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Filipe David Borba Manana 5de865eebb Btrfs: fix tree mod logging 
While running the test btrfs/004 from xfstests in a loop, it failed
about 1 time out of 20 runs in my desktop. The failure happened in
the backref walking part of the test, and the test's error message was
like this:

  btrfs/004 93s ... [failed, exit status 1] - output mismatch (see /home/fdmanana/git/hub/xfstests_2/results//btrfs/004.out.bad)
      --- tests/btrfs/004.out	2013-11-26 18:25:29.263333714 +0000
      +++ /home/fdmanana/git/hub/xfstests_2/results//btrfs/004.out.bad	2013-12-10 15:25:10.327518516 +0000
      @@ -1,3 +1,8 @@
       QA output created by 004
       *** test backref walking
      -*** done
      +unexpected output from
      +	/home/fdmanana/git/hub/btrfs-progs/btrfs inspect-internal logical-resolve -P 141512704 /home/fdmanana/btrfs-tests/scratch_1
      +expected inum: 405, expected address: 454656, file: /home/fdmanana/btrfs-tests/scratch_1/snap1/p0/d6/d3d/d156/fce, got:
      +
       ...
       (Run 'diff -u tests/btrfs/004.out /home/fdmanana/git/hub/xfstests_2/results//btrfs/004.out.bad' to see the entire diff)
  Ran: btrfs/004
  Failures: btrfs/004
  Failed 1 of 1 tests

But immediately after the test finished, the btrfs inspect-internal command
returned the expected output:

  $ btrfs inspect-internal logical-resolve -P 141512704 /home/fdmanana/btrfs-tests/scratch_1
  inode 405 offset 454656 root 258
  inode 405 offset 454656 root 5

It turned out this was because the btrfs_search_old_slot() calls performed
during backref walking (backref.c:__resolve_indirect_ref) were not finding
anything. The reason for this turned out to be that the tree mod logging
code was not logging some node multi-step operations atomically, therefore
btrfs_search_old_slot() callers iterated often over an incomplete tree that
wasn't fully consistent with any tree state from the past. Besides missing
items, this often (but not always) resulted in -EIO errors during old slot
searches, reported in dmesg like this:

[ 4299.933936] ------------[ cut here ]------------
[ 4299.933949] WARNING: CPU: 0 PID: 23190 at fs/btrfs/ctree.c:1343 btrfs_search_old_slot+0x57b/0xab0 [btrfs]()
[ 4299.933950] Modules linked in: btrfs raid6_pq xor pci_stub vboxpci(O) vboxnetadp(O) vboxnetflt(O) vboxdrv(O) bnep rfcomm bluetooth parport_pc ppdev binfmt_misc joydev snd_hda_codec_h
[ 4299.933977] CPU: 0 PID: 23190 Comm: btrfs Tainted: G        W  O 3.12.0-fdm-btrfs-next-16+ #70
[ 4299.933978] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./Z77 Pro4, BIOS P1.50 09/04/2012
[ 4299.933979]  000000000000053f ffff8806f3fd98f8 ffffffff8176d284 0000000000000007
[ 4299.933982]  0000000000000000 ffff8806f3fd9938 ffffffff8104a81c ffff880659c64b70
[ 4299.933984]  ffff880659c643d0 ffff8806599233d8 ffff880701e2e938 0000160000000000
[ 4299.933987] Call Trace:
[ 4299.933991]  [<ffffffff8176d284>] dump_stack+0x55/0x76
[ 4299.933994]  [<ffffffff8104a81c>] warn_slowpath_common+0x8c/0xc0
[ 4299.933997]  [<ffffffff8104a86a>] warn_slowpath_null+0x1a/0x20
[ 4299.934003]  [<ffffffffa065d3bb>] btrfs_search_old_slot+0x57b/0xab0 [btrfs]
[ 4299.934005]  [<ffffffff81775f3b>] ? _raw_read_unlock+0x2b/0x50
[ 4299.934010]  [<ffffffffa0655001>] ? __tree_mod_log_search+0x81/0xc0 [btrfs]
[ 4299.934019]  [<ffffffffa06dd9b0>] __resolve_indirect_refs+0x130/0x5f0 [btrfs]
[ 4299.934027]  [<ffffffffa06a21f1>] ? free_extent_buffer+0x61/0xc0 [btrfs]
[ 4299.934034]  [<ffffffffa06de39c>] find_parent_nodes+0x1fc/0xe40 [btrfs]
[ 4299.934042]  [<ffffffffa06b13e0>] ? defrag_lookup_extent+0xe0/0xe0 [btrfs]
[ 4299.934048]  [<ffffffffa06b13e0>] ? defrag_lookup_extent+0xe0/0xe0 [btrfs]
[ 4299.934056]  [<ffffffffa06df980>] iterate_extent_inodes+0xe0/0x250 [btrfs]
[ 4299.934058]  [<ffffffff817762db>] ? _raw_spin_unlock+0x2b/0x50
[ 4299.934065]  [<ffffffffa06dfb82>] iterate_inodes_from_logical+0x92/0xb0 [btrfs]
[ 4299.934071]  [<ffffffffa06b13e0>] ? defrag_lookup_extent+0xe0/0xe0 [btrfs]
[ 4299.934078]  [<ffffffffa06b7015>] btrfs_ioctl+0xf65/0x1f60 [btrfs]
[ 4299.934080]  [<ffffffff811658b8>] ? handle_mm_fault+0x278/0xb00
[ 4299.934083]  [<ffffffff81075563>] ? up_read+0x23/0x40
[ 4299.934085]  [<ffffffff8177a41c>] ? __do_page_fault+0x20c/0x5a0
[ 4299.934088]  [<ffffffff811b2946>] do_vfs_ioctl+0x96/0x570
[ 4299.934090]  [<ffffffff81776e23>] ? error_sti+0x5/0x6
[ 4299.934093]  [<ffffffff810b71e8>] ? trace_hardirqs_off_caller+0x28/0xd0
[ 4299.934096]  [<ffffffff81776a09>] ? retint_swapgs+0xe/0x13
[ 4299.934098]  [<ffffffff811b2eb1>] SyS_ioctl+0x91/0xb0
[ 4299.934100]  [<ffffffff813eecde>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[ 4299.934102]  [<ffffffff8177ef12>] system_call_fastpath+0x16/0x1b
[ 4299.934102]  [<ffffffff8177ef12>] system_call_fastpath+0x16/0x1b
[ 4299.934104] ---[ end trace 48f0cfc902491414 ]---
[ 4299.934378] btrfs bad fsid on block 0

These tree mod log operations that must be performed atomically, tree_mod_log_free_eb,
tree_mod_log_eb_copy, tree_mod_log_insert_root and tree_mod_log_insert_move, used to
be performed atomically before the following commit:

  c8cc634165
  (Btrfs: stop using GFP_ATOMIC for the tree mod log allocations)

That change removed the atomicity of such operations. This patch restores the
atomicity while still not doing the GFP_ATOMIC allocations of tree_mod_elem
structures, so it has to do the allocations using GFP_NOFS before acquiring
the mod log lock.

This issue has been experienced by several users recently, such as for example:

  http://www.spinics.net/lists/linux-btrfs/msg28574.html

After running the btrfs/004 test for 679 consecutive iterations with this
patch applied, I didn't ran into the issue anymore.

Cc: stable@vger.kernel.org
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
2014-01-28 13:20:04 -08:00
..
tests Btrfs: add a sanity test for a vacant extent at the front of a file 2013-11-11 21:58:19 -05:00
acl.c btrfs: remove dead code 2014-01-28 13:19:50 -08:00
async-thread.c Btrfs: fix __btrfs_start_workers retval 2013-11-20 20:42:11 -05:00
async-thread.h Btrfs: eliminate races in worker stopping code 2013-10-04 16:02:13 -04:00
backref.c Btrfs: fix deadlock when iterating inode refs and running delayed inodes 2014-01-28 13:19:59 -08:00
backref.h Btrfs: allocate prelim_ref with a slab allocater 2013-09-01 08:16:27 -04:00
btrfs_inode.h Btrfs: improve inode hash function/inode lookup 2013-11-11 21:55:19 -05:00
check-integrity.c Btrfs: fix check-integrity to look at the referenced data properly 2014-01-28 13:19:21 -08:00
check-integrity.h block: submit_bio_wait() conversions 2013-11-24 16:33:41 -07:00
compression.c btrfs: Fix checkpatch.pl warning of spacing issues 2013-11-11 22:12:31 -05:00
compression.h btrfs: make static code static & remove dead code 2013-05-06 15:55:23 -04:00
ctree.c Btrfs: fix tree mod logging 2014-01-28 13:20:04 -08:00
ctree.h btrfs: Check read-only status of roots during send 2014-01-28 13:20:01 -08:00
delayed-inode.c btrfs: Replace kmalloc with kmalloc_array 2013-11-11 22:12:22 -05:00
delayed-inode.h [readdir] convert btrfs 2013-06-29 12:57:00 +04:00
delayed-ref.c Btrfs: skip merge part for delayed data refs 2014-01-28 13:19:23 -08:00
delayed-ref.h Btrfs: introduce a head ref rbtree 2014-01-28 13:19:22 -08:00
dev-replace.c btrfs: fix typo in the log message 2013-11-20 20:44:47 -05:00
dev-replace.h Btrfs: add new sources for device replace code 2012-12-12 17:15:41 -05:00
dir-item.c Btrfs: fix max dir item size calculation 2014-01-28 13:19:49 -08:00
disk-io.c Btrfs: move the extent buffer radix tree into the fs_info 2014-01-28 13:19:55 -08:00
disk-io.h Btrfs: add a sanity test for btrfs_split_item 2013-11-11 21:51:02 -05:00
export.c btrfs: remove fs/btrfs/compat.h 2013-11-11 22:03:19 -05:00
export.h
extent-tree.c Btrfs: fix double initialization of the raid kobject 2014-01-28 13:20:03 -08:00
extent_io.c Btrfs: move the extent buffer radix tree into the fs_info 2014-01-28 13:19:55 -08:00
extent_io.h Btrfs: move the extent buffer radix tree into the fs_info 2014-01-28 13:19:55 -08:00
extent_map.c Btrfs: fix extent_map block_len after merging 2014-01-28 13:19:51 -08:00
extent_map.h btrfs: Enclose macros with complex values within parenthesis 2013-11-11 22:12:06 -05:00
file-item.c btrfs: Use WARN_ON()'s return value in place of WARN_ON(1) 2013-11-11 22:11:53 -05:00
file.c Btrfs: fix use of uninitialized err variable 2014-01-28 13:19:57 -08:00
free-space-cache.c btrfs: remove unused variable from setup_cluster_no_bitmap 2014-01-28 13:19:33 -08:00
free-space-cache.h Btrfs: remove path arg from btrfs_truncate_free_space_cache 2013-11-11 21:51:33 -05:00
hash.h btrfs: extended inode refs 2012-10-09 09:14:45 -04:00
inode-item.c btrfs: cleanup: removed unused 'btrfs_get_inode_ref_index' 2014-01-28 13:19:39 -08:00
inode-map.c btrfs: Use WARN_ON()'s return value in place of WARN_ON(1) 2013-11-11 22:11:53 -05:00
inode-map.h
inode.c Btrfs: fix a warning when iput a file 2014-01-28 13:20:02 -08:00
ioctl.c btrfs: Check read-only status of roots during send 2014-01-28 13:20:01 -08:00
Kconfig Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2013-11-22 08:38:55 -08:00
locking.c btrfs: make static code static & remove dead code 2013-05-06 15:55:23 -04:00
locking.h Btrfs: remove btrfs_try_spin_lock 2013-03-14 14:57:10 -04:00
lzo.c Btrfs: return -1 when lzo compression makes data bigger 2013-09-01 07:57:19 -04:00
Makefile Btrfs: add tests for btrfs_get_extent 2013-11-11 21:57:30 -05:00
math.h Btrfs: cleanup duplicated division functions 2012-12-11 13:31:30 -05:00
ordered-data.c Btrfs: avoid unnecessary ordered extent cache resets 2014-01-28 13:19:46 -08:00
ordered-data.h Btrfs: don't wait for the completion of all the ordered extents 2013-11-11 22:13:44 -05:00
orphan.c btrfs: expand btrfs_find_item() to include find_orphan_item functionality 2014-01-28 13:19:37 -08:00
print-tree.c btrfs: drop unused parameter from btrfs_item_nr 2013-11-11 21:50:48 -05:00
print-tree.h btrfs: make static code static & remove dead code 2013-05-06 15:55:23 -04:00
qgroup.c btrfs: fix unused variables in qgroup.c 2014-01-28 13:19:35 -08:00
raid56.c btrfs: remove fs/btrfs/compat.h 2013-11-11 22:03:19 -05:00
raid56.h Btrfs: RAID5 and RAID6 2013-02-01 14:24:23 -05:00
rcu-string.h
reada.c Btrfs: fix reada debug code compilation 2013-05-06 15:54:55 -04:00
relocation.c Btrfs: remove unnecessary filemap writting and waiting after block group relocation 2014-01-28 13:19:57 -08:00
root-tree.c btrfs: expand btrfs_find_item() to include find_root_ref functionality 2014-01-28 13:19:36 -08:00
scrub.c Btrfs: wrap repeated code into scrub_blocked_if_needed() 2014-01-28 13:19:53 -08:00
send.c btrfs: check balance of send_in_progress 2014-01-28 13:20:04 -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 Btrfs: don't clear the default compression type 2013-12-12 07:11:19 -08:00
sysfs.c btrfs: fix leaks during sysfs teardown 2014-01-28 13:19:45 -08:00
sysfs.h btrfs: publish allocation data in sysfs 2014-01-28 13:19:29 -08:00
transaction.c Btrfs: wrap repeated code into scrub_blocked_if_needed() 2014-01-28 13:19:53 -08:00
transaction.h Btrfs: fix BUG_ON() casued by the reserved space migration 2013-11-11 21:54:28 -05:00
tree-defrag.c Btrfs: cleanup dead code of defragment 2013-11-11 21:59:45 -05:00
tree-log.c btrfs: expand btrfs_find_item() to include find_orphan_item functionality 2014-01-28 13:19:37 -08:00
tree-log.h btrfs: make static code static & remove dead code 2013-05-06 15:55:23 -04:00
ulist.c Btrfs: fix crash regarding to ulist_add_merge 2013-07-02 11:50:59 -04:00
ulist.h Btrfs: add a rb_tree to improve performance of ulist search 2013-05-06 15:54:44 -04:00
uuid-tree.c Btrfs: remove unused max_key arg from btrfs_search_forward 2013-11-11 21:54:57 -05:00
volumes.c btrfs: fix bio_size_ok() for max_sectors > 0xffff 2013-11-20 20:48:44 -05:00
volumes.h btrfs: Pack struct btrfs_device 2013-11-11 22:11:26 -05:00
xattr.c btrfs: make static code static & remove dead code 2013-05-06 15:55:23 -04:00
xattr.h
zlib.c btrfs: fix message printing 2012-10-09 09:19:57 -04:00