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To reduce amount of damage caused by single bad block, we limit number
of inodes sharing an xattr block to 1024. Thus there can be more xattr
blocks with the same contents when there are lots of files with the same
extended attributes. These xattr blocks naturally result in hash
collisions and can form long hash chains and we unnecessarily check each
such block only to find out we cannot use it because it is already
shared by too many inodes.
Add a reusable flag to cache entries which is cleared when a cache entry
has reached its maximum refcount. Cache entries which are not marked
reusable are skipped by mb_cache_entry_find_{first,next}. This
significantly speeds up mbcache when there are many same xattr blocks.
For example for xattr-bench with 5 values and each process handling
20000 files, the run for 64 processes is 25x faster with this patch.
Even for 8 processes the speedup is almost 3x. We have also verified
that for situations where there is only one xattr block of each kind,
the patch doesn't have a measurable cost.
[JK: Remove handling of setting the same value since it is not needed
anymore, check for races in e_reusable setting, improve changelog,
add measurements]
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Get rid of field _e_hash_list_head in cache entries and add bit field
e_referenced instead.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Since old mbcache code is gone, let's rename new code to mbcache since
number 2 is now meaningless. This is just a mechanical replacement.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Both ext2 and ext4 are now converted to mbcache2. Remove the old mbcache
code.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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This patch changes each mb_cache's both block and index hash chains to
use a hlist_bl_node, which contains a built-in lock. This is the
first step in decoupling of locks serializing accesses to mb_cache
global data and each mb_cache_entry local data.
Signed-off-by: T. Makphaibulchoke <tmac@hp.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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EXT2_XATTR_DEBUG
When I enable EXT2_XATTR_DEBUG in fs/ext2/xattr.c I get a build error stating
the following:
CC fs/ext2/xattr.o
fs/ext2/xattr.c: In function 'ext2_xattr_cache_insert':
fs/ext2/xattr.c:841: error: dereferencing pointer to incomplete type
fs/ext2/xattr.c:846: error: dereferencing pointer to incomplete type
make[2]: *** [fs/ext2/xattr.o] Error 1
make[1]: *** [fs/ext2] Error 2
make: *** [fs] Error 2
These lines reference ext2_xattr_cache->c_entry_count which is defined
in struct mb_cache. struct mb_cache is currently only defined in fs/mbcache.c.
Moving struct mb_cache definition to include/linux/mbcache.h to resolve the
issue.
Signed-off-by: Josh Hunt <johunt@akamai.com>
Signed-off-by: Jan Kara <jack@suse.cz>
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The mbcache code was written to support a variable number of indexes,
but all the existing users use exactly one index. Simplify to code to
support only that case.
There are also no users of the cache entry free operation, and none of
the users keep extra data in cache entries. Remove those features as
well.
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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mb_cache_entry_alloc() was allocating cache entries with GFP_KERNEL. But
filesystems are calling this function while holding xattr_sem so possible
recursion into the fs violates locking ordering of xattr_sem and transaction
start / i_mutex for ext2-4. Change mb_cache_entry_alloc() so that filesystems
can specify desired gfp mask and use GFP_NOFS from all of them.
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Dave Jones <davej@redhat.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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- ->releasepage() annotated (s/int/gfp_t), instances updated
- missing gfp_t in fs/* added
- fixed misannotation from the original sweep caught by bitwise checks:
XFS used __nocast both for gfp_t and for flags used by XFS allocator.
The latter left with unsigned int __nocast; we might want to add a
different type for those but for now let's leave them alone. That,
BTW, is a case when __nocast use had been actively confusing - it had
been used in the same code for two different and similar types, with
no way to catch misuses. Switch of gfp_t to bitwise had caught that
immediately...
One tricky bit is left alone to be dealt with later - mapping->flags is
a mix of gfp_t and error indications. Left alone for now.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The cache parameter to mb_cache_shrink isn't used. We may as well remove
it.
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Andrew Tridgell and Stephen C. Tweedie have reported two different Oopses
caused by a race condition in the mbcache, which is responsible for
extended attribute sharing in ext2 and ext3. Stephen tracked down the bug;
I did the fix.
Explanation:
The mbcache caches the locations and content hashes of xattr blocks. There
are two access strategies: [1] xattr block disposal via
mb_cache_entry_get(), [2] xattr block reuse (sharing) via
mb_cache_entry_find_{first,next}(). There is no locking between the two
methods, so between one mb_cache_entry_find_x and the next, a
mb_cache_entry_get might come in, unhash the cache entry, and change the
journaling state of the xattr buffer. Subsequently, two things can happen:
[a] the next mb_cache_entry_find_x may try to follow the mbcache hash chain
starting from the entry that has become unhashed, which now is a stale
pointer, [b] the block may have become deallocated, and then we try to
reuse it.
Fix this by converting the mbcache into a readers-writer style lock, and
protect all block accesses in ext2/ext3 by the mbcache entry lock. This
ensures that destroying blocks is an exclusive operation that may not
overlap xattr block reuse, while allowing multiple "re-users". Write
access to the xattr block's buffer is protected by the buffer lock.
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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There is no need to export struct mb_cache outside mbcache.c. Move struct
mb_cache to fs/mbcache.c and remove the superfluous struct
mb_cache_entry_index declaration.
Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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mb_cache_entry_takeout and mb_cache_entry_dup are totally unused.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Patch from Andreas Gruenbacher <agruen@suse.de>
Add a gfp_mask parameter to the free() callback so that the callback can
safely do I/O, etc. The free callback can now also fail. This will be
needed by reiserfs.
The order of entries on the cache entry lru is reversed so that
list_for_each_safe() can be used. Several helper functions that don't
make the code any better are removed. Finally, a couple of cosmetic
things.
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(now uses struct block_device * to index devices, and uses hash.h for hash function)
This patch creates a meta block cache which is utilized by the ext3 and
ext2 extended attribute patch (patches 2 and 3, respectively). This
cache allows directory blocks to be indexed by multiple keys. In the
case of the extended attribute patches, it is used to look up blocks by
both the block number and by the hash of the extended attributes. This
is extremely important to allow the sharing of acl's when stored as
extended attributes. Otherwise every single file would require its own,
separate, one block overhead to store then ACL, even though there might
be a large number of files that have the same ACL.
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