From: Richard Weinberger <richard.weinberger@gmail.com>
To: Kyeong Yoo <Kyeong.Yoo@alliedtelesis.co.nz>
Cc: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>
Subject: Re: [PATCH] jffs2: GC deadlock reading a page that is used in jffs2_write_begin()
Date: Tue, 18 Jul 2017 09:17:26 +0200 [thread overview]
Message-ID: <CAFLxGvwAJ+xfN=1QGfe_6mNksmMr6cTjSSRKPqYGKMi-1zvU2Q@mail.gmail.com> (raw)
In-Reply-To: <7e0d37e6-c3de-5c17-72e1-f6003e5d7d4a@alliedtelesis.co.nz>
Kyeong Yoo,
On Mon, Jul 17, 2017 at 11:54 PM, Kyeong Yoo
<Kyeong.Yoo@alliedtelesis.co.nz> wrote:
> Hi,
>
> Can someone review this and give me any feedback?
>
> This patch is to prevent deadlock in jffs2 GC.
>
> Thanks,
> Kyeong
>
>
> On 04/07/17 16:22, Kyeong Yoo wrote:
>> GC task can deadlock in read_cache_page() because it may attempt
>> to release a page that is actually allocated by another task in
>> jffs2_write_begin().
>> The reason is that in jffs2_write_begin() there is a small window
>> a cache page is allocated for use but not set Uptodate yet.
>>
>> This ends up with a deadlock between two tasks:
>> 1) A task (e.g. file copy)
>> - jffs2_write_begin() locks a cache page
>> - jffs2_write_end() tries to lock "alloc_sem" from
>> jffs2_reserve_space() <-- STUCK
>> 2) GC task (jffs2_gcd_mtd3)
>> - jffs2_garbage_collect_pass() locks "alloc_sem"
>> - try to lock the same cache page in read_cache_page() <-- STUCK
Your description does not match the code. Are you seeing this on a
recent mainline kernel?
Can t be that your kernel does not has this commit?
commit 157078f64b8a9cd7011b6b900b2f2498df850748
Author: Thomas Betker <thomas.betker@rohde-schwarz.com>
Date: Tue Nov 10 22:18:15 2015 +0100
Revert "jffs2: Fix lock acquisition order bug in jffs2_write_begin"
This reverts commit 5ffd3412ae55
("jffs2: Fix lock acquisition order bug in jffs2_write_begin").
--
Thanks,
//richard
next prev parent reply other threads:[~2017-07-18 7:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-04 4:22 [PATCH] jffs2: GC deadlock reading a page that is used in jffs2_write_begin() Kyeong Yoo
2017-07-17 21:54 ` Kyeong Yoo
2017-07-18 7:17 ` Richard Weinberger [this message]
2017-07-18 23:00 ` Kyeong Yoo
2018-12-15 22:37 ` Richard Weinberger
2019-01-25 6:30 ` Hou Tao
2020-05-20 0:00 ` Hamish Martin
2020-05-25 19:45 ` Richard Weinberger
2020-06-02 21:00 ` Richard Weinberger
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