From patchwork Mon May 11 18:07:04 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 6381991 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id D7B7CBEEE1 for ; Mon, 11 May 2015 18:35:23 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 169F120A8E for ; Mon, 11 May 2015 18:35:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C8AE208F0 for ; Mon, 11 May 2015 18:35:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932915AbbEKScm (ORCPT ); Mon, 11 May 2015 14:32:42 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:47138 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754957AbbEKSIU (ORCPT ); Mon, 11 May 2015 14:08:20 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.76 #1 (Red Hat Linux)) id 1Yrs7l-0001Qh-SP; Mon, 11 May 2015 18:08:17 +0000 From: Al Viro To: Linus Torvalds Cc: Neil Brown , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v3 044/110] link_path_walk: kill the recursion Date: Mon, 11 May 2015 19:07:04 +0100 Message-Id: <1431367690-5223-44-git-send-email-viro@ZenIV.linux.org.uk> X-Mailer: git-send-email 1.7.7.6 In-Reply-To: <20150511180650.GA4147@ZenIV.linux.org.uk> References: <20150511180650.GA4147@ZenIV.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Al Viro absolutely straightforward now - the only variables we need to preserve across the recursive call are name, link and cookie, and recursion depth is limited (and can is equal to nd->depth). So arrange an array of triples to hold instances of those and be done with that. Signed-off-by: Al Viro --- fs/namei.c | 40 +++++++++++++++++++++++++++++----------- 1 file changed, 29 insertions(+), 11 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index b469ce2..9844bb2 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1711,8 +1711,14 @@ static inline u64 hash_name(const char *name) */ static int link_path_walk(const char *name, struct nameidata *nd) { + struct saved { + struct path link; + void *cookie; + const char *name; + } stack[MAX_NESTED_LINKS], *last = stack + nd->depth - 1; int err; - + +start: while (*name=='/') name++; if (!*name) @@ -1776,8 +1782,6 @@ Walked: goto Err; if (err) { - struct path link; - void *cookie; const char *s; if (unlikely(current->link_count >= MAX_NESTED_LINKS)) { @@ -1790,22 +1794,25 @@ Walked: nd->depth++; current->link_count++; + last++; - link = nd->link; - s = get_link(&link, nd, &cookie); + last->link = nd->link; + s = get_link(&last->link, nd, &last->cookie); if (unlikely(IS_ERR(s))) { err = PTR_ERR(s); current->link_count--; nd->depth--; + last--; goto Err; } err = 0; if (unlikely(!s)) { /* jumped */ - put_link(nd, &link, cookie); + put_link(nd, &last->link, last->cookie); current->link_count--; nd->depth--; + last--; } else { if (*s == '/') { if (!nd->root.mnt) @@ -1816,17 +1823,24 @@ Walked: nd->flags |= LOOKUP_JUMPED; } nd->inode = nd->path.dentry->d_inode; - err = link_path_walk(s, nd); + last->name = name; + name = s; + goto start; + +back: + name = last->name; if (unlikely(err)) { - put_link(nd, &link, cookie); + put_link(nd, &last->link, last->cookie); current->link_count--; nd->depth--; + last--; goto Err; } else { err = walk_component(nd, LOOKUP_FOLLOW); - put_link(nd, &link, cookie); + put_link(nd, &last->link, last->cookie); current->link_count--; nd->depth--; + last--; goto Walked; } } @@ -1838,9 +1852,13 @@ Walked: } terminate_walk(nd); Err: - return err; + if (likely(!nd->depth)) + return err; + goto back; OK: - return 0; + if (likely(!nd->depth)) + return 0; + goto back; } static int path_init(int dfd, const struct filename *name, unsigned int flags,