memcg: synchronized LRU

A big patch for changing memcg's LRU semantics.

Now,
  - page_cgroup is linked to mem_cgroup's its own LRU (per zone).

  - LRU of page_cgroup is not synchronous with global LRU.

  - page and page_cgroup is one-to-one and statically allocated.

  - To find page_cgroup is on what LRU, you have to check pc->mem_cgroup as
    - lru = page_cgroup_zoneinfo(pc, nid_of_pc, zid_of_pc);

  - SwapCache is handled.

And, when we handle LRU list of page_cgroup, we do following.

	pc = lookup_page_cgroup(page);
	lock_page_cgroup(pc); .....................(1)
	mz = page_cgroup_zoneinfo(pc);
	spin_lock(&mz->lru_lock);
	.....add to LRU
	spin_unlock(&mz->lru_lock);
	unlock_page_cgroup(pc);

But (1) is spin_lock and we have to be afraid of dead-lock with zone->lru_lock.
So, trylock() is used at (1), now. Without (1), we can't trust "mz" is correct.

This is a trial to remove this dirty nesting of locks.
This patch changes mz->lru_lock to be zone->lru_lock.
Then, above sequence will be written as

        spin_lock(&zone->lru_lock); # in vmscan.c or swap.c via global LRU
	mem_cgroup_add/remove/etc_lru() {
		pc = lookup_page_cgroup(page);
		mz = page_cgroup_zoneinfo(pc);
		if (PageCgroupUsed(pc)) {
			....add to LRU
		}
        spin_lock(&zone->lru_lock); # in vmscan.c or swap.c via global LRU

This is much simpler.
(*) We're safe even if we don't take lock_page_cgroup(pc). Because..
    1. When pc->mem_cgroup can be modified.
       - at charge.
       - at account_move().
    2. at charge
       the PCG_USED bit is not set before pc->mem_cgroup is fixed.
    3. at account_move()
       the page is isolated and not on LRU.

Pros.
  - easy for maintenance.
  - memcg can make use of laziness of pagevec.
  - we don't have to duplicated LRU/Active/Unevictable bit in page_cgroup.
  - LRU status of memcg will be synchronized with global LRU's one.
  - # of locks are reduced.
  - account_move() is simplified very much.
Cons.
  - may increase cost of LRU rotation.
    (no impact if memcg is not configured.)

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 141 insertions, 182 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2efcf38f3b73..8ce4e9e47959 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -36,6 +36,7 @@
 #include <linux/vmalloc.h>
 #include <linux/mm_inline.h>
 #include <linux/page_cgroup.h>
+#include "internal.h"
 
 #include <asm/uaccess.h>
 
@@ -100,7 +101,6 @@ struct mem_cgroup_per_zone {
         /*
          * spin_lock to protect the per cgroup LRU
          */
-        spinlock_t              lru_lock;
         struct list_head        lists[NR_LRU_LISTS];
         unsigned long           count[NR_LRU_LISTS];
 };
@@ -163,14 +163,12 @@ enum charge_type {
 /* only for here (for easy reading.) */
 #define PCGF_CACHE      (1UL << PCG_CACHE)
 #define PCGF_USED       (1UL << PCG_USED)
-#define PCGF_ACTIVE     (1UL << PCG_ACTIVE)
 #define PCGF_LOCK       (1UL << PCG_LOCK)
-#define PCGF_FILE       (1UL << PCG_FILE)
 static const unsigned long
 pcg_default_flags[NR_CHARGE_TYPE] = {
-        PCGF_CACHE | PCGF_FILE | PCGF_USED | PCGF_LOCK, /* File Cache */
-        PCGF_ACTIVE | PCGF_USED | PCGF_LOCK, /* Anon */
-        PCGF_ACTIVE | PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* Shmem */
+        PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* File Cache */
+        PCGF_USED | PCGF_LOCK, /* Anon */
+        PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* Shmem */
         0, /* FORCE */
 };
 
@@ -185,9 +183,6 @@ pcg_default_flags[NR_CHARGE_TYPE] = {
 static void mem_cgroup_get(struct mem_cgroup *mem);
 static void mem_cgroup_put(struct mem_cgroup *mem);
 
-/*
- * Always modified under lru lock. Then, not necessary to preempt_disable()
- */
 static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
                                          struct page_cgroup *pc,
                                          bool charge)
@@ -195,10 +190,9 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
         int val = (charge)? 1 : -1;
         struct mem_cgroup_stat *stat = &mem->stat;
         struct mem_cgroup_stat_cpu *cpustat;
+        int cpu = get_cpu();
 
-        VM_BUG_ON(!irqs_disabled());
-
-        cpustat = &stat->cpustat[smp_processor_id()];
+        cpustat = &stat->cpustat[cpu];
         if (PageCgroupCache(pc))
                 __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_CACHE, val);
         else
@@ -210,6 +204,7 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
         else
                 __mem_cgroup_stat_add_safe(cpustat,
                                 MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
+        put_cpu();
 }
 
 static struct mem_cgroup_per_zone *
@@ -264,80 +259,95 @@ struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
                                 struct mem_cgroup, css);
 }
 
-static void __mem_cgroup_remove_list(struct mem_cgroup_per_zone *mz,
-                        struct page_cgroup *pc)
-{
-        int lru = LRU_BASE;
+/*
+ * Following LRU functions are allowed to be used without PCG_LOCK.
+ * Operations are called by routine of global LRU independently from memcg.
+ * What we have to take care of here is validness of pc->mem_cgroup.
+ *
+ * Changes to pc->mem_cgroup happens when
+ * 1. charge
+ * 2. moving account
+ * In typical case, "charge" is done before add-to-lru. Exception is SwapCache.
+ * It is added to LRU before charge.
+ * If PCG_USED bit is not set, page_cgroup is not added to this private LRU.
+ * When moving account, the page is not on LRU. It's isolated.
+ */
 
-        if (PageCgroupUnevictable(pc))
-                lru = LRU_UNEVICTABLE;
-        else {
-                if (PageCgroupActive(pc))
-                        lru += LRU_ACTIVE;
-                if (PageCgroupFile(pc))
-                        lru += LRU_FILE;
-        }
+void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
+{
+        struct page_cgroup *pc;
+        struct mem_cgroup *mem;
+        struct mem_cgroup_per_zone *mz;
 
+        if (mem_cgroup_subsys.disabled)
+                return;
+        pc = lookup_page_cgroup(page);
+        /* can happen while we handle swapcache. */
+        if (list_empty(&pc->lru))
+                return;
+        mz = page_cgroup_zoneinfo(pc);
+        mem = pc->mem_cgroup;
         MEM_CGROUP_ZSTAT(mz, lru) -= 1;
-
-        mem_cgroup_charge_statistics(pc->mem_cgroup, pc, false);
-        list_del(&pc->lru);
+        list_del_init(&pc->lru);
+        return;
 }
 
-static void __mem_cgroup_add_list(struct mem_cgroup_per_zone *mz,
-                                struct page_cgroup *pc, bool hot)
+void mem_cgroup_del_lru(struct page *page)
 {
-        int lru = LRU_BASE;
+        mem_cgroup_del_lru_list(page, page_lru(page));
+}
 
-        if (PageCgroupUnevictable(pc))
-                lru = LRU_UNEVICTABLE;
-        else {
-                if (PageCgroupActive(pc))
-                        lru += LRU_ACTIVE;
-                if (PageCgroupFile(pc))
-                        lru += LRU_FILE;
-        }
+void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
+{
+        struct mem_cgroup_per_zone *mz;
+        struct page_cgroup *pc;
 
-        MEM_CGROUP_ZSTAT(mz, lru) += 1;
-        if (hot)
-                list_add(&pc->lru, &mz->lists[lru]);
-        else
-                list_add_tail(&pc->lru, &mz->lists[lru]);
+        if (mem_cgroup_subsys.disabled)
+                return;
 
-        mem_cgroup_charge_statistics(pc->mem_cgroup, pc, true);
+        pc = lookup_page_cgroup(page);
+        smp_rmb();
+        /* unused page is not rotated. */
+        if (!PageCgroupUsed(pc))
+                return;
+        mz = page_cgroup_zoneinfo(pc);
+        list_move(&pc->lru, &mz->lists[lru]);
 }
 
-static void __mem_cgroup_move_lists(struct page_cgroup *pc, enum lru_list lru)
+void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
 {
-        struct mem_cgroup_per_zone *mz = page_cgroup_zoneinfo(pc);
-        int active    = PageCgroupActive(pc);
-        int file      = PageCgroupFile(pc);
-        int unevictable = PageCgroupUnevictable(pc);
-        enum lru_list from = unevictable ? LRU_UNEVICTABLE :
-                                (LRU_FILE * !!file + !!active);
+        struct page_cgroup *pc;
+        struct mem_cgroup_per_zone *mz;
 
-        if (lru == from)
+        if (mem_cgroup_subsys.disabled)
+                return;
+        pc = lookup_page_cgroup(page);
+        /* barrier to sync with "charge" */
+        smp_rmb();
+        if (!PageCgroupUsed(pc))
                 return;
 
-        MEM_CGROUP_ZSTAT(mz, from) -= 1;
-        /*
-         * However this is done under mz->lru_lock, another flags, which
-         * are not related to LRU, will be modified from out-of-lock.
-         * We have to use atomic set/clear flags.
-         */
-        if (is_unevictable_lru(lru)) {
-                ClearPageCgroupActive(pc);
-                SetPageCgroupUnevictable(pc);
-        } else {
-                if (is_active_lru(lru))
-                        SetPageCgroupActive(pc);
-                else
-                        ClearPageCgroupActive(pc);
-                ClearPageCgroupUnevictable(pc);
-        }
-
+        mz = page_cgroup_zoneinfo(pc);
         MEM_CGROUP_ZSTAT(mz, lru) += 1;
-        list_move(&pc->lru, &mz->lists[lru]);
+        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.
+ */
+static void mem_cgroup_lru_fixup(struct page *page)
+{
+        if (!isolate_lru_page(page))
+                putback_lru_page(page);
+}
+
+void mem_cgroup_move_lists(struct page *page,
+                           enum lru_list from, enum lru_list to)
+{
+        if (mem_cgroup_subsys.disabled)
+                return;
+        mem_cgroup_del_lru_list(page, from);
+        mem_cgroup_add_lru_list(page, to);
 }
 
 int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
@@ -351,37 +361,6 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
 }
 
 /*
- * This routine assumes that the appropriate zone's lru lock is already held
- */
-void mem_cgroup_move_lists(struct page *page, enum lru_list lru)
-{
-        struct page_cgroup *pc;
-        struct mem_cgroup_per_zone *mz;
-        unsigned long flags;
-
-        if (mem_cgroup_subsys.disabled)
-                return;
-
-        /*
-         * We cannot lock_page_cgroup while holding zone's lru_lock,
-         * because other holders of lock_page_cgroup can be interrupted
-         * with an attempt to rotate_reclaimable_page.  But we cannot
-         * safely get to page_cgroup without it, so just try_lock it:
-         * mem_cgroup_isolate_pages allows for page left on wrong list.
-         */
-        pc = lookup_page_cgroup(page);
-        if (!trylock_page_cgroup(pc))
-                return;
-        if (pc && PageCgroupUsed(pc)) {
-                mz = page_cgroup_zoneinfo(pc);
-                spin_lock_irqsave(&mz->lru_lock, flags);
-                __mem_cgroup_move_lists(pc, lru);
-                spin_unlock_irqrestore(&mz->lru_lock, flags);
-        }
-        unlock_page_cgroup(pc);
-}
-
-/*
  * Calculate mapped_ratio under memory controller. This will be used in
  * vmscan.c for deteremining we have to reclaim mapped pages.
  */
@@ -460,40 +439,24 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
         mz = mem_cgroup_zoneinfo(mem_cont, nid, zid);
         src = &mz->lists[lru];
 
-        spin_lock(&mz->lru_lock);
         scan = 0;
         list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
                 if (scan >= nr_to_scan)
                         break;
+
+                page = pc->page;
                 if (unlikely(!PageCgroupUsed(pc)))
                         continue;
-                page = pc->page;
-
                 if (unlikely(!PageLRU(page)))
                         continue;
 
-                /*
-                 * TODO: play better with lumpy reclaim, grabbing anything.
-                 */
-                if (PageUnevictable(page) ||
-                    (PageActive(page) && !active) ||
-                    (!PageActive(page) && active)) {
-                        __mem_cgroup_move_lists(pc, page_lru(page));
-                        continue;
-                }
-
                 scan++;
-                list_move(&pc->lru, &pc_list);
-
                 if (__isolate_lru_page(page, mode, file) == 0) {
                         list_move(&page->lru, dst);
                         nr_taken++;
                 }
         }
 
-        list_splice(&pc_list, src);
-        spin_unlock(&mz->lru_lock);
-
         *scanned = scan;
         return nr_taken;
 }
@@ -608,9 +571,6 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
                                      struct page_cgroup *pc,
                                      enum charge_type ctype)
 {
-        struct mem_cgroup_per_zone *mz;
-        unsigned long flags;
-
         /* try_charge() can return NULL to *memcg, taking care of it. */
         if (!mem)
                 return;
@@ -625,17 +585,11 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
                 return;
         }
         pc->mem_cgroup = mem;
-        /*
-         * If a page is accounted as a page cache, insert to inactive list.
-         * If anon, insert to active list.
-         */
+        smp_wmb();
         pc->flags = pcg_default_flags[ctype];
 
-        mz = page_cgroup_zoneinfo(pc);
+        mem_cgroup_charge_statistics(mem, pc, true);
 
-        spin_lock_irqsave(&mz->lru_lock, flags);
-        __mem_cgroup_add_list(mz, pc, true);
-        spin_unlock_irqrestore(&mz->lru_lock, flags);
         unlock_page_cgroup(pc);
 }
 
@@ -646,8 +600,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
  * @to: mem_cgroup which the page is moved to. @from != @to.
  *
  * The caller must confirm following.
- * 1. disable irq.
- * 2. lru_lock of old mem_cgroup(@from) should be held.
+ * - page is not on LRU (isolate_page() is useful.)
  *
  * returns 0 at success,
  * returns -EBUSY when lock is busy or "pc" is unstable.
@@ -663,15 +616,14 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
         int nid, zid;
         int ret = -EBUSY;
 
-        VM_BUG_ON(!irqs_disabled());
         VM_BUG_ON(from == to);
+        VM_BUG_ON(PageLRU(pc->page));
 
         nid = page_cgroup_nid(pc);
         zid = page_cgroup_zid(pc);
         from_mz =  mem_cgroup_zoneinfo(from, nid, zid);
         to_mz =  mem_cgroup_zoneinfo(to, nid, zid);
 
-
         if (!trylock_page_cgroup(pc))
                 return ret;
 
@@ -681,18 +633,15 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
         if (pc->mem_cgroup != from)
                 goto out;
 
-        if (spin_trylock(&to_mz->lru_lock)) {
-                __mem_cgroup_remove_list(from_mz, pc);
-                css_put(&from->css);
-                res_counter_uncharge(&from->res, PAGE_SIZE);
-                if (do_swap_account)
-                        res_counter_uncharge(&from->memsw, PAGE_SIZE);
-                pc->mem_cgroup = to;
-                css_get(&to->css);
-                __mem_cgroup_add_list(to_mz, pc, false);
-                ret = 0;
-                spin_unlock(&to_mz->lru_lock);
-        }
+        css_put(&from->css);
+        res_counter_uncharge(&from->res, PAGE_SIZE);
+        mem_cgroup_charge_statistics(from, pc, false);
+        if (do_swap_account)
+                res_counter_uncharge(&from->memsw, PAGE_SIZE);
+        pc->mem_cgroup = to;
+        mem_cgroup_charge_statistics(to, pc, true);
+        css_get(&to->css);
+        ret = 0;
 out:
         unlock_page_cgroup(pc);
         return ret;
@@ -706,39 +655,47 @@ static int mem_cgroup_move_parent(struct page_cgroup *pc,
                                   struct mem_cgroup *child,
                                   gfp_t gfp_mask)
 {
+        struct page *page = pc->page;
         struct cgroup *cg = child->css.cgroup;
         struct cgroup *pcg = cg->parent;
         struct mem_cgroup *parent;
-        struct mem_cgroup_per_zone *mz;
-        unsigned long flags;
         int ret;
 
         /* Is ROOT ? */
         if (!pcg)
                 return -EINVAL;
 
+
         parent = mem_cgroup_from_cont(pcg);
 
+
         ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false);
         if (ret)
                 return ret;
 
-        mz = mem_cgroup_zoneinfo(child,
-                        page_cgroup_nid(pc), page_cgroup_zid(pc));
+        if (!get_page_unless_zero(page))
+                return -EBUSY;
+
+        ret = isolate_lru_page(page);
+
+        if (ret)
+                goto cancel;
 
-        spin_lock_irqsave(&mz->lru_lock, flags);
         ret = mem_cgroup_move_account(pc, child, parent);
-        spin_unlock_irqrestore(&mz->lru_lock, flags);
 
-        /* drop extra refcnt */
+        /* drop extra refcnt by try_charge() (move_account increment one) */
         css_put(&parent->css);
-        /* uncharge if move fails */
-        if (ret) {
-                res_counter_uncharge(&parent->res, PAGE_SIZE);
-                if (do_swap_account)
-                        res_counter_uncharge(&parent->memsw, PAGE_SIZE);
+        putback_lru_page(page);
+        if (!ret) {
+                put_page(page);
+                return 0;
         }
-
+        /* uncharge if move fails */
+cancel:
+        res_counter_uncharge(&parent->res, PAGE_SIZE);
+        if (do_swap_account)
+                res_counter_uncharge(&parent->memsw, PAGE_SIZE);
+        put_page(page);
         return ret;
 }
 
@@ -912,6 +869,8 @@ 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;
 }
@@ -944,6 +903,8 @@ 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)
@@ -968,7 +929,6 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
         struct page_cgroup *pc;
         struct mem_cgroup *mem = NULL;
         struct mem_cgroup_per_zone *mz;
-        unsigned long flags;
 
         if (mem_cgroup_subsys.disabled)
                 return NULL;
@@ -1010,12 +970,10 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
         if (do_swap_account && (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT))
                 res_counter_uncharge(&mem->memsw, PAGE_SIZE);
 
+        mem_cgroup_charge_statistics(mem, pc, false);
         ClearPageCgroupUsed(pc);
 
         mz = page_cgroup_zoneinfo(pc);
-        spin_lock_irqsave(&mz->lru_lock, flags);
-        __mem_cgroup_remove_list(mz, pc);
-        spin_unlock_irqrestore(&mz->lru_lock, flags);
         unlock_page_cgroup(pc);
 
         css_put(&mem->css);
@@ -1281,21 +1239,22 @@ int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
         return ret;
 }
 
-
 /*
  * This routine traverse page_cgroup in given list and drop them all.
  * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
  */
 static int mem_cgroup_force_empty_list(struct mem_cgroup *mem,
-                            struct mem_cgroup_per_zone *mz,
-                            enum lru_list lru)
+                                int node, int zid, enum lru_list lru)
 {
+        struct zone *zone;
+        struct mem_cgroup_per_zone *mz;
         struct page_cgroup *pc, *busy;
-        unsigned long flags;
-        unsigned long loop;
+        unsigned long flags, loop;
         struct list_head *list;
         int ret = 0;
 
+        zone = &NODE_DATA(node)->node_zones[zid];
+        mz = mem_cgroup_zoneinfo(mem, node, zid);
         list = &mz->lists[lru];
 
         loop = MEM_CGROUP_ZSTAT(mz, lru);
@@ -1304,19 +1263,19 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *mem,
         busy = NULL;
         while (loop--) {
                 ret = 0;
-                spin_lock_irqsave(&mz->lru_lock, flags);
+                spin_lock_irqsave(&zone->lru_lock, flags);
                 if (list_empty(list)) {
-                        spin_unlock_irqrestore(&mz->lru_lock, flags);
+                        spin_unlock_irqrestore(&zone->lru_lock, flags);
                         break;
                 }
                 pc = list_entry(list->prev, struct page_cgroup, lru);
                 if (busy == pc) {
                         list_move(&pc->lru, list);
                         busy = 0;
-                        spin_unlock_irqrestore(&mz->lru_lock, flags);
+                        spin_unlock_irqrestore(&zone->lru_lock, flags);
                         continue;
                 }
-                spin_unlock_irqrestore(&mz->lru_lock, flags);
+                spin_unlock_irqrestore(&zone->lru_lock, flags);
 
                 ret = mem_cgroup_move_parent(pc, mem, GFP_HIGHUSER_MOVABLE);
                 if (ret == -ENOMEM)
@@ -1329,6 +1288,7 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *mem,
                 } else
                         busy = NULL;
         }
+
         if (!ret && !list_empty(list))
                 return -EBUSY;
         return ret;
@@ -1364,12 +1324,10 @@ move_account:
                 ret = 0;
                 for_each_node_state(node, N_POSSIBLE) {
                         for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
-                                struct mem_cgroup_per_zone *mz;
                                 enum lru_list l;
-                                mz = mem_cgroup_zoneinfo(mem, node, zid);
                                 for_each_lru(l) {
                                         ret = mem_cgroup_force_empty_list(mem,
-                                                                  mz, l);
+                                                        node, zid, l);
                                         if (ret)
                                                 break;
                                 }
@@ -1413,6 +1371,7 @@ try_to_free:
                 }
 
         }
+        lru_add_drain();
         /* try move_account...there may be some *locked* pages. */
         if (mem->res.usage)
                 goto move_account;
@@ -1657,7 +1616,6 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
 
         for (zone = 0; zone < MAX_NR_ZONES; zone++) {
                 mz = &pn->zoneinfo[zone];
-                spin_lock_init(&mz->lru_lock);
                 for_each_lru(l)
                         INIT_LIST_HEAD(&mz->lists[l]);
         }
@@ -1706,8 +1664,15 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 
 static void mem_cgroup_free(struct mem_cgroup *mem)
 {
+        int node;
+
         if (atomic_read(&mem->refcnt) > 0)
                 return;
+
+
+        for_each_node_state(node, N_POSSIBLE)
+                free_mem_cgroup_per_zone_info(mem, node);
+
         if (mem_cgroup_size() < PAGE_SIZE)
                 kfree(mem);
         else
@@ -1780,12 +1745,6 @@ static void mem_cgroup_pre_destroy(struct cgroup_subsys *ss,
 static void mem_cgroup_destroy(struct cgroup_subsys *ss,
                                 struct cgroup *cont)
 {
-        int node;
-        struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
-
-        for_each_node_state(node, N_POSSIBLE)
-                free_mem_cgroup_per_zone_info(mem, node);
-
         mem_cgroup_free(mem_cgroup_from_cont(cont));
 }