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Re: [linux-lvm] 2.6.22-rc4 XFS fails after hibernate/resume

To: Pavel Machek <pavel@xxxxxx>
Subject: Re: [linux-lvm] 2.6.22-rc4 XFS fails after hibernate/resume
From: David Chinner <dgc@xxxxxxx>
Date: Fri, 29 Jun 2007 14:55:53 +1000
Cc: David Chinner <dgc@xxxxxxx>, David Greaves <david@xxxxxxxxxxxx>, David Robinson <zxvdr.au@xxxxxxxxx>, LVM general discussion and development <linux-lvm@xxxxxxxxxx>, "'linux-kernel@xxxxxxxxxxxxxxx'" <linux-kernel@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, linux-pm <linux-pm@xxxxxxxxxxxxxx>, LinuxRaid <linux-raid@xxxxxxxxxxxxxxx>
In-reply-to: <20070627204924.GA4777@xxxxxx>
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On Wed, Jun 27, 2007 at 08:49:24PM +0000, Pavel Machek wrote:
> Hi!
> 
> > FWIW, I'm on record stating that "sync" is not sufficient to quiesce an XFS
> > filesystem for a suspend/resume to work safely and have argued that the only
> 
> Hmm, so XFS writes to disk even when its threads are frozen?

They issue async I/O before they sleep and expects
processing to be done on I/O completion via workqueues.

> > safe thing to do is freeze the filesystem before suspend and thaw it after
> > resume. This is why I originally asked you to test that with the other 
> > problem
> 
> Could you add that to the XFS threads if it is really required? They
> do know that they are being frozen for suspend.

We don't suspend the threads on a filesystem freeze - they continue
run. A filesystem freeze guarantees the filesystem clean and that
the in memory state matches what is on disk. It is not possible for
the filesytem to issue I/O or have outstanding I/O when it is in the
frozen state, so the state of the threads and/or workqueues does not
matter because they will be idle.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group


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