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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 18:00:15 -0500
Cc: Eric Sandeen <sandeen@xxxxxxxxxx>, Boris Ranto <branto@xxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140428221849.GC18672@dastard>
References: <535E8344.2070209@xxxxxxxxxx> <20140428205420.GB18672@dastard> <535ECAA6.3050200@xxxxxxx> <20140428221849.GC18672@dastard>
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On 04/28/14 17:18, Dave Chinner wrote:
On Mon, Apr 28, 2014 at 04:39:50PM -0500, Mark Tinguely wrote:
>  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 
>  >>
>  >>[ 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.

>  Similar to what Jeff Liu mention in Dec:
>     http://oss.sgi.com/archives/xfs/2013-12/msg00870.html
Which fell through the cracks because of objections to calling
wake_up_all(&ctx->cil->xc_commit_wait) from xlog_cil_committed().

FYI, I just independently wrote a patch to fix this, and part of the
fix is that it calls wake_up_all(&ctx->cil->xc_commit_wait) from
xlog_cil_committed(). The rest of the fix indicates that the above
patch wasn't sufficient. Patch below.

This time it isn't going to fall through the cracks because I don't
think the objections are valid...



I did not intend to stall out the patch.

I came to like the idea of always notifying the waiters on an lsn after the iclog is successfully written out not just when we start the IO.


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