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55507ce361
linux/fs/btrfs
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Filipe Manana 55507ce361 Btrfs: fix race between writing free space cache and trimming 
Trimming is completely transactionless, and the way it operates consists
of hiding free space entries from a block group, perform the trim/discard
and then make the free space entries visible again.
Therefore while a free space entry is being trimmed, we can have free space
cache writing running in parallel (as part of a transaction commit) which
will miss the free space entry. This means that an unmount (or crash/reboot)
after that transaction commit and mount again before another transaction
starts/commits after the discard finishes, we will have some free space
that won't be used again unless the free space cache is rebuilt. After the
unmount, fsck (btrfsck, btrfs check) reports the issue like the following
example:

        *** fsck.btrfs output ***
        checking extents
        checking free space cache
        There is no free space entry for 521764864-521781248
        There is no free space entry for 521764864-1103101952
        cache appears valid but isnt 29360128
        Checking filesystem on /dev/sdc
        UUID: b4789e27-4774-4626-98e9-ae8dfbfb0fb5
        found 1235681286 bytes used err is -22
        (...)

Another issue caused by this race is a crash while writing bitmap entries
to the cache, because while the cache writeout task accesses the bitmaps,
the trim task can be concurrently modifying the bitmap or worse might
be freeing the bitmap. The later case results in the following crash:

[55650.804460] general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC
[55650.804835] Modules linked in: btrfs dm_flakey dm_mod crc32c_generic xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd fscache sunrpc loop parport_pc parport i2c_piix4 psmouse evdev pcspkr microcode processor i2ccore serio_raw thermal_sys button ext4 crc16 jbd2 mbcache sg sd_mod crc_t10dif sr_mod cdrom crct10dif_generic crct10dif_common ata_generic virtio_scsi floppy ata_piix libata virtio_pci virtio_ring virtio scsi_mod e1000 [last unloaded: btrfs]
[55650.806169] CPU: 1 PID: 31002 Comm: btrfs-transacti Tainted: G        W      3.17.0-rc5-btrfs-next-1+ #1
[55650.806493] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
[55650.806867] task: ffff8800b12f6410 ti: ffff880071538000 task.ti: ffff880071538000
[55650.807166] RIP: 0010:[<ffffffffa037cf45>]  [<ffffffffa037cf45>] write_bitmap_entries+0x65/0xbb [btrfs]
[55650.807514] RSP: 0018:ffff88007153bc30  EFLAGS: 00010246
[55650.807687] RAX: 000000005d1ec000 RBX: ffff8800a665df08 RCX: 0000000000000400
[55650.807885] RDX: ffff88005d1ec000 RSI: 6b6b6b6b6b6b6b6b RDI: ffff88005d1ec000
[55650.808017] RBP: ffff88007153bc58 R08: 00000000ddd51536 R09: 00000000000001e0
[55650.808017] R10: 0000000000000000 R11: 0000000000000037 R12: 6b6b6b6b6b6b6b6b
[55650.808017] R13: ffff88007153bca8 R14: 6b6b6b6b6b6b6b6b R15: ffff88007153bc98
[55650.808017] FS:  0000000000000000(0000) GS:ffff88023ec80000(0000) knlGS:0000000000000000
[55650.808017] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[55650.808017] CR2: 0000000002273b88 CR3: 00000000b18f6000 CR4: 00000000000006e0
[55650.808017] Stack:
[55650.808017]  ffff88020e834e00 ffff880172d68db0 0000000000000000 ffff88019257c800
[55650.808017]  ffff8801d42ea720 ffff88007153bd10 ffffffffa037d2fa ffff880224e99180
[55650.808017]  ffff8801469a6188 ffff880224e99140 ffff880172d68c50 00000003000000b7
[55650.808017] Call Trace:
[55650.808017]  [<ffffffffa037d2fa>] __btrfs_write_out_cache+0x1ea/0x37f [btrfs]
[55650.808017]  [<ffffffffa037d959>] btrfs_write_out_cache+0xa1/0xd8 [btrfs]
[55650.808017]  [<ffffffffa033936b>] btrfs_write_dirty_block_groups+0x4b5/0x505 [btrfs]
[55650.808017]  [<ffffffffa03aa98e>] commit_cowonly_roots+0x15e/0x1f7 [btrfs]
[55650.808017]  [<ffffffff813eb9c7>] ? _raw_spin_lock+0xe/0x10
[55650.808017]  [<ffffffffa0346e46>] btrfs_commit_transaction+0x411/0x882 [btrfs]
[55650.808017]  [<ffffffffa03432a4>] transaction_kthread+0xf2/0x1a4 [btrfs]
[55650.808017]  [<ffffffffa03431b2>] ? btrfs_cleanup_transaction+0x3d8/0x3d8 [btrfs]
[55650.808017]  [<ffffffff8105966b>] kthread+0xb7/0xbf
[55650.808017]  [<ffffffff810595b4>] ? __kthread_parkme+0x67/0x67
[55650.808017]  [<ffffffff813ebeac>] ret_from_fork+0x7c/0xb0
[55650.808017]  [<ffffffff810595b4>] ? __kthread_parkme+0x67/0x67
[55650.808017] Code: 4c 89 ef 8d 70 ff e8 d4 fc ff ff 41 8b 45 34 41 39 45 30 7d 5c 31 f6 4c 89 ef e8 80 f6 ff ff 49 8b 7d 00 4c 89 f6 b9 00 04 00 00 <f3> a5 4c 89 ef 41 8b 45 30 8d 70 ff e8 a3 fc ff ff 41 8b 45 34
[55650.808017] RIP  [<ffffffffa037cf45>] write_bitmap_entries+0x65/0xbb [btrfs]
[55650.808017]  RSP <ffff88007153bc30>
[55650.815725] ---[ end trace 1c032e96b149ff86 ]---

Fix this by serializing both tasks in such a way that cache writeout
doesn't wait for the trim/discard of free space entries to finish and
doesn't miss any free space entry.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
2014-12-02 18:35:09 -08:00
..
tests Btrfs: remove empty block groups automatically 2014-09-22 17:13:21 -07:00
acl.c btrfs: remove useless ACL check 2014-06-09 17:20:42 -07:00
async-thread.c btrfs: remove unlikely from NULL checks 2014-10-02 16:06:19 +02:00
async-thread.h Btrfs: implement repair function when direct read fails 2014-09-17 13:39:01 -07:00
backref.c btrfs: remove parameter blocksize from read_tree_block 2014-10-02 17:14:50 +02:00
backref.h Btrfs: make fiemap not blow when you have lots of snapshots 2014-09-17 13:38:24 -07:00
btrfs_inode.h Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2014-10-11 08:03:52 -04:00
check-integrity.c Btrfs: include vmalloc.h in check-integrity.c 2014-11-25 06:01:11 -08:00
check-integrity.h block: submit_bio_wait() conversions 2013-11-24 16:33:41 -07:00
compression.c Btrfs: don't ignore compressed bio write errors 2014-11-20 17:14:26 -08:00
compression.h btrfs: make static code static & remove dead code 2013-05-06 15:55:23 -04:00
ctree.c Btrfs: make xattr replace operations atomic 2014-11-20 17:20:07 -08:00
ctree.h Btrfs: fix race between fs trimming and block group remove/allocation 2014-12-02 18:35:09 -08:00
delayed-inode.c btrfs: kill the key type accessor helpers 2014-09-17 13:37:12 -07:00
delayed-inode.h Btrfs: introduce the delayed inode ref deletion for the single link inode 2014-01-28 13:20:09 -08:00
delayed-ref.c Btrfs: rework qgroup accounting 2014-06-09 17:20:48 -07:00
delayed-ref.h Btrfs: rework qgroup accounting 2014-06-09 17:20:48 -07:00
dev-replace.c btrfs: Fix a lockdep warning when running xfstest. 2014-11-25 05:55:38 -08:00
dev-replace.h
dir-item.c Btrfs: make xattr replace operations atomic 2014-11-20 17:20:07 -08:00
disk-io.c Btrfs: fix race between fs trimming and block group remove/allocation 2014-12-02 18:35:09 -08:00
disk-io.h Merge branch 'cleanup/blocksize-diet-part1' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux into for-linus 2014-10-04 09:57:14 -07:00
export.c btrfs: kill the key type accessor helpers 2014-09-17 13:37:12 -07:00
export.h
extent_io.c Btrfs: avoid premature -ENOMEM in clear_extent_bit() 2014-11-20 17:20:06 -08:00
extent_io.h Btrfs: set page and mapping error on compressed write failure 2014-11-20 17:14:25 -08:00
extent_map.c Btrfs: do not move em to modified list when unpinning 2014-11-21 11:59:54 -08:00
extent_map.h Btrfs: fix NULL pointer crash when running balance and scrub concurrently 2014-06-19 14:20:55 -07:00
extent-tree.c Btrfs: fix race between fs trimming and block group remove/allocation 2014-12-02 18:35:09 -08:00
file-item.c Btrfs: fix kfree on list_head in btrfs_lookup_csums_range error cleanup 2014-11-04 06:59:04 -08:00
file.c Btrfs: fix snapshot inconsistency after a file write followed by truncate 2014-11-25 07:41:23 -08:00
free-space-cache.c Btrfs: fix race between writing free space cache and trimming 2014-12-02 18:35:09 -08:00
free-space-cache.h Btrfs: fix race between writing free space cache and trimming 2014-12-02 18:35:09 -08:00
hash.c btrfs: LLVMLinux: Remove VLAIS 2014-10-14 10:51:22 +02:00
hash.h Btrfs: fix btrfs boot when compiled as built-in 2014-01-28 13:20:31 -08:00
inode-item.c btrfs: kill the key type accessor helpers 2014-09-17 13:37:12 -07:00
inode-map.c Btrfs: fix race between writing free space cache and trimming 2014-12-02 18:35:09 -08:00
inode-map.h
inode.c Btrfs: fix snapshot inconsistency after a file write followed by truncate 2014-11-25 07:41:23 -08:00
ioctl.c Btrfs: fix snapshot inconsistency after a file write followed by truncate 2014-11-25 07:41:23 -08:00
Kconfig Btrfs: fix btrfs boot when compiled as built-in 2014-01-28 13:20:31 -08:00
locking.c Btrfs: fix deadlocks with trylock on tree nodes 2014-06-19 14:19:55 -07:00
locking.h Btrfs: remove btrfs_try_spin_lock 2013-03-14 14:57:10 -04:00
lzo.c btrfs: use DIV_ROUND_UP instead of open-coded variants 2014-09-17 13:37:17 -07:00
Makefile Btrfs: add sanity tests for new qgroup accounting code 2014-06-09 17:20:49 -07:00
math.h
ordered-data.c Btrfs: collect only the necessary ordered extents on ranged fsync 2014-11-21 11:59:56 -08:00
ordered-data.h Btrfs: collect only the necessary ordered extents on ranged fsync 2014-11-21 11:59:56 -08:00
orphan.c btrfs: kill the key type accessor helpers 2014-09-17 13:37:12 -07:00
print-tree.c btrfs: remove parameter blocksize from read_tree_block 2014-10-02 17:14:50 +02:00
print-tree.h btrfs: make static code static & remove dead code 2013-05-06 15:55:23 -04:00
props.c Btrfs: add support for inode properties 2014-01-28 13:20:24 -08:00
props.h Btrfs: add support for inode properties 2014-01-28 13:20:24 -08:00
qgroup.c btrfs: move checks for DUMMY_ROOT into a helper 2014-10-02 17:30:33 +02:00
qgroup.h btrfs: qgroup: account shared subtrees during snapshot delete 2014-08-15 07:43:14 -07:00
raid56.c btrfs: use DIV_ROUND_UP instead of open-coded variants 2014-09-17 13:37:17 -07:00
raid56.h
rcu-string.h
reada.c btrfs: use nodesize everywhere, kill leafsize 2014-09-17 13:37:14 -07:00
relocation.c Merge branch 'cleanup/blocksize-diet-part1' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux into for-linus 2014-10-04 09:57:14 -07:00
root-tree.c Btrfs: use bitfield instead of integer data type for the some variants in btrfs_root 2014-06-09 17:20:40 -07:00
scrub.c btrfs: fix dead lock while running replace and defrag concurrently 2014-11-20 17:20:08 -08:00
send.c Btrfs: ensure send always works on roots without orphans 2014-11-25 07:41:23 -08:00
send.h btrfs: make static code static & remove dead code 2013-05-06 15:55:23 -04:00
struct-funcs.c
super.c Merge branch 'dev/pending-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux into for-linus 2014-11-25 05:45:30 -08:00
sysfs.c btrfs: move commit out of sysfs when changing label 2014-11-12 16:53:15 +01:00
sysfs.h btrfs: code optimize: BTRFS_ATTR_RW could set the mode 2014-09-17 13:37:59 -07:00
transaction.c Merge branch 'dev/pending-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux into for-linus 2014-11-25 05:45:30 -08:00
transaction.h Merge branch 'dev/pending-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux into for-linus 2014-11-25 05:45:30 -08:00
tree-defrag.c Btrfs: use bitfield instead of integer data type for the some variants in btrfs_root 2014-06-09 17:20:40 -07:00
tree-log.c Btrfs: ensure ordered extent errors aren't missed on fsync 2014-11-21 11:59:57 -08:00
tree-log.h Btrfs: fix data corruption after fast fsync and writeback error 2014-09-19 06:57:51 -07:00
ulist.c Btrfs: do not export ulist functions 2014-01-29 07:06:27 -08:00
ulist.h Btrfs: Fix memory corruption by ulist_add_merge() on 32bit arch 2014-08-15 07:43:19 -07:00
uuid-tree.c Btrfs: make btrfs_search_forward return with nodes unlocked 2014-09-17 13:38:02 -07:00
volumes.c Btrfs: fix race between fs trimming and block group remove/allocation 2014-12-02 18:35:09 -08:00
volumes.h Btrfs: fix race between fs trimming and block group remove/allocation 2014-12-02 18:35:09 -08:00
xattr.c Btrfs: make xattr replace operations atomic 2014-11-20 17:20:07 -08:00
xattr.h btrfs: use generic posix ACL infrastructure 2014-01-25 23:58:18 -05:00
zlib.c btrfs compression: merge inflate and deflate z_streams 2014-09-17 13:37:33 -07:00