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From: Mikulas Patocka <>
To: Dave Chinner <>
Cc: Alexander Viro <>,
	"Darrick J. Wong" <>,
	Mike Snitzer <>,,,
	Alasdair Kergon <>,,,,
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: <> (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 

I think that this logic is sufficient to prevent the deadlock.


  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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