Btrfs: do not ignore errors from btrfs_lookup_xattr in do_setxattr

The return value from btrfs_lookup_xattr() can be a pointer encoding an
error, therefore deal with it. This fixes commit 5f5bc6b1
("Btrfs: make xattr replace operations atomic").
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/xattr.c

@@ -111,6 +111,8 @@ static int do_setxattr(struct btrfs_trans_handle *trans,
 					name, name_len, -1);
 		if (!di && (flags & XATTR_REPLACE))
 			ret = -ENODATA;
+		else if (IS_ERR(di))
+			ret = PTR_ERR(di);
 		else if (di)
 			ret = btrfs_delete_one_dir_name(trans, root, path, di);
 		goto out;
@@ -127,10 +129,12 @@ static int do_setxattr(struct btrfs_trans_handle *trans,
 		ASSERT(mutex_is_locked(&inode->i_mutex));
 		di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
 					name, name_len, 0);
-		if (!di) {
+		if (!di)
 			ret = -ENODATA;
+		else if (IS_ERR(di))
+			ret = PTR_ERR(di);
+		if (ret)
 			goto out;
-		}
 		btrfs_release_path(path);
 		di = NULL;
 	}