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>

1 files 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) {