Possible memory allocation deadlock in kmem_alloc and hung task in xfs_log_commit_cil and xlog_cil_push

[Gavin Guo]

Hi all,

Recently, we observed that there is the error message in
Ubuntu-3.13.0-48.80:

"XFS: possible memory allocation deadlock in kmem_alloc (mode:0x8250)"

repeatedly shows in the dmesg. Temporarily, our workaround is to tune the
parameters, such as, vfs_cache_pressure, min_free_kbytes, and dirty_ratio.

And we also found that there are different error messages regarding the
hung tasks which happened in xfs_log_commit_cil and xlog_cil_push.

The log is available at: http://paste.ubuntu.com/11835007/

The following link seems the same problem we suffered:

XFS hangs with XFS: possible memory allocation deadlock in kmem_alloc
http://oss.sgi.com/archives/xfs/2015-03/msg00172.html

I read the mail and found that there might be some modification regarding
to move the memory allocation outside the ctx lock. And I also read the
latest patch from February of 2015 to see if there is any new change
about that. Unfortunately, I didn't find anything regarding the change (may
be I'm not familiar with the XFS, so didn't find the commit). If it's
possible for someone who is familiar with the code to point out the commits
related to the bug if already exist or any status about the plan.

Thanks,
Gavin Guo
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