From patchwork Mon Jul 4 23:17:03 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 12905875 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id CF0C1C43334 for ; Mon, 4 Jul 2022 23:17:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6FBD96B0074; Mon, 4 Jul 2022 19:17:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6ABCD6B0075; Mon, 4 Jul 2022 19:17:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 59B366B0078; Mon, 4 Jul 2022 19:17:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 4C0046B0074 for ; Mon, 4 Jul 2022 19:17:40 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 1932F34FD6 for ; Mon, 4 Jul 2022 23:17:40 +0000 (UTC) X-FDA: 79650981480.13.0941E0E Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) by imf03.hostedemail.com (Postfix) with ESMTP id B720620003 for ; Mon, 4 Jul 2022 23:17:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=NqVApc9I2DDH/ifQWSRH221HRDI5UWBJClZrnVtHcvg=; b=XMq6en3D1K42NPJrNPt3lNiGHU 6m4VZEYHJsKw2KJ8FEER0qK8oNGCVOWcuDgjwh8WQDSnCv3uQR6L+1i3enPxKWoWnbVOH3z6CEie3 nAp9cJJDd2p+yBlssUPpEpXlwKJbc2p27ShaRo5hao7QkcNFe3prUfJ6W5u0gQWZQnbKrS5pR1Tdf egeY54C3ZyVr7W9Zdixd+0O1ckAB19QGVGrBNLoZWZcqmBVvuhjabPDBCUO+bxM+6STEGYDHx9FyS toKCReTROXqjfeOSHKWpf/dSfOftFLkoYOpfUHq4w3tP7uXrpyQGmCSK5nAd/yJzARh/75JRzMNP4 bDBFQeCA==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.95 #2 (Red Hat Linux)) id 1o8VJP-008AcR-HB; Mon, 04 Jul 2022 23:17:03 +0000 Date: Tue, 5 Jul 2022 00:17:03 +0100 From: Al Viro To: Linus Torvalds Cc: Alexander Potapenko , Alexei Starovoitov , Andrew Morton , Andrey Konovalov , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Dumazet , Greg Kroah-Hartman , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jens Axboe , Joonsoo Kim , Kees Cook , Marco Elver , Mark Rutland , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , kasan-dev , Linux-MM , linux-arch , Linux Kernel Mailing List , Evgenii Stepanov , Nathan Chancellor , Nick Desaulniers , Segher Boessenkool , Vitaly Buka , linux-toolchains Subject: [PATCH 7/7] step_into(): move fetching ->d_inode past handle_mounts() Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=linux.org.uk header.s=zeniv-20220401 header.b=XMq6en3D; dmarc=pass (policy=none) header.from=zeniv.linux.org.uk; spf=none (imf03.hostedemail.com: domain of viro@ftp.linux.org.uk has no SPF policy when checking 62.89.141.173) smtp.mailfrom=viro@ftp.linux.org.uk ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656976659; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=NqVApc9I2DDH/ifQWSRH221HRDI5UWBJClZrnVtHcvg=; b=E4xo7TLcmOZ13U0bs98MFffi8IexFN8V7/b70O8L3g2yem+IqosehqoP7wAySOaTE575bn bm6cntSPeRuQ/cbbwMcK6wppAoQjZ075Y101oKgcG0ZVj2yr6ZQ0QabR5m+rIeSVPpJnJs ov82jsjwONwzQvAlCJqbCKmt3JqrL/o= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656976659; a=rsa-sha256; cv=none; b=PE7mgfShWL1MsMhvxdAOSPQkNsiJTk31+udVPq73O4acYiVtxA+As335X19W4la9ACjRNy 7+OVSi3nS0+cfOkXMbne8T4Lwke34SNbS+ILT5QK1voAtSp/4qANZn0d1yh7rogX9gGk3h HnU28N3zqhqUvO7M4DTSBmNOY7VZSw8= X-Stat-Signature: 65acpwez3n1r59qg1doyfk55coy5cqas X-Rspamd-Queue-Id: B720620003 Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=linux.org.uk header.s=zeniv-20220401 header.b=XMq6en3D; dmarc=pass (policy=none) header.from=zeniv.linux.org.uk; spf=none (imf03.hostedemail.com: domain of viro@ftp.linux.org.uk has no SPF policy when checking 62.89.141.173) smtp.mailfrom=viro@ftp.linux.org.uk X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1656976659-326747 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: ... and lose messing with it in __follow_mount_rcu() Signed-off-by: Al Viro --- fs/namei.c | 31 +++++++++++-------------------- 1 file changed, 11 insertions(+), 20 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index cdb61d09df79..f2c99e75b578 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1470,8 +1470,7 @@ EXPORT_SYMBOL(follow_down); * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if * we meet a managed dentry that would need blocking. */ -static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, - struct inode **inode) +static bool __follow_mount_rcu(struct nameidata *nd, struct path *path) { struct dentry *dentry = path->dentry; unsigned int flags = dentry->d_flags; @@ -1501,13 +1500,6 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, dentry = path->dentry = mounted->mnt.mnt_root; nd->state |= ND_JUMPED; nd->next_seq = read_seqcount_begin(&dentry->d_seq); - *inode = dentry->d_inode; - /* - * We don't need to re-check ->d_seq after this - * ->d_inode read - there will be an RCU delay - * between mount hash removal and ->mnt_root - * becoming unpinned. - */ flags = dentry->d_flags; // makes sure that non-RCU pathwalk could reach // this state. @@ -1523,7 +1515,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, } static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, - struct path *path, struct inode **inode) + struct path *path) { bool jumped; int ret; @@ -1532,12 +1524,7 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, path->dentry = dentry; if (nd->flags & LOOKUP_RCU) { unsigned int seq = nd->next_seq; - *inode = dentry->d_inode; - if (read_seqcount_retry(&dentry->d_seq, seq)) - return -ECHILD; - if (unlikely(!*inode)) - return -ENOENT; - if (likely(__follow_mount_rcu(nd, path, inode))) + if (likely(__follow_mount_rcu(nd, path))) return 0; // *path and nd->next_seq might've been clobbered path->mnt = nd->path.mnt; @@ -1557,8 +1544,6 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, dput(path->dentry); if (path->mnt != nd->path.mnt) mntput(path->mnt); - } else { - *inode = d_backing_inode(path->dentry); } return ret; } @@ -1839,15 +1824,21 @@ static const char *step_into(struct nameidata *nd, int flags, { struct path path; struct inode *inode; - int err = handle_mounts(nd, dentry, &path, &inode); + int err = handle_mounts(nd, dentry, &path); if (err < 0) return ERR_PTR(err); + inode = path.dentry->d_inode; if (likely(!d_is_symlink(path.dentry)) || ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) || (flags & WALK_NOFOLLOW)) { /* not a symlink or should not follow */ - if (!(nd->flags & LOOKUP_RCU)) { + if (nd->flags & LOOKUP_RCU) { + if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq)) + return ERR_PTR(-ECHILD); + if (unlikely(!inode)) + return ERR_PTR(-ENOENT); + } else { dput(nd->path.dentry); if (nd->path.mnt != path.mnt) mntput(nd->path.mnt);