Cross-Referenced Linux and Device Driver Code

   /* memcontrol.c - Memory Controller
    *
    * Copyright IBM Corporation, 2007
    * Author Balbir Singh <balbir@linux.vnet.ibm.com>
    *
    * Copyright 2007 OpenVZ SWsoft Inc
    * Author: Pavel Emelianov <xemul@openvz.org>
    *
    * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */
  
  #include <linux/res_counter.h>
  #include <linux/memcontrol.h>
  #include <linux/cgroup.h>
  #include <linux/mm.h>
  #include <linux/pagemap.h>
  #include <linux/smp.h>
  #include <linux/page-flags.h>
  #include <linux/backing-dev.h>
  #include <linux/bit_spinlock.h>
  #include <linux/rcupdate.h>
  #include <linux/limits.h>
  #include <linux/mutex.h>
  #include <linux/slab.h>
  #include <linux/swap.h>
  #include <linux/spinlock.h>
  #include <linux/fs.h>
  #include <linux/seq_file.h>
  #include <linux/vmalloc.h>
  #include <linux/mm_inline.h>
  #include <linux/page_cgroup.h>
  #include "internal.h"
  
  #include <asm/uaccess.h>
  
  struct cgroup_subsys mem_cgroup_subsys __read_mostly;
  #define MEM_CGROUP_RECLAIM_RETRIES      5
  
  #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
  /* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
  int do_swap_account __read_mostly;
  static int really_do_swap_account __initdata = 1; /* for remember boot option*/
  #else
  #define do_swap_account         (0)
  #endif
  
  static DEFINE_MUTEX(memcg_tasklist);    /* can be hold under cgroup_mutex */
  
  /*
   * Statistics for memory cgroup.
   */
  enum mem_cgroup_stat_index {
          /*
           * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
           */
          MEM_CGROUP_STAT_CACHE,     /* # of pages charged as cache */
          MEM_CGROUP_STAT_RSS,       /* # of pages charged as anon rss */
          MEM_CGROUP_STAT_MAPPED_FILE,  /* # of pages charged as file rss */
          MEM_CGROUP_STAT_PGPGIN_COUNT,   /* # of pages paged in */
          MEM_CGROUP_STAT_PGPGOUT_COUNT,  /* # of pages paged out */
  
          MEM_CGROUP_STAT_NSTATS,
  };
  
  struct mem_cgroup_stat_cpu {
          s64 count[MEM_CGROUP_STAT_NSTATS];
  } ____cacheline_aligned_in_smp;
  
  struct mem_cgroup_stat {
          struct mem_cgroup_stat_cpu cpustat[0];
  };
  
  /*
   * For accounting under irq disable, no need for increment preempt count.
   */
  static inline void __mem_cgroup_stat_add_safe(struct mem_cgroup_stat_cpu *stat,
                  enum mem_cgroup_stat_index idx, int val)
  {
          stat->count[idx] += val;
  }
  
  static s64 mem_cgroup_read_stat(struct mem_cgroup_stat *stat,
                  enum mem_cgroup_stat_index idx)
  {
          int cpu;
          s64 ret = 0;
          for_each_possible_cpu(cpu)
                  ret += stat->cpustat[cpu].count[idx];
          return ret;
  }
  
 static s64 mem_cgroup_local_usage(struct mem_cgroup_stat *stat)
 {
         s64 ret;
 
         ret = mem_cgroup_read_stat(stat, MEM_CGROUP_STAT_CACHE);
         ret += mem_cgroup_read_stat(stat, MEM_CGROUP_STAT_RSS);
         return ret;
 }
 
 /*
  * per-zone information in memory controller.
  */
 struct mem_cgroup_per_zone {
         /*
          * spin_lock to protect the per cgroup LRU
          */
         struct list_head        lists[NR_LRU_LISTS];
         unsigned long           count[NR_LRU_LISTS];
 
         struct zone_reclaim_stat reclaim_stat;
 };
 /* Macro for accessing counter */
 #define MEM_CGROUP_ZSTAT(mz, idx)       ((mz)->count[(idx)])
 
 struct mem_cgroup_per_node {
         struct mem_cgroup_per_zone zoneinfo[MAX_NR_ZONES];
 };
 
 struct mem_cgroup_lru_info {
         struct mem_cgroup_per_node *nodeinfo[MAX_NUMNODES];
 };
 
 /*
  * The memory controller data structure. The memory controller controls both
  * page cache and RSS per cgroup. We would eventually like to provide
  * statistics based on the statistics developed by Rik Van Riel for clock-pro,
  * to help the administrator determine what knobs to tune.
  *
  * TODO: Add a water mark for the memory controller. Reclaim will begin when
  * we hit the water mark. May be even add a low water mark, such that
  * no reclaim occurs from a cgroup at it's low water mark, this is
  * a feature that will be implemented much later in the future.
  */
 struct mem_cgroup {
         struct cgroup_subsys_state css;
         /*
          * the counter to account for memory usage
          */
         struct res_counter res;
         /*
          * the counter to account for mem+swap usage.
          */
         struct res_counter memsw;
         /*
          * Per cgroup active and inactive list, similar to the
          * per zone LRU lists.
          */
         struct mem_cgroup_lru_info info;
 
         /*
           protect against reclaim related member.
         */
         spinlock_t reclaim_param_lock;
 
         int     prev_priority;  /* for recording reclaim priority */
 
         /*
          * While reclaiming in a hiearchy, we cache the last child we
          * reclaimed from.
          */
         int last_scanned_child;
         /*
          * Should the accounting and control be hierarchical, per subtree?
          */
         bool use_hierarchy;
         unsigned long   last_oom_jiffies;
         atomic_t        refcnt;
 
         unsigned int    swappiness;
 
         /* set when res.limit == memsw.limit */
         bool            memsw_is_minimum;
 
         /*
          * statistics. This must be placed at the end of memcg.
          */
         struct mem_cgroup_stat stat;
 };
 
 enum charge_type {
         MEM_CGROUP_CHARGE_TYPE_CACHE = 0,
         MEM_CGROUP_CHARGE_TYPE_MAPPED,
         MEM_CGROUP_CHARGE_TYPE_SHMEM,   /* used by page migration of shmem */
         MEM_CGROUP_CHARGE_TYPE_FORCE,   /* used by force_empty */
         MEM_CGROUP_CHARGE_TYPE_SWAPOUT, /* for accounting swapcache */
         MEM_CGROUP_CHARGE_TYPE_DROP,    /* a page was unused swap cache */
         NR_CHARGE_TYPE,
 };
 
 /* only for here (for easy reading.) */
 #define PCGF_CACHE      (1UL << PCG_CACHE)
 #define PCGF_USED       (1UL << PCG_USED)
 #define PCGF_LOCK       (1UL << PCG_LOCK)
 static const unsigned long
 pcg_default_flags[NR_CHARGE_TYPE] = {
         PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* File Cache */
         PCGF_USED | PCGF_LOCK, /* Anon */
         PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* Shmem */
         0, /* FORCE */
 };
 
 /* for encoding cft->private value on file */
 #define _MEM                    (0)
 #define _MEMSWAP                (1)
 #define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
 #define MEMFILE_TYPE(val)       (((val) >> 16) & 0xffff)
 #define MEMFILE_ATTR(val)       ((val) & 0xffff)
 
 static void mem_cgroup_get(struct mem_cgroup *mem);
 static void mem_cgroup_put(struct mem_cgroup *mem);
 static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
 
 static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
                                          struct page_cgroup *pc,
                                          bool charge)
 {
         int val = (charge)? 1 : -1;
         struct mem_cgroup_stat *stat = &mem->stat;
         struct mem_cgroup_stat_cpu *cpustat;
         int cpu = get_cpu();
 
         cpustat = &stat->cpustat[cpu];
         if (PageCgroupCache(pc))
                 __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_CACHE, val);
         else
                 __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_RSS, val);
 
         if (charge)
                 __mem_cgroup_stat_add_safe(cpustat,
                                 MEM_CGROUP_STAT_PGPGIN_COUNT, 1);
         else
                 __mem_cgroup_stat_add_safe(cpustat,
                                 MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
         put_cpu();
 }
 
 static struct mem_cgroup_per_zone *
 mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
 {
         return &mem->info.nodeinfo[nid]->zoneinfo[zid];
 }
 
 static struct mem_cgroup_per_zone *
 page_cgroup_zoneinfo(struct page_cgroup *pc)
 {
         struct mem_cgroup *mem = pc->mem_cgroup;
         int nid = page_cgroup_nid(pc);
         int zid = page_cgroup_zid(pc);
 
         if (!mem)
                 return NULL;
 
         return mem_cgroup_zoneinfo(mem, nid, zid);
 }
 
 static unsigned long mem_cgroup_get_local_zonestat(struct mem_cgroup *mem,
                                         enum lru_list idx)
 {
         int nid, zid;
         struct mem_cgroup_per_zone *mz;
         u64 total = 0;
 
         for_each_online_node(nid)
                 for (zid = 0; zid < MAX_NR_ZONES; zid++) {
                         mz = mem_cgroup_zoneinfo(mem, nid, zid);
                         total += MEM_CGROUP_ZSTAT(mz, idx);
                 }
         return total;
 }
 
 static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
 {
         return container_of(cgroup_subsys_state(cont,
                                 mem_cgroup_subsys_id), struct mem_cgroup,
                                 css);
 }
 
 struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
 {
         /*
          * mm_update_next_owner() may clear mm->owner to NULL
          * if it races with swapoff, page migration, etc.
          * So this can be called with p == NULL.
          */
         if (unlikely(!p))
                 return NULL;
 
         return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
                                 struct mem_cgroup, css);
 }
 
 static struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
 {
         struct mem_cgroup *mem = NULL;
 
         if (!mm)
                 return NULL;
         /*
          * Because we have no locks, mm->owner's may be being moved to other
          * cgroup. We use css_tryget() here even if this looks
          * pessimistic (rather than adding locks here).
          */
         rcu_read_lock();
         do {
                 mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
                 if (unlikely(!mem))
                         break;
         } while (!css_tryget(&mem->css));
         rcu_read_unlock();
         return mem;
 }
 
 /*
  * Call callback function against all cgroup under hierarchy tree.
  */
 static int mem_cgroup_walk_tree(struct mem_cgroup *root, void *data,
                           int (*func)(struct mem_cgroup *, void *))
 {
         int found, ret, nextid;
         struct cgroup_subsys_state *css;
         struct mem_cgroup *mem;
 
         if (!root->use_hierarchy)
                 return (*func)(root, data);
 
         nextid = 1;
         do {
                 ret = 0;
                 mem = NULL;
 
                 rcu_read_lock();
                 css = css_get_next(&mem_cgroup_subsys, nextid, &root->css,
                                    &found);
                 if (css && css_tryget(css))
                         mem = container_of(css, struct mem_cgroup, css);
                 rcu_read_unlock();
 
                 if (mem) {
                         ret = (*func)(mem, data);
                         css_put(&mem->css);
                 }
                 nextid = found + 1;
         } while (!ret && css);
 
         return ret;
 }
 
 /*
  * 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.
  */
 
 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_disabled())
                 return;
         pc = lookup_page_cgroup(page);
         /* can happen while we handle swapcache. */
         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;
         list_del_init(&pc->lru);
         return;
 }
 
 void mem_cgroup_del_lru(struct page *page)
 {
         mem_cgroup_del_lru_list(page, page_lru(page));
 }
 
 void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
 {
         struct mem_cgroup_per_zone *mz;
         struct page_cgroup *pc;
 
         if (mem_cgroup_disabled())
                 return;
 
         pc = lookup_page_cgroup(page);
         /*
          * Used bit is set without atomic ops but after smp_wmb().
          * For making pc->mem_cgroup visible, insert smp_rmb() here.
          */
         smp_rmb();
         /* unused page is not rotated. */
         if (!PageCgroupUsed(pc))
                 return;
         mz = page_cgroup_zoneinfo(pc);
         list_move(&pc->lru, &mz->lists[lru]);
 }
 
 void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
 {
         struct page_cgroup *pc;
         struct mem_cgroup_per_zone *mz;
 
         if (mem_cgroup_disabled())
                 return;
         pc = lookup_page_cgroup(page);
         /*
          * Used bit is set without atomic ops but after smp_wmb().
          * For making pc->mem_cgroup visible, insert smp_rmb() here.
          */
         smp_rmb();
         if (!PageCgroupUsed(pc))
                 return;
 
         mz = page_cgroup_zoneinfo(pc);
         MEM_CGROUP_ZSTAT(mz, lru) += 1;
         list_add(&pc->lru, &mz->lists[lru]);
 }
 
 /*
  * 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_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)
 {
         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)
 {
         if (mem_cgroup_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)
 {
         int ret;
         struct mem_cgroup *curr = NULL;
 
         task_lock(task);
         rcu_read_lock();
         curr = try_get_mem_cgroup_from_mm(task->mm);
         rcu_read_unlock();
         task_unlock(task);
         if (!curr)
                 return 0;
         /*
          * We should check use_hierarchy of "mem" not "curr". Because checking
          * use_hierarchy of "curr" here make this function true if hierarchy is
          * enabled in "curr" and "curr" is a child of "mem" in *cgroup*
          * hierarchy(even if use_hierarchy is disabled in "mem").
          */
         if (mem->use_hierarchy)
                 ret = css_is_ancestor(&curr->css, &mem->css);
         else
                 ret = (curr == mem);
         css_put(&curr->css);
         return ret;
 }
 
 /*
  * prev_priority control...this will be used in memory reclaim path.
  */
 int mem_cgroup_get_reclaim_priority(struct mem_cgroup *mem)
 {
         int prev_priority;
 
         spin_lock(&mem->reclaim_param_lock);
         prev_priority = mem->prev_priority;
         spin_unlock(&mem->reclaim_param_lock);
 
         return prev_priority;
 }
 
 void mem_cgroup_note_reclaim_priority(struct mem_cgroup *mem, int priority)
 {
         spin_lock(&mem->reclaim_param_lock);
         if (priority < mem->prev_priority)
                 mem->prev_priority = priority;
         spin_unlock(&mem->reclaim_param_lock);
 }
 
 void mem_cgroup_record_reclaim_priority(struct mem_cgroup *mem, int priority)
 {
         spin_lock(&mem->reclaim_param_lock);
         mem->prev_priority = priority;
         spin_unlock(&mem->reclaim_param_lock);
 }
 
 static int calc_inactive_ratio(struct mem_cgroup *memcg, unsigned long *present_pages)
 {
         unsigned long active;
         unsigned long inactive;
         unsigned long gb;
         unsigned long inactive_ratio;
 
         inactive = mem_cgroup_get_local_zonestat(memcg, LRU_INACTIVE_ANON);
         active = mem_cgroup_get_local_zonestat(memcg, LRU_ACTIVE_ANON);
 
         gb = (inactive + active) >> (30 - PAGE_SHIFT);
         if (gb)
                 inactive_ratio = int_sqrt(10 * gb);
         else
                 inactive_ratio = 1;
 
         if (present_pages) {
                 present_pages[0] = inactive;
                 present_pages[1] = active;
         }
 
         return inactive_ratio;
 }
 
 int mem_cgroup_inactive_anon_is_low(struct mem_cgroup *memcg)
 {
         unsigned long active;
         unsigned long inactive;
         unsigned long present_pages[2];
         unsigned long inactive_ratio;
 
         inactive_ratio = calc_inactive_ratio(memcg, present_pages);
 
         inactive = present_pages[0];
         active = present_pages[1];
 
         if (inactive * inactive_ratio < active)
                 return 1;
 
         return 0;
 }
 
 int mem_cgroup_inactive_file_is_low(struct mem_cgroup *memcg)
 {
         unsigned long active;
         unsigned long inactive;
 
         inactive = mem_cgroup_get_local_zonestat(memcg, LRU_INACTIVE_FILE);
         active = mem_cgroup_get_local_zonestat(memcg, LRU_ACTIVE_FILE);
 
         return (active > inactive);
 }
 
 unsigned long mem_cgroup_zone_nr_pages(struct mem_cgroup *memcg,
                                        struct zone *zone,
                                        enum lru_list lru)
 {
         int nid = zone->zone_pgdat->node_id;
         int zid = zone_idx(zone);
         struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);
 
         return MEM_CGROUP_ZSTAT(mz, lru);
 }
 
 struct zone_reclaim_stat *mem_cgroup_get_reclaim_stat(struct mem_cgroup *memcg,
                                                       struct zone *zone)
 {
         int nid = zone->zone_pgdat->node_id;
         int zid = zone_idx(zone);
         struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);
 
         return &mz->reclaim_stat;
 }
 
 struct zone_reclaim_stat *
 mem_cgroup_get_reclaim_stat_from_page(struct page *page)
 {
         struct page_cgroup *pc;
         struct mem_cgroup_per_zone *mz;
 
         if (mem_cgroup_disabled())
                 return NULL;
 
         pc = lookup_page_cgroup(page);
         /*
          * Used bit is set without atomic ops but after smp_wmb().
          * For making pc->mem_cgroup visible, insert smp_rmb() here.
          */
         smp_rmb();
         if (!PageCgroupUsed(pc))
                 return NULL;
 
         mz = page_cgroup_zoneinfo(pc);
         if (!mz)
                 return NULL;
 
         return &mz->reclaim_stat;
 }
 
 unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
                                         struct list_head *dst,
                                         unsigned long *scanned, int order,
                                         int mode, struct zone *z,
                                         struct mem_cgroup *mem_cont,
                                         int active, int file)
 {
         unsigned long nr_taken = 0;
         struct page *page;
         unsigned long scan;
         LIST_HEAD(pc_list);
         struct list_head *src;
         struct page_cgroup *pc, *tmp;
         int nid = z->zone_pgdat->node_id;
         int zid = zone_idx(z);
         struct mem_cgroup_per_zone *mz;
         int lru = LRU_FILE * !!file + !!active;
         int ret;
 
         BUG_ON(!mem_cont);
         mz = mem_cgroup_zoneinfo(mem_cont, nid, zid);
         src = &mz->lists[lru];
 
         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;
                 if (unlikely(!PageLRU(page)))
                         continue;
 
                 scan++;
                 ret = __isolate_lru_page(page, mode, file);
                 switch (ret) {
                 case 0:
                         list_move(&page->lru, dst);
                         mem_cgroup_del_lru(page);
                         nr_taken++;
                         break;
                 case -EBUSY:
                         /* we don't affect global LRU but rotate in our LRU */
                         mem_cgroup_rotate_lru_list(page, page_lru(page));
                         break;
                 default:
                         break;
                 }
         }
 
         *scanned = scan;
         return nr_taken;
 }
 
 #define mem_cgroup_from_res_counter(counter, member)    \
         container_of(counter, struct mem_cgroup, member)
 
 static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem)
 {
         if (do_swap_account) {
                 if (res_counter_check_under_limit(&mem->res) &&
                         res_counter_check_under_limit(&mem->memsw))
                         return true;
         } else
                 if (res_counter_check_under_limit(&mem->res))
                         return true;
         return false;
 }
 
 static unsigned int get_swappiness(struct mem_cgroup *memcg)
 {
         struct cgroup *cgrp = memcg->css.cgroup;
         unsigned int swappiness;
 
         /* root ? */
         if (cgrp->parent == NULL)
                 return vm_swappiness;
 
         spin_lock(&memcg->reclaim_param_lock);
         swappiness = memcg->swappiness;
         spin_unlock(&memcg->reclaim_param_lock);
 
         return swappiness;
 }
 
 static int mem_cgroup_count_children_cb(struct mem_cgroup *mem, void *data)
 {
         int *val = data;
         (*val)++;
         return 0;
 }
 
 /**
  * mem_cgroup_print_mem_info: Called from OOM with tasklist_lock held in read mode.
  * @memcg: The memory cgroup that went over limit
  * @p: Task that is going to be killed
  *
  * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
  * enabled
  */
 void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 {
         struct cgroup *task_cgrp;
         struct cgroup *mem_cgrp;
         /*
          * Need a buffer in BSS, can't rely on allocations. The code relies
          * on the assumption that OOM is serialized for memory controller.
          * If this assumption is broken, revisit this code.
          */
         static char memcg_name[PATH_MAX];
         int ret;
 
         if (!memcg)
                 return;
 
 
         rcu_read_lock();
 
         mem_cgrp = memcg->css.cgroup;
         task_cgrp = task_cgroup(p, mem_cgroup_subsys_id);
 
         ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX);
         if (ret < 0) {
                 /*
                  * Unfortunately, we are unable to convert to a useful name
                  * But we'll still print out the usage information
                  */
                 rcu_read_unlock();
                 goto done;
         }
         rcu_read_unlock();
 
         printk(KERN_INFO "Task in %s killed", memcg_name);
 
         rcu_read_lock();
         ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
         if (ret < 0) {
                 rcu_read_unlock();
                 goto done;
         }
         rcu_read_unlock();
 
         /*
          * Continues from above, so we don't need an KERN_ level
          */
         printk(KERN_CONT " as a result of limit of %s\n", memcg_name);
 done:
 
         printk(KERN_INFO "memory: usage %llukB, limit %llukB, failcnt %llu\n",
                 res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
                 res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
                 res_counter_read_u64(&memcg->res, RES_FAILCNT));
         printk(KERN_INFO "memory+swap: usage %llukB, limit %llukB, "
                 "failcnt %llu\n",
                 res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
                 res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
                 res_counter_read_u64(&memcg->memsw, RES_FAILCNT));
 }
 
 /*
  * This function returns the number of memcg under hierarchy tree. Returns
  * 1(self count) if no children.
  */
 static int mem_cgroup_count_children(struct mem_cgroup *mem)
 {
         int num = 0;
         mem_cgroup_walk_tree(mem, &num, mem_cgroup_count_children_cb);
         return num;
 }
 
 /*
  * Visit the first child (need not be the first child as per the ordering
  * of the cgroup list, since we track last_scanned_child) of @mem and use
  * that to reclaim free pages from.
  */
 static struct mem_cgroup *
 mem_cgroup_select_victim(struct mem_cgroup *root_mem)
 {
         struct mem_cgroup *ret = NULL;
         struct cgroup_subsys_state *css;
         int nextid, found;
 
         if (!root_mem->use_hierarchy) {
                 css_get(&root_mem->css);
                 ret = root_mem;
         }
 
         while (!ret) {
                 rcu_read_lock();
                 nextid = root_mem->last_scanned_child + 1;
                 css = css_get_next(&mem_cgroup_subsys, nextid, &root_mem->css,
                                    &found);
                 if (css && css_tryget(css))
                         ret = container_of(css, struct mem_cgroup, css);
 
                 rcu_read_unlock();
                 /* Updates scanning parameter */
                 spin_lock(&root_mem->reclaim_param_lock);
                 if (!css) {
                         /* this means start scan from ID:1 */
                         root_mem->last_scanned_child = 0;
                 } else
                         root_mem->last_scanned_child = found;
                 spin_unlock(&root_mem->reclaim_param_lock);
         }
 
         return ret;
 }
 
 /*
  * Scan the hierarchy if needed to reclaim memory. We remember the last child
  * we reclaimed from, so that we don't end up penalizing one child extensively
  * based on its position in the children list.
  *
  * root_mem is the original ancestor that we've been reclaim from.
  *
  * We give up and return to the caller when we visit root_mem twice.
  * (other groups can be removed while we're walking....)
  *
  * If shrink==true, for avoiding to free too much, this returns immedieately.
  */
 static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
                                    gfp_t gfp_mask, bool noswap, bool shrink)
 {
         struct mem_cgroup *victim;
         int ret, total = 0;
         int loop = 0;
 
         /* If memsw_is_minimum==1, swap-out is of-no-use. */
         if (root_mem->memsw_is_minimum)
                 noswap = true;
 
         while (loop < 2) {
                 victim = mem_cgroup_select_victim(root_mem);
                 if (victim == root_mem)
                         loop++;
                 if (!mem_cgroup_local_usage(&victim->stat)) {
                         /* this cgroup's local usage == 0 */
                         css_put(&victim->css);
                         continue;
                 }
                 /* we use swappiness of local cgroup */
                 ret = try_to_free_mem_cgroup_pages(victim, gfp_mask, noswap,
                                                    get_swappiness(victim));
                 css_put(&victim->css);
                 /*
                  * At shrinking usage, we can't check we should stop here or
                  * reclaim more. It's depends on callers. last_scanned_child
                  * will work enough for keeping fairness under tree.
                  */
                 if (shrink)
                         return ret;
                 total += ret;
                 if (mem_cgroup_check_under_limit(root_mem))
                         return 1 + total;
         }
         return total;
 }
 
 bool mem_cgroup_oom_called(struct task_struct *task)
 {
         bool ret = false;
         struct mem_cgroup *mem;
         struct mm_struct *mm;
 
         rcu_read_lock();
         mm = task->mm;
         if (!mm)
                 mm = &init_mm;
         mem = mem_cgroup_from_task(rcu_dereference(mm->owner));
         if (mem && time_before(jiffies, mem->last_oom_jiffies + HZ/10))
                 ret = true;
         rcu_read_unlock();
         return ret;
 }
 
 static int record_last_oom_cb(struct mem_cgroup *mem, void *data)
 {
         mem->last_oom_jiffies = jiffies;
         return 0;
 }
 
 static void record_last_oom(struct mem_cgroup *mem)
 {
         mem_cgroup_walk_tree(mem, NULL, record_last_oom_cb);
 }
 
 /*
  * Currently used to update mapped file statistics, but the routine can be
  * generalized to update other statistics as well.
  */
 void mem_cgroup_update_mapped_file_stat(struct page *page, int val)
 {
         struct mem_cgroup *mem;
         struct mem_cgroup_stat *stat;
         struct mem_cgroup_stat_cpu *cpustat;
         int cpu;
         struct page_cgroup *pc;
 
         if (!page_is_file_cache(page))
                 return;
 
         pc = lookup_page_cgroup(page);
         if (unlikely(!pc))
                 return;
 
         lock_page_cgroup(pc);
         mem = pc->mem_cgroup;
         if (!mem)
                 goto done;
 
         if (!PageCgroupUsed(pc))
                 goto done;
 
         /*
          * Preemption is already disabled, we don't need get_cpu()
          */
         cpu = smp_processor_id();
         stat = &mem->stat;
         cpustat = &stat->cpustat[cpu];
 
         __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_MAPPED_FILE, val);
 done:
         unlock_page_cgroup(pc);
 }
 
 /*
  * Unlike exported interface, "oom" parameter is added. if oom==true,
  * oom-killer can be invoked.
  */
 static int __mem_cgroup_try_charge(struct mm_struct *mm,
                         gfp_t gfp_mask, struct mem_cgroup **memcg,
                         bool oom)
 {
         struct mem_cgroup *mem, *mem_over_limit;
         int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
         struct res_counter *fail_res;
 
         if (unlikely(test_thread_flag(TIF_MEMDIE))) {
                 /* Don't account this! */
                 *memcg = NULL;
                 return 0;
         }
 
         /*
          * We always charge the cgroup the mm_struct belongs to.
          * The mm_struct's mem_cgroup changes on task migration if the
          * thread group leader migrates. It's possible that mm is not
          * set, if so charge the init_mm (happens for pagecache usage).
          */
         mem = *memcg;
         if (likely(!mem)) {
                 mem = try_get_mem_cgroup_from_mm(mm);
                 *memcg = mem;
         } else {
                 css_get(&mem->css);
         }
         if (unlikely(!mem))
                 return 0;
 
         VM_BUG_ON(css_is_removed(&mem->css));
 
         while (1) {
                 int ret;
                 bool noswap = false;
 
                 ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res);
                 if (likely(!ret)) {
                         if (!do_swap_account)
                                 break;
                         ret = res_counter_charge(&mem->memsw, PAGE_SIZE,
                                                         &fail_res);
                         if (likely(!ret))
                                 break;
                         /* mem+swap counter fails */
                         res_counter_uncharge(&mem->res, PAGE_SIZE);
                         noswap = true;
                         mem_over_limit = mem_cgroup_from_res_counter(fail_res,
                                                                         memsw);
                 } else
                         /* mem counter fails */
                         mem_over_limit = mem_cgroup_from_res_counter(fail_res,
                                                                         res);
 
                 if (!(gfp_mask & __GFP_WAIT))
                         goto nomem;
 
                 ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, gfp_mask,
                                                         noswap, false);
                 if (ret)
                         continue;
 
                 /*
                  * try_to_free_mem_cgroup_pages() might not give us a full
                  * picture of reclaim. Some pages are reclaimed and might be
                  * moved to swap cache or just unmapped from the cgroup.
                  * Check the limit again to see if the reclaim reduced the
                  * current usage of the cgroup before giving up
                  *
                  */
                 if (mem_cgroup_check_under_limit(mem_over_limit))
                         continue;
 
                 if (!nr_retries--) {
                         if (oom) {
                                 mutex_lock(&memcg_tasklist);
                                 mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
                                 mutex_unlock(&memcg_tasklist);
                                 record_last_oom(mem_over_limit);
                         }
                         goto nomem;
                 }
         }
         return 0;
 nomem:
         css_put(&mem->css);
         return -ENOMEM;
 }
 
 
 /*
  * A helper function to get mem_cgroup from ID. must be called under
  * rcu_read_lock(). The caller must check css_is_removed() or some if
  * it's concern. (dropping refcnt from swap can be called against removed
  * memcg.)
  */
 static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
 {
         struct cgroup_subsys_state *css;
 
         /* ID 0 is unused ID */
         if (!id)
                 return NULL;
         css = css_lookup(&mem_cgroup_subsys, id);
         if (!css)
                 return NULL;
         return container_of(css, struct mem_cgroup, css);
 }
 
 static struct mem_cgroup *try_get_mem_cgroup_from_swapcache(struct page *page)
 {
         struct mem_cgroup *mem;
         struct page_cgroup *pc;
         unsigned short id;
         swp_entry_t ent;
 
         VM_BUG_ON(!PageLocked(page));
 
         if (!PageSwapCache(page))
                 return NULL;
 
         pc = lookup_page_cgroup(page);
         lock_page_cgroup(pc);
         if (PageCgroupUsed(pc)) {
                 mem = pc->mem_cgroup;
                 if (mem && !css_tryget(&mem->css))
                         mem = NULL;
         } else {
                 ent.val = page_private(page);
                 id = lookup_swap_cgroup(ent);
                 rcu_read_lock();
                 mem = mem_cgroup_lookup(id);
                 if (mem && !css_tryget(&mem->css))
                         mem = NULL;
                 rcu_read_unlock();
         }
         unlock_page_cgroup(pc);
         return mem;
 }
 
 /*
  * commit a charge got by __mem_cgroup_try_charge() and makes page_cgroup to be
  * USED state. If already USED, uncharge and return.
  */
 
 static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
                                      struct page_cgroup *pc,
                                      enum charge_type ctype)
 {
         /* try_charge() can return NULL to *memcg, taking care of it. */
         if (!mem)
                 return;
 
         lock_page_cgroup(pc);
         if (unlikely(PageCgroupUsed(pc))) {
                 unlock_page_cgroup(pc);
                 res_counter_uncharge(&mem->res, PAGE_SIZE);
                 if (do_swap_account)
                         res_counter_uncharge(&mem->memsw, PAGE_SIZE);
                 css_put(&mem->css);
                 return;
         }
         pc->mem_cgroup = mem;
         smp_wmb();
         pc->flags = pcg_default_flags[ctype];
 
         mem_cgroup_charge_statistics(mem, pc, true);
 
         unlock_page_cgroup(pc);
 }
 
 /**
  * mem_cgroup_move_account - move account of the page
  * @pc: page_cgroup of the page.
  * @from: mem_cgroup which the page is moved from.
  * @to: mem_cgroup which the page is moved to. @from != @to.
  *
  * The caller must confirm following.
  * - page is not on LRU (isolate_page() is useful.)
  *
  * returns 0 at success,
  * returns -EBUSY when lock is busy or "pc" is unstable.
  *
  * This function does "uncharge" from old cgroup but doesn't do "charge" to
  * new cgroup. It should be done by a caller.
  */
 
 static int mem_cgroup_move_account(struct page_cgroup *pc,
         struct mem_cgroup *from, struct mem_cgroup *to)
 {
         struct mem_cgroup_per_zone *from_mz, *to_mz;
         int nid, zid;
         int ret = -EBUSY;
         struct page *page;
         int cpu;
         struct mem_cgroup_stat *stat;
         struct mem_cgroup_stat_cpu *cpustat;
 
         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;
 
         if (!PageCgroupUsed(pc))
                 goto out;
 
         if (pc->mem_cgroup != from)
                 goto out;
 
         res_counter_uncharge(&from->res, PAGE_SIZE);
         mem_cgroup_charge_statistics(from, pc, false);
 
         page = pc->page;
         if (page_is_file_cache(page) && page_mapped(page)) {
                 cpu = smp_processor_id();
                 /* Update mapped_file data for mem_cgroup "from" */
                 stat = &from->stat;
                 cpustat = &stat->cpustat[cpu];
                 __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_MAPPED_FILE,
                                                 -1);
 
                 /* Update mapped_file data for mem_cgroup "to" */
                 stat = &to->stat;
                 cpustat = &stat->cpustat[cpu];
                 __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_MAPPED_FILE,
                                                 1);
         }
 
         if (do_swap_account)
                 res_counter_uncharge(&from->memsw, PAGE_SIZE);
         css_put(&from->css);
 
         css_get(&to->css);
         pc->mem_cgroup = to;
         mem_cgroup_charge_statistics(to, pc, true);
         ret = 0;
 out:
         unlock_page_cgroup(pc);
         /*
          * We charges against "to" which may not have any tasks. Then, "to"
          * can be under rmdir(). But in current implementation, caller of
          * this function is just force_empty() and it's garanteed that
          * "to" is never removed. So, we don't check rmdir status here.
          */
         return ret;
 }
 
 /*
  * move charges to its parent.
  */
 
 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;
         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 || !parent)
                 return ret;
 
         if (!get_page_unless_zero(page)) {
                 ret = -EBUSY;
                 goto uncharge;
         }
 
         ret = isolate_lru_page(page);
 
         if (ret)
                 goto cancel;
 
         ret = mem_cgroup_move_account(pc, child, parent);
 
         putback_lru_page(page);
         if (!ret) {
                 put_page(page);
                 /* drop extra refcnt by try_charge() */
                 css_put(&parent->css);
                 return 0;
         }
 
 cancel:
         put_page(page);
 uncharge:
         /* drop extra refcnt by try_charge() */
         css_put(&parent->css);
         /* uncharge if move fails */
         res_counter_uncharge(&parent->res, PAGE_SIZE);
         if (do_swap_account)
                 res_counter_uncharge(&parent->memsw, PAGE_SIZE);
         return ret;
 }
 
 /*
  * Charge the memory controller for page usage.
  * Return
  * 0 if the charge was successful
  * < 0 if the cgroup is over its limit
  */
 static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
                                 gfp_t gfp_mask, enum charge_type ctype,
                                 struct mem_cgroup *memcg)
 {
         struct mem_cgroup *mem;
         struct page_cgroup *pc;
         int ret;
 
         pc = lookup_page_cgroup(page);
         /* can happen at boot */
         if (unlikely(!pc))
                 return 0;
         prefetchw(pc);
 
         mem = memcg;
         ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, true);
         if (ret || !mem)
                 return ret;
 
         __mem_cgroup_commit_charge(mem, pc, ctype);
         return 0;
 }
 
 int mem_cgroup_newpage_charge(struct page *page,
                               struct mm_struct *mm, gfp_t gfp_mask)
 {
         if (mem_cgroup_disabled())
                 return 0;
         if (PageCompound(page))
                 return 0;
         /*
          * If already mapped, we don't have to account.
          * If page cache, page->mapping has address_space.
          * But page->mapping may have out-of-use anon_vma pointer,
          * detecit it by PageAnon() check. newly-mapped-anon's page->mapping
          * is NULL.
          */
         if (page_mapped(page) || (page->mapping && !PageAnon(page)))
                 return 0;
         if (unlikely(!mm))
                 mm = &init_mm;
         return mem_cgroup_charge_common(page, mm, gfp_mask,
                                 MEM_CGROUP_CHARGE_TYPE_MAPPED, NULL);
 }
 
 static void
 __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
                                         enum charge_type ctype);
 
 int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
                                 gfp_t gfp_mask)
 {
         struct mem_cgroup *mem = NULL;
         int ret;
 
         if (mem_cgroup_disabled())
                 return 0;
         if (PageCompound(page))
                 return 0;
         /*
          * Corner case handling. This is called from add_to_page_cache()
          * in usual. But some FS (shmem) precharges this page before calling it
          * and call add_to_page_cache() with GFP_NOWAIT.
          *
          * For GFP_NOWAIT case, the page may be pre-charged before calling
          * add_to_page_cache(). (See shmem.c) check it here and avoid to call
          * charge twice. (It works but has to pay a bit larger cost.)
          * And when the page is SwapCache, it should take swap information
          * into account. This is under lock_page() now.
          */
         if (!(gfp_mask & __GFP_WAIT)) {
                 struct page_cgroup *pc;
 
 
                 pc = lookup_page_cgroup(page);
                 if (!pc)
                         return 0;
                 lock_page_cgroup(pc);
                 if (PageCgroupUsed(pc)) {
                         unlock_page_cgroup(pc);
                         return 0;
                 }
                 unlock_page_cgroup(pc);
         }
 
         if (unlikely(!mm && !mem))
                 mm = &init_mm;
 
         if (page_is_file_cache(page))
                 return mem_cgroup_charge_common(page, mm, gfp_mask,
                                 MEM_CGROUP_CHARGE_TYPE_CACHE, NULL);
 
         /* shmem */
         if (PageSwapCache(page)) {
                 ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
                 if (!ret)
                         __mem_cgroup_commit_charge_swapin(page, mem,
                                         MEM_CGROUP_CHARGE_TYPE_SHMEM);
         } else
                 ret = mem_cgroup_charge_common(page, mm, gfp_mask,
                                         MEM_CGROUP_CHARGE_TYPE_SHMEM, mem);
 
         return ret;
 }
 
 /*
  * While swap-in, try_charge -> commit or cancel, the page is locked.
  * And when try_charge() successfully returns, one refcnt to memcg without
  * struct page_cgroup is aquired. This refcnt will be cumsumed by
  * "commit()" or removed by "cancel()"
  */
 int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
                                  struct page *page,
                                  gfp_t mask, struct mem_cgroup **ptr)
 {
         struct mem_cgroup *mem;
         int ret;
 
         if (mem_cgroup_disabled())
                 return 0;
 
         if (!do_swap_account)
                 goto charge_cur_mm;
         /*
          * A racing thread's fault, or swapoff, may have already updated
          * the pte, and even removed page from swap cache: return success
          * to go on to do_swap_page()'s pte_same() test, which should fail.
          */
         if (!PageSwapCache(page))
                 return 0;
         mem = try_get_mem_cgroup_from_swapcache(page);
         if (!mem)
                 goto charge_cur_mm;
         *ptr = mem;
         ret = __mem_cgroup_try_charge(NULL, mask, ptr, true);
         /* drop extra refcnt from tryget */
         css_put(&mem->css);
         return ret;
 charge_cur_mm:
         if (unlikely(!mm))
                 mm = &init_mm;
         return __mem_cgroup_try_charge(mm, mask, ptr, true);
 }
 
 static void
 __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
                                         enum charge_type ctype)
 {
         struct page_cgroup *pc;
 
         if (mem_cgroup_disabled())
                 return;
         if (!ptr)
                 return;
         cgroup_exclude_rmdir(&ptr->css);
         pc = lookup_page_cgroup(page);
         mem_cgroup_lru_del_before_commit_swapcache(page);
         __mem_cgroup_commit_charge(ptr, pc, ctype);
         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.
          * Fix it by uncharging from memsw. Basically, this SwapCache is stable
          * under lock_page(). But in do_swap_page()::memory.c, reuse_swap_page()
          * may call delete_from_swap_cache() before reach here.
          */
         if (do_swap_account && PageSwapCache(page)) {
                 swp_entry_t ent = {.val = page_private(page)};
                 unsigned short id;
                 struct mem_cgroup *memcg;
 
                 id = swap_cgroup_record(ent, 0);
                 rcu_read_lock();
                 memcg = mem_cgroup_lookup(id);
                 if (memcg) {
                         /*
                          * This recorded memcg can be obsolete one. So, avoid
                          * calling css_tryget
                          */
                         res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
                         mem_cgroup_put(memcg);
                 }
                 rcu_read_unlock();
         }
         /*
          * At swapin, we may charge account against cgroup which has no tasks.
          * So, rmdir()->pre_destroy() can be called while we do this charge.
          * In that case, we need to call pre_destroy() again. check it here.
          */
         cgroup_release_and_wakeup_rmdir(&ptr->css);
 }
 
 void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr)
 {
         __mem_cgroup_commit_charge_swapin(page, ptr,
                                         MEM_CGROUP_CHARGE_TYPE_MAPPED);
 }
 
 void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem)
 {
         if (mem_cgroup_disabled())
                 return;
         if (!mem)
                 return;
         res_counter_uncharge(&mem->res, PAGE_SIZE);
         if (do_swap_account)
                 res_counter_uncharge(&mem->memsw, PAGE_SIZE);
         css_put(&mem->css);
 }
 
 
 /*
  * uncharge if !page_mapped(page)
  */
 static struct mem_cgroup *
 __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;
 
         if (mem_cgroup_disabled())
                 return NULL;
 
         if (PageSwapCache(page))
                 return NULL;
 
         /*
          * Check if our page_cgroup is valid
          */
         pc = lookup_page_cgroup(page);
         if (unlikely(!pc || !PageCgroupUsed(pc)))
                 return NULL;
 
         lock_page_cgroup(pc);
 
         mem = pc->mem_cgroup;
 
         if (!PageCgroupUsed(pc))
                 goto unlock_out;
 
         switch (ctype) {
         case MEM_CGROUP_CHARGE_TYPE_MAPPED:
         case MEM_CGROUP_CHARGE_TYPE_DROP:
                 if (page_mapped(page))
                         goto unlock_out;
                 break;
         case MEM_CGROUP_CHARGE_TYPE_SWAPOUT:
                 if (!PageAnon(page)) {  /* Shared memory */
                         if (page->mapping && !page_is_file_cache(page))
                                 goto unlock_out;
                 } else if (page_mapped(page)) /* Anon */
                                 goto unlock_out;
                 break;
         default:
                 break;
         }
 
         res_counter_uncharge(&mem->res, PAGE_SIZE);
         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);
         /*
          * 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);
 
         /* at swapout, this memcg will be accessed to record to swap */
         if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
                 css_put(&mem->css);
 
         return mem;
 
 unlock_out:
         unlock_page_cgroup(pc);
         return NULL;
 }
 
 void mem_cgroup_uncharge_page(struct page *page)
 {
         /* early check. */
         if (page_mapped(page))
                 return;
         if (page->mapping && !PageAnon(page))
                 return;
         __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_MAPPED);
 }
 
 void mem_cgroup_uncharge_cache_page(struct page *page)
 {
         VM_BUG_ON(page_mapped(page));
         VM_BUG_ON(page->mapping);
         __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE);
 }
 
 #ifdef CONFIG_SWAP
 /*
  * called after __delete_from_swap_cache() and drop "page" account.
  * memcg information is recorded to swap_cgroup of "ent"
  */
 void
 mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
 {
         struct mem_cgroup *memcg;
         int ctype = MEM_CGROUP_CHARGE_TYPE_SWAPOUT;
 
         if (!swapout) /* this was a swap cache but the swap is unused ! */
                 ctype = MEM_CGROUP_CHARGE_TYPE_DROP;
 
         memcg = __mem_cgroup_uncharge_common(page, ctype);
 
         /* record memcg information */
         if (do_swap_account && swapout && memcg) {
                 swap_cgroup_record(ent, css_id(&memcg->css));
                 mem_cgroup_get(memcg);
         }
         if (swapout && memcg)
                 css_put(&memcg->css);
 }
 #endif
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 /*
  * called from swap_entry_free(). remove record in swap_cgroup and
  * uncharge "memsw" account.
  */
 void mem_cgroup_uncharge_swap(swp_entry_t ent)
 {
         struct mem_cgroup *memcg;
         unsigned short id;
 
         if (!do_swap_account)
                 return;
 
         id = swap_cgroup_record(ent, 0);
         rcu_read_lock();
         memcg = mem_cgroup_lookup(id);
         if (memcg) {
                 /*
                  * We uncharge this because swap is freed.
                  * This memcg can be obsolete one. We avoid calling css_tryget
                  */
                 res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
                 mem_cgroup_put(memcg);
         }
         rcu_read_unlock();
 }
 #endif
 
 /*
  * Before starting migration, account PAGE_SIZE to mem_cgroup that the old
  * page belongs to.
  */
 int mem_cgroup_prepare_migration(struct page *page, struct mem_cgroup **ptr)
 {
         struct page_cgroup *pc;
         struct mem_cgroup *mem = NULL;
         int ret = 0;
 
         if (mem_cgroup_disabled())
                 return 0;
 
         pc = lookup_page_cgroup(page);
         lock_page_cgroup(pc);
         if (PageCgroupUsed(pc)) {
                 mem = pc->mem_cgroup;
                 css_get(&mem->css);
         }
         unlock_page_cgroup(pc);
 
         if (mem) {
                 ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem, false);
                 css_put(&mem->css);
         }
         *ptr = mem;
         return ret;
 }
 
 /* remove redundant charge if migration failed*/
 void mem_cgroup_end_migration(struct mem_cgroup *mem,
                 struct page *oldpage, struct page *newpage)
 {
         struct page *target, *unused;
         struct page_cgroup *pc;
         enum charge_type ctype;
 
         if (!mem)
                 return;
         cgroup_exclude_rmdir(&mem->css);
         /* at migration success, oldpage->mapping is NULL. */
         if (oldpage->mapping) {
                 target = oldpage;
                 unused = NULL;
         } else {
                 target = newpage;
                 unused = oldpage;
         }
 
         if (PageAnon(target))
                 ctype = MEM_CGROUP_CHARGE_TYPE_MAPPED;
         else if (page_is_file_cache(target))
                 ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
         else
                 ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
 
         /* unused page is not on radix-tree now. */
         if (unused)
                 __mem_cgroup_uncharge_common(unused, ctype);
 
         pc = lookup_page_cgroup(target);
         /*
          * __mem_cgroup_commit_charge() check PCG_USED bit of page_cgroup.
          * So, double-counting is effectively avoided.
          */
         __mem_cgroup_commit_charge(mem, pc, ctype);
 
         /*
          * Both of oldpage and newpage are still under lock_page().
          * Then, we don't have to care about race in radix-tree.
          * But we have to be careful that this page is unmapped or not.
          *
          * There is a case for !page_mapped(). At the start of
          * migration, oldpage was mapped. But now, it's zapped.
          * But we know *target* page is not freed/reused under us.
          * mem_cgroup_uncharge_page() does all necessary checks.
          */
         if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
                 mem_cgroup_uncharge_page(target);
         /*
          * At migration, we may charge account against cgroup which has no tasks
          * So, rmdir()->pre_destroy() can be called while we do this charge.
          * In that case, we need to call pre_destroy() again. check it here.
          */
         cgroup_release_and_wakeup_rmdir(&mem->css);
 }
 
 /*
  * A call to try to shrink memory usage on charge failure at shmem's swapin.
  * Calling hierarchical_reclaim is not enough because we should update
  * last_oom_jiffies to prevent pagefault_out_of_memory from invoking global OOM.
  * Moreover considering hierarchy, we should reclaim from the mem_over_limit,
  * not from the memcg which this page would be charged to.
  * try_charge_swapin does all of these works properly.
  */
 int mem_cgroup_shmem_charge_fallback(struct page *page,
                             struct mm_struct *mm,
                             gfp_t gfp_mask)
 {
         struct mem_cgroup *mem = NULL;
         int ret;
 
         if (mem_cgroup_disabled())
                 return 0;
 
         ret = mem_cgroup_try_charge_swapin(mm, page, gfp_mask, &mem);
         if (!ret)
                 mem_cgroup_cancel_charge_swapin(mem); /* it does !mem check */
 
         return ret;
 }
 
 static DEFINE_MUTEX(set_limit_mutex);
 
 static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
                                 unsigned long long val)
 {
         int retry_count;
         int progress;
         u64 memswlimit;
         int ret = 0;
         int children = mem_cgroup_count_children(memcg);
         u64 curusage, oldusage;
 
         /*
          * For keeping hierarchical_reclaim simple, how long we should retry
          * is depends on callers. We set our retry-count to be function
          * of # of children which we should visit in this loop.
          */
         retry_count = MEM_CGROUP_RECLAIM_RETRIES * children;
 
         oldusage = res_counter_read_u64(&memcg->res, RES_USAGE);
 
         while (retry_count) {
                 if (signal_pending(current)) {
                         ret = -EINTR;
                         break;
                 }
                 /*
                  * Rather than hide all in some function, I do this in
                  * open coded manner. You see what this really does.
                  * We have to guarantee mem->res.limit < mem->memsw.limit.
                  */
                 mutex_lock(&set_limit_mutex);
                 memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
                 if (memswlimit < val) {
                         ret = -EINVAL;
                         mutex_unlock(&set_limit_mutex);
                         break;
                 }
                 ret = res_counter_set_limit(&memcg->res, val);
                 if (!ret) {
                         if (memswlimit == val)
                                 memcg->memsw_is_minimum = true;
                         else
                                 memcg->memsw_is_minimum = false;
                 }
                 mutex_unlock(&set_limit_mutex);
 
                 if (!ret)
                         break;
 
                 progress = mem_cgroup_hierarchical_reclaim(memcg, GFP_KERNEL,
                                                    false, true);
                 curusage = res_counter_read_u64(&memcg->res, RES_USAGE);
                 /* Usage is reduced ? */
                 if (curusage >= oldusage)
                         retry_count--;
                 else
                         oldusage = curusage;
         }
 
         return ret;
 }
 
 static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
                                         unsigned long long val)
 {
         int retry_count;
         u64 memlimit, oldusage, curusage;
         int children = mem_cgroup_count_children(memcg);
         int ret = -EBUSY;
 
         /* see mem_cgroup_resize_res_limit */
         retry_count = children * MEM_CGROUP_RECLAIM_RETRIES;
         oldusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
         while (retry_count) {
                 if (signal_pending(current)) {
                         ret = -EINTR;
                         break;
                 }
                 /*
                  * Rather than hide all in some function, I do this in
                  * open coded manner. You see what this really does.
                  * We have to guarantee mem->res.limit < mem->memsw.limit.
                  */
                 mutex_lock(&set_limit_mutex);
                 memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
                 if (memlimit > val) {
                         ret = -EINVAL;
                         mutex_unlock(&set_limit_mutex);
                         break;
                 }
                 ret = res_counter_set_limit(&memcg->memsw, val);
                 if (!ret) {
                         if (memlimit == val)
                                 memcg->memsw_is_minimum = true;
                         else
                                 memcg->memsw_is_minimum = false;
                 }
                 mutex_unlock(&set_limit_mutex);
 
                 if (!ret)
                         break;
 
                 mem_cgroup_hierarchical_reclaim(memcg, GFP_KERNEL, true, true);
                 curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
                 /* Usage is reduced ? */
                 if (curusage >= oldusage)
                         retry_count--;
                 else
                         oldusage = curusage;
         }
         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,
                                 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, 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);
         /* give some margin against EBUSY etc...*/
         loop += 256;
         busy = NULL;
         while (loop--) {
                 ret = 0;
                 spin_lock_irqsave(&zone->lru_lock, flags);
                 if (list_empty(list)) {
                         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(&zone->lru_lock, flags);
                         continue;
                 }
                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 
                 ret = mem_cgroup_move_parent(pc, mem, GFP_KERNEL);
                 if (ret == -ENOMEM)
                         break;
 
                 if (ret == -EBUSY || ret == -EINVAL) {
                         /* found lock contention or "pc" is obsolete. */
                         busy = pc;
                         cond_resched();
                 } else
                         busy = NULL;
         }
 
         if (!ret && !list_empty(list))
                 return -EBUSY;
         return ret;
 }
 
 /*
  * make mem_cgroup's charge to be 0 if there is no task.
  * This enables deleting this mem_cgroup.
  */
 static int mem_cgroup_force_empty(struct mem_cgroup *mem, bool free_all)
 {
         int ret;
         int node, zid, shrink;
         int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
         struct cgroup *cgrp = mem->css.cgroup;
 
         css_get(&mem->css);
 
         shrink = 0;
         /* should free all ? */
         if (free_all)
                 goto try_to_free;
 move_account:
         while (mem->res.usage > 0) {
                 ret = -EBUSY;
                 if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
                         goto out;
                 ret = -EINTR;
                 if (signal_pending(current))
                         goto out;
                 /* This is for making all *used* pages to be on LRU. */
                 lru_add_drain_all();
                 ret = 0;
                 for_each_node_state(node, N_HIGH_MEMORY) {
                         for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
                                 enum lru_list l;
                                 for_each_lru(l) {
                                         ret = mem_cgroup_force_empty_list(mem,
                                                         node, zid, l);
                                         if (ret)
                                                 break;
                                 }
                         }
                         if (ret)
                                 break;
                 }
                 /* it seems parent cgroup doesn't have enough mem */
                 if (ret == -ENOMEM)
                         goto try_to_free;
                 cond_resched();
         }
         ret = 0;
 out:
         css_put(&mem->css);
         return ret;
 
 try_to_free:
         /* returns EBUSY if there is a task or if we come here twice. */
         if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children) || shrink) {
                 ret = -EBUSY;
                 goto out;
         }
         /* we call try-to-free pages for make this cgroup empty */
         lru_add_drain_all();
         /* try to free all pages in this cgroup */
         shrink = 1;
         while (nr_retries && mem->res.usage > 0) {
                 int progress;
 
                 if (signal_pending(current)) {
                         ret = -EINTR;
                         goto out;
                 }
                 progress = try_to_free_mem_cgroup_pages(mem, GFP_KERNEL,
                                                 false, get_swappiness(mem));
                 if (!progress) {
                         nr_retries--;
                         /* maybe some writeback is necessary */
                         congestion_wait(BLK_RW_ASYNC, HZ/10);
                 }
 
         }
         lru_add_drain();
         /* try move_account...there may be some *locked* pages. */
         if (mem->res.usage)
                 goto move_account;
         ret = 0;
         goto out;
 }
 
 int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
 {
         return mem_cgroup_force_empty(mem_cgroup_from_cont(cont), true);
 }
 
 
 static u64 mem_cgroup_hierarchy_read(struct cgroup *cont, struct cftype *cft)
 {
         return mem_cgroup_from_cont(cont)->use_hierarchy;
 }
 
 static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
                                         u64 val)
 {
         int retval = 0;
         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
         struct cgroup *parent = cont->parent;
         struct mem_cgroup *parent_mem = NULL;
 
         if (parent)
                 parent_mem = mem_cgroup_from_cont(parent);
 
         cgroup_lock();
         /*
          * If parent's use_hiearchy is set, we can't make any modifications
          * in the child subtrees. If it is unset, then the change can
          * occur, provided the current cgroup has no children.
          *
          * For the root cgroup, parent_mem is NULL, we allow value to be
          * set if there are no children.
          */
         if ((!parent_mem || !parent_mem->use_hierarchy) &&
                                 (val == 1 || val == 0)) {
                 if (list_empty(&cont->children))
                         mem->use_hierarchy = val;
                 else
                         retval = -EBUSY;
         } else
                 retval = -EINVAL;
         cgroup_unlock();
 
         return retval;
 }
 
 static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
 {
         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
         u64 val = 0;
         int type, name;
 
         type = MEMFILE_TYPE(cft->private);
         name = MEMFILE_ATTR(cft->private);
         switch (type) {
         case _MEM:
                 val = res_counter_read_u64(&mem->res, name);
                 break;
         case _MEMSWAP:
                 val = res_counter_read_u64(&mem->memsw, name);
                 break;
         default:
                 BUG();
                 break;
         }
         return val;
 }
 /*
  * The user of this function is...
  * RES_LIMIT.
  */
 static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
                             const char *buffer)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
         int type, name;
         unsigned long long val;
         int ret;
 
         type = MEMFILE_TYPE(cft->private);
         name = MEMFILE_ATTR(cft->private);
         switch (name) {
         case RES_LIMIT:
                 /* This function does all necessary parse...reuse it */
                 ret = res_counter_memparse_write_strategy(buffer, &val);
                 if (ret)
                         break;
                 if (type == _MEM)
                         ret = mem_cgroup_resize_limit(memcg, val);
                 else
                         ret = mem_cgroup_resize_memsw_limit(memcg, val);
                 break;
         default:
                 ret = -EINVAL; /* should be BUG() ? */
                 break;
         }
         return ret;
 }
 
 static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
                 unsigned long long *mem_limit, unsigned long long *memsw_limit)
 {
         struct cgroup *cgroup;
         unsigned long long min_limit, min_memsw_limit, tmp;
 
         min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
         min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
         cgroup = memcg->css.cgroup;
         if (!memcg->use_hierarchy)
                 goto out;
 
         while (cgroup->parent) {
                 cgroup = cgroup->parent;
                 memcg = mem_cgroup_from_cont(cgroup);
                 if (!memcg->use_hierarchy)
                         break;
                 tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
                 min_limit = min(min_limit, tmp);
                 tmp = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
                 min_memsw_limit = min(min_memsw_limit, tmp);
         }
 out:
         *mem_limit = min_limit;
         *memsw_limit = min_memsw_limit;
         return;
 }
 
 static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
 {
         struct mem_cgroup *mem;
         int type, name;
 
         mem = mem_cgroup_from_cont(cont);
         type = MEMFILE_TYPE(event);
         name = MEMFILE_ATTR(event);
         switch (name) {
         case RES_MAX_USAGE:
                 if (type == _MEM)
                         res_counter_reset_max(&mem->res);
                 else
                         res_counter_reset_max(&mem->memsw);
                 break;
         case RES_FAILCNT:
                 if (type == _MEM)
                         res_counter_reset_failcnt(&mem->res);
                 else
                         res_counter_reset_failcnt(&mem->memsw);
                 break;
         }
         return 0;
 }
 
 
 /* For read statistics */
 enum {
         MCS_CACHE,
         MCS_RSS,
         MCS_MAPPED_FILE,
         MCS_PGPGIN,
         MCS_PGPGOUT,
         MCS_INACTIVE_ANON,
         MCS_ACTIVE_ANON,
         MCS_INACTIVE_FILE,
         MCS_ACTIVE_FILE,
         MCS_UNEVICTABLE,
         NR_MCS_STAT,
 };
 
 struct mcs_total_stat {
         s64 stat[NR_MCS_STAT];
 };
 
 struct {
         char *local_name;
         char *total_name;
 } memcg_stat_strings[NR_MCS_STAT] = {
         {"cache", "total_cache"},
         {"rss", "total_rss"},
         {"mapped_file", "total_mapped_file"},
         {"pgpgin", "total_pgpgin"},
         {"pgpgout", "total_pgpgout"},
         {"inactive_anon", "total_inactive_anon"},
         {"active_anon", "total_active_anon"},
         {"inactive_file", "total_inactive_file"},
         {"active_file", "total_active_file"},
         {"unevictable", "total_unevictable"}
 };
 
 
 static int mem_cgroup_get_local_stat(struct mem_cgroup *mem, void *data)
 {
         struct mcs_total_stat *s = data;
         s64 val;
 
         /* per cpu stat */
         val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_CACHE);
         s->stat[MCS_CACHE] += val * PAGE_SIZE;
         val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_RSS);
         s->stat[MCS_RSS] += val * PAGE_SIZE;
         val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_MAPPED_FILE);
         s->stat[MCS_MAPPED_FILE] += val * PAGE_SIZE;
         val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_PGPGIN_COUNT);
         s->stat[MCS_PGPGIN] += val;
         val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_PGPGOUT_COUNT);
         s->stat[MCS_PGPGOUT] += val;
 
         /* per zone stat */
         val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON);
         s->stat[MCS_INACTIVE_ANON] += val * PAGE_SIZE;
         val = mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_ANON);
         s->stat[MCS_ACTIVE_ANON] += val * PAGE_SIZE;
         val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_FILE);
         s->stat[MCS_INACTIVE_FILE] += val * PAGE_SIZE;
         val = mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_FILE);
         s->stat[MCS_ACTIVE_FILE] += val * PAGE_SIZE;
         val = mem_cgroup_get_local_zonestat(mem, LRU_UNEVICTABLE);
         s->stat[MCS_UNEVICTABLE] += val * PAGE_SIZE;
         return 0;
 }
 
 static void
 mem_cgroup_get_total_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
 {
         mem_cgroup_walk_tree(mem, s, mem_cgroup_get_local_stat);
 }
 
 static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
                                  struct cgroup_map_cb *cb)
 {
         struct mem_cgroup *mem_cont = mem_cgroup_from_cont(cont);
         struct mcs_total_stat mystat;
         int i;
 
         memset(&mystat, 0, sizeof(mystat));
         mem_cgroup_get_local_stat(mem_cont, &mystat);
 
         for (i = 0; i < NR_MCS_STAT; i++)
                 cb->fill(cb, memcg_stat_strings[i].local_name, mystat.stat[i]);
 
         /* Hierarchical information */
         {
                 unsigned long long limit, memsw_limit;
                 memcg_get_hierarchical_limit(mem_cont, &limit, &memsw_limit);
                 cb->fill(cb, "hierarchical_memory_limit", limit);
                 if (do_swap_account)
                         cb->fill(cb, "hierarchical_memsw_limit", memsw_limit);
         }
 
         memset(&mystat, 0, sizeof(mystat));
         mem_cgroup_get_total_stat(mem_cont, &mystat);
         for (i = 0; i < NR_MCS_STAT; i++)
                 cb->fill(cb, memcg_stat_strings[i].total_name, mystat.stat[i]);
 
 
 #ifdef CONFIG_DEBUG_VM
         cb->fill(cb, "inactive_ratio", calc_inactive_ratio(mem_cont, NULL));
 
         {
                 int nid, zid;
                 struct mem_cgroup_per_zone *mz;
                 unsigned long recent_rotated[2] = {0, 0};
                 unsigned long recent_scanned[2] = {0, 0};
 
                 for_each_online_node(nid)
                         for (zid = 0; zid < MAX_NR_ZONES; zid++) {
                                 mz = mem_cgroup_zoneinfo(mem_cont, nid, zid);
 
                                 recent_rotated[0] +=
                                         mz->reclaim_stat.recent_rotated[0];
                                 recent_rotated[1] +=
                                         mz->reclaim_stat.recent_rotated[1];
                                 recent_scanned[0] +=
                                         mz->reclaim_stat.recent_scanned[0];
                                 recent_scanned[1] +=
                                         mz->reclaim_stat.recent_scanned[1];
                         }
                 cb->fill(cb, "recent_rotated_anon", recent_rotated[0]);
                 cb->fill(cb, "recent_rotated_file", recent_rotated[1]);
                 cb->fill(cb, "recent_scanned_anon", recent_scanned[0]);
                 cb->fill(cb, "recent_scanned_file", recent_scanned[1]);
         }
 #endif
 
         return 0;
 }
 
 static u64 mem_cgroup_swappiness_read(struct cgroup *cgrp, struct cftype *cft)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
 
         return get_swappiness(memcg);
 }
 
 static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
                                        u64 val)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
         struct mem_cgroup *parent;
 
         if (val > 100)
                 return -EINVAL;
 
         if (cgrp->parent == NULL)
                 return -EINVAL;
 
         parent = mem_cgroup_from_cont(cgrp->parent);
 
         cgroup_lock();
 
         /* If under hierarchy, only empty-root can set this value */
         if ((parent->use_hierarchy) ||
             (memcg->use_hierarchy && !list_empty(&cgrp->children))) {
                 cgroup_unlock();
                 return -EINVAL;
         }
 
         spin_lock(&memcg->reclaim_param_lock);
         memcg->swappiness = val;
         spin_unlock(&memcg->reclaim_param_lock);
 
         cgroup_unlock();
 
         return 0;
 }
 
 
 static struct cftype mem_cgroup_files[] = {
         {
                 .name = "usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
                 .read_u64 = mem_cgroup_read,
         },
         {
                 .name = "max_usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEM, RES_MAX_USAGE),
                 .trigger = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read,
         },
         {
                 .name = "limit_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEM, RES_LIMIT),
                 .write_string = mem_cgroup_write,
                 .read_u64 = mem_cgroup_read,
         },
         {
                 .name = "failcnt",
                 .private = MEMFILE_PRIVATE(_MEM, RES_FAILCNT),
                 .trigger = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read,
         },
         {
                 .name = "stat",
                 .read_map = mem_control_stat_show,
         },
         {
                 .name = "force_empty",
                 .trigger = mem_cgroup_force_empty_write,
         },
         {
                 .name = "use_hierarchy",
                 .write_u64 = mem_cgroup_hierarchy_write,
                 .read_u64 = mem_cgroup_hierarchy_read,
         },
         {
                 .name = "swappiness",
                 .read_u64 = mem_cgroup_swappiness_read,
                 .write_u64 = mem_cgroup_swappiness_write,
         },
 };
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 static struct cftype memsw_cgroup_files[] = {
         {
                 .name = "memsw.usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
                 .read_u64 = mem_cgroup_read,
         },
         {
                 .name = "memsw.max_usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
                 .trigger = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read,
         },
         {
                 .name = "memsw.limit_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_LIMIT),
                 .write_string = mem_cgroup_write,
                 .read_u64 = mem_cgroup_read,
         },
         {
                 .name = "memsw.failcnt",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
                 .trigger = mem_cgroup_reset,
                 .read_u64 = mem_cgroup_read,
         },
 };
 
 static int register_memsw_files(struct cgroup *cont, struct cgroup_subsys *ss)
 {
         if (!do_swap_account)
                 return 0;
         return cgroup_add_files(cont, ss, memsw_cgroup_files,
                                 ARRAY_SIZE(memsw_cgroup_files));
 };
 #else
 static int register_memsw_files(struct cgroup *cont, struct cgroup_subsys *ss)
 {
         return 0;
 }
 #endif
 
 static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
 {
         struct mem_cgroup_per_node *pn;
         struct mem_cgroup_per_zone *mz;
         enum lru_list l;
         int zone, tmp = node;
         /*
          * This routine is called against possible nodes.
          * But it's BUG to call kmalloc() against offline node.
          *
          * TODO: this routine can waste much memory for nodes which will
          *       never be onlined. It's better to use memory hotplug callback
          *       function.
          */
         if (!node_state(node, N_NORMAL_MEMORY))
                 tmp = -1;
         pn = kmalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
         if (!pn)
                 return 1;
 
         mem->info.nodeinfo[node] = pn;
         memset(pn, 0, sizeof(*pn));
 
         for (zone = 0; zone < MAX_NR_ZONES; zone++) {
                 mz = &pn->zoneinfo[zone];
                 for_each_lru(l)
                         INIT_LIST_HEAD(&mz->lists[l]);
         }
         return 0;
 }
 
 static void free_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
 {
         kfree(mem->info.nodeinfo[node]);
 }
 
 static int mem_cgroup_size(void)
 {
         int cpustat_size = nr_cpu_ids * sizeof(struct mem_cgroup_stat_cpu);
         return sizeof(struct mem_cgroup) + cpustat_size;
 }
 
 static struct mem_cgroup *mem_cgroup_alloc(void)
 {
         struct mem_cgroup *mem;
         int size = mem_cgroup_size();
 
         if (size < PAGE_SIZE)
                 mem = kmalloc(size, GFP_KERNEL);
         else
                 mem = vmalloc(size);
 
         if (mem)
                 memset(mem, 0, size);
         return mem;
 }
 
 /*
  * At destroying mem_cgroup, references from swap_cgroup can remain.
  * (scanning all at force_empty is too costly...)
  *
  * Instead of clearing all references at force_empty, we remember
  * the number of reference from swap_cgroup and free mem_cgroup when
  * it goes down to 0.
  *
  * Removal of cgroup itself succeeds regardless of refs from swap.
  */
 
 static void __mem_cgroup_free(struct mem_cgroup *mem)
 {
         int node;
 
         free_css_id(&mem_cgroup_subsys, &mem->css);
 
         for_each_node_state(node, N_POSSIBLE)
                 free_mem_cgroup_per_zone_info(mem, node);
 
         if (mem_cgroup_size() < PAGE_SIZE)
                 kfree(mem);
         else
                 vfree(mem);
 }
 
 static void mem_cgroup_get(struct mem_cgroup *mem)
 {
         atomic_inc(&mem->refcnt);
 }
 
 static void mem_cgroup_put(struct mem_cgroup *mem)
 {
         if (atomic_dec_and_test(&mem->refcnt)) {
                 struct mem_cgroup *parent = parent_mem_cgroup(mem);
                 __mem_cgroup_free(mem);
                 if (parent)
                         mem_cgroup_put(parent);
         }
 }
 
 /*
  * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.
  */
 static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem)
 {
         if (!mem->res.parent)
                 return NULL;
         return mem_cgroup_from_res_counter(mem->res.parent, res);
 }
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 static void __init enable_swap_cgroup(void)
 {
         if (!mem_cgroup_disabled() && really_do_swap_account)
                 do_swap_account = 1;
 }
 #else
 static void __init enable_swap_cgroup(void)
 {
 }
 #endif
 
 static struct cgroup_subsys_state * __ref
 mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 {
         struct mem_cgroup *mem, *parent;
         long error = -ENOMEM;
         int node;
 
         mem = mem_cgroup_alloc();
         if (!mem)
                 return ERR_PTR(error);
 
         for_each_node_state(node, N_POSSIBLE)
                 if (alloc_mem_cgroup_per_zone_info(mem, node))
                         goto free_out;
         /* root ? */
         if (cont->parent == NULL) {
                 enable_swap_cgroup();
                 parent = NULL;
         } else {
                 parent = mem_cgroup_from_cont(cont->parent);
                 mem->use_hierarchy = parent->use_hierarchy;
         }
 
         if (parent && parent->use_hierarchy) {
                 res_counter_init(&mem->res, &parent->res);
                 res_counter_init(&mem->memsw, &parent->memsw);
                 /*
                  * We increment refcnt of the parent to ensure that we can
                  * safely access it on res_counter_charge/uncharge.
                  * This refcnt will be decremented when freeing this
                  * mem_cgroup(see mem_cgroup_put).
                  */
                 mem_cgroup_get(parent);
         } else {
                 res_counter_init(&mem->res, NULL);
                 res_counter_init(&mem->memsw, NULL);
         }
         mem->last_scanned_child = 0;
         spin_lock_init(&mem->reclaim_param_lock);
 
         if (parent)
                 mem->swappiness = get_swappiness(parent);
         atomic_set(&mem->refcnt, 1);
         return &mem->css;
 free_out:
         __mem_cgroup_free(mem);
         return ERR_PTR(error);
 }
 
 static int mem_cgroup_pre_destroy(struct cgroup_subsys *ss,
                                         struct cgroup *cont)
 {
         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
 
         return mem_cgroup_force_empty(mem, false);
 }
 
 static void mem_cgroup_destroy(struct cgroup_subsys *ss,
                                 struct cgroup *cont)
 {
         struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
 
         mem_cgroup_put(mem);
 }
 
 static int mem_cgroup_populate(struct cgroup_subsys *ss,
                                 struct cgroup *cont)
 {
         int ret;
 
         ret = cgroup_add_files(cont, ss, mem_cgroup_files,
                                 ARRAY_SIZE(mem_cgroup_files));
 
         if (!ret)
                 ret = register_memsw_files(cont, ss);
         return ret;
 }
 
 static void mem_cgroup_move_task(struct cgroup_subsys *ss,
                                 struct cgroup *cont,
                                 struct cgroup *old_cont,
                                 struct task_struct *p)
 {
         mutex_lock(&memcg_tasklist);
         /*
          * FIXME: It's better to move charges of this process from old
          * memcg to new memcg. But it's just on TODO-List now.
          */
         mutex_unlock(&memcg_tasklist);
 }
 
 struct cgroup_subsys mem_cgroup_subsys = {
         .name = "memory",
         .subsys_id = mem_cgroup_subsys_id,
         .create = mem_cgroup_create,
         .pre_destroy = mem_cgroup_pre_destroy,
         .destroy = mem_cgroup_destroy,
         .populate = mem_cgroup_populate,
         .attach = mem_cgroup_move_task,
         .early_init = 0,
         .use_id = 1,
 };
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 
 static int __init disable_swap_account(char *s)
 {
         really_do_swap_account = 0;
         return 1;
 }
 __setup("noswapaccount", disable_swap_account);
 #endif