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

Dave Chinner
2009-11-08T08:29:06Z

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@fromorbit.com