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[PATCH 4.6 34/56] mm: memcontrol: fix swap counter leak on swapout from offline cgroup

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.6 34/56] mm: memcontrol: fix swap counter leak on swapout from offline cgroup
Date 2016-08-14 22:50 +0200
Message-ID <s6aw1-4AX-33@gated-at.bofh.it> (permalink)
References <s6amm-4wI-9@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.6-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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/memcontrol.c |   44 ++++++++++++++++++++++++++++++++++++++------
 1 file changed, 38 insertions(+), 6 deletions(-)

--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4069,6 +4069,24 @@ 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)) {
@@ -5785,7 +5803,7 @@ 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);
@@ -5800,16 +5818,27 @@ 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
@@ -5848,11 +5877,14 @@ int mem_cgroup_try_charge_swap(struct pa
 	if (!memcg)
 		return 0;
 
+	memcg = mem_cgroup_id_get_online(memcg);
+
 	if (!mem_cgroup_is_root(memcg) &&
-	    !page_counter_try_charge(&memcg->swap, 1, &counter))
+	    !page_counter_try_charge(&memcg->swap, 1, &counter)) {
+		mem_cgroup_id_put(memcg);
 		return -ENOMEM;
+	}
 
-	mem_cgroup_id_get(memcg);
 	oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg));
 	VM_BUG_ON_PAGE(oldid, page);
 	mem_cgroup_swap_statistics(memcg, true);

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[PATCH 4.6 00/56] 4.6.7-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:40 +0200
  [PATCH 4.6 56/56] ext4: fix reference counting bug on block allocation error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 02/56] libnvdimm, pfn, dax: fix initialization vs autodetect for mode + alignment Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 28/56] x86/xen, pat: Remove PAT table init code from Xen Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 35/56] mm: memcontrol: fix memcg id ref counter on swap charge move Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 06/56] bonding: set carrier off for devices created through netlink Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 34/56] mm: memcontrol: fix swap counter leak on swapout from offline cgroup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 32/56] powerpc/eeh: Fix invalid cached PE primary bus Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 39/56] radix-tree: account nodes to memcg only if explicitly requested Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 45/56] Revert "mm, mempool: only set __GFP_NOMEMALLOC if there are free elements" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 41/56] x86/power/64: Fix hibernation return address corruption Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 22/56] random: strengthen input validation for RNDADDTOENTCNT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 54/56] ext4: validate s_reserved_gdt_blocks on mount Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 37/56] block: fix use-after-free in seq file Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 51/56] ext4: check for extents that wrap around Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 27/56] x86/mtrr: Fix PAT init handling when MTRR is disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 05/56] tcp: enable per-socket rate limiting of all challenge acks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 25/56] x86/mm/pat: Replace cpu_has_pat with boot_cpu_has() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 21/56] regulator: qcom_smd: Remove list_voltage callback for rpm_smps_ldo_ops_fixed Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 47/56] Revert "cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 50/56] serial: mvebu-uart: free the IRQ in ->shutdown() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 53/56] ext4: dont call ext4_should_journal_data() on the journal inode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 46/56] fs/dcache.c: avoid soft-lockup in dput() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 48/56] crypto: gcm - Filter out async ghash if necessary Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 09/56] bridge: Fix incorrect re-injection of LLDP packets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 30/56] x86/mm/pat: Fix BUG_ON() in mmap_mem() on QEMU/i386 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 38/56] sysv, ipc: fix security-layer leaking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 44/56] fuse: fix wrong assignment of ->flags in fuse_send_init() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 18/56] IB/hfi1: Correct issues with sc5 computation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 16/56] arm: oabi compat: add missing access checks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 17/56] KEYS: 64-bit MIPS needs to use compat_sys_keyctl for 32-bit userspace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 22:50 +0200
  [PATCH 4.6 42/56] fuse: fsync() did not return IO errors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 36/56] x86/syscalls/64: Add compat_sys_keyctl for 32-bit userspace Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 29/56] x86/pat: Document the PAT initialization sequence Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 40/56] x86/microcode: Fix suspend to RAM with builtin microcode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 33/56] powerpc/bpf/jit: Disable classic BPF JIT on ppc64le Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 26/56] x86/mtrr: Fix Xorg crashes in Qemu sessions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 23/56] x86/mm/pat: Add support of non-default PAT MSR setting Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 52/56] ext4: fix deadlock during page writeback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 55/56] ext4: short-cut orphan cleanup on error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 31/56] udf: Prevent stack overflow on corrupted filesystem mount Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 43/56] fuse: fuse_flush must check mapping->flags for errors Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 49/56] crypto: scatterwalk - Fix test in scatterwalk_done Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:00 +0200
  [PATCH 4.6 20/56] apparmor: fix ref count leak when profile sha1 hash is read Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:10 +0200
  [PATCH 4.6 04/56] tcp: make challenge acks less predictable Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:10 +0200
  [PATCH 4.6 03/56] ppp: defer netns reference release for ppp channel Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:10 +0200
  [PATCH 4.6 19/56] IB/hfi1: Fix deadlock with txreq allocation slow path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:10 +0200
  [PATCH 4.6 08/56] vlan: use a valid default mtu value for vlan over macsec Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:10 +0200
  [PATCH 4.6 07/56] net: bgmac: Fix infinite loop in bgmac_dma_tx_add() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:10 +0200
  [PATCH 4.6 24/56] x86/mm/pat: Add pat_disable() interface Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-14 23:10 +0200
  Re: [PATCH 4.6 00/56] 4.6.7-stable review Guenter Roeck <linux@roeck-us.net> - 2016-08-15 15:10 +0200
  Re: [PATCH 4.6 00/56] 4.6.7-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-08-16 06:10 +0200

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