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Re: [PATCH v2] xfs: Fix rounding in xfs_alloc_fix_len()

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: [PATCH v2] xfs: Fix rounding in xfs_alloc_fix_len()
From: Jan Kara <jack@xxxxxxx>
Date: Fri, 13 Jun 2014 17:02:07 +0200
Cc: Jan Kara <jack@xxxxxxx>, xfs@xxxxxxxxxxx, dchinner@xxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140604184440.GC55624@xxxxxxxxxxxxxxx>
References: <1401900833-25485-1-git-send-email-jack@xxxxxxx> <20140604184440.GC55624@xxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed 04-06-14 14:44:40, Brian Foster wrote:
> On Wed, Jun 04, 2014 at 06:53:53PM +0200, Jan Kara wrote:
> > Rounding in xfs_alloc_fix_len() is wrong. As the comment states, the
> > result should be a number of a form (k*prod+mod) however due to sign
> > mistake the result is different. As a result allocations on raid arrays
> > could be misaligned in some cases.
> > 
> > This also seems to fix occasional assertion failure:
> >     XFS_WANT_CORRUPTED_GOTO(rlen <= flen, error0)
> > in xfs_alloc_ag_vextent_size().
> > 
> > Also add an assertion that the result of xfs_alloc_fix_len() is of
> > expected form.
> > 
> > Signed-off-by: Jan Kara <jack@xxxxxxx>
> > ---
> 
> Looks good to me. Thanks Jan.
> 
> Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
  Ping Dave? Are you going to pick up this patch?

                                                        Honza
 
> >  fs/xfs/xfs_alloc.c | 18 ++++++++----------
> >  1 file changed, 8 insertions(+), 10 deletions(-)
> > 
> > diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
> > index c1cf6a336a72..1351a24d3cdc 100644
> > --- a/fs/xfs/xfs_alloc.c
> > +++ b/fs/xfs/xfs_alloc.c
> > @@ -257,16 +257,14 @@ xfs_alloc_fix_len(
> >     k = rlen % args->prod;
> >     if (k == args->mod)
> >             return;
> > -   if (k > args->mod) {
> > -           if ((int)(rlen = rlen - k - args->mod) < (int)args->minlen)
> > -                   return;
> > -   } else {
> > -           if ((int)(rlen = rlen - args->prod - (args->mod - k)) <
> > -               (int)args->minlen)
> > -                   return;
> > -   }
> > -   ASSERT(rlen >= args->minlen);
> > -   ASSERT(rlen <= args->maxlen);
> > +   if (k > args->mod)
> > +           rlen = rlen - (k - args->mod);
> > +   else
> > +           rlen = rlen - args->prod + (args->mod - k);
> > +   if ((int)rlen < (int)args->minlen)
> > +           return;
> > +   ASSERT(rlen >= args->minlen && rlen <= args->maxlen);
> > +   ASSERT(rlen % args->prod == args->mod);
> >     args->len = rlen;
> >  }
> >  
> > -- 
> > 1.8.1.4
> > 
> > _______________________________________________
> > xfs mailing list
> > xfs@xxxxxxxxxxx
> > http://oss.sgi.com/mailman/listinfo/xfs
-- 
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR

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