ocfs2: Reset xattr value size after xa_cleanup_value_truncate().

In ocfs2_prepare_xattr_entry, if we fail to grow an existing value,
xa_cleanup_value_truncate() will leave the old entry in place.  Thus, we
reset its value size.  However, if we were allocating a new value, we
must not reset the value size or we will BUG().  This resolves
oss.oracle.com bug 1247.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

fs/ocfs2/xattr.c

@@ -2135,15 +2135,18 @@ static int ocfs2_xa_prepare_entry(struct ocfs2_xa_loc *loc,
 		orig_clusters = ocfs2_xa_value_clusters(loc);
 		rc = ocfs2_xa_value_truncate(loc, xi->xi_value_len, ctxt);
 		if (rc < 0) {
-			/*
-			 * If we tried to grow an existing external value,
-			 * ocfs2_xa_cleanuP-value_truncate() is going to
-			 * let it stand.  We have to restore its original
-			 * value size.
-			 */
-			loc->xl_entry->xe_value_size = orig_value_size;
 			ocfs2_xa_cleanup_value_truncate(loc, "growing",
 							orig_clusters);
+			/*
+			 * If we were growing an existing value,
+			 * ocfs2_xa_cleanup_value_truncate() won't remove
+			 * the entry. We need to restore the original value
+			 * size.
+			 */
+			if (loc->xl_entry) {
+				BUG_ON(!orig_value_size);
+				loc->xl_entry->xe_value_size = orig_value_size;
+			}
 			mlog_errno(rc);
 		}
 	}