Review: xfs_bmapi does not update previous extent pointer correctly

Review: xfs_bmapi does not update previous extent pointer correctly

[David Chinner]

When looping across multiple extents, xfs_bmapi will fail to
update the previous extent pointer which is used in subsequent
loops.

As a result, we can end up with the second loop in xfs_bmapi trying
to use an incorrect previous extent pointer and assert failures or
corrupted in-memory extent lists will result.

Correctly update the previous extent at the end of each loop so that
we DTRT when processing multiple map requests.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group

---
 fs/xfs/xfs_bmap.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Index: 2.6.x-xfs-new/fs/xfs/xfs_bmap.c
===================================================================
--- 2.6.x-xfs-new.orig/fs/xfs/xfs_bmap.c	2007-05-23 16:33:00.000000000 +1000
+++ 2.6.x-xfs-new/fs/xfs/xfs_bmap.c	2007-05-25 11:53:31.949847746 +1000
@@ -5575,10 +5575,10 @@ xfs_bmapi(
 		 * Else go on to the next record.
 		 */
 		ep = xfs_iext_get_ext(ifp, ++lastx);
-		if (lastx >= nextents) {
+		prev = got;
+		if (lastx >= nextents)
 			eof = 1;
-			prev = got;
-		} else
+		else
 			xfs_bmbt_get_all(ep, &got);
 	}
 	ifp->if_lastex = lastx;

Re: Review: xfs_bmapi does not update previous extent pointer correctly

[Vlad Apostolov]

It is looking good Dave,

Regards,
Vlad

David Chinner wrote:
> When looping across multiple extents, xfs_bmapi will fail to
> update the previous extent pointer which is used in subsequent
> loops.
>
> As a result, we can end up with the second loop in xfs_bmapi trying
> to use an incorrect previous extent pointer and assert failures or
> corrupted in-memory extent lists will result.
>
> Correctly update the previous extent at the end of each loop so that
> we DTRT when processing multiple map requests.
>
> Cheers,
>
> Dave.
>