ocfs2: Fix check of return value of ocfs2_start_trans() in xattr.c.

On failure, ocfs2_start_trans() returns values like ERR_PTR(-ENOMEM),
so we should check whether handle is NULL. Fix them to use IS_ERR().
Jan has made the patch for other part in ocfs2(thank Jan for it), so
this is just the fix for fs/ocfs2/xattr.c.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

fs/ocfs2/xattr.c

@@ -4092,7 +4092,7 @@ static int ocfs2_xattr_value_update_size(struct inode *inode,
 	handle_t *handle = NULL;
 
 	handle = ocfs2_start_trans(osb, 1);
-	if (handle == NULL) {
+	if (IS_ERR(handle)) {
 		ret = -ENOMEM;
 		mlog_errno(ret);
 		goto out;
@@ -4259,7 +4259,7 @@ static int ocfs2_rm_xattr_cluster(struct inode *inode,
 	}
 
 	handle = ocfs2_start_trans(osb, OCFS2_REMOVE_EXTENT_CREDITS);
-	if (handle == NULL) {
+	if (IS_ERR(handle)) {
 		ret = -ENOMEM;
 		mlog_errno(ret);
 		goto out;