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

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Message-ID: <20070629045553.GN31489@sgi.com>
Date:	Fri, 29 Jun 2007 14:55:53 +1000
From:	David Chinner <dgc@....com>
To:	Pavel Machek <pavel@....cz>
Cc:	David Chinner <dgc@....com>, David Greaves <david@...eaves.com>,
	David Robinson <zxvdr.au@...il.com>,
	LVM general discussion and development 
	<linux-lvm@...hat.com>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	xfs@....sgi.com, linux-pm <linux-pm@...ts.osdl.org>,
	LinuxRaid <linux-raid@...r.kernel.org>
Subject: Re: [linux-lvm] 2.6.22-rc4 XFS fails after hibernate/resume

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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