From: Vladimir Davydov <vdavy...@virtuozzo.com> 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. [han...@cmpxchg.org: add comment to mem_cgroup_swapout] [vdavy...@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.vdavy...@virtuozzo.com Signed-off-by: Vladimir Davydov <vdavy...@virtuozzo.com> Acked-by: Johannes Weiner <han...@cmpxchg.org> Acked-by: Michal Hocko <mho...@suse.com> Cc: <sta...@vger.kernel.org> [3.19+] Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> https://jira.vzint.dev/browse/PSBM-147036 (cherry picked from commit 1f47b61fb4077936465dcde872a4e5cc4fe708da) Signed-off-by: Pavel Tikhomirov <ptikhomi...@virtuozzo.com> --- mm/memcontrol.c | 39 ++++++++++++++++++++++++++++++++++----- 1 file changed, 34 insertions(+), 5 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 6356b6532163..a9a1fb354d33 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6679,6 +6679,24 @@ 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)) { @@ -7759,7 +7777,7 @@ static void __init enable_swap_cgroup(void) */ void mem_cgroup_swapout(struct page *page, swp_entry_t entry) { - struct mem_cgroup *memcg; + struct mem_cgroup *memcg, *swap_memcg; struct page_cgroup *pc; unsigned short oldid; @@ -7778,17 +7796,28 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry) VM_BUG_ON_PAGE(!(pc->flags & PCG_MEMSW), page); memcg = pc->mem_cgroup; - 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); - this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PSWPOUT]); + mem_cgroup_swap_statistics(swap_memcg, true); + this_cpu_inc(swap_memcg->stat->events[MEM_CGROUP_EVENTS_PSWPOUT]); pc->flags = 0; 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); + } + /* XXX: caller holds IRQ-safe mapping->tree_lock */ VM_BUG_ON(!irqs_disabled()); -- 2.40.1 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
