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[PATCH 4.4 33/49] mm: memcontrol: fix swap counter leak on swapout from offline cgroup

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.4 33/49] mm: memcontrol: fix swap counter leak on swapout from offline cgroup
Date 2016-08-14 22:30 +0200
Message-ID <s6acG-4ts-31@gated-at.bofh.it> (permalink)
References <s6acF-4ts-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vladimir Davydov <vdavydov@virtuozzo.com>

commit 1f47b61fb4077936465dcde872a4e5cc4fe708da upstream.

An offline memory cgroup might have anonymous memory or shmem left
charged to it and no swap.  Since only swap entries pin the id of an
offline cgroup, such a cgroup will have no id and so an attempt to
swapout its anon/shmem will not store memory cgroup info in the swap
cgroup map.  As a result, memcg->swap or memcg->memsw will never get
uncharged from it and any of its ascendants.

Fix this by always charging swapout to the first ancestor cgroup that
hasn't released its id yet.

[hannes@cmpxchg.org: add comment to mem_cgroup_swapout]
[vdavydov@virtuozzo.com: use WARN_ON_ONCE() in mem_cgroup_id_get_online()]
  Link: http://lkml.kernel.org/r/20160803123445.GJ13263@esperanza
Fixes: 73f576c04b941 ("mm: memcontrol: fix cgroup creation failure after many small jobs")
Link: http://lkml.kernel.org/r/5336daa5c9a32e776067773d9da655d2dc126491.1470219853.git.vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>	[3.19+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 mm/memcontrol.c |   37 +++++++++++++++++++++++++++++++++----
 1 file changed, 33 insertions(+), 4 deletions(-)

--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4141,6 +4141,24 @@ static void mem_cgroup_id_get(struct mem
 	atomic_inc(&memcg->id.ref);
 }
 
+static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
+{
+	while (!atomic_inc_not_zero(&memcg->id.ref)) {
+		/*
+		 * The root cgroup cannot be destroyed, so it's refcount must
+		 * always be >= 1.
+		 */
+		if (WARN_ON_ONCE(memcg == root_mem_cgroup)) {
+			VM_BUG_ON(1);
+			break;
+		}
+		memcg = parent_mem_cgroup(memcg);
+		if (!memcg)
+			memcg = root_mem_cgroup;
+	}
+	return memcg;
+}
+
 static void mem_cgroup_id_put(struct mem_cgroup *memcg)
 {
 	if (atomic_dec_and_test(&memcg->id.ref)) {
@@ -5723,7 +5741,7 @@ subsys_initcall(mem_cgroup_init);
  */
 void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 {
-	struct mem_cgroup *memcg;
+	struct mem_cgroup *memcg, *swap_memcg;
 	unsigned short oldid;
 
 	VM_BUG_ON_PAGE(PageLRU(page), page);
@@ -5738,16 +5756,27 @@ void mem_cgroup_swapout(struct page *pag
 	if (!memcg)
 		return;
 
-	mem_cgroup_id_get(memcg);
-	oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg));
+	/*
+	 * In case the memcg owning these pages has been offlined and doesn't
+	 * have an ID allocated to it anymore, charge the closest online
+	 * ancestor for the swap instead and transfer the memory+swap charge.
+	 */
+	swap_memcg = mem_cgroup_id_get_online(memcg);
+	oldid = swap_cgroup_record(entry, mem_cgroup_id(swap_memcg));
 	VM_BUG_ON_PAGE(oldid, page);
-	mem_cgroup_swap_statistics(memcg, true);
+	mem_cgroup_swap_statistics(swap_memcg, true);
 
 	page->mem_cgroup = NULL;
 
 	if (!mem_cgroup_is_root(memcg))
 		page_counter_uncharge(&memcg->memory, 1);
 
+	if (memcg != swap_memcg) {
+		if (!mem_cgroup_is_root(swap_memcg))
+			page_counter_charge(&swap_memcg->memsw, 1);
+		page_counter_uncharge(&memcg->memsw, 1);
+	}
+
 	/*
 	 * Interrupts should be disabled here because the caller holds the
 	 * mapping->tree_lock lock which is taken with interrupts-off. It is

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[PATCH 4.4 00/49] 4.4.18-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 33/49] mm: memcontrol: fix swap counter leak on swapout from offline cgroup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 05/49] net: bgmac: Fix infinite loop in bgmac_dma_tx_add() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 26/49] x86/mtrr: Fix Xorg crashes in Qemu sessions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 28/49] x86/xen, pat: Remove PAT table init code from Xen Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 01/49] tcp: make challenge acks less predictable Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 03/49] ipv4: reject RTNH_F_DEAD and RTNH_F_LINKDOWN from user space Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 12/49] PNP: Add Broadwell to Intel MCH size workaround Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 23/49] x86/mm/pat: Add support of non-default PAT MSR setting Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 24/49] x86/mm/pat: Add pat_disable() interface Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 10/49] scsi: ignore errors from scsi_dh_add_device() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 20/49] apparmor: fix ref count leak when profile sha1 hash is read Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 41/49] fs/dcache.c: avoid soft-lockup in dput() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 49/49] ext4: fix reference counting bug on block allocation error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 07/49] qed: Fix setting/clearing bit in completion bitmap Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 38/49] fuse: fsync() did not return IO errors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 46/49] ext4: dont call ext4_should_journal_data() on the journal inode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 43/49] crypto: scatterwalk - Fix test in scatterwalk_done Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 19/49] Revert "s390/kdump: Clear subchannel ID to signal non-CCW/SCSI IPL" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 45/49] ext4: fix deadlock during page writeback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 22/49] devpts: clean up interface to pty drivers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 48/49] ext4: short-cut orphan cleanup on error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 32/49] mm: memcontrol: fix cgroup creation failure after many small jobs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 06/49] net/irda: fix NULL pointer dereference on memory allocation failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 27/49] x86/mtrr: Fix PAT init handling when MTRR is disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 44/49] ext4: check for extents that wrap around Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 29/49] x86/pat: Document the PAT initialization sequence Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 36/49] block: fix use-after-free in seq file Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:30 +0200
  [PATCH 4.4 37/49] sysv, ipc: fix security-layer leaking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 09/49] ipath: Restrict use of the write() interface Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 35/49] x86/syscalls/64: Add compat_sys_keyctl for 32-bit userspace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 21/49] random: strengthen input validation for RNDADDTOENTCNT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 04/49] bonding: set carrier off for devices created through netlink Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.4 11/49] PNP: Add Haswell-ULT to Intel MCH size workaround Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  Re: [PATCH 4.4 00/49] 4.4.18-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-15 10:00 +0200
  Re: [PATCH 4.4 00/49] 4.4.18-stable review Guenter Roeck <linux@roeck-us.net> - 2016-08-15 15:10 +0200
  Re: [PATCH 4.4 00/49] 4.4.18-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-08-16 06:10 +0200

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