From: Hugh Dickins Date: Fri, 13 Jan 2012 01:19:52 +0000 (-0800) Subject: memcg: fix split_huge_page_refcounts() X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=12d27107867fc7216e8faaff0b894b0f162dcf75;p=mv-sheeva.git memcg: fix split_huge_page_refcounts() This patch started off as a cleanup: __split_huge_page_refcounts() has to cope with two scenarios, when the hugepage being split is already on LRU, and when it is not; but why does it have to split that accounting across three different sites? Consolidate it in lru_add_page_tail(), handling evictable and unevictable alike, and use standard add_page_to_lru_list() when accounting is needed (when the head is not yet on LRU). But a recent regression in -next, I guess the removal of PageCgroupAcctLRU test from mem_cgroup_split_huge_fixup(), makes this now a necessary fix: under load, the MEM_CGROUP_ZSTAT count was wrapping to a huge number, messing up reclaim calculations and causing a freeze at rmdir of cgroup. Add a VM_BUG_ON to mem_cgroup_lru_del_list() when we're about to wrap that count - this has not been the only such incident. Document that lru_add_page_tail() is for Transparent HugePages by #ifdef around it. Signed-off-by: Hugh Dickins Cc: Daisuke Nishimura Cc: KAMEZAWA Hiroyuki Cc: Johannes Weiner Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 76cc3f7dd4f..b3ffc21ce80 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1229,7 +1229,6 @@ static void __split_huge_page_refcount(struct page *page) { int i; struct zone *zone = page_zone(page); - int zonestat; int tail_count = 0; /* prevent PageLRU to go away from under us, and freeze lru stats */ @@ -1317,15 +1316,6 @@ static void __split_huge_page_refcount(struct page *page) __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); - /* - * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics, - * so adjust those appropriately if this page is on the LRU. - */ - if (PageLRU(page)) { - zonestat = NR_LRU_BASE + page_lru(page); - __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1)); - } - ClearPageCompound(page); compound_unlock(page); spin_unlock_irq(&zone->lru_lock); diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 609c49f492e..9f2f6469740 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1071,6 +1071,7 @@ void mem_cgroup_lru_del_list(struct page *page, enum lru_list lru) VM_BUG_ON(!memcg); mz = page_cgroup_zoneinfo(memcg, page); /* huge page split is done under lru_lock. so, we have no races. */ + VM_BUG_ON(MEM_CGROUP_ZSTAT(mz, lru) < (1 << compound_order(page))); MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page); } @@ -2465,9 +2466,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg, void mem_cgroup_split_huge_fixup(struct page *head) { struct page_cgroup *head_pc = lookup_page_cgroup(head); - struct mem_cgroup_per_zone *mz; struct page_cgroup *pc; - enum lru_list lru; int i; if (mem_cgroup_disabled()) @@ -2478,15 +2477,8 @@ void mem_cgroup_split_huge_fixup(struct page *head) smp_wmb();/* see __commit_charge() */ pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT; } - /* - * Tail pages will be added to LRU. - * We hold lru_lock,then,reduce counter directly. - */ - lru = page_lru(head); - mz = page_cgroup_zoneinfo(head_pc->mem_cgroup, head); - MEM_CGROUP_ZSTAT(mz, lru) -= HPAGE_PMD_NR - 1; } -#endif +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ /** * mem_cgroup_move_account - move account of the page diff --git a/mm/swap.c b/mm/swap.c index ddccf8e0b4a..db6defaf2e5 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -650,6 +650,7 @@ void __pagevec_release(struct pagevec *pvec) EXPORT_SYMBOL(__pagevec_release); +#ifdef CONFIG_TRANSPARENT_HUGEPAGE /* used by __split_huge_page_refcount() */ void lru_add_page_tail(struct zone* zone, struct page *page, struct page *page_tail) @@ -666,8 +667,6 @@ void lru_add_page_tail(struct zone* zone, SetPageLRU(page_tail); if (page_evictable(page_tail, NULL)) { - struct lruvec *lruvec; - if (PageActive(page)) { SetPageActive(page_tail); active = 1; @@ -677,18 +676,28 @@ void lru_add_page_tail(struct zone* zone, lru = LRU_INACTIVE_ANON; } update_page_reclaim_stat(zone, page_tail, file, active); - lruvec = mem_cgroup_lru_add_list(zone, page_tail, lru); - if (likely(PageLRU(page))) - list_add(&page_tail->lru, page->lru.prev); - else - list_add(&page_tail->lru, lruvec->lists[lru].prev); - __mod_zone_page_state(zone, NR_LRU_BASE + lru, - hpage_nr_pages(page_tail)); } else { SetPageUnevictable(page_tail); - add_page_to_lru_list(zone, page_tail, LRU_UNEVICTABLE); + lru = LRU_UNEVICTABLE; + } + + if (likely(PageLRU(page))) + list_add_tail(&page_tail->lru, &page->lru); + else { + struct list_head *list_head; + /* + * Head page has not yet been counted, as an hpage, + * so we must account for each subpage individually. + * + * Use the standard add function to put page_tail on the list, + * but then correct its position so they all end up in order. + */ + add_page_to_lru_list(zone, page_tail, lru); + list_head = page_tail->lru.prev; + list_move_tail(&page_tail->lru, list_head); } } +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ static void ____pagevec_lru_add_fn(struct page *page, void *arg) {