Btrfs: return ENOSPC when target space is full

In extent-tree.c:do_chunk_alloc(), early on we returned 0 (success)
when the target space was full and when chunk allocation is needed.
However, later on in that same function we return ENOSPC if
btrfs_alloc_chunk() fails (and chunk allocation was needed) and
set the space's full flag.

This was inconsistent, as -ENOSPC should be returned if the space
is full and a chunk allocation needs to performed. If the space is
full but no chunk allocation is needed, just return 0 (success).

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

fs/btrfs/extent-tree.c

@@ -3836,8 +3836,12 @@ again:
 	if (force < space_info->force_alloc)
 		force = space_info->force_alloc;
 	if (space_info->full) {
+		if (should_alloc_chunk(extent_root, space_info, force))
+			ret = -ENOSPC;
+		else
+			ret = 0;
 		spin_unlock(&space_info->lock);
-		return 0;
+		return ret;
 	}
 
 	if (!should_alloc_chunk(extent_root, space_info, force)) {