diff options
| -rw-r--r-- | mm/memcontrol.c | 76 |
1 files changed, 48 insertions, 28 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 916132a29b36..5a1d584ffed3 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2702,10 +2702,27 @@ out: return ret; } -/* - * move charges to its parent. +/** + * mem_cgroup_move_parent - moves page to the parent group + * @page: the page to move + * @pc: page_cgroup of the page + * @child: page's cgroup + * + * move charges to its parent or the root cgroup if the group has no + * parent (aka use_hierarchy==0). + * Although this might fail (get_page_unless_zero, isolate_lru_page or + * mem_cgroup_move_account fails) the failure is always temporary and + * it signals a race with a page removal/uncharge or migration. In the + * first case the page is on the way out and it will vanish from the LRU + * on the next attempt and the call should be retried later. + * Isolation from the LRU fails only if page has been isolated from + * the LRU since we looked at it and that usually means either global + * reclaim or migration going on. The page will either get back to the + * LRU or vanish. + * Finaly mem_cgroup_move_account fails only if the page got uncharged + * (!PageCgroupUsed) or moved to a different group. The page will + * disappear in the next attempt. */ - static int mem_cgroup_move_parent(struct page *page, struct page_cgroup *pc, struct mem_cgroup *child) @@ -2732,8 +2749,10 @@ static int mem_cgroup_move_parent(struct page *page, if (!parent) parent = root_mem_cgroup; - if (nr_pages > 1) + if (nr_pages > 1) { + VM_BUG_ON(!PageTransHuge(page)); flags = compound_lock_irqsave(page); + } ret = mem_cgroup_move_account(page, nr_pages, pc, child, parent); @@ -3683,17 +3702,22 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order, return nr_reclaimed; } -/* +/** + * mem_cgroup_force_empty_list - clears LRU of a group + * @memcg: group to clear + * @node: NUMA node + * @zid: zone id + * @lru: lru to to clear + * * Traverse a specified page_cgroup list and try to drop them all. This doesn't - * reclaim the pages page themselves - it just removes the page_cgroups. - * Returns true if some page_cgroups were not freed, indicating that the caller - * must retry this operation. + * reclaim the pages page themselves - pages are moved to the parent (or root) + * group. */ -static bool mem_cgroup_force_empty_list(struct mem_cgroup *memcg, +static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg, int node, int zid, enum lru_list lru) { struct mem_cgroup_per_zone *mz; - unsigned long flags, loop; + unsigned long flags; struct list_head *list; struct page *busy; struct zone *zone; @@ -3702,11 +3726,8 @@ static bool mem_cgroup_force_empty_list(struct mem_cgroup *memcg, mz = mem_cgroup_zoneinfo(memcg, node, zid); list = &mz->lruvec.lists[lru]; - loop = mz->lru_size[lru]; - /* give some margin against EBUSY etc...*/ - loop += 256; busy = NULL; - while (loop--) { + do { struct page_cgroup *pc; struct page *page; @@ -3732,8 +3753,7 @@ static bool mem_cgroup_force_empty_list(struct mem_cgroup *memcg, cond_resched(); } else busy = NULL; - } - return !list_empty(list); + } while (!list_empty(list)); } /* @@ -3747,7 +3767,6 @@ static int mem_cgroup_reparent_charges(struct mem_cgroup *memcg) { struct cgroup *cgrp = memcg->css.cgroup; int node, zid; - int ret; do { if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children)) @@ -3755,28 +3774,30 @@ static int mem_cgroup_reparent_charges(struct mem_cgroup *memcg) /* This is for making all *used* pages to be on LRU. */ lru_add_drain_all(); drain_all_stock_sync(memcg); - ret = 0; mem_cgroup_start_move(memcg); for_each_node_state(node, N_HIGH_MEMORY) { - for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) { + for (zid = 0; zid < MAX_NR_ZONES; zid++) { enum lru_list lru; for_each_lru(lru) { - ret = mem_cgroup_force_empty_list(memcg, + mem_cgroup_force_empty_list(memcg, node, zid, lru); - if (ret) - break; } } - if (ret) - break; } mem_cgroup_end_move(memcg); memcg_oom_recover(memcg); cond_resched(); - /* "ret" should also be checked to ensure all lists are empty. */ - } while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0 || ret); - return ret; + /* + * This is a safety check because mem_cgroup_force_empty_list + * could have raced with mem_cgroup_replace_page_cache callers + * so the lru seemed empty but the page could have been added + * right after the check. RES_USAGE should be safe as we always + * charge before adding to the LRU. + */ + } while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0); + + return 0; } /* @@ -5618,7 +5639,6 @@ struct cgroup_subsys mem_cgroup_subsys = { .base_cftypes = mem_cgroup_files, .early_init = 0, .use_id = 1, - .__DEPRECATED_clear_css_refs = true, }; #ifdef CONFIG_MEMCG_SWAP |