vfs: allow setxattr to retry once on ESTALE errors

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/xattr.c

@@ -370,8 +370,9 @@ SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 {
 	struct path path;
 	int error;
-
-	error = user_path(pathname, &path);
+	unsigned int lookup_flags = LOOKUP_FOLLOW;
+retry:
+	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 	if (error)
 		return error;
 	error = mnt_want_write(path.mnt);
@@ -380,6 +381,10 @@ SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 		mnt_drop_write(path.mnt);
 	}
 	path_put(&path);
+	if (retry_estale(error, lookup_flags)) {
+		lookup_flags |= LOOKUP_REVAL;
+		goto retry;
+	}
 	return error;
 }