1. 19 May, 2002 25 commits
    • Andrew Morton's avatar
      [PATCH] fix ext3 race with writeback · 5409c2b5
      Andrew Morton authored
      The ext3-no-steal patch has exposed a long-standing race in ext3.  It
      has been there all the time in 2.4, but never triggered until some
      timing change in the ext3-no-steal patch exposed it.  The race was not
      present in 2.2 because 2.2's bdflush runs inside lock_kernel().
      
      The problem is that when ext3 is shuffling a buffer between journalling
      lists there is a small window where the buffer is marked BH_dirty.
      Aonther CPU can grab it, mark it clean and write it out.  Then ext3
      puts the buffer onto a list of buffers which are expected to be dirty,
      and gets confused later on when the buffer turns out to be clean.
      
      The patch from Stephen records the expected dirtiness of the buffer in
      a local variable, so BH_dirty is not transiently set while ext3
      shuffles.
      5409c2b5
    • Andrew Morton's avatar
      [PATCH] fix ext3 buffer-stealing · d9ae0cee
      Andrew Morton authored
      Patch from sct fixes a long-standing (I did it!) and rather complex
      problem with ext3.
      
      The problem is to do with buffers which are continually being dirtied
      by an external agent.  I had code in there (for easily-triggerable
      livelock avoidance) which steals the buffer from checkpoint mode and
      reattaches it to the running transaction.  This violates ext3 ordering
      requirements - it can permit journal space to be reclaimed before the
      relevant data has really been written out.
      
      Also, we do have to reliably get a lock on the buffer when moving it
      between lists and inspecting its internal state.  Otherwise a competing
      read from the underlying block device can trigger an assertion failure,
      and a competing write to the underlying block device can confuse ext3
      journalling state completely.
      d9ae0cee
    • Andrew Morton's avatar
      [PATCH] improved I/O scheduling for indirect blocks · 799391cc
      Andrew Morton authored
      Fixes a performance problem with many-small-file writeout.
      
      At present, files are written out via their mapping and their indirect
      blocks are written out via the blockdev mapping.  As we know that
      indirects are disk-adjacent to the data it is better to start I/O
      against the indirects at the same time as the data.
      
      The delalloc pathes have code in ext2_writepage() which recognises when
      the target page->index was at an indirect boundary and does an explicit
      hunt-and-write against the neighbouring indirect block.  Which is
      ideal.  (Unless the file was dirtied seekily and the page which is next
      to the indirect was not dirtied).
      
      This patch does it the other way: when we start writeback against a
      mapping, also start writeback against any dirty buffers which are
      attached to mapping->private_list.  Let the elevator take care of the
      rest.
      
      The patch makes a number of tuning changes to the writeback path in
      fs-writeback.c.  This is very fiddly code: getting the throughput
      tuned, getting the data-integrity "sync" operations right, avoiding
      most of the livelock opportunities, getting the `kupdate' function
      working efficiently, keeping it all least somewhat comprehensible.
      
      An important intent here is to ensure that metadata blocks for inodes
      are marked dirty before writeback starts working the blockdev mapping,
      so all the inode blocks are efficiently written back.
      
      The patch removes try_to_writeback_unused_inodes(), which became
      unreferenced in vm-writeback.patch.
      
      The patch has a tweak in ext2_put_inode() to prevent ext2 from
      incorrectly droppping its preallocation window in response to a random
      iput().
      
      
      Generally, many-small-file writeout is a lot faster than 2.5.7 (which
      is linux-before-I-futzed-with-it).  The workload which was optimised was
      
      	tar xfz /nfs/mountpoint/linux-2.4.18.tar.gz ; sync
      
      on mem=128M and mem=2048M.
      
      With these patches, 2.5.15 is completing in about 2/3 of the time of
      2.5.7.  But it is only a shade faster than 2.4.19-pre7.  Why is 2.5.7
      so much slower than 2.4.19?  Not sure yet.
      
      Heavy dbench loads (dbench 32 on mem=128M) are slightly faster than
      2.5.7 and significantly slower than 2.4.19.  It appears that the cause
      is poor read throughput at the later stages of the run.  Because there
      are background writeback threads operating at the same time.
      
      The 2.4.19-pre8 write scheduling manages to stop writeback during the
      latter stages of the dbench run in a way which I haven't been able to
      sanely emulate yet.  It may not be desirable to do this anyway - it's
      optimising for the case where the files are about to be deleted.  But
      it would be good to find a way of "pausing" the writeback for a few
      seconds to allow readers to get an interval of decent bandwidth.
      
      tiobench throughput is basically the same across all recent kernels.
      CPU load on writes is down maybe 30% in 2.5.15.
      799391cc
    • Andrew Morton's avatar
      [PATCH] ext2: preread inode backing blocks · a9f525e6
      Andrew Morton authored
      When ext2 creates a new inode, perform an asynchronous preread against
      its backing block.
      
      Without this patch, many-file writeout gets stalled by having to read
      many individual inode table blocks in the middle of writeback.
      
      It's worth about a 20% gain in writeback bandwidth for the many-file
      writeback case.
      
      ext3 already reads the inode's backing block in
      ext3_new_inode->ext3_mark_inode_dirty, so no change is needed there.
      
      A backport to 2.4 would make sense.
      a9f525e6
    • Andrew Morton's avatar
      [PATCH] writeback tuning · acb5f6f9
      Andrew Morton authored
      Tune up the VM-based writeback a bit.
      
      - Always use the multipage clustered-writeback function from within
        shrink_cache(), even if the page's mapping has a NULL ->vm_writeback().  So
        clustered writeback is turned on for all address_spaces, not just ext2.
      
        Subtle effect of this change: it is now the case that *all* writeback
        proceeds along the mapping->dirty_pages list.  The orderedness of the page
        LRUs no longer has an impact on disk scheduling.  So we only have one list
        to keep well-sorted rather than two, and churning pages around on the LRU
        will no longer damage write bandwidth - it's all up to the filesystem.
      
      - Decrease the clustered writeback from 1024 pages(!) to 32 pages.
      
        (1024 was a leftover from when this code was always dispatching writeback
        to a pdflush thread).
      
      - Fix wakeup_bdflush() so that it actually does write something (duh).
      
        do_wp_page() needs to call balance_dirty_pages_ratelimited(), so we
        throttle mmap page-dirtiers in the same way as write(2) page-dirtiers.
        This may make wakeup_bdflush() obsolete, but it doesn't hurt.
      
      - Converts generic_vm_writeback() to directly call ->writeback_mapping(),
        rather that going through writeback_single_inode().  This prevents memory
        allocators from blocking on the inode's I_LOCK.  But it does mean that two
        processes can be writing pages from the same mapping at the same time.  If
        filesystems care about this (for layout reasons) then they should serialise
        in their ->writeback_mapping a_op.
      
        This means that memory-allocators will writeback only pages, not pages
        and inodes.  There are no locks in that writeback path (except for request
        queue exhaustion).  Reduces memory allocation latency.
      
      - Implement new background_writeback function, which when kicked off
        will perform writeback until dirty memory falls below the background
        threshold.
      
      - Put written-back pages onto the remote end of the page LRU.  It
        does this in the slow-and-stupid way at present.  pagemap_lru_lock
        stress-relief is planned...
      
      - Remove the funny writeback_unused_inodes() stuff from prune_icache().
        Writeback from wakeup_bdflush() and the `kupdate' function now just
        naturally cleanses the oldest inodes so we don't need to do anything
        there.
      
      - Dirty memory balancing is still using magic numbers: "after you
        dirtied your 1,000th page, go write 1,500".  Obviously, this needs
        more work.
      acb5f6f9
    • Andrew Morton's avatar
      [PATCH] pdflush exclusion · 17a74e88
      Andrew Morton authored
      Use the pdflush exclusion infrastructure to ensure that only one
      pdlfush thread is ever performing writeback against a particular
      request_queue.
      
      This works rather well.  It requires a lot of activity against a lot of
      disks to cause more pdflush threads to start up.  Possibly the
      thread-creation logic is a little weak: it starts more threads when a
      pdflush thread goes back to sleep.  It may be better to start new
      threads within pdlfush_operation().
      
      All non-request_queue-backed address_spaces share the global
      default_backing_dev_info structure.  So at present only a single
      pdflush instance will be available for background writeback of *all*
      NFS filesystems (for example).
      
      If there is benefit in concurrent background writeback for multiple NFS
      mounts then NFS would need to create per-mount backing_dev_info
      structures and install those into new inode's address_spaces in some
      manner.
      17a74e88
    • Andrew Morton's avatar
      [PATCH] pdflush exclusion infrastructure · 1f6acea0
      Andrew Morton authored
      Collision avoidance for pdflush threads.
      
      Turns the request_queue-based `unsigned long ra_pages' into a structure
      which contains ra_pages as well as a longword.
      
      That longword is used to record the fact that a pdflush thread is
      currently writing something back against this request_queue.
      
      Avoids the situation where several pdflush threads are sleeping on the
      same request_queue.
      
      This patch provides only the infrastructure for the pdflush exclusion.
      This infrastructure gets used in pdflush-single.patch
      1f6acea0
    • Andrew Morton's avatar
      [PATCH] dirty inode management · 610c5ab8
      Andrew Morton authored
      Fix the "race with umount" in __sync_list().  __sync_list() no longer
      puts inodes onto a local list while writing them out.
      
      The super_block.sb_dirty list is kept time-ordered.  Mappings which
      have the "oldest" ->dirtied_when are kept at sb->s_dirty.prev.
      
      So the time-based writeback (kupdate) can just bale out when it
      encounters a not-old-enough mapping, rather than walking the entire
      list.
      
      dirtied_when is set on the *first* dirtying of a mapping.  So once the
      mapping is marked dirty it strictly retains its place on s_dirty until
      it reaches the oldest end and is written out.  So frequently-dirtied
      mappings don't stay dirty at the head of the list for all time.
      
      That local inode list was there for livelock avoidance.  Livelock is
      instead avoided by looking at each mapping's ->dirtied_when.  If we
      encounter one which was dirtied after this invokation of __sync_list(),
      then just bale out - the sync functions are only required to write out
      data which was dirty at the time when they were called.
      
      Keeping the s_dirty list in time-order is the right thing to do anyway
      - so all the various writeback callers always work against the oldest
      data.
      610c5ab8
    • Andrew Morton's avatar
      [PATCH] larger b_size, and misc fixlets · 2d8f24d0
      Andrew Morton authored
      Miscellany.
      
      - make the printk in buffer_io_error() sector_t-aware.
      
      - Some buffer.c cleanups from AntonA: remove a couple of !uptodate
        checks, and set a new buffer's b_blocknr to -1 in a more sensible
        place.
      
      - Make buffer_head.b_size a 32-bit quantity.  Needed for 64k pagesize
        on ia64.  Does not increase sizeof(struct buffer_head).
      2d8f24d0
    • Andrew Morton's avatar
      [PATCH] reiserfs locking fix · 943acef9
      Andrew Morton authored
      reiserfs is using b_inode_buffers and fsync_buffers_list() for
      attaching dependent buffers to its journal.  For writeout prior to
      commit.
      
      This worked OK when a global lock was used everywhere, but the locking
      is currently incorrect - try_to_free_buffers() is taking a different
      lock when detaching buffers from their "foreign" inode.  So list_head
      corruption could occur on SMP.
      
      The patch implements a reiserfs_releasepage() which holds the
      journal-wide buffer lock while it runs try_to_free_buffers(), so all
      those list_heads are protected.  The lock is held across the
      try_to_free_buffers() call as well, so nobody will attach one of this
      page's buffers to a list while try_to_free_buffers() is running.
      943acef9
    • Andrew Morton's avatar
      [PATCH] fix dirty page management · 0f9268b8
      Andrew Morton authored
      This fixes a bug in ext3 - when ext3 decides that it wants to fail its
      writepage(), it is running SetPageDirty().  But ->writepage has just put
      the page on ->clean_pages().  The page ends up dirty, on ->clean_pages
      and the normal writeback paths don't know about it any more.
      
      So run set_page_dirty() instead, to place the page back on the dirty
      list.
      
      And in move_from_swap_cache(), shuffle the page across to ->dirty_pages
      so that it's eligible for writeout.  ___add_to_page_cache() forgets to
      look at the page state when deciding which list to attach it to.
      
      All SetPageDirty() callers otherwise look OK.
      0f9268b8
    • Andrew Morton's avatar
      [PATCH] i_dirty_buffers locking fix · 43152186
      Andrew Morton authored
      This fixes a race between try_to_free_buffers' call to
      __remove_inode_queue() and other users of b_inode_buffers
      (fsync_inode_buffers and mark_buffer_dirty_inode()).  They are
      presently taking different locks.
      
      The patch relocates and redefines and clarifies(?) the role of
      inode.i_dirty_buffers.
      
      The 2.4 definition of i_dirty_buffers is "a list of random buffers
      which is protected by a kernel-wide lock".  This definition needs to be
      narrowed in the 2.5 context.  It is now
      
      "a list of buffers from a different mapping, protected by a lock within
      that mapping".  This list of buffers is specifically for fsync().
      
      As this is a "data plane" operation, all the structures have been moved
      out of the inode and into the address_space.  So address_space now has:
      
      list_head private_list;
      
           A list, available to the address_space for any purpose.  If
           that address_space chooses to use the helper functions
           mark_buffer_dirty_inode and sync_mapping_buffers() then this list
           will contain buffer_heads, attached via
           buffer_head.b_assoc_buffers.
      
           If the address_space does not call those helper functions
           then the list is free for other usage.  The only requirement is
           that the list be list_empty() at destroy_inode() time.
      
           At least, this is the objective.  At present,
           generic_file_write() will call generic_osync_inode(), which
           expects that list to contain buffer_heads.  So private_list isn't
           useful for anything else yet.
      
      spinlock_t private_lock;
      
           A spinlock, available to the address_space.
      
           If the address_space is using try_to_free_buffers(),
           mark_inode_dirty_buffers() and fsync_inode_buffers() then this
           lock is used to protect the private_list of *other* mappings which
           have listed buffers from *this* mapping onto themselves.
      
           That is: for buffer_heads, mapping_A->private_lock does not
           protect mapping_A->private_list!  It protects the b_assoc_buffers
           list from buffers which are backed by mapping_A and it protects
           mapping_B->private_list, mapping_C->private_list, ...
      
           So what we have here is a cross-mapping association.  S_ISREG
           mappings maintain a list of buffers from the blockdev's
           address_space which they need to know about for a successful
           fsync().  The locking follows the buffers: the lock in in the
           blockdev's mapping, not in the S_ISREG file's mapping.
      
           For address_spaces which use try_to_free_buffers,
           private_lock is also (and quite unrelatedly) used for protection
           of the buffer ring at page->private.  Exclusion between
           try_to_free_buffers(), __get_hash_table() and
           __set_page_dirty_buffers().  This is in fact its major use.
      
      address_space *assoc_mapping
      
          Sigh.  This is the address of the mapping which backs the
          buffers which are attached to private_list.  It's here so that
          generic_osync_inode() can locate the lock which protects this
          mapping's private_list.  Will probably go away.
      
      
      A consequence of all the above is that:
      
          a) All the buffers at a mapping_A's ->private_list must come
             from the same mapping, mapping_B.  There is no requirement that
             mapping_B be a blockdev mapping, but that's how it's used.
      
             There is a BUG() check in mark_buffer_dirty_inode() for this.
      
          b) blockdev mappings never have any buffers on ->private_list.
             It just never happens, and doesn't make a lot of sense.
      
      reiserfs is using b_inode_buffers for attaching dependent buffers to its
      journal and that caused a few problems.  Fixed in reiserfs_releasepage.patch
      43152186
    • Andrew Morton's avatar
      [PATCH] check for dirtying of non-uptodate buffers · 6b9f3b41
      Andrew Morton authored
      - Add a debug check to catch people who are marking non-uptodate
        buffers as dirty.
      
        This is either a source of data corruption, or sloppy programming.
      
      - Fix sloppy programming in ext3 ;)
      6b9f3b41
    • Andrew Morton's avatar
      [PATCH] reduce lock contention in do_pagecache_readahead · cd016d80
      Andrew Morton authored
      Anton Blanchard has a workload (the SDET benchmark) which is showing some
      moderate lock contention in do_pagecache_readahead().
      
      Seems that SDET has many threads performing seeky reads against a
      cached file.  The average number of pagecache probes in a single
      do_pagecache_readahead() is six, which seems reasonable.
      
      The patch (from Anton) flips the locking around to optimise for the
      fast case (page was present).  So the kernel takes the lock less often,
      and does more work once it has been acquired.
      cd016d80
    • Arnaldo Carvalho de Melo's avatar
      - sound/{core,pci}/*.c · f5737b71
      Arnaldo Carvalho de Melo authored
      	- fix copy_{to,from}_user error handling (thanks to Rusty for pointing this out)
      f5737b71
    • Linus Torvalds's avatar
      Merge http://linux-isdn.bkbits.net/linux-2.5.make · a252cfb4
      Linus Torvalds authored
      into home.transmeta.com:/home/torvalds/v2.5/linux
      a252cfb4
    • Kai Germaschewski's avatar
      kbuild: Use $(CURDIR) · 8f3ee280
      Kai Germaschewski authored
      Not a big change, but make provides the current directory,
      so why not use it ;-)
      8f3ee280
    • Kai Germaschewski's avatar
      kbuild: Suppress printing of '$(MAKE) -C command' line · 8202c057
      Kai Germaschewski authored
      Don't print the actual command to call make in a subdir, make will
      print 'Entering directory <foo>' anyway, so we don't lose that
      information.
      8202c057
    • Kai Germaschewski's avatar
      Small fix for net/irda/Makefile · 56de0f3c
      Kai Germaschewski authored
      This Makefile would add irlan/irlan.o to $(obj-m) when selected as
      modular, which is wrong. The module will get compiled just fine after
      descending into that subdirectory anyway (whereas in the current
      directory we have no idea how to build it).
      56de0f3c
    • Kai Germaschewski's avatar
      kbuild: Fix object-specific CFLAGS_foo.o · 18a8b891
      Kai Germaschewski authored
      Make CFLAGS_foo.o work also when generating preprocessed (.i) and
      assembler (.s) files.
        
      Same for AFLAGS_foo.o.
      18a8b891
    • Kai Germaschewski's avatar
      Merge http://linux-isdn.bkbits.net/linux-2.5.make · d852a144
      Kai Germaschewski authored
      into tp1.ruhr-uni-bochum.de:/home/kai/kernel/v2.5/linux-2.5.make
      d852a144
    • Linus Torvalds's avatar
      Merge http://kernel-acme.bkbits.net:8080/usb-copy_tofrom_user-2.5 · e1b37299
      Linus Torvalds authored
      into home.transmeta.com:/home/torvalds/v2.5/linux
      e1b37299
    • Linus Torvalds's avatar
      Merge http://kernel-acme.bkbits.net:8080/isdn-copy_tofrom_user-2.5 · 96f1f1d5
      Linus Torvalds authored
      into home.transmeta.com:/home/torvalds/v2.5/linux
      96f1f1d5
    • Arnaldo Carvalho de Melo's avatar
      drivers/usr/*.c · a465121e
      Arnaldo Carvalho de Melo authored
      	- fix copy_{to,from}_user error handling (thanks to Rusty for pointing this out)
      a465121e
    • Arnaldo Carvalho de Melo's avatar
      drivers/isdn/*.c · 7ccde684
      Arnaldo Carvalho de Melo authored
      	- fix copy_{to,from}_user error handling (thanks to Rusty for pointing this out)
      7ccde684
  2. 18 May, 2002 3 commits
  3. 19 May, 2002 1 commit
  4. 18 May, 2002 11 commits