From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0784CC43219 for ; Sat, 27 Apr 2019 15:29:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D4B89212F5 for ; Sat, 27 Apr 2019 15:29:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728654AbfD0P3t (ORCPT ); Sat, 27 Apr 2019 11:29:49 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:32898 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727272AbfD0PPS (ORCPT ); Sat, 27 Apr 2019 11:15:18 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hKP2p-0000zB-Uq; Sat, 27 Apr 2019 16:15:16 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hKP2n-0004cd-0i; Sat, 27 Apr 2019 16:15:13 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Linus Torvalds" , "Matej Kupljen" , "Hugh Dickins" , "Al Viro" , "Darrick J. Wong" Date: Sat, 27 Apr 2019 16:13:09 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 167/202] tmpfs: fix link accounting when a tmpfile is linked in In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.66-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: "Darrick J. Wong" commit 1062af920c07f5b54cf5060fde3339da6df0cf6b upstream. tmpfs has a peculiarity of accounting hard links as if they were separate inodes: so that when the number of inodes is limited, as it is by default, a user cannot soak up an unlimited amount of unreclaimable dcache memory just by repeatedly linking a file. But when v3.11 added O_TMPFILE, and the ability to use linkat() on the fd, we missed accommodating this new case in tmpfs: "df -i" shows that an extra "inode" remains accounted after the file is unlinked and the fd closed and the actual inode evicted. If a user repeatedly links tmpfiles into a tmpfs, the limit will be hit (ENOSPC) even after they are deleted. Just skip the extra reservation from shmem_link() in this case: there's a sense in which this first link of a tmpfile is then cheaper than a hard link of another file, but the accounting works out, and there's still good limiting, so no need to do anything more complicated. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1902182134370.7035@eggly.anvils Fixes: f4e0c30c191 ("allow the temp files created by open() to be linked to") Signed-off-by: Darrick J. Wong Signed-off-by: Hugh Dickins Reported-by: Matej Kupljen Acked-by: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- mm/shmem.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2013,10 +2013,14 @@ static int shmem_link(struct dentry *old * No ordinary (disk based) filesystem counts links as inodes; * but each new link needs a new dentry, pinning lowmem, and * tmpfs dentries cannot be pruned until they are unlinked. + * But if an O_TMPFILE file is linked into the tmpfs, the + * first link must skip that, to get the accounting right. */ - ret = shmem_reserve_inode(inode->i_sb); - if (ret) - goto out; + if (inode->i_nlink) { + ret = shmem_reserve_inode(inode->i_sb); + if (ret) + goto out; + } dir->i_size += BOGO_DIRENT_SIZE; inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;