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authorVladimir Davydov <vdavydov@virtuozzo.com>2016-08-11 15:33:00 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-08-16 09:30:51 +0200
commita0fddee3fb342a4150c83c36e317660663691a72 (patch)
tree2435e80263be529b9150d62649fe3c7ffdbb6e0c /mm
parent8627c7750a66a46d56d3564e1e881aa53764497c (diff)
mm: memcontrol: fix swap counter leak on swapout from offline cgroup
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>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c37
1 files changed, 33 insertions, 4 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e139c982b143..27eaee2acaae 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4141,6 +4141,24 @@ static void mem_cgroup_id_get(struct mem_cgroup *memcg)
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)) {
@@ -5721,7 +5739,7 @@ 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);
@@ -5736,16 +5754,27 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
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