From f1c63b73cf60dc4800cde5ce7fd9466c419e5e36 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@infradead.org>
Date: Wed, 11 May 2011 15:04:09 +0000
Subject: [PATCH] xfs: do not do pointer arithmetic on extent records

We need to call xfs_iext_get_ext for the previous extent to get a
valid pointer, and can't just do pointer arithmetics as they might
be in different pages.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Lachlan McIlroy <lmcilroy@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>
---
 fs/xfs/xfs_bmap.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index ebcd45203c3d..896e16f08ed9 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -5143,9 +5143,12 @@ xfs_bunmapi(
 				 */
 				ASSERT(bno >= del.br_blockcount);
 				bno -= del.br_blockcount;
-				if (bno < got.br_startoff) {
-					if (--lastx >= 0)
-						xfs_bmbt_get_all(--ep, &got);
+				if (got.br_startoff > bno) {
+					if (--lastx >= 0) {
+						ep = xfs_iext_get_ext(ifp,
+								      lastx);
+						xfs_bmbt_get_all(ep, &got);
+					}
 				}
 				continue;
 			} else if (del.br_state == XFS_EXT_UNWRITTEN) {