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[209.85.220.65]) by mx.google.com with SMTPS id b13sor3838896pfi.19.2019.03.13.12.58.59 for (Google Transport Security); Wed, 13 Mar 2019 12:59:00 -0700 (PDT) Received-SPF: pass (google.com: domain of hughd@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b="SBr3m5X/"; spf=pass (google.com: domain of hughd@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=hughd@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=SajRrUaUGaud6Nn4Qj6K9i18P4JO+MNtdJ37Bn8y7bQ=; b=SBr3m5X/eJzdT+sEonH+SmkvXYruM+CrkEu9nppT3EY0319WJl+seG3l5xz3A4DZYE A+oRZ9HXJeu60cYin5WicOu2UtNbEI4SBvN25Tni1LO2EXl+FCnyKxPkxb7K6d9IRthM 6sVG/zHpR+leoapOgFGFCQayKJJr81IyKkQ3KgWD9FHZEi+H7GyYf9aGJILNWm3j5MJv 7X8Ap3skyXpWAGZJbnrxBuZltTxhekSKYPjUddN1oy4zJFFHkKnvFlvpnuorr/qczwVy su7wZJV7u72Q1W1t881hlTX/VvhqJdGEGK+UJpXt/fG3xqpYm9CN7TbG1JfQPB8qIvCu Uy9A== X-Google-Smtp-Source: APXvYqxtqw/l3jAmyf1Nv+r2FH56v+9+XlPl1VhkWGkRCkFf6Jsi+2m51OrFhzBX29knybK33dc4mA== X-Received: by 2002:a63:2bcd:: with SMTP id r196mr40920203pgr.355.1552507138925; Wed, 13 Mar 2019 12:58:58 -0700 (PDT) Received: from [100.112.89.103] ([104.133.8.103]) by smtp.gmail.com with ESMTPSA id e63sm17933208pfa.116.2019.03.13.12.58.57 (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 13 Mar 2019 12:58:58 -0700 (PDT) Date: Wed, 13 Mar 2019 12:58:26 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Sasha Levin cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, "Darrick J. Wong" , Hugh Dickins , Andrew Morton , Linus Torvalds , linux-mm@kvack.org Subject: Re: [PATCH AUTOSEL 4.20 37/60] tmpfs: fix link accounting when a tmpfile is linked in In-Reply-To: <20190313191021.158171-37-sashal@kernel.org> Message-ID: References: <20190313191021.158171-1-sashal@kernel.org> <20190313191021.158171-37-sashal@kernel.org> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII 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: AUTOSEL is wrong to select this commit without also selecting 29b00e609960 ("tmpfs: fix uninitialized return value in shmem_link") which contains the tag Fixes: 1062af920c07 ("tmpfs: fix link accounting when a tmpfile is linked in") Please add 29b00e609960 for those 6 trees, or else omit 1062af920c07 for now. Thanks, Hugh On Wed, 13 Mar 2019, Sasha Levin wrote: > 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 5d07e0b1352f..7872e3b75e57 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2852,10 +2852,14 @@ 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(inode); > -- > 2.19.1