linux-kernel - Re: [PATCH 1/5] fsfreeze: Prevent emergency thaw from looping infinitely

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Date:	Tue, 15 Jun 2010 09:19:43 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	viro@...IV.linux.org.uk, josef@...hat.com, jeffmerkey@...il.com
Subject: Re: [PATCH 1/5] fsfreeze: Prevent emergency thaw from looping
 infinitely

On Mon, Jun 14, 2010 at 11:18:15AM -0400, Christoph Hellwig wrote:
> On Thu, Jun 10, 2010 at 05:19:50PM +1000, Dave Chinner wrote:
> > Return -EINVAL when the filesystem is already unfrozen to avoid this
> > problem.
> 
> 
> This includes some additional changes in addition to the description,
> and at least one of them seems incorrect.
> 
> > -	error = 0;
> > -	if (--bdev->bd_fsfreeze_count > 0)
> > +	if (!sb)
> >  		goto out;
> >  
> > -	if (!sb)
> > +	error = 0;
> > +	if (--bdev->bd_fsfreeze_count > 0)
> >  		goto out;
> 
> Here you reorder the sb check to be before the counter decrement.  But
> we do support calling freeze_bdev on a device without a superblock, and
> you would leak bd_fsfreeze_count for that case and wrongly return
> -EINVAL on unthaw for these now.

Ok, will fix it.

Cheers,

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