From: Guoqing Jiang <guoqing.jiang@linux.dev>
To: Donald Buczek <buczek@molgen.mpg.de>,
Paul Menzel <pmenzel@molgen.mpg.de>,
song@kernel.org
Cc: agk@redhat.com, snitzer@redhat.com, linux-raid@vger.kernel.org,
dm-devel@redhat.com, it+raid@molgen.mpg.de
Subject: Re: [PATCH V2] md: don't unregister sync_thread with reconfig_mutex held
Date: Fri, 10 Dec 2021 09:06:57 +0800 [thread overview]
Message-ID: <43ae2d60-4f28-07ea-95dc-ae722ca13b23@linux.dev> (raw)
In-Reply-To: <2cefad59-c0fc-d48f-f7a5-5d593931feb7@molgen.mpg.de>
On 12/9/21 8:57 PM, Donald Buczek wrote:
> [Update Guoqing’s email address]
>
> On 15.02.21 12:07, Paul Menzel wrote:
>> [+cc Donald]
>>
>> Am 13.02.21 um 01:49 schrieb Guoqing Jiang:
>>> Unregister sync_thread doesn't need to hold reconfig_mutex since it
>>> doesn't reconfigure array.
>>>
>>> And it could cause deadlock problem for raid5 as follows:
>>>
>>> 1. process A tried to reap sync thread with reconfig_mutex held
>>> after echo
>>> idle to sync_action.
>>> 2. raid5 sync thread was blocked if there were too many active stripes.
>>> 3. SB_CHANGE_PENDING was set (because of write IO comes from upper
>>> layer)
>>> which causes the number of active stripes can't be decreased.
>>> 4. SB_CHANGE_PENDING can't be cleared since md_check_recovery was
>>> not able
>>> to hold reconfig_mutex.
>>>
>>> More details in the link:
>>> https://lore.kernel.org/linux-raid/5ed54ffc-ce82-bf66-4eff-390cb23bc1ac@molgen.mpg.de/T/#t
>>>
>>>
>>> And add one parameter to md_reap_sync_thread since it could be
>>> called by
>>> dm-raid which doesn't hold reconfig_mutex.
>>>
>>> Reported-and-tested-by: Donald Buczek <buczek@molgen.mpg.de>
>
> Thanks, Paul, for putting me into the cc.
>
> Guoqing, I don't think, I've tested this patch. Please remove the
> tested-by.
This version is basically the similar as the change in the thread.
https://lore.kernel.org/linux-raid/5ed54ffc-ce82-bf66-4eff-390cb23bc1ac@molgen.mpg.de/T/#m546d8c55a42f308985b9d31d4be85832edcd15ab
Anyway, I will remove your tested-by per the request if I will update
the patch.
Thanks,
Guoqing
next prev parent reply other threads:[~2021-12-10 1:07 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-13 0:49 [PATCH V2] md: don't unregister sync_thread with reconfig_mutex held Guoqing Jiang
2021-02-15 11:07 ` Paul Menzel
2021-02-24 9:09 ` Song Liu
2021-02-24 9:25 ` Guoqing Jiang
2021-03-19 23:00 ` Song Liu
2021-11-30 17:25 ` Paul Menzel
2021-11-30 17:27 ` Paul Menzel
2021-12-08 14:16 ` Guoqing Jiang
[not found] ` <CAM23VxrYRbWEUsCsez2QOQM9oWKxSv432rc9oZCj5zEPmtND0A@mail.gmail.com>
2021-12-09 0:47 ` Guoqing Jiang
2021-12-09 12:54 ` Donald Buczek
2021-12-09 12:57 ` Donald Buczek
2021-12-10 1:06 ` Guoqing Jiang [this message]
2021-12-10 14:16 ` Donald Buczek
2021-12-14 2:34 ` Guoqing Jiang
2021-12-14 9:31 ` Donald Buczek
2021-12-14 10:03 ` Guoqing Jiang
2021-12-14 12:21 ` Donald Buczek
2022-01-11 12:25 ` Mikko Rantalainen
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