vfs: have chroot retry once on ESTALE error

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

fs/open.c

diff --git a/fs/open.c b/fs/open.c
index 402dfcb..a13a54d 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -445,8 +445,9 @@
 {
 	struct path path;
 	int error;
-
-	error = user_path_dir(filename, &path);
+	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
+retry:
+	error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 	if (error)
 		goto out;
 
@@ -465,6 +466,10 @@
 	error = 0;
 dput_and_out:
 	path_put(&path);
+	if (retry_estale(error, lookup_flags)) {
+		lookup_flags |= LOOKUP_REVAL;
+		goto retry;
+	}
 out:
 	return error;
 }