xfs: distinguish extra split from real ENOSPC from xfs_attr_node_try_addname

Just like xfs_attr3_leaf_split, xfs_attr_node_try_addname can return
-ENOSPC both for an actual failure to allocate a disk block, but also
to signal the caller to convert the format of the attr fork.  Use magic
1 to ask for the conversion here as well.

Note that unlike the similar issue in xfs_attr3_leaf_split, this one was
only found by code review.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

fs/xfs/libxfs/xfs_attr.c

@@ -597,7 +597,7 @@ xfs_attr_node_addname(
 		return error;
 
 	error = xfs_attr_node_try_addname(attr);
-	if (error == -ENOSPC) {
+	if (error == 1) {
 		error = xfs_attr3_leaf_to_node(args);
 		if (error)
 			return error;
@@ -1386,9 +1386,12 @@ xfs_attr_node_addname_find_attr(
 /*
  * Add a name to a Btree-format attribute list.
  *
- * This will involve walking down the Btree, and may involve splitting
- * leaf nodes and even splitting intermediate nodes up to and including
- * the root node (a special case of an intermediate node).
+ * This will involve walking down the Btree, and may involve splitting leaf
+ * nodes and even splitting intermediate nodes up to and including the root
+ * node (a special case of an intermediate node).
+ *
+ * If the tree was still in single leaf format and needs to converted to
+ * real node format return 1 and let the caller handle that.
  */
 static int
 xfs_attr_node_try_addname(
@@ -1410,7 +1413,7 @@ xfs_attr_node_try_addname(
 			 * out-of-line values so it looked like it *might*
 			 * have been a b-tree. Let the caller deal with this.
 			 */
-			error = -ENOSPC;
+			error = 1;
 			goto out;
 		}