Re: [PATCH] Fix sysrq emergency thaw

From	Pavel Machek <pavel@ucw.cz>
Newsgroups	linux.kernel
Subject	Re: [PATCH] Fix sysrq emergency thaw
Date	2016-08-05 22:20 +0200
Message-ID	<s2TL3-3TQ-1@gated-at.bofh.it> (permalink)
References	<rX8Wu-7Sc-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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@fb.com>
> Signed-off-by: Charles Gong <cggong@fb.com>

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

(even magic should be finite...)
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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Re: [PATCH] Fix sysrq emergency thaw Pavel Machek <pavel@ucw.cz> - 2016-08-05 22:20 +0200

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