linux-kernel - Re: [RFC][PATCH] PM / Sleep: Freeze filesystems during system suspend/hibernation

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Message-ID: <20120201133642.GC3673@elf.ucw.cz>
Date:	Wed, 1 Feb 2012 14:36:42 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>,
	linux-fsdevel@...r.kernel.org, Dave Chinner <david@...morbit.com>,
	Nigel Cunningham <nigel@...onice.net>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: Re: [RFC][PATCH] PM / Sleep: Freeze filesystems during system
 suspend/hibernation

Hi!

> From: Rafael J. Wysocki <rjw@...k.pl>
> 
> Freeze all filesystems during system suspend and (kernel-driven)
> hibernation by calling freeze_supers() for all superblocks and thaw
> them during the subsequent resume with the help of thaw_supers().
> 
> This makes filesystems stay in a consistent state in case something
> goes wrong between system suspend (or hibernation) and the subsequent
> resume (e.g. journal replays won't be necessary in those cases).  In

Good.

> particular, this should help to solve a long-standing issue that, in
> some cases, during resume from hibernation the boot loader causes the
> journal to be replied for the filesystem containing the kernel image
> and/or initrd causing it to become inconsistent with the information
> stored in the hibernation image.

Ungood. Why is bootloader/initrd doing that? If it mounts filesystem
read/write, what is the guarantee that it will not change data on the
filesystem, breaking stuff?

Bootloaders should just not replay journals.

> The user-space-driven hibernation (s2disk) is not covered by this
> change, because the freezing of filesystems prevents s2disk from
> accessing device special files it needs to do its job.

...so bootloaders need to be fixed, anyway.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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