When commit [1] was ported we should not have removed css_get in mem_cgroup_swapout, as when we put page from memory to swap we need to have refcount on css in case we will want to put it back. In vz7 we don't have commit [2] which in mainstream preceeds [1], that's why in mainstream in [1] they removed css_get as we don't need to take second reference for the same page. So fix for [1] is bringing back css_get.
When commit [3] was ported we should have removed this css_get as now we take mem_cgroup_id_get instead. But we should not have added css_put there as it would be an excess put (remove get + put is equivalent of double put). In mainstream [3] is preceeded by [2], so they need to put css reference of page put to swap and replace it with id reference. So fix for [1] + [2] is removal of css_put. When commit [4] was ported in __mem_cgroup_clear_mc we should have removed css_put-s as now after [3] we don't have css reference for swapped pages, and there is nothing to put when moving to other cgroup. And now I understand why they do css_put(from)->css_put(to) replacement in original mainstream patch, it's because they also don't have refcount from page which is already in swap after [3], but obviousely when they charge pages to destination cgroup they have reference from them to css and as they are swap they need to put this reference. https://jira.vzint.dev/browse/PSBM-148702 Fixes: d0f735e5df66 ("ms/mm: memcontrol: uncharge pages on swapout") [1] e8ea14cc6ead ("mm: memcontrol: take a css reference for each charged page") [2] Fixes: 9dcef96ce3e2 ("ms/mm: memcontrol: fix cgroup creation failure after many small jobs") [3] Fixes: 11870ae0f7b6 ("ms/mm: memcontrol: fix memcg id ref counter on swap charge move") [4] Signed-off-by: Pavel Tikhomirov <ptikhomi...@virtuozzo.com> --- mm/memcontrol.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index b2911329852f..8f74de3ebace 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -7436,9 +7436,6 @@ static void __mem_cgroup_clear_mc(void) mem_cgroup_id_put_many(mc.from, mc.moved_swap); - for (i = 0; i < mc.moved_swap; i++) - css_put(&mc.from->css); - if (!mem_cgroup_is_root(mc.to)) { /* * we charged both to->memory and to->memsw, so we @@ -7837,9 +7834,6 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry) mem_cgroup_charge_statistics(memcg, page, -1); memcg_check_events(memcg, page); - - if (!mem_cgroup_is_root(memcg)) - css_put(&memcg->css); } /** -- 2.41.0 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
