[dm-devel] Re: [PATCH 2.6.19 5/5] fs: freeze_bdev with semaphore not mutex

[Pavel Machek <pavel suse cz>]

Hi!

> > Okay, so you claim that sys_sync can stall, waiting for administator?
> > 
> > In such case we can simply do one sys_sync() before we start freezing
> > userspace... or just more the only sys_sync() there. That way, admin
> > has chance to unlock his system.
> 
> Well, this is a different story.
> 
> My point is that if we call sys_sync() _anyway_ before calling
> freeze_filesystems(), then freeze_filesystems() is _safe_ (either the
> sys_sync() blocks, or it doesn't in which case freeze_filesystems() won't
> block either).
> 
> This means, however, that we can leave the patch as is (well, with the minor
> fix I have already posted), for now, because it doesn't make things worse a
> bit, but:
> (a) it prevents xfs from being corrupted and

I'd really prefer it to be fixed by 'freezeable workqueues'. Can you
point me into sources -- which xfs workqueues are problematic?

(It would be nice to fix that for 2.6.19, and full bdev freezing looks
intrusive to me).

> (b) it prevents journaling filesystems in general from replaying journals
> after a failing resume.

I do not see b) as an useful goal.
							Pavel

-- 
Thanks for all the (sleeping) penguins.