From: Sunil Mushran <sunil.mushran@oracle.com>
Date: Fri, 4 Sep 2009 18:12:01 +0000 (-0700)
Subject: ocfs2: ocfs2_write_begin_nolock() should handle len=0
X-Git-Tag: v2.6.30.6~1
X-Git-Url: https://git.fsl.cs.sunysb.edu/?a=commitdiff_plain;h=e38d22518cad8f3e1805bf17482b8bd2a5ec7de0;p=unionfs-2.6.39.y.git

ocfs2: ocfs2_write_begin_nolock() should handle len=0

commit 8379e7c46cc48f51197dd663fc6676f47f2a1e71 upstream.

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>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 122fb7978f6..044990a4785 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1746,8 +1746,8 @@ 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;