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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: "Rafael J. Wysocki" <rjw@xxxxxxx>
Date: Tue, 24 Oct 2006 17:29:59 +0200
Cc: Nigel Cunningham <ncunningham@xxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, Pavel Machek <pavel@xxxxxx>, xfs@xxxxxxxxxxx
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References: <1161576735.3466.7.camel@xxxxxxxxxxxxxxxxxx> <200610231236.54317.rjw@xxxxxxx> <20061024144446.GD11034@xxxxxxxxxxxxxxxxx>
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On Tuesday, 24 October 2006 16:44, David Chinner wrote:
> On Mon, Oct 23, 2006 at 12:36:53PM +0200, Rafael J. Wysocki wrote:
> > On Monday, 23 October 2006 06:12, Nigel Cunningham wrote:
> > > XFS can continue to submit I/O from a timer routine, even after
> > > freezeable kernel and userspace threads are frozen. This doesn't seem to
> > > be an issue for current swsusp code,
> > 
> > So it doesn't look like we need the patch _now_.
> > 
> > > but is definitely an issue for Suspend2, where the pages being written 
> > > could
> > > be overwritten by Suspend2's atomic copy.
> > 
> > And IMO that's a good reason why we shouldn't use RCU pages for storing the
> > image.  XFS is one known example that breaks things if we do so and
> > there may be more such things that we don't know of.  The fact that they
> > haven't appeared in testing so far doesn't mean they don't exist and
> > moreover some things like that may appear in the future.
> Could you please tell us which XFS bits are broken so we can get
> them fixed?  The XFS daemons should all be checking if they are
> supposed to freeze (i.e. they call try_to_freeze() after they wake
> up due to timer expiry) so I thought they were doing the right
> thing.
> However, I have to say that I agree with freezing the filesystems
> before suspend - at least XFS will be in a consistent state that can
> be recovered from without corruption if your machine fails to
> resume....

Do you mean calling sys_sync() after the userspace has been frozen
may not be sufficient?


You never change things by fighting the existing reality.
                R. Buckminster Fuller

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