linux-kernel - Re: [linux-pm] Massive ext4 filesystem corruption after a failed s2disk/ram cycle

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Date:	Sun, 8 Nov 2009 19:29:05 +1100
From:	Dave Chinner <david@...morbit.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Daniel Pittman <daniel@...space.net>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	linux-pm@...ts.linux-foundation.org,
	Maxim Levitsky <maximlevitsky@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [linux-pm] Massive ext4 filesystem corruption after a failed
	s2disk/ram cycle

On Wed, Nov 04, 2009 at 11:18:05AM +0900, KOSAKI Motohiro wrote:
> > On Wed, Oct 07, 2009 at 01:14:10PM +1100, Daniel Pittman wrote:
> > > For what it is worth, I would also be quite interested to know
> > > /why/ XFS is bad in this regard.  Is it just the previously
> > > stated "XFS writes to disk despite freezing kernel threads"
> > > issue, or something deeper?
> > 
> > sync pushes out all data to disk, but in a journaling filesystem
> > that might just but the log not the "normal" place on disk.  For
> > a boot loader to deal with it properly it actually needs to do
> > an replay of the log.  Grub does so for reiserfs but not for XFS
> > for some reason.  I don't know why problems don't trigger more
> > often with ext3, though.
> 
> I'm sorry for the long delayed and offtopic responce. I discussed
> this issue with okuji-san (GRUB2 maintainer) at several month ago.
> He really wish linux implement real sync.
> 
> A bootloader has much constraint than OS (mainly caused by size
> constraint).  it can't implemnt jornal log replay logic for _all_
> filesystem.  Why can't we implement storong sync syscall? I don't
> think this is PM nor bootloader fault.

We already have an ioctl that does what you want: FIFREEZE.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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