Also seeing full deadlocks with 3.15.1

[Marc MERLIN <marc@merlins.org>]

My laptop deadlocked some more times (everything works until it needs to
touch the filesystem, and then it's deadlocked).
Unfortunately, I can trigger sysrq, but it doesn't get committed to disk and
netconsole eats half of it because it goes too fast for UDP apparently

Now, I just captured that on my server with serial console.

11005  1-16:11:10 wait_current_trans.isra.15     /usr/bin/zma -m 3
14441  1-16:07:44 wait_current_trans.isra.15     /usr/bin/zma -m 1
17045  1-23:53:33 wait_current_trans.isra.15     /usr/bin/zma -m 9
22261  2-00:40:36 wait_current_trans.isra.15     /usr/bin/zma -m 6
22292  2-00:40:36 wait_current_trans.isra.15     /usr/bin/zma -m 8

19911    09:29:35 wait_current_trans.isra.15     rm -f -- /mnt/dshelf2/backup/0Notmachines/mysql//mysql.daily.sql.gz.13 /mnt/dshelf2/backup/0Notmachines/mysql//mysql.daily.sql.gz.13.gz
22848  1-05:18:35 wait_current_trans.isra.15     rm -f -- mnt/dshelf2/backup/0Notmachines/jen//backup.tar.bz.11 mnt/dshelf2/backup/0Notmachines/jen//backup.tar.bz.11.gz

Those are 2 different filesystems (one single device mapper disk, the other one is btrfs raid1), so I'm not sure which one of the 2 caused the problem, but I'm perplexed as to why one would than hang the other, unless they both hit the same bug?

The sysrq-w output is here:
http://marc.merlins.org/tmp/btrfs-hang.txt

but here is one hung process:
 zma		D 0000000000000003     0 22292	    1 0x20020084
  ffff880074733bb0 0000000000000082 ffff8800c933f270 ffff880074733fd8
  ffff8801853b4610 00000000000141c0 ffff8801aac60f00 ffff880036caa9e8
  0000000000000000 ffff880036caa800 ffff8801db59f0c0 ffff880074733bc0
 Call Trace:
  [<ffffffff8161d3c6>] schedule+0x73/0x75
  [<ffffffff8122a87b>] wait_current_trans.isra.15+0x98/0xf4
  [<ffffffff810847ed>] ? finish_wait+0x65/0x65
  [<ffffffff8122bd95>] start_transaction+0x498/0x4fc
  [<ffffffff8122be14>] btrfs_start_transaction+0x1b/0x1d
  [<ffffffff8123602a>] btrfs_create+0x3c/0x1ce
  [<ffffffff81298985>] ? security_inode_permission+0x1c/0x23
  [<ffffffff8115e93e>] ? __inode_permission+0x79/0xa4
  [<ffffffff8115fbfc>] vfs_create+0x66/0x8c
  [<ffffffff8116095e>] do_last+0x5af/0xa23
  [<ffffffff81161009>] path_openat+0x237/0x4de
  [<ffffffff81162408>] do_filp_open+0x3a/0x7f
  [<ffffffff8161faeb>] ? _raw_spin_unlock+0x17/0x2a
  [<ffffffff8116c3eb>] ? __alloc_fd+0xea/0xf9
  [<ffffffff8115499d>] do_sys_open+0x70/0xff
  [<ffffffff81194e20>] compat_SyS_open+0x1b/0x1d
  [<ffffffff8162842c>] sysenter_dispatch+0x7/0x21

As per the other thread, I'm happy to test a patch against 3.15, but not hot about switching to a likely even less stable 3.16 since it's a real server with real data.

Thanks,
Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/