From patchwork Mon May 11 18:08:09 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 6380381 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id A648B9F32E for ; Mon, 11 May 2015 18:09:21 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id DDE342098B for ; Mon, 11 May 2015 18:09:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE67B209A2 for ; Mon, 11 May 2015 18:09:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932120AbbEKSJS (ORCPT ); Mon, 11 May 2015 14:09:18 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:47643 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755074AbbEKSIc (ORCPT ); Mon, 11 May 2015 14:08:32 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.76 #1 (Red Hat Linux)) id 1Yrs7x-0001XG-Vt; Mon, 11 May 2015 18:08:30 +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 109/110] namei: handle absolute symlinks without dropping out of RCU mode Date: Mon, 11 May 2015 19:08:09 +0100 Message-Id: <1431367690-5223-109-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 Signed-off-by: Al Viro --- fs/namei.c | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 1771143..fc8df8b 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -499,7 +499,7 @@ struct nameidata { struct path root; struct inode *inode; /* path.dentry.d_inode */ unsigned int flags; - unsigned seq, m_seq; + unsigned seq, m_seq, root_seq; int last_type; unsigned depth; int total_link_count; @@ -780,14 +780,14 @@ static __always_inline void set_root(struct nameidata *nd) static __always_inline unsigned set_root_rcu(struct nameidata *nd) { struct fs_struct *fs = current->fs; - unsigned seq, res; + unsigned seq; do { seq = read_seqcount_begin(&fs->seq); nd->root = fs->root; - res = __read_seqcount_begin(&nd->root.dentry->d_seq); + nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq); } while (read_seqcount_retry(&fs->seq, seq)); - return res; + return nd->root_seq; } static void path_put_conditional(struct path *path, struct nameidata *nd) @@ -988,15 +988,23 @@ const char *get_link(struct nameidata *nd) } if (*res == '/') { if (nd->flags & LOOKUP_RCU) { - if (unlikely(unlazy_walk(nd, NULL, 0))) + struct dentry *d; + if (!nd->root.mnt) + set_root_rcu(nd); + nd->path = nd->root; + d = nd->path.dentry; + nd->inode = d->d_inode; + nd->seq = nd->root_seq; + if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq))) return ERR_PTR(-ECHILD); + } else { + if (!nd->root.mnt) + set_root(nd); + path_put(&nd->path); + nd->path = nd->root; + path_get(&nd->root); + nd->inode = nd->path.dentry->d_inode; } - if (!nd->root.mnt) - set_root(nd); - path_put(&nd->path); - nd->path = nd->root; - path_get(&nd->root); - nd->inode = nd->path.dentry->d_inode; nd->flags |= LOOKUP_JUMPED; while (unlikely(*++res == '/')) ;