linux-kernel - Re: [PATCH] Freeze bdevs when freezing processes.

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Message-ID: <20061025084714.GA7266@elf.ucw.cz>
Date:	Wed, 25 Oct 2006 10:47:14 +0200
From:	Pavel Machek <pavel@....cz>
To:	David Chinner <dgc@....com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Nigel Cunningham <ncunningham@...uxmail.org>,
	Andrew Morton <akpm@...l.org>,
	LKML <linux-kernel@...r.kernel.org>, xfs@....sgi.com
Subject: Re: [PATCH] Freeze bdevs when freezing processes.

On Wed 2006-10-25 18:38:30, David Chinner wrote:
> On Wed, Oct 25, 2006 at 10:10:01AM +0200, Pavel Machek wrote:
> > > Hence the only way to correctly rebuild the XFS state on resume is
> > > to quiesce the filesystem on suspend and thaw it on resume so as to
> > > trigger log recovery.
> > 
> > No, during suspend/resume, memory image is saved, and no state is
> > lost. We would not even have to do sys_sync(), and suspend/resume
> > would still work properly.
> 
> It seems to me that you ensure the filesystem is synced to disk and
> then at some point later you record the memory state of the
> filesystem, but these happen at different times. That leaves a
> window for things to get out of sync again, right?

I DO NOT HAVE TO ENSURE FILESYSTEM IS SYNCED. That sys_sync() is
optional.

Recording of memory state is atomic, and as long as noone writes to
the disk after atomic snapshot, memory image matches what is on disk.

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