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Re: [PATCH] xfs: test for shut down fs in xfs_dir_fsync()

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH] xfs: test for shut down fs in xfs_dir_fsync()
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Mon, 28 Apr 2014 16:39:50 -0500
Cc: Eric Sandeen <sandeen@xxxxxxxxxx>, Boris Ranto <branto@xxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140428205420.GB18672@dastard>
References: <535E8344.2070209@xxxxxxxxxx> <20140428205420.GB18672@dastard>
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On 04/28/14 15:54, Dave Chinner wrote:
On Mon, Apr 28, 2014 at 11:35:16AM -0500, Eric Sandeen wrote:
Similar to xfs_file_fsync(), I think xfs_dir_fsync() needs
to test for a shut down fs, lest we go down paths we'll
never be able to complete; Boris reported that during some
stress tests he had threads stuck in xlog_cil_force_lsn
via xfs_dir_fsync().

[ 3663.361709] sfsuspend-par   D ffff88042f0b4540     0  3981   3947 0x00000080

[ 3663.394472] Call Trace:
[ 3663.397199]  [<ffffffff815f1889>] schedule+0x29/0x70
[ 3663.402743]  [<ffffffffa01feda5>] xlog_cil_force_lsn+0x185/0x1a0 [xfs]
[ 3663.416249]  [<ffffffffa01fd3af>] _xfs_log_force_lsn+0x6f/0x2f0 [xfs]
[ 3663.429271]  [<ffffffffa01a339d>] xfs_dir_fsync+0x7d/0xe0 [xfs]
[ 3663.435873]  [<ffffffff811df8c5>] do_fsync+0x65/0xa0
[ 3663.441408]  [<ffffffff811dfbc0>] SyS_fsync+0x10/0x20
[ 3663.447043]  [<ffffffff815fc7d9>] system_call_fastpath+0x16/0x1b

Wow, I believe it's taken this long for us to notice that we can't
break out of xlog_cil_force_lsn() if we fail on xlog_write()
from a CIL push.

I'd say that xlog_cil_force_lsn() needs log shutdown checks before
it goes to sleep in xlog_wait()....

Reported-by: Boris Ranto<branto@xxxxxxxxxx>
Signed-off-by: Eric Sandeen<sandeen@xxxxxxxxxx>
---

NB: While I've not asked Boris to test this yet, it seems
clear (?) that dir_fsync should behave the same as
file_fsync() in the face of a shut-down fs.

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 4c749ab..2b94362 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -146,6 +146,9 @@ xfs_dir_fsync(

        trace_xfs_dir_fsync(ip);

+       if (XFS_FORCED_SHUTDOWN(mp))
+               return -XFS_ERROR(EIO);
+

That won't hurt, but it won't fix the problem.

Cheers,

Dave.

Similar to what Jeff Liu mention in Dec:

  http://oss.sgi.com/archives/xfs/2013-12/msg00870.html

--Mark.

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