ocfs2: ocfs2_write_begin_nolock() should handle len=0

Bug introduced by mainline commit e7432675f8ca868a4af365759a8d4c3779a3d922
The bug causes ocfs2_write_begin_nolock() to oops when len=0.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Cc: stable@kernel.org
Signed-off-by: Joel Becker <joel.becker@oracle.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index b401654011a2..8a1e61545f41 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1747,8 +1747,8 @@ int ocfs2_write_begin_nolock(struct address_space *mapping,
          * we know zeros will only be needed in the first and/or last cluster.
          */
         if (clusters_to_alloc || extents_to_split ||
-            wc->w_desc[0].c_needs_zero ||
-            wc->w_desc[wc->w_clen - 1].c_needs_zero)
+            (wc->w_clen && (wc->w_desc[0].c_needs_zero ||
+                            wc->w_desc[wc->w_clen - 1].c_needs_zero)))
                 cluster_of_pages = 1;
         else
                 cluster_of_pages = 0;