From: Alex Elder <aelder@sgi.com>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/2] bdi: mark the bdi flusher busy when being forked
Date: Wed, 13 Apr 2011 14:29:23 -0500 [thread overview]
Message-ID: <1302722963.2023.66.camel@doink> (raw)
In-Reply-To: <1302157196-1988-2-git-send-email-david@fromorbit.com>
On Thu, 2011-04-07 at 16:19 +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> Recetn attempts to use writeback_inode_sb_nr_if_idle() in XFs from
> memory reclaim context have caused deadlocks because memory reclaim
> call be called from a failed allocation during forking a flusher
> thread. The shrinker then attempts to trigger writeback and the bdi
> is considered idle because writeback is not in progress yet and then
> deadlocks because bdi_queue_work() blocks waiting for the
> BDI_Pending bit to clear which will never happen because it needs
> the fork to complete.
>
> To avoid this deadlock, consider writeback to be in progress if the
> flusher thread is being created. This prevents reclaim from blocking
> waiting for it be forked and hence avoids the deadlock.
I don't believe it matters, but BDI_pending is also set
while a writeback flusher thread is being shut down.
In any case, a handy use of that flag bit.
Reviewed-by: Alex Elder <aelder@sgi.com>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
next prev parent reply other threads:[~2011-04-13 19:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-07 6:19 [PATCH 0/2] xfs: write back inodes during reclaim Dave Chinner
2011-04-07 6:19 ` [PATCH 1/2] bdi: mark the bdi flusher busy when being forked Dave Chinner
2011-04-11 18:34 ` Christoph Hellwig
2011-04-13 19:29 ` Alex Elder [this message]
2011-04-07 6:19 ` [PATCH 2/2] xfs: kick inode writeback when low on memory Dave Chinner
2011-04-11 18:36 ` Christoph Hellwig
2011-04-11 21:14 ` Dave Chinner
2011-04-13 20:33 ` Alex Elder
2011-04-14 5:08 ` Dave Chinner
2011-04-15 8:09 ` Christoph Hellwig
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