From: Mikulas Patocka <mpatocka@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
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: Thu, 8 Aug 2019 11:13:50 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.1908081112580.18950@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <20190808135329.GG5482@bombadil.infradead.org>
On Thu, 8 Aug 2019, Matthew Wilcox wrote:
> On Thu, Aug 08, 2019 at 05:50:10AM -0400, Mikulas Patocka wrote:
> > A deadlock with this stacktrace was observed.
> >
> > The obvious problem here is that in the call chain
> > xfs_vm_direct_IO->__blockdev_direct_IO->do_blockdev_direct_IO->kmem_cache_alloc
> > we do a GFP_KERNEL allocation while we are in a filesystem driver and in a
> > block device driver.
>
> But that's not the problem. The problem is the loop driver calls into the
> filesystem without calling memalloc_noio_save() / memalloc_noio_restore().
> There are dozens of places in XFS which use GFP_KERNEL allocations and
> all can trigger this same problem if called from the loop driver.
OK. I'll send a new patch that sets PF_MEMALLOC_NOIO in the loop driver.
Mikulas
next prev parent reply other threads:[~2019-08-08 15:14 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 [this message]
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
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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