linux-kernel - Re: [PATCH] f2fs: avoid the deadlock case when stopping discard thread

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Message-Id: <20240322113357.2599-1-hdanton@sina.com>
Date: Fri, 22 Mar 2024 19:33:57 +0800
From: Hillf Danton <hdanton@...a.com>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	Light Hsieh (謝明燈) <Light.Hsieh@...iatek.com>,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH] f2fs: avoid the deadlock case when stopping discard thread

On Thu, 21 Mar 2024 17:29:03 -0700 Jaegeuk Kim <jaegeuk@...nel.org>
> 
> I posted this patch before Light reported.

Yeah, his report's timestamp is 2024-03-20  6:59, nearly 7 hours later,
which shows that you constructed the deadlock with nothing to do with
his report.
> 
> And, in the report, I didn't get this:
> 
> f2fs_ioc_shutdown() --> freeze_bdev() --> freeze_super() --> sb_wait_write(sb, SB_FREEZE_FS) --> ... ->percpu_down_write().
> 
> because f2fs_ioc_shutdown() calls f2fs_stop_discard_thread() after thaw_bdev()
> like this order.
> 
>  -> freeze_bdev()
>  -> thaw_bdev()
>  -> f2fs_stop_discard_thread()
> 
> Am I missing something?

Light, could you specify to help Jaegeuk understand the deadlock you reported?