linux-ext4 - Re: + fs-introduce-write_begin-write_end-and-perform

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Message-ID: <20070614103903.GA6703@wotan.suse.de>
Date:	Thu, 14 Jun 2007 12:39:03 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Jan Kara <jack@...e.cz>
Cc:	Badari Pulavarty <pbadari@...il.com>,
	lkml <linux-kernel@...r.kernel.org>, mark.fasheh@...cle.com,
	ext4 <linux-ext4@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, cmm@...ibm.com
Subject: Re: + fs-introduce-write_begin-write_end-and-perform_write-aops.patch added to -mm tree

On Thu, Jun 14, 2007 at 11:52:49AM +0200, Jan Kara wrote:
> > On Wed, 2007-06-13 at 13:43 +0200, Nick Piggin wrote:
> > ..
> > >  
> > > > 5) ext3_write_end:
> > > > 	Before  write_begin/write_end patch set we have folowing locking
> > > > 	order:
> > > > 		stop_journal(handle);
> > > > 		unlock_page(page);
> > > > 	But now order is oposite:
> > > > 		unlock_page(page);
> > > > 		stop_journal(handle);
> > > > 	Can we got any race condition now? I'm not sure is it actual problem,
> > > > 	may be somebody cant describe this.
> > > 
> > > Can we just change it to the original order? That would seem to be
> > > safest unless one of the ext3 devs explicitly acks it.
>   Sorry, I've missed beginning of this thread. But what problems can
> exactly cause this ordering change? ext3_journal_stop has no need to be
> protected by the page lock - it can be even better that it's not
> protected as it can trigger commit and all that would happen
> unnecessarily under page lock...

Sure, if you think it is safe. I would rather it be done in a
different patch though.

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