From: Mikulas Patocka <mpatocka@redhat.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Mike Snitzer <msnitzer@redhat.com>,
junxiao.bi@oracle.com, dm-devel@redhat.com,
Alasdair Kergon <agk@redhat.com>,
honglei.wang@oracle.com, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org
Subject: Re: [PATCH] direct-io: use GFP_NOIO to avoid deadlock
Date: Fri, 9 Aug 2019 07:30:00 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1908090725290.31061@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <20190809013403.GY7777@dread.disaster.area>
On Fri, 9 Aug 2019, Dave Chinner wrote:
> And, FWIW, there's an argument to be made here that the underlying
> bug is dm_bufio_shrink_scan() blocking kswapd by waiting on IO
> completions while holding a mutex that other IO-level reclaim
> contexts require to make progress.
>
> Cheers,
>
> Dave.
The IO-level reclaim contexts should use GFP_NOIO. If the dm-bufio
shrinker is called with GFP_NOIO, it cannot be blocked by kswapd, because:
* it uses trylock to acquire the mutex
* it doesn't attempt to free buffers that are dirty or under I/O (see
__try_evict_buffer)
I think that this logic is sufficient to prevent the deadlock.
Mikulas
next prev parent reply other threads:[~2019-08-09 11:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-08 9:50 [PATCH] direct-io: use GFP_NOIO to avoid deadlock Mikulas Patocka
2019-08-08 13:53 ` Matthew Wilcox
2019-08-08 15:13 ` Mikulas Patocka
2019-08-08 15:17 ` [PATCH] loop: set PF_MEMALLOC_NOIO for the worker thread Mikulas Patocka
2019-08-08 16:12 ` Jens Axboe
2019-08-08 14:39 ` [PATCH] direct-io: use GFP_NOIO to avoid deadlock Junxiao Bi
2019-08-09 1:34 ` Dave Chinner
2019-08-09 11:30 ` Mikulas Patocka [this message]
2019-08-09 21:57 ` Dave Chinner
2019-08-13 16:35 ` Mikulas Patocka
2019-08-14 10:43 ` Dave Chinner
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