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  1. 24 2月, 2017 7 次提交
    • F
      Btrfs: fix assertion failure when freeing block groups at close_ctree() · 5cdd7db6
      由 Filipe Manana 提交于 
      At close_ctree() we free the block groups and then only after we wait for
any running worker kthreads to finish and shutdown the workqueues. This
behaviour is racy and it triggers an assertion failure when freeing block
groups because while we are doing it we can have for example a block group
caching kthread running, and in that case the block group's reference
count can still be greater than 1 by the time we assert its reference count
is 1, leading to an assertion failure:

[19041.198004] assertion failed: atomic_read(&block_group->count) == 1, file: fs/btrfs/extent-tree.c, line: 9799
[19041.200584] ------------[ cut here ]------------
[19041.201692] kernel BUG at fs/btrfs/ctree.h:3418!
[19041.202830] invalid opcode: 0000 [#1] PREEMPT SMP
[19041.203929] Modules linked in: btrfs xor raid6_pq dm_flakey dm_mod crc32c_generic ppdev sg psmouse acpi_cpufreq pcspkr parport_pc evdev tpm_tis parport tpm_tis_core i2c_piix4 i2c_core tpm serio_raw processor button loop autofs4 ext4 crc16 jbd2 mbcache sr_mod cdrom sd_mod ata_generic virtio_scsi ata_piix virtio_pci libata virtio_ring virtio e1000 scsi_mod floppy [last unloaded: btrfs]
[19041.208082] CPU: 6 PID: 29051 Comm: umount Not tainted 4.9.0-rc7-btrfs-next-36+ #1
[19041.208082] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
[19041.208082] task: ffff88015f028980 task.stack: ffffc9000ad34000
[19041.208082] RIP: 0010:[<ffffffffa03e319e>]  [<ffffffffa03e319e>] assfail.constprop.41+0x1c/0x1e [btrfs]
[19041.208082] RSP: 0018:ffffc9000ad37d60  EFLAGS: 00010286
[19041.208082] RAX: 0000000000000061 RBX: ffff88015ecb4000 RCX: 0000000000000001
[19041.208082] RDX: ffff88023f392fb8 RSI: ffffffff817ef7ba RDI: 00000000ffffffff
[19041.208082] RBP: ffffc9000ad37d60 R08: 0000000000000001 R09: 0000000000000000
[19041.208082] R10: ffffc9000ad37cb0 R11: ffffffff82f2b66d R12: ffff88023431d170
[19041.208082] R13: ffff88015ecb40c0 R14: ffff88023431d000 R15: ffff88015ecb4100
[19041.208082] FS:  00007f44f3d42840(0000) GS:ffff88023f380000(0000) knlGS:0000000000000000
[19041.208082] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[19041.208082] CR2: 00007f65d623b000 CR3: 00000002166f2000 CR4: 00000000000006e0
[19041.208082] Stack:
[19041.208082]  ffffc9000ad37d98 ffffffffa035989f ffff88015ecb4000 ffff88015ecb5630
[19041.208082]  ffff88014f6be000 0000000000000000 00007ffcf0ba6a10 ffffc9000ad37df8
[19041.208082]  ffffffffa0368cd4 ffff88014e9658e0 ffffc9000ad37e08 ffffffff811a634d
[19041.208082] Call Trace:
[19041.208082]  [<ffffffffa035989f>] btrfs_free_block_groups+0x17f/0x392 [btrfs]
[19041.208082]  [<ffffffffa0368cd4>] close_ctree+0x1c5/0x2e1 [btrfs]
[19041.208082]  [<ffffffff811a634d>] ? evict_inodes+0x132/0x141
[19041.208082]  [<ffffffffa034356d>] btrfs_put_super+0x15/0x17 [btrfs]
[19041.208082]  [<ffffffff8118fc32>] generic_shutdown_super+0x6a/0xeb
[19041.208082]  [<ffffffff8119004f>] kill_anon_super+0x12/0x1c
[19041.208082]  [<ffffffffa0343370>] btrfs_kill_super+0x16/0x21 [btrfs]
[19041.208082]  [<ffffffff8118fad1>] deactivate_locked_super+0x3b/0x68
[19041.208082]  [<ffffffff8118fb34>] deactivate_super+0x36/0x39
[19041.208082]  [<ffffffff811a9946>] cleanup_mnt+0x58/0x76
[19041.208082]  [<ffffffff811a99a2>] __cleanup_mnt+0x12/0x14
[19041.208082]  [<ffffffff81071573>] task_work_run+0x6f/0x95
[19041.208082]  [<ffffffff81001897>] prepare_exit_to_usermode+0xa3/0xc1
[19041.208082]  [<ffffffff81001a23>] syscall_return_slowpath+0x16e/0x1d2
[19041.208082]  [<ffffffff814c607d>] entry_SYSCALL_64_fastpath+0xab/0xad
[19041.208082] Code: c7 ae a0 3e a0 48 89 e5 e8 4e 74 d4 e0 0f 0b 55 89 f1 48 c7 c2 0b a4 3e a0 48 89 fe 48 c7 c7 a4 a6 3e a0 48 89 e5 e8 30 74 d4 e0 <0f> 0b 55 31 d2 48 89 e5 e8 d5 b9 f7 ff 5d c3 48 63 f6 55 31 c9
[19041.208082] RIP  [<ffffffffa03e319e>] assfail.constprop.41+0x1c/0x1e [btrfs]
[19041.208082]  RSP <ffffc9000ad37d60>
[19041.279264] ---[ end trace 23330586f16f064d ]---

This started happening as of kernel 4.8, since commit f3bca802
("Btrfs: add ASSERT for block group's memory leak") introduced these
assertions.

So fix this by freeing the block groups only after waiting for all
worker kthreads to complete and shutdown the workqueues.
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
Reviewed-by: NLiu Bo <bo.li.liu@oracle.com>
      5cdd7db6
    • F
      Btrfs: do not create explicit holes when replaying log tree if NO_HOLES enabled · 3168021c
      由 Filipe Manana 提交于 
      We log holes explicitly by using file extent items, however when replaying
a log tree, if a logged file extent item corresponds to a hole and the
NO_HOLES feature is enabled we do not need to copy the file extent item
into the fs/subvolume tree, as the absence of such file extent items is
the purpose of the NO_HOLES feature. So skip the copying of file extent
items representing holes when the NO_HOLES feature is enabled.
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
      3168021c
    • R
      Btrfs: fix leak of subvolume writers counter · 91e1f56a
      由 Robbie Ko 提交于 
      When falling back from a nocow write to a regular cow write, we were
leaking the subvolume writers counter in 2 situations, preventing
snapshot creation from ever completing in the future, as it waits
for that counter to go down to zero before the snapshot creation
starts.
Signed-off-by: NRobbie Ko <robbieko@synology.com>
Reviewed-by: NFilipe Manana <fdmanana@suse.com>
[Improved changelog and subject]
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
      91e1f56a
    • F
      Btrfs: bulk delete checksum items in the same leaf · 6f546216
      由 Filipe Manana 提交于 
      Very often we have the checksums for an extent spread in multiple items
in the checksums tree, and currently the algorithm to delete them starts
by looking for them one by one and then deleting them one by one, which
is not optimal since each deletion involves shifting all the other items
in the leaf and when the leaf reaches some low threshold, to move items
off the leaf into its left and right neighbor leafs. Also, after each
item deletion we release our search path and start a new search for other
checksums items.

So optimize this by deleting in bulk all the items in the same leaf that
contain checksums for the extent being freed.
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
Reviewed-by: NLiu Bo <bo.li.liu@oracle.com>
      6f546216
    • R
      Btrfs: incremental send, do not issue invalid rmdir operations · 01914101
      由 Robbie Ko 提交于 
      When both the parent and send snapshots have a directory inode with the
same number but different generations (therefore they are different
inodes) and both have an entry with the same name, an incremental send
stream will contain an invalid rmdir operation that refers to the
orphanized name of the inode from the parent snapshot.

The following example scenario shows how this happens.

Parent snapshot:

 .
 |---- d259_old/               (ino 259, gen 9)
 |         |---- d1/           (ino 258, gen 9)
 |
 |---- f                       (ino 257, gen 9)

Send snapshot:

 .
 |---- d258/                   (ino 258, gen 7)
 |---- d259/                   (ino 259, gen 7)
         |---- d1/             (ino 257, gen 7)

When the kernel is processing inode 258 it notices that in both snapshots
there is an inode numbered 259 that is a parent of an inode 258. However
it ignores the fact that the inodes numbered 259 have different generations
in both snapshots, which means they are effectively different inodes.
Then it checks that both inodes 259 have a dentry named "d1" and because
of that it issues a rmdir operation with orphanized name of the inode 258
from the parent snapshot. This happens at send.c:process_record_refs(),
which calls send.c:did_overwrite_first_ref() that returns true and because
of that later on at process_recorded_refs() such rmdir operation is issued
because the inode being currently processed (258) is a directory and it
was deleted in the send snapshot (and replaced with another inode that has
the same number and is a directory too).
Fix this issue by comparing the generations of parent directory inodes
that have the same number and make send.c:did_overwrite_first_ref() when
the generations are different.

The following steps reproduce the problem.

 $ mkfs.btrfs -f /dev/sdb
 $ mount /dev/sdb /mnt
 $ touch /mnt/f
 $ mkdir /mnt/d1
 $ mkdir /mnt/d259_old
 $ mv /mnt/d1 /mnt/d259_old/d1
 $ btrfs subvolume snapshot -r /mnt /mnt/snap1
 $ btrfs send /mnt/snap1 -f /tmp/1.snap
 $ umount /mnt

 $ mkfs.btrfs -f /dev/sdc
 $ mount /dev/sdc /mnt
 $ mkdir /mnt/d1
 $ mkdir /mnt/dir258
 $ mkdir /mnt/dir259
 $ mv /mnt/d1 /mnt/dir259/d1
 $ btrfs subvolume snapshot -r /mnt /mnt/snap2
 $ btrfs receive /mnt/ -f /tmp/1.snap
 # Take note that once the filesystem is created, its current
 # generation has value 7 so the inodes from the second snapshot all have
 # a generation value of 7. And after receiving the first snapshot
 # the filesystem is at a generation value of 10, because the call to
 # create the second snapshot bumps the generation to 8 (the snapshot
 # creation ioctl does a transaction commit), the receive command calls
 # the snapshot creation ioctl to create the first snapshot, which bumps
 # the filesystem's generation to 9, and finally when the receive
 # operation finishes it calls an ioctl to transition the first snapshot
 # (snap1) from RW mode to RO mode, which does another transaction commit
 # and bumps the filesystem's generation to 10. This means all the inodes
 # in the first snapshot (snap1) have a generation value of 9.
 $ rm -f /tmp/1.snap
 $ btrfs send /mnt/snap1 -f /tmp/1.snap
 $ btrfs send -p /mnt/snap1 /mnt/snap2 -f /tmp/2.snap
 $ umount /mnt

 $ mkfs.btrfs -f /dev/sdd
 $ mount /dev/sdd /mnt
 $ btrfs receive /mnt -f /tmp/1.snap
 $ btrfs receive -vv /mnt -f /tmp/2.snap
 receiving snapshot mysnap2 uuid=9c03962f-f620-0047-9f98-32e5a87116d9, ctransid=7 parent_uuid=d17a6e3f-14e5-df4f-be39-a7951a5399aa, parent_ctransid=9
 utimes
 unlink f
 mkdir o257-7-0
 mkdir o259-7-0
 rename o257-7-0 -> o259-7-0/d1
 chown o259-7-0/d1 - uid=0, gid=0
 chmod o259-7-0/d1 - mode=0755
 utimes o259-7-0/d1
 rmdir o258-9-0
 ERROR: rmdir o258-9-0 failed: No such file or directory
Signed-off-by: NRobbie Ko <robbieko@synology.com>
Reviewed-by: NFilipe Manana <fdmanana@suse.com>
[Rewrote changelog to be more precise and clear]
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
      01914101
    • F
      Btrfs: incremental send, do not delay rename when parent inode is new · fe9c798d
      由 Filipe Manana 提交于 
      When we are checking if we need to delay the rename operation for an
inode we not checking if a parent inode that exists in the send and
parent snapshots is really the same inode or not, that is, we are not
comparing the generation number of the parent inode in the send and
parent snapshots. Not only this results in unnecessarily delaying a
rename operation but also can later on make us generate an incorrect
name for a new inode in the send snapshot that has the same number
as another inode in the parent snapshot but a different generation.

Here follows an example where this happens.

Parent snapshot:

 .                                                  (ino 256, gen 3)
 |--- dir258/                                       (ino 258, gen 7)
 |       |--- dir257/                               (ino 257, gen 7)
 |
 |--- dir259/                                       (ino 259, gen 7)

Send snapshot:

 .                                                  (ino 256, gen 3)
 |--- file258                                       (ino 258, gen 10)
 |
 |--- new_dir259/                                   (ino 259, gen 10)
          |--- dir257/                              (ino 257, gen 7)

The following steps happen when computing the incremental send stream:

1) When processing inode 257, its new parent is created using its orphan
   name (o257-21-0), and the rename operation for inode 257 is delayed
   because its new parent (inode 259) was not yet processed - this
   decision to delay the rename operation does not make much sense
   because the inode 259 in the send snapshot is a new inode, it's not
   the same as inode 259 in the parent snapshot.

2) When processing inode 258 we end up delaying its rmdir operation,
   because inode 257 was not yet renamed (moved away from the directory
   inode 258 represents). We also create the new inode 258 using its
   orphan name "o258-10-0", then rename it to its final name of "file258"
   and then issue a truncate operation for it. However this truncate
   operation contains an incorrect name, which corresponds to the orphan
   name and not to the final name, which makes the receiver fail. This
   happens because when we attempt to compute the inode's current name
   we verify that there's another inode with the same number (258) that
   has its rmdir operation pending and because of that we generate an
   orphan name for the new inode 258 (we do this in the function
   get_cur_path()).

Fix this by not delayed the rename operation of an inode if it has parents
with the same number but different generations in both snapshots.

The following steps reproduce this example scenario.

 $ mkfs.btrfs -f /dev/sdb
 $ mount /dev/sdb /mnt
 $ mkdir /mnt/dir257
 $ mkdir /mnt/dir258
 $ mkdir /mnt/dir259
 $ mv /mnt/dir257 /mnt/dir258/dir257
 $ btrfs subvolume snapshot -r /mnt /mnt/snap1

 $ mv /mnt/dir258/dir257 /mnt/dir257
 $ rmdir /mnt/dir258
 $ rmdir /mnt/dir259

 # Remount the filesystem so that the next created inodes will have the
 # numbers 258 and 259. This is because when a filesystem is mounted,
 # btrfs sets the subvolume's inode counter to a value corresponding to
 # the highest inode number in the subvolume plus 1. This inode counter
 # is used to assign a unique number to each new inode and it's
 # incremented by 1 after very inode creation.
 # Note: we unmount and then mount instead of doing a mount with
 # "-o remount" because otherwise the inode counter remains at value 260.
 $ umount /mnt
 $ mount /dev/sdb /mnt
 $ touch /mnt/file258
 $ mkdir /mnt/new_dir259
 $ mv /mnt/dir257 /mnt/new_dir259/dir257
 $ btrfs subvolume snapshot -r /mnt /mnt/snap2

 $ btrfs send /mnt/snap1 -f /tmp/1.snap
 $ btrfs send -p /mnt/snap1 /mnt/snap2 -f /tmp/2.snap

 $ umount /mnt
 $ mkfs.btrfs -f /dev/sdc
 $ mount /dev/sdc /mnt
 $ btrfs receive /mnt -f /tmo/1.snap
 $ btrfs receive /mnt -f /tmo/2.snap -vv
 receiving snapshot mysnap2 uuid=e059b6d1-7f55-f140-8d7c-9a3039d23c97, ctransid=10 parent_uuid=77e98cb6-8762-814f-9e05-e8ba877fc0b0, parent_ctransid=7
 utimes
 mkdir o259-10-0
 rename dir258 -> o258-7-0
 utimes
 mkfile o258-10-0
 rename o258-10-0 -> file258
 utimes
 truncate o258-10-0 size=0
 ERROR: truncate o258-10-0 failed: No such file or directory
Reported-by: NRobbie Ko <robbieko@synology.com>
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
      fe9c798d
    • R
      Btrfs: send, fix failure to rename top level inode due to name collision · 4dd9920d
      由 Robbie Ko 提交于 
      Under certain situations, an incremental send operation can fail due to a
premature attempt to create a new top level inode (a direct child of the
subvolume/snapshot root) whose name collides with another inode that was
removed from the send snapshot.

Consider the following example scenario.

Parent snapshot:

  .                 (ino 256, gen 8)
  |---- a1/         (ino 257, gen 9)
  |---- a2/         (ino 258, gen 9)

Send snapshot:

  .                 (ino 256, gen 3)
  |---- a2/         (ino 257, gen 7)

In this scenario, when receiving the incremental send stream, the btrfs
receive command fails like this (ran in verbose mode, -vv argument):

  rmdir a1
  mkfile o257-7-0
  rename o257-7-0 -> a2
  ERROR: rename o257-7-0 -> a2 failed: Is a directory

What happens when computing the incremental send stream is:

1) An operation to remove the directory with inode number 257 and
   generation 9 is issued.

2) An operation to create the inode with number 257 and generation 7 is
   issued. This creates the inode with an orphanized name of "o257-7-0".

3) An operation rename the new inode 257 to its final name, "a2", is
   issued. This is incorrect because inode 258, which has the same name
   and it's a child of the same parent (root inode 256), was not yet
   processed and therefore no rmdir operation for it was yet issued.
   The rename operation is issued because we fail to detect that the
   name of the new inode 257 collides with inode 258, because their
   parent, a subvolume/snapshot root (inode 256) has a different
   generation in both snapshots.

So fix this by ignoring the generation value of a parent directory that
matches a root inode (number 256) when we are checking if the name of the
inode currently being processed collides with the name of some other
inode that was not yet processed.

We can achieve this scenario of different inodes with the same number but
different generation values either by mounting a filesystem with the inode
cache option (-o inode_cache) or by creating and sending snapshots across
different filesystems, like in the following example:

  $ mkfs.btrfs -f /dev/sdb
  $ mount /dev/sdb /mnt
  $ mkdir /mnt/a1
  $ mkdir /mnt/a2
  $ btrfs subvolume snapshot -r /mnt /mnt/snap1
  $ btrfs send /mnt/snap1 -f /tmp/1.snap
  $ umount /mnt

  $ mkfs.btrfs -f /dev/sdc
  $ mount /dev/sdc /mnt
  $ touch /mnt/a2
  $ btrfs subvolume snapshot -r /mnt /mnt/snap2
  $ btrfs receive /mnt -f /tmp/1.snap
  # Take note that once the filesystem is created, its current
  # generation has value 7 so the inode from the second snapshot has
  # a generation value of 7. And after receiving the first snapshot
  # the filesystem is at a generation value of 10, because the call to
  # create the second snapshot bumps the generation to 8 (the snapshot
  # creation ioctl does a transaction commit), the receive command calls
  # the snapshot creation ioctl to create the first snapshot, which bumps
  # the filesystem's generation to 9, and finally when the receive
  # operation finishes it calls an ioctl to transition the first snapshot
  # (snap1) from RW mode to RO mode, which does another transaction commit
  # and bumps the filesystem's generation to 10.
  $ rm -f /tmp/1.snap
  $ btrfs send /mnt/snap1 -f /tmp/1.snap
  $ btrfs send -p /mnt/snap1 /mnt/snap2 -f /tmp/2.snap
  $ umount /mnt

  $ mkfs.btrfs -f /dev/sdd
  $ mount /dev/sdd /mnt
  $ btrfs receive /mnt /tmp/1.snap
  # Receive of snapshot snap2 used to fail.
  $ btrfs receive /mnt /tmp/2.snap
Signed-off-by: NRobbie Ko <robbieko@synology.com>
Reviewed-by: NFilipe Manana <fdmanana@suse.com>
[Rewrote changelog to be more precise and clear]
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
      4dd9920d
  3. 23 2月, 2017 2 次提交
    • L
      Btrfs: use the correct type when creating cow dio extent · 6288d6ea
      由 Liu Bo 提交于 
      'BTRFS_ORDERED_REGULAR' was introduced for the cow case in patch
'Btrfs: specify a new ordered extent type for create_io_em',
but it missed the directIO cow case.
Signed-off-by: NLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: NChris Mason <clm@fb.com>
      6288d6ea
    • F
      Btrfs: fix deadlock between dedup on same file and starting writeback · b1517622
      由 Filipe Manana 提交于 
      If we are deduping two ranges of the same file we need to make sure that
we lock all pages in ascending order, that is, lock first the pages from
the range with lower offset and then the pages from the other range, as
otherwise we can deadlock with a concurrent task that is starting delalloc
(writeback). Example trace:

[74073.052218] INFO: task kworker/u32:10:17997 blocked for more than 120 seconds.
[74073.053889]       Tainted: G        W       4.9.0-rc7-btrfs-next-36+ #1
[74073.055071] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[74073.056696] kworker/u32:10  D    0 17997      2 0x00000000
[74073.058606] Workqueue: writeback wb_workfn (flush-btrfs-53176)
[74073.061370]  ffff880031e79858 ffff8802159d2580 ffff880237004580 ffff880031e79240
[74073.064784]  ffff88023f4978c0 ffffc9000817b638 ffffffff814c15e1 0000000000000000
[74073.068386]  ffff88023f4978d8 ffff88023f4978c0 000000000017b620 ffff880031e79240
[74073.071712] Call Trace:
[74073.072884]  [<ffffffff814c15e1>] ? __schedule+0x48f/0x6f4
[74073.075395]  [<ffffffff814c1c8b>] ? bit_wait+0x2f/0x2f
[74073.077511]  [<ffffffff814c18d2>] schedule+0x8c/0xa0
[74073.079440]  [<ffffffff814c4b36>] schedule_timeout+0x43/0xff
[74073.081637]  [<ffffffff8110953e>] ? time_hardirqs_on+0x9/0x14
[74073.083809]  [<ffffffff81095c67>] ? trace_hardirqs_on_caller+0x16/0x197
[74073.086314]  [<ffffffff810bde98>] ? timekeeping_get_ns+0x1e/0x32
[74073.100654]  [<ffffffff810be048>] ? ktime_get+0x41/0x52
[74073.102619]  [<ffffffff814c10f0>] io_schedule_timeout+0xa0/0x102
[74073.104771]  [<ffffffff814c10f0>] ? io_schedule_timeout+0xa0/0x102
[74073.106969]  [<ffffffff814c1ca6>] bit_wait_io+0x1b/0x39
[74073.108954]  [<ffffffff814c1fb8>] __wait_on_bit_lock+0x4f/0x99
[74073.110981]  [<ffffffff8112b692>] __lock_page+0x6b/0x6d
[74073.112833]  [<ffffffff8108ceb4>] ? autoremove_wake_function+0x3a/0x3a
[74073.115010]  [<ffffffffa031178b>] lock_page+0x2f/0x32 [btrfs]
[74073.116999]  [<ffffffffa0311d9f>] lock_delalloc_pages+0xc7/0x1a0 [btrfs]
[74073.119243]  [<ffffffffa0313d15>] find_lock_delalloc_range+0xc3/0x1a4 [btrfs]
[74073.121636]  [<ffffffffa0313e81>] writepage_delalloc.isra.31+0x8b/0x134 [btrfs]
[74073.124229]  [<ffffffffa0315d69>] __extent_writepage+0x1c1/0x2bf [btrfs]
[74073.126372]  [<ffffffffa03160f2>] extent_write_cache_pages.isra.30.constprop.49+0x28b/0x36c [btrfs]
[74073.129371]  [<ffffffffa03165b9>] extent_writepages+0x4b/0x5c [btrfs]
[74073.131440]  [<ffffffffa02fcb59>] ? insert_reserved_file_extent.constprop.42+0x261/0x261 [btrfs]
[74073.134303]  [<ffffffff811b4ce4>] ? writeback_sb_inodes+0xe0/0x4a1
[74073.136298]  [<ffffffffa02fab7f>] btrfs_writepages+0x28/0x2a [btrfs]
[74073.138248]  [<ffffffff81138200>] do_writepages+0x23/0x2c
[74073.139910]  [<ffffffff811b3cab>] __writeback_single_inode+0x105/0x6d2
[74073.142003]  [<ffffffff811b4e96>] writeback_sb_inodes+0x292/0x4a1
[74073.136298]  [<ffffffffa02fab7f>] btrfs_writepages+0x28/0x2a [btrfs]
[74073.138248]  [<ffffffff81138200>] do_writepages+0x23/0x2c
[74073.139910]  [<ffffffff811b3cab>] __writeback_single_inode+0x105/0x6d2
[74073.142003]  [<ffffffff811b4e96>] writeback_sb_inodes+0x292/0x4a1
[74073.143911]  [<ffffffff811b511b>] __writeback_inodes_wb+0x76/0xae
[74073.145787]  [<ffffffff811b53ca>] wb_writeback+0x1cc/0x4d7
[74073.147452]  [<ffffffff811b60cd>] wb_workfn+0x194/0x37d
[74073.149084]  [<ffffffff811b60cd>] ? wb_workfn+0x194/0x37d
[74073.150726]  [<ffffffff8106ce77>] ? process_one_work+0x154/0x4e4
[74073.152694]  [<ffffffff8106cf96>] process_one_work+0x273/0x4e4
[74073.154452]  [<ffffffff8106d6db>] worker_thread+0x1eb/0x2ca
[74073.156138]  [<ffffffff8106d4f0>] ? rescuer_thread+0x2b6/0x2b6
[74073.157837]  [<ffffffff81072a81>] kthread+0xd5/0xdd
[74073.159339]  [<ffffffff810729ac>] ? __kthread_unpark+0x5a/0x5a
[74073.161088]  [<ffffffff814c6257>] ret_from_fork+0x27/0x40
[74073.162680] INFO: lockdep is turned off.
[74073.163855] INFO: task do-dedup:30264 blocked for more than 120 seconds.
[74073.181180]       Tainted: G        W       4.9.0-rc7-btrfs-next-36+ #1
[74073.181180] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[74073.185296] fdm-stress      D    0 30264  29974 0x00000000
[74073.186810]  ffff880089595118 ffff880211b8eac0 ffff880237030380 ffff880089594b00
[74073.188998]  ffff88023f2978c0 ffffc900063abb68 ffffffff814c15e1 0000000000000000
[74073.191070]  ffff88023f2978d8 ffff88023f2978c0 00000000003abb50 ffff880089594b00
[74073.193286] Call Trace:
[74073.193990]  [<ffffffff814c15e1>] ? __schedule+0x48f/0x6f4
[74073.195418]  [<ffffffff814c1c8b>] ? bit_wait+0x2f/0x2f
[74073.196796]  [<ffffffff814c18d2>] schedule+0x8c/0xa0
[74073.198163]  [<ffffffff814c4b36>] schedule_timeout+0x43/0xff
[74073.199621]  [<ffffffff81095df5>] ? trace_hardirqs_on+0xd/0xf
[74073.201100]  [<ffffffff810bde98>] ? timekeeping_get_ns+0x1e/0x32
[74073.202686]  [<ffffffff810be048>] ? ktime_get+0x41/0x52
[74073.204051]  [<ffffffff814c10f0>] io_schedule_timeout+0xa0/0x102
[74073.205585]  [<ffffffff814c10f0>] ? io_schedule_timeout+0xa0/0x102
[74073.207123]  [<ffffffff814c1ca6>] bit_wait_io+0x1b/0x39
[74073.208238]  [<ffffffff814c1fb8>] __wait_on_bit_lock+0x4f/0x99
[74073.208871]  [<ffffffff8112b692>] __lock_page+0x6b/0x6d
[74073.209430]  [<ffffffff8108ceb4>] ? autoremove_wake_function+0x3a/0x3a
[74073.210101]  [<ffffffff8112b800>] lock_page+0x2f/0x32
[74073.210636]  [<ffffffff8112c502>] pagecache_get_page+0x5e/0x153
[74073.211270]  [<ffffffffa03257eb>] gather_extent_pages+0x4e/0x109 [btrfs]
[74073.212166]  [<ffffffffa032a04c>] btrfs_dedupe_file_range+0x1e1/0x4dd [btrfs]
[74073.213257]  [<ffffffff8118d9b5>] vfs_dedupe_file_range+0x1c1/0x221
[74073.214086]  [<ffffffff8119e0c4>] do_vfs_ioctl+0x442/0x600
[74073.214767]  [<ffffffff811a7874>] ? rcu_read_unlock+0x5b/0x5d
[74073.215619]  [<ffffffff811a7953>] ? __fget+0x6b/0x77
[74073.216338]  [<ffffffff8119e2d9>] SyS_ioctl+0x57/0x79
[74073.217149]  [<ffffffff814c5fea>] entry_SYSCALL_64_fastpath+0x18/0xad
[74073.218102]  [<ffffffff81109552>] ? time_hardirqs_off+0x9/0x14
[74073.218968]  [<ffffffff810938ce>] ? trace_hardirqs_off_caller+0x1f/0xaa
[74073.219938] INFO: lockdep is turned off.

What happened was the following:

      CPU 1                                       CPU 2

                                             btrfs_dedupe_file_range()
                                               --> using same inode as source
                                                   and target
                                               --> src range is [768K, 1Mb[
                                               --> dst range is [0, 256K[
                                              btrfs_cmp_data_prepare()
                                               --> calls gather_extent_pages()
                                                   for range [768K, 1Mb[ and
                                                   locks all pages in that range

 do_writepages()
  btrfs_writepages()
   extent_writepages()
    extent_write_cache_pages()
     __extent_writepage()
      writepage_delalloc()
       find_lock_delalloc_range()
         --> finds range [0, 1Mb[
         lock_delalloc_pages()
          --> locks all pages in the
              range [0, 768K[
          --> tries to lock page at
              offset 768K
                --> deadlock

                                               --> calls gather_extent_pages()
                                                   to lock pages in the range
                                                   [0, 256K[
                                                    --> deadlock, task at CPU 1
                                                        already locked that
                                                        range and it's trying
                                                        to lock the range we
                                                        locked previously

So fix this by making sure that during a dedup we always lock first the
pages from the range with lower offset.
Signed-off-by: NFilipe Manana <fdmanana@suse.com>
Signed-off-by: NChris Mason <clm@fb.com>
      b1517622
  5. 17 2月, 2017 31 次提交