mf_keycache.c 161 KB
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/* Copyright (C) 2000 MySQL AB, 2008-2009 Sun Microsystems, Inc
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   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
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   the Free Software Foundation; version 2 of the License.
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   This program is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
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/**
  @file
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  These functions handle keyblock cacheing for ISAM and MyISAM tables.

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  One cache can handle many files.
  It must contain buffers of the same blocksize.
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  init_key_cache() should be used to init cache handler.
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  The free list (free_block_list) is a stack like structure.
  When a block is freed by free_block(), it is pushed onto the stack.
  When a new block is required it is first tried to pop one from the stack.
  If the stack is empty, it is tried to get a never-used block from the pool.
  If this is empty too, then a block is taken from the LRU ring, flushing it
  to disk, if neccessary. This is handled in find_key_block().
  With the new free list, the blocks can have three temperatures:
  hot, warm and cold (which is free). This is remembered in the block header
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  by the enum BLOCK_TEMPERATURE temperature variable. Remembering the
  temperature is neccessary to correctly count the number of warm blocks,
  which is required to decide when blocks are allowed to become hot. Whenever
  a block is inserted to another (sub-)chain, we take the old and new
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  temperature into account to decide if we got one more or less warm block.
  blocks_unused is the sum of never used blocks in the pool and of currently
  free blocks. blocks_used is the number of blocks fetched from the pool and
  as such gives the maximum number of in-use blocks at any time.
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*/
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/*
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  Key Cache Locking
  =================

  All key cache locking is done with a single mutex per key cache:
  keycache->cache_lock. This mutex is locked almost all the time
  when executing code in this file (mf_keycache.c).
  However it is released for I/O and some copy operations.

  The cache_lock is also released when waiting for some event. Waiting
  and signalling is done via condition variables. In most cases the
  thread waits on its thread->suspend condition variable. Every thread
  has a my_thread_var structure, which contains this variable and a
  '*next' and '**prev' pointer. These pointers are used to insert the
  thread into a wait queue.

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  A thread can wait for one block and thus be in one wait queue at a
  time only.
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  Before starting to wait on its condition variable with
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  mysql_cond_wait(), the thread enters itself to a specific wait queue
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  with link_into_queue() (double linked with '*next' + '**prev') or
  wait_on_queue() (single linked with '*next').

  Another thread, when releasing a resource, looks up the waiting thread
  in the related wait queue. It sends a signal with
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  mysql_cond_signal() to the waiting thread.
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  NOTE: Depending on the particular wait situation, either the sending
  thread removes the waiting thread from the wait queue with
  unlink_from_queue() or release_whole_queue() respectively, or the waiting
  thread removes itself.

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  There is one exception from this locking scheme when one thread wants
  to reuse a block for some other address. This works by first marking
  the block reserved (status= BLOCK_IN_SWITCH) and then waiting for all
  threads that are reading the block to finish. Each block has a
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  reference to a condition variable (condvar). It holds a reference to
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  the thread->suspend condition variable for the waiting thread (if such
  a thread exists). When that thread is signaled, the reference is
  cleared. The number of readers of a block is registered in
  block->hash_link->requests. See wait_for_readers() / remove_reader()
  for details. This is similar to the above, but it clearly means that
  only one thread can wait for a particular block. There is no queue in
  this case. Strangely enough block->convar is used for waiting for the
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  assigned hash_link only. More precisely it is used to wait for all
  requests to be unregistered from the assigned hash_link.

  The resize_queue serves two purposes:
  1. Threads that want to do a resize wait there if in_resize is set.
     This is not used in the server. The server refuses a second resize
     request if one is already active. keycache->in_init is used for the
     synchronization. See set_var.cc.
  2. Threads that want to access blocks during resize wait here during
     the re-initialization phase.
  When the resize is done, all threads on the queue are signalled.
  Hypothetical resizers can compete for resizing, and read/write
  requests will restart to request blocks from the freshly resized
  cache. If the cache has been resized too small, it is disabled and
  'can_be_used' is false. In this case read/write requests bypass the
  cache. Since they increment and decrement 'cnt_for_resize_op', the
  next resizer can wait on the queue 'waiting_for_resize_cnt' until all
  I/O finished.
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*/
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#include "mysys_priv.h"
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#include "mysys_err.h"
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#include <keycache.h>
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#include "my_static.h"
#include <m_string.h>
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#include <my_bit.h>
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#include <errno.h>
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#include <stdarg.h>
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#include "probes_mysql.h"
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/*
  Some compilation flags have been added specifically for this module
  to control the following:
  - not to let a thread to yield the control when reading directly
    from key cache, which might improve performance in many cases;
    to enable this add:
    #define SERIALIZED_READ_FROM_CACHE
  - to set an upper bound for number of threads simultaneously
    using the key cache; this setting helps to determine an optimal
    size for hash table and improve performance when the number of
    blocks in the key cache much less than the number of threads
    accessing it;
    to set this number equal to <N> add
      #define MAX_THREADS <N>
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  - to substitute calls of mysql_cond_wait for calls of
    mysql_cond_timedwait (wait with timeout set up);
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    this setting should be used only when you want to trap a deadlock
    situation, which theoretically should not happen;
    to set timeout equal to <T> seconds add
      #define KEYCACHE_TIMEOUT <T>
  - to enable the module traps and to send debug information from
    key cache module to a special debug log add:
      #define KEYCACHE_DEBUG
    the name of this debug log file <LOG NAME> can be set through:
      #define KEYCACHE_DEBUG_LOG  <LOG NAME>
    if the name is not defined, it's set by default;
    if the KEYCACHE_DEBUG flag is not set up and we are in a debug
    mode, i.e. when ! defined(DBUG_OFF), the debug information from the
    module is sent to the regular debug log.

  Example of the settings:
    #define SERIALIZED_READ_FROM_CACHE
    #define MAX_THREADS   100
    #define KEYCACHE_TIMEOUT  1
    #define KEYCACHE_DEBUG
    #define KEYCACHE_DEBUG_LOG  "my_key_cache_debug.log"
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*/
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#define STRUCT_PTR(TYPE, MEMBER, a)                                           \
          (TYPE *) ((char *) (a) - offsetof(TYPE, MEMBER))

/* types of condition variables */
#define  COND_FOR_REQUESTED 0
#define  COND_FOR_SAVED     1
#define  COND_FOR_READERS   2

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typedef mysql_cond_t KEYCACHE_CONDVAR;
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/* descriptor of the page in the key cache block buffer */
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struct st_keycache_page
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{
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  int file;               /* file to which the page belongs to  */
  my_off_t filepos;       /* position of the page in the file   */
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};
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/* element in the chain of a hash table bucket */
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struct st_hash_link
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{
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  struct st_hash_link *next, **prev; /* to connect links in the same bucket  */
  struct st_block_link *block;       /* reference to the block for the page: */
  File file;                         /* from such a file                     */
  my_off_t diskpos;                  /* with such an offset                  */
  uint requests;                     /* number of requests for the page      */
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};
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/* simple states of a block */
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#define BLOCK_ERROR           1 /* an error occured when performing file i/o */
#define BLOCK_READ            2 /* file block is in the block buffer         */
#define BLOCK_IN_SWITCH       4 /* block is preparing to read new page       */
#define BLOCK_REASSIGNED      8 /* blk does not accept requests for old page */
#define BLOCK_IN_FLUSH       16 /* block is selected for flush               */
#define BLOCK_CHANGED        32 /* block buffer contains a dirty page        */
#define BLOCK_IN_USE         64 /* block is not free                         */
#define BLOCK_IN_EVICTION   128 /* block is selected for eviction            */
#define BLOCK_IN_FLUSHWRITE 256 /* block is in write to file                 */
#define BLOCK_FOR_UPDATE    512 /* block is selected for buffer modification */
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/* page status, returned by find_key_block */
#define PAGE_READ               0
#define PAGE_TO_BE_READ         1
#define PAGE_WAIT_TO_BE_READ    2

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/* block temperature determines in which (sub-)chain the block currently is */
enum BLOCK_TEMPERATURE { BLOCK_COLD /*free*/ , BLOCK_WARM , BLOCK_HOT };

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/* key cache block */
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struct st_block_link
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{
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  struct st_block_link
    *next_used, **prev_used;   /* to connect links in the LRU chain (ring)   */
  struct st_block_link
    *next_changed, **prev_changed; /* for lists of file dirty/clean blocks   */
  struct st_hash_link *hash_link; /* backward ptr to referring hash_link     */
  KEYCACHE_WQUEUE wqueue[2]; /* queues on waiting requests for new/old pages */
  uint requests;          /* number of requests for the block                */
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  uchar *buffer;           /* buffer for the block page                       */
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  uint offset;            /* beginning of modified data in the buffer        */
  uint length;            /* end of data in the buffer                       */
  uint status;            /* state of the block                              */
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  enum BLOCK_TEMPERATURE temperature; /* block temperature: cold, warm, hot */
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  uint hits_left;         /* number of hits left until promotion             */
  ulonglong last_hit_time; /* timestamp of the last hit                      */
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  KEYCACHE_CONDVAR *condvar; /* condition variable for 'no readers' event    */
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};
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KEY_CACHE dflt_key_cache_var;
KEY_CACHE *dflt_key_cache= &dflt_key_cache_var;

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#define FLUSH_CACHE         2000            /* sort this many blocks at once */

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static int flush_all_key_blocks(KEY_CACHE *keycache);
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#ifdef THREAD
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static void wait_on_queue(KEYCACHE_WQUEUE *wqueue,
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                          mysql_mutex_t *mutex);
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static void release_whole_queue(KEYCACHE_WQUEUE *wqueue);
#else
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#define wait_on_queue(wqueue, mutex)    do {} while (0)
#define release_whole_queue(wqueue)     do {} while (0)
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#endif
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static void free_block(KEY_CACHE *keycache, BLOCK_LINK *block);
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#if !defined(DBUG_OFF)
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static void test_key_cache(KEY_CACHE *keycache,
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                           const char *where, my_bool lock);
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#endif
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#define KEYCACHE_HASH(f, pos)                                                 \
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(((ulong) ((pos) / keycache->key_cache_block_size) +                          \
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                                     (ulong) (f)) & (keycache->hash_entries-1))
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#define FILE_HASH(f)                 ((uint) (f) & (CHANGED_BLOCKS_HASH-1))
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#define DEFAULT_KEYCACHE_DEBUG_LOG  "keycache_debug.log"
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#if defined(KEYCACHE_DEBUG) && ! defined(KEYCACHE_DEBUG_LOG)
#define KEYCACHE_DEBUG_LOG  DEFAULT_KEYCACHE_DEBUG_LOG
#endif
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#if defined(KEYCACHE_DEBUG_LOG)
static FILE *keycache_debug_log=NULL;
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static void keycache_debug_print(const char *fmt,...);
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#define KEYCACHE_DEBUG_OPEN                                                   \
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          if (!keycache_debug_log)                                            \
          {                                                                   \
            keycache_debug_log= fopen(KEYCACHE_DEBUG_LOG, "w");               \
            (void) setvbuf(keycache_debug_log, NULL, _IOLBF, BUFSIZ);         \
          }
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#define KEYCACHE_DEBUG_CLOSE                                                  \
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          if (keycache_debug_log)                                             \
          {                                                                   \
            fclose(keycache_debug_log);                                       \
            keycache_debug_log= 0;                                            \
          }
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#else
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#define KEYCACHE_DEBUG_OPEN
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#define KEYCACHE_DEBUG_CLOSE
#endif /* defined(KEYCACHE_DEBUG_LOG) */

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#if defined(KEYCACHE_DEBUG_LOG) && defined(KEYCACHE_DEBUG)
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#define KEYCACHE_DBUG_PRINT(l, m)                                             \
            { if (keycache_debug_log) fprintf(keycache_debug_log, "%s: ", l); \
              keycache_debug_print m; }

#define KEYCACHE_DBUG_ASSERT(a)                                               \
            { if (! (a) && keycache_debug_log) fclose(keycache_debug_log);    \
              assert(a); }
#else
#define KEYCACHE_DBUG_PRINT(l, m)  DBUG_PRINT(l, m)
#define KEYCACHE_DBUG_ASSERT(a)    DBUG_ASSERT(a)
#endif /* defined(KEYCACHE_DEBUG_LOG) && defined(KEYCACHE_DEBUG) */

#if defined(KEYCACHE_DEBUG) || !defined(DBUG_OFF)
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#ifdef THREAD
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static long keycache_thread_id;
#define KEYCACHE_THREAD_TRACE(l)                                              \
             KEYCACHE_DBUG_PRINT(l,("|thread %ld",keycache_thread_id))

#define KEYCACHE_THREAD_TRACE_BEGIN(l)                                        \
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            { struct st_my_thread_var *thread_var= my_thread_var;             \
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              keycache_thread_id= thread_var->id;                             \
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              KEYCACHE_DBUG_PRINT(l,("[thread %ld",keycache_thread_id)) }

#define KEYCACHE_THREAD_TRACE_END(l)                                          \
            KEYCACHE_DBUG_PRINT(l,("]thread %ld",keycache_thread_id))
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#else /* THREAD */
#define KEYCACHE_THREAD_TRACE(l)        KEYCACHE_DBUG_PRINT(l,(""))
#define KEYCACHE_THREAD_TRACE_BEGIN(l)  KEYCACHE_DBUG_PRINT(l,(""))
#define KEYCACHE_THREAD_TRACE_END(l)    KEYCACHE_DBUG_PRINT(l,(""))
#endif /* THREAD */
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#else
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#define KEYCACHE_THREAD_TRACE_BEGIN(l)
#define KEYCACHE_THREAD_TRACE_END(l)
#define KEYCACHE_THREAD_TRACE(l)
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#endif /* defined(KEYCACHE_DEBUG) || !defined(DBUG_OFF) */

#define BLOCK_NUMBER(b)                                                       \
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  ((uint) (((char*)(b)-(char *) keycache->block_root)/sizeof(BLOCK_LINK)))
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#define HASH_LINK_NUMBER(h)                                                   \
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  ((uint) (((char*)(h)-(char *) keycache->hash_link_root)/sizeof(HASH_LINK)))
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#if (defined(KEYCACHE_TIMEOUT) && !defined(__WIN__)) || defined(KEYCACHE_DEBUG)
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static int keycache_pthread_cond_wait(mysql_cond_t *cond,
                                      mysql_mutex_t *mutex);
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#else
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#define keycache_pthread_cond_wait(C, M) mysql_cond_wait(C, M)
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#endif

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#if defined(KEYCACHE_DEBUG)
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static int keycache_pthread_mutex_lock(mysql_mutex_t *mutex);
static void keycache_pthread_mutex_unlock(mysql_mutex_t *mutex);
static int keycache_pthread_cond_signal(mysql_cond_t *cond);
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#else
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#define keycache_pthread_mutex_lock(M) mysql_mutex_lock(M)
#define keycache_pthread_mutex_unlock(M) mysql_mutex_unlock(M)
#define keycache_pthread_cond_signal(C) mysql_cond_signal(C)
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#endif /* defined(KEYCACHE_DEBUG) */

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#if !defined(DBUG_OFF)
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#if defined(inline)
#undef inline
#endif
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#define inline  /* disabled inline for easier debugging */
static int fail_block(BLOCK_LINK *block);
static int fail_hlink(HASH_LINK *hlink);
static int cache_empty(KEY_CACHE *keycache);
#endif

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static inline uint next_power(uint value)
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{
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  return (uint) my_round_up_to_next_power((uint32) value) << 1;
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}
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/*
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  Initialize a key cache

  SYNOPSIS
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    init_key_cache()
    keycache			pointer to a key cache data structure
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    key_cache_block_size	size of blocks to keep cached data
    use_mem                 	total memory to use for the key cache
    division_limit		division limit (may be zero)
    age_threshold		age threshold (may be zero)
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  RETURN VALUE
    number of blocks in the key cache, if successful,
    0 - otherwise.

  NOTES.
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    if keycache->key_cache_inited != 0 we assume that the key cache
    is already initialized.  This is for now used by myisamchk, but shouldn't
    be something that a program should rely on!

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    It's assumed that no two threads call this function simultaneously
    referring to the same key cache handle.
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*/
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int init_key_cache(KEY_CACHE *keycache, uint key_cache_block_size,
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                   size_t use_mem, uint division_limit,
                   uint age_threshold)
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{
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  ulong blocks, hash_links;
  size_t length;
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  int error;
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  DBUG_ENTER("init_key_cache");
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  DBUG_ASSERT(key_cache_block_size >= 512);
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  KEYCACHE_DEBUG_OPEN;
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  if (keycache->key_cache_inited && keycache->disk_blocks > 0)
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  {
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    DBUG_PRINT("warning",("key cache already in use"));
    DBUG_RETURN(0);
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  }
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  keycache->global_cache_w_requests= keycache->global_cache_r_requests= 0;
  keycache->global_cache_read= keycache->global_cache_write= 0;
  keycache->disk_blocks= -1;
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  if (! keycache->key_cache_inited)
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  {
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    keycache->key_cache_inited= 1;
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    /*
      Initialize these variables once only.
      Their value must survive re-initialization during resizing.
    */
    keycache->in_resize= 0;
    keycache->resize_in_flush= 0;
    keycache->cnt_for_resize_op= 0;
    keycache->waiting_for_resize_cnt.last_thread= NULL;
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    keycache->in_init= 0;
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    mysql_mutex_init(key_KEY_CACHE_cache_lock,
                     &keycache->cache_lock, MY_MUTEX_INIT_FAST);
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    keycache->resize_queue.last_thread= NULL;
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  }
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  keycache->key_cache_mem_size= use_mem;
  keycache->key_cache_block_size= key_cache_block_size;
  DBUG_PRINT("info", ("key_cache_block_size: %u",
		      key_cache_block_size));
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  blocks= (ulong) (use_mem / (sizeof(BLOCK_LINK) + 2 * sizeof(HASH_LINK) +
                              sizeof(HASH_LINK*) * 5/4 + key_cache_block_size));
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  /* It doesn't make sense to have too few blocks (less than 8) */
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  if (blocks >= 8)
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  {
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    for ( ; ; )
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    {
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      /* Set my_hash_entries to the next bigger 2 power */
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      if ((keycache->hash_entries= next_power(blocks)) < blocks * 5/4)
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        keycache->hash_entries<<= 1;
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      hash_links= 2 * blocks;
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#if defined(MAX_THREADS)
      if (hash_links < MAX_THREADS + blocks - 1)
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        hash_links= MAX_THREADS + blocks - 1;
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#endif
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      while ((length= (ALIGN_SIZE(blocks * sizeof(BLOCK_LINK)) +
		       ALIGN_SIZE(hash_links * sizeof(HASH_LINK)) +
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		       ALIGN_SIZE(sizeof(HASH_LINK*) *
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                                  keycache->hash_entries))) +
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	     ((size_t) blocks * keycache->key_cache_block_size) > use_mem)
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        blocks--;
      /* Allocate memory for cache page buffers */
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      if ((keycache->block_mem=
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	   my_large_malloc((size_t) blocks * keycache->key_cache_block_size,
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			  MYF(0))))
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      {
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        /*
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	  Allocate memory for blocks, hash_links and hash entries;
	  For each block 2 hash links are allocated
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        */
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        if ((keycache->block_root= (BLOCK_LINK*) my_malloc(length,
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                                                           MYF(0))))
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          break;
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        my_large_free(keycache->block_mem);
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        keycache->block_mem= 0;
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      }
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      if (blocks < 8)
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      {
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        my_errno= ENOMEM;
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        my_error(EE_OUTOFMEMORY, MYF(0), blocks * keycache->key_cache_block_size);
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        goto err;
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      }
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      blocks= blocks / 4*3;
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    }
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    keycache->blocks_unused= blocks;
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    keycache->disk_blocks= (int) blocks;
    keycache->hash_links= hash_links;
    keycache->hash_root= (HASH_LINK**) ((char*) keycache->block_root +
				        ALIGN_SIZE(blocks*sizeof(BLOCK_LINK)));
    keycache->hash_link_root= (HASH_LINK*) ((char*) keycache->hash_root +
				            ALIGN_SIZE((sizeof(HASH_LINK*) *
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							keycache->hash_entries)));
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    bzero((uchar*) keycache->block_root,
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	  keycache->disk_blocks * sizeof(BLOCK_LINK));
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    bzero((uchar*) keycache->hash_root,
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          keycache->hash_entries * sizeof(HASH_LINK*));
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    bzero((uchar*) keycache->hash_link_root,
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	  keycache->hash_links * sizeof(HASH_LINK));
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    keycache->hash_links_used= 0;
    keycache->free_hash_list= NULL;
    keycache->blocks_used= keycache->blocks_changed= 0;
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    keycache->global_blocks_changed= 0;
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    keycache->blocks_available=0;		/* For debugging */

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    /* The LRU chain is empty after initialization */
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    keycache->used_last= NULL;
    keycache->used_ins= NULL;
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    keycache->free_block_list= NULL;
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    keycache->keycache_time= 0;
    keycache->warm_blocks= 0;
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    keycache->min_warm_blocks= (division_limit ?
				blocks * division_limit / 100 + 1 :
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				blocks);
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    keycache->age_threshold= (age_threshold ?
			      blocks * age_threshold / 100 :
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			      blocks);
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    keycache->can_be_used= 1;

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    keycache->waiting_for_hash_link.last_thread= NULL;
    keycache->waiting_for_block.last_thread= NULL;
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    DBUG_PRINT("exit",
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	       ("disk_blocks: %d  block_root: 0x%lx  hash_entries: %d\
 hash_root: 0x%lx  hash_links: %d  hash_link_root: 0x%lx",
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		keycache->disk_blocks,  (long) keycache->block_root,
		keycache->hash_entries, (long) keycache->hash_root,
		keycache->hash_links,   (long) keycache->hash_link_root));
504
    bzero((uchar*) keycache->changed_blocks,
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	  sizeof(keycache->changed_blocks[0]) * CHANGED_BLOCKS_HASH);
506
    bzero((uchar*) keycache->file_blocks,
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	  sizeof(keycache->file_blocks[0]) * CHANGED_BLOCKS_HASH);
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  }
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  else
  {
    /* key_buffer_size is specified too small. Disable the cache. */
    keycache->can_be_used= 0;
  }
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  keycache->blocks= keycache->disk_blocks > 0 ? keycache->disk_blocks : 0;
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  DBUG_RETURN((int) keycache->disk_blocks);
517

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err:
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  error= my_errno;
520
  keycache->disk_blocks= 0;
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  keycache->blocks=  0;
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  if (keycache->block_mem)
523
  {
524
    my_large_free((uchar*) keycache->block_mem);
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    keycache->block_mem= NULL;
  }
  if (keycache->block_root)
  {
529
    my_free(keycache->block_root);
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    keycache->block_root= NULL;
  }
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  my_errno= error;
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  keycache->can_be_used= 0;
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  DBUG_RETURN(0);
535
}
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/*
539 540 541 542
  Resize a key cache

  SYNOPSIS
    resize_key_cache()
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    keycache     	        pointer to a key cache data structure
    key_cache_block_size        size of blocks to keep cached data
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    use_mem			total memory to use for the new key cache
    division_limit		new division limit (if not zero)
    age_threshold		new age threshold (if not zero)
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  RETURN VALUE
    number of blocks in the key cache, if successful,
    0 - otherwise.

  NOTES.
    The function first compares the memory size and the block size parameters
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    with the key cache values.

    If they differ the function free the the memory allocated for the
    old key cache blocks by calling the end_key_cache function and
    then rebuilds the key cache with new blocks by calling
    init_key_cache.
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    The function starts the operation only when all other threads
    performing operations with the key cache let her to proceed
    (when cnt_for_resize=0).
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*/
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int resize_key_cache(KEY_CACHE *keycache, uint key_cache_block_size,
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                     size_t use_mem, uint division_limit,
                     uint age_threshold)
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{
571
  int blocks;
572
  DBUG_ENTER("resize_key_cache");
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  if (!keycache->key_cache_inited)
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    DBUG_RETURN(keycache->disk_blocks);
576

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  if(key_cache_block_size == keycache->key_cache_block_size &&
     use_mem == keycache->key_cache_mem_size)
  {
    change_key_cache_param(keycache, division_limit, age_threshold);
    DBUG_RETURN(keycache->disk_blocks);
582
  }
583

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  keycache_pthread_mutex_lock(&keycache->cache_lock);
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586
#ifdef THREAD
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  /*
    We may need to wait for another thread which is doing a resize
    already. This cannot happen in the MySQL server though. It allows
    one resizer only. In set_var.cc keycache->in_init is used to block
    multiple attempts.
  */
  while (keycache->in_resize)
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  {
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    /* purecov: begin inspected */
    wait_on_queue(&keycache->resize_queue, &keycache->cache_lock);
    /* purecov: end */
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  }
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#endif
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  /*
    Mark the operation in progress. This blocks other threads from doing
    a resize in parallel. It prohibits new blocks to enter the cache.
    Read/write requests can bypass the cache during the flush phase.
  */
  keycache->in_resize= 1;

  /* Need to flush only if keycache is enabled. */
  if (keycache->can_be_used)
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  {
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    /* Start the flush phase. */
    keycache->resize_in_flush= 1;

    if (flush_all_key_blocks(keycache))
    {
      /* TODO: if this happens, we should write a warning in the log file ! */
      keycache->resize_in_flush= 0;
      blocks= 0;
      keycache->can_be_used= 0;
      goto finish;
    }
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    DBUG_ASSERT(cache_empty(keycache));
623 624

    /* End the flush phase. */
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    keycache->resize_in_flush= 0;
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  }
627

628
#ifdef THREAD
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  /*
    Some direct read/write operations (bypassing the cache) may still be
    unfinished. Wait until they are done. If the key cache can be used,
    direct I/O is done in increments of key_cache_block_size. That is,
    every block is checked if it is in the cache. We need to wait for
    pending I/O before re-initializing the cache, because we may change
    the block size. Otherwise they could check for blocks at file
    positions where the new block division has none. We do also want to
    wait for I/O done when (if) the cache was disabled. It must not
    run in parallel with normal cache operation.
  */
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  while (keycache->cnt_for_resize_op)
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    wait_on_queue(&keycache->waiting_for_resize_cnt, &keycache->cache_lock);
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#else
  KEYCACHE_DBUG_ASSERT(keycache->cnt_for_resize_op == 0);
#endif
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646 647 648 649 650 651
  /*
    Free old cache structures, allocate new structures, and initialize
    them. Note that the cache_lock mutex and the resize_queue are left
    untouched. We do not lose the cache_lock and will release it only at
    the end of this function.
  */
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  end_key_cache(keycache, 0);			/* Don't free mutex */
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  /* The following will work even if use_mem is 0 */
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  blocks= init_key_cache(keycache, key_cache_block_size, use_mem,
			 division_limit, age_threshold);
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finish:
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  /*
    Mark the resize finished. This allows other threads to start a
    resize or to request new cache blocks.
  */
  keycache->in_resize= 0;

  /* Signal waiting threads. */
  release_whole_queue(&keycache->resize_queue);

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  keycache_pthread_mutex_unlock(&keycache->cache_lock);
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  DBUG_RETURN(blocks);
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}


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/*
  Increment counter blocking resize key cache operation
*/
static inline void inc_counter_for_resize_op(KEY_CACHE *keycache)
{
  keycache->cnt_for_resize_op++;
}


/*
  Decrement counter blocking resize key cache operation;
  Signal the operation to proceed when counter becomes equal zero
*/
static inline void dec_counter_for_resize_op(KEY_CACHE *keycache)
{
687 688
  if (!--keycache->cnt_for_resize_op)
    release_whole_queue(&keycache->waiting_for_resize_cnt);
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}

691
/*
692
  Change the key cache parameters
693 694 695

  SYNOPSIS
    change_key_cache_param()
696
    keycache			pointer to a key cache data structure
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    division_limit		new division limit (if not zero)
    age_threshold		new age threshold (if not zero)
699 700 701 702 703 704 705

  RETURN VALUE
    none

  NOTES.
    Presently the function resets the key cache parameters
    concerning midpoint insertion strategy - division_limit and
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    age_threshold.
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*/

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void change_key_cache_param(KEY_CACHE *keycache, uint division_limit,
			    uint age_threshold)
711
{
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  DBUG_ENTER("change_key_cache_param");
713

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  keycache_pthread_mutex_lock(&keycache->cache_lock);
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  if (division_limit)
    keycache->min_warm_blocks= (keycache->disk_blocks *
				division_limit / 100 + 1);
  if (age_threshold)
    keycache->age_threshold=   (keycache->disk_blocks *
				age_threshold / 100);
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  keycache_pthread_mutex_unlock(&keycache->cache_lock);
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  DBUG_VOID_RETURN;
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}


726
/*
727
  Remove key_cache from memory
728 729 730

  SYNOPSIS
    end_key_cache()
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    keycache		key cache handle
    cleanup		Complete free (Free also mutex for key cache)
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  RETURN VALUE
    none
736
*/
737

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void end_key_cache(KEY_CACHE *keycache, my_bool cleanup)
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{
  DBUG_ENTER("end_key_cache");
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  DBUG_PRINT("enter", ("key_cache: 0x%lx", (long) keycache));
742

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  if (!keycache->key_cache_inited)
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    DBUG_VOID_RETURN;
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  if (keycache->disk_blocks > 0)
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  {
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    if (keycache->block_mem)
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    {
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      my_large_free((uchar*) keycache->block_mem);
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      keycache->block_mem= NULL;
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      my_free(keycache->block_root);
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      keycache->block_root= NULL;
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    }
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    keycache->disk_blocks= -1;
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    /* Reset blocks_changed to be safe if flush_all_key_blocks is called */
    keycache->blocks_changed= 0;
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  }
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  DBUG_PRINT("status", ("used: %lu  changed: %lu  w_requests: %lu  "
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                        "writes: %lu  r_requests: %lu  reads: %lu",
                        keycache->blocks_used, keycache->global_blocks_changed,
                        (ulong) keycache->global_cache_w_requests,
                        (ulong) keycache->global_cache_write,
                        (ulong) keycache->global_cache_r_requests,
                        (ulong) keycache->global_cache_read));
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768 769 770 771 772 773 774
  /*
    Reset these values to be able to detect a disabled key cache.
    See Bug#44068 (RESTORE can disable the MyISAM Key Cache).
  */
  keycache->blocks_used= 0;
  keycache->blocks_unused= 0;

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  if (cleanup)
  {
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    mysql_mutex_destroy(&keycache->cache_lock);
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    keycache->key_cache_inited= keycache->can_be_used= 0;
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    KEYCACHE_DEBUG_CLOSE;
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  }
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  DBUG_VOID_RETURN;
} /* end_key_cache */


785
#ifdef THREAD
786

787
/*
788 789 790 791
  Link a thread into double-linked queue of waiting threads.

  SYNOPSIS
    link_into_queue()
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      wqueue              pointer to the queue structure
      thread              pointer to the thread to be added to the queue
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  RETURN VALUE
    none

  NOTES.
    Queue is represented by a circular list of the thread structures
    The list is double-linked of the type (**prev,*next), accessed by
    a pointer to the last element.
802
*/
803

804
static void link_into_queue(KEYCACHE_WQUEUE *wqueue,
805
                                   struct st_my_thread_var *thread)
806
{
807
  struct st_my_thread_var *last;
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  DBUG_ASSERT(!thread->next && !thread->prev);
810
  if (! (last= wqueue->last_thread))
811 812
  {
    /* Queue is empty */
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    thread->next= thread;
    thread->prev= &thread->next;
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  }
  else
817
  {
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    thread->prev= last->next->prev;
    last->next->prev= &thread->next;
    thread->next= last->next;
    last->next= thread;
822
  }
823
  wqueue->last_thread= thread;
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}

/*
827
  Unlink a thread from double-linked queue of waiting threads
828 829 830

  SYNOPSIS
    unlink_from_queue()
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      wqueue              pointer to the queue structure
      thread              pointer to the thread to be removed from the queue
833 834 835 836 837 838

  RETURN VALUE
    none

  NOTES.
    See NOTES for link_into_queue
839
*/
840

841
static void unlink_from_queue(KEYCACHE_WQUEUE *wqueue,
842
                                     struct st_my_thread_var *thread)
843
{
844
  KEYCACHE_DBUG_PRINT("unlink_from_queue", ("thread %ld", thread->id));
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  DBUG_ASSERT(thread->next && thread->prev);
846 847
  if (thread->next == thread)
    /* The queue contains only one member */
848
    wqueue->last_thread= NULL;
849
  else
850
  {
851
    thread->next->prev= thread->prev;
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    *thread->prev=thread->next;
    if (wqueue->last_thread == thread)
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      wqueue->last_thread= STRUCT_PTR(struct st_my_thread_var, next,
                                      thread->prev);
856
  }
857
  thread->next= NULL;
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#if !defined(DBUG_OFF)
  /*
    This makes it easier to see it's not in a chain during debugging.
    And some DBUG_ASSERT() rely on it.
  */
  thread->prev= NULL;
#endif
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}


/*
869
  Add a thread to single-linked queue of waiting threads
870 871

  SYNOPSIS
872 873 874
    wait_on_queue()
      wqueue            Pointer to the queue structure.
      mutex             Cache_lock to acquire after awake.
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  RETURN VALUE
    none

  NOTES.
    Queue is represented by a circular list of the thread structures
    The list is single-linked of the type (*next), accessed by a pointer
    to the last element.
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    The function protects against stray signals by verifying that the
    current thread is unlinked from the queue when awaking. However,
    since several threads can wait for the same event, it might be
    necessary for the caller of the function to check again if the
    condition for awake is indeed matched.
889
*/
890

891
static void wait_on_queue(KEYCACHE_WQUEUE *wqueue,
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                          mysql_mutex_t *mutex)
893
{
894
  struct st_my_thread_var *last;
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  struct st_my_thread_var *thread= my_thread_var;

  /* Add to queue. */
  DBUG_ASSERT(!thread->next);
  DBUG_ASSERT(!thread->prev); /* Not required, but must be true anyway. */
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  if (! (last= wqueue->last_thread))
    thread->next= thread;
902
  else
903
  {
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    thread->next= last->next;
    last->next= thread;
906
  }
907
  wqueue->last_thread= thread;
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  /*
    Wait until thread is removed from queue by the signalling thread.
    The loop protects against stray signals.
  */
  do
  {
    KEYCACHE_DBUG_PRINT("wait", ("suspend thread %ld", thread->id));
    keycache_pthread_cond_wait(&thread->suspend, mutex);
  }
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  while (thread->next);
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}


/*
923
  Remove all threads from queue signaling them to proceed
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  SYNOPSIS
926 927
    release_whole_queue()
      wqueue            pointer to the queue structure
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  RETURN VALUE
    none

  NOTES.
933
    See notes for wait_on_queue().
934
    When removed from the queue each thread is signaled via condition
935
    variable thread->suspend.
936
*/
937

938
static void release_whole_queue(KEYCACHE_WQUEUE *wqueue)
939
{
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  struct st_my_thread_var *last;
  struct st_my_thread_var *next;
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  struct st_my_thread_var *thread;
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  /* Queue may be empty. */
  if (!(last= wqueue->last_thread))
    return;

  next= last->next;
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  do
  {
    thread=next;
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    KEYCACHE_DBUG_PRINT("release_whole_queue: signal",
                        ("thread %ld", thread->id));
    /* Signal the thread. */
955
    keycache_pthread_cond_signal(&thread->suspend);
956
    /* Take thread from queue. */
957
    next=thread->next;
958
    thread->next= NULL;
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  }
  while (thread != last);
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  /* Now queue is definitely empty. */
963
  wqueue->last_thread= NULL;
964
}
965 966

#endif /* THREAD */
967 968 969


/*
970
  Unlink a block from the chain of dirty/clean blocks
971
*/
972

973
static inline void unlink_changed(BLOCK_LINK *block)
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{
975
  DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
976
  if (block->next_changed)
977 978
    block->next_changed->prev_changed= block->prev_changed;
  *block->prev_changed= block->next_changed;
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#if !defined(DBUG_OFF)
  /*
    This makes it easier to see it's not in a chain during debugging.
    And some DBUG_ASSERT() rely on it.
  */
  block->next_changed= NULL;
  block->prev_changed= NULL;
#endif
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}


991
/*
992
  Link a block into the chain of dirty/clean blocks
993
*/
994

995
static inline void link_changed(BLOCK_LINK *block, BLOCK_LINK **phead)
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{
997 998
  DBUG_ASSERT(!block->next_changed);
  DBUG_ASSERT(!block->prev_changed);
999 1000
  block->prev_changed= phead;
  if ((block->next_changed= *phead))
1001
    (*phead)->prev_changed= &block->next_changed;
1002
  *phead= block;
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}

1005 1006

/*
1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028
  Link a block in a chain of clean blocks of a file.

  SYNOPSIS
    link_to_file_list()
      keycache		Key cache handle
      block             Block to relink
      file              File to be linked to
      unlink            If to unlink first

  DESCRIPTION
    Unlink a block from whichever chain it is linked in, if it's
    asked for, and link it to the chain of clean blocks of the
    specified file.

  NOTE
    Please do never set/clear BLOCK_CHANGED outside of
    link_to_file_list() or link_to_changed_list().
    You would risk to damage correct counting of changed blocks
    and to find blocks in the wrong hash.

  RETURN
    void
1029
*/
1030

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static void link_to_file_list(KEY_CACHE *keycache,
1032 1033
                              BLOCK_LINK *block, int file,
                              my_bool unlink_block)
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{
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  DBUG_ASSERT(block->status & BLOCK_IN_USE);
  DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
  DBUG_ASSERT(block->hash_link->file == file);
1038
  if (unlink_block)
1039
    unlink_changed(block);
1040
  link_changed(block, &keycache->file_blocks[FILE_HASH(file)]);
1041 1042
  if (block->status & BLOCK_CHANGED)
  {
1043
    block->status&= ~BLOCK_CHANGED;
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    keycache->blocks_changed--;
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    keycache->global_blocks_changed--;
1046
  }
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}

1049

1050
/*
1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069
  Re-link a block from the clean chain to the dirty chain of a file.

  SYNOPSIS
    link_to_changed_list()
      keycache		key cache handle
      block             block to relink

  DESCRIPTION
    Unlink a block from the chain of clean blocks of a file
    and link it to the chain of dirty blocks of the same file.

  NOTE
    Please do never set/clear BLOCK_CHANGED outside of
    link_to_file_list() or link_to_changed_list().
    You would risk to damage correct counting of changed blocks
    and to find blocks in the wrong hash.

  RETURN
    void
1070
*/
1071

1072 1073
static void link_to_changed_list(KEY_CACHE *keycache,
                                 BLOCK_LINK *block)
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{
1075 1076 1077 1078
  DBUG_ASSERT(block->status & BLOCK_IN_USE);
  DBUG_ASSERT(!(block->status & BLOCK_CHANGED));
  DBUG_ASSERT(block->hash_link && block->hash_link->block == block);

1079
  unlink_changed(block);
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  link_changed(block,
               &keycache->changed_blocks[FILE_HASH(block->hash_link->file)]);
1082
  block->status|=BLOCK_CHANGED;
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  keycache->blocks_changed++;
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  keycache->global_blocks_changed++;
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}


1088
/*
1089 1090 1091 1092 1093
  Link a block to the LRU chain at the beginning or at the end of
  one of two parts.

  SYNOPSIS
    link_block()
1094
      keycache            pointer to a key cache data structure
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      block               pointer to the block to link to the LRU chain
      hot                 <-> to link the block into the hot subchain
      at_end              <-> to link the block at the end of the subchain

  RETURN VALUE
    none

  NOTES.
1103
    The LRU ring is represented by a circular list of block structures.
1104
    The list is double-linked of the type (**prev,*next) type.
1105
    The LRU ring is divided into two parts - hot and warm.
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    There are two pointers to access the last blocks of these two
1107
    parts. The beginning of the warm part follows right after the
1108
    end of the hot part.
1109
    Only blocks of the warm part can be used for eviction.
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    The first block from the beginning of this subchain is always
    taken for eviction (keycache->last_used->next)

    LRU chain:       +------+   H O T    +------+
                +----| end  |----...<----| beg  |----+
                |    +------+last        +------+    |
                v<-link in latest hot (new end)      |
                |     link in latest warm (new end)->^
                |    +------+  W A R M   +------+    |
                +----| beg  |---->...----| end  |----+
                     +------+            +------+ins
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                  first for eviction
1122 1123 1124

    It is also possible that the block is selected for eviction and thus
    not linked in the LRU ring.
1125
*/
1126

1127 1128
static void link_block(KEY_CACHE *keycache, BLOCK_LINK *block, my_bool hot,
                       my_bool at_end)
1129
{
1130 1131 1132
  BLOCK_LINK *ins;
  BLOCK_LINK **pins;

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  DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE));
  DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/
  DBUG_ASSERT(!block->requests);
  DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
  DBUG_ASSERT(!block->next_used);
  DBUG_ASSERT(!block->prev_used);
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#ifdef THREAD
1140 1141
  if (!hot && keycache->waiting_for_block.last_thread)
  {
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    /* Signal that in the LRU warm sub-chain an available block has appeared */
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    struct st_my_thread_var *last_thread=
                               keycache->waiting_for_block.last_thread;
    struct st_my_thread_var *first_thread= last_thread->next;
    struct st_my_thread_var *next_thread= first_thread;
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    HASH_LINK *hash_link= (HASH_LINK *) first_thread->opt_info;
    struct st_my_thread_var *thread;
    do
    {
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      thread= next_thread;
      next_thread= thread->next;
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      /*
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         We notify about the event all threads that ask
         for the same page as the first thread in the queue
      */
      if ((HASH_LINK *) thread->opt_info == hash_link)
      {
1159
        KEYCACHE_DBUG_PRINT("link_block: signal", ("thread %ld", thread->id));
1160
        keycache_pthread_cond_signal(&thread->suspend);
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        unlink_from_queue(&keycache->waiting_for_block, thread);
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        block->requests++;
      }
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    }
1165
    while (thread != last_thread);
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    hash_link->block= block;
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    /*
      NOTE: We assigned the block to the hash_link and signalled the
      requesting thread(s). But it is possible that other threads runs
      first. These threads see the hash_link assigned to a block which
      is assigned to another hash_link and not marked BLOCK_IN_SWITCH.
      This can be a problem for functions that do not select the block
      via its hash_link: flush and free. They do only see a block which
      is in a "normal" state and don't know that it will be evicted soon.

      We cannot set BLOCK_IN_SWITCH here because only one of the
      requesting threads must handle the eviction. All others must wait
      for it to complete. If we set the flag here, the threads would not
      know who is in charge of the eviction. Without the flag, the first
      thread takes the stick and sets the flag.

      But we need to note in the block that is has been selected for
      eviction. It must not be freed. The evicting thread will not
      expect the block in the free list. Before freeing we could also
      check if block->requests > 1. But I think including another flag
      in the check of block->status is slightly more efficient and
      probably easier to read.
    */
    block->status|= BLOCK_IN_EVICTION;
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    KEYCACHE_THREAD_TRACE("link_block: after signaling");
#if defined(KEYCACHE_DEBUG)
1192
    KEYCACHE_DBUG_PRINT("link_block",
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        ("linked,unlinked block %u  status=%x  #requests=%u  #available=%u",
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         BLOCK_NUMBER(block), block->status,
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         block->requests, keycache->blocks_available));
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#endif
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    return;
  }
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#else /* THREAD */
  KEYCACHE_DBUG_ASSERT(! (!hot && keycache->waiting_for_block.last_thread));
      /* Condition not transformed using DeMorgan, to keep the text identical */
#endif /* THREAD */
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  pins= hot ? &keycache->used_ins : &keycache->used_last;
1204
  ins= *pins;
1205
  if (ins)
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  {
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    ins->next_used->prev_used= &block->next_used;
    block->next_used= ins->next_used;
    block->prev_used= &ins->next_used;
    ins->next_used= block;
1211
    if (at_end)
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      *pins= block;
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  }
  else
  {
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    /* The LRU ring is empty. Let the block point to itself. */
1217
    keycache->used_last= keycache->used_ins= block->next_used= block;
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    block->prev_used= &block->next_used;
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  }
  KEYCACHE_THREAD_TRACE("link_block");
#if defined(KEYCACHE_DEBUG)
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  keycache->blocks_available++;
1223
  KEYCACHE_DBUG_PRINT("link_block",
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      ("linked block %u:%1u  status=%x  #requests=%u  #available=%u",
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       BLOCK_NUMBER(block), at_end, block->status,
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       block->requests, keycache->blocks_available));
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  KEYCACHE_DBUG_ASSERT((ulong) keycache->blocks_available <=
                       keycache->blocks_used);
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#endif
}
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1232 1233

/*
1234
  Unlink a block from the LRU chain
1235 1236 1237

  SYNOPSIS
    unlink_block()
1238
      keycache            pointer to a key cache data structure
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      block               pointer to the block to unlink from the LRU chain

  RETURN VALUE
    none

  NOTES.
    See NOTES for link_block
1246
*/
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static void unlink_block(KEY_CACHE *keycache, BLOCK_LINK *block)
1249
{
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  DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE));
  DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/
  DBUG_ASSERT(!block->requests);
  DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
  DBUG_ASSERT(block->next_used && block->prev_used &&
              (block->next_used->prev_used == &block->next_used) &&
              (*block->prev_used == block));
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  if (block->next_used == block)
    /* The list contains only one member */
1259
    keycache->used_last= keycache->used_ins= NULL;
1260
  else
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  {
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    block->next_used->prev_used= block->prev_used;
    *block->prev_used= block->next_used;
    if (keycache->used_last == block)
      keycache->used_last= STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used);
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    if (keycache->used_ins == block)
      keycache->used_ins=STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used);
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  }
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  block->next_used= NULL;
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#if !defined(DBUG_OFF)
  /*
    This makes it easier to see it's not in a chain during debugging.
    And some DBUG_ASSERT() rely on it.
  */
  block->prev_used= NULL;
#endif
1277

1278 1279
  KEYCACHE_THREAD_TRACE("unlink_block");
#if defined(KEYCACHE_DEBUG)
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  KEYCACHE_DBUG_ASSERT(keycache->blocks_available != 0);
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  keycache->blocks_available--;
1282
  KEYCACHE_DBUG_PRINT("unlink_block",
1283
    ("unlinked block %u  status=%x   #requests=%u  #available=%u",
1284
     BLOCK_NUMBER(block), block->status,
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     block->requests, keycache->blocks_available));
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#endif
}


/*
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  Register requests for a block.

  SYNOPSIS
    reg_requests()
      keycache          Pointer to a key cache data structure.
      block             Pointer to the block to register a request on.
      count             Number of requests. Always 1.

  NOTE
    The first request unlinks the block from the LRU ring. This means
    that it is protected against eveiction.

  RETURN
    void
1305
*/
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static void reg_requests(KEY_CACHE *keycache, BLOCK_LINK *block, int count)
1307
{
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  DBUG_ASSERT(block->status & BLOCK_IN_USE);
  DBUG_ASSERT(block->hash_link);

  if (!block->requests)
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    unlink_block(keycache, block);
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  block->requests+=count;
}


1317 1318 1319
/*
  Unregister request for a block
  linking it to the LRU chain if it's the last request
1320 1321

  SYNOPSIS
1322 1323 1324 1325
    unreg_request()
    keycache            pointer to a key cache data structure
    block               pointer to the block to link to the LRU chain
    at_end              <-> to link the block at the end of the LRU chain
1326 1327 1328 1329

  RETURN VALUE
    none

1330
  NOTES.
1331
    Every linking to the LRU ring decrements by one a special block
1332 1333
    counter (if it's positive). If the at_end parameter is TRUE the block is
    added either at the end of warm sub-chain or at the end of hot sub-chain.
1334 1335
    It is added to the hot subchain if its counter is zero and number of
    blocks in warm sub-chain is not less than some low limit (determined by
1336 1337
    the division_limit parameter). Otherwise the block is added to the warm
    sub-chain. If the at_end parameter is FALSE the block is always added
1338
    at beginning of the warm sub-chain.
1339 1340 1341 1342
    Thus a warm block can be promoted to the hot sub-chain when its counter
    becomes zero for the first time.
    At the same time  the block at the very beginning of the hot subchain
    might be moved to the beginning of the warm subchain if it stays untouched
1343
    for a too long time (this time is determined by parameter age_threshold).
1344 1345 1346

    It is also possible that the block is selected for eviction and thus
    not linked in the LRU ring.
1347
*/
1348

1349 1350
static void unreg_request(KEY_CACHE *keycache,
                          BLOCK_LINK *block, int at_end)
1351
{
1352 1353 1354 1355 1356 1357
  DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
  DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/
  DBUG_ASSERT(block->requests);
  DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
  DBUG_ASSERT(!block->next_used);
  DBUG_ASSERT(!block->prev_used);
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  /*
    Unregister the request, but do not link erroneous blocks into the
    LRU ring.
  */
  if (!--block->requests && !(block->status & BLOCK_ERROR))
1363 1364 1365 1366 1367 1368 1369 1370
  {
    my_bool hot;
    if (block->hits_left)
      block->hits_left--;
    hot= !block->hits_left && at_end &&
      keycache->warm_blocks > keycache->min_warm_blocks;
    if (hot)
    {
1371 1372 1373
      if (block->temperature == BLOCK_WARM)
        keycache->warm_blocks--;
      block->temperature= BLOCK_HOT;
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      KEYCACHE_DBUG_PRINT("unreg_request", ("#warm_blocks: %lu",
1375 1376 1377 1378
                           keycache->warm_blocks));
    }
    link_block(keycache, block, hot, (my_bool)at_end);
    block->last_hit_time= keycache->keycache_time;
1379
    keycache->keycache_time++;
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    /*
      At this place, the block might be in the LRU ring or not. If an
      evicter was waiting for a block, it was selected for eviction and
      not linked in the LRU ring.
    */
1385

1386 1387 1388 1389 1390 1391 1392 1393 1394
    /*
      Check if we should link a hot block to the warm block sub-chain.
      It is possible that we select the same block as above. But it can
      also be another block. In any case a block from the LRU ring is
      selected. In other words it works even if the above block was
      selected for eviction and not linked in the LRU ring. Since this
      happens only if the LRU ring is empty, the block selected below
      would be NULL and the rest of the function skipped.
    */
1395 1396
    block= keycache->used_ins;
    if (block && keycache->keycache_time - block->last_hit_time >
1397 1398 1399 1400
	keycache->age_threshold)
    {
      unlink_block(keycache, block);
      link_block(keycache, block, 0, 0);
1401 1402 1403 1404 1405
      if (block->temperature != BLOCK_WARM)
      {
        keycache->warm_blocks++;
        block->temperature= BLOCK_WARM;
      }
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      KEYCACHE_DBUG_PRINT("unreg_request", ("#warm_blocks: %lu",
1407 1408 1409
                           keycache->warm_blocks));
    }
  }
1410 1411 1412
}

/*
1413
  Remove a reader of the page in block
1414
*/
1415

1416
static void remove_reader(BLOCK_LINK *block)
1417
{
1418 1419 1420 1421 1422 1423
  DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
  DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
  DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
  DBUG_ASSERT(!block->next_used);
  DBUG_ASSERT(!block->prev_used);
  DBUG_ASSERT(block->hash_link->requests);
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#ifdef THREAD
1425 1426
  if (! --block->hash_link->requests && block->condvar)
    keycache_pthread_cond_signal(block->condvar);
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#else
  --block->hash_link->requests;
#endif
1430 1431 1432 1433
}


/*
1434 1435
  Wait until the last reader of the page in block
  signals on its termination
1436
*/
1437

1438 1439
static void wait_for_readers(KEY_CACHE *keycache,
                             BLOCK_LINK *block)
1440
{
1441
#ifdef THREAD
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  struct st_my_thread_var *thread= my_thread_var;
1443
  DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
1444
  DBUG_ASSERT(!(block->status & (BLOCK_IN_FLUSH | BLOCK_CHANGED)));
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  DBUG_ASSERT(block->hash_link);
  DBUG_ASSERT(block->hash_link->block == block);
  /* Linked in file_blocks or changed_blocks hash. */
  DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
  /* Not linked in LRU ring. */
  DBUG_ASSERT(!block->next_used);
  DBUG_ASSERT(!block->prev_used);
1452 1453
  while (block->hash_link->requests)
  {
1454 1455 1456
    KEYCACHE_DBUG_PRINT("wait_for_readers: wait",
                        ("suspend thread %ld  block %u",
                         thread->id, BLOCK_NUMBER(block)));
1457 1458
    /* There must be no other waiter. We have no queue here. */
    DBUG_ASSERT(!block->condvar);
1459
    block->condvar= &thread->suspend;
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    keycache_pthread_cond_wait(&thread->suspend, &keycache->cache_lock);
1461
    block->condvar= NULL;
1462
  }
1463 1464 1465
#else
  KEYCACHE_DBUG_ASSERT(block->hash_link->requests == 0);
#endif
1466 1467 1468 1469
}


/*
1470
  Add a hash link to a bucket in the hash_table
1471
*/
1472

1473 1474 1475
static inline void link_hash(HASH_LINK **start, HASH_LINK *hash_link)
{
  if (*start)
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    (*start)->prev= &hash_link->next;
  hash_link->next= *start;
  hash_link->prev= start;
  *start= hash_link;
1480 1481 1482 1483
}


/*
1484
  Remove a hash link from the hash table
1485
*/
1486

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1487
static void unlink_hash(KEY_CACHE *keycache, HASH_LINK *hash_link)
1488
{
1489
  KEYCACHE_DBUG_PRINT("unlink_hash", ("fd: %u  pos_ %lu  #requests=%u",
1490 1491
      (uint) hash_link->file,(ulong) hash_link->diskpos, hash_link->requests));
  KEYCACHE_DBUG_ASSERT(hash_link->requests == 0);
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  if ((*hash_link->prev= hash_link->next))
    hash_link->next->prev= hash_link->prev;
  hash_link->block= NULL;
1495
#ifdef THREAD
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  if (keycache->waiting_for_hash_link.last_thread)
1497
  {
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    /* Signal that a free hash link has appeared */
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    struct st_my_thread_var *last_thread=
                               keycache->waiting_for_hash_link.last_thread;
    struct st_my_thread_var *first_thread= last_thread->next;
    struct st_my_thread_var *next_thread= first_thread;
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    KEYCACHE_PAGE *first_page= (KEYCACHE_PAGE *) (first_thread->opt_info);
    struct st_my_thread_var *thread;

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    hash_link->file= first_page->file;
    hash_link->diskpos= first_page->filepos;
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    do
    {
      KEYCACHE_PAGE *page;
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      thread= next_thread;
1512
      page= (KEYCACHE_PAGE *) thread->opt_info;
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      next_thread= thread->next;
1514
      /*
1515 1516 1517 1518 1519
         We notify about the event all threads that ask
         for the same page as the first thread in the queue
      */
      if (page->file == hash_link->file && page->filepos == hash_link->diskpos)
      {
1520
        KEYCACHE_DBUG_PRINT("unlink_hash: signal", ("thread %ld", thread->id));
1521
        keycache_pthread_cond_signal(&thread->suspend);
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        unlink_from_queue(&keycache->waiting_for_hash_link, thread);
1523 1524 1525
      }
    }
    while (thread != last_thread);
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    link_hash(&keycache->hash_root[KEYCACHE_HASH(hash_link->file,
					         hash_link->diskpos)],
              hash_link);
1529
    return;
1530
  }
1531 1532 1533
#else /* THREAD */
  KEYCACHE_DBUG_ASSERT(! (keycache->waiting_for_hash_link.last_thread));
#endif /* THREAD */
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1534 1535
  hash_link->next= keycache->free_hash_list;
  keycache->free_hash_list= hash_link;
1536 1537
}

1538

1539
/*
1540
  Get the hash link for a page
1541
*/
1542

1543
static HASH_LINK *get_hash_link(KEY_CACHE *keycache,
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                                int file, my_off_t filepos)
1545 1546 1547 1548 1549 1550
{
  reg1 HASH_LINK *hash_link, **start;
#if defined(KEYCACHE_DEBUG)
  int cnt;
#endif

1551
  KEYCACHE_DBUG_PRINT("get_hash_link", ("fd: %u  pos: %lu",
1552 1553 1554 1555 1556 1557 1558 1559
                      (uint) file,(ulong) filepos));

restart:
  /*
     Find the bucket in the hash table for the pair (file, filepos);
     start contains the head of the bucket list,
     hash_link points to the first member of the list
  */
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  hash_link= *(start= &keycache->hash_root[KEYCACHE_HASH(file, filepos)]);
1561
#if defined(KEYCACHE_DEBUG)
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  cnt= 0;
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#endif
  /* Look for an element for the pair (file, filepos) in the bucket chain */
  while (hash_link &&
         (hash_link->diskpos != filepos || hash_link->file != file))
  {
    hash_link= hash_link->next;
#if defined(KEYCACHE_DEBUG)
    cnt++;
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    if (! (cnt <= keycache->hash_links_used))
1572 1573
    {
      int i;
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      for (i=0, hash_link= *start ;
           i < cnt ; i++, hash_link= hash_link->next)
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      {
1577
        KEYCACHE_DBUG_PRINT("get_hash_link", ("fd: %u  pos: %lu",
1578 1579 1580
            (uint) hash_link->file,(ulong) hash_link->diskpos));
      }
    }
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    KEYCACHE_DBUG_ASSERT(cnt <= keycache->hash_links_used);
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#endif
  }
  if (! hash_link)
1585 1586
  {
    /* There is no hash link in the hash table for the pair (file, filepos) */
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    if (keycache->free_hash_list)
1588
    {
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      hash_link= keycache->free_hash_list;
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      keycache->free_hash_list= hash_link->next;
1591
    }
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    else if (keycache->hash_links_used < keycache->hash_links)
1593
    {
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      hash_link= &keycache->hash_link_root[keycache->hash_links_used++];
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    }
    else
1597
    {
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#ifdef THREAD
1599
      /* Wait for a free hash link */
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      struct st_my_thread_var *thread= my_thread_var;
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      KEYCACHE_PAGE page;
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      KEYCACHE_DBUG_PRINT("get_hash_link", ("waiting"));
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      page.file= file;
      page.filepos= filepos;
1605
      thread->opt_info= (void *) &page;
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      link_into_queue(&keycache->waiting_for_hash_link, thread);
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      KEYCACHE_DBUG_PRINT("get_hash_link: wait",
                        ("suspend thread %ld", thread->id));
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      keycache_pthread_cond_wait(&thread->suspend,
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                                 &keycache->cache_lock);
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      thread->opt_info= NULL;
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#else
      KEYCACHE_DBUG_ASSERT(0);
#endif
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      goto restart;
    }
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    hash_link->file= file;
    hash_link->diskpos= filepos;
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    link_hash(start, hash_link);
  }
  /* Register the request for the page */
  hash_link->requests++;
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  return hash_link;
}


/*
1629 1630
  Get a block for the file page requested by a keycache read/write operation;
  If the page is not in the cache return a free block, if there is none
1631
  return the lru block after saving its buffer if the page is dirty.
1632

1633 1634 1635
  SYNOPSIS

    find_key_block()
1636
      keycache            pointer to a key cache data structure
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      file                handler for the file to read page from
      filepos             position of the page in the file
      init_hits_left      how initialize the block counter for the page
      wrmode              <-> get for writing
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      page_st        out  {PAGE_READ,PAGE_TO_BE_READ,PAGE_WAIT_TO_BE_READ}
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  RETURN VALUE
    Pointer to the found block if successful, 0 - otherwise

  NOTES.
    For the page from file positioned at filepos the function checks whether
    the page is in the key cache specified by the first parameter.
    If this is the case it immediately returns the block.
    If not, the function first chooses  a block for this page. If there is
    no not used blocks in the key cache yet, the function takes the block
    at the very beginning of the warm sub-chain. It saves the page in that
1653
    block if it's dirty before returning the pointer to it.
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    The function returns in the page_st parameter the following values:
      PAGE_READ         - if page already in the block,
      PAGE_TO_BE_READ   - if it is to be read yet by the current thread
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      WAIT_TO_BE_READ   - if it is to be read by another thread
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    If an error occurs THE BLOCK_ERROR bit is set in the block status.
    It might happen that there are no blocks in LRU chain (in warm part) -
    all blocks  are unlinked for some read/write operations. Then the function
1661
    waits until first of this operations links any block back.
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*/

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static BLOCK_LINK *find_key_block(KEY_CACHE *keycache,
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                                  File file, my_off_t filepos,
                                  int init_hits_left,
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                                  int wrmode, int *page_st)
{
  HASH_LINK *hash_link;
  BLOCK_LINK *block;
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  int error= 0;
1672
  int page_status;
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  DBUG_ENTER("find_key_block");
  KEYCACHE_THREAD_TRACE("find_key_block:begin");
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  DBUG_PRINT("enter", ("fd: %d  pos: %lu  wrmode: %d",
                       file, (ulong) filepos, wrmode));
  KEYCACHE_DBUG_PRINT("find_key_block", ("fd: %d  pos: %lu  wrmode: %d",
                                         file, (ulong) filepos,
                                         wrmode));
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#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
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  DBUG_EXECUTE("check_keycache2",
               test_key_cache(keycache, "start of find_key_block", 0););
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#endif
1685

1686
restart:
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  /*
    If the flush phase of a resize operation fails, the cache is left
    unusable. This will be detected only after "goto restart".
  */
  if (!keycache->can_be_used)
    DBUG_RETURN(0);

  /*
    Find the hash_link for the requested file block (file, filepos). We
    do always get a hash_link here. It has registered our request so
    that no other thread can use it for another file block until we
    release the request (which is done by remove_reader() usually). The
    hash_link can have a block assigned to it or not. If there is a
    block, it may be assigned to this hash_link or not. In cases where a
    block is evicted from the cache, it is taken from the LRU ring and
    referenced by the new hash_link. But the block can still be assigned
    to its old hash_link for some time if it needs to be flushed first,
    or if there are other threads still reading it.

    Summary:
      hash_link is always returned.
      hash_link->block can be:
      - NULL or
      - not assigned to this hash_link or
      - assigned to this hash_link. If assigned, the block can have
        - invalid data (when freshly assigned) or
        - valid data. Valid data can be
          - changed over the file contents (dirty) or
          - not changed (clean).
  */
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  hash_link= get_hash_link(keycache, file, filepos);
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  DBUG_ASSERT((hash_link->file == file) && (hash_link->diskpos == filepos));
1719

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  page_status= -1;
  if ((block= hash_link->block) &&
1722
      block->hash_link == hash_link && (block->status & BLOCK_READ))
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  {
    /* Assigned block with valid (changed or unchanged) contents. */
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    page_status= PAGE_READ;
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  }
  /*
    else (page_status == -1)
      - block == NULL or
      - block not assigned to this hash_link or
      - block assigned but not yet read from file (invalid data).
  */
1733

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1734
#ifdef THREAD
1735
  if (keycache->in_resize)
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  {
1737
    /* This is a request during a resize operation */
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1739
    if (!block)
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    {
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      struct st_my_thread_var *thread;

      /*
        The file block is not in the cache. We don't need it in the
        cache: we are going to read or write directly to file. Cancel
        the request. We can simply decrement hash_link->requests because
        we did not release cache_lock since increasing it. So no other
        thread can wait for our request to become released.
      */
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      if (hash_link->requests == 1)
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      {
        /*
          We are the only one to request this hash_link (this file/pos).
          Free the hash_link.
        */
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        hash_link->requests--;
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        unlink_hash(keycache, hash_link);
        DBUG_RETURN(0);
      }

      /*
        More requests on the hash_link. Someone tries to evict a block
        for this hash_link (could have started before resizing started).
        This means that the LRU ring is empty. Otherwise a block could
        be assigned immediately. Behave like a thread that wants to
        evict a block for this file/pos. Add to the queue of threads
        waiting for a block. Wait until there is one assigned.

        Refresh the request on the hash-link so that it cannot be reused
        for another file/pos.
      */
      thread= my_thread_var;
      thread->opt_info= (void *) hash_link;
      link_into_queue(&keycache->waiting_for_block, thread);
      do
      {
        KEYCACHE_DBUG_PRINT("find_key_block: wait",
                            ("suspend thread %ld", thread->id));
        keycache_pthread_cond_wait(&thread->suspend,
                                   &keycache->cache_lock);
      } while (thread->next);
      thread->opt_info= NULL;
      /*
        A block should now be assigned to the hash_link. But it may
        still need to be evicted. Anyway, we should re-check the
        situation. page_status must be set correctly.
      */
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      hash_link->requests--;
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      goto restart;
    } /* end of if (!block) */

    /*
      There is a block for this file/pos in the cache. Register a
      request on it. This unlinks it from the LRU ring (if it is there)
      and hence protects it against eviction (if not already in
      eviction). We need this for returning the block to the caller, for
      calling remove_reader() (for debugging purposes), and for calling
      free_block(). The only case where we don't need the request is if
      the block is in eviction. In that case we have to unregister the
      request later.
    */
    reg_requests(keycache, block, 1);

    if (page_status != PAGE_READ)
    {
      /*
        - block not assigned to this hash_link or
        - block assigned but not yet read from file (invalid data).

        This must be a block in eviction. It will be read soon. We need
        to wait here until this happened. Otherwise the caller could
        access a wrong block or a block which is in read. While waiting
        we cannot lose hash_link nor block. We have registered a request
        on the hash_link. Everything can happen to the block but changes
        in the hash_link -> block relationship. In other words:
        everything can happen to the block but free or another completed
        eviction.

        Note that we bahave like a secondary requestor here. We just
        cannot return with PAGE_WAIT_TO_BE_READ. This would work for
        read requests and writes on dirty blocks that are not in flush
        only. Waiting here on COND_FOR_REQUESTED works in all
        situations.
      */
      DBUG_ASSERT(((block->hash_link != hash_link) &&
                   (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) ||
                  ((block->hash_link == hash_link) &&
                   !(block->status & BLOCK_READ)));
      wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock);
      /*
        Here we can trust that the block has been assigned to this
        hash_link (block->hash_link == hash_link) and read into the
        buffer (BLOCK_READ). The worst things possible here are that the
        block is in free (BLOCK_REASSIGNED). But the block is still
        assigned to the hash_link. The freeing thread waits until we
        release our request on the hash_link. The block must not be
        again in eviction because we registered an request on it before
        starting to wait.
      */
      DBUG_ASSERT(block->hash_link == hash_link);
      DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
      DBUG_ASSERT(!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH)));
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    }
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    /*
      The block is in the cache. Assigned to the hash_link. Valid data.
      Note that in case of page_st == PAGE_READ, the block can be marked
      for eviction. In any case it can be marked for freeing.
    */

    if (!wrmode)
    {
      /* A reader can just read the block. */
      *page_st= PAGE_READ;
      DBUG_ASSERT((hash_link->file == file) &&
                  (hash_link->diskpos == filepos) &&
                  (block->hash_link == hash_link));
      DBUG_RETURN(block);
    }

    /*
      This is a writer. No two writers for the same block can exist.
      This must be assured by locks outside of the key cache.
    */
    DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block));

    while (block->status & BLOCK_IN_FLUSH)
    {
      /*
        Wait until the block is flushed to file. Do not release the
        request on the hash_link yet to prevent that the block is freed
        or reassigned while we wait. While we wait, several things can
        happen to the block, including another flush. But the block
        cannot be reassigned to another hash_link until we release our
        request on it. But it can be marked BLOCK_REASSIGNED from free
        or eviction, while they wait for us to release the hash_link.
      */
      wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock);
      /*
        If the flush phase failed, the resize could have finished while
        we waited here.
      */
      if (!keycache->in_resize)
      {
        remove_reader(block);
        unreg_request(keycache, block, 1);
        goto restart;
      }
      DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
      DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block));
      DBUG_ASSERT(block->hash_link == hash_link);
    }

    if (block->status & BLOCK_CHANGED)
    {
      /*
        We want to write a block with changed contents. If the cache
        block size is bigger than the callers block size (e.g. MyISAM),
        the caller may replace part of the block only. Changes of the
        other part of the block must be preserved. Since the block has
        not yet been selected for flush, we can still add our changes.
      */
      *page_st= PAGE_READ;
      DBUG_ASSERT((hash_link->file == file) &&
                  (hash_link->diskpos == filepos) &&
                  (block->hash_link == hash_link));
      DBUG_RETURN(block);
    }

    /*
      This is a write request for a clean block. We do not want to have
      new dirty blocks in the cache while resizing. We will free the
      block and write directly to file. If the block is in eviction or
      in free, we just let it go.

      Unregister from the hash_link. This must be done before freeing
      the block. And it must be done if not freeing the block. Because
      we could have waited above, we need to call remove_reader(). Other
      threads could wait for us to release our request on the hash_link.
    */
    remove_reader(block);

    /* If the block is not in eviction and not in free, we can free it. */
    if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
                           BLOCK_REASSIGNED)))
1925
    {
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      /*
1927 1928 1929
        Free block as we are going to write directly to file.
        Although we have an exlusive lock for the updated key part,
        the control can be yielded by the current thread as we might
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        have unfinished readers of other key parts in the block
        buffer. Still we are guaranteed not to have any readers
        of the key part we are writing into until the block is
1933
        removed from the cache as we set the BLOCK_REASSIGNED
1934
        flag (see the code below that handles reading requests).
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      */
1936
      free_block(keycache, block);
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    }
1938
    else
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    {
1940
      /*
1941 1942
        The block will be evicted/freed soon. Don't touch it in any way.
        Unregister the request that we registered above.
1943
      */
1944 1945 1946 1947
      unreg_request(keycache, block, 1);

      /*
        The block is still assigned to the hash_link (the file/pos that
1948
        we are going to write to). Wait until the eviction/free is
1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972
        complete. Otherwise the direct write could complete before all
        readers are done with the block. So they could read outdated
        data.

        Since we released our request on the hash_link, it can be reused
        for another file/pos. Hence we cannot just check for
        block->hash_link == hash_link. As long as the resize is
        proceeding the block cannot be reassigned to the same file/pos
        again. So we can terminate the loop when the block is no longer
        assigned to this file/pos.
      */
      do
      {
        wait_on_queue(&block->wqueue[COND_FOR_SAVED],
                      &keycache->cache_lock);
        /*
          If the flush phase failed, the resize could have finished
          while we waited here.
        */
        if (!keycache->in_resize)
          goto restart;
      } while (block->hash_link &&
               (block->hash_link->file == file) &&
               (block->hash_link->diskpos == filepos));
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    }
1974
    DBUG_RETURN(0);
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  }
1976 1977 1978
#else /* THREAD */
  DBUG_ASSERT(!keycache->in_resize);
#endif
1979

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  if (page_status == PAGE_READ &&
1981 1982
      (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
                        BLOCK_REASSIGNED)))
1983
  {
1984 1985 1986 1987 1988 1989 1990 1991 1992
    /*
      This is a request for a block to be removed from cache. The block
      is assigned to this hash_link and contains valid data, but is
      marked for eviction or to be freed. Possible reasons why it has
      not yet been evicted/freed can be a flush before reassignment
      (BLOCK_IN_SWITCH), readers of the block have not finished yet
      (BLOCK_REASSIGNED), or the evicting thread did not yet awake after
      the block has been selected for it (BLOCK_IN_EVICTION).
    */
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1994
    KEYCACHE_DBUG_PRINT("find_key_block",
1995 1996 1997
                        ("request for old page in block %u "
                         "wrmode: %d  block->status: %d",
                         BLOCK_NUMBER(block), wrmode, block->status));
1998
    /*
1999 2000 2001 2002
       Only reading requests can proceed until the old dirty page is flushed,
       all others are to be suspended, then resubmitted
    */
    if (!wrmode && !(block->status & BLOCK_REASSIGNED))
2003 2004 2005 2006 2007 2008
    {
      /*
        This is a read request and the block not yet reassigned. We can
        register our request and proceed. This unlinks the block from
        the LRU ring and protects it against eviction.
      */
2009
      reg_requests(keycache, block, 1);
2010
    }
2011 2012
    else
    {
2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026
      /*
        Either this is a write request for a block that is in eviction
        or in free. We must not use it any more. Instead we must evict
        another block. But we cannot do this before the eviction/free is
        done. Otherwise we would find the same hash_link + block again
        and again.

        Or this is a read request for a block in eviction/free that does
        not require a flush, but waits for readers to finish with the
        block. We do not read this block to let the eviction/free happen
        as soon as possible. Again we must wait so that we don't find
        the same hash_link + block again and again.
      */
      DBUG_ASSERT(hash_link->requests);
2027
      hash_link->requests--;
2028
      KEYCACHE_DBUG_PRINT("find_key_block",
2029
                          ("request waiting for old page to be saved"));
2030
      wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock);
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      KEYCACHE_DBUG_PRINT("find_key_block",
2032
                          ("request for old page resubmitted"));
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      /*
        The block is no longer assigned to this hash_link.
        Get another one.
      */
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      goto restart;
    }
  }
  else
2041
  {
2042 2043 2044 2045 2046 2047 2048 2049 2050 2051
    /*
      This is a request for a new block or for a block not to be removed.
      Either
      - block == NULL or
      - block not assigned to this hash_link or
      - block assigned but not yet read from file,
      or
      - block assigned with valid (changed or unchanged) data and
      - it will not be reassigned/freed.
    */
2052
    if (! block)
2053
    {
2054
      /* No block is assigned to the hash_link yet. */
2055
      if (keycache->blocks_unused)
2056
      {
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        if (keycache->free_block_list)
        {
          /* There is a block in the free list. */
          block= keycache->free_block_list;
          keycache->free_block_list= block->next_used;
          block->next_used= NULL;
        }
        else
        {
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          size_t block_mem_offset;
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          /* There are some never used blocks, take first of them */
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          DBUG_ASSERT(keycache->blocks_used <
                      (ulong) keycache->disk_blocks);
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          block= &keycache->block_root[keycache->blocks_used];
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          block_mem_offset= 
           ((size_t) keycache->blocks_used) * keycache->key_cache_block_size;
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          block->buffer= ADD_TO_PTR(keycache->block_mem,
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                                    block_mem_offset,
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                                    uchar*);
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          keycache->blocks_used++;
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          DBUG_ASSERT(!block->next_used);
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        }
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        DBUG_ASSERT(!block->prev_used);
        DBUG_ASSERT(!block->next_changed);
        DBUG_ASSERT(!block->prev_changed);
        DBUG_ASSERT(!block->hash_link);
        DBUG_ASSERT(!block->status);
        DBUG_ASSERT(!block->requests);
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        keycache->blocks_unused--;
2086
        block->status= BLOCK_IN_USE;
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        block->length= 0;
        block->offset= keycache->key_cache_block_size;
        block->requests= 1;
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        block->temperature= BLOCK_COLD;
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        block->hits_left= init_hits_left;
        block->last_hit_time= 0;
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        block->hash_link= hash_link;
2094
        hash_link->block= block;
2095
        link_to_file_list(keycache, block, file, 0);
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        page_status= PAGE_TO_BE_READ;
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        KEYCACHE_DBUG_PRINT("find_key_block",
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                            ("got free or never used block %u",
                             BLOCK_NUMBER(block)));
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      }
      else
2102
      {
2103 2104 2105
	/*
          There are no free blocks and no never used blocks, use a block
          from the LRU ring.
2106
        */
2107

2108
#ifdef THREAD
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        if (! keycache->used_last)
2110
        {
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          /*
            The LRU ring is empty. Wait until a new block is added to
            it. Several threads might wait here for the same hash_link,
            all of them must get the same block. While waiting for a
            block, after a block is selected for this hash_link, other
            threads can run first before this one awakes. During this
            time interval other threads find this hash_link pointing to
            the block, which is still assigned to another hash_link. In
            this case the block is not marked BLOCK_IN_SWITCH yet, but
            it is marked BLOCK_IN_EVICTION.
          */

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          struct st_my_thread_var *thread= my_thread_var;
          thread->opt_info= (void *) hash_link;
          link_into_queue(&keycache->waiting_for_block, thread);
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          do
2127
          {
2128 2129
            KEYCACHE_DBUG_PRINT("find_key_block: wait",
                                ("suspend thread %ld", thread->id));
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            keycache_pthread_cond_wait(&thread->suspend,
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                                       &keycache->cache_lock);
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          }
          while (thread->next);
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          thread->opt_info= NULL;
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          /* Assert that block has a request registered. */
          DBUG_ASSERT(hash_link->block->requests);
          /* Assert that block is not in LRU ring. */
          DBUG_ASSERT(!hash_link->block->next_used);
          DBUG_ASSERT(!hash_link->block->prev_used);
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        }
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#else
        KEYCACHE_DBUG_ASSERT(keycache->used_last);
#endif
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        /*
          If we waited above, hash_link->block has been assigned by
          link_block(). Otherwise it is still NULL. In the latter case
          we need to grab a block from the LRU ring ourselves.
        */
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        block= hash_link->block;
2150 2151
        if (! block)
        {
2152
          /* Select the last block from the LRU ring. */
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          block= keycache->used_last->next_used;
2154 2155
          block->hits_left= init_hits_left;
          block->last_hit_time= 0;
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          hash_link->block= block;
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          /*
            Register a request on the block. This unlinks it from the
            LRU ring and protects it against eviction.
          */
          DBUG_ASSERT(!block->requests);
          reg_requests(keycache, block,1);
          /*
            We do not need to set block->status|= BLOCK_IN_EVICTION here
            because we will set block->status|= BLOCK_IN_SWITCH
            immediately without releasing the lock in between. This does
            also support debugging. When looking at the block, one can
            see if the block has been selected by link_block() after the
            LRU ring was empty, or if it was grabbed directly from the
            LRU ring in this branch.
          */
2172
        }
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        /*
          If we had to wait above, there is a small chance that another
          thread grabbed this block for the same file block already. But
          in most cases the first condition is true.
        */
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        if (block->hash_link != hash_link &&
	    ! (block->status & BLOCK_IN_SWITCH) )
        {
	  /* this is a primary request for a new page */
2183
          block->status|= BLOCK_IN_SWITCH;
2184 2185

          KEYCACHE_DBUG_PRINT("find_key_block",
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                        ("got block %u for new page", BLOCK_NUMBER(block)));
2187

2188
          if (block->status & BLOCK_CHANGED)
2189 2190 2191
          {
	    /* The block contains a dirty page - push it out of the cache */

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            KEYCACHE_DBUG_PRINT("find_key_block", ("block is dirty"));
2193 2194 2195 2196 2197 2198 2199
            if (block->status & BLOCK_IN_FLUSH)
            {
              /*
                The block is marked for flush. If we do not wait here,
                it could happen that we write the block, reassign it to
                another file block, then, before the new owner can read
                the new file block, the flusher writes the cache block
2200
                (which still has the old contents) to the new file block!
2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224
              */
              wait_on_queue(&block->wqueue[COND_FOR_SAVED],
                            &keycache->cache_lock);
              /*
                The block is marked BLOCK_IN_SWITCH. It should be left
                alone except for reading. No free, no write.
              */
              DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
              DBUG_ASSERT(!(block->status & (BLOCK_REASSIGNED |
                                             BLOCK_CHANGED |
                                             BLOCK_FOR_UPDATE)));
            }
            else
            {
              block->status|= BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE;
              /*
                BLOCK_IN_EVICTION may be true or not. Other flags must
                have a fixed value.
              */
              DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) ==
                          (BLOCK_READ | BLOCK_IN_SWITCH |
                           BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE |
                           BLOCK_CHANGED | BLOCK_IN_USE));
              DBUG_ASSERT(block->hash_link);
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              keycache_pthread_mutex_unlock(&keycache->cache_lock);
              /*
                The call is thread safe because only the current
                thread might change the block->hash_link value
              */
              error= my_pwrite(block->hash_link->file,
2232
                               block->buffer + block->offset,
2233
                               block->length - block->offset,
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                               block->hash_link->diskpos + block->offset,
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                               MYF(MY_NABP | MY_WAIT_IF_FULL));
              keycache_pthread_mutex_lock(&keycache->cache_lock);

              /* Block status must not have changed. */
              DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) ==
                          (BLOCK_READ | BLOCK_IN_SWITCH |
                           BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE |
                           BLOCK_CHANGED | BLOCK_IN_USE) || fail_block(block));
              keycache->global_cache_write++;
            }
2245
          }
2246

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          block->status|= BLOCK_REASSIGNED;
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          /*
            The block comes from the LRU ring. It must have a hash_link
            assigned.
          */
          DBUG_ASSERT(block->hash_link);
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          if (block->hash_link)
          {
2255
            /*
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              All pending requests for this page must be resubmitted.
              This must be done before waiting for readers. They could
              wait for the flush to complete. And we must also do it
              after the wait. Flushers might try to free the block while
              we wait. They would wait until the reassignment is
              complete. Also the block status must reflect the correct
              situation: The block is not changed nor in flush any more.
              Note that we must not change the BLOCK_CHANGED flag
              outside of link_to_file_list() so that it is always in the
              correct queue and the *blocks_changed counters are
              correct.
            */
            block->status&= ~(BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE);
            link_to_file_list(keycache, block, block->hash_link->file, 1);
            release_whole_queue(&block->wqueue[COND_FOR_SAVED]);
            /*
              The block is still assigned to its old hash_link.
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	      Wait until all pending read requests
	      for this page are executed
	      (we could have avoided this waiting, if we had read
	      a page in the cache in a sweep, without yielding control)
2277
            */
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            wait_for_readers(keycache, block);
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            DBUG_ASSERT(block->hash_link && block->hash_link->block == block &&
                        block->prev_changed);
            /* The reader must not have been a writer. */
            DBUG_ASSERT(!(block->status & BLOCK_CHANGED));

            /* Wake flushers that might have found the block in between. */
            release_whole_queue(&block->wqueue[COND_FOR_SAVED]);
2286

2287
            /* Remove the hash link for the old file block from the hash. */
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            unlink_hash(keycache, block->hash_link);
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            /*
              For sanity checks link_to_file_list() asserts that block
              and hash_link refer to each other. Hence we need to assign
              the hash_link first, but then we would not know if it was
              linked before. Hence we would not know if to unlink it. So
              unlink it here and call link_to_file_list(..., FALSE).
            */
            unlink_changed(block);
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          }
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          block->status= error ? BLOCK_ERROR : BLOCK_IN_USE ;
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          block->length= 0;
          block->offset= keycache->key_cache_block_size;
          block->hash_link= hash_link;
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          link_to_file_list(keycache, block, file, 0);
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          page_status= PAGE_TO_BE_READ;
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          KEYCACHE_DBUG_ASSERT(block->hash_link->block == block);
          KEYCACHE_DBUG_ASSERT(hash_link->block->hash_link == hash_link);
        }
        else
        {
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          /*
            Either (block->hash_link == hash_link),
	    or     (block->status & BLOCK_IN_SWITCH).

            This is for secondary requests for a new file block only.
            Either it is already assigned to the new hash_link meanwhile
            (if we had to wait due to empty LRU), or it is already in
            eviction by another thread. Since this block has been
            grabbed from the LRU ring and attached to this hash_link,
            another thread cannot grab the same block from the LRU ring
            anymore. If the block is in eviction already, it must become
            attached to the same hash_link and as such destined for the
            same file block.
          */
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          KEYCACHE_DBUG_PRINT("find_key_block",
                              ("block->hash_link: %p  hash_link: %p  "
                               "block->status: %u", block->hash_link,
                               hash_link, block->status ));
          page_status= (((block->hash_link == hash_link) &&
                         (block->status & BLOCK_READ)) ?
                        PAGE_READ : PAGE_WAIT_TO_BE_READ);
2332 2333 2334 2335 2336
        }
      }
    }
    else
    {
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      /*
        Block is not NULL. This hash_link points to a block.
        Either
        - block not assigned to this hash_link (yet) or
        - block assigned but not yet read from file,
        or
        - block assigned with valid (changed or unchanged) data and
        - it will not be reassigned/freed.

        The first condition means hash_link points to a block in
        eviction. This is not necessarily marked by BLOCK_IN_SWITCH yet.
        But then it is marked BLOCK_IN_EVICTION. See the NOTE in
        link_block(). In both cases it is destined for this hash_link
        and its file block address. When this hash_link got its block
        address, the block was removed from the LRU ring and cannot be
        selected for eviction (for another hash_link) again.

        Register a request on the block. This is another protection
        against eviction.
      */
      DBUG_ASSERT(((block->hash_link != hash_link) &&
                   (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) ||
                  ((block->hash_link == hash_link) &&
                   !(block->status & BLOCK_READ)) ||
                  ((block->status & BLOCK_READ) &&
                   !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))));
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      reg_requests(keycache, block, 1);
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      KEYCACHE_DBUG_PRINT("find_key_block",
                          ("block->hash_link: %p  hash_link: %p  "
                           "block->status: %u", block->hash_link,
                           hash_link, block->status ));
      page_status= (((block->hash_link == hash_link) &&
                     (block->status & BLOCK_READ)) ?
                    PAGE_READ : PAGE_WAIT_TO_BE_READ);
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    }
  }
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2374
  KEYCACHE_DBUG_ASSERT(page_status != -1);
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  /* Same assert basically, but be very sure. */
  KEYCACHE_DBUG_ASSERT(block);
  /* Assert that block has a request and is not in LRU ring. */
  DBUG_ASSERT(block->requests);
  DBUG_ASSERT(!block->next_used);
  DBUG_ASSERT(!block->prev_used);
  /* Assert that we return the correct block. */
  DBUG_ASSERT((page_status == PAGE_WAIT_TO_BE_READ) ||
              ((block->hash_link->file == file) &&
               (block->hash_link->diskpos == filepos)));
2385
  *page_st=page_status;
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  KEYCACHE_DBUG_PRINT("find_key_block",
2387
                      ("fd: %d  pos: %lu  block->status: %u  page_status: %d",
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                       file, (ulong) filepos, block->status,
2389
                       page_status));
2390

2391
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
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2392 2393
  DBUG_EXECUTE("check_keycache2",
               test_key_cache(keycache, "end of find_key_block",0););
2394 2395 2396 2397
#endif
  KEYCACHE_THREAD_TRACE("find_key_block:end");
  DBUG_RETURN(block);
}
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2398 2399


2400
/*
2401 2402 2403 2404 2405
  Read into a key cache block buffer from disk.

  SYNOPSIS

    read_block()
2406
      keycache            pointer to a key cache data structure
2407
      block               block to which buffer the data is to be read
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      read_length         size of data to be read
      min_length          at least so much data must be read
      primary             <-> the current thread will read the data

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  RETURN VALUE
    None

  NOTES.
    The function either reads a page data from file to the block buffer,
    or waits until another thread reads it. What page to read is determined
    by a block parameter - reference to a hash link for this page.
    If an error occurs THE BLOCK_ERROR bit is set in the block status.
    We do not report error when the size of successfully read
    portion is less than read_length, but not less than min_length.
2422
*/
2423

2424
static void read_block(KEY_CACHE *keycache,
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                       BLOCK_LINK *block, uint read_length,
2426 2427
                       uint min_length, my_bool primary)
{
2428
  size_t got_length;
2429

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2430
  /* On entry cache_lock is locked */
2431

2432 2433
  KEYCACHE_THREAD_TRACE("read_block");
  if (primary)
2434 2435
  {
    /*
2436 2437 2438 2439
      This code is executed only by threads that submitted primary
      requests. Until block->status contains BLOCK_READ, all other
      request for the block become secondary requests. For a primary
      request the block must be properly initialized.
2440
    */
2441 2442 2443 2444 2445 2446
    DBUG_ASSERT(((block->status & ~BLOCK_FOR_UPDATE) == BLOCK_IN_USE) ||
                fail_block(block));
    DBUG_ASSERT((block->length == 0) || fail_block(block));
    DBUG_ASSERT((block->offset == keycache->key_cache_block_size) ||
                fail_block(block));
    DBUG_ASSERT((block->requests > 0) || fail_block(block));
2447 2448

    KEYCACHE_DBUG_PRINT("read_block",
2449
                        ("page to be read by primary request"));
2450

2451
    keycache->global_cache_read++;
2452
    /* Page is not in buffer yet, is to be read from disk */
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    keycache_pthread_mutex_unlock(&keycache->cache_lock);
2454 2455 2456 2457
    /*
      Here other threads may step in and register as secondary readers.
      They will register in block->wqueue[COND_FOR_REQUESTED].
    */
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    got_length= my_pread(block->hash_link->file, block->buffer,
                         read_length, block->hash_link->diskpos, MYF(0));
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    keycache_pthread_mutex_lock(&keycache->cache_lock);
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    /*
      The block can now have been marked for free (in case of
      FLUSH_RELEASE). Otherwise the state must be unchanged.
    */
    DBUG_ASSERT(((block->status & ~(BLOCK_REASSIGNED |
                                    BLOCK_FOR_UPDATE)) == BLOCK_IN_USE) ||
                fail_block(block));
    DBUG_ASSERT((block->length == 0) || fail_block(block));
    DBUG_ASSERT((block->offset == keycache->key_cache_block_size) ||
                fail_block(block));
    DBUG_ASSERT((block->requests > 0) || fail_block(block));

2473
    if (got_length < min_length)
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      block->status|= BLOCK_ERROR;
2475 2476
    else
    {
2477
      block->status|= BLOCK_READ;
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      block->length= got_length;
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      /*
        Do not set block->offset here. If this block is marked
        BLOCK_CHANGED later, we want to flush only the modified part. So
        only a writer may set block->offset down from
        keycache->key_cache_block_size.
      */
2485
    }
2486
    KEYCACHE_DBUG_PRINT("read_block",
2487 2488
                        ("primary request: new page in cache"));
    /* Signal that all pending requests for this page now can be processed */
2489
    release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]);
2490
  }
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  else
  {
    /*
2494 2495 2496 2497 2498 2499 2500
      This code is executed only by threads that submitted secondary
      requests. At this point it could happen that the cache block is
      not yet assigned to the hash_link for the requested file block.
      But at awake from the wait this should be the case. Unfortunately
      we cannot assert this here because we do not know the hash_link
      for the requested file block nor the file and position. So we have
      to assert this in the caller.
2501
    */
2502
    KEYCACHE_DBUG_PRINT("read_block",
2503
                      ("secondary request waiting for new page to be read"));
2504
    wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock);
2505
    KEYCACHE_DBUG_PRINT("read_block",
2506 2507 2508 2509 2510 2511
                        ("secondary request: new page in cache"));
  }
}


/*
2512
  Read a block of data from a cached file into a buffer;
2513 2514 2515 2516

  SYNOPSIS

    key_cache_read()
2517
      keycache            pointer to a key cache data structure
2518 2519 2520
      file                handler for the file for the block of data to be read
      filepos             position of the block of data in the file
      level               determines the weight of the data
2521
      buff                buffer to where the data must be placed
2522
      length              length of the buffer
2523 2524 2525
      block_length        length of the block in the key cache buffer
      return_buffer       return pointer to the key cache buffer with the data

2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536
  RETURN VALUE
    Returns address from where the data is placed if sucessful, 0 - otherwise.

  NOTES.
    The function ensures that a block of data of size length from file
    positioned at filepos is in the buffers for some key cache blocks.
    Then the function either copies the data into the buffer buff, or,
    if return_buffer is TRUE, it just returns the pointer to the key cache
    buffer with the data.
    Filepos must be a multiple of 'block_length', but it doesn't
    have to be a multiple of key_cache_block_size;
2537
*/
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2538

2539
uchar *key_cache_read(KEY_CACHE *keycache,
2540 2541 2542 2543
                      File file, my_off_t filepos, int level,
                      uchar *buff, uint length,
                      uint block_length __attribute__((unused)),
                      int return_buffer __attribute__((unused)))
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{
2545
  my_bool locked_and_incremented= FALSE;
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2546
  int error=0;
2547
  uchar *start= buff;
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2548
  DBUG_ENTER("key_cache_read");
2549
  DBUG_PRINT("enter", ("fd: %u  pos: %lu  length: %u",
2550
               (uint) file, (ulong) filepos, length));
2551

2552
  if (keycache->key_cache_inited)
2553 2554
  {
    /* Key cache is used */
2555
    reg1 BLOCK_LINK *block;
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2556
    uint read_length;
2557
    uint offset;
2558
    int page_st;
2559

2560 2561 2562 2563 2564 2565 2566 2567 2568
    if (MYSQL_KEYCACHE_READ_START_ENABLED())
    {
      MYSQL_KEYCACHE_READ_START(my_filename(file), length,
                                (ulong) (keycache->blocks_used *
                                         keycache->key_cache_block_size),
                                (ulong) (keycache->blocks_unused *
                                         keycache->key_cache_block_size));
    }
  
2569
    /*
2570 2571 2572 2573
      When the key cache is once initialized, we use the cache_lock to
      reliably distinguish the cases of normal operation, resizing, and
      disabled cache. We always increment and decrement
      'cnt_for_resize_op' so that a resizer can wait for pending I/O.
2574
    */
2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593
    keycache_pthread_mutex_lock(&keycache->cache_lock);
    /*
      Cache resizing has two phases: Flushing and re-initializing. In
      the flush phase read requests are allowed to bypass the cache for
      blocks not in the cache. find_key_block() returns NULL in this
      case.

      After the flush phase new I/O requests must wait until the
      re-initialization is done. The re-initialization can be done only
      if no I/O request is in progress. The reason is that
      key_cache_block_size can change. With enabled cache, I/O is done
      in chunks of key_cache_block_size. Every chunk tries to use a
      cache block first. If the block size changes in the middle, a
      block could be missed and old data could be read.
    */
    while (keycache->in_resize && !keycache->resize_in_flush)
      wait_on_queue(&keycache->resize_queue, &keycache->cache_lock);
    /* Register the I/O for the next resize. */
    inc_counter_for_resize_op(keycache);
2594
    locked_and_incremented= TRUE;
2595
    /* Requested data may not always be aligned to cache blocks. */
2596
    offset= (uint) (filepos % keycache->key_cache_block_size);
2597
    /* Read data in key_cache_block_size increments */
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2598 2599
    do
    {
2600
      /* Cache could be disabled in a later iteration. */
2601
      if (!keycache->can_be_used)
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      {
2603 2604
        KEYCACHE_DBUG_PRINT("key_cache_read", ("keycache cannot be used"));
        goto no_key_cache;
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2605
      }
2606
      /* Start reading at the beginning of the cache block. */
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      filepos-= offset;
2608
      /* Do not read beyond the end of the cache block. */
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      read_length= length;
      set_if_smaller(read_length, keycache->key_cache_block_size-offset);
      KEYCACHE_DBUG_ASSERT(read_length > 0);

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2613 2614 2615 2616 2617
#ifndef THREAD
      if (block_length > keycache->key_cache_block_size || offset)
	return_buffer=0;
#endif

2618
      /* Request the cache block that matches file/pos. */
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2619
      keycache->global_cache_r_requests++;
2620 2621 2622

      MYSQL_KEYCACHE_READ_BLOCK(keycache->key_cache_block_size);

2623
      block=find_key_block(keycache, file, filepos, level, 0, &page_st);
2624
      if (!block)
2625 2626
      {
        /*
2627 2628 2629
          This happens only for requests submitted during key cache
          resize. The block is not in the cache and shall not go in.
          Read directly from file.
2630
        */
2631 2632
        keycache->global_cache_read++;
        keycache_pthread_mutex_unlock(&keycache->cache_lock);
2633
        error= (my_pread(file, (uchar*) buff, read_length,
2634
                         filepos + offset, MYF(MY_NABP)) != 0);
2635 2636 2637
        keycache_pthread_mutex_lock(&keycache->cache_lock);
        goto next_block;
      }
2638
      if (!(block->status & BLOCK_ERROR))
2639 2640 2641
      {
        if (page_st != PAGE_READ)
        {
2642
          MYSQL_KEYCACHE_READ_MISS();
2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666
          /* The requested page is to be read into the block buffer */
          read_block(keycache, block,
                     keycache->key_cache_block_size, read_length+offset,
                     (my_bool)(page_st == PAGE_TO_BE_READ));
          /*
            A secondary request must now have the block assigned to the
            requested file block. It does not hurt to check it for
            primary requests too.
          */
          DBUG_ASSERT(keycache->can_be_used);
          DBUG_ASSERT(block->hash_link->file == file);
          DBUG_ASSERT(block->hash_link->diskpos == filepos);
          DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
        }
        else if (block->length < read_length + offset)
        {
          /*
            Impossible if nothing goes wrong:
            this could only happen if we are using a file with
            small key blocks and are trying to read outside the file
          */
          my_errno= -1;
          block->status|= BLOCK_ERROR;
        }
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        else
        {
          MYSQL_KEYCACHE_READ_HIT();
        }
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2671
      }
2672

2673
      /* block status may have added BLOCK_ERROR in the above 'if'. */
2674
      if (!(block->status & BLOCK_ERROR))
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      {
2676
#ifndef THREAD
2677
        if (! return_buffer)
2678 2679
#endif
        {
2680
          DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
2681
#if !defined(SERIALIZED_READ_FROM_CACHE)
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2682
          keycache_pthread_mutex_unlock(&keycache->cache_lock);
2683
#endif
2684

2685
          /* Copy data from the cache buffer */
2686
          memcpy(buff, block->buffer+offset, (size_t) read_length);
2687 2688

#if !defined(SERIALIZED_READ_FROM_CACHE)
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2689
          keycache_pthread_mutex_lock(&keycache->cache_lock);
2690
          DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
2691 2692
#endif
        }
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2693
      }
2694

2695
      remove_reader(block);
2696

2697 2698 2699
      /* Error injection for coverage testing. */
      DBUG_EXECUTE_IF("key_cache_read_block_error",
                      block->status|= BLOCK_ERROR;);
2700

2701 2702 2703 2704 2705 2706 2707 2708 2709 2710
      /* Do not link erroneous blocks into the LRU ring, but free them. */
      if (!(block->status & BLOCK_ERROR))
      {
        /*
          Link the block into the LRU ring if it's the last submitted
          request for the block. This enables eviction for the block.
        */
        unreg_request(keycache, block, 1);
      }
      else
2711
      {
2712
        free_block(keycache, block);
2713 2714 2715
        error= 1;
        break;
      }
2716

2717
#ifndef THREAD
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      /* This is only true if we where able to read everything in one block */
2719
      if (return_buffer)
2720 2721 2722 2723 2724 2725 2726 2727
      {
        if (MYSQL_KEYCACHE_READ_DONE_ENABLED())
        {
          MYSQL_KEYCACHE_READ_DONE((ulong) (keycache->blocks_used *
                                            keycache->key_cache_block_size),
                                   (ulong) (keycache->blocks_unused *
                                            keycache->key_cache_block_size));
        }
2728
	DBUG_RETURN(block->buffer);
2729
      }
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2730
#endif
2731
    next_block:
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2732
      buff+= read_length;
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      filepos+= read_length+offset;
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2734
      offset= 0;
2735

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2736
    } while ((length-= read_length));
2737 2738 2739 2740 2741 2742 2743
    if (MYSQL_KEYCACHE_READ_DONE_ENABLED())
    {
      MYSQL_KEYCACHE_READ_DONE((ulong) (keycache->blocks_used *
                                        keycache->key_cache_block_size),
                               (ulong) (keycache->blocks_unused *
                                        keycache->key_cache_block_size));
    }
2744
    goto end;
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2745
  }
2746
  KEYCACHE_DBUG_PRINT("key_cache_read", ("keycache not initialized"));
2747

2748 2749
no_key_cache:
  /* Key cache is not used */
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2750 2751 2752

  keycache->global_cache_r_requests++;
  keycache->global_cache_read++;
2753

2754
  if (locked_and_incremented)
2755
    keycache_pthread_mutex_unlock(&keycache->cache_lock);
2756
  if (my_pread(file, (uchar*) buff, length, filepos, MYF(MY_NABP)))
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2757
    error= 1;
2758
  if (locked_and_incremented)
2759 2760 2761
    keycache_pthread_mutex_lock(&keycache->cache_lock);

end:
2762
  if (locked_and_incremented)
2763 2764 2765 2766
  {
    dec_counter_for_resize_op(keycache);
    keycache_pthread_mutex_unlock(&keycache->cache_lock);
  }
2767
  DBUG_PRINT("exit", ("error: %d", error ));
2768
  DBUG_RETURN(error ? (uchar*) 0 : start);
2769
}
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2770 2771


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2772 2773 2774 2775
/*
  Insert a block of file data from a buffer into key cache

  SYNOPSIS
2776
    key_cache_insert()
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2777 2778 2779 2780 2781 2782 2783 2784 2785 2786
    keycache            pointer to a key cache data structure
    file                handler for the file to insert data from
    filepos             position of the block of data in the file to insert
    level               determines the weight of the data
    buff                buffer to read data from
    length              length of the data in the buffer

  NOTES
    This is used by MyISAM to move all blocks from a index file to the key
    cache
2787

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2788
  RETURN VALUE
2789
    0 if a success, 1 - otherwise.
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2790 2791
*/

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2792
int key_cache_insert(KEY_CACHE *keycache,
2793
                     File file, my_off_t filepos, int level,
2794
                     uchar *buff, uint length)
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2795
{
2796
  int error= 0;
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2797
  DBUG_ENTER("key_cache_insert");
2798
  DBUG_PRINT("enter", ("fd: %u  pos: %lu  length: %u",
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2799 2800
               (uint) file,(ulong) filepos, length));

2801
  if (keycache->key_cache_inited)
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2802 2803 2804 2805
  {
    /* Key cache is used */
    reg1 BLOCK_LINK *block;
    uint read_length;
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2806
    uint offset;
2807
    int page_st;
2808
    my_bool locked_and_incremented= FALSE;
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2809

2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824
    /*
      When the keycache is once initialized, we use the cache_lock to
      reliably distinguish the cases of normal operation, resizing, and
      disabled cache. We always increment and decrement
      'cnt_for_resize_op' so that a resizer can wait for pending I/O.
    */
    keycache_pthread_mutex_lock(&keycache->cache_lock);
    /*
      We do not load index data into a disabled cache nor into an
      ongoing resize.
    */
    if (!keycache->can_be_used || keycache->in_resize)
	goto no_key_cache;
    /* Register the pseudo I/O for the next resize. */
    inc_counter_for_resize_op(keycache);
2825
    locked_and_incremented= TRUE;
2826
    /* Loaded data may not always be aligned to cache blocks. */
2827
    offset= (uint) (filepos % keycache->key_cache_block_size);
2828
    /* Load data in key_cache_block_size increments. */
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2829 2830
    do
    {
2831 2832 2833 2834
      /* Cache could be disabled or resizing in a later iteration. */
      if (!keycache->can_be_used || keycache->in_resize)
	goto no_key_cache;
      /* Start loading at the beginning of the cache block. */
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2835
      filepos-= offset;
2836
      /* Do not load beyond the end of the cache block. */
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2837 2838 2839
      read_length= length;
      set_if_smaller(read_length, keycache->key_cache_block_size-offset);
      KEYCACHE_DBUG_ASSERT(read_length > 0);
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2840

2841 2842 2843
      /* The block has been read by the caller already. */
      keycache->global_cache_read++;
      /* Request the cache block that matches file/pos. */
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2844
      keycache->global_cache_r_requests++;
2845
      block= find_key_block(keycache, file, filepos, level, 0, &page_st);
2846
      if (!block)
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2847
      {
2848
        /*
2849 2850 2851
          This happens only for requests submitted during key cache
          resize. The block is not in the cache and shall not go in.
          Stop loading index data.
2852
        */
2853 2854
        goto no_key_cache;
      }
2855
      if (!(block->status & BLOCK_ERROR))
2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909
      {
        if ((page_st == PAGE_WAIT_TO_BE_READ) ||
            ((page_st == PAGE_TO_BE_READ) &&
             (offset || (read_length < keycache->key_cache_block_size))))
        {
          /*
            Either

            this is a secondary request for a block to be read into the
            cache. The block is in eviction. It is not yet assigned to
            the requested file block (It does not point to the right
            hash_link). So we cannot call remove_reader() on the block.
            And we cannot access the hash_link directly here. We need to
            wait until the assignment is complete. read_block() executes
            the correct wait when called with primary == FALSE.

            Or

            this is a primary request for a block to be read into the
            cache and the supplied data does not fill the whole block.

            This function is called on behalf of a LOAD INDEX INTO CACHE
            statement, which is a read-only task and allows other
            readers. It is possible that a parallel running reader tries
            to access this block. If it needs more data than has been
            supplied here, it would report an error. To be sure that we
            have all data in the block that is available in the file, we
            read the block ourselves.

            Though reading again what the caller did read already is an
            expensive operation, we need to do this for correctness.
          */
          read_block(keycache, block, keycache->key_cache_block_size,
                     read_length + offset, (page_st == PAGE_TO_BE_READ));
          /*
            A secondary request must now have the block assigned to the
            requested file block. It does not hurt to check it for
            primary requests too.
          */
          DBUG_ASSERT(keycache->can_be_used);
          DBUG_ASSERT(block->hash_link->file == file);
          DBUG_ASSERT(block->hash_link->diskpos == filepos);
          DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
        }
        else if (page_st == PAGE_TO_BE_READ)
        {
          /*
            This is a new block in the cache. If we come here, we have
            data for the whole block.
          */
          DBUG_ASSERT(block->hash_link->requests);
          DBUG_ASSERT(block->status & BLOCK_IN_USE);
          DBUG_ASSERT((page_st == PAGE_TO_BE_READ) ||
                      (block->status & BLOCK_READ));
2910

2911 2912 2913 2914 2915 2916
#if !defined(SERIALIZED_READ_FROM_CACHE)
          keycache_pthread_mutex_unlock(&keycache->cache_lock);
          /*
            Here other threads may step in and register as secondary readers.
            They will register in block->wqueue[COND_FOR_REQUESTED].
          */
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2917 2918
#endif

2919
          /* Copy data from buff */
2920
          memcpy(block->buffer+offset, buff, (size_t) read_length);
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2921 2922

#if !defined(SERIALIZED_READ_FROM_CACHE)
2923 2924 2925 2926
          keycache_pthread_mutex_lock(&keycache->cache_lock);
          DBUG_ASSERT(block->status & BLOCK_IN_USE);
          DBUG_ASSERT((page_st == PAGE_TO_BE_READ) ||
                      (block->status & BLOCK_READ));
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2927
#endif
2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970
          /*
            After the data is in the buffer, we can declare the block
            valid. Now other threads do not need to register as
            secondary readers any more. They can immediately access the
            block.
          */
          block->status|= BLOCK_READ;
          block->length= read_length+offset;
          /*
            Do not set block->offset here. If this block is marked
            BLOCK_CHANGED later, we want to flush only the modified part. So
            only a writer may set block->offset down from
            keycache->key_cache_block_size.
          */
          KEYCACHE_DBUG_PRINT("key_cache_insert",
                              ("primary request: new page in cache"));
          /* Signal all pending requests. */
          release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]);
        }
        else
        {
          /*
            page_st == PAGE_READ. The block is in the buffer. All data
            must already be present. Blocks are always read with all
            data available on file. Assert that the block does not have
            less contents than the preloader supplies. If the caller has
            data beyond block->length, it means that a file write has
            been done while this block was in cache and not extended
            with the new data. If the condition is met, we can simply
            ignore the block.
          */
          DBUG_ASSERT((page_st == PAGE_READ) &&
                      (read_length + offset <= block->length));
        }

        /*
          A secondary request must now have the block assigned to the
          requested file block. It does not hurt to check it for primary
          requests too.
        */
        DBUG_ASSERT(block->hash_link->file == file);
        DBUG_ASSERT(block->hash_link->diskpos == filepos);
        DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
2971
      } /* end of if (!(block->status & BLOCK_ERROR)) */
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2972 2973

      remove_reader(block);
2974

2975 2976 2977
      /* Error injection for coverage testing. */
      DBUG_EXECUTE_IF("key_cache_insert_block_error",
                      block->status|= BLOCK_ERROR; errno=EIO;);
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2978

2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991
      /* Do not link erroneous blocks into the LRU ring, but free them. */
      if (!(block->status & BLOCK_ERROR))
      {
        /*
          Link the block into the LRU ring if it's the last submitted
          request for the block. This enables eviction for the block.
        */
        unreg_request(keycache, block, 1);
      }
      else
      {
        free_block(keycache, block);
        error= 1;
2992
        break;
2993
      }
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2994

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2995
      buff+= read_length;
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2996
      filepos+= read_length+offset;
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2997
      offset= 0;
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2998 2999

    } while ((length-= read_length));
3000 3001

  no_key_cache:
3002
    if (locked_and_incremented)
3003 3004
      dec_counter_for_resize_op(keycache);
    keycache_pthread_mutex_unlock(&keycache->cache_lock);
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3005
  }
3006
  DBUG_RETURN(error);
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3007 3008 3009
}


3010
/*
3011 3012
  Write a buffer into a cached file.

3013 3014 3015
  SYNOPSIS

    key_cache_write()
3016
      keycache            pointer to a key cache data structure
3017 3018 3019
      file                handler for the file to write data to
      filepos             position in the file to write data to
      level               determines the weight of the data
3020
      buff                buffer with the data
3021 3022
      length              length of the buffer
      dont_write          if is 0 then all dirty pages involved in writing
3023 3024
                          should have been flushed from key cache

3025 3026 3027 3028 3029 3030 3031
  RETURN VALUE
    0 if a success, 1 - otherwise.

  NOTES.
    The function copies the data of size length from buff into buffers
    for key cache blocks that are  assigned to contain the portion of
    the file starting with position filepos.
3032
    It ensures that this data is flushed to the file if dont_write is FALSE.
3033 3034
    Filepos must be a multiple of 'block_length', but it doesn't
    have to be a multiple of key_cache_block_size;
3035 3036

    dont_write is always TRUE in the server (info->lock_type is never F_UNLCK).
3037
*/
3038

unknown's avatar
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3039
int key_cache_write(KEY_CACHE *keycache,
3040
                    File file, my_off_t filepos, int level,
3041
                    uchar *buff, uint length,
3042 3043
                    uint block_length  __attribute__((unused)),
                    int dont_write)
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3044
{
3045
  my_bool locked_and_incremented= FALSE;
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3046
  int error=0;
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3047
  DBUG_ENTER("key_cache_write");
3048
  DBUG_PRINT("enter",
3049 3050 3051 3052
             ("fd: %u  pos: %lu  length: %u  block_length: %u"
              "  key_block_length: %u",
              (uint) file, (ulong) filepos, length, block_length,
              keycache ? keycache->key_cache_block_size : 0));
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3053 3054

  if (!dont_write)
3055
  {
3056 3057 3058 3059
    /* purecov: begin inspected */
    /* Not used in the server. */
    /* Force writing from buff into disk. */
    keycache->global_cache_w_requests++;
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3060
    keycache->global_cache_write++;
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3061
    if (my_pwrite(file, buff, length, filepos, MYF(MY_NABP | MY_WAIT_IF_FULL)))
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3062
      DBUG_RETURN(1);
3063
    /* purecov: end */
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3064
  }
3065

unknown's avatar
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3066
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
unknown's avatar
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3067 3068
  DBUG_EXECUTE("check_keycache",
               test_key_cache(keycache, "start of key_cache_write", 1););
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3069
#endif
3070

3071
  if (keycache->key_cache_inited)
3072 3073
  {
    /* Key cache is used */
3074
    reg1 BLOCK_LINK *block;
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3075
    uint read_length;
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3076
    uint offset;
3077
    int page_st;
3078

3079 3080 3081 3082 3083 3084 3085 3086 3087
    if (MYSQL_KEYCACHE_WRITE_START_ENABLED())
    {
      MYSQL_KEYCACHE_WRITE_START(my_filename(file), length,
                                 (ulong) (keycache->blocks_used *
                                          keycache->key_cache_block_size),
                                 (ulong) (keycache->blocks_unused *
                                          keycache->key_cache_block_size));
    }

3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113
    /*
      When the key cache is once initialized, we use the cache_lock to
      reliably distinguish the cases of normal operation, resizing, and
      disabled cache. We always increment and decrement
      'cnt_for_resize_op' so that a resizer can wait for pending I/O.
    */
    keycache_pthread_mutex_lock(&keycache->cache_lock);
    /*
      Cache resizing has two phases: Flushing and re-initializing. In
      the flush phase write requests can modify dirty blocks that are
      not yet in flush. Otherwise they are allowed to bypass the cache.
      find_key_block() returns NULL in both cases (clean blocks and
      non-cached blocks).

      After the flush phase new I/O requests must wait until the
      re-initialization is done. The re-initialization can be done only
      if no I/O request is in progress. The reason is that
      key_cache_block_size can change. With enabled cache I/O is done in
      chunks of key_cache_block_size. Every chunk tries to use a cache
      block first. If the block size changes in the middle, a block
      could be missed and data could be written below a cached block.
    */
    while (keycache->in_resize && !keycache->resize_in_flush)
      wait_on_queue(&keycache->resize_queue, &keycache->cache_lock);
    /* Register the I/O for the next resize. */
    inc_counter_for_resize_op(keycache);
3114
    locked_and_incremented= TRUE;
3115
    /* Requested data may not always be aligned to cache blocks. */
3116
    offset= (uint) (filepos % keycache->key_cache_block_size);
3117
    /* Write data in key_cache_block_size increments. */
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3118 3119
    do
    {
3120
      /* Cache could be disabled in a later iteration. */
3121
      if (!keycache->can_be_used)
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3122
	goto no_key_cache;
3123 3124

      MYSQL_KEYCACHE_WRITE_BLOCK(keycache->key_cache_block_size);
3125
      /* Start writing at the beginning of the cache block. */
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3126
      filepos-= offset;
3127
      /* Do not write beyond the end of the cache block. */
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3128 3129 3130
      read_length= length;
      set_if_smaller(read_length, keycache->key_cache_block_size-offset);
      KEYCACHE_DBUG_ASSERT(read_length > 0);
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3131

3132
      /* Request the cache block that matches file/pos. */
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3133
      keycache->global_cache_w_requests++;
3134
      block= find_key_block(keycache, file, filepos, level, 1, &page_st);
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3135 3136
      if (!block)
      {
3137 3138 3139 3140 3141 3142
        /*
          This happens only for requests submitted during key cache
          resize. The block is not in the cache and shall not go in.
          Write directly to file.
        */
        if (dont_write)
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3143
        {
3144
          /* Used in the server. */
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3145
          keycache->global_cache_write++;
3146
          keycache_pthread_mutex_unlock(&keycache->cache_lock);
3147
          if (my_pwrite(file, (uchar*) buff, read_length, filepos + offset,
3148
                        MYF(MY_NABP | MY_WAIT_IF_FULL)))
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3149
            error=1;
3150 3151
          keycache_pthread_mutex_lock(&keycache->cache_lock);
        }
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3152 3153
        goto next_block;
      }
3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173
      /*
        Prevent block from flushing and from being selected for to be
        freed. This must be set when we release the cache_lock.
        However, we must not set the status of the block before it is
        assigned to this file/pos.
      */
      if (page_st != PAGE_WAIT_TO_BE_READ)
        block->status|= BLOCK_FOR_UPDATE;
      /*
        We must read the file block first if it is not yet in the cache
        and we do not replace all of its contents.

        In cases where the cache block is big enough to contain (parts
        of) index blocks of different indexes, our request can be
        secondary (PAGE_WAIT_TO_BE_READ). In this case another thread is
        reading the file block. If the read completes after us, it
        overwrites our new contents with the old contents. So we have to
        wait for the other thread to complete the read of this block.
        read_block() takes care for the wait.
      */
3174
      if (!(block->status & BLOCK_ERROR) &&
3175 3176 3177 3178
          ((page_st == PAGE_TO_BE_READ &&
            (offset || read_length < keycache->key_cache_block_size)) ||
           (page_st == PAGE_WAIT_TO_BE_READ)))
      {
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3179 3180 3181
        read_block(keycache, block,
                   offset + read_length >= keycache->key_cache_block_size?
                   offset : keycache->key_cache_block_size,
3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237
                   offset, (page_st == PAGE_TO_BE_READ));
        DBUG_ASSERT(keycache->can_be_used);
        DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
        /*
          Prevent block from flushing and from being selected for to be
          freed. This must be set when we release the cache_lock.
          Here we set it in case we could not set it above.
        */
        block->status|= BLOCK_FOR_UPDATE;
      }
      /*
        The block should always be assigned to the requested file block
        here. It need not be BLOCK_READ when overwriting the whole block.
      */
      DBUG_ASSERT(block->hash_link->file == file);
      DBUG_ASSERT(block->hash_link->diskpos == filepos);
      DBUG_ASSERT(block->status & BLOCK_IN_USE);
      DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || (block->status & BLOCK_READ));
      /*
        The block to be written must not be marked BLOCK_REASSIGNED.
        Otherwise it could be freed in dirty state or reused without
        another flush during eviction. It must also not be in flush.
        Otherwise the old contens may have been flushed already and
        the flusher could clear BLOCK_CHANGED without flushing the
        new changes again.
      */
      DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED));

      while (block->status & BLOCK_IN_FLUSHWRITE)
      {
        /*
          Another thread is flushing the block. It was dirty already.
          Wait until the block is flushed to file. Otherwise we could
          modify the buffer contents just while it is written to file.
          An unpredictable file block contents would be the result.
          While we wait, several things can happen to the block,
          including another flush. But the block cannot be reassigned to
          another hash_link until we release our request on it.
        */
        wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock);
        DBUG_ASSERT(keycache->can_be_used);
        DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));
        /* Still must not be marked for free. */
        DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED));
        DBUG_ASSERT(block->hash_link && (block->hash_link->block == block));
      }

      /*
        We could perhaps release the cache_lock during access of the
        data like in the other functions. Locks outside of the key cache
        assure that readers and a writer do not access the same range of
        data. Parallel accesses should happen only if the cache block
        contains multiple index block(fragment)s. So different parts of
        the buffer would be read/written. An attempt to flush during
        memcpy() is prevented with BLOCK_FOR_UPDATE.
      */
3238
      if (!(block->status & BLOCK_ERROR))
3239 3240 3241 3242
      {
#if !defined(SERIALIZED_READ_FROM_CACHE)
        keycache_pthread_mutex_unlock(&keycache->cache_lock);
#endif
3243
        memcpy(block->buffer+offset, buff, (size_t) read_length);
3244 3245 3246 3247 3248

#if !defined(SERIALIZED_READ_FROM_CACHE)
        keycache_pthread_mutex_lock(&keycache->cache_lock);
#endif
      }
3249

3250
      if (!dont_write)
3251
      {
3252
        /* Not used in the server. buff has been written to disk at start. */
3253
        if ((block->status & BLOCK_CHANGED) &&
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3254 3255
            (!offset && read_length >= keycache->key_cache_block_size))
             link_to_file_list(keycache, block, block->hash_link->file, 1);
3256 3257
      }
      else if (! (block->status & BLOCK_CHANGED))
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3258
        link_to_changed_list(keycache, block);
3259 3260 3261 3262 3263 3264 3265
      block->status|=BLOCK_READ;
      /*
        Allow block to be selected for to be freed. Since it is marked
        BLOCK_CHANGED too, it won't be selected for to be freed without
        a flush.
      */
      block->status&= ~BLOCK_FOR_UPDATE;
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3266
      set_if_smaller(block->offset, offset);
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3267
      set_if_bigger(block->length, read_length+offset);
3268

3269 3270
      /* Threads may be waiting for the changes to be complete. */
      release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]);
3271

3272 3273 3274 3275 3276 3277 3278 3279 3280
      /*
        If only a part of the cache block is to be replaced, and the
        rest has been read from file, then the cache lock has been
        released for I/O and it could be possible that another thread
        wants to evict or free the block and waits for it to be
        released. So we must not just decrement hash_link->requests, but
        also wake a waiting thread.
      */
      remove_reader(block);
3281

3282 3283 3284
      /* Error injection for coverage testing. */
      DBUG_EXECUTE_IF("key_cache_write_block_error",
                      block->status|= BLOCK_ERROR;);
3285

3286 3287
      /* Do not link erroneous blocks into the LRU ring, but free them. */
      if (!(block->status & BLOCK_ERROR))
3288
      {
3289 3290 3291 3292 3293 3294 3295
        /*
          Link the block into the LRU ring if it's the last submitted
          request for the block. This enables eviction for the block.
        */
        unreg_request(keycache, block, 1);
      }
      else
3296
      {
3297 3298 3299
        /* Pretend a "clean" block to avoid complications. */
        block->status&= ~(BLOCK_CHANGED);
        free_block(keycache, block);
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3300
        error= 1;
3301 3302
        break;
      }
3303

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3304
    next_block:
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3305
      buff+= read_length;
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3306
      filepos+= read_length+offset;
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3307
      offset= 0;
3308

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3309
    } while ((length-= read_length));
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3310
    goto end;
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3311
  }
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3312 3313 3314 3315

no_key_cache:
  /* Key cache is not used */
  if (dont_write)
3316
  {
3317
    /* Used in the server. */
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3318 3319
    keycache->global_cache_w_requests++;
    keycache->global_cache_write++;
3320
    if (locked_and_incremented)
3321
      keycache_pthread_mutex_unlock(&keycache->cache_lock);
3322
    if (my_pwrite(file, (uchar*) buff, length, filepos,
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3323 3324
		  MYF(MY_NABP | MY_WAIT_IF_FULL)))
      error=1;
3325
    if (locked_and_incremented)
3326
      keycache_pthread_mutex_lock(&keycache->cache_lock);
3327
  }
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3328

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3329
end:
3330
  if (locked_and_incremented)
3331 3332 3333 3334
  {
    dec_counter_for_resize_op(keycache);
    keycache_pthread_mutex_unlock(&keycache->cache_lock);
  }
3335 3336 3337 3338 3339 3340 3341 3342 3343
  
  if (MYSQL_KEYCACHE_WRITE_DONE_ENABLED())
  {
    MYSQL_KEYCACHE_WRITE_DONE((ulong) (keycache->blocks_used *
                                       keycache->key_cache_block_size),
                              (ulong) (keycache->blocks_unused *
                                       keycache->key_cache_block_size));
  }
  
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3344
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
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3345 3346
  DBUG_EXECUTE("exec",
               test_key_cache(keycache, "end of key_cache_write", 1););
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3347
#endif
3348 3349
  DBUG_RETURN(error);
}
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3350 3351


3352
/*
3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376
  Free block.

  SYNOPSIS
    free_block()
      keycache          Pointer to a key cache data structure
      block             Pointer to the block to free

  DESCRIPTION
    Remove reference to block from hash table.
    Remove block from the chain of clean blocks.
    Add block to the free list.

  NOTE
    Block must not be free (status == 0).
    Block must not be in free_block_list.
    Block must not be in the LRU ring.
    Block must not be in eviction (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH).
    Block must not be in free (BLOCK_REASSIGNED).
    Block must not be in flush (BLOCK_IN_FLUSH).
    Block must not be dirty (BLOCK_CHANGED).
    Block must not be in changed_blocks (dirty) hash.
    Block must be in file_blocks (clean) hash.
    Block must refer to a hash_link.
    Block must have a request registered on it.
3377 3378
*/

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3379
static void free_block(KEY_CACHE *keycache, BLOCK_LINK *block)
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3380
{
3381
  KEYCACHE_THREAD_TRACE("free block");
3382
  KEYCACHE_DBUG_PRINT("free_block",
3383 3384 3385
                      ("block %u to be freed, hash_link %p  status: %u",
                       BLOCK_NUMBER(block), block->hash_link,
                       block->status));
3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410
  /*
    Assert that the block is not free already. And that it is in a clean
    state. Note that the block might just be assigned to a hash_link and
    not yet read (BLOCK_READ may not be set here). In this case a reader
    is registered in the hash_link and free_block() will wait for it
    below.
  */
  DBUG_ASSERT((block->status & BLOCK_IN_USE) &&
              !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
                                 BLOCK_REASSIGNED | BLOCK_IN_FLUSH |
                                 BLOCK_CHANGED | BLOCK_FOR_UPDATE)));
  /* Assert that the block is in a file_blocks chain. */
  DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
  /* Assert that the block is not in the LRU ring. */
  DBUG_ASSERT(!block->next_used && !block->prev_used);
  /*
    IMHO the below condition (if()) makes no sense. I can't see how it
    could be possible that free_block() is entered with a NULL hash_link
    pointer. The only place where it can become NULL is in free_block()
    (or before its first use ever, but for those blocks free_block() is
    not called). I don't remove the conditional as it cannot harm, but
    place an DBUG_ASSERT to confirm my hypothesis. Eventually the
    condition (if()) can be removed.
  */
  DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
3411
  if (block->hash_link)
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3412
  {
3413 3414 3415 3416 3417 3418
    /*
      While waiting for readers to finish, new readers might request the
      block. But since we set block->status|= BLOCK_REASSIGNED, they
      will wait on block->wqueue[COND_FOR_SAVED]. They must be signalled
      later.
    */
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3419 3420
    block->status|= BLOCK_REASSIGNED;
    wait_for_readers(keycache, block);
3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443
    /*
      The block must not have been freed by another thread. Repeat some
      checks. An additional requirement is that it must be read now
      (BLOCK_READ).
    */
    DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
    DBUG_ASSERT((block->status & (BLOCK_READ | BLOCK_IN_USE |
                                  BLOCK_REASSIGNED)) &&
                !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
                                   BLOCK_IN_FLUSH | BLOCK_CHANGED |
                                   BLOCK_FOR_UPDATE)));
    DBUG_ASSERT(block->prev_changed && *block->prev_changed == block);
    DBUG_ASSERT(!block->prev_used);
    /*
      Unset BLOCK_REASSIGNED again. If we hand the block to an evicting
      thread (through unreg_request() below), other threads must not see
      this flag. They could become confused.
    */
    block->status&= ~BLOCK_REASSIGNED;
    /*
      Do not release the hash_link until the block is off all lists.
      At least not if we hand it over for eviction in unreg_request().
    */
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3444
  }
3445

3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456
  /*
    Unregister the block request and link the block into the LRU ring.
    This enables eviction for the block. If the LRU ring was empty and
    threads are waiting for a block, then the block wil be handed over
    for eviction immediately. Otherwise we will unlink it from the LRU
    ring again, without releasing the lock in between. So decrementing
    the request counter and updating statistics are the only relevant
    operation in this case. Assert that there are no other requests
    registered.
  */
  DBUG_ASSERT(block->requests == 1);
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3457
  unreg_request(keycache, block, 0);
3458 3459 3460 3461 3462 3463 3464 3465
  /*
    Note that even without releasing the cache lock it is possible that
    the block is immediately selected for eviction by link_block() and
    thus not added to the LRU ring. In this case we must not touch the
    block any more.
  */
  if (block->status & BLOCK_IN_EVICTION)
    return;
3466

3467 3468 3469 3470 3471 3472 3473
  /* Error blocks are not put into the LRU ring. */
  if (!(block->status & BLOCK_ERROR))
  {
    /* Here the block must be in the LRU ring. Unlink it again. */
    DBUG_ASSERT(block->next_used && block->prev_used &&
                *block->prev_used == block);
    unlink_block(keycache, block);
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3474
  }
3475 3476 3477
  if (block->temperature == BLOCK_WARM)
    keycache->warm_blocks--;
  block->temperature= BLOCK_COLD;
3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495

  /* Remove from file_blocks hash. */
  unlink_changed(block);

  /* Remove reference to block from hash table. */
  unlink_hash(keycache, block->hash_link);
  block->hash_link= NULL;

  block->status= 0;
  block->length= 0;
  block->offset= keycache->key_cache_block_size;
  KEYCACHE_THREAD_TRACE("free block");
  KEYCACHE_DBUG_PRINT("free_block", ("block is freed"));

  /* Enforced by unlink_changed(), but just to be sure. */
  DBUG_ASSERT(!block->next_changed && !block->prev_changed);
  /* Enforced by unlink_block(): not in LRU ring nor in free_block_list. */
  DBUG_ASSERT(!block->next_used && !block->prev_used);
3496 3497 3498 3499 3500
  /* Insert the free block in the free list. */
  block->next_used= keycache->free_block_list;
  keycache->free_block_list= block;
  /* Keep track of the number of currently unused blocks. */
  keycache->blocks_unused++;
3501 3502

  /* All pending requests for this page must be resubmitted. */
3503
  release_whole_queue(&block->wqueue[COND_FOR_SAVED]);
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3504 3505 3506
}


3507
static int cmp_sec_link(BLOCK_LINK **a, BLOCK_LINK **b)
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3508
{
3509 3510
  return (((*a)->hash_link->diskpos < (*b)->hash_link->diskpos) ? -1 :
      ((*a)->hash_link->diskpos > (*b)->hash_link->diskpos) ? 1 : 0);
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3511 3512
}

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3513

3514 3515 3516
/*
  Flush a portion of changed blocks to disk,
  free used blocks if requested
3517
*/
3518

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3519 3520
static int flush_cached_blocks(KEY_CACHE *keycache,
                               File file, BLOCK_LINK **cache,
3521 3522
                               BLOCK_LINK **end,
                               enum flush_type type)
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3523
{
3524
  int error;
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3525
  int last_errno= 0;
3526
  uint count= (uint) (end-cache);
3527

3528
  /* Don't lock the cache during the flush */
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3529
  keycache_pthread_mutex_unlock(&keycache->cache_lock);
3530 3531 3532
  /*
     As all blocks referred in 'cache' are marked by BLOCK_IN_FLUSH
     we are guarunteed no thread will change them
3533
  */
3534
  my_qsort((uchar*) cache, count, sizeof(*cache), (qsort_cmp) cmp_sec_link);
3535

unknown's avatar
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3536
  keycache_pthread_mutex_lock(&keycache->cache_lock);
3537 3538 3539 3540 3541
  /*
    Note: Do not break the loop. We have registered a request on every
    block in 'cache'. These must be unregistered by free_block() or
    unreg_request().
  */
3542
  for ( ; cache != end ; cache++)
unknown's avatar
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3543
  {
3544
    BLOCK_LINK *block= *cache;
3545 3546

    KEYCACHE_DBUG_PRINT("flush_cached_blocks",
3547
                        ("block %u to be flushed", BLOCK_NUMBER(block)));
3548 3549 3550 3551 3552 3553
    /*
      If the block contents is going to be changed, we abandon the flush
      for this block. flush_key_blocks_int() will restart its search and
      handle the block properly.
    */
    if (!(block->status & BLOCK_FOR_UPDATE))
unknown's avatar
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3554
    {
3555 3556 3557 3558 3559 3560 3561 3562
      /* Blocks coming here must have a certain status. */
      DBUG_ASSERT(block->hash_link);
      DBUG_ASSERT(block->hash_link->block == block);
      DBUG_ASSERT(block->hash_link->file == file);
      DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) ==
                  (BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE));
      block->status|= BLOCK_IN_FLUSHWRITE;
      keycache_pthread_mutex_unlock(&keycache->cache_lock);
3563
      error= my_pwrite(file, block->buffer+block->offset,
3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589
                       block->length - block->offset,
                       block->hash_link->diskpos+ block->offset,
                       MYF(MY_NABP | MY_WAIT_IF_FULL));
      keycache_pthread_mutex_lock(&keycache->cache_lock);
      keycache->global_cache_write++;
      if (error)
      {
        block->status|= BLOCK_ERROR;
        if (!last_errno)
          last_errno= errno ? errno : -1;
      }
      block->status&= ~BLOCK_IN_FLUSHWRITE;
      /* Block must not have changed status except BLOCK_FOR_UPDATE. */
      DBUG_ASSERT(block->hash_link);
      DBUG_ASSERT(block->hash_link->block == block);
      DBUG_ASSERT(block->hash_link->file == file);
      DBUG_ASSERT((block->status & ~(BLOCK_FOR_UPDATE | BLOCK_IN_EVICTION)) ==
                  (BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE));
      /*
        Set correct status and link in right queue for free or later use.
        free_block() must not see BLOCK_CHANGED and it may need to wait
        for readers of the block. These should not see the block in the
        wrong hash. If not freeing the block, we need to have it in the
        right queue anyway.
      */
      link_to_file_list(keycache, block, file, 1);
3590
    }
3591
    block->status&= ~BLOCK_IN_FLUSH;
3592
    /*
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unknown committed
3593 3594 3595
      Let to proceed for possible waiting requests to write to the block page.
      It might happen only during an operation to resize the key cache.
    */
3596
    release_whole_queue(&block->wqueue[COND_FOR_SAVED]);
3597
    /* type will never be FLUSH_IGNORE_CHANGED here */
3598 3599 3600
    if (!(type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE) &&
        !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
                           BLOCK_FOR_UPDATE)))
3601
    {
3602 3603 3604 3605
      /*
        Note that a request has been registered against the block in
        flush_key_blocks_int().
      */
unknown's avatar
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3606
      free_block(keycache, block);
3607
    }
3608
    else
3609
    {
3610 3611 3612 3613 3614 3615
      /*
        Link the block into the LRU ring if it's the last submitted
        request for the block. This enables eviction for the block.
        Note that a request has been registered against the block in
        flush_key_blocks_int().
      */
unknown's avatar
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3616
      unreg_request(keycache, block, 1);
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3617
    }
3618

3619
  } /* end of for ( ; cache != end ; cache++) */
unknown's avatar
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3620 3621 3622 3623
  return last_errno;
}


3624
/*
3625
  Flush all key blocks for a file to disk, but don't do any mutex locks.
3626

3627
  SYNOPSIS
unknown's avatar
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3628
    flush_key_blocks_int()
3629
      keycache            pointer to a key cache data structure
3630 3631
      file                handler for the file to flush to
      flush_type          type of the flush
3632

3633 3634 3635 3636 3637
  NOTES
    This function doesn't do any mutex locks because it needs to be called both
    from flush_key_blocks and flush_all_key_blocks (the later one does the
    mutex lock in the resize_key_cache() function).

3638 3639 3640 3641
    We do only care about changed blocks that exist when the function is
    entered. We do not guarantee that all changed blocks of the file are
    flushed if more blocks change while this function is running.

3642 3643 3644 3645 3646
  RETURN
    0   ok
    1  error
*/

unknown's avatar
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3647
static int flush_key_blocks_int(KEY_CACHE *keycache,
3648
				File file, enum flush_type type)
unknown's avatar
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3649
{
3650
  BLOCK_LINK *cache_buff[FLUSH_CACHE],**cache;
unknown's avatar
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3651
  int last_errno= 0;
3652
  int last_errcnt= 0;
3653
  DBUG_ENTER("flush_key_blocks_int");
unknown's avatar
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3654
  DBUG_PRINT("enter",("file: %d  blocks_used: %lu  blocks_changed: %lu",
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3655
              file, keycache->blocks_used, keycache->blocks_changed));
3656

unknown's avatar
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3657
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
3658 3659
  DBUG_EXECUTE("check_keycache",
               test_key_cache(keycache, "start of flush_key_blocks", 0););
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3660
#endif
3661

unknown's avatar
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3662 3663
  cache= cache_buff;
  if (keycache->disk_blocks > 0 &&
3664
      (!my_disable_flush_key_blocks || type != FLUSH_KEEP))
3665 3666
  {
    /* Key cache exists and flush is not disabled */
unknown's avatar
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3667
    int error= 0;
3668
    uint count= FLUSH_CACHE;
3669
    BLOCK_LINK **pos,**end;
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3670
    BLOCK_LINK *first_in_switch= NULL;
3671 3672
    BLOCK_LINK *last_in_flush;
    BLOCK_LINK *last_for_update;
3673 3674 3675 3676
    BLOCK_LINK *block, *next;
#if defined(KEYCACHE_DEBUG)
    uint cnt=0;
#endif
3677

unknown's avatar
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3678 3679
    if (type != FLUSH_IGNORE_CHANGED)
    {
3680
      /*
3681 3682 3683
         Count how many key blocks we have to cache to be able
         to flush all dirty pages with minimum seek moves
      */
3684
      count= 0;
unknown's avatar
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3685
      for (block= keycache->changed_blocks[FILE_HASH(file)] ;
3686
           block ;
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3687
           block= block->next_changed)
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3688
      {
3689 3690
        if ((block->hash_link->file == file) &&
            !(block->status & BLOCK_IN_FLUSH))
3691
        {
3692
          count++;
unknown's avatar
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3693
          KEYCACHE_DBUG_ASSERT(count<= keycache->blocks_used);
3694
        }
unknown's avatar
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3695
      }
3696 3697 3698 3699 3700
      /*
        Allocate a new buffer only if its bigger than the one we have.
        Assure that we always have some entries for the case that new
        changed blocks appear while we need to wait for something.
      */
3701 3702 3703
      if ((count > FLUSH_CACHE) &&
          !(cache= (BLOCK_LINK**) my_malloc(sizeof(BLOCK_LINK*)*count,
                                            MYF(0))))
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3704
        cache= cache_buff;
3705 3706 3707 3708 3709
      /*
        After a restart there could be more changed blocks than now.
        So we should not let count become smaller than the fixed buffer.
      */
      if (cache == cache_buff)
3710
        count= FLUSH_CACHE;
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3711
    }
3712

3713 3714
    /* Retrieve the blocks and write them to a buffer to be flushed */
restart:
3715 3716
    last_in_flush= NULL;
    last_for_update= NULL;
unknown's avatar
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3717 3718
    end= (pos= cache)+count;
    for (block= keycache->changed_blocks[FILE_HASH(file)] ;
3719
         block ;
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3720
         block= next)
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3721
    {
3722 3723
#if defined(KEYCACHE_DEBUG)
      cnt++;
unknown's avatar
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3724
      KEYCACHE_DBUG_ASSERT(cnt <= keycache->blocks_used);
3725
#endif
unknown's avatar
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3726
      next= block->next_changed;
3727
      if (block->hash_link->file == file)
unknown's avatar
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3728
      {
3729
        if (!(block->status & (BLOCK_IN_FLUSH | BLOCK_FOR_UPDATE)))
3730
        {
3731 3732 3733 3734
          /*
            Note: The special handling of BLOCK_IN_SWITCH is obsolete
            since we set BLOCK_IN_FLUSH if the eviction includes a
            flush. It can be removed in a later version.
3735
          */
3736
          if (!(block->status & BLOCK_IN_SWITCH))
3737
          {
3738 3739 3740 3741 3742 3743 3744 3745
            /*
              We care only for the blocks for which flushing was not
              initiated by another thread and which are not in eviction.
              Registering a request on the block unlinks it from the LRU
              ring and protects against eviction.
            */
            reg_requests(keycache, block, 1);
            if (type != FLUSH_IGNORE_CHANGED)
3746
            {
3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762
              /* It's not a temporary file */
              if (pos == end)
              {
                /*
                  This should happen relatively seldom. Remove the
                  request because we won't do anything with the block
                  but restart and pick it again in the next iteration.
                */
                unreg_request(keycache, block, 0);
                /*
                  This happens only if there is not enough
                  memory for the big block
                */
                if ((error= flush_cached_blocks(keycache, file, cache,
                                                end,type)))
                {
3763
                  /* Do not loop infinitely trying to flush in vain. */
3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780
                  if ((last_errno == error) && (++last_errcnt > 5))
                    goto err;
                  last_errno= error;
                }
                /*
                  Restart the scan as some other thread might have changed
                  the changed blocks chain: the blocks that were in switch
                  state before the flush started have to be excluded
                */
                goto restart;
              }
              /*
                Mark the block with BLOCK_IN_FLUSH in order not to let
                other threads to use it for new pages and interfere with
                our sequence of flushing dirty file pages. We must not
                set this flag before actually putting the block on the
                write burst array called 'cache'.
3781
              */
3782 3783 3784 3785 3786 3787 3788 3789
              block->status|= BLOCK_IN_FLUSH;
              /* Add block to the array for a write burst. */
              *pos++= block;
            }
            else
            {
              /* It's a temporary file */
              DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED));
3790
              /*
3791 3792 3793 3794
                free_block() must not be called with BLOCK_CHANGED. Note
                that we must not change the BLOCK_CHANGED flag outside of
                link_to_file_list() so that it is always in the correct
                queue and the *blocks_changed counters are correct.
3795
              */
3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811
              link_to_file_list(keycache, block, file, 1);
              if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH)))
              {
                /* A request has been registered against the block above. */
                free_block(keycache, block);
              }
              else
              {
                /*
                  Link the block into the LRU ring if it's the last
                  submitted request for the block. This enables eviction
                  for the block. A request has been registered against
                  the block above.
                */
                unreg_request(keycache, block, 1);
              }
3812 3813 3814 3815
            }
          }
          else
          {
3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826
            /*
              Link the block into a list of blocks 'in switch'.

              WARNING: Here we introduce a place where a changed block
              is not in the changed_blocks hash! This is acceptable for
              a BLOCK_IN_SWITCH. Never try this for another situation.
              Other parts of the key cache code rely on changed blocks
              being in the changed_blocks hash.
            */
            unlink_changed(block);
            link_changed(block, &first_in_switch);
3827 3828
          }
        }
3829
        else if (type != FLUSH_KEEP)
3830
        {
3831 3832 3833 3834 3835 3836 3837 3838
          /*
            During the normal flush at end of statement (FLUSH_KEEP) we
            do not need to ensure that blocks in flush or update by
            other threads are flushed. They will be flushed by them
            later. In all other cases we must assure that we do not have
            any changed block of this file in the cache when this
            function returns.
          */
3839 3840 3841 3842 3843 3844 3845 3846 3847 3848
          if (block->status & BLOCK_IN_FLUSH)
          {
            /* Remember the last block found to be in flush. */
            last_in_flush= block;
          }
          else
          {
            /* Remember the last block found to be selected for update. */
            last_for_update= block;
          }
3849
        }
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3850 3851 3852 3853
      }
    }
    if (pos != cache)
    {
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3854
      if ((error= flush_cached_blocks(keycache, file, cache, pos, type)))
3855 3856 3857 3858
      {
        /* Do not loop inifnitely trying to flush in vain. */
        if ((last_errno == error) && (++last_errcnt > 5))
          goto err;
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3859
        last_errno= error;
3860 3861
      }
      /*
3862 3863 3864 3865 3866
        Do not restart here during the normal flush at end of statement
        (FLUSH_KEEP). We have now flushed at least all blocks that were
        changed when entering this function. In all other cases we must
        assure that we do not have any changed block of this file in the
        cache when this function returns.
3867
      */
3868 3869
      if (type != FLUSH_KEEP)
        goto restart;
3870 3871 3872 3873 3874 3875
    }
    if (last_in_flush)
    {
      /*
        There are no blocks to be flushed by this thread, but blocks in
        flush by other threads. Wait until one of the blocks is flushed.
3876 3877 3878 3879 3880 3881 3882
        Re-check the condition for last_in_flush. We may have unlocked
        the cache_lock in flush_cached_blocks(). The state of the block
        could have changed.
      */
      if (last_in_flush->status & BLOCK_IN_FLUSH)
        wait_on_queue(&last_in_flush->wqueue[COND_FOR_SAVED],
                      &keycache->cache_lock);
3883 3884 3885 3886 3887 3888 3889 3890
      /* Be sure not to lose a block. They may be flushed in random order. */
      goto restart;
    }
    if (last_for_update)
    {
      /*
        There are no blocks to be flushed by this thread, but blocks for
        update by other threads. Wait until one of the blocks is updated.
3891 3892 3893 3894 3895 3896 3897
        Re-check the condition for last_for_update. We may have unlocked
        the cache_lock in flush_cached_blocks(). The state of the block
        could have changed.
      */
      if (last_for_update->status & BLOCK_FOR_UPDATE)
        wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED],
                      &keycache->cache_lock);
3898 3899
      /* The block is now changed. Flush it. */
      goto restart;
3900
    }
3901 3902 3903 3904 3905 3906

    /*
      Wait until the list of blocks in switch is empty. The threads that
      are switching these blocks will relink them to clean file chains
      while we wait and thus empty the 'first_in_switch' chain.
    */
3907 3908 3909
    while (first_in_switch)
    {
#if defined(KEYCACHE_DEBUG)
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3910
      cnt= 0;
3911
#endif
3912 3913
      wait_on_queue(&first_in_switch->wqueue[COND_FOR_SAVED],
                    &keycache->cache_lock);
3914 3915
#if defined(KEYCACHE_DEBUG)
      cnt++;
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3916
      KEYCACHE_DBUG_ASSERT(cnt <= keycache->blocks_used);
3917
#endif
3918 3919 3920 3921 3922 3923
      /*
        Do not restart here. We have flushed all blocks that were
        changed when entering this function and were not marked for
        eviction. Other threads have now flushed all remaining blocks in
        the course of their eviction.
      */
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3924
    }
3925

3926
    if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE))
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3927
    {
3928 3929 3930 3931 3932 3933 3934 3935 3936 3937
      BLOCK_LINK *last_for_update= NULL;
      BLOCK_LINK *last_in_switch= NULL;
      uint total_found= 0;
      uint found;

      /*
        Finally free all clean blocks for this file.
        During resize this may be run by two threads in parallel.
      */
      do
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3938
      {
3939 3940 3941 3942
        found= 0;
        for (block= keycache->file_blocks[FILE_HASH(file)] ;
             block ;
             block= next)
3943
        {
3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965
          /* Remember the next block. After freeing we cannot get at it. */
          next= block->next_changed;

          /* Changed blocks cannot appear in the file_blocks hash. */
          DBUG_ASSERT(!(block->status & BLOCK_CHANGED));
          if (block->hash_link->file == file)
          {
            /* We must skip blocks that will be changed. */
            if (block->status & BLOCK_FOR_UPDATE)
            {
              last_for_update= block;
              continue;
            }

            /*
              We must not free blocks in eviction (BLOCK_IN_EVICTION |
              BLOCK_IN_SWITCH) or blocks intended to be freed
              (BLOCK_REASSIGNED).
            */
            if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH |
                                   BLOCK_REASSIGNED)))
            {
3966 3967 3968 3969 3970
              struct st_hash_link *UNINIT_VAR(next_hash_link);
              my_off_t UNINIT_VAR(next_diskpos);
              File UNINIT_VAR(next_file);
              uint UNINIT_VAR(next_status);
              uint UNINIT_VAR(hash_requests);
3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036

              total_found++;
              found++;
              KEYCACHE_DBUG_ASSERT(found <= keycache->blocks_used);

              /*
                Register a request. This unlinks the block from the LRU
                ring and protects it against eviction. This is required
                by free_block().
              */
              reg_requests(keycache, block, 1);

              /*
                free_block() may need to wait for readers of the block.
                This is the moment where the other thread can move the
                'next' block from the chain. free_block() needs to wait
                if there are requests for the block pending.
              */
              if (next && (hash_requests= block->hash_link->requests))
              {
                /* Copy values from the 'next' block and its hash_link. */
                next_status=    next->status;
                next_hash_link= next->hash_link;
                next_diskpos=   next_hash_link->diskpos;
                next_file=      next_hash_link->file;
                DBUG_ASSERT(next == next_hash_link->block);
              }

              free_block(keycache, block);
              /*
                If we had to wait and the state of the 'next' block
                changed, break the inner loop. 'next' may no longer be
                part of the current chain.

                We do not want to break the loop after every free_block(),
                not even only after waits. The chain might be quite long
                and contain blocks for many files. Traversing it again and
                again to find more blocks for this file could become quite
                inefficient.
              */
              if (next && hash_requests &&
                  ((next_status    != next->status) ||
                   (next_hash_link != next->hash_link) ||
                   (next_file      != next_hash_link->file) ||
                   (next_diskpos   != next_hash_link->diskpos) ||
                   (next           != next_hash_link->block)))
                break;
            }
            else
            {
              last_in_switch= block;
            }
          }
        } /* end for block in file_blocks */
      } while (found);

      /*
        If any clean block has been found, we may have waited for it to
        become free. In this case it could be possible that another clean
        block became dirty. This is possible if the write request existed
        before the flush started (BLOCK_FOR_UPDATE). Re-check the hashes.
      */
      if (total_found)
        goto restart;

      /*
4037
        To avoid an infinite loop, wait until one of the blocks marked
4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061
        for update is updated.
      */
      if (last_for_update)
      {
        /* We did not wait. Block must not have changed status. */
        DBUG_ASSERT(last_for_update->status & BLOCK_FOR_UPDATE);
        wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED],
                      &keycache->cache_lock);
        goto restart;
      }

      /*
        To avoid an infinite loop wait until one of the blocks marked
        for eviction is switched.
      */
      if (last_in_switch)
      {
        /* We did not wait. Block must not have changed status. */
        DBUG_ASSERT(last_in_switch->status & (BLOCK_IN_EVICTION |
                                              BLOCK_IN_SWITCH |
                                              BLOCK_REASSIGNED));
        wait_on_queue(&last_in_switch->wqueue[COND_FOR_SAVED],
                      &keycache->cache_lock);
        goto restart;
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4062
      }
4063 4064 4065 4066

    } /* if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE)) */

  } /* if (keycache->disk_blocks > 0 */
4067

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4068
#ifndef DBUG_OFF
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4069 4070
  DBUG_EXECUTE("check_keycache",
               test_key_cache(keycache, "end of flush_key_blocks", 0););
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4071
#endif
4072
err:
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4073
  if (cache != cache_buff)
4074
    my_free(cache);
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4075
  if (last_errno)
4076
    errno=last_errno;                /* Return first error */
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4077
  DBUG_RETURN(last_errno != 0);
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4078 4079 4080
}


4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093
/*
  Flush all blocks for a file to disk

  SYNOPSIS

    flush_key_blocks()
      keycache            pointer to a key cache data structure
      file                handler for the file to flush to
      flush_type          type of the flush

  RETURN
    0   ok
    1  error
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4094
*/
4095

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4096
int flush_key_blocks(KEY_CACHE *keycache,
4097 4098
                     File file, enum flush_type type)
{
4099
  int res= 0;
4100
  DBUG_ENTER("flush_key_blocks");
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4101
  DBUG_PRINT("enter", ("keycache: 0x%lx", (long) keycache));
4102

4103
  if (!keycache->key_cache_inited)
4104
    DBUG_RETURN(0);
4105

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  keycache_pthread_mutex_lock(&keycache->cache_lock);
4107 4108 4109 4110 4111 4112 4113
  /* While waiting for lock, keycache could have been ended. */
  if (keycache->disk_blocks > 0)
  {
    inc_counter_for_resize_op(keycache);
    res= flush_key_blocks_int(keycache, file, type);
    dec_counter_for_resize_op(keycache);
  }
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4114
  keycache_pthread_mutex_unlock(&keycache->cache_lock);
4115 4116 4117 4118
  DBUG_RETURN(res);
}


4119
/*
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  Flush all blocks in the key cache to disk.

  SYNOPSIS
    flush_all_key_blocks()
      keycache                  pointer to key cache root structure

  DESCRIPTION

    Flushing of the whole key cache is done in two phases.

    1. Flush all changed blocks, waiting for them if necessary. Loop
    until there is no changed block left in the cache.

    2. Free all clean blocks. Normally this means free all blocks. The
    changed blocks were flushed in phase 1 and became clean. However we
    may need to wait for blocks that are read by other threads. While we
    wait, a clean block could become changed if that operation started
    before the resize operation started. To be safe we must restart at
    phase 1.

    When we can run through the changed_blocks and file_blocks hashes
    without finding a block any more, then we are done.

    Note that we hold keycache->cache_lock all the time unless we need
    to wait for something.

  RETURN
    0           OK
    != 0        Error
4149
*/
4150

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4151
static int flush_all_key_blocks(KEY_CACHE *keycache)
4152
{
4153 4154 4155 4156 4157 4158 4159
  BLOCK_LINK    *block;
  uint          total_found;
  uint          found;
  uint          idx;
  DBUG_ENTER("flush_all_key_blocks");

  do
4160
  {
Marc Alff's avatar
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4161
    mysql_mutex_assert_owner(&keycache->cache_lock);
4162 4163
    total_found= 0;

4164 4165 4166 4167
    /*
      Phase1: Flush all changed blocks, waiting for them if necessary.
      Loop until there is no changed block left in the cache.
    */
4168
    do
4169
    {
4170 4171 4172
      found= 0;
      /* Step over the whole changed_blocks hash array. */
      for (idx= 0; idx < CHANGED_BLOCKS_HASH; idx++)
4173
      {
4174 4175
        /*
          If an array element is non-empty, use the first block from its
4176 4177 4178 4179 4180 4181
          chain to find a file for flush. All changed blocks for this
          file are flushed. So the same block will not appear at this
          place again with the next iteration. New writes for blocks are
          not accepted during the flush. If multiple files share the
          same hash bucket, one of them will be flushed per iteration
          of the outer loop of phase 1.
4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193
        */
        if ((block= keycache->changed_blocks[idx]))
        {
          found++;
          /*
            Flush dirty blocks but do not free them yet. They can be used
            for reading until all other blocks are flushed too.
          */
          if (flush_key_blocks_int(keycache, block->hash_link->file,
                                   FLUSH_FORCE_WRITE))
            DBUG_RETURN(1);
        }
4194
      }
4195 4196 4197

    } while (found);

4198 4199 4200 4201 4202 4203 4204 4205
    /*
      Phase 2: Free all clean blocks. Normally this means free all
      blocks. The changed blocks were flushed in phase 1 and became
      clean. However we may need to wait for blocks that are read by
      other threads. While we wait, a clean block could become changed
      if that operation started before the resize operation started. To
      be safe we must restart at phase 1.
    */
4206 4207 4208 4209 4210 4211 4212 4213 4214 4215
    do
    {
      found= 0;
      /* Step over the whole file_blocks hash array. */
      for (idx= 0; idx < CHANGED_BLOCKS_HASH; idx++)
      {
        /*
          If an array element is non-empty, use the first block from its
          chain to find a file for flush. All blocks for this file are
          freed. So the same block will not appear at this place again
4216 4217 4218
          with the next iteration. If multiple files share the
          same hash bucket, one of them will be flushed per iteration
          of the outer loop of phase 2.
4219 4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245
        */
        if ((block= keycache->file_blocks[idx]))
        {
          total_found++;
          found++;
          if (flush_key_blocks_int(keycache, block->hash_link->file,
                                   FLUSH_RELEASE))
            DBUG_RETURN(1);
        }
      }

    } while (found);

    /*
      If any clean block has been found, we may have waited for it to
      become free. In this case it could be possible that another clean
      block became dirty. This is possible if the write request existed
      before the resize started (BLOCK_FOR_UPDATE). Re-check the hashes.
    */
  } while (total_found);

#ifndef DBUG_OFF
  /* Now there should not exist any block any more. */
  for (idx= 0; idx < CHANGED_BLOCKS_HASH; idx++)
  {
    DBUG_ASSERT(!keycache->changed_blocks[idx]);
    DBUG_ASSERT(!keycache->file_blocks[idx]);
4246
  }
4247 4248 4249
#endif

  DBUG_RETURN(0);
4250
}
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4251 4252


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4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268
/*
  Reset the counters of a key cache.

  SYNOPSIS
    reset_key_cache_counters()
    name       the name of a key cache
    key_cache  pointer to the key kache to be reset

  DESCRIPTION
   This procedure is used by process_key_caches() to reset the counters of all
   currently used key caches, both the default one and the named ones.

  RETURN
    0 on success (always because it can't fail)
*/

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4269 4270
int reset_key_cache_counters(const char *name __attribute__((unused)),
                             KEY_CACHE *key_cache)
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4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288
{
  DBUG_ENTER("reset_key_cache_counters");
  if (!key_cache->key_cache_inited)
  {
    DBUG_PRINT("info", ("Key cache %s not initialized.", name));
    DBUG_RETURN(0);
  }
  DBUG_PRINT("info", ("Resetting counters for key cache %s.", name));

  key_cache->global_blocks_changed= 0;   /* Key_blocks_not_flushed */
  key_cache->global_cache_r_requests= 0; /* Key_read_requests */
  key_cache->global_cache_read= 0;       /* Key_reads */
  key_cache->global_cache_w_requests= 0; /* Key_write_requests */
  key_cache->global_cache_write= 0;      /* Key_writes */
  DBUG_RETURN(0);
}


4289 4290
#ifndef DBUG_OFF
/*
4291
  Test if disk-cache is ok
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4292
*/
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4293
static void test_key_cache(KEY_CACHE *keycache __attribute__((unused)),
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                           const char *where __attribute__((unused)),
4295 4296 4297
                           my_bool lock __attribute__((unused)))
{
  /* TODO */
4298
}
4299
#endif
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4300

4301 4302 4303 4304 4305 4306
#if defined(KEYCACHE_TIMEOUT)

#define KEYCACHE_DUMP_FILE  "keycache_dump.txt"
#define MAX_QUEUE_LEN  100


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4307
static void keycache_dump(KEY_CACHE *keycache)
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4308
{
4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333
  FILE *keycache_dump_file=fopen(KEYCACHE_DUMP_FILE, "w");
  struct st_my_thread_var *last;
  struct st_my_thread_var *thread;
  BLOCK_LINK *block;
  HASH_LINK *hash_link;
  KEYCACHE_PAGE *page;
  uint i;

  fprintf(keycache_dump_file, "thread:%u\n", thread->id);

  i=0;
  thread=last=waiting_for_hash_link.last_thread;
  fprintf(keycache_dump_file, "queue of threads waiting for hash link\n");
  if (thread)
    do
    {
      thread=thread->next;
      page= (KEYCACHE_PAGE *) thread->opt_info;
      fprintf(keycache_dump_file,
              "thread:%u, (file,filepos)=(%u,%lu)\n",
              thread->id,(uint) page->file,(ulong) page->filepos);
      if (++i == MAX_QUEUE_LEN)
        break;
    }
    while (thread != last);
4334

4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351
  i=0;
  thread=last=waiting_for_block.last_thread;
  fprintf(keycache_dump_file, "queue of threads waiting for block\n");
  if (thread)
    do
    {
      thread=thread->next;
      hash_link= (HASH_LINK *) thread->opt_info;
      fprintf(keycache_dump_file,
        "thread:%u hash_link:%u (file,filepos)=(%u,%lu)\n",
        thread->id, (uint) HASH_LINK_NUMBER(hash_link),
        (uint) hash_link->file,(ulong) hash_link->diskpos);
      if (++i == MAX_QUEUE_LEN)
        break;
    }
    while (thread != last);

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4352
  for (i=0 ; i< keycache->blocks_used ; i++)
4353 4354
  {
    int j;
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4355
    block= &keycache->block_root[i];
4356
    hash_link= block->hash_link;
4357 4358 4359 4360 4361 4362 4363
    fprintf(keycache_dump_file,
            "block:%u hash_link:%d status:%x #requests=%u waiting_for_readers:%d\n",
            i, (int) (hash_link ? HASH_LINK_NUMBER(hash_link) : -1),
            block->status, block->requests, block->condvar ? 1 : 0);
    for (j=0 ; j < 2; j++)
    {
      KEYCACHE_WQUEUE *wqueue=&block->wqueue[j];
4364
      thread= last= wqueue->last_thread;
4365 4366
      fprintf(keycache_dump_file, "queue #%d\n", j);
      if (thread)
4367
      {
4368 4369 4370 4371 4372 4373 4374 4375 4376
        do
        {
          thread=thread->next;
          fprintf(keycache_dump_file,
                  "thread:%u\n", thread->id);
          if (++i == MAX_QUEUE_LEN)
            break;
        }
        while (thread != last);
4377
      }
4378 4379 4380
    }
  }
  fprintf(keycache_dump_file, "LRU chain:");
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4381
  block= keycache= used_last;
4382
  if (block)
4383
  {
4384 4385
    do
    {
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4386
      block= block->next_used;
4387 4388 4389
      fprintf(keycache_dump_file,
              "block:%u, ", BLOCK_NUMBER(block));
    }
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4390
    while (block != keycache->used_last);
4391
  }
4392
  fprintf(keycache_dump_file, "\n");
4393

4394
  fclose(keycache_dump_file);
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4395 4396
}

4397
#endif /* defined(KEYCACHE_TIMEOUT) */
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4398

4399
#if defined(KEYCACHE_TIMEOUT) && !defined(__WIN__)
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4400 4401


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4402 4403
static int keycache_pthread_cond_wait(mysql_cond_t *cond,
                                      mysql_mutex_t *mutex)
4404 4405 4406 4407 4408 4409 4410 4411
{
  int rc;
  struct timeval  now;            /* time when we started waiting        */
  struct timespec timeout;        /* timeout value for the wait function */
  struct timezone tz;
#if defined(KEYCACHE_DEBUG)
  int cnt=0;
#endif
4412 4413

  /* Get current time */
4414 4415
  gettimeofday(&now, &tz);
  /* Prepare timeout value */
4416
  timeout.tv_sec= now.tv_sec + KEYCACHE_TIMEOUT;
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 /*
   timeval uses microseconds.
   timespec uses nanoseconds.
   1 nanosecond = 1000 micro seconds
 */
  timeout.tv_nsec= now.tv_usec * 1000;
4423 4424 4425 4426 4427 4428 4429
  KEYCACHE_THREAD_TRACE_END("started waiting");
#if defined(KEYCACHE_DEBUG)
  cnt++;
  if (cnt % 100 == 0)
    fprintf(keycache_debug_log, "waiting...\n");
    fflush(keycache_debug_log);
#endif
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  rc= mysql_cond_timedwait(cond, mutex, &timeout);
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  KEYCACHE_THREAD_TRACE_BEGIN("finished waiting");
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  if (rc == ETIMEDOUT || rc == ETIME)
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  {
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#if defined(KEYCACHE_DEBUG)
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    fprintf(keycache_debug_log,"aborted by keycache timeout\n");
    fclose(keycache_debug_log);
    abort();
#endif
    keycache_dump();
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  }
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#if defined(KEYCACHE_DEBUG)
  KEYCACHE_DBUG_ASSERT(rc != ETIMEDOUT);
#else
  assert(rc != ETIMEDOUT);
#endif
  return rc;
}
#else
#if defined(KEYCACHE_DEBUG)
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static int keycache_pthread_cond_wait(mysql_cond_t *cond,
                                      mysql_mutex_t *mutex)
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{
  int rc;
  KEYCACHE_THREAD_TRACE_END("started waiting");
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  rc= mysql_cond_wait(cond, mutex);
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  KEYCACHE_THREAD_TRACE_BEGIN("finished waiting");
  return rc;
}
#endif
#endif /* defined(KEYCACHE_TIMEOUT) && !defined(__WIN__) */
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#if defined(KEYCACHE_DEBUG)
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static int keycache_pthread_mutex_lock(mysql_mutex_t *mutex)
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{
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  int rc;
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  rc= mysql_mutex_lock(mutex);
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  KEYCACHE_THREAD_TRACE_BEGIN("");
  return rc;
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}
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static void keycache_pthread_mutex_unlock(mysql_mutex_t *mutex)
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{
  KEYCACHE_THREAD_TRACE_END("");
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  mysql_mutex_unlock(mutex);
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}
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static int keycache_pthread_cond_signal(mysql_cond_t *cond)
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{
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  int rc;
  KEYCACHE_THREAD_TRACE("signal");
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  rc= mysql_cond_signal(cond);
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  return rc;
}
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#if defined(KEYCACHE_DEBUG_LOG)
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static void keycache_debug_print(const char * fmt,...)
{
  va_list args;
  va_start(args,fmt);
  if (keycache_debug_log)
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  {
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    (void) vfprintf(keycache_debug_log, fmt, args);
    (void) fputc('\n',keycache_debug_log);
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  }
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  va_end(args);
}
#endif /* defined(KEYCACHE_DEBUG_LOG) */
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#if defined(KEYCACHE_DEBUG_LOG)


void keycache_debug_log_close(void)
{
  if (keycache_debug_log)
    fclose(keycache_debug_log);
}
#endif /* defined(KEYCACHE_DEBUG_LOG) */

#endif /* defined(KEYCACHE_DEBUG) */
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#if !defined(DBUG_OFF)
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#define F_B_PRT(_f_, _v_) DBUG_PRINT("assert_fail", (_f_, _v_))
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static int fail_block(BLOCK_LINK *block)
{
  F_B_PRT("block->next_used:    %lx\n", (ulong) block->next_used);
  F_B_PRT("block->prev_used:    %lx\n", (ulong) block->prev_used);
  F_B_PRT("block->next_changed: %lx\n", (ulong) block->next_changed);
  F_B_PRT("block->prev_changed: %lx\n", (ulong) block->prev_changed);
  F_B_PRT("block->hash_link:    %lx\n", (ulong) block->hash_link);
  F_B_PRT("block->status:       %u\n", block->status);
  F_B_PRT("block->length:       %u\n", block->length);
  F_B_PRT("block->offset:       %u\n", block->offset);
  F_B_PRT("block->requests:     %u\n", block->requests);
  F_B_PRT("block->temperature:  %u\n", block->temperature);
  return 0; /* Let the assert fail. */
}

static int fail_hlink(HASH_LINK *hlink)
{
  F_B_PRT("hlink->next:    %lx\n", (ulong) hlink->next);
  F_B_PRT("hlink->prev:    %lx\n", (ulong) hlink->prev);
  F_B_PRT("hlink->block:   %lx\n", (ulong) hlink->block);
  F_B_PRT("hlink->diskpos: %lu\n", (ulong) hlink->diskpos);
  F_B_PRT("hlink->file:    %d\n", hlink->file);
  return 0; /* Let the assert fail. */
}

static int cache_empty(KEY_CACHE *keycache)
{
  int errcnt= 0;
  int idx;
  if (keycache->disk_blocks <= 0)
    return 1;
  for (idx= 0; idx < keycache->disk_blocks; idx++)
  {
    BLOCK_LINK *block= keycache->block_root + idx;
    if (block->status || block->requests || block->hash_link)
    {
      fprintf(stderr, "block index: %u\n", idx);
      fail_block(block);
      errcnt++;
    }
  }
  for (idx= 0; idx < keycache->hash_links; idx++)
  {
    HASH_LINK *hash_link= keycache->hash_link_root + idx;
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    if (hash_link->requests || hash_link->block)
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    {
      fprintf(stderr, "hash_link index: %u\n", idx);
      fail_hlink(hash_link);
      errcnt++;
    }
  }
  if (errcnt)
  {
    fprintf(stderr, "blocks: %d  used: %lu\n",
            keycache->disk_blocks, keycache->blocks_used);
    fprintf(stderr, "hash_links: %d  used: %d\n",
            keycache->hash_links, keycache->hash_links_used);
    fprintf(stderr, "\n");
  }
  return !errcnt;
}
#endif