diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0e6484ea268d6be661f19db8e1cac31657f69d6c..f90e43c1499f0c79b03e89af5979caee63b30011 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1132,7 +1132,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
if (css == &root->css)
break;
- if (css_tryget_online(css)) {
+ if (css_tryget(css)) {
/*
* Make sure the memcg is initialized:
* mem_cgroup_css_online() orders the the
@@ -3316,79 +3316,6 @@ static int mem_cgroup_move_account(struct page *page,
return ret;
}
-/**
- * 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)
-{
- struct mem_cgroup *parent;
- unsigned int nr_pages;
- unsigned long uninitialized_var(flags);
- int ret;
-
- VM_BUG_ON(mem_cgroup_is_root(child));
-
- ret = -EBUSY;
- if (!get_page_unless_zero(page))
- goto out;
- if (isolate_lru_page(page))
- goto put;
-
- nr_pages = hpage_nr_pages(page);
-
- parent = parent_mem_cgroup(child);
- /*
- * If no parent, move charges to root cgroup.
- */
- if (!parent)
- parent = root_mem_cgroup;
-
- if (nr_pages > 1) {
- VM_BUG_ON_PAGE(!PageTransHuge(page), page);
- flags = compound_lock_irqsave(page);
- }
-
- ret = mem_cgroup_move_account(page, nr_pages,
- pc, child, parent);
- if (!ret) {
- if (!mem_cgroup_is_root(parent))
- css_get_many(&parent->css, nr_pages);
- /* Take charge off the local counters */
- page_counter_cancel(&child->memory, nr_pages);
- if (do_swap_account)
- page_counter_cancel(&child->memsw, nr_pages);
- css_put_many(&child->css, nr_pages);
- }
-
- if (nr_pages > 1)
- compound_unlock_irqrestore(page, flags);
- putback_lru_page(page);
-put:
- put_page(page);
-out:
- return ret;
-}
-
#ifdef CONFIG_MEMCG_SWAP
static void mem_cgroup_swap_statistics(struct mem_cgroup *memcg,
bool charge)
@@ -3682,105 +3609,6 @@ 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 - pages are moved to the parent (or root)
- * group.
- */
-static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
- int node, int zid, enum lru_list lru)
-{
- struct lruvec *lruvec;
- unsigned long flags;
- struct list_head *list;
- struct page *busy;
- struct zone *zone;
-
- zone = &NODE_DATA(node)->node_zones[zid];
- lruvec = mem_cgroup_zone_lruvec(zone, memcg);
- list = &lruvec->lists[lru];
-
- busy = NULL;
- do {
- struct page_cgroup *pc;
- struct page *page;
-
- spin_lock_irqsave(&zone->lru_lock, flags);
- if (list_empty(list)) {
- spin_unlock_irqrestore(&zone->lru_lock, flags);
- break;
- }
- page = list_entry(list->prev, struct page, lru);
- if (busy == page) {
- list_move(&page->lru, list);
- busy = NULL;
- spin_unlock_irqrestore(&zone->lru_lock, flags);
- continue;
- }
- spin_unlock_irqrestore(&zone->lru_lock, flags);
-
- pc = lookup_page_cgroup(page);
-
- if (mem_cgroup_move_parent(page, pc, memcg)) {
- /* found lock contention or "pc" is obsolete. */
- busy = page;
- } else
- busy = NULL;
- cond_resched();
- } while (!list_empty(list));
-}
-
-/*
- * make mem_cgroup's charge to be 0 if there is no task by moving
- * all the charges and pages to the parent.
- * This enables deleting this mem_cgroup.
- *
- * Caller is responsible for holding css reference on the memcg.
- */
-static void mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
-{
- int node, zid;
-
- do {
- /* This is for making all *used* pages to be on LRU. */
- lru_add_drain_all();
- drain_all_stock_sync(memcg);
- mem_cgroup_start_move(memcg);
- for_each_node_state(node, N_MEMORY) {
- for (zid = 0; zid < MAX_NR_ZONES; zid++) {
- enum lru_list lru;
- for_each_lru(lru) {
- mem_cgroup_force_empty_list(memcg,
- node, zid, lru);
- }
- }
- }
- mem_cgroup_end_move(memcg);
- memcg_oom_recover(memcg);
- cond_resched();
-
- /*
- * Kernel memory may not necessarily be trackable to a specific
- * process. So they are not migrated, and therefore we can't
- * expect their value to drop to 0 here.
- * Having res filled up with kmem only is enough.
- *
- * 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 (page_counter_read(&memcg->memory) -
- page_counter_read(&memcg->kmem) > 0);
-}
-
/*
* Test whether @memcg has children, dead or alive. Note that this
* function doesn't care whether @memcg has use_hierarchy enabled and
@@ -5323,7 +5151,6 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(css);
struct mem_cgroup_event *event, *tmp;
- struct cgroup_subsys_state *iter;
/*
* Unregister events and notify userspace.
@@ -5337,13 +5164,6 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
}
spin_unlock(&memcg->event_list_lock);
- /*
- * This requires that offlining is serialized. Right now that is
- * guaranteed because css_killed_work_fn() holds the cgroup_mutex.
- */
- css_for_each_descendant_post(iter, css)
- mem_cgroup_reparent_charges(mem_cgroup_from_css(iter));
-
memcg_unregister_all_caches(memcg);
vmpressure_cleanup(&memcg->vmpressure);
}
@@ -5351,42 +5171,6 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(css);
- /*
- * XXX: css_offline() would be where we should reparent all
- * memory to prepare the cgroup for destruction. However,
- * memcg does not do css_tryget_online() and page_counter charging
- * under the same RCU lock region, which means that charging
- * could race with offlining. Offlining only happens to
- * cgroups with no tasks in them but charges can show up
- * without any tasks from the swapin path when the target
- * memcg is looked up from the swapout record and not from the
- * current task as it usually is. A race like this can leak
- * charges and put pages with stale cgroup pointers into
- * circulation:
- *
- * #0 #1
- * lookup_swap_cgroup_id()
- * rcu_read_lock()
- * mem_cgroup_lookup()
- * css_tryget_online()
- * rcu_read_unlock()
- * disable css_tryget_online()
- * call_rcu()
- * offline_css()
- * reparent_charges()
- * page_counter_try_charge()
- * css_put()
- * css_free()
- * pc->mem_cgroup = dead memcg
- * add page to lru
- *
- * The bulk of the charges are still moved in offline_css() to
- * avoid pinning a lot of pages in case a long-term reference
- * like a swapout record is deferring the css_free() to long
- * after offlining. But this makes sure we catch any charges
- * made after offlining:
- */
- mem_cgroup_reparent_charges(memcg);
memcg_destroy_kmem(memcg);
__mem_cgroup_free(memcg);