Btrfs: add missing error code to BTRFS_IOC_INO_LOOKUP handler

If the path doesn't fit in the input buffer, return ENAMETOOLONG
instead of returning with a success code (0) and a partially
filled and right justified buffer.

Also removed useless buffer pointer check outside the while loop.
Signed-off-by: NFilipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: NJosef Bacik <jbacik@fusionio.com>
Signed-off-by: NChris Mason <chris.mason@fusionio.com>

fs/btrfs/ioctl.c

@@ -2030,8 +2030,10 @@ static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info,
 		len = btrfs_inode_ref_name_len(l, iref);
 		ptr -= len + 1;
 		total_len += len + 1;
-		if (ptr < name)
+		if (ptr < name) {
+			ret = -ENAMETOOLONG;
 			goto out;
+		}
 
 		*(ptr + len) = '/';
 		read_extent_buffer(l, ptr,(unsigned long)(iref + 1), len);
@@ -2044,8 +2046,6 @@ static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info,
 		key.offset = (u64)-1;
 		dirid = key.objectid;
 	}
-	if (ptr < name)
-		goto out;
 	memmove(name, ptr, total_len);
 	name[total_len]='\0';
 	ret = 0;