linux-kernel - Re: [PATCH 2.6.19 5/5] fs: freeze

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Message-Id: <200611091652.34649.rjw@sisk.pl>
Date:	Thu, 9 Nov 2006 16:52:33 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Pavel Machek <pavel@....cz>
Cc:	Alasdair G Kergon <agk@...hat.com>,
	Eric Sandeen <sandeen@...hat.com>,
	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com, Srinivasa DS <srinivasa@...ibm.com>,
	Nigel Cunningham <nigel@...pend2.net>,
	David Chinner <dgc@....com>
Subject: Re: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex

Hi,

On Wednesday, 8 November 2006 19:09, Pavel Machek wrote:
> Hi!
> 
> > > swsusp-freeze-filesystems-during-suspend-rev-2.patch
> > > 
> > > I think you need to give more thought to device-mapper
> > > interactions here.  If an underlying device is suspended
> > > by device-mapper without freezing the filesystem (the
> > > normal state) and you issue a freeze_bdev on a device
> > > above it, the freeze_bdev may never return if it attempts
> > > any synchronous I/O (as it should).
> > 
> > Well, it looks like the interactions with dm add quite a bit of
> > complexity here.
> 
> What about just fixing xfs (thou shall not write to disk when kernel
> threads are frozen), and getting rid of blockdev freezing?

Well, first I must admit you were absolutely right being suspicious with
respect to this stuff.

OTOH I have no idea _how_ we can tell xfs that the processes have been
frozen.  Should we introduce a global flag for that or something?

Rafael


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