From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
Hugh Dickins <hughd@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Sasha Levin <sashal@kernel.org>,
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 [thread overview]
Message-ID: <20190313191806.160547-10-sashal@kernel.org> (raw)
In-Reply-To: <20190313191806.160547-1-sashal@kernel.org>
From: "Darrick J. Wong" <darrick.wong@oracle.com>
[ 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 <darrick.wong@oracle.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Reported-by: Matej Kupljen <matej.kupljen@gmail.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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
next prev parent reply other threads:[~2019-03-13 19:18 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-13 19:17 [PATCH AUTOSEL 4.4 01/15] ARM: 8824/1: fix a migrating irq bug when hotplug cpu Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 02/15] assoc_array: Fix shortcut creation Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 03/15] scsi: libiscsi: Fix race between iscsi_xmit_task and iscsi_complete_task Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 04/15] scsi: libsas: Fix rphy phy_identifier for PHYs with end devices attached Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 05/15] net: systemport: Fix reception of BPDUs Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 06/15] pinctrl: meson: meson8b: fix the sdxc_a data 1..3 pins Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 07/15] net: mv643xx_eth: disable clk on error path in mv643xx_eth_shared_probe() Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 08/15] ASoC: topology: free created components in tplg load error Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 09/15] arm64: Relax GIC version check during early boot Sasha Levin
2019-03-13 19:17 ` Sasha Levin [this message]
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 11/15] ARC: uacces: remove lp_start, lp_end from clobber list Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 12/15] phonet: fix building with clang Sasha Levin
2019-03-13 19:17 ` [PATCH AUTOSEL 4.4 13/15] mac80211_hwsim: propagate genlmsg_reply return code Sasha Levin
2019-03-13 19:18 ` [PATCH AUTOSEL 4.4 14/15] mdio_bus: Fix use-after-free on device_register fails Sasha Levin
2019-03-13 19:18 ` [PATCH AUTOSEL 4.4 15/15] net: set static variable an initial value in atl2_probe() Sasha Levin
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