From patchwork Mon Jul 4 23:15:12 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 12905872 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 2C7D1C43334 for ; Mon, 4 Jul 2022 23:15:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C057C6B0071; Mon, 4 Jul 2022 19:15:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BB4026B0073; Mon, 4 Jul 2022 19:15:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A7D656B0075; Mon, 4 Jul 2022 19:15:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 9C0886B0071 for ; Mon, 4 Jul 2022 19:15:55 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 7BBB18014D for ; Mon, 4 Jul 2022 23:15:55 +0000 (UTC) X-FDA: 79650977070.07.A83C1DE Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) by imf18.hostedemail.com (Postfix) with ESMTP id 26E531C004F for ; Mon, 4 Jul 2022 23:15:55 +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=phosGs0ReDXhvjah48sBo0KCwl+d1jcc+HCEqeu58tc=; b=OwdNXG7l7nBZtBBbjR/cEwIL4N J37eUfI1FdldQ2JpF8o2dJ2JHAuu3g5AX9ZcC1ukryfycNUEebrOsH9bjzn5Ms14CE5CNkbnEFGqs MYAVKAe6mUxmINf7gP+SuhmQ5NOKLLqGiIJPJwezFX+CUPngnBDRuMi5xYoptjm99AXdxw+ozX7dd RUdGasO87hSmy74nZJTIKnsrM8O5sp4QAVlELB8ReYdLKpNELFQf2zgYT8cv6WZMmQox9iK66Kq9n TgHphg+f7OxwqwIe3eA3NnlxLV5SbKhPv91SC5i4ZlWxYcAa8/WRiJWOWIk4fkjPr0mRjx2KC0bk9 25vU+zrg==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.95 #2 (Red Hat Linux)) id 1o8VHc-008AYW-Qq; Mon, 04 Jul 2022 23:15:12 +0000 Date: Tue, 5 Jul 2022 00:15:12 +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 4/7] step_into(): lose inode argument Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656976555; a=rsa-sha256; cv=none; b=m4Qkbgug/W70I1k4BOzak/nxmSfqthjqzdGs5WKuI1vGMGnewUmexRCbDXzwh+9/nSZbIy /4ajtpNqMCeyeBzaeJFvbUh8W4ag5ePEJ+mDWMQC0DGJfH2T/30S322D9HLeK0OYYKUpiY mAYQla9vN9Pc/ONqT1QNsnmIVmwxOSs= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=linux.org.uk header.s=zeniv-20220401 header.b=OwdNXG7l; dmarc=pass (policy=none) header.from=zeniv.linux.org.uk; spf=none (imf18.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=1656976555; 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=phosGs0ReDXhvjah48sBo0KCwl+d1jcc+HCEqeu58tc=; b=z4S2NO2N5QUMglNIvdkrqShCakyqcJ+3UkIogkJGTzO31DcEIuJqp+KxpsyNCFExogW5tJ hU+Pb0uI+Ki8H035ab/FeSGAxE0Pd5Emw3URoijLUQAteHWf/6OL8ebD5aM9PnVqIKf7F/ Kjc0RhUkUTeqWCyZ39Nz7woGXRGOaE8= Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=linux.org.uk header.s=zeniv-20220401 header.b=OwdNXG7l; dmarc=pass (policy=none) header.from=zeniv.linux.org.uk; spf=none (imf18.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-Rspam-User: X-Stat-Signature: owmyfmu7ohrdtkcciat8pu4qffr8op7n X-Rspamd-Queue-Id: 26E531C004F X-Rspamd-Server: rspam04 X-HE-Tag: 1656976555-603249 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: make handle_mounts() always fetch it. This is just the first step - the callers of step_into() will stop trying to calculate the sucker, etc. The passed value should be equal to dentry->d_inode in all cases; in RCU mode - fetched after we'd sampled ->d_seq. Might as well fetch it here. We do need to validate ->d_seq, which duplicates the check currently done in lookup_fast(); that duplication will go away shortly. After that change handle_mounts() always ignores the initial value of *inode and always sets it on success. Signed-off-by: Al Viro --- fs/namei.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index c7c9e88add85..dddbebf92b48 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1532,6 +1532,11 @@ 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))) return 0; // *path and nd->next_seq might've been clobbered @@ -1842,9 +1847,10 @@ static const char *pick_link(struct nameidata *nd, struct path *link, * NOTE: dentry must be what nd->next_seq had been sampled from. */ static const char *step_into(struct nameidata *nd, int flags, - struct dentry *dentry, struct inode *inode) + struct dentry *dentry) { struct path path; + struct inode *inode; int err = handle_mounts(nd, dentry, &path, &inode); if (err < 0) @@ -1970,7 +1976,7 @@ static const char *handle_dots(struct nameidata *nd, int type) parent = follow_dotdot(nd, &inode); if (IS_ERR(parent)) return ERR_CAST(parent); - error = step_into(nd, WALK_NOFOLLOW, parent, inode); + error = step_into(nd, WALK_NOFOLLOW, parent); if (unlikely(error)) return error; @@ -2015,7 +2021,7 @@ static const char *walk_component(struct nameidata *nd, int flags) } if (!(flags & WALK_MORE) && nd->depth) put_link(nd); - return step_into(nd, flags, dentry, inode); + return step_into(nd, flags, dentry); } /* @@ -2474,8 +2480,7 @@ static int handle_lookup_down(struct nameidata *nd) if (!(nd->flags & LOOKUP_RCU)) dget(nd->path.dentry); nd->next_seq = nd->seq; - return PTR_ERR(step_into(nd, WALK_NOFOLLOW, - nd->path.dentry, nd->inode)); + return PTR_ERR(step_into(nd, WALK_NOFOLLOW, nd->path.dentry)); } /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ @@ -3464,7 +3469,7 @@ static const char *open_last_lookups(struct nameidata *nd, finish_lookup: if (nd->depth) put_link(nd); - res = step_into(nd, WALK_TRAILING, dentry, inode); + res = step_into(nd, WALK_TRAILING, dentry); if (unlikely(res)) nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); return res;