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

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Date:	Sat, 7 Nov 2009 15:22:41 -0700
From:	Thomas Fjellstrom <tfjellstrom@...w.ca>
To:	linux-kernel@...r.kernel.org
Subject: Re: [linux-pm] Massive ext4 filesystem corruption after a failed s2disk/ram cycle

On Thu November 5 2009, Henrique de Moraes Holschuh wrote:
> On Wed, 04 Nov 2009, 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.
> 
> This is not about real sync.  It is about the box being able to reboot
>  after a crash or power failure.
> 
> GRUB2 is broken in that regard, at least in its peecee-BIOS version: 
>  last time I checked, it doesn't sort RAID components so that it won't
>  boot from failed or out-of-sync older components, it can't deal with
>  some of the filesystems being unclean...
> 
> > 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.
> 
> A bootloader that can't boot a system that went through an unclean
>  shutdown is quite broken.
> 

It can barely boot a system that's gone through a clean shutdown. "bios read 
error" and all that.

-- 
Thomas Fjellstrom
tfjellstrom@...w.ca
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