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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 804FEC43381 for ; Wed, 13 Mar 2019 19:18:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 50EFF2075C for ; Wed, 13 Mar 2019 19:18:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1552504726; bh=Gy41IntoW9zDc+4SvaYFkEzrMixdHyrMNGOPn18QZJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Fp8xMygZdpS87IGeayJlHpKJdP0TU4Coclbhx/wu6/WH3kR35eRDk+dWIbk8wozAY 1MF2uMwDP/2bvUW20M6Ygohr3s5QKnPJbFnhp93/sJ021xyHYaBA3bOl7/1gu3znpa +9ALokAn6LVxV1j5w9+/qhyfggt3rGI/CCVYnCWc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728763AbfCMTSo (ORCPT ); Wed, 13 Mar 2019 15:18:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:49110 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728672AbfCMTSd (ORCPT ); Wed, 13 Mar 2019 15:18:33 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A7291217F5; Wed, 13 Mar 2019 19:18:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1552504712; bh=Gy41IntoW9zDc+4SvaYFkEzrMixdHyrMNGOPn18QZJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IGPkThvKUh08LEjBy45Sc0FASiCmmyh2VyO1mkBJGVTyf6DNgu1RAHHd0FHxzsQzb 8kUypHdCrBzt4QkO4Y243YviEYvvG70HXbqwox4PE0k4b//p7MjFhPCAcSDjUt8jBN 4xPrH7ULVRH4turElBSowqZlTm3Eg5UpivVrs1qc= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Darrick J. Wong" , Hugh Dickins , Andrew Morton , Linus Torvalds , Sasha Levin , linux-mm@kvack.org Subject: [PATCH AUTOSEL 4.4 10/15] tmpfs: fix link accounting when a tmpfile is linked in Date: Wed, 13 Mar 2019 15:17:56 -0400 Message-Id: <20190313191806.160547-10-sashal@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20190313191806.160547-1-sashal@kernel.org> References: <20190313191806.160547-1-sashal@kernel.org> MIME-Version: 1.0 X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Darrick J. Wong" [ Upstream commit 1062af920c07f5b54cf5060fde3339da6df0cf6b ] 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: Sasha Levin --- mm/shmem.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index d902b413941a..183ed4dae219 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2299,10 +2299,14 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentr * 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; -- 2.19.1