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

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Message-ID: <Pine.LNX.4.44L0.1202011027150.1405-100000@iolanthe.rowland.org>
Date:	Wed, 1 Feb 2012 10:29:38 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pavel Machek <pavel@....cz>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	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

On Wed, 1 Feb 2012, Pavel Machek wrote:

> > 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.

I don't know about bootloaders, but from what I've heard, Linux fs
drivers (including those inside initrds) always replay the journal,
even if the filesystem is mounted read-only.  This could be considered
a bug in the filesystem code.

Alan Stern

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