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Re: [PATCH] Freeze bdevs when freezing processes.

To: David Chinner <dgc@xxxxxxx>
Subject: Re: [PATCH] Freeze bdevs when freezing processes.
From: Pavel Machek <pavel@xxxxxx>
Date: Wed, 25 Oct 2006 10:47:14 +0200
Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>, Nigel Cunningham <ncunningham@xxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20061025083830.GI11034@xxxxxxxxxxxxxxxxx>
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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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