page frame to save memory.

compressed page, copy the contents from the uncompressed page if necessary.

and update the comments.

buf_pool->page_hash and buf_pool->LRU before releasing buf_pool->mutex.

buf_page_init_for_read(), buf_page_create(): Allocate the compressed
page after the block has been added to the buffer pool.  Document the
reason for this.

when calling btr_search_drop_page_hash_index() and uninitialized after that.

buf_page_init(): Declare block->frame valid only in the system tablespace.

trx_sysf_create(): Declare the rest of the page valid, although it is
uninitialized.

buf_buddy_relocate(): Document that src may have been split and some of
it may be in buf_pool->zip_free[j] for some j<i, thus mach_read_from_4()
may be reading from free memory.  Check buffer pages only for addressability,
not for being completely initialized.  Ensure that block descriptors are
completely initialized.

buf_buddy_remove_from_free(): Check prev->state and next->state in
UNIV_DEBUG && UNIV_DEBUG_VALGRIND builds.

buf_buddy_free_low(): Flag the entire block valid prior to invoking
buf_buddy_remove_from_free() in order to avoid a Valgrind warning about
the debug assertion on bpage->state.  Remove the Valgrind check for
buddy being completely allocated.  If it has been split to smaller blocks,
some of those blocks may be free.

We cannot clear the page with memset(), because the page number and
tablespace id have already been stamped on it.

buf_buddy_add_to_free() and buf_buddy_remove_from_free().
Remove some bogus Valgrind warnings.  Improve Valgrind instrumentation.

UNIV_MEM_FREE(): Declare a memory area free.
UNIV_MEM_ALLOC(): Declare a memory area allocated (but uninitialized).
UNIV_MEM_DESC(): Associate a memory area with a control block.
UNIV_MEM_UNDESC(): Unassociate a control block.

trx_sys_create_doublewrite_buf(): Clear the buffer with memset().

buf_page_init(): Add a bogus UNIV_MEM_VALID(block->frame) to silence
valid warnings about InnoDB data pages containing uninitialized data.

buf_LRU_get_free_only(): Add UNIV_MEM_ALLOC(block->frame).

buf_LRU_get_free_block(): Add UNIV_MEM_DESC(block->page.zip.data, block).

buf_LRU_free_block(): Add UNIV_MEM_DESC(b->zip.data, b) when allocating
a compressed-only control block for a compressed page.

buf_LRU_block_free_non_file_page(): Replace UNIV_MEM_INVALID() with
UNIV_MEM_FREE().

buf_LRU_block_remove_hashed_page(): Add UNIV_MEM_UNDESC(bpage) when
deallocating a compressed-only control block.  Add
UNIV_MEM_INVALID(block->frame).  (The frame should be flagged free
by buf_LRU_block_free_non_file_page() moments later.)

buf0buddy.c: Disable some extra checks in Valgrind-instrumented builds.
Add UNIV_MEM_VALID(), UNIV_MEM_INVALID(), UNIV_MEM_FREE(), UNIV_MEM_ALLOC()
as necessary.

buf_buddy_block_free(), buf_buddy_free_low(): Flag the freed bytes
uninitialized.

buf_page_init_for_read(), buf_buddy_relocate(): Do not refer to bpage
after invoking buf_relocate().

buf_buddy_relocate(): Flag src uninitialized.

buf_block_t* to buf_page_t*.  Handle compressed-only blocks.

buf_pool->page_hash corruption.

during the buf_zip_decompress() call.  Otherwise, the block may end
up being freed by another thread.  This bug was caught by the
page_zip_validate() check in buf_LRU_block_remove_hashed_page().

buf_page_init_for_read(): Protect the buf_zip_decompress() call with
an X-lock on the block.

page_zip_validate(): Move the page_is_comp() assertion after the
page header comparison.

objects in the free area.

compressed-only page, restart the scan of the LRU list, because
prev_bpage may have been relocated.

buf_LRU_block_remove_hashed_page(): Note that other compressed pages
or compressed-only blocks may be relocated when freeing a compressed
page or a compressed-only block descriptor.

dirty uncompressed blocks.  Move the page_zip_validate() call to
a more appropriate place, buf_LRU_block_remove_hashed_page().

buf_LRU_block_remove_hashed_page(): Allow bpage->oldest_modification != 0
for uncompressed pages if there is a compressed page that will be preserved.
Release the mutexes before calling buf_print() and buf_LRU_print().

page_zip_validate(): Remove the assertion containing the
buf_frame_get_page_zip() call.  We might already be holding buf_pool->mutex.

successful buf_LRU_free_block().

buf_LRU_free_block(): Note that buf_pool->mutex may be temporarily released.

buf_flush_batch(): Remove the local variable "found".

the buffer pool.

buf_LRU_free_block(): When preserving the compressed page, compute the
checksum.  Also assert page_zip_validate().

buf_zip_decompress(): Add parameter "check" for enabling checksum tests.
Before decompressing a compressed-only page from the buffer pool, verify
the compressed page checksum.

to the buffer pool while we were not holding buf_pool->mutex.  If it was,
do not attempt to preserve the compressed page.

page_zip_malloc(): Replace ut_malloc(...) with mem_heap_alloc(opaque, ...).

page_zip_free(): Dummy function (cannot deallocate from InnoDB memory
heaps, and zlib seems to defer deallocation to the very end anyway).

page_zip_compress(): Create a big enough heap for the needs of zlib.
Replace deflateInit() with deflateInit2().

page_zip_decompress(): Create a big enough heap for the needs of zlib.
Replace inflateInit() with inflateInit2().

Remove the unused parameter init_block.

mem_heap_fast_create(): Remove.

struct mem_block_info_struct: Remove the field init_block.

buf_page_get_gen(): Note that buf_read_page() may uncompress
a compressed-only page.

buf_page_create(): Test buf_page_in_file() instead of BUF_BLOCK_FILE_PAGE.

buffer pool in compressed form only.

buf_page_peek_block(): Remove.

mutex_enter_fast_func: Remove.

and add compressed-only pages to buf_pool->page_hash.

BUF_POOL_ZIP_FOLD(), BUF_POOL_ZIP_FOLD_PTR(), BUF_POOL_ZIP_FOLD_BPAGE():
Macros for computing buf_pool->zip_hash fold values.  Make use of these
in buf0buddy.c.

buf0buddy.c: Replace some ptr == ut_align_down(ptr, ...) in assertions with
!ut_align_offset(ptr, ...).

to BUF_BLOCK_ZIP_DIRTY (discarding the uncompressed page corresponding
to a modified compressed page that has not been flushed to disk).

buf_page_can_relocate(): New function, modelled after
buf_flush_ready_for_replace().

buf_LRU_free_block(): Allow the transition to BUF_BLOCK_ZIP_DIRTY.

buf_flush_insert_into_flush_list(): Make the prototype public.

buf_buddy_relocate(): Remove an unnecessary switch statement.
Use buf_page_can_relocate() instead of buf_flush_ready_for_replace().

buf_page_peek(): Made UNIV_INLINE.

Document UNIV_ZIP_DEBUG.

Improve diagnostics.

buf_buddy_relocate(): Do not assume all small blocks to contain only one
buf_page_t object.  Require an exact size match, as in the case of
compressed pages.

buf_relocate(): Relocate buf_pool->LRU_old if needed.
Validate the LRU list in debug builds.

buf_LRU_block_remove_hashed_page(): Do not overwrite FIL_PAGE_OFFSET
or FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID.  The memory will be invalidated
in debug builds of buf_buddy_free().

buf0buddy.c: Add assertions for not holding buf_pool->zip_mutex.
The calling thread should not be holding any block->mutex, but it might
be too time-consuming to assert against that, even #ifdef UNIV_SYNC_DEBUG.

release any block mutexes but hold the buf_pool->mutex.

There is something wrong with the management of compressed-only blocks
(BUF_BLOCK_ZIP_PAGE).  To disable the creation of such blocks, set zip=TRUE
in buf_LRU_block_remove_hashed_page().

buf_LRU_block_remove_hashed_page(): Release buf_pool->zip_mutex when
freeing a compressed-only page and its control block, with buf_buddy_free().
Adapt callers.

buf_LRU_block_free_hashed_page(): Change the parameter type from buf_page_t*
to buf_block_t*.

buf_LRU_free_block(): Move below the definition of buf_LRU_add_block_low().
Allocate block descriptor for compressed-only blocks.

buf_LRU_block_free_non_file_page(): Replace ut_free() with buf_buddy_free().

buf_zip_decompress(): New function, split from buf_page_io_complete().

buf_page_init_for_read(): Do not allocate the compressed page until it is
really needed, to avoid the overhead of the buddy allocator.  Decompress
compressed-only blocks that are needed again.

buf_page_create(): Do not allocate the compressed page until it is
really needed, to avoid the overhead of the buddy allocator.

buf_validate(): Replace some equality tests on the lengths of the LRU
list and the flush lists with greater-or-equal tests, since the counted
numbers do not include control blocks for compressed-only pages.

to all fold functions.

must_flush_log, and remove warning about lsn being possibly uninitialized.

also check buf_page_in_file().  This error was introduced in r1082.