linux-toradex.git/fs/mbcache.c, branch v4.17-rc1

mbcache: make sure c_entry_count is not decremented past zero

2018-01-10T04:57:52+00:00

Signed-off-by: Jiang Biao 
Signed-off-by: Theodore Ts'o 
CC: Eric Biggers 
CC: Andrew Morton 
CC: Jan Kara

mbcache: revert "fs/mbcache.c: make count_objects() more robust"

2018-01-07T21:35:20+00:00

This reverts commit d5dabd633922ac5ee5bcc67748f7defb8b211469.

This patch did absolutely nothing, because ->c_entry_count is unsigned.

In addition if there is a bug in how mbcache maintains its entry count,
it needs to be fixed, not just hacked around.  (There is no obvious bug,
though.)

Cc: Jan Kara 
Cc: Jiang Biao 
Signed-off-by: Eric Biggers 
Signed-off-by: Theodore Ts'o

mbcache: initialize entry->e_referenced in mb_cache_entry_create()

2018-01-07T21:22:35+00:00

KMSAN reported use of uninitialized |entry->e_referenced| in a condition
in mb_cache_shrink():

==================================================================
BUG: KMSAN: use of uninitialized memory in mb_cache_shrink+0x3b4/0xc50 fs/mbcache.c:287
CPU: 2 PID: 816 Comm: kswapd1 Not tainted 4.11.0-rc5+ #2877
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x172/0x1c0 lib/dump_stack.c:52
 kmsan_report+0x12a/0x180 mm/kmsan/kmsan.c:927
 __msan_warning_32+0x61/0xb0 mm/kmsan/kmsan_instr.c:469
 mb_cache_shrink+0x3b4/0xc50 fs/mbcache.c:287
 mb_cache_scan+0x67/0x80 fs/mbcache.c:321
 do_shrink_slab mm/vmscan.c:397 [inline]
 shrink_slab+0xc3d/0x12d0 mm/vmscan.c:500
 shrink_node+0x208f/0x2fd0 mm/vmscan.c:2603
 kswapd_shrink_node mm/vmscan.c:3172 [inline]
 balance_pgdat mm/vmscan.c:3289 [inline]
 kswapd+0x160f/0x2850 mm/vmscan.c:3478
 kthread+0x46c/0x5f0 kernel/kthread.c:230
 ret_from_fork+0x29/0x40 arch/x86/entry/entry_64.S:430
chained origin:
 save_stack_trace+0x37/0x40 arch/x86/kernel/stacktrace.c:59
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:302 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:317 [inline]
 kmsan_internal_chain_origin+0x12a/0x1f0 mm/kmsan/kmsan.c:547
 __msan_store_shadow_origin_1+0xac/0x110 mm/kmsan/kmsan_instr.c:257
 mb_cache_entry_create+0x3b3/0xc60 fs/mbcache.c:95
 ext4_xattr_cache_insert fs/ext4/xattr.c:1647 [inline]
 ext4_xattr_block_set+0x4c82/0x5530 fs/ext4/xattr.c:1022
 ext4_xattr_set_handle+0x1332/0x20a0 fs/ext4/xattr.c:1252
 ext4_xattr_set+0x4d2/0x680 fs/ext4/xattr.c:1306
 ext4_xattr_trusted_set+0x8d/0xa0 fs/ext4/xattr_trusted.c:36
 __vfs_setxattr+0x703/0x790 fs/xattr.c:149
 __vfs_setxattr_noperm+0x27a/0x6f0 fs/xattr.c:180
 vfs_setxattr fs/xattr.c:223 [inline]
 setxattr+0x6ae/0x790 fs/xattr.c:449
 path_setxattr+0x1eb/0x380 fs/xattr.c:468
 SYSC_lsetxattr+0x8d/0xb0 fs/xattr.c:490
 SyS_lsetxattr+0x77/0xa0 fs/xattr.c:486
 entry_SYSCALL_64_fastpath+0x13/0x94
origin:
 save_stack_trace+0x37/0x40 arch/x86/kernel/stacktrace.c:59
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:302 [inline]
 kmsan_internal_poison_shadow+0xb1/0x1a0 mm/kmsan/kmsan.c:198
 kmsan_kmalloc+0x7f/0xe0 mm/kmsan/kmsan.c:337
 kmem_cache_alloc+0x1c2/0x1e0 mm/slub.c:2766
 mb_cache_entry_create+0x283/0xc60 fs/mbcache.c:86
 ext4_xattr_cache_insert fs/ext4/xattr.c:1647 [inline]
 ext4_xattr_block_set+0x4c82/0x5530 fs/ext4/xattr.c:1022
 ext4_xattr_set_handle+0x1332/0x20a0 fs/ext4/xattr.c:1252
 ext4_xattr_set+0x4d2/0x680 fs/ext4/xattr.c:1306
 ext4_xattr_trusted_set+0x8d/0xa0 fs/ext4/xattr_trusted.c:36
 __vfs_setxattr+0x703/0x790 fs/xattr.c:149
 __vfs_setxattr_noperm+0x27a/0x6f0 fs/xattr.c:180
 vfs_setxattr fs/xattr.c:223 [inline]
 setxattr+0x6ae/0x790 fs/xattr.c:449
 path_setxattr+0x1eb/0x380 fs/xattr.c:468
 SYSC_lsetxattr+0x8d/0xb0 fs/xattr.c:490
 SyS_lsetxattr+0x77/0xa0 fs/xattr.c:486
 entry_SYSCALL_64_fastpath+0x13/0x94
==================================================================

Signed-off-by: Alexander Potapenko 
Signed-off-by: Eric Biggers 
Cc: stable@vger.kernel.org # v4.6

fs/mbcache.c: make count_objects() more robust

2017-11-30T02:40:43+00:00

When running ltp stress test for 7*24 hours, vmscan occasionally emits
the following warning continuously:

  mb_cache_scan+0x0/0x3f0 negative objects to delete
  nr=-9232265467809300450
  ...

Tracing shows the freeable(mb_cache_count returns) is -1, which causes
the continuous accumulation and overflow of total_scan.

This patch makes sure that mb_cache_count() cannot return a negative
value, which makes the mbcache shrinker more robust.

Link: http://lkml.kernel.org/r/1511753419-52328-1-git-send-email-jiang.biao2@zte.com.cn
Signed-off-by: Jiang Biao 
Cc: Al Viro 
Cc: Minchan Kim 
Cc: Michal Hocko 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ext4: xattr inode deduplication

2017-06-22T15:44:55+00:00

Ext4 now supports xattr values that are up to 64k in size (vfs limit).
Large xattr values are stored in external inodes each one holding a
single value. Once written the data blocks of these inodes are immutable.

The real world use cases are expected to have a lot of value duplication
such as inherited acls etc. To reduce data duplication on disk, this patch
implements a deduplicator that allows sharing of xattr inodes.

The deduplication is based on an in-memory hash lookup that is a best
effort sharing scheme. When a xattr inode is read from disk (i.e.
getxattr() call), its crc32c hash is added to a hash table. Before
creating a new xattr inode for a value being set, the hash table is
checked to see if an existing inode holds an identical value. If such an
inode is found, the ref count on that inode is incremented. On value
removal the ref count is decremented and if it reaches zero the inode is
deleted.

The quota charging for such inodes is manually managed. Every reference
holder is charged the full size as if there was no sharing happening.
This is consistent with how xattr blocks are also charged.

[ Fixed up journal credits calculation to handle inline data and the
  rare case where an shared xattr block can get freed when two thread
  race on breaking the xattr block sharing. --tytso ]

Signed-off-by: Tahsin Erdogan 
Signed-off-by: Theodore Ts'o

mbcache: make mbcache naming more generic

2017-06-22T14:29:53+00:00

Make names more generic so that mbcache usage is not limited to
block sharing. In a subsequent patch in the series
("ext4: xattr inode deduplication"), we start using the mbcache code
for sharing xattr inodes. With that patch, old mb_cache_entry.e_block
field could be holding either a block number or an inode number.

Signed-off-by: Tahsin Erdogan 
Signed-off-by: Theodore Ts'o

mbcache: document that "find" functions only return reusable entries

2016-12-03T20:55:01+00:00

mb_cache_entry_find_first() and mb_cache_entry_find_next() only return
cache entries with the 'e_reusable' bit set.  This should be documented.

Signed-off-by: Eric Biggers 
Signed-off-by: Theodore Ts'o 
Reviewed-by: Jan Kara

mbcache: use consistent type for entry count

2016-12-03T20:43:48+00:00

mbcache used several different types to represent the number of entries
in the cache.  For consistency within mbcache and with the shrinker API,
always use unsigned long.

This does not change behavior for current mbcache users (ext2 and ext4)
since they limit the entry count to a value which easily fits in an int.

Signed-off-by: Eric Biggers 
Signed-off-by: Theodore Ts'o 
Reviewed-by: Jan Kara

mbcache: remove unnecessary module_get/module_put

2016-12-03T20:38:29+00:00

When mbcache is built as a module, any modules that use it (ext2 and/or
ext4) will depend on its symbols directly, incrementing its reference
count.  Therefore, there is no need to do module_get/module_put.

Also note that since the module_get/module_put were in the mbcache
module itself, executing those lines of code was already dependent on
another reference to the mbcache module being held.

Signed-off-by: Eric Biggers 
Signed-off-by: Theodore Ts'o 
Reviewed-by: Jan Kara

mbcache: don't BUG() if entry cache cannot be allocated

2016-12-03T20:28:53+00:00

mbcache can be a module that is loaded long after startup, when someone
asks to mount an ext2 or ext4 filesystem.  Therefore it should not BUG()
if kmem_cache_create() fails, but rather just fail the module load.

Signed-off-by: Eric Biggers 
Signed-off-by: Theodore Ts'o 
Reviewed-by: Jan Kara