From: KAMEZAWA Hiroyuki Date: Thu, 8 Jan 2009 02:08:34 +0000 (-0800) Subject: memcg: fix LRU accounting for SwapCache X-Git-Tag: v2.6.29-rc1~92 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=544122e5e0ee27d5aac4a441f7746712afbf248c;p=linux-2.6-omap-h63xx.git memcg: fix LRU accounting for SwapCache Now, a page can be deleted from SwapCache while do_swap_page(). memcg-fix-swap-accounting-leak-v3.patch handles that, but, LRU handling is still broken. (above behavior broke assumption of memcg-synchronized-lru patch.) This patch is a fix for LRU handling (especially for per-zone counters). At charging SwapCache, - Remove page_cgroup from LRU if it's not used. - Add page cgroup to LRU if it's not linked to. Reported-by: Daisuke Nishimura Signed-off-by: KAMEZAWA Hiroyuki Cc: Balbir Singh Cc: Paul Menage Cc: Li Zefan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/memcontrol.c b/mm/memcontrol.c index b311f19bbe0..f50cb7b1efd 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -331,8 +331,12 @@ void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru) return; pc = lookup_page_cgroup(page); /* can happen while we handle swapcache. */ - if (list_empty(&pc->lru)) + if (list_empty(&pc->lru) || !pc->mem_cgroup) return; + /* + * We don't check PCG_USED bit. It's cleared when the "page" is finally + * removed from global LRU. + */ mz = page_cgroup_zoneinfo(pc); mem = pc->mem_cgroup; MEM_CGROUP_ZSTAT(mz, lru) -= 1; @@ -379,16 +383,44 @@ void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru) MEM_CGROUP_ZSTAT(mz, lru) += 1; list_add(&pc->lru, &mz->lists[lru]); } + /* - * To add swapcache into LRU. Be careful to all this function. - * zone->lru_lock shouldn't be held and irq must not be disabled. + * At handling SwapCache, pc->mem_cgroup may be changed while it's linked to + * lru because the page may.be reused after it's fully uncharged (because of + * SwapCache behavior).To handle that, unlink page_cgroup from LRU when charge + * it again. This function is only used to charge SwapCache. It's done under + * lock_page and expected that zone->lru_lock is never held. */ -static void mem_cgroup_lru_fixup(struct page *page) +static void mem_cgroup_lru_del_before_commit_swapcache(struct page *page) +{ + unsigned long flags; + struct zone *zone = page_zone(page); + struct page_cgroup *pc = lookup_page_cgroup(page); + + spin_lock_irqsave(&zone->lru_lock, flags); + /* + * Forget old LRU when this page_cgroup is *not* used. This Used bit + * is guarded by lock_page() because the page is SwapCache. + */ + if (!PageCgroupUsed(pc)) + mem_cgroup_del_lru_list(page, page_lru(page)); + spin_unlock_irqrestore(&zone->lru_lock, flags); +} + +static void mem_cgroup_lru_add_after_commit_swapcache(struct page *page) { - if (!isolate_lru_page(page)) - putback_lru_page(page); + unsigned long flags; + struct zone *zone = page_zone(page); + struct page_cgroup *pc = lookup_page_cgroup(page); + + spin_lock_irqsave(&zone->lru_lock, flags); + /* link when the page is linked to LRU but page_cgroup isn't */ + if (PageLRU(page) && list_empty(&pc->lru)) + mem_cgroup_add_lru_list(page, page_lru(page)); + spin_unlock_irqrestore(&zone->lru_lock, flags); } + void mem_cgroup_move_lists(struct page *page, enum lru_list from, enum lru_list to) { @@ -1168,8 +1200,11 @@ int mem_cgroup_cache_charge_swapin(struct page *page, mem = NULL; /* charge to current */ } } + /* SwapCache may be still linked to LRU now. */ + mem_cgroup_lru_del_before_commit_swapcache(page); ret = mem_cgroup_charge_common(page, mm, mask, MEM_CGROUP_CHARGE_TYPE_SHMEM, mem); + mem_cgroup_lru_add_after_commit_swapcache(page); /* drop extra refcnt from tryget */ if (mem) css_put(&mem->css); @@ -1185,8 +1220,6 @@ int mem_cgroup_cache_charge_swapin(struct page *page, } if (!locked) unlock_page(page); - /* add this page(page_cgroup) to the LRU we want. */ - mem_cgroup_lru_fixup(page); return ret; } @@ -1201,7 +1234,9 @@ void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr) if (!ptr) return; pc = lookup_page_cgroup(page); + mem_cgroup_lru_del_before_commit_swapcache(page); __mem_cgroup_commit_charge(ptr, pc, MEM_CGROUP_CHARGE_TYPE_MAPPED); + mem_cgroup_lru_add_after_commit_swapcache(page); /* * Now swap is on-memory. This means this page may be * counted both as mem and swap....double count. @@ -1220,7 +1255,7 @@ void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr) } /* add this page(page_cgroup) to the LRU we want. */ - mem_cgroup_lru_fixup(page); + } void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem) @@ -1288,6 +1323,12 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) mem_cgroup_charge_statistics(mem, pc, false); ClearPageCgroupUsed(pc); + /* + * pc->mem_cgroup is not cleared here. It will be accessed when it's + * freed from LRU. This is safe because uncharged page is expected not + * to be reused (freed soon). Exception is SwapCache, it's handled by + * special functions. + */ mz = page_cgroup_zoneinfo(pc); unlock_page_cgroup(pc);