linux-kernel - Re: [PATCH 3.16 102/305] xfs: xfs_iflush

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Message-ID: <20160817020248.GE2031@devil.localdomain>
Date:	Wed, 17 Aug 2016 12:02:48 +1000
From:	Dave Chinner <dchinner@...hat.com>
To:	Ben Hutchings <ben@...adent.org.uk>
Cc:	Dave Chinner <david@...morbit.com>, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, akpm@...ux-foundation.org,
	Christoph Hellwig <hch@....de>,
	Shyam Kaushik <shyam@...arastorage.com>
Subject: Re: [PATCH 3.16 102/305] xfs: xfs_iflush_cluster fails to abort on
 error

On Tue, Aug 16, 2016 at 08:45:02PM +0100, Ben Hutchings wrote:
> On Sun, 2016-08-14 at 09:36 +1000, Dave Chinner wrote:
> > On Sat, Aug 13, 2016 at 06:42:51PM +0100, Ben Hutchings wrote:
> > > 
> > > 3.16.37-rc1 review patch.  If anyone has any objections, please let me know.
> > > 
> > > ------------------
> > > 
> > > > > From: Dave Chinner <dchinner@...hat.com>
> > > 
> > > commit b1438f477934f5a4d5a44df26f3079a7575d5946 upstream.
> > > 
> > > When a failure due to an inode buffer occurs, the error handling
> > > fails to abort the inode writeback correctly. This can result in the
> > > inode being reclaimed whilst still in the AIL, leading to
> > > use-after-free situations as well as filesystems that cannot be
> > > unmounted as the inode log items left in the AIL never get removed.
> > > 
> > > Fix this by ensuring fatal errors from xfs_imap_to_bp() result in
> > > the inode flush being aborted correctly.
> > ....
> > > 
> > >  
> > > > >  	/*
> > > > > -	 * Get the buffer containing the on-disk inode.
> > > > > +	 * Get the buffer containing the on-disk inode. We are doing a try-lock
> > > > > +	 * operation here, so we may get  an EAGAIN error. In that case, we
> > > > > +	 * simply want to return with the inode still dirty.
> > > > > +	 *
> > > > > +	 * If we get any other error, we effectively have a corruption situation
> > > > > +	 * and we cannot flush the inode, so we treat it the same as failing
> > > > > +	 * xfs_iflush_int().
> > > > >  	 */
> > > > >  	error = xfs_imap_to_bp(mp, NULL, &ip->i_imap, &dip, &bp, XBF_TRYLOCK,
> > > > >  			       0);
> > > > > -	if (error || !bp) {
> > > > > +	if (error == -EAGAIN) {
> > 
> > Wrong. As was pointed out for other -stable trees after users
> > reported regressions, the error signs in XFS changed from positive
> > to negative in 3.17-rc1.
> 
> OK, so do I just need to delete the minus sign there?

Yes.

-Dave.
-- 
Dave Chinner
dchinner@...hat.com