linux-kernel - Re: [PATCH] Fix sysrq emergency thaw

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Message-ID: <20160805201447.GC7999@amd>
Date:	Fri, 5 Aug 2016 22:14:47 +0200
From:	Pavel Machek <pavel@....cz>
To:	Charles Gong <cggong@...com>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...com, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] Fix sysrq emergency thaw

On Wed 2016-07-20 16:11:16, Charles Gong wrote:
> "SYSRQ + J" triggers a call to emergency_thaw_all(). Currently, this
> is an infinite loop. Once we trigger it, we'll need to do a hard
> power-cycle. There are users reporting this bug from 2012 to 2016, for
> example, at https://bugzilla.kernel.org/show_bug.cgi?id=47741.
> 
> This happens because thaw_bdev() fails to return -EINVAL in the
> non-frozen case, so fix it so that do_one_thaw() can recognize this case
> and quit from looping. I checked that none of the other thaw_bdev()
> callers check the return value.
> 
> The regression was introduced in commit 4504230a7156 ("freeze_bdev: grab
> active reference to frozen superblocks").
> 
> Reviewed-by: Chris Mason <clm@...com>
> Signed-off-by: Charles Gong <cggong@...com>

Acked-by: Pavel Machek <pavel@....cz>

(even magic should be finite...)
-- 
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