vfs: fix symlinkat to retry on ESTALE errors

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

fs/namei.c

@@ -3521,12 +3521,13 @@ SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
 	struct filename *from;
 	struct dentry *dentry;
 	struct path path;
+	unsigned int lookup_flags = 0;
 
 	from = getname(oldname);
 	if (IS_ERR(from))
 		return PTR_ERR(from);
-
-	dentry = user_path_create(newdfd, newname, &path, 0);
+retry:
+	dentry = user_path_create(newdfd, newname, &path, lookup_flags);
 	error = PTR_ERR(dentry);
 	if (IS_ERR(dentry))
 		goto out_putname;
@@ -3535,6 +3536,10 @@ SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
 	if (!error)
 		error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
 	done_path_create(&path, dentry);
+	if (retry_estale(error, lookup_flags)) {
+		lookup_flags |= LOOKUP_REVAL;
+		goto retry;
+	}
 out_putname:
 	putname(from);
 	return error;