vfs: have faccessat retry once on an ESTALE error

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

fs/open.c

@@ -316,6 +316,7 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 	struct path path;
 	struct inode *inode;
 	int res;
+	unsigned int lookup_flags = LOOKUP_FOLLOW;
 
 	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
 		return -EINVAL;
@@ -338,8 +339,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 	}
 
 	old_cred = override_creds(override_cred);
-
-	res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
+retry:
+	res = user_path_at(dfd, filename, lookup_flags, &path);
 	if (res)
 		goto out;
 
@@ -374,6 +375,10 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 
 out_path_release:
 	path_put(&path);
+	if (retry_estale(res, lookup_flags)) {
+		lookup_flags |= LOOKUP_REVAL;
+		goto retry;
+	}
 out:
 	revert_creds(old_cred);
 	put_cred(override_cred);