TOMOYO Linux Cross Reference
Linux/mm/memcontrol.c

   /* 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>
    *
    * Memory thresholds
   * Copyright (C) 2009 Nokia Corporation
   * Author: Kirill A. Shutemov
   *
   * Kernel Memory Controller
   * Copyright (C) 2012 Parallels Inc. and Google Inc.
   * Authors: Glauber Costa and Suleiman Souhlal
   *
   * 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/hugetlb.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/export.h>
  #include <linux/mutex.h>
  #include <linux/rbtree.h>
  #include <linux/slab.h>
  #include <linux/swap.h>
  #include <linux/swapops.h>
  #include <linux/spinlock.h>
  #include <linux/eventfd.h>
  #include <linux/sort.h>
  #include <linux/fs.h>
  #include <linux/seq_file.h>
  #include <linux/vmalloc.h>
  #include <linux/vmpressure.h>
  #include <linux/mm_inline.h>
  #include <linux/page_cgroup.h>
  #include <linux/cpu.h>
  #include <linux/oom.h>
  #include <linux/lockdep.h>
  #include "internal.h"
  #include <net/sock.h>
  #include <net/ip.h>
  #include <net/tcp_memcontrol.h>
  #include "slab.h"
  
  #include <asm/uaccess.h>
  
  #include <trace/events/vmscan.h>
  
  struct cgroup_subsys mem_cgroup_subsys __read_mostly;
  EXPORT_SYMBOL(mem_cgroup_subsys);
  
  #define MEM_CGROUP_RECLAIM_RETRIES      5
  static struct mem_cgroup *root_mem_cgroup __read_mostly;
  
  #ifdef CONFIG_MEMCG_SWAP
  /* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
  int do_swap_account __read_mostly;
  
  /* for remember boot option*/
  #ifdef CONFIG_MEMCG_SWAP_ENABLED
  static int really_do_swap_account __initdata = 1;
  #else
  static int really_do_swap_account __initdata = 0;
  #endif
  
  #else
  #define do_swap_account         0
  #endif
  
  
  static const char * const mem_cgroup_stat_names[] = {
          "cache",
          "rss",
          "rss_huge",
          "mapped_file",
          "writeback",
          "swap",
  };
  
  enum mem_cgroup_events_index {
         MEM_CGROUP_EVENTS_PGPGIN,       /* # of pages paged in */
         MEM_CGROUP_EVENTS_PGPGOUT,      /* # of pages paged out */
         MEM_CGROUP_EVENTS_PGFAULT,      /* # of page-faults */
         MEM_CGROUP_EVENTS_PGMAJFAULT,   /* # of major page-faults */
         MEM_CGROUP_EVENTS_NSTATS,
 };
 
 static const char * const mem_cgroup_events_names[] = {
         "pgpgin",
         "pgpgout",
         "pgfault",
         "pgmajfault",
 };
 
 static const char * const mem_cgroup_lru_names[] = {
         "inactive_anon",
         "active_anon",
         "inactive_file",
         "active_file",
         "unevictable",
 };
 
 /*
  * Per memcg event counter is incremented at every pagein/pageout. With THP,
  * it will be incremated by the number of pages. This counter is used for
  * for trigger some periodic events. This is straightforward and better
  * than using jiffies etc. to handle periodic memcg event.
  */
 enum mem_cgroup_events_target {
         MEM_CGROUP_TARGET_THRESH,
         MEM_CGROUP_TARGET_SOFTLIMIT,
         MEM_CGROUP_TARGET_NUMAINFO,
         MEM_CGROUP_NTARGETS,
 };
 #define THRESHOLDS_EVENTS_TARGET 128
 #define SOFTLIMIT_EVENTS_TARGET 1024
 #define NUMAINFO_EVENTS_TARGET  1024
 
 struct mem_cgroup_stat_cpu {
         long count[MEM_CGROUP_STAT_NSTATS];
         unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
         unsigned long nr_page_events;
         unsigned long targets[MEM_CGROUP_NTARGETS];
 };
 
 struct mem_cgroup_reclaim_iter {
         /*
          * last scanned hierarchy member. Valid only if last_dead_count
          * matches memcg->dead_count of the hierarchy root group.
          */
         struct mem_cgroup *last_visited;
         unsigned long last_dead_count;
 
         /* scan generation, increased every round-trip */
         unsigned int generation;
 };
 
 /*
  * per-zone information in memory controller.
  */
 struct mem_cgroup_per_zone {
         struct lruvec           lruvec;
         unsigned long           lru_size[NR_LRU_LISTS];
 
         struct mem_cgroup_reclaim_iter reclaim_iter[DEF_PRIORITY + 1];
 
         struct rb_node          tree_node;      /* RB tree node */
         unsigned long long      usage_in_excess;/* Set to the value by which */
                                                 /* the soft limit is exceeded*/
         bool                    on_tree;
         struct mem_cgroup       *memcg;         /* Back pointer, we cannot */
                                                 /* use container_of        */
 };
 
 struct mem_cgroup_per_node {
         struct mem_cgroup_per_zone zoneinfo[MAX_NR_ZONES];
 };
 
 /*
  * Cgroups above their limits are maintained in a RB-Tree, independent of
  * their hierarchy representation
  */
 
 struct mem_cgroup_tree_per_zone {
         struct rb_root rb_root;
         spinlock_t lock;
 };
 
 struct mem_cgroup_tree_per_node {
         struct mem_cgroup_tree_per_zone rb_tree_per_zone[MAX_NR_ZONES];
 };
 
 struct mem_cgroup_tree {
         struct mem_cgroup_tree_per_node *rb_tree_per_node[MAX_NUMNODES];
 };
 
 static struct mem_cgroup_tree soft_limit_tree __read_mostly;
 
 struct mem_cgroup_threshold {
         struct eventfd_ctx *eventfd;
         u64 threshold;
 };
 
 /* For threshold */
 struct mem_cgroup_threshold_ary {
         /* An array index points to threshold just below or equal to usage. */
         int current_threshold;
         /* Size of entries[] */
         unsigned int size;
         /* Array of thresholds */
         struct mem_cgroup_threshold entries[0];
 };
 
 struct mem_cgroup_thresholds {
         /* Primary thresholds array */
         struct mem_cgroup_threshold_ary *primary;
         /*
          * Spare threshold array.
          * This is needed to make mem_cgroup_unregister_event() "never fail".
          * It must be able to store at least primary->size - 1 entries.
          */
         struct mem_cgroup_threshold_ary *spare;
 };
 
 /* for OOM */
 struct mem_cgroup_eventfd_list {
         struct list_head list;
         struct eventfd_ctx *eventfd;
 };
 
 static void mem_cgroup_threshold(struct mem_cgroup *memcg);
 static void mem_cgroup_oom_notify(struct mem_cgroup *memcg);
 
 /*
  * 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;
 
         /* vmpressure notifications */
         struct vmpressure vmpressure;
 
         /*
          * the counter to account for mem+swap usage.
          */
         struct res_counter memsw;
 
         /*
          * the counter to account for kernel memory usage.
          */
         struct res_counter kmem;
         /*
          * Should the accounting and control be hierarchical, per subtree?
          */
         bool use_hierarchy;
         unsigned long kmem_account_flags; /* See KMEM_ACCOUNTED_*, below */
 
         bool            oom_lock;
         atomic_t        under_oom;
         atomic_t        oom_wakeups;
 
         int     swappiness;
         /* OOM-Killer disable */
         int             oom_kill_disable;
 
         /* set when res.limit == memsw.limit */
         bool            memsw_is_minimum;
 
         /* protect arrays of thresholds */
         struct mutex thresholds_lock;
 
         /* thresholds for memory usage. RCU-protected */
         struct mem_cgroup_thresholds thresholds;
 
         /* thresholds for mem+swap usage. RCU-protected */
         struct mem_cgroup_thresholds memsw_thresholds;
 
         /* For oom notifier event fd */
         struct list_head oom_notify;
 
         /*
          * Should we move charges of a task when a task is moved into this
          * mem_cgroup ? And what type of charges should we move ?
          */
         unsigned long move_charge_at_immigrate;
         /*
          * set > 0 if pages under this cgroup are moving to other cgroup.
          */
         atomic_t        moving_account;
         /* taken only while moving_account > 0 */
         spinlock_t      move_lock;
         /*
          * percpu counter.
          */
         struct mem_cgroup_stat_cpu __percpu *stat;
         /*
          * used when a cpu is offlined or other synchronizations
          * See mem_cgroup_read_stat().
          */
         struct mem_cgroup_stat_cpu nocpu_base;
         spinlock_t pcp_counter_lock;
 
         atomic_t        dead_count;
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_INET)
         struct cg_proto tcp_mem;
 #endif
 #if defined(CONFIG_MEMCG_KMEM)
         /* analogous to slab_common's slab_caches list. per-memcg */
         struct list_head memcg_slab_caches;
         /* Not a spinlock, we can take a lot of time walking the list */
         struct mutex slab_caches_mutex;
         /* Index in the kmem_cache->memcg_params->memcg_caches array */
         int kmemcg_id;
 #endif
 
         int last_scanned_node;
 #if MAX_NUMNODES > 1
         nodemask_t      scan_nodes;
         atomic_t        numainfo_events;
         atomic_t        numainfo_updating;
 #endif
 
         struct mem_cgroup_per_node *nodeinfo[0];
         /* WARNING: nodeinfo must be the last member here */
 };
 
 static size_t memcg_size(void)
 {
         return sizeof(struct mem_cgroup) +
                 nr_node_ids * sizeof(struct mem_cgroup_per_node *);
 }
 
 /* internal only representation about the status of kmem accounting. */
 enum {
         KMEM_ACCOUNTED_ACTIVE = 0, /* accounted by this cgroup itself */
         KMEM_ACCOUNTED_ACTIVATED, /* static key enabled. */
         KMEM_ACCOUNTED_DEAD, /* dead memcg with pending kmem charges */
 };
 
 /* We account when limit is on, but only after call sites are patched */
 #define KMEM_ACCOUNTED_MASK \
                 ((1 << KMEM_ACCOUNTED_ACTIVE) | (1 << KMEM_ACCOUNTED_ACTIVATED))
 
 #ifdef CONFIG_MEMCG_KMEM
 static inline void memcg_kmem_set_active(struct mem_cgroup *memcg)
 {
         set_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags);
 }
 
 static bool memcg_kmem_is_active(struct mem_cgroup *memcg)
 {
         return test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags);
 }
 
 static void memcg_kmem_set_activated(struct mem_cgroup *memcg)
 {
         set_bit(KMEM_ACCOUNTED_ACTIVATED, &memcg->kmem_account_flags);
 }
 
 static void memcg_kmem_clear_activated(struct mem_cgroup *memcg)
 {
         clear_bit(KMEM_ACCOUNTED_ACTIVATED, &memcg->kmem_account_flags);
 }
 
 static void memcg_kmem_mark_dead(struct mem_cgroup *memcg)
 {
         /*
          * Our caller must use css_get() first, because memcg_uncharge_kmem()
          * will call css_put() if it sees the memcg is dead.
          */
         smp_wmb();
         if (test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags))
                 set_bit(KMEM_ACCOUNTED_DEAD, &memcg->kmem_account_flags);
 }
 
 static bool memcg_kmem_test_and_clear_dead(struct mem_cgroup *memcg)
 {
         return test_and_clear_bit(KMEM_ACCOUNTED_DEAD,
                                   &memcg->kmem_account_flags);
 }
 #endif
 
 /* Stuffs for move charges at task migration. */
 /*
  * Types of charges to be moved. "move_charge_at_immitgrate" and
  * "immigrate_flags" are treated as a left-shifted bitmap of these types.
  */
 enum move_type {
         MOVE_CHARGE_TYPE_ANON,  /* private anonymous page and swap of it */
         MOVE_CHARGE_TYPE_FILE,  /* file page(including tmpfs) and swap of it */
         NR_MOVE_TYPE,
 };
 
 /* "mc" and its members are protected by cgroup_mutex */
 static struct move_charge_struct {
         spinlock_t        lock; /* for from, to */
         struct mem_cgroup *from;
         struct mem_cgroup *to;
         unsigned long immigrate_flags;
         unsigned long precharge;
         unsigned long moved_charge;
         unsigned long moved_swap;
         struct task_struct *moving_task;        /* a task moving charges */
         wait_queue_head_t waitq;                /* a waitq for other context */
 } mc = {
         .lock = __SPIN_LOCK_UNLOCKED(mc.lock),
         .waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq),
 };
 
 static bool move_anon(void)
 {
         return test_bit(MOVE_CHARGE_TYPE_ANON, &mc.immigrate_flags);
 }
 
 static bool move_file(void)
 {
         return test_bit(MOVE_CHARGE_TYPE_FILE, &mc.immigrate_flags);
 }
 
 /*
  * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
  * limit reclaim to prevent infinite loops, if they ever occur.
  */
 #define MEM_CGROUP_MAX_RECLAIM_LOOPS            100
 #define MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS 2
 
 enum charge_type {
         MEM_CGROUP_CHARGE_TYPE_CACHE = 0,
         MEM_CGROUP_CHARGE_TYPE_ANON,
         MEM_CGROUP_CHARGE_TYPE_SWAPOUT, /* for accounting swapcache */
         MEM_CGROUP_CHARGE_TYPE_DROP,    /* a page was unused swap cache */
         NR_CHARGE_TYPE,
 };
 
 /* for encoding cft->private value on file */
 enum res_type {
         _MEM,
         _MEMSWAP,
         _OOM_TYPE,
         _KMEM,
 };
 
 #define MEMFILE_PRIVATE(x, val) ((x) << 16 | (val))
 #define MEMFILE_TYPE(val)       ((val) >> 16 & 0xffff)
 #define MEMFILE_ATTR(val)       ((val) & 0xffff)
 /* Used for OOM nofiier */
 #define OOM_CONTROL             (0)
 
 /*
  * Reclaim flags for mem_cgroup_hierarchical_reclaim
  */
 #define MEM_CGROUP_RECLAIM_NOSWAP_BIT   0x0
 #define MEM_CGROUP_RECLAIM_NOSWAP       (1 << MEM_CGROUP_RECLAIM_NOSWAP_BIT)
 #define MEM_CGROUP_RECLAIM_SHRINK_BIT   0x1
 #define MEM_CGROUP_RECLAIM_SHRINK       (1 << MEM_CGROUP_RECLAIM_SHRINK_BIT)
 
 /*
  * The memcg_create_mutex will be held whenever a new cgroup is created.
  * As a consequence, any change that needs to protect against new child cgroups
  * appearing has to hold it as well.
  */
 static DEFINE_MUTEX(memcg_create_mutex);
 
 struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s)
 {
         return s ? container_of(s, struct mem_cgroup, css) : NULL;
 }
 
 /* Some nice accessors for the vmpressure. */
 struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg)
 {
         if (!memcg)
                 memcg = root_mem_cgroup;
         return &memcg->vmpressure;
 }
 
 struct cgroup_subsys_state *vmpressure_to_css(struct vmpressure *vmpr)
 {
         return &container_of(vmpr, struct mem_cgroup, vmpressure)->css;
 }
 
 struct vmpressure *css_to_vmpressure(struct cgroup_subsys_state *css)
 {
         return &mem_cgroup_from_css(css)->vmpressure;
 }
 
 static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
 {
         return (memcg == root_mem_cgroup);
 }
 
 /*
  * We restrict the id in the range of [1, 65535], so it can fit into
  * an unsigned short.
  */
 #define MEM_CGROUP_ID_MAX       USHRT_MAX
 
 static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
 {
         /*
          * The ID of the root cgroup is 0, but memcg treat 0 as an
          * invalid ID, so we return (cgroup_id + 1).
          */
         return memcg->css.cgroup->id + 1;
 }
 
 static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
 {
         struct cgroup_subsys_state *css;
 
         css = css_from_id(id - 1, &mem_cgroup_subsys);
         return mem_cgroup_from_css(css);
 }
 
 /* Writing them here to avoid exposing memcg's inner layout */
 #if defined(CONFIG_INET) && defined(CONFIG_MEMCG_KMEM)
 
 void sock_update_memcg(struct sock *sk)
 {
         if (mem_cgroup_sockets_enabled) {
                 struct mem_cgroup *memcg;
                 struct cg_proto *cg_proto;
 
                 BUG_ON(!sk->sk_prot->proto_cgroup);
 
                 /* Socket cloning can throw us here with sk_cgrp already
                  * filled. It won't however, necessarily happen from
                  * process context. So the test for root memcg given
                  * the current task's memcg won't help us in this case.
                  *
                  * Respecting the original socket's memcg is a better
                  * decision in this case.
                  */
                 if (sk->sk_cgrp) {
                         BUG_ON(mem_cgroup_is_root(sk->sk_cgrp->memcg));
                         css_get(&sk->sk_cgrp->memcg->css);
                         return;
                 }
 
                 rcu_read_lock();
                 memcg = mem_cgroup_from_task(current);
                 cg_proto = sk->sk_prot->proto_cgroup(memcg);
                 if (!mem_cgroup_is_root(memcg) &&
                     memcg_proto_active(cg_proto) && css_tryget(&memcg->css)) {
                         sk->sk_cgrp = cg_proto;
                 }
                 rcu_read_unlock();
         }
 }
 EXPORT_SYMBOL(sock_update_memcg);
 
 void sock_release_memcg(struct sock *sk)
 {
         if (mem_cgroup_sockets_enabled && sk->sk_cgrp) {
                 struct mem_cgroup *memcg;
                 WARN_ON(!sk->sk_cgrp->memcg);
                 memcg = sk->sk_cgrp->memcg;
                 css_put(&sk->sk_cgrp->memcg->css);
         }
 }
 
 struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)
 {
         if (!memcg || mem_cgroup_is_root(memcg))
                 return NULL;
 
         return &memcg->tcp_mem;
 }
 EXPORT_SYMBOL(tcp_proto_cgroup);
 
 static void disarm_sock_keys(struct mem_cgroup *memcg)
 {
         if (!memcg_proto_activated(&memcg->tcp_mem))
                 return;
         static_key_slow_dec(&memcg_socket_limit_enabled);
 }
 #else
 static void disarm_sock_keys(struct mem_cgroup *memcg)
 {
 }
 #endif
 
 #ifdef CONFIG_MEMCG_KMEM
 /*
  * This will be the memcg's index in each cache's ->memcg_params->memcg_caches.
  * The main reason for not using cgroup id for this:
  *  this works better in sparse environments, where we have a lot of memcgs,
  *  but only a few kmem-limited. Or also, if we have, for instance, 200
  *  memcgs, and none but the 200th is kmem-limited, we'd have to have a
  *  200 entry array for that.
  *
  * The current size of the caches array is stored in
  * memcg_limited_groups_array_size.  It will double each time we have to
  * increase it.
  */
 static DEFINE_IDA(kmem_limited_groups);
 int memcg_limited_groups_array_size;
 
 /*
  * MIN_SIZE is different than 1, because we would like to avoid going through
  * the alloc/free process all the time. In a small machine, 4 kmem-limited
  * cgroups is a reasonable guess. In the future, it could be a parameter or
  * tunable, but that is strictly not necessary.
  *
  * MAX_SIZE should be as large as the number of cgrp_ids. Ideally, we could get
  * this constant directly from cgroup, but it is understandable that this is
  * better kept as an internal representation in cgroup.c. In any case, the
  * cgrp_id space is not getting any smaller, and we don't have to necessarily
  * increase ours as well if it increases.
  */
 #define MEMCG_CACHES_MIN_SIZE 4
 #define MEMCG_CACHES_MAX_SIZE MEM_CGROUP_ID_MAX
 
 /*
  * A lot of the calls to the cache allocation functions are expected to be
  * inlined by the compiler. Since the calls to memcg_kmem_get_cache are
  * conditional to this static branch, we'll have to allow modules that does
  * kmem_cache_alloc and the such to see this symbol as well
  */
 struct static_key memcg_kmem_enabled_key;
 EXPORT_SYMBOL(memcg_kmem_enabled_key);
 
 static void disarm_kmem_keys(struct mem_cgroup *memcg)
 {
         if (memcg_kmem_is_active(memcg)) {
                 static_key_slow_dec(&memcg_kmem_enabled_key);
                 ida_simple_remove(&kmem_limited_groups, memcg->kmemcg_id);
         }
         /*
          * This check can't live in kmem destruction function,
          * since the charges will outlive the cgroup
          */
         WARN_ON(res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0);
 }
 #else
 static void disarm_kmem_keys(struct mem_cgroup *memcg)
 {
 }
 #endif /* CONFIG_MEMCG_KMEM */
 
 static void disarm_static_keys(struct mem_cgroup *memcg)
 {
         disarm_sock_keys(memcg);
         disarm_kmem_keys(memcg);
 }
 
 static void drain_all_stock_async(struct mem_cgroup *memcg);
 
 static struct mem_cgroup_per_zone *
 mem_cgroup_zoneinfo(struct mem_cgroup *memcg, int nid, int zid)
 {
         VM_BUG_ON((unsigned)nid >= nr_node_ids);
         return &memcg->nodeinfo[nid]->zoneinfo[zid];
 }
 
 struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *memcg)
 {
         return &memcg->css;
 }
 
 static struct mem_cgroup_per_zone *
 page_cgroup_zoneinfo(struct mem_cgroup *memcg, struct page *page)
 {
         int nid = page_to_nid(page);
         int zid = page_zonenum(page);
 
         return mem_cgroup_zoneinfo(memcg, nid, zid);
 }
 
 static struct mem_cgroup_tree_per_zone *
 soft_limit_tree_node_zone(int nid, int zid)
 {
         return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
 }
 
 static struct mem_cgroup_tree_per_zone *
 soft_limit_tree_from_page(struct page *page)
 {
         int nid = page_to_nid(page);
         int zid = page_zonenum(page);
 
         return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
 }
 
 static void
 __mem_cgroup_insert_exceeded(struct mem_cgroup *memcg,
                                 struct mem_cgroup_per_zone *mz,
                                 struct mem_cgroup_tree_per_zone *mctz,
                                 unsigned long long new_usage_in_excess)
 {
         struct rb_node **p = &mctz->rb_root.rb_node;
         struct rb_node *parent = NULL;
         struct mem_cgroup_per_zone *mz_node;
 
         if (mz->on_tree)
                 return;
 
         mz->usage_in_excess = new_usage_in_excess;
         if (!mz->usage_in_excess)
                 return;
         while (*p) {
                 parent = *p;
                 mz_node = rb_entry(parent, struct mem_cgroup_per_zone,
                                         tree_node);
                 if (mz->usage_in_excess < mz_node->usage_in_excess)
                         p = &(*p)->rb_left;
                 /*
                  * We can't avoid mem cgroups that are over their soft
                  * limit by the same amount
                  */
                 else if (mz->usage_in_excess >= mz_node->usage_in_excess)
                         p = &(*p)->rb_right;
         }
         rb_link_node(&mz->tree_node, parent, p);
         rb_insert_color(&mz->tree_node, &mctz->rb_root);
         mz->on_tree = true;
 }
 
 static void
 __mem_cgroup_remove_exceeded(struct mem_cgroup *memcg,
                                 struct mem_cgroup_per_zone *mz,
                                 struct mem_cgroup_tree_per_zone *mctz)
 {
         if (!mz->on_tree)
                 return;
         rb_erase(&mz->tree_node, &mctz->rb_root);
         mz->on_tree = false;
 }
 
 static void
 mem_cgroup_remove_exceeded(struct mem_cgroup *memcg,
                                 struct mem_cgroup_per_zone *mz,
                                 struct mem_cgroup_tree_per_zone *mctz)
 {
         spin_lock(&mctz->lock);
         __mem_cgroup_remove_exceeded(memcg, mz, mctz);
         spin_unlock(&mctz->lock);
 }
 
 
 static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
 {
         unsigned long long excess;
         struct mem_cgroup_per_zone *mz;
         struct mem_cgroup_tree_per_zone *mctz;
         int nid = page_to_nid(page);
         int zid = page_zonenum(page);
         mctz = soft_limit_tree_from_page(page);
 
         /*
          * Necessary to update all ancestors when hierarchy is used.
          * because their event counter is not touched.
          */
         for (; memcg; memcg = parent_mem_cgroup(memcg)) {
                 mz = mem_cgroup_zoneinfo(memcg, nid, zid);
                 excess = res_counter_soft_limit_excess(&memcg->res);
                 /*
                  * We have to update the tree if mz is on RB-tree or
                  * mem is over its softlimit.
                  */
                 if (excess || mz->on_tree) {
                         spin_lock(&mctz->lock);
                         /* if on-tree, remove it */
                         if (mz->on_tree)
                                 __mem_cgroup_remove_exceeded(memcg, mz, mctz);
                         /*
                          * Insert again. mz->usage_in_excess will be updated.
                          * If excess is 0, no tree ops.
                          */
                         __mem_cgroup_insert_exceeded(memcg, mz, mctz, excess);
                         spin_unlock(&mctz->lock);
                 }
         }
 }
 
 static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
 {
         int node, zone;
         struct mem_cgroup_per_zone *mz;
         struct mem_cgroup_tree_per_zone *mctz;
 
         for_each_node(node) {
                 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
                         mz = mem_cgroup_zoneinfo(memcg, node, zone);
                         mctz = soft_limit_tree_node_zone(node, zone);
                         mem_cgroup_remove_exceeded(memcg, mz, mctz);
                 }
         }
 }
 
 static struct mem_cgroup_per_zone *
 __mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
 {
         struct rb_node *rightmost = NULL;
         struct mem_cgroup_per_zone *mz;
 
 retry:
         mz = NULL;
         rightmost = rb_last(&mctz->rb_root);
         if (!rightmost)
                 goto done;              /* Nothing to reclaim from */
 
         mz = rb_entry(rightmost, struct mem_cgroup_per_zone, tree_node);
         /*
          * Remove the node now but someone else can add it back,
          * we will to add it back at the end of reclaim to its correct
          * position in the tree.
          */
         __mem_cgroup_remove_exceeded(mz->memcg, mz, mctz);
         if (!res_counter_soft_limit_excess(&mz->memcg->res) ||
                 !css_tryget(&mz->memcg->css))
                 goto retry;
 done:
         return mz;
 }
 
 static struct mem_cgroup_per_zone *
 mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
 {
         struct mem_cgroup_per_zone *mz;
 
         spin_lock(&mctz->lock);
         mz = __mem_cgroup_largest_soft_limit_node(mctz);
         spin_unlock(&mctz->lock);
         return mz;
 }
 
 /*
  * Implementation Note: reading percpu statistics for memcg.
  *
  * Both of vmstat[] and percpu_counter has threshold and do periodic
  * synchronization to implement "quick" read. There are trade-off between
  * reading cost and precision of value. Then, we may have a chance to implement
  * a periodic synchronizion of counter in memcg's counter.
  *
  * But this _read() function is used for user interface now. The user accounts
  * memory usage by memory cgroup and he _always_ requires exact value because
  * he accounts memory. Even if we provide quick-and-fuzzy read, we always
  * have to visit all online cpus and make sum. So, for now, unnecessary
  * synchronization is not implemented. (just implemented for cpu hotplug)
  *
  * If there are kernel internal actions which can make use of some not-exact
  * value, and reading all cpu value can be performance bottleneck in some
  * common workload, threashold and synchonization as vmstat[] should be
  * implemented.
  */
 static long mem_cgroup_read_stat(struct mem_cgroup *memcg,
                                  enum mem_cgroup_stat_index idx)
 {
         long val = 0;
         int cpu;
 
         get_online_cpus();
         for_each_online_cpu(cpu)
                 val += per_cpu(memcg->stat->count[idx], cpu);
 #ifdef CONFIG_HOTPLUG_CPU
         spin_lock(&memcg->pcp_counter_lock);
         val += memcg->nocpu_base.count[idx];
         spin_unlock(&memcg->pcp_counter_lock);
 #endif
         put_online_cpus();
         return val;
 }
 
 static void mem_cgroup_swap_statistics(struct mem_cgroup *memcg,
                                          bool charge)
 {
         int val = (charge) ? 1 : -1;
         this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_SWAP], val);
 }
 
 static unsigned long mem_cgroup_read_events(struct mem_cgroup *memcg,
                                             enum mem_cgroup_events_index idx)
 {
         unsigned long val = 0;
         int cpu;
 
         get_online_cpus();
         for_each_online_cpu(cpu)
                 val += per_cpu(memcg->stat->events[idx], cpu);
 #ifdef CONFIG_HOTPLUG_CPU
         spin_lock(&memcg->pcp_counter_lock);
         val += memcg->nocpu_base.events[idx];
         spin_unlock(&memcg->pcp_counter_lock);
 #endif
         put_online_cpus();
         return val;
 }
 
 static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
                                          struct page *page,
                                          bool anon, int nr_pages)
 {
         preempt_disable();
 
         /*
          * Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
          * counted as CACHE even if it's on ANON LRU.
          */
         if (anon)
                 __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
                                 nr_pages);
         else
                 __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
                                 nr_pages);
 
         if (PageTransHuge(page))
                 __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
                                 nr_pages);
 
         /* pagein of a big page is an event. So, ignore page size */
         if (nr_pages > 0)
                 __this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGIN]);
         else {
                 __this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGOUT]);
                 nr_pages = -nr_pages; /* for event */
         }
 
         __this_cpu_add(memcg->stat->nr_page_events, nr_pages);
 
         preempt_enable();
 }
 
 unsigned long
 mem_cgroup_get_lru_size(struct lruvec *lruvec, enum lru_list lru)
 {
         struct mem_cgroup_per_zone *mz;
 
         mz = container_of(lruvec, struct mem_cgroup_per_zone, lruvec);
         return mz->lru_size[lru];
 }
 
 static unsigned long
 mem_cgroup_zone_nr_lru_pages(struct mem_cgroup *memcg, int nid, int zid,
                         unsigned int lru_mask)
 {
         struct mem_cgroup_per_zone *mz;
         enum lru_list lru;
         unsigned long ret = 0;
 
         mz = mem_cgroup_zoneinfo(memcg, nid, zid);
 
         for_each_lru(lru) {
                 if (BIT(lru) & lru_mask)
                         ret += mz->lru_size[lru];
         }
         return ret;
 }
 
 static unsigned long
 mem_cgroup_node_nr_lru_pages(struct mem_cgroup *memcg,
                         int nid, unsigned int lru_mask)
 {
         u64 total = 0;
         int zid;
 
         for (zid = 0; zid < MAX_NR_ZONES; zid++)
                 total += mem_cgroup_zone_nr_lru_pages(memcg,
                                                 nid, zid, lru_mask);
 
         return total;
 }
 
 static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg,
                         unsigned int lru_mask)
 {
         int nid;
         u64 total = 0;
 
         for_each_node_state(nid, N_MEMORY)
                 total += mem_cgroup_node_nr_lru_pages(memcg, nid, lru_mask);
         return total;
 }
 
 static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
                                        enum mem_cgroup_events_target target)
 {
         unsigned long val, next;
 
         val = __this_cpu_read(memcg->stat->nr_page_events);
         next = __this_cpu_read(memcg->stat->targets[target]);
         /* from time_after() in jiffies.h */
         if ((long)next - (long)val < 0) {
                 switch (target) {
                 case MEM_CGROUP_TARGET_THRESH:
                         next = val + THRESHOLDS_EVENTS_TARGET;
                         break;
                 case MEM_CGROUP_TARGET_SOFTLIMIT:
                         next = val + SOFTLIMIT_EVENTS_TARGET;
                         break;
                 case MEM_CGROUP_TARGET_NUMAINFO:
                         next = val + NUMAINFO_EVENTS_TARGET;
                         break;
                 default:
                         break;
                 }
                 __this_cpu_write(memcg->stat->targets[target], next);
                 return true;
         }
         return false;
 }
 
 /*
  * Check events in order.
  *
  */
 static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
 {
         preempt_disable();
         /* threshold event is triggered in finer grain than soft limit */
         if (unlikely(mem_cgroup_event_ratelimit(memcg,
                                                 MEM_CGROUP_TARGET_THRESH))) {
                 bool do_softlimit;
                 bool do_numainfo __maybe_unused;
 
                 do_softlimit = mem_cgroup_event_ratelimit(memcg,
                                                 MEM_CGROUP_TARGET_SOFTLIMIT);
 #if MAX_NUMNODES > 1
                 do_numainfo = mem_cgroup_event_ratelimit(memcg,
                                                 MEM_CGROUP_TARGET_NUMAINFO);
 #endif
                 preempt_enable();
 
                 mem_cgroup_threshold(memcg);
                 if (unlikely(do_softlimit))
                         mem_cgroup_update_tree(memcg, page);
 #if MAX_NUMNODES > 1
                 if (unlikely(do_numainfo))
                         atomic_inc(&memcg->numainfo_events);
 #endif
         } else
                 preempt_enable();
 }
 
 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 mem_cgroup_from_css(task_css(p, mem_cgroup_subsys_id));
 }
 
 struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
 {
         struct mem_cgroup *memcg = 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 {
                 memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
                 if (unlikely(!memcg))
                         break;
         } while (!css_tryget(&memcg->css));
         rcu_read_unlock();
         return memcg;
 }
 
 /*
  * Returns a next (in a pre-order walk) alive memcg (with elevated css
  * ref. count) or NULL if the whole root's subtree has been visited.
  *
  * helper function to be used by mem_cgroup_iter
  */
 static struct mem_cgroup *__mem_cgroup_iter_next(struct mem_cgroup *root,
                 struct mem_cgroup *last_visited)
 {
         struct cgroup_subsys_state *prev_css, *next_css;
 
         prev_css = last_visited ? &last_visited->css : NULL;
 skip_node:
         next_css = css_next_descendant_pre(prev_css, &root->css);
 
         /*
          * Even if we found a group we have to make sure it is
          * alive. css && !memcg means that the groups should be
          * skipped and we should continue the tree walk.
          * last_visited css is safe to use because it is
          * protected by css_get and the tree walk is rcu safe.
          *
          * We do not take a reference on the root of the tree walk
          * because we might race with the root removal when it would
          * be the only node in the iterated hierarchy and mem_cgroup_iter
          * would end up in an endless loop because it expects that at
          * least one valid node will be returned. Root cannot disappear
          * because caller of the iterator should hold it already so
          * skipping css reference should be safe.
          */
         if (next_css) {
                 if ((next_css == &root->css) ||
                     ((next_css->flags & CSS_ONLINE) && css_tryget(next_css)))
                         return mem_cgroup_from_css(next_css);
 
                 prev_css = next_css;
                 goto skip_node;
         }
 
         return NULL;
 }
 
 static void mem_cgroup_iter_invalidate(struct mem_cgroup *root)
 {
         /*
          * When a group in the hierarchy below root is destroyed, the
          * hierarchy iterator can no longer be trusted since it might
          * have pointed to the destroyed group.  Invalidate it.
          */
         atomic_inc(&root->dead_count);
 }
 
 static struct mem_cgroup *
 mem_cgroup_iter_load(struct mem_cgroup_reclaim_iter *iter,
                      struct mem_cgroup *root,
                      int *sequence)
 {
         struct mem_cgroup *position = NULL;
         /*
          * A cgroup destruction happens in two stages: offlining and
          * release.  They are separated by a RCU grace period.
          *
          * If the iterator is valid, we may still race with an
          * offlining.  The RCU lock ensures the object won't be
          * released, tryget will fail if we lost the race.
          */
         *sequence = atomic_read(&root->dead_count);
         if (iter->last_dead_count == *sequence) {
                 smp_rmb();
                 position = iter->last_visited;
 
                 /*
                  * We cannot take a reference to root because we might race
                  * with root removal and returning NULL would end up in
                  * an endless loop on the iterator user level when root
                  * would be returned all the time.
                  */
                 if (position && position != root &&
                                 !css_tryget(&position->css))
                         position = NULL;
         }
         return position;
 }
 
 static void mem_cgroup_iter_update(struct mem_cgroup_reclaim_iter *iter,
                                    struct mem_cgroup *last_visited,
                                    struct mem_cgroup *new_position,
                                    struct mem_cgroup *root,
                                    int sequence)
 {
         /* root reference counting symmetric to mem_cgroup_iter_load */
         if (last_visited && last_visited != root)
                 css_put(&last_visited->css);
         /*
          * We store the sequence count from the time @last_visited was
          * loaded successfully instead of rereading it here so that we
          * don't lose destruction events in between.  We could have
          * raced with the destruction of @new_position after all.
          */
         iter->last_visited = new_position;
         smp_wmb();
         iter->last_dead_count = sequence;
 }
 
 /**
  * mem_cgroup_iter - iterate over memory cgroup hierarchy
  * @root: hierarchy root
  * @prev: previously returned memcg, NULL on first invocation
  * @reclaim: cookie for shared reclaim walks, NULL for full walks
  *
  * Returns references to children of the hierarchy below @root, or
  * @root itself, or %NULL after a full round-trip.
  *
  * Caller must pass the return value in @prev on subsequent
  * invocations for reference counting, or use mem_cgroup_iter_break()
  * to cancel a hierarchy walk before the round-trip is complete.
  *
  * Reclaimers can specify a zone and a priority level in @reclaim to
  * divide up the memcgs in the hierarchy among all concurrent
  * reclaimers operating on the same zone and priority.
  */
 struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
                                    struct mem_cgroup *prev,
                                    struct mem_cgroup_reclaim_cookie *reclaim)
 {
         struct mem_cgroup *memcg = NULL;
         struct mem_cgroup *last_visited = NULL;
 
         if (mem_cgroup_disabled())
                 return NULL;
 
         if (!root)
                 root = root_mem_cgroup;
 
         if (prev && !reclaim)
                 last_visited = prev;
 
         if (!root->use_hierarchy && root != root_mem_cgroup) {
                 if (prev)
                         goto out_css_put;
                 return root;
         }
 
         rcu_read_lock();
         while (!memcg) {
                 struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
                 int uninitialized_var(seq);
 
                 if (reclaim) {
                         int nid = zone_to_nid(reclaim->zone);
                         int zid = zone_idx(reclaim->zone);
                         struct mem_cgroup_per_zone *mz;
 
                         mz = mem_cgroup_zoneinfo(root, nid, zid);
                         iter = &mz->reclaim_iter[reclaim->priority];
                         if (prev && reclaim->generation != iter->generation) {
                                 iter->last_visited = NULL;
                                 goto out_unlock;
                         }
 
                         last_visited = mem_cgroup_iter_load(iter, root, &seq);
                 }
 
                 memcg = __mem_cgroup_iter_next(root, last_visited);
 
                 if (reclaim) {
                         mem_cgroup_iter_update(iter, last_visited, memcg, root,
                                         seq);
 
                         if (!memcg)
                                 iter->generation++;
                         else if (!prev && memcg)
                                 reclaim->generation = iter->generation;
                 }
 
                 if (prev && !memcg)
                         goto out_unlock;
         }
 out_unlock:
         rcu_read_unlock();
 out_css_put:
         if (prev && prev != root)
                 css_put(&prev->css);
 
         return memcg;
 }
 
 /**
  * mem_cgroup_iter_break - abort a hierarchy walk prematurely
  * @root: hierarchy root
  * @prev: last visited hierarchy member as returned by mem_cgroup_iter()
  */
 void mem_cgroup_iter_break(struct mem_cgroup *root,
                            struct mem_cgroup *prev)
 {
         if (!root)
                 root = root_mem_cgroup;
         if (prev && prev != root)
                 css_put(&prev->css);
 }
 
 /*
  * Iteration constructs for visiting all cgroups (under a tree).  If
  * loops are exited prematurely (break), mem_cgroup_iter_break() must
  * be used for reference counting.
  */
 #define for_each_mem_cgroup_tree(iter, root)            \
         for (iter = mem_cgroup_iter(root, NULL, NULL);  \
              iter != NULL;                              \
              iter = mem_cgroup_iter(root, iter, NULL))
 
 #define for_each_mem_cgroup(iter)                       \
         for (iter = mem_cgroup_iter(NULL, NULL, NULL);  \
              iter != NULL;                              \
              iter = mem_cgroup_iter(NULL, iter, NULL))
 
 void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx)
 {
         struct mem_cgroup *memcg;
 
         rcu_read_lock();
         memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
         if (unlikely(!memcg))
                 goto out;
 
         switch (idx) {
         case PGFAULT:
                 this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGFAULT]);
                 break;
         case PGMAJFAULT:
                 this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGMAJFAULT]);
                 break;
         default:
                 BUG();
         }
 out:
         rcu_read_unlock();
 }
 EXPORT_SYMBOL(__mem_cgroup_count_vm_event);
 
 /**
  * mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg
  * @zone: zone of the wanted lruvec
  * @memcg: memcg of the wanted lruvec
  *
  * Returns the lru list vector holding pages for the given @zone and
  * @mem.  This can be the global zone lruvec, if the memory controller
  * is disabled.
  */
 struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
                                       struct mem_cgroup *memcg)
 {
         struct mem_cgroup_per_zone *mz;
         struct lruvec *lruvec;
 
         if (mem_cgroup_disabled()) {
                 lruvec = &zone->lruvec;
                 goto out;
         }
 
         mz = mem_cgroup_zoneinfo(memcg, zone_to_nid(zone), zone_idx(zone));
         lruvec = &mz->lruvec;
 out:
         /*
          * Since a node can be onlined after the mem_cgroup was created,
          * we have to be prepared to initialize lruvec->zone here;
          * and if offlined then reonlined, we need to reinitialize it.
          */
         if (unlikely(lruvec->zone != zone))
                 lruvec->zone = zone;
         return lruvec;
 }
 
 /*
  * 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.
  */
 
 /**
  * mem_cgroup_page_lruvec - return lruvec for adding an lru page
  * @page: the page
  * @zone: zone of the page
  */
 struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct zone *zone)
 {
         struct mem_cgroup_per_zone *mz;
         struct mem_cgroup *memcg;
         struct page_cgroup *pc;
         struct lruvec *lruvec;
 
         if (mem_cgroup_disabled()) {
                 lruvec = &zone->lruvec;
                 goto out;
         }
 
         pc = lookup_page_cgroup(page);
         memcg = pc->mem_cgroup;
 
         /*
          * Surreptitiously switch any uncharged offlist page to root:
          * an uncharged page off lru does nothing to secure
          * its former mem_cgroup from sudden removal.
          *
          * Our caller holds lru_lock, and PageCgroupUsed is updated
          * under page_cgroup lock: between them, they make all uses
          * of pc->mem_cgroup safe.
          */
         if (!PageLRU(page) && !PageCgroupUsed(pc) && memcg != root_mem_cgroup)
                 pc->mem_cgroup = memcg = root_mem_cgroup;
 
         mz = page_cgroup_zoneinfo(memcg, page);
         lruvec = &mz->lruvec;
 out:
         /*
          * Since a node can be onlined after the mem_cgroup was created,
          * we have to be prepared to initialize lruvec->zone here;
          * and if offlined then reonlined, we need to reinitialize it.
          */
         if (unlikely(lruvec->zone != zone))
                 lruvec->zone = zone;
         return lruvec;
 }
 
 /**
  * mem_cgroup_update_lru_size - account for adding or removing an lru page
  * @lruvec: mem_cgroup per zone lru vector
  * @lru: index of lru list the page is sitting on
  * @nr_pages: positive when adding or negative when removing
  *
  * This function must be called when a page is added to or removed from an
  * lru list.
  */
 void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
                                 int nr_pages)
 {
         struct mem_cgroup_per_zone *mz;
         unsigned long *lru_size;
 
         if (mem_cgroup_disabled())
                 return;
 
         mz = container_of(lruvec, struct mem_cgroup_per_zone, lruvec);
         lru_size = mz->lru_size + lru;
         *lru_size += nr_pages;
         VM_BUG_ON((long)(*lru_size) < 0);
 }
 
 /*
  * Checks whether given mem is same or in the root_mem_cgroup's
  * hierarchy subtree
  */
 bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
                                   struct mem_cgroup *memcg)
 {
         if (root_memcg == memcg)
                 return true;
         if (!root_memcg->use_hierarchy || !memcg)
                 return false;
         return cgroup_is_descendant(memcg->css.cgroup, root_memcg->css.cgroup);
 }
 
 static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
                                        struct mem_cgroup *memcg)
 {
         bool ret;
 
         rcu_read_lock();
         ret = __mem_cgroup_same_or_subtree(root_memcg, memcg);
         rcu_read_unlock();
         return ret;
 }
 
 bool task_in_mem_cgroup(struct task_struct *task,
                         const struct mem_cgroup *memcg)
 {
         struct mem_cgroup *curr = NULL;
         struct task_struct *p;
         bool ret;
 
         p = find_lock_task_mm(task);
         if (p) {
                 curr = try_get_mem_cgroup_from_mm(p->mm);
                 task_unlock(p);
         } else {
                 /*
                  * All threads may have already detached their mm's, but the oom
                  * killer still needs to detect if they have already been oom
                  * killed to prevent needlessly killing additional tasks.
                  */
                 rcu_read_lock();
                 curr = mem_cgroup_from_task(task);
                 if (curr)
                         css_get(&curr->css);
                 rcu_read_unlock();
         }
         if (!curr)
                 return false;
         /*
          * We should check use_hierarchy of "memcg" 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 "memcg" in *cgroup*
          * hierarchy(even if use_hierarchy is disabled in "memcg").
          */
         ret = mem_cgroup_same_or_subtree(memcg, curr);
         css_put(&curr->css);
         return ret;
 }
 
 int mem_cgroup_inactive_anon_is_low(struct lruvec *lruvec)
 {
         unsigned long inactive_ratio;
         unsigned long inactive;
         unsigned long active;
         unsigned long gb;
 
         inactive = mem_cgroup_get_lru_size(lruvec, LRU_INACTIVE_ANON);
         active = mem_cgroup_get_lru_size(lruvec, LRU_ACTIVE_ANON);
 
         gb = (inactive + active) >> (30 - PAGE_SHIFT);
         if (gb)
                 inactive_ratio = int_sqrt(10 * gb);
         else
                 inactive_ratio = 1;
 
         return inactive * inactive_ratio < active;
 }
 
 #define mem_cgroup_from_res_counter(counter, member)    \
         container_of(counter, struct mem_cgroup, member)
 
 /**
  * mem_cgroup_margin - calculate chargeable space of a memory cgroup
  * @memcg: the memory cgroup
  *
  * Returns the maximum amount of memory @mem can be charged with, in
  * pages.
  */
 static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
 {
         unsigned long long margin;
 
         margin = res_counter_margin(&memcg->res);
         if (do_swap_account)
                 margin = min(margin, res_counter_margin(&memcg->memsw));
         return margin >> PAGE_SHIFT;
 }
 
 int mem_cgroup_swappiness(struct mem_cgroup *memcg)
 {
         /* root ? */
         if (!css_parent(&memcg->css))
                 return vm_swappiness;
 
         return memcg->swappiness;
 }
 
 /*
  * memcg->moving_account is used for checking possibility that some thread is
  * calling move_account(). When a thread on CPU-A starts moving pages under
  * a memcg, other threads should check memcg->moving_account under
  * rcu_read_lock(), like this:
  *
  *         CPU-A                                    CPU-B
  *                                              rcu_read_lock()
  *         memcg->moving_account+1              if (memcg->mocing_account)
  *                                                   take heavy locks.
  *         synchronize_rcu()                    update something.
  *                                              rcu_read_unlock()
  *         start move here.
  */
 
 /* for quick checking without looking up memcg */
 atomic_t memcg_moving __read_mostly;
 
 static void mem_cgroup_start_move(struct mem_cgroup *memcg)
 {
         atomic_inc(&memcg_moving);
         atomic_inc(&memcg->moving_account);
         synchronize_rcu();
 }
 
 static void mem_cgroup_end_move(struct mem_cgroup *memcg)
 {
         /*
          * Now, mem_cgroup_clear_mc() may call this function with NULL.
          * We check NULL in callee rather than caller.
          */
         if (memcg) {
                 atomic_dec(&memcg_moving);
                 atomic_dec(&memcg->moving_account);
         }
 }
 
 /*
  * 2 routines for checking "mem" is under move_account() or not.
  *
  * mem_cgroup_stolen() -  checking whether a cgroup is mc.from or not. This
  *                        is used for avoiding races in accounting.  If true,
  *                        pc->mem_cgroup may be overwritten.
  *
  * mem_cgroup_under_move() - checking a cgroup is mc.from or mc.to or
  *                        under hierarchy of moving cgroups. This is for
  *                        waiting at hith-memory prressure caused by "move".
  */
 
 static bool mem_cgroup_stolen(struct mem_cgroup *memcg)
 {
         VM_BUG_ON(!rcu_read_lock_held());
         return atomic_read(&memcg->moving_account) > 0;
 }
 
 static bool mem_cgroup_under_move(struct mem_cgroup *memcg)
 {
         struct mem_cgroup *from;
         struct mem_cgroup *to;
         bool ret = false;
         /*
          * Unlike task_move routines, we access mc.to, mc.from not under
          * mutual exclusion by cgroup_mutex. Here, we take spinlock instead.
          */
         spin_lock(&mc.lock);
         from = mc.from;
         to = mc.to;
         if (!from)
                 goto unlock;
 
         ret = mem_cgroup_same_or_subtree(memcg, from)
                 || mem_cgroup_same_or_subtree(memcg, to);
 unlock:
         spin_unlock(&mc.lock);
         return ret;
 }
 
 static bool mem_cgroup_wait_acct_move(struct mem_cgroup *memcg)
 {
         if (mc.moving_task && current != mc.moving_task) {
                 if (mem_cgroup_under_move(memcg)) {
                         DEFINE_WAIT(wait);
                         prepare_to_wait(&mc.waitq, &wait, TASK_INTERRUPTIBLE);
                         /* moving charge context might have finished. */
                         if (mc.moving_task)
                                 schedule();
                         finish_wait(&mc.waitq, &wait);
                         return true;
                 }
         }
         return false;
 }
 
 /*
  * Take this lock when
  * - a code tries to modify page's memcg while it's USED.
  * - a code tries to modify page state accounting in a memcg.
  * see mem_cgroup_stolen(), too.
  */
 static void move_lock_mem_cgroup(struct mem_cgroup *memcg,
                                   unsigned long *flags)
 {
         spin_lock_irqsave(&memcg->move_lock, *flags);
 }
 
 static void move_unlock_mem_cgroup(struct mem_cgroup *memcg,
                                 unsigned long *flags)
 {
         spin_unlock_irqrestore(&memcg->move_lock, *flags);
 }
 
 #define K(x) ((x) << (PAGE_SHIFT-10))
 /**
  * mem_cgroup_print_oom_info: Print OOM information relevant to memory controller.
  * @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;
         struct mem_cgroup *iter;
         unsigned int i;
 
         if (!p)
                 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();
 
         pr_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
          */
         pr_cont(" as a result of limit of %s\n", memcg_name);
 done:
 
         pr_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));
         pr_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));
         pr_info("kmem: usage %llukB, limit %llukB, failcnt %llu\n",
                 res_counter_read_u64(&memcg->kmem, RES_USAGE) >> 10,
                 res_counter_read_u64(&memcg->kmem, RES_LIMIT) >> 10,
                 res_counter_read_u64(&memcg->kmem, RES_FAILCNT));
 
         for_each_mem_cgroup_tree(iter, memcg) {
                 pr_info("Memory cgroup stats");
 
                 rcu_read_lock();
                 ret = cgroup_path(iter->css.cgroup, memcg_name, PATH_MAX);
                 if (!ret)
                         pr_cont(" for %s", memcg_name);
                 rcu_read_unlock();
                 pr_cont(":");
 
                 for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
                         if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
                                 continue;
                         pr_cont(" %s:%ldKB", mem_cgroup_stat_names[i],
                                 K(mem_cgroup_read_stat(iter, i)));
                 }
 
                 for (i = 0; i < NR_LRU_LISTS; i++)
                         pr_cont(" %s:%luKB", mem_cgroup_lru_names[i],
                                 K(mem_cgroup_nr_lru_pages(iter, BIT(i))));
 
                 pr_cont("\n");
         }
 }
 
 /*
  * 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 *memcg)
 {
         int num = 0;
         struct mem_cgroup *iter;
 
         for_each_mem_cgroup_tree(iter, memcg)
                 num++;
         return num;
 }
 
 /*
  * Return the memory (and swap, if configured) limit for a memcg.
  */
 static u64 mem_cgroup_get_limit(struct mem_cgroup *memcg)
 {
         u64 limit;
 
         limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
 
         /*
          * Do not consider swap space if we cannot swap due to swappiness
          */
         if (mem_cgroup_swappiness(memcg)) {
                 u64 memsw;
 
                 limit += total_swap_pages << PAGE_SHIFT;
                 memsw = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
 
                 /*
                  * If memsw is finite and limits the amount of swap space
                  * available to this memcg, return that limit.
                  */
                 limit = min(limit, memsw);
         }
 
         return limit;
 }
 
 static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
                                      int order)
 {
         struct mem_cgroup *iter;
         unsigned long chosen_points = 0;
         unsigned long totalpages;
         unsigned int points = 0;
         struct task_struct *chosen = NULL;
 
         /*
          * If current has a pending SIGKILL or is exiting, then automatically
          * select it.  The goal is to allow it to allocate so that it may
          * quickly exit and free its memory.
          */
         if (fatal_signal_pending(current) || current->flags & PF_EXITING) {
                 set_thread_flag(TIF_MEMDIE);
                 return;
         }
 
         check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, order, NULL);
         totalpages = mem_cgroup_get_limit(memcg) >> PAGE_SHIFT ? : 1;
         for_each_mem_cgroup_tree(iter, memcg) {
                 struct css_task_iter it;
                 struct task_struct *task;
 
                 css_task_iter_start(&iter->css, &it);
                 while ((task = css_task_iter_next(&it))) {
                         switch (oom_scan_process_thread(task, totalpages, NULL,
                                                         false)) {
                         case OOM_SCAN_SELECT:
                                 if (chosen)
                                         put_task_struct(chosen);
                                 chosen = task;
                                 chosen_points = ULONG_MAX;
                                 get_task_struct(chosen);
                                 /* fall through */
                         case OOM_SCAN_CONTINUE:
                                 continue;
                         case OOM_SCAN_ABORT:
                                 css_task_iter_end(&it);
                                 mem_cgroup_iter_break(memcg, iter);
                                 if (chosen)
                                         put_task_struct(chosen);
                                 return;
                         case OOM_SCAN_OK:
                                 break;
                         };
                         points = oom_badness(task, memcg, NULL, totalpages);
                         if (points > chosen_points) {
                                 if (chosen)
                                         put_task_struct(chosen);
                                 chosen = task;
                                 chosen_points = points;
                                 get_task_struct(chosen);
                         }
                 }
                 css_task_iter_end(&it);
         }
 
         if (!chosen)
                 return;
         points = chosen_points * 1000 / totalpages;
         oom_kill_process(chosen, gfp_mask, order, points, totalpages, memcg,
                          NULL, "Memory cgroup out of memory");
 }
 
 static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
                                         gfp_t gfp_mask,
                                         unsigned long flags)
 {
         unsigned long total = 0;
         bool noswap = false;
         int loop;
 
         if (flags & MEM_CGROUP_RECLAIM_NOSWAP)
                 noswap = true;
         if (!(flags & MEM_CGROUP_RECLAIM_SHRINK) && memcg->memsw_is_minimum)
                 noswap = true;
 
         for (loop = 0; loop < MEM_CGROUP_MAX_RECLAIM_LOOPS; loop++) {
                 if (loop)
                         drain_all_stock_async(memcg);
                 total += try_to_free_mem_cgroup_pages(memcg, gfp_mask, noswap);
                 /*
                  * Allow limit shrinkers, which are triggered directly
                  * by userspace, to catch signals and stop reclaim
                  * after minimal progress, regardless of the margin.
                  */
                 if (total && (flags & MEM_CGROUP_RECLAIM_SHRINK))
                         break;
                 if (mem_cgroup_margin(memcg))
                         break;
                 /*
                  * If nothing was reclaimed after two attempts, there
                  * may be no reclaimable pages in this hierarchy.
                  */
                 if (loop && !total)
                         break;
         }
         return total;
 }
 
 /**
  * test_mem_cgroup_node_reclaimable
  * @memcg: the target memcg
  * @nid: the node ID to be checked.
  * @noswap : specify true here if the user wants flle only information.
  *
  * This function returns whether the specified memcg contains any
  * reclaimable pages on a node. Returns true if there are any reclaimable
  * pages in the node.
  */
 static bool test_mem_cgroup_node_reclaimable(struct mem_cgroup *memcg,
                 int nid, bool noswap)
 {
         if (mem_cgroup_node_nr_lru_pages(memcg, nid, LRU_ALL_FILE))
                 return true;
         if (noswap || !total_swap_pages)
                 return false;
         if (mem_cgroup_node_nr_lru_pages(memcg, nid, LRU_ALL_ANON))
                 return true;
         return false;
 
 }
 #if MAX_NUMNODES > 1
 
 /*
  * Always updating the nodemask is not very good - even if we have an empty
  * list or the wrong list here, we can start from some node and traverse all
  * nodes based on the zonelist. So update the list loosely once per 10 secs.
  *
  */
 static void mem_cgroup_may_update_nodemask(struct mem_cgroup *memcg)
 {
         int nid;
         /*
          * numainfo_events > 0 means there was at least NUMAINFO_EVENTS_TARGET
          * pagein/pageout changes since the last update.
          */
         if (!atomic_read(&memcg->numainfo_events))
                 return;
         if (atomic_inc_return(&memcg->numainfo_updating) > 1)
                 return;
 
         /* make a nodemask where this memcg uses memory from */
         memcg->scan_nodes = node_states[N_MEMORY];
 
         for_each_node_mask(nid, node_states[N_MEMORY]) {
 
                 if (!test_mem_cgroup_node_reclaimable(memcg, nid, false))
                         node_clear(nid, memcg->scan_nodes);
         }
 
         atomic_set(&memcg->numainfo_events, 0);
         atomic_set(&memcg->numainfo_updating, 0);
 }
 
 /*
  * Selecting a node where we start reclaim from. Because what we need is just
  * reducing usage counter, start from anywhere is O,K. Considering
  * memory reclaim from current node, there are pros. and cons.
  *
  * Freeing memory from current node means freeing memory from a node which
  * we'll use or we've used. So, it may make LRU bad. And if several threads
  * hit limits, it will see a contention on a node. But freeing from remote
  * node means more costs for memory reclaim because of memory latency.
  *
  * Now, we use round-robin. Better algorithm is welcomed.
  */
 int mem_cgroup_select_victim_node(struct mem_cgroup *memcg)
 {
         int node;
 
         mem_cgroup_may_update_nodemask(memcg);
         node = memcg->last_scanned_node;
 
         node = next_node(node, memcg->scan_nodes);
         if (node == MAX_NUMNODES)
                 node = first_node(memcg->scan_nodes);
         /*
          * We call this when we hit limit, not when pages are added to LRU.
          * No LRU may hold pages because all pages are UNEVICTABLE or
          * memcg is too small and all pages are not on LRU. In that case,
          * we use curret node.
          */
         if (unlikely(node == MAX_NUMNODES))
                 node = numa_node_id();
 
         memcg->last_scanned_node = node;
         return node;
 }
 
 /*
  * Check all nodes whether it contains reclaimable pages or not.
  * For quick scan, we make use of scan_nodes. This will allow us to skip
  * unused nodes. But scan_nodes is lazily updated and may not cotain
  * enough new information. We need to do double check.
  */
 static bool mem_cgroup_reclaimable(struct mem_cgroup *memcg, bool noswap)
 {
         int nid;
 
         /*
          * quick check...making use of scan_node.
          * We can skip unused nodes.
          */
         if (!nodes_empty(memcg->scan_nodes)) {
                 for (nid = first_node(memcg->scan_nodes);
                      nid < MAX_NUMNODES;
                      nid = next_node(nid, memcg->scan_nodes)) {
 
                         if (test_mem_cgroup_node_reclaimable(memcg, nid, noswap))
                                 return true;
                 }
         }
         /*
          * Check rest of nodes.
          */
         for_each_node_state(nid, N_MEMORY) {
                 if (node_isset(nid, memcg->scan_nodes))
                         continue;
                 if (test_mem_cgroup_node_reclaimable(memcg, nid, noswap))
                         return true;
         }
         return false;
 }
 
 #else
 int mem_cgroup_select_victim_node(struct mem_cgroup *memcg)
 {
         return 0;
 }
 
 static bool mem_cgroup_reclaimable(struct mem_cgroup *memcg, bool noswap)
 {
         return test_mem_cgroup_node_reclaimable(memcg, 0, noswap);
 }
 #endif
 
 static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
                                    struct zone *zone,
                                    gfp_t gfp_mask,
                                    unsigned long *total_scanned)
 {
         struct mem_cgroup *victim = NULL;
         int total = 0;
         int loop = 0;
         unsigned long excess;
         unsigned long nr_scanned;
         struct mem_cgroup_reclaim_cookie reclaim = {
                 .zone = zone,
                 .priority = 0,
         };
 
         excess = res_counter_soft_limit_excess(&root_memcg->res) >> PAGE_SHIFT;
 
         while (1) {
                 victim = mem_cgroup_iter(root_memcg, victim, &reclaim);
                 if (!victim) {
                         loop++;
                         if (loop >= 2) {
                                 /*
                                  * If we have not been able to reclaim
                                  * anything, it might because there are
                                  * no reclaimable pages under this hierarchy
                                  */
                                 if (!total)
                                         break;
                                 /*
                                  * We want to do more targeted reclaim.
                                  * excess >> 2 is not to excessive so as to
                                  * reclaim too much, nor too less that we keep
                                  * coming back to reclaim from this cgroup
                                  */
                                 if (total >= (excess >> 2) ||
                                         (loop > MEM_CGROUP_MAX_RECLAIM_LOOPS))
                                         break;
                         }
                         continue;
                 }
                 if (!mem_cgroup_reclaimable(victim, false))
                         continue;
                 total += mem_cgroup_shrink_node_zone(victim, gfp_mask, false,
                                                      zone, &nr_scanned);
                 *total_scanned += nr_scanned;
                 if (!res_counter_soft_limit_excess(&root_memcg->res))
                         break;
         }
         mem_cgroup_iter_break(root_memcg, victim);
         return total;
 }
 
 #ifdef CONFIG_LOCKDEP
 static struct lockdep_map memcg_oom_lock_dep_map = {
         .name = "memcg_oom_lock",
 };
 #endif
 
 static DEFINE_SPINLOCK(memcg_oom_lock);
 
 /*
  * Check OOM-Killer is already running under our hierarchy.
  * If someone is running, return false.
  */
 static bool mem_cgroup_oom_trylock(struct mem_cgroup *memcg)
 {
         struct mem_cgroup *iter, *failed = NULL;
 
         spin_lock(&memcg_oom_lock);
 
         for_each_mem_cgroup_tree(iter, memcg) {
                 if (iter->oom_lock) {
                         /*
                          * this subtree of our hierarchy is already locked
                          * so we cannot give a lock.
                          */
                         failed = iter;
                         mem_cgroup_iter_break(memcg, iter);
                         break;
                 } else
                         iter->oom_lock = true;
         }
 
         if (failed) {
                 /*
                  * OK, we failed to lock the whole subtree so we have
                  * to clean up what we set up to the failing subtree
                  */
                 for_each_mem_cgroup_tree(iter, memcg) {
                         if (iter == failed) {
                                 mem_cgroup_iter_break(memcg, iter);
                                 break;
                         }
                         iter->oom_lock = false;
                 }
         } else
                 mutex_acquire(&memcg_oom_lock_dep_map, 0, 1, _RET_IP_);
 
         spin_unlock(&memcg_oom_lock);
 
         return !failed;
 }
 
 static void mem_cgroup_oom_unlock(struct mem_cgroup *memcg)
 {
         struct mem_cgroup *iter;
 
         spin_lock(&memcg_oom_lock);
         mutex_release(&memcg_oom_lock_dep_map, 1, _RET_IP_);
         for_each_mem_cgroup_tree(iter, memcg)
                 iter->oom_lock = false;
         spin_unlock(&memcg_oom_lock);
 }
 
 static void mem_cgroup_mark_under_oom(struct mem_cgroup *memcg)
 {
         struct mem_cgroup *iter;
 
         for_each_mem_cgroup_tree(iter, memcg)
                 atomic_inc(&iter->under_oom);
 }
 
 static void mem_cgroup_unmark_under_oom(struct mem_cgroup *memcg)
 {
         struct mem_cgroup *iter;
 
         /*
          * When a new child is created while the hierarchy is under oom,
          * mem_cgroup_oom_lock() may not be called. We have to use
          * atomic_add_unless() here.
          */
         for_each_mem_cgroup_tree(iter, memcg)
                 atomic_add_unless(&iter->under_oom, -1, 0);
 }
 
 static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);
 
 struct oom_wait_info {
         struct mem_cgroup *memcg;
         wait_queue_t    wait;
 };
 
 static int memcg_oom_wake_function(wait_queue_t *wait,
         unsigned mode, int sync, void *arg)
 {
         struct mem_cgroup *wake_memcg = (struct mem_cgroup *)arg;
         struct mem_cgroup *oom_wait_memcg;
         struct oom_wait_info *oom_wait_info;
 
         oom_wait_info = container_of(wait, struct oom_wait_info, wait);
         oom_wait_memcg = oom_wait_info->memcg;
 
         /*
          * Both of oom_wait_info->memcg and wake_memcg are stable under us.
          * Then we can use css_is_ancestor without taking care of RCU.
          */
         if (!mem_cgroup_same_or_subtree(oom_wait_memcg, wake_memcg)
                 && !mem_cgroup_same_or_subtree(wake_memcg, oom_wait_memcg))
                 return 0;
         return autoremove_wake_function(wait, mode, sync, arg);
 }
 
 static void memcg_wakeup_oom(struct mem_cgroup *memcg)
 {
         atomic_inc(&memcg->oom_wakeups);
         /* for filtering, pass "memcg" as argument. */
         __wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, memcg);
 }
 
 static void memcg_oom_recover(struct mem_cgroup *memcg)
 {
         if (memcg && atomic_read(&memcg->under_oom))
                 memcg_wakeup_oom(memcg);
 }
 
 static void mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order)
 {
         if (!current->memcg_oom.may_oom)
                 return;
         /*
          * We are in the middle of the charge context here, so we
          * don't want to block when potentially sitting on a callstack
          * that holds all kinds of filesystem and mm locks.
          *
          * Also, the caller may handle a failed allocation gracefully
          * (like optional page cache readahead) and so an OOM killer
          * invocation might not even be necessary.
          *
          * That's why we don't do anything here except remember the
          * OOM context and then deal with it at the end of the page
          * fault when the stack is unwound, the locks are released,
          * and when we know whether the fault was overall successful.
          */
         css_get(&memcg->css);
         current->memcg_oom.memcg = memcg;
         current->memcg_oom.gfp_mask = mask;
         current->memcg_oom.order = order;
 }
 
 /**
  * mem_cgroup_oom_synchronize - complete memcg OOM handling
  * @handle: actually kill/wait or just clean up the OOM state
  *
  * This has to be called at the end of a page fault if the memcg OOM
  * handler was enabled.
  *
  * Memcg supports userspace OOM handling where failed allocations must
  * sleep on a waitqueue until the userspace task resolves the
  * situation.  Sleeping directly in the charge context with all kinds
  * of locks held is not a good idea, instead we remember an OOM state
  * in the task and mem_cgroup_oom_synchronize() has to be called at
  * the end of the page fault to complete the OOM handling.
  *
  * Returns %true if an ongoing memcg OOM situation was detected and
  * completed, %false otherwise.
  */
 bool mem_cgroup_oom_synchronize(bool handle)
 {
         struct mem_cgroup *memcg = current->memcg_oom.memcg;
         struct oom_wait_info owait;
         bool locked;
 
         /* OOM is global, do not handle */
         if (!memcg)
                 return false;
 
         if (!handle)
                 goto cleanup;
 
         owait.memcg = memcg;
         owait.wait.flags = 0;
         owait.wait.func = memcg_oom_wake_function;
         owait.wait.private = current;
         INIT_LIST_HEAD(&owait.wait.task_list);
 
         prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
         mem_cgroup_mark_under_oom(memcg);
 
         locked = mem_cgroup_oom_trylock(memcg);
 
         if (locked)
                 mem_cgroup_oom_notify(memcg);
 
         if (locked && !memcg->oom_kill_disable) {
                 mem_cgroup_unmark_under_oom(memcg);
                 finish_wait(&memcg_oom_waitq, &owait.wait);
                 mem_cgroup_out_of_memory(memcg, current->memcg_oom.gfp_mask,
                                          current->memcg_oom.order);
         } else {
                 schedule();
                 mem_cgroup_unmark_under_oom(memcg);
                 finish_wait(&memcg_oom_waitq, &owait.wait);
         }
 
         if (locked) {
                 mem_cgroup_oom_unlock(memcg);
                 /*
                  * There is no guarantee that an OOM-lock contender
                  * sees the wakeups triggered by the OOM kill
                  * uncharges.  Wake any sleepers explicitely.
                  */
                 memcg_oom_recover(memcg);
         }
 cleanup:
         current->memcg_oom.memcg = NULL;
         css_put(&memcg->css);
         return true;
 }
 
 /*
  * Currently used to update mapped file statistics, but the routine can be
  * generalized to update other statistics as well.
  *
  * Notes: Race condition
  *
  * We usually use page_cgroup_lock() for accessing page_cgroup member but
  * it tends to be costly. But considering some conditions, we doesn't need
  * to do so _always_.
  *
  * Considering "charge", lock_page_cgroup() is not required because all
  * file-stat operations happen after a page is attached to radix-tree. There
  * are no race with "charge".
  *
  * Considering "uncharge", we know that memcg doesn't clear pc->mem_cgroup
  * at "uncharge" intentionally. So, we always see valid pc->mem_cgroup even
  * if there are race with "uncharge". Statistics itself is properly handled
  * by flags.
  *
  * Considering "move", this is an only case we see a race. To make the race
  * small, we check mm->moving_account and detect there are possibility of race
  * If there is, we take a lock.
  */
 
 void __mem_cgroup_begin_update_page_stat(struct page *page,
                                 bool *locked, unsigned long *flags)
 {
         struct mem_cgroup *memcg;
         struct page_cgroup *pc;
 
         pc = lookup_page_cgroup(page);
 again:
         memcg = pc->mem_cgroup;
         if (unlikely(!memcg || !PageCgroupUsed(pc)))
                 return;
         /*
          * If this memory cgroup is not under account moving, we don't
          * need to take move_lock_mem_cgroup(). Because we already hold
          * rcu_read_lock(), any calls to move_account will be delayed until
          * rcu_read_unlock() if mem_cgroup_stolen() == true.
          */
         if (!mem_cgroup_stolen(memcg))
                 return;
 
         move_lock_mem_cgroup(memcg, flags);
         if (memcg != pc->mem_cgroup || !PageCgroupUsed(pc)) {
                 move_unlock_mem_cgroup(memcg, flags);
                 goto again;
         }
         *locked = true;
 }
 
 void __mem_cgroup_end_update_page_stat(struct page *page, unsigned long *flags)
 {
         struct page_cgroup *pc = lookup_page_cgroup(page);
 
         /*
          * It's guaranteed that pc->mem_cgroup never changes while
          * lock is held because a routine modifies pc->mem_cgroup
          * should take move_lock_mem_cgroup().
          */
         move_unlock_mem_cgroup(pc->mem_cgroup, flags);
 }
 
 void mem_cgroup_update_page_stat(struct page *page,
                                  enum mem_cgroup_stat_index idx, int val)
 {
         struct mem_cgroup *memcg;
         struct page_cgroup *pc = lookup_page_cgroup(page);
         unsigned long uninitialized_var(flags);
 
         if (mem_cgroup_disabled())
                 return;
 
         VM_BUG_ON(!rcu_read_lock_held());
         memcg = pc->mem_cgroup;
         if (unlikely(!memcg || !PageCgroupUsed(pc)))
                 return;
 
         this_cpu_add(memcg->stat->count[idx], val);
 }
 
 /*
  * size of first charge trial. "32" comes from vmscan.c's magic value.
  * TODO: maybe necessary to use big numbers in big irons.
  */
 #define CHARGE_BATCH    32U
 struct memcg_stock_pcp {
         struct mem_cgroup *cached; /* this never be root cgroup */
         unsigned int nr_pages;
         struct work_struct work;
         unsigned long flags;
 #define FLUSHING_CACHED_CHARGE  0
 };
 static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
 static DEFINE_MUTEX(percpu_charge_mutex);
 
 /**
  * consume_stock: Try to consume stocked charge on this cpu.
  * @memcg: memcg to consume from.
  * @nr_pages: how many pages to charge.
  *
  * The charges will only happen if @memcg matches the current cpu's memcg
  * stock, and at least @nr_pages are available in that stock.  Failure to
  * service an allocation will refill the stock.
  *
  * returns true if successful, false otherwise.
  */
 static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
         struct memcg_stock_pcp *stock;
         bool ret = true;
 
         if (nr_pages > CHARGE_BATCH)
                 return false;
 
         stock = &get_cpu_var(memcg_stock);
         if (memcg == stock->cached && stock->nr_pages >= nr_pages)
                 stock->nr_pages -= nr_pages;
         else /* need to call res_counter_charge */
                 ret = false;
         put_cpu_var(memcg_stock);
         return ret;
 }
 
 /*
  * Returns stocks cached in percpu to res_counter and reset cached information.
  */
 static void drain_stock(struct memcg_stock_pcp *stock)
 {
         struct mem_cgroup *old = stock->cached;
 
         if (stock->nr_pages) {
                 unsigned long bytes = stock->nr_pages * PAGE_SIZE;
 
                 res_counter_uncharge(&old->res, bytes);
                 if (do_swap_account)
                         res_counter_uncharge(&old->memsw, bytes);
                 stock->nr_pages = 0;
         }
         stock->cached = NULL;
 }
 
 /*
  * This must be called under preempt disabled or must be called by
  * a thread which is pinned to local cpu.
  */
 static void drain_local_stock(struct work_struct *dummy)
 {
         struct memcg_stock_pcp *stock = &__get_cpu_var(memcg_stock);
         drain_stock(stock);
         clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);
 }
 
 static void __init memcg_stock_init(void)
 {
         int cpu;
 
         for_each_possible_cpu(cpu) {
                 struct memcg_stock_pcp *stock =
                                         &per_cpu(memcg_stock, cpu);
                 INIT_WORK(&stock->work, drain_local_stock);
         }
 }
 
 /*
  * Cache charges(val) which is from res_counter, to local per_cpu area.
  * This will be consumed by consume_stock() function, later.
  */
 static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
         struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock);
 
         if (stock->cached != memcg) { /* reset if necessary */
                 drain_stock(stock);
                 stock->cached = memcg;
         }
         stock->nr_pages += nr_pages;
         put_cpu_var(memcg_stock);
 }
 
 /*
  * Drains all per-CPU charge caches for given root_memcg resp. subtree
  * of the hierarchy under it. sync flag says whether we should block
  * until the work is done.
  */
 static void drain_all_stock(struct mem_cgroup *root_memcg, bool sync)
 {
         int cpu, curcpu;
 
         /* Notify other cpus that system-wide "drain" is running */
         get_online_cpus();
         curcpu = get_cpu();
         for_each_online_cpu(cpu) {
                 struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
                 struct mem_cgroup *memcg;
 
                 memcg = stock->cached;
                 if (!memcg || !stock->nr_pages)
                         continue;
                 if (!mem_cgroup_same_or_subtree(root_memcg, memcg))
                         continue;
                 if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) {
                         if (cpu == curcpu)
                                 drain_local_stock(&stock->work);
                         else
                                 schedule_work_on(cpu, &stock->work);
                 }
         }
         put_cpu();
 
         if (!sync)
                 goto out;
 
         for_each_online_cpu(cpu) {
                 struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
                 if (test_bit(FLUSHING_CACHED_CHARGE, &stock->flags))
                         flush_work(&stock->work);
         }
 out:
         put_online_cpus();
 }
 
 /*
  * Tries to drain stocked charges in other cpus. This function is asynchronous
  * and just put a work per cpu for draining localy on each cpu. Caller can
  * expects some charges will be back to res_counter later but cannot wait for
  * it.
  */
 static void drain_all_stock_async(struct mem_cgroup *root_memcg)
 {
         /*
          * If someone calls draining, avoid adding more kworker runs.
          */
         if (!mutex_trylock(&percpu_charge_mutex))
                 return;
         drain_all_stock(root_memcg, false);
         mutex_unlock(&percpu_charge_mutex);
 }
 
 /* This is a synchronous drain interface. */
 static void drain_all_stock_sync(struct mem_cgroup *root_memcg)
 {
         /* called when force_empty is called */
         mutex_lock(&percpu_charge_mutex);
         drain_all_stock(root_memcg, true);
         mutex_unlock(&percpu_charge_mutex);
 }
 
 /*
  * This function drains percpu counter value from DEAD cpu and
  * move it to local cpu. Note that this function can be preempted.
  */
 static void mem_cgroup_drain_pcp_counter(struct mem_cgroup *memcg, int cpu)
 {
         int i;
 
         spin_lock(&memcg->pcp_counter_lock);
         for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
                 long x = per_cpu(memcg->stat->count[i], cpu);
 
                 per_cpu(memcg->stat->count[i], cpu) = 0;
                 memcg->nocpu_base.count[i] += x;
         }
         for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++) {
                 unsigned long x = per_cpu(memcg->stat->events[i], cpu);
 
                 per_cpu(memcg->stat->events[i], cpu) = 0;
                 memcg->nocpu_base.events[i] += x;
         }
         spin_unlock(&memcg->pcp_counter_lock);
 }
 
 static int memcg_cpu_hotplug_callback(struct notifier_block *nb,
                                         unsigned long action,
                                         void *hcpu)
 {
         int cpu = (unsigned long)hcpu;
         struct memcg_stock_pcp *stock;
         struct mem_cgroup *iter;
 
         if (action == CPU_ONLINE)
                 return NOTIFY_OK;
 
         if (action != CPU_DEAD && action != CPU_DEAD_FROZEN)
                 return NOTIFY_OK;
 
         for_each_mem_cgroup(iter)
                 mem_cgroup_drain_pcp_counter(iter, cpu);
 
         stock = &per_cpu(memcg_stock, cpu);
         drain_stock(stock);
         return NOTIFY_OK;
 }
 
 
 /* See __mem_cgroup_try_charge() for details */
 enum {
         CHARGE_OK,              /* success */
         CHARGE_RETRY,           /* need to retry but retry is not bad */
         CHARGE_NOMEM,           /* we can't do more. return -ENOMEM */
         CHARGE_WOULDBLOCK,      /* GFP_WAIT wasn't set and no enough res. */
 };
 
 static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
                                 unsigned int nr_pages, unsigned int min_pages,
                                 bool invoke_oom)
 {
         unsigned long csize = nr_pages * PAGE_SIZE;
         struct mem_cgroup *mem_over_limit;
         struct res_counter *fail_res;
         unsigned long flags = 0;
         int ret;
 
         ret = res_counter_charge(&memcg->res, csize, &fail_res);
 
         if (likely(!ret)) {
                 if (!do_swap_account)
                         return CHARGE_OK;
                 ret = res_counter_charge(&memcg->memsw, csize, &fail_res);
                 if (likely(!ret))
                         return CHARGE_OK;
 
                 res_counter_uncharge(&memcg->res, csize);
                 mem_over_limit = mem_cgroup_from_res_counter(fail_res, memsw);
                 flags |= MEM_CGROUP_RECLAIM_NOSWAP;
         } else
                 mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
         /*
          * Never reclaim on behalf of optional batching, retry with a
          * single page instead.
          */
         if (nr_pages > min_pages)
                 return CHARGE_RETRY;
 
         if (!(gfp_mask & __GFP_WAIT))
                 return CHARGE_WOULDBLOCK;
 
         if (gfp_mask & __GFP_NORETRY)
                 return CHARGE_NOMEM;
 
         ret = mem_cgroup_reclaim(mem_over_limit, gfp_mask, flags);
         if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
                 return CHARGE_RETRY;
         /*
          * Even though the limit is exceeded at this point, reclaim
          * may have been able to free some pages.  Retry the charge
          * before killing the task.
          *
          * Only for regular pages, though: huge pages are rather
          * unlikely to succeed so close to the limit, and we fall back
          * to regular pages anyway in case of failure.
          */
         if (nr_pages <= (1 << PAGE_ALLOC_COSTLY_ORDER) && ret)
                 return CHARGE_RETRY;
 
         /*
          * At task move, charge accounts can be doubly counted. So, it's
          * better to wait until the end of task_move if something is going on.
          */
         if (mem_cgroup_wait_acct_move(mem_over_limit))
                 return CHARGE_RETRY;
 
         if (invoke_oom)
                 mem_cgroup_oom(mem_over_limit, gfp_mask, get_order(csize));
 
         return CHARGE_NOMEM;
 }
 
 /*
  * __mem_cgroup_try_charge() does
  * 1. detect memcg to be charged against from passed *mm and *ptr,
  * 2. update res_counter
  * 3. call memory reclaim if necessary.
  *
  * In some special case, if the task is fatal, fatal_signal_pending() or
  * has TIF_MEMDIE, this function returns -EINTR while writing root_mem_cgroup
  * to *ptr. There are two reasons for this. 1: fatal threads should quit as soon
  * as possible without any hazards. 2: all pages should have a valid
  * pc->mem_cgroup. If mm is NULL and the caller doesn't pass a valid memcg
  * pointer, that is treated as a charge to root_mem_cgroup.
  *
  * So __mem_cgroup_try_charge() will return
  *  0       ...  on success, filling *ptr with a valid memcg pointer.
  *  -ENOMEM ...  charge failure because of resource limits.
  *  -EINTR  ...  if thread is fatal. *ptr is filled with root_mem_cgroup.
  *
  * Unlike the exported interface, an "oom" parameter is added. if oom==true,
  * the oom-killer can be invoked.
  */
 static int __mem_cgroup_try_charge(struct mm_struct *mm,
                                    gfp_t gfp_mask,
                                    unsigned int nr_pages,
                                    struct mem_cgroup **ptr,
                                    bool oom)
 {
         unsigned int batch = max(CHARGE_BATCH, nr_pages);
         int nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
         struct mem_cgroup *memcg = NULL;
         int ret;
 
         /*
          * Unlike gloval-vm's OOM-kill, we're not in memory shortage
          * in system level. So, allow to go ahead dying process in addition to
          * MEMDIE process.
          */
         if (unlikely(test_thread_flag(TIF_MEMDIE)
                      || fatal_signal_pending(current)))
                 goto bypass;
 
         if (unlikely(task_in_memcg_oom(current)))
                 goto nomem;
 
         if (gfp_mask & __GFP_NOFAIL)
                 oom = false;
 
         /*
          * 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 root memcg (happens for pagecache usage).
          */
         if (!*ptr && !mm)
                 *ptr = root_mem_cgroup;
 again:
         if (*ptr) { /* css should be a valid one */
                 memcg = *ptr;
                 if (mem_cgroup_is_root(memcg))
                         goto done;
                 if (consume_stock(memcg, nr_pages))
                         goto done;
                 css_get(&memcg->css);
         } else {
                 struct task_struct *p;
 
                 rcu_read_lock();
                 p = rcu_dereference(mm->owner);
                 /*
                  * Because we don't have task_lock(), "p" can exit.
                  * In that case, "memcg" can point to root or p can be NULL with
                  * race with swapoff. Then, we have small risk of mis-accouning.
                  * But such kind of mis-account by race always happens because
                  * we don't have cgroup_mutex(). It's overkill and we allo that
                  * small race, here.
                  * (*) swapoff at el will charge against mm-struct not against
                  * task-struct. So, mm->owner can be NULL.
                  */
                 memcg = mem_cgroup_from_task(p);
                 if (!memcg)
                         memcg = root_mem_cgroup;
                 if (mem_cgroup_is_root(memcg)) {
                         rcu_read_unlock();
                         goto done;
                 }
                 if (consume_stock(memcg, nr_pages)) {
                         /*
                          * It seems dagerous to access memcg without css_get().
                          * But considering how consume_stok works, it's not
                          * necessary. If consume_stock success, some charges
                          * from this memcg are cached on this cpu. So, we
                          * don't need to call css_get()/css_tryget() before
                          * calling consume_stock().
                          */
                         rcu_read_unlock();
                         goto done;
                 }
                 /* after here, we may be blocked. we need to get refcnt */
                 if (!css_tryget(&memcg->css)) {
                         rcu_read_unlock();
                         goto again;
                 }
                 rcu_read_unlock();
         }
 
         do {
                 bool invoke_oom = oom && !nr_oom_retries;
 
                 /* If killed, bypass charge */
                 if (fatal_signal_pending(current)) {
                         css_put(&memcg->css);
                         goto bypass;
                 }
 
                 ret = mem_cgroup_do_charge(memcg, gfp_mask, batch,
                                            nr_pages, invoke_oom);
                 switch (ret) {
                 case CHARGE_OK:
                         break;
                 case CHARGE_RETRY: /* not in OOM situation but retry */
                         batch = nr_pages;
                         css_put(&memcg->css);
                         memcg = NULL;
                         goto again;
                 case CHARGE_WOULDBLOCK: /* !__GFP_WAIT */
                         css_put(&memcg->css);
                         goto nomem;
                 case CHARGE_NOMEM: /* OOM routine works */
                         if (!oom || invoke_oom) {
                                 css_put(&memcg->css);
                                 goto nomem;
                         }
                         nr_oom_retries--;
                         break;
                 }
         } while (ret != CHARGE_OK);
 
         if (batch > nr_pages)
                 refill_stock(memcg, batch - nr_pages);
         css_put(&memcg->css);
 done:
         *ptr = memcg;
         return 0;
 nomem:
         if (!(gfp_mask & __GFP_NOFAIL)) {
                 *ptr = NULL;
                 return -ENOMEM;
         }
 bypass:
         *ptr = root_mem_cgroup;
         return -EINTR;
 }
 
 /*
  * Somemtimes we have to undo a charge we got by try_charge().
  * This function is for that and do uncharge, put css's refcnt.
  * gotten by try_charge().
  */
 static void __mem_cgroup_cancel_charge(struct mem_cgroup *memcg,
                                        unsigned int nr_pages)
 {
         if (!mem_cgroup_is_root(memcg)) {
                 unsigned long bytes = nr_pages * PAGE_SIZE;
 
                 res_counter_uncharge(&memcg->res, bytes);
                 if (do_swap_account)
                         res_counter_uncharge(&memcg->memsw, bytes);
         }
 }
 
 /*
  * Cancel chrages in this cgroup....doesn't propagate to parent cgroup.
  * This is useful when moving usage to parent cgroup.
  */
 static void __mem_cgroup_cancel_local_charge(struct mem_cgroup *memcg,
                                         unsigned int nr_pages)
 {
         unsigned long bytes = nr_pages * PAGE_SIZE;
 
         if (mem_cgroup_is_root(memcg))
                 return;
 
         res_counter_uncharge_until(&memcg->res, memcg->res.parent, bytes);
         if (do_swap_account)
                 res_counter_uncharge_until(&memcg->memsw,
                                                 memcg->memsw.parent, bytes);
 }
 
 /*
  * A helper function to get mem_cgroup from ID. must be called under
  * rcu_read_lock().  The caller is responsible for calling css_tryget if
  * the mem_cgroup is used for charging. (dropping refcnt from swap can be
  * called against removed memcg.)
  */
 static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
 {
         /* ID 0 is unused ID */
         if (!id)
                 return NULL;
         return mem_cgroup_from_id(id);
 }
 
 struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
 {
         struct mem_cgroup *memcg = NULL;
         struct page_cgroup *pc;
         unsigned short id;
         swp_entry_t ent;
 
         VM_BUG_ON(!PageLocked(page));
 
         pc = lookup_page_cgroup(page);
         lock_page_cgroup(pc);
         if (PageCgroupUsed(pc)) {
                 memcg = pc->mem_cgroup;
                 if (memcg && !css_tryget(&memcg->css))
                         memcg = NULL;
         } else if (PageSwapCache(page)) {
                 ent.val = page_private(page);
                 id = lookup_swap_cgroup_id(ent);
                 rcu_read_lock();
                 memcg = mem_cgroup_lookup(id);
                 if (memcg && !css_tryget(&memcg->css))
                         memcg = NULL;
                 rcu_read_unlock();
         }
         unlock_page_cgroup(pc);
         return memcg;
 }
 
 static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
                                        struct page *page,
                                        unsigned int nr_pages,
                                        enum charge_type ctype,
                                        bool lrucare)
 {
         struct page_cgroup *pc = lookup_page_cgroup(page);
         struct zone *uninitialized_var(zone);
         struct lruvec *lruvec;
         bool was_on_lru = false;
         bool anon;
 
         lock_page_cgroup(pc);
         VM_BUG_ON(PageCgroupUsed(pc));
         /*
          * we don't need page_cgroup_lock about tail pages, becase they are not
          * accessed by any other context at this point.
          */
 
         /*
          * In some cases, SwapCache and FUSE(splice_buf->radixtree), the page
          * may already be on some other mem_cgroup's LRU.  Take care of it.
          */
         if (lrucare) {
                 zone = page_zone(page);
                 spin_lock_irq(&zone->lru_lock);
                 if (PageLRU(page)) {
                         lruvec = mem_cgroup_zone_lruvec(zone, pc->mem_cgroup);
                         ClearPageLRU(page);
                         del_page_from_lru_list(page, lruvec, page_lru(page));
                         was_on_lru = true;
                 }
         }
 
         pc->mem_cgroup = memcg;
         /*
          * We access a page_cgroup asynchronously without lock_page_cgroup().
          * Especially when a page_cgroup is taken from a page, pc->mem_cgroup
          * is accessed after testing USED bit. To make pc->mem_cgroup visible
          * before USED bit, we need memory barrier here.
          * See mem_cgroup_add_lru_list(), etc.
          */
         smp_wmb();
         SetPageCgroupUsed(pc);
 
         if (lrucare) {
                 if (was_on_lru) {
                         lruvec = mem_cgroup_zone_lruvec(zone, pc->mem_cgroup);
                         VM_BUG_ON(PageLRU(page));
                         SetPageLRU(page);
                         add_page_to_lru_list(page, lruvec, page_lru(page));
                 }
                 spin_unlock_irq(&zone->lru_lock);
         }
 
         if (ctype == MEM_CGROUP_CHARGE_TYPE_ANON)
                 anon = true;
         else
                 anon = false;
 
         mem_cgroup_charge_statistics(memcg, page, anon, nr_pages);
         unlock_page_cgroup(pc);
 
         /*
          * "charge_statistics" updated event counter. Then, check it.
          * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
          * if they exceeds softlimit.
          */
         memcg_check_events(memcg, page);
 }
 
 static DEFINE_MUTEX(set_limit_mutex);
 
 #ifdef CONFIG_MEMCG_KMEM
 static inline bool memcg_can_account_kmem(struct mem_cgroup *memcg)
 {
         return !mem_cgroup_disabled() && !mem_cgroup_is_root(memcg) &&
                 (memcg->kmem_account_flags & KMEM_ACCOUNTED_MASK);
 }
 
 /*
  * This is a bit cumbersome, but it is rarely used and avoids a backpointer
  * in the memcg_cache_params struct.
  */
 static struct kmem_cache *memcg_params_to_cache(struct memcg_cache_params *p)
 {
         struct kmem_cache *cachep;
 
         VM_BUG_ON(p->is_root_cache);
         cachep = p->root_cache;
         return cache_from_memcg_idx(cachep, memcg_cache_id(p->memcg));
 }
 
 #ifdef CONFIG_SLABINFO
 static int mem_cgroup_slabinfo_read(struct cgroup_subsys_state *css,
                                     struct cftype *cft, struct seq_file *m)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct memcg_cache_params *params;
 
         if (!memcg_can_account_kmem(memcg))
                 return -EIO;
 
         print_slabinfo_header(m);
 
         mutex_lock(&memcg->slab_caches_mutex);
         list_for_each_entry(params, &memcg->memcg_slab_caches, list)
                 cache_show(memcg_params_to_cache(params), m);
         mutex_unlock(&memcg->slab_caches_mutex);
 
         return 0;
 }
 #endif
 
 static int memcg_charge_kmem(struct mem_cgroup *memcg, gfp_t gfp, u64 size)
 {
         struct res_counter *fail_res;
         struct mem_cgroup *_memcg;
         int ret = 0;
 
         ret = res_counter_charge(&memcg->kmem, size, &fail_res);
         if (ret)
                 return ret;
 
         _memcg = memcg;
         ret = __mem_cgroup_try_charge(NULL, gfp, size >> PAGE_SHIFT,
                                       &_memcg, oom_gfp_allowed(gfp));
 
         if (ret == -EINTR)  {
                 /*
                  * __mem_cgroup_try_charge() chosed to bypass to root due to
                  * OOM kill or fatal signal.  Since our only options are to
                  * either fail the allocation or charge it to this cgroup, do
                  * it as a temporary condition. But we can't fail. From a
                  * kmem/slab perspective, the cache has already been selected,
                  * by mem_cgroup_kmem_get_cache(), so it is too late to change
                  * our minds.
                  *
                  * This condition will only trigger if the task entered
                  * memcg_charge_kmem in a sane state, but was OOM-killed during
                  * __mem_cgroup_try_charge() above. Tasks that were already
                  * dying when the allocation triggers should have been already
                  * directed to the root cgroup in memcontrol.h
                  */
                 res_counter_charge_nofail(&memcg->res, size, &fail_res);
                 if (do_swap_account)
                         res_counter_charge_nofail(&memcg->memsw, size,
                                                   &fail_res);
                 ret = 0;
         } else if (ret)
                 res_counter_uncharge(&memcg->kmem, size);
 
         return ret;
 }
 
 static void memcg_uncharge_kmem(struct mem_cgroup *memcg, u64 size)
 {
         res_counter_uncharge(&memcg->res, size);
         if (do_swap_account)
                 res_counter_uncharge(&memcg->memsw, size);
 
         /* Not down to 0 */
         if (res_counter_uncharge(&memcg->kmem, size))
                 return;
 
         /*
          * Releases a reference taken in kmem_cgroup_css_offline in case
          * this last uncharge is racing with the offlining code or it is
          * outliving the memcg existence.
          *
          * The memory barrier imposed by test&clear is paired with the
          * explicit one in memcg_kmem_mark_dead().
          */
         if (memcg_kmem_test_and_clear_dead(memcg))
                 css_put(&memcg->css);
 }
 
 void memcg_cache_list_add(struct mem_cgroup *memcg, struct kmem_cache *cachep)
 {
         if (!memcg)
                 return;
 
         mutex_lock(&memcg->slab_caches_mutex);
         list_add(&cachep->memcg_params->list, &memcg->memcg_slab_caches);
         mutex_unlock(&memcg->slab_caches_mutex);
 }
 
 /*
  * helper for acessing a memcg's index. It will be used as an index in the
  * child cache array in kmem_cache, and also to derive its name. This function
  * will return -1 when this is not a kmem-limited memcg.
  */
 int memcg_cache_id(struct mem_cgroup *memcg)
 {
         return memcg ? memcg->kmemcg_id : -1;
 }
 
 /*
  * This ends up being protected by the set_limit mutex, during normal
  * operation, because that is its main call site.
  *
  * But when we create a new cache, we can call this as well if its parent
  * is kmem-limited. That will have to hold set_limit_mutex as well.
  */
 int memcg_update_cache_sizes(struct mem_cgroup *memcg)
 {
         int num, ret;
 
         num = ida_simple_get(&kmem_limited_groups,
                                 0, MEMCG_CACHES_MAX_SIZE, GFP_KERNEL);
         if (num < 0)
                 return num;
         /*
          * After this point, kmem_accounted (that we test atomically in
          * the beginning of this conditional), is no longer 0. This
          * guarantees only one process will set the following boolean
          * to true. We don't need test_and_set because we're protected
          * by the set_limit_mutex anyway.
          */
         memcg_kmem_set_activated(memcg);
 
         ret = memcg_update_all_caches(num+1);
         if (ret) {
                 ida_simple_remove(&kmem_limited_groups, num);
                 memcg_kmem_clear_activated(memcg);
                 return ret;
         }
 
         memcg->kmemcg_id = num;
         INIT_LIST_HEAD(&memcg->memcg_slab_caches);
         mutex_init(&memcg->slab_caches_mutex);
         return 0;
 }
 
 static size_t memcg_caches_array_size(int num_groups)
 {
         ssize_t size;
         if (num_groups <= 0)
                 return 0;
 
         size = 2 * num_groups;
         if (size < MEMCG_CACHES_MIN_SIZE)
                 size = MEMCG_CACHES_MIN_SIZE;
         else if (size > MEMCG_CACHES_MAX_SIZE)
                 size = MEMCG_CACHES_MAX_SIZE;
 
         return size;
 }
 
 /*
  * We should update the current array size iff all caches updates succeed. This
  * can only be done from the slab side. The slab mutex needs to be held when
  * calling this.
  */
 void memcg_update_array_size(int num)
 {
         if (num > memcg_limited_groups_array_size)
                 memcg_limited_groups_array_size = memcg_caches_array_size(num);
 }
 
 static void kmem_cache_destroy_work_func(struct work_struct *w);
 
 int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
 {
         struct memcg_cache_params *cur_params = s->memcg_params;
 
         VM_BUG_ON(!is_root_cache(s));
 
         if (num_groups > memcg_limited_groups_array_size) {
                 int i;
                 ssize_t size = memcg_caches_array_size(num_groups);
 
                 size *= sizeof(void *);
                 size += offsetof(struct memcg_cache_params, memcg_caches);
 
                 s->memcg_params = kzalloc(size, GFP_KERNEL);
                 if (!s->memcg_params) {
                         s->memcg_params = cur_params;
                         return -ENOMEM;
                 }
 
                 s->memcg_params->is_root_cache = true;
 
                 /*
                  * There is the chance it will be bigger than
                  * memcg_limited_groups_array_size, if we failed an allocation
                  * in a cache, in which case all caches updated before it, will
                  * have a bigger array.
                  *
                  * But if that is the case, the data after
                  * memcg_limited_groups_array_size is certainly unused
                  */
                 for (i = 0; i < memcg_limited_groups_array_size; i++) {
                         if (!cur_params->memcg_caches[i])
                                 continue;
                         s->memcg_params->memcg_caches[i] =
                                                 cur_params->memcg_caches[i];
                 }
 
                 /*
                  * Ideally, we would wait until all caches succeed, and only
                  * then free the old one. But this is not worth the extra
                  * pointer per-cache we'd have to have for this.
                  *
                  * It is not a big deal if some caches are left with a size
                  * bigger than the others. And all updates will reset this
                  * anyway.
                  */
                 kfree(cur_params);
         }
         return 0;
 }
 
 int memcg_register_cache(struct mem_cgroup *memcg, struct kmem_cache *s,
                          struct kmem_cache *root_cache)
 {
         size_t size;
 
         if (!memcg_kmem_enabled())
                 return 0;
 
         if (!memcg) {
                 size = offsetof(struct memcg_cache_params, memcg_caches);
                 size += memcg_limited_groups_array_size * sizeof(void *);
         } else
                 size = sizeof(struct memcg_cache_params);
 
         s->memcg_params = kzalloc(size, GFP_KERNEL);
         if (!s->memcg_params)
                 return -ENOMEM;
 
         if (memcg) {
                 s->memcg_params->memcg = memcg;
                 s->memcg_params->root_cache = root_cache;
                 INIT_WORK(&s->memcg_params->destroy,
                                 kmem_cache_destroy_work_func);
         } else
                 s->memcg_params->is_root_cache = true;
 
         return 0;
 }
 
 void memcg_release_cache(struct kmem_cache *s)
 {
         struct kmem_cache *root;
         struct mem_cgroup *memcg;
         int id;
 
         /*
          * This happens, for instance, when a root cache goes away before we
          * add any memcg.
          */
         if (!s->memcg_params)
                 return;
 
         if (s->memcg_params->is_root_cache)
                 goto out;
 
         memcg = s->memcg_params->memcg;
         id  = memcg_cache_id(memcg);
 
         root = s->memcg_params->root_cache;
         root->memcg_params->memcg_caches[id] = NULL;
 
         mutex_lock(&memcg->slab_caches_mutex);
         list_del(&s->memcg_params->list);
         mutex_unlock(&memcg->slab_caches_mutex);
 
         css_put(&memcg->css);
 out:
         kfree(s->memcg_params);
 }
 
 /*
  * During the creation a new cache, we need to disable our accounting mechanism
  * altogether. This is true even if we are not creating, but rather just
  * enqueing new caches to be created.
  *
  * This is because that process will trigger allocations; some visible, like
  * explicit kmallocs to auxiliary data structures, name strings and internal
  * cache structures; some well concealed, like INIT_WORK() that can allocate
  * objects during debug.
  *
  * If any allocation happens during memcg_kmem_get_cache, we will recurse back
  * to it. This may not be a bounded recursion: since the first cache creation
  * failed to complete (waiting on the allocation), we'll just try to create the
  * cache again, failing at the same point.
  *
  * memcg_kmem_get_cache is prepared to abort after seeing a positive count of
  * memcg_kmem_skip_account. So we enclose anything that might allocate memory
  * inside the following two functions.
  */
 static inline void memcg_stop_kmem_account(void)
 {
         VM_BUG_ON(!current->mm);
         current->memcg_kmem_skip_account++;
 }
 
 static inline void memcg_resume_kmem_account(void)
 {
         VM_BUG_ON(!current->mm);
         current->memcg_kmem_skip_account--;
 }
 
 static void kmem_cache_destroy_work_func(struct work_struct *w)
 {
         struct kmem_cache *cachep;
         struct memcg_cache_params *p;
 
         p = container_of(w, struct memcg_cache_params, destroy);
 
         cachep = memcg_params_to_cache(p);
 
         /*
          * If we get down to 0 after shrink, we could delete right away.
          * However, memcg_release_pages() already puts us back in the workqueue
          * in that case. If we proceed deleting, we'll get a dangling
          * reference, and removing the object from the workqueue in that case
          * is unnecessary complication. We are not a fast path.
          *
          * Note that this case is fundamentally different from racing with
          * shrink_slab(): if memcg_cgroup_destroy_cache() is called in
          * kmem_cache_shrink, not only we would be reinserting a dead cache
          * into the queue, but doing so from inside the worker racing to
          * destroy it.
          *
          * So if we aren't down to zero, we'll just schedule a worker and try
          * again
          */
         if (atomic_read(&cachep->memcg_params->nr_pages) != 0) {
                 kmem_cache_shrink(cachep);
                 if (atomic_read(&cachep->memcg_params->nr_pages) == 0)
                         return;
         } else
                 kmem_cache_destroy(cachep);
 }
 
 void mem_cgroup_destroy_cache(struct kmem_cache *cachep)
 {
         if (!cachep->memcg_params->dead)
                 return;
 
         /*
          * There are many ways in which we can get here.
          *
          * We can get to a memory-pressure situation while the delayed work is
          * still pending to run. The vmscan shrinkers can then release all
          * cache memory and get us to destruction. If this is the case, we'll
          * be executed twice, which is a bug (the second time will execute over
          * bogus data). In this case, cancelling the work should be fine.
          *
          * But we can also get here from the worker itself, if
          * kmem_cache_shrink is enough to shake all the remaining objects and
          * get the page count to 0. In this case, we'll deadlock if we try to
          * cancel the work (the worker runs with an internal lock held, which
          * is the same lock we would hold for cancel_work_sync().)
          *
          * Since we can't possibly know who got us here, just refrain from
          * running if there is already work pending
          */
         if (work_pending(&cachep->memcg_params->destroy))
                 return;
         /*
          * We have to defer the actual destroying to a workqueue, because
          * we might currently be in a context that cannot sleep.
          */
         schedule_work(&cachep->memcg_params->destroy);
 }
 
 /*
  * This lock protects updaters, not readers. We want readers to be as fast as
  * they can, and they will either see NULL or a valid cache value. Our model
  * allow them to see NULL, in which case the root memcg will be selected.
  *
  * We need this lock because multiple allocations to the same cache from a non
  * will span more than one worker. Only one of them can create the cache.
  */
 static DEFINE_MUTEX(memcg_cache_mutex);
 
 /*
  * Called with memcg_cache_mutex held
  */
 static struct kmem_cache *kmem_cache_dup(struct mem_cgroup *memcg,
                                          struct kmem_cache *s)
 {
         struct kmem_cache *new;
         static char *tmp_name = NULL;
 
         lockdep_assert_held(&memcg_cache_mutex);
 
         /*
          * kmem_cache_create_memcg duplicates the given name and
          * cgroup_name for this name requires RCU context.
          * This static temporary buffer is used to prevent from
          * pointless shortliving allocation.
          */
         if (!tmp_name) {
                 tmp_name = kmalloc(PATH_MAX, GFP_KERNEL);
                 if (!tmp_name)
                         return NULL;
         }
 
         rcu_read_lock();
         snprintf(tmp_name, PATH_MAX, "%s(%d:%s)", s->name,
                          memcg_cache_id(memcg), cgroup_name(memcg->css.cgroup));
         rcu_read_unlock();
 
         new = kmem_cache_create_memcg(memcg, tmp_name, s->object_size, s->align,
                                       (s->flags & ~SLAB_PANIC), s->ctor, s);
 
         if (new)
                 new->allocflags |= __GFP_KMEMCG;
 
         return new;
 }
 
 static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg,
                                                   struct kmem_cache *cachep)
 {
         struct kmem_cache *new_cachep;
         int idx;
 
         BUG_ON(!memcg_can_account_kmem(memcg));
 
         idx = memcg_cache_id(memcg);
 
         mutex_lock(&memcg_cache_mutex);
         new_cachep = cache_from_memcg_idx(cachep, idx);
         if (new_cachep) {
                 css_put(&memcg->css);
                 goto out;
         }
 
         new_cachep = kmem_cache_dup(memcg, cachep);
         if (new_cachep == NULL) {
                 new_cachep = cachep;
                 css_put(&memcg->css);
                 goto out;
         }
 
         atomic_set(&new_cachep->memcg_params->nr_pages , 0);
 
         cachep->memcg_params->memcg_caches[idx] = new_cachep;
         /*
          * the readers won't lock, make sure everybody sees the updated value,
          * so they won't put stuff in the queue again for no reason
          */
         wmb();
 out:
         mutex_unlock(&memcg_cache_mutex);
         return new_cachep;
 }
 
 void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 {
         struct kmem_cache *c;
         int i;
 
         if (!s->memcg_params)
                 return;
         if (!s->memcg_params->is_root_cache)
                 return;
 
         /*
          * If the cache is being destroyed, we trust that there is no one else
          * requesting objects from it. Even if there are, the sanity checks in
          * kmem_cache_destroy should caught this ill-case.
          *
          * Still, we don't want anyone else freeing memcg_caches under our
          * noses, which can happen if a new memcg comes to life. As usual,
          * we'll take the set_limit_mutex to protect ourselves against this.
          */
         mutex_lock(&set_limit_mutex);
         for_each_memcg_cache_index(i) {
                 c = cache_from_memcg_idx(s, i);
                 if (!c)
                         continue;
 
                 /*
                  * We will now manually delete the caches, so to avoid races
                  * we need to cancel all pending destruction workers and
                  * proceed with destruction ourselves.
                  *
                  * kmem_cache_destroy() will call kmem_cache_shrink internally,
                  * and that could spawn the workers again: it is likely that
                  * the cache still have active pages until this very moment.
                  * This would lead us back to mem_cgroup_destroy_cache.
                  *
                  * But that will not execute at all if the "dead" flag is not
                  * set, so flip it down to guarantee we are in control.
                  */
                 c->memcg_params->dead = false;
                 cancel_work_sync(&c->memcg_params->destroy);
                 kmem_cache_destroy(c);
         }
         mutex_unlock(&set_limit_mutex);
 }
 
 struct create_work {
         struct mem_cgroup *memcg;
         struct kmem_cache *cachep;
         struct work_struct work;
 };
 
 static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
 {
         struct kmem_cache *cachep;
         struct memcg_cache_params *params;
 
         if (!memcg_kmem_is_active(memcg))
                 return;
 
         mutex_lock(&memcg->slab_caches_mutex);
         list_for_each_entry(params, &memcg->memcg_slab_caches, list) {
                 cachep = memcg_params_to_cache(params);
                 cachep->memcg_params->dead = true;
                 schedule_work(&cachep->memcg_params->destroy);
         }
         mutex_unlock(&memcg->slab_caches_mutex);
 }
 
 static void memcg_create_cache_work_func(struct work_struct *w)
 {
         struct create_work *cw;
 
         cw = container_of(w, struct create_work, work);
         memcg_create_kmem_cache(cw->memcg, cw->cachep);
         kfree(cw);
 }
 
 /*
  * Enqueue the creation of a per-memcg kmem_cache.
  */
 static void __memcg_create_cache_enqueue(struct mem_cgroup *memcg,
                                          struct kmem_cache *cachep)
 {
         struct create_work *cw;
 
         cw = kmalloc(sizeof(struct create_work), GFP_NOWAIT);
         if (cw == NULL) {
                 css_put(&memcg->css);
                 return;
         }
 
         cw->memcg = memcg;
         cw->cachep = cachep;
 
         INIT_WORK(&cw->work, memcg_create_cache_work_func);
         schedule_work(&cw->work);
 }
 
 static void memcg_create_cache_enqueue(struct mem_cgroup *memcg,
                                        struct kmem_cache *cachep)
 {
         /*
          * We need to stop accounting when we kmalloc, because if the
          * corresponding kmalloc cache is not yet created, the first allocation
          * in __memcg_create_cache_enqueue will recurse.
          *
          * However, it is better to enclose the whole function. Depending on
          * the debugging options enabled, INIT_WORK(), for instance, can
          * trigger an allocation. This too, will make us recurse. Because at
          * this point we can't allow ourselves back into memcg_kmem_get_cache,
          * the safest choice is to do it like this, wrapping the whole function.
          */
         memcg_stop_kmem_account();
         __memcg_create_cache_enqueue(memcg, cachep);
         memcg_resume_kmem_account();
 }
 /*
  * Return the kmem_cache we're supposed to use for a slab allocation.
  * We try to use the current memcg's version of the cache.
  *
  * If the cache does not exist yet, if we are the first user of it,
  * we either create it immediately, if possible, or create it asynchronously
  * in a workqueue.
  * In the latter case, we will let the current allocation go through with
  * the original cache.
  *
  * Can't be called in interrupt context or from kernel threads.
  * This function needs to be called with rcu_read_lock() held.
  */
 struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
                                           gfp_t gfp)
 {
         struct mem_cgroup *memcg;
         int idx;
 
         VM_BUG_ON(!cachep->memcg_params);
         VM_BUG_ON(!cachep->memcg_params->is_root_cache);
 
         if (!current->mm || current->memcg_kmem_skip_account)
                 return cachep;
 
         rcu_read_lock();
         memcg = mem_cgroup_from_task(rcu_dereference(current->mm->owner));
 
         if (!memcg_can_account_kmem(memcg))
                 goto out;
 
         idx = memcg_cache_id(memcg);
 
         /*
          * barrier to mare sure we're always seeing the up to date value.  The
          * code updating memcg_caches will issue a write barrier to match this.
          */
         read_barrier_depends();
         if (likely(cache_from_memcg_idx(cachep, idx))) {
                 cachep = cache_from_memcg_idx(cachep, idx);
                 goto out;
         }
 
         /* The corresponding put will be done in the workqueue. */
         if (!css_tryget(&memcg->css))
                 goto out;
         rcu_read_unlock();
 
         /*
          * If we are in a safe context (can wait, and not in interrupt
          * context), we could be be predictable and return right away.
          * This would guarantee that the allocation being performed
          * already belongs in the new cache.
          *
          * However, there are some clashes that can arrive from locking.
          * For instance, because we acquire the slab_mutex while doing
          * kmem_cache_dup, this means no further allocation could happen
          * with the slab_mutex held.
          *
          * Also, because cache creation issue get_online_cpus(), this
          * creates a lock chain: memcg_slab_mutex -> cpu_hotplug_mutex,
          * that ends up reversed during cpu hotplug. (cpuset allocates
          * a bunch of GFP_KERNEL memory during cpuup). Due to all that,
          * better to defer everything.
          */
         memcg_create_cache_enqueue(memcg, cachep);
         return cachep;
 out:
         rcu_read_unlock();
         return cachep;
 }
 EXPORT_SYMBOL(__memcg_kmem_get_cache);
 
 /*
  * We need to verify if the allocation against current->mm->owner's memcg is
  * possible for the given order. But the page is not allocated yet, so we'll
  * need a further commit step to do the final arrangements.
  *
  * It is possible for the task to switch cgroups in this mean time, so at
  * commit time, we can't rely on task conversion any longer.  We'll then use
  * the handle argument to return to the caller which cgroup we should commit
  * against. We could also return the memcg directly and avoid the pointer
  * passing, but a boolean return value gives better semantics considering
  * the compiled-out case as well.
  *
  * Returning true means the allocation is possible.
  */
 bool
 __memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **_memcg, int order)
 {
         struct mem_cgroup *memcg;
         int ret;
 
         *_memcg = NULL;
 
         /*
          * Disabling accounting is only relevant for some specific memcg
          * internal allocations. Therefore we would initially not have such
          * check here, since direct calls to the page allocator that are marked
          * with GFP_KMEMCG only happen outside memcg core. We are mostly
          * concerned with cache allocations, and by having this test at
          * memcg_kmem_get_cache, we are already able to relay the allocation to
          * the root cache and bypass the memcg cache altogether.
          *
          * There is one exception, though: the SLUB allocator does not create
          * large order caches, but rather service large kmallocs directly from
          * the page allocator. Therefore, the following sequence when backed by
          * the SLUB allocator:
          *
          *      memcg_stop_kmem_account();
          *      kmalloc(<large_number>)
          *      memcg_resume_kmem_account();
          *
          * would effectively ignore the fact that we should skip accounting,
          * since it will drive us directly to this function without passing
          * through the cache selector memcg_kmem_get_cache. Such large
          * allocations are extremely rare but can happen, for instance, for the
          * cache arrays. We bring this test here.
          */
         if (!current->mm || current->memcg_kmem_skip_account)
                 return true;
 
         memcg = try_get_mem_cgroup_from_mm(current->mm);
 
         /*
          * very rare case described in mem_cgroup_from_task. Unfortunately there
          * isn't much we can do without complicating this too much, and it would
          * be gfp-dependent anyway. Just let it go
          */
         if (unlikely(!memcg))
                 return true;
 
         if (!memcg_can_account_kmem(memcg)) {
                 css_put(&memcg->css);
                 return true;
         }
 
         ret = memcg_charge_kmem(memcg, gfp, PAGE_SIZE << order);
         if (!ret)
                 *_memcg = memcg;
 
         css_put(&memcg->css);
         return (ret == 0);
 }
 
 void __memcg_kmem_commit_charge(struct page *page, struct mem_cgroup *memcg,
                               int order)
 {
         struct page_cgroup *pc;
 
         VM_BUG_ON(mem_cgroup_is_root(memcg));
 
         /* The page allocation failed. Revert */
         if (!page) {
                 memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
                 return;
         }
 
         pc = lookup_page_cgroup(page);
         lock_page_cgroup(pc);
         pc->mem_cgroup = memcg;
         SetPageCgroupUsed(pc);
         unlock_page_cgroup(pc);
 }
 
 void __memcg_kmem_uncharge_pages(struct page *page, int order)
 {
         struct mem_cgroup *memcg = NULL;
         struct page_cgroup *pc;
 
 
         pc = lookup_page_cgroup(page);
         /*
          * Fast unlocked return. Theoretically might have changed, have to
          * check again after locking.
          */
         if (!PageCgroupUsed(pc))
                 return;
 
         lock_page_cgroup(pc);
         if (PageCgroupUsed(pc)) {
                 memcg = pc->mem_cgroup;
                 ClearPageCgroupUsed(pc);
         }
         unlock_page_cgroup(pc);
 
         /*
          * We trust that only if there is a memcg associated with the page, it
          * is a valid allocation
          */
         if (!memcg)
                 return;
 
         VM_BUG_ON(mem_cgroup_is_root(memcg));
         memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
 }
 #else
 static inline void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)
 {
 }
 #endif /* CONFIG_MEMCG_KMEM */
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 
 #define PCGF_NOCOPY_AT_SPLIT (1 << PCG_LOCK | 1 << PCG_MIGRATION)
 /*
  * Because tail pages are not marked as "used", set it. We're under
  * zone->lru_lock, 'splitting on pmd' and compound_lock.
  * charge/uncharge will be never happen and move_account() is done under
  * compound_lock(), so we don't have to take care of races.
  */
 void mem_cgroup_split_huge_fixup(struct page *head)
 {
         struct page_cgroup *head_pc = lookup_page_cgroup(head);
         struct page_cgroup *pc;
         struct mem_cgroup *memcg;
         int i;
 
         if (mem_cgroup_disabled())
                 return;
 
         memcg = head_pc->mem_cgroup;
         for (i = 1; i < HPAGE_PMD_NR; i++) {
                 pc = head_pc + i;
                 pc->mem_cgroup = memcg;
                 smp_wmb();/* see __commit_charge() */
                 pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
         }
         __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
                        HPAGE_PMD_NR);
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 static inline
 void mem_cgroup_move_account_page_stat(struct mem_cgroup *from,
                                         struct mem_cgroup *to,
                                         unsigned int nr_pages,
                                         enum mem_cgroup_stat_index idx)
 {
         /* Update stat data for mem_cgroup */
         preempt_disable();
         __this_cpu_sub(from->stat->count[idx], nr_pages);
         __this_cpu_add(to->stat->count[idx], nr_pages);
         preempt_enable();
 }
 
 /**
  * mem_cgroup_move_account - move account of the page
  * @page: the page
  * @nr_pages: number of regular pages (>1 for huge pages)
  * @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.)
  * - compound_lock is held when nr_pages > 1
  *
  * This function doesn't do "charge" to new cgroup and doesn't do "uncharge"
  * from old cgroup.
  */
 static int mem_cgroup_move_account(struct page *page,
                                    unsigned int nr_pages,
                                    struct page_cgroup *pc,
                                    struct mem_cgroup *from,
                                    struct mem_cgroup *to)
 {
         unsigned long flags;
         int ret;
         bool anon = PageAnon(page);
 
         VM_BUG_ON(from == to);
         VM_BUG_ON(PageLRU(page));
         /*
          * The page is isolated from LRU. So, collapse function
          * will not handle this page. But page splitting can happen.
          * Do this check under compound_page_lock(). The caller should
          * hold it.
          */
         ret = -EBUSY;
         if (nr_pages > 1 && !PageTransHuge(page))
                 goto out;
 
         lock_page_cgroup(pc);
 
         ret = -EINVAL;
         if (!PageCgroupUsed(pc) || pc->mem_cgroup != from)
                 goto unlock;
 
         move_lock_mem_cgroup(from, &flags);
 
         if (!anon && page_mapped(page))
                 mem_cgroup_move_account_page_stat(from, to, nr_pages,
                         MEM_CGROUP_STAT_FILE_MAPPED);
 
         if (PageWriteback(page))
                 mem_cgroup_move_account_page_stat(from, to, nr_pages,
                         MEM_CGROUP_STAT_WRITEBACK);
 
         mem_cgroup_charge_statistics(from, page, anon, -nr_pages);
 
         /* caller should have done css_get */
         pc->mem_cgroup = to;
         mem_cgroup_charge_statistics(to, page, anon, nr_pages);
         move_unlock_mem_cgroup(from, &flags);
         ret = 0;
 unlock:
         unlock_page_cgroup(pc);
         /*
          * check events
          */
         memcg_check_events(to, page);
         memcg_check_events(from, page);
 out:
         return ret;
 }
 
 /**
  * mem_cgroup_move_parent - moves page to the parent group
  * @page: the page to move
  * @pc: page_cgroup of the page
  * @child: page's cgroup
  *
  * move charges to its parent or the root cgroup if the group has no
  * parent (aka use_hierarchy==0).
  * Although this might fail (get_page_unless_zero, isolate_lru_page or
  * mem_cgroup_move_account fails) the failure is always temporary and
  * it signals a race with a page removal/uncharge or migration. In the
  * first case the page is on the way out and it will vanish from the LRU
  * on the next attempt and the call should be retried later.
  * Isolation from the LRU fails only if page has been isolated from
  * the LRU since we looked at it and that usually means either global
  * reclaim or migration going on. The page will either get back to the
  * LRU or vanish.
  * Finaly mem_cgroup_move_account fails only if the page got uncharged
  * (!PageCgroupUsed) or moved to a different group. The page will
  * disappear in the next attempt.
  */
 static int mem_cgroup_move_parent(struct page *page,
                                   struct page_cgroup *pc,
                                   struct mem_cgroup *child)
 {
         struct mem_cgroup *parent;
         unsigned int nr_pages;
         unsigned long uninitialized_var(flags);
         int ret;
 
         VM_BUG_ON(mem_cgroup_is_root(child));
 
         ret = -EBUSY;
         if (!get_page_unless_zero(page))
                 goto out;
         if (isolate_lru_page(page))
                 goto put;
 
         nr_pages = hpage_nr_pages(page);
 
         parent = parent_mem_cgroup(child);
         /*
          * If no parent, move charges to root cgroup.
          */
         if (!parent)
                 parent = root_mem_cgroup;
 
         if (nr_pages > 1) {
                 VM_BUG_ON(!PageTransHuge(page));
                 flags = compound_lock_irqsave(page);
         }
 
         ret = mem_cgroup_move_account(page, nr_pages,
                                 pc, child, parent);
         if (!ret)
                 __mem_cgroup_cancel_local_charge(child, nr_pages);
 
         if (nr_pages > 1)
                 compound_unlock_irqrestore(page, flags);
         putback_lru_page(page);
 put:
         put_page(page);
 out:
         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 = NULL;
         unsigned int nr_pages = 1;
         bool oom = true;
         int ret;
 
         if (PageTransHuge(page)) {
                 nr_pages <<= compound_order(page);
                 VM_BUG_ON(!PageTransHuge(page));
                 /*
                  * Never OOM-kill a process for a huge page.  The
                  * fault handler will fall back to regular pages.
                  */
                 oom = false;
         }
 
         ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &memcg, oom);
         if (ret == -ENOMEM)
                 return ret;
         __mem_cgroup_commit_charge(memcg, page, nr_pages, ctype, false);
         return 0;
 }
 
 int mem_cgroup_newpage_charge(struct page *page,
                               struct mm_struct *mm, gfp_t gfp_mask)
 {
         if (mem_cgroup_disabled())
                 return 0;
         VM_BUG_ON(page_mapped(page));
         VM_BUG_ON(page->mapping && !PageAnon(page));
         VM_BUG_ON(!mm);
         return mem_cgroup_charge_common(page, mm, gfp_mask,
                                         MEM_CGROUP_CHARGE_TYPE_ANON);
 }
 
 /*
  * 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 acquired. This refcnt will be consumed by
  * "commit()" or removed by "cancel()"
  */
 static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm,
                                           struct page *page,
                                           gfp_t mask,
                                           struct mem_cgroup **memcgp)
 {
         struct mem_cgroup *memcg;
         struct page_cgroup *pc;
         int ret;
 
         pc = lookup_page_cgroup(page);
         /*
          * Every swap fault against a single page tries to charge the
          * page, bail as early as possible.  shmem_unuse() encounters
          * already charged pages, too.  The USED bit is protected by
          * the page lock, which serializes swap cache removal, which
          * in turn serializes uncharging.
          */
         if (PageCgroupUsed(pc))
                 return 0;
         if (!do_swap_account)
                 goto charge_cur_mm;
         memcg = try_get_mem_cgroup_from_page(page);
         if (!memcg)
                 goto charge_cur_mm;
         *memcgp = memcg;
         ret = __mem_cgroup_try_charge(NULL, mask, 1, memcgp, true);
         css_put(&memcg->css);
         if (ret == -EINTR)
                 ret = 0;
         return ret;
 charge_cur_mm:
         ret = __mem_cgroup_try_charge(mm, mask, 1, memcgp, true);
         if (ret == -EINTR)
                 ret = 0;
         return ret;
 }
 
 int mem_cgroup_try_charge_swapin(struct mm_struct *mm, struct page *page,
                                  gfp_t gfp_mask, struct mem_cgroup **memcgp)
 {
         *memcgp = NULL;
         if (mem_cgroup_disabled())
                 return 0;
         /*
          * A racing thread's fault, or swapoff, may have already
          * updated the pte, and even removed page from swap cache: in
          * those cases unuse_pte()'s pte_same() test will fail; but
          * there's also a KSM case which does need to charge the page.
          */
         if (!PageSwapCache(page)) {
                 int ret;
 
                 ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, memcgp, true);
                 if (ret == -EINTR)
                         ret = 0;
                 return ret;
         }
         return __mem_cgroup_try_charge_swapin(mm, page, gfp_mask, memcgp);
 }
 
 void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *memcg)
 {
         if (mem_cgroup_disabled())
                 return;
         if (!memcg)
                 return;
         __mem_cgroup_cancel_charge(memcg, 1);
 }
 
 static void
 __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *memcg,
                                         enum charge_type ctype)
 {
         if (mem_cgroup_disabled())
                 return;
         if (!memcg)
                 return;
 
         __mem_cgroup_commit_charge(memcg, page, 1, ctype, true);
         /*
          * 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)};
                 mem_cgroup_uncharge_swap(ent);
         }
 }
 
 void mem_cgroup_commit_charge_swapin(struct page *page,
                                      struct mem_cgroup *memcg)
 {
         __mem_cgroup_commit_charge_swapin(page, memcg,
                                           MEM_CGROUP_CHARGE_TYPE_ANON);
 }
 
 int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
                                 gfp_t gfp_mask)
 {
         struct mem_cgroup *memcg = NULL;
         enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
         int ret;
 
         if (mem_cgroup_disabled())
                 return 0;
         if (PageCompound(page))
                 return 0;
 
         if (!PageSwapCache(page))
                 ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
         else { /* page is swapcache/shmem */
                 ret = __mem_cgroup_try_charge_swapin(mm, page,
                                                      gfp_mask, &memcg);
                 if (!ret)
                         __mem_cgroup_commit_charge_swapin(page, memcg, type);
         }
         return ret;
 }
 
 static void mem_cgroup_do_uncharge(struct mem_cgroup *memcg,
                                    unsigned int nr_pages,
                                    const enum charge_type ctype)
 {
         struct memcg_batch_info *batch = NULL;
         bool uncharge_memsw = true;
 
         /* If swapout, usage of swap doesn't decrease */
         if (!do_swap_account || ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
                 uncharge_memsw = false;
 
         batch = &current->memcg_batch;
         /*
          * In usual, we do css_get() when we remember memcg pointer.
          * But in this case, we keep res->usage until end of a series of
          * uncharges. Then, it's ok to ignore memcg's refcnt.
          */
         if (!batch->memcg)
                 batch->memcg = memcg;
         /*
          * do_batch > 0 when unmapping pages or inode invalidate/truncate.
          * In those cases, all pages freed continuously can be expected to be in
          * the same cgroup and we have chance to coalesce uncharges.
          * But we do uncharge one by one if this is killed by OOM(TIF_MEMDIE)
          * because we want to do uncharge as soon as possible.
          */
 
         if (!batch->do_batch || test_thread_flag(TIF_MEMDIE))
                 goto direct_uncharge;
 
         if (nr_pages > 1)
                 goto direct_uncharge;
 
         /*
          * In typical case, batch->memcg == mem. This means we can
          * merge a series of uncharges to an uncharge of res_counter.
          * If not, we uncharge res_counter ony by one.
          */
         if (batch->memcg != memcg)
                 goto direct_uncharge;
         /* remember freed charge and uncharge it later */
         batch->nr_pages++;
         if (uncharge_memsw)
                 batch->memsw_nr_pages++;
         return;
 direct_uncharge:
         res_counter_uncharge(&memcg->res, nr_pages * PAGE_SIZE);
         if (uncharge_memsw)
                 res_counter_uncharge(&memcg->memsw, nr_pages * PAGE_SIZE);
         if (unlikely(batch->memcg != memcg))
                 memcg_oom_recover(memcg);
 }
 
 /*
  * uncharge if !page_mapped(page)
  */
 static struct mem_cgroup *
 __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype,
                              bool end_migration)
 {
         struct mem_cgroup *memcg = NULL;
         unsigned int nr_pages = 1;
         struct page_cgroup *pc;
         bool anon;
 
         if (mem_cgroup_disabled())
                 return NULL;
 
         if (PageTransHuge(page)) {
                 nr_pages <<= compound_order(page);
                 VM_BUG_ON(!PageTransHuge(page));
         }
         /*
          * Check if our page_cgroup is valid
          */
         pc = lookup_page_cgroup(page);
         if (unlikely(!PageCgroupUsed(pc)))
                 return NULL;
 
         lock_page_cgroup(pc);
 
         memcg = pc->mem_cgroup;
 
         if (!PageCgroupUsed(pc))
                 goto unlock_out;
 
         anon = PageAnon(page);
 
         switch (ctype) {
         case MEM_CGROUP_CHARGE_TYPE_ANON:
                 /*
                  * Generally PageAnon tells if it's the anon statistics to be
                  * updated; but sometimes e.g. mem_cgroup_uncharge_page() is
                  * used before page reached the stage of being marked PageAnon.
                  */
                 anon = true;
                 /* fallthrough */
         case MEM_CGROUP_CHARGE_TYPE_DROP:
                 /* See mem_cgroup_prepare_migration() */
                 if (page_mapped(page))
                         goto unlock_out;
                 /*
                  * Pages under migration may not be uncharged.  But
                  * end_migration() /must/ be the one uncharging the
                  * unused post-migration page and so it has to call
                  * here with the migration bit still set.  See the
                  * res_counter handling below.
                  */
                 if (!end_migration && PageCgroupMigration(pc))
                         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;
         }
 
         mem_cgroup_charge_statistics(memcg, page, anon, -nr_pages);
 
         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.
          */
 
         unlock_page_cgroup(pc);
         /*
          * even after unlock, we have memcg->res.usage here and this memcg
          * will never be freed, so it's safe to call css_get().
          */
         memcg_check_events(memcg, page);
         if (do_swap_account && ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) {
                 mem_cgroup_swap_statistics(memcg, true);
                 css_get(&memcg->css);
         }
         /*
          * Migration does not charge the res_counter for the
          * replacement page, so leave it alone when phasing out the
          * page that is unused after the migration.
          */
         if (!end_migration && !mem_cgroup_is_root(memcg))
                 mem_cgroup_do_uncharge(memcg, nr_pages, ctype);
 
         return memcg;
 
 unlock_out:
         unlock_page_cgroup(pc);
         return NULL;
 }
 
 void mem_cgroup_uncharge_page(struct page *page)
 {
         /* early check. */
         if (page_mapped(page))
                 return;
         VM_BUG_ON(page->mapping && !PageAnon(page));
         /*
          * If the page is in swap cache, uncharge should be deferred
          * to the swap path, which also properly accounts swap usage
          * and handles memcg lifetime.
          *
          * Note that this check is not stable and reclaim may add the
          * page to swap cache at any time after this.  However, if the
          * page is not in swap cache by the time page->mapcount hits
          * 0, there won't be any page table references to the swap
          * slot, and reclaim will free it and not actually write the
          * page to disk.
          */
         if (PageSwapCache(page))
                 return;
         __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_ANON, false);
 }
 
 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, false);
 }
 
 /*
  * Batch_start/batch_end is called in unmap_page_range/invlidate/trucate.
  * In that cases, pages are freed continuously and we can expect pages
  * are in the same memcg. All these calls itself limits the number of
  * pages freed at once, then uncharge_start/end() is called properly.
  * This may be called prural(2) times in a context,
  */
 
 void mem_cgroup_uncharge_start(void)
 {
         current->memcg_batch.do_batch++;
         /* We can do nest. */
         if (current->memcg_batch.do_batch == 1) {
                 current->memcg_batch.memcg = NULL;
                 current->memcg_batch.nr_pages = 0;
                 current->memcg_batch.memsw_nr_pages = 0;
         }
 }
 
 void mem_cgroup_uncharge_end(void)
 {
         struct memcg_batch_info *batch = &current->memcg_batch;
 
         if (!batch->do_batch)
                 return;
 
         batch->do_batch--;
         if (batch->do_batch) /* If stacked, do nothing. */
                 return;
 
         if (!batch->memcg)
                 return;
         /*
          * This "batch->memcg" is valid without any css_get/put etc...
          * bacause we hide charges behind us.
          */
         if (batch->nr_pages)
                 res_counter_uncharge(&batch->memcg->res,
                                      batch->nr_pages * PAGE_SIZE);
         if (batch->memsw_nr_pages)
                 res_counter_uncharge(&batch->memcg->memsw,
                                      batch->memsw_nr_pages * PAGE_SIZE);
         memcg_oom_recover(batch->memcg);
         /* forget this pointer (for sanity check) */
         batch->memcg = NULL;
 }
 
 #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, false);
 
         /*
          * record memcg information,  if swapout && memcg != NULL,
          * css_get() was called in uncharge().
          */
         if (do_swap_account && swapout && memcg)
                 swap_cgroup_record(ent, mem_cgroup_id(memcg));
 }
 #endif
 
 #ifdef CONFIG_MEMCG_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
                  */
                 if (!mem_cgroup_is_root(memcg))
                         res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
                 mem_cgroup_swap_statistics(memcg, false);
                 css_put(&memcg->css);
         }
         rcu_read_unlock();
 }
 
 /**
  * mem_cgroup_move_swap_account - move swap charge and swap_cgroup's record.
  * @entry: swap entry to be moved
  * @from:  mem_cgroup which the entry is moved from
  * @to:  mem_cgroup which the entry is moved to
  *
  * It succeeds only when the swap_cgroup's record for this entry is the same
  * as the mem_cgroup's id of @from.
  *
  * Returns 0 on success, -EINVAL on failure.
  *
  * The caller must have charged to @to, IOW, called res_counter_charge() about
  * both res and memsw, and called css_get().
  */
 static int mem_cgroup_move_swap_account(swp_entry_t entry,
                                 struct mem_cgroup *from, struct mem_cgroup *to)
 {
         unsigned short old_id, new_id;
 
         old_id = mem_cgroup_id(from);
         new_id = mem_cgroup_id(to);
 
         if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
                 mem_cgroup_swap_statistics(from, false);
                 mem_cgroup_swap_statistics(to, true);
                 /*
                  * This function is only called from task migration context now.
                  * It postpones res_counter and refcount handling till the end
                  * of task migration(mem_cgroup_clear_mc()) for performance
                  * improvement. But we cannot postpone css_get(to)  because if
                  * the process that has been moved to @to does swap-in, the
                  * refcount of @to might be decreased to 0.
                  *
                  * We are in attach() phase, so the cgroup is guaranteed to be
                  * alive, so we can just call css_get().
                  */
                 css_get(&to->css);
                 return 0;
         }
         return -EINVAL;
 }
 #else
 static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
                                 struct mem_cgroup *from, struct mem_cgroup *to)
 {
         return -EINVAL;
 }
 #endif
 
 /*
  * Before starting migration, account PAGE_SIZE to mem_cgroup that the old
  * page belongs to.
  */
 void mem_cgroup_prepare_migration(struct page *page, struct page *newpage,
                                   struct mem_cgroup **memcgp)
 {
         struct mem_cgroup *memcg = NULL;
         unsigned int nr_pages = 1;
         struct page_cgroup *pc;
         enum charge_type ctype;
 
         *memcgp = NULL;
 
         if (mem_cgroup_disabled())
                 return;
 
         if (PageTransHuge(page))
                 nr_pages <<= compound_order(page);
 
         pc = lookup_page_cgroup(page);
         lock_page_cgroup(pc);
         if (PageCgroupUsed(pc)) {
                 memcg = pc->mem_cgroup;
                 css_get(&memcg->css);
                 /*
                  * At migrating an anonymous page, its mapcount goes down
                  * to 0 and uncharge() will be called. But, even if it's fully
                  * unmapped, migration may fail and this page has to be
                  * charged again. We set MIGRATION flag here and delay uncharge
                  * until end_migration() is called
                  *
                  * Corner Case Thinking
                  * A)
                  * When the old page was mapped as Anon and it's unmap-and-freed
                  * while migration was ongoing.
                  * If unmap finds the old page, uncharge() of it will be delayed
                  * until end_migration(). If unmap finds a new page, it's
                  * uncharged when it make mapcount to be 1->0. If unmap code
                  * finds swap_migration_entry, the new page will not be mapped
                  * and end_migration() will find it(mapcount==0).
                  *
                  * B)
                  * When the old page was mapped but migraion fails, the kernel
                  * remaps it. A charge for it is kept by MIGRATION flag even
                  * if mapcount goes down to 0. We can do remap successfully
                  * without charging it again.
                  *
                  * C)
                  * The "old" page is under lock_page() until the end of
                  * migration, so, the old page itself will not be swapped-out.
                  * If the new page is swapped out before end_migraton, our
                  * hook to usual swap-out path will catch the event.
                  */
                 if (PageAnon(page))
                         SetPageCgroupMigration(pc);
         }
         unlock_page_cgroup(pc);
         /*
          * If the page is not charged at this point,
          * we return here.
          */
         if (!memcg)
                 return;
 
         *memcgp = memcg;
         /*
          * We charge new page before it's used/mapped. So, even if unlock_page()
          * is called before end_migration, we can catch all events on this new
          * page. In the case new page is migrated but not remapped, new page's
          * mapcount will be finally 0 and we call uncharge in end_migration().
          */
         if (PageAnon(page))
                 ctype = MEM_CGROUP_CHARGE_TYPE_ANON;
         else
                 ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
         /*
          * The page is committed to the memcg, but it's not actually
          * charged to the res_counter since we plan on replacing the
          * old one and only one page is going to be left afterwards.
          */
         __mem_cgroup_commit_charge(memcg, newpage, nr_pages, ctype, false);
 }
 
 /* remove redundant charge if migration failed*/
 void mem_cgroup_end_migration(struct mem_cgroup *memcg,
         struct page *oldpage, struct page *newpage, bool migration_ok)
 {
         struct page *used, *unused;
         struct page_cgroup *pc;
         bool anon;
 
         if (!memcg)
                 return;
 
         if (!migration_ok) {
                 used = oldpage;
                 unused = newpage;
         } else {
                 used = newpage;
                 unused = oldpage;
         }
         anon = PageAnon(used);
         __mem_cgroup_uncharge_common(unused,
                                      anon ? MEM_CGROUP_CHARGE_TYPE_ANON
                                      : MEM_CGROUP_CHARGE_TYPE_CACHE,
                                      true);
         css_put(&memcg->css);
         /*
          * We disallowed uncharge of pages under migration because mapcount
          * of the page goes down to zero, temporarly.
          * Clear the flag and check the page should be charged.
          */
         pc = lookup_page_cgroup(oldpage);
         lock_page_cgroup(pc);
         ClearPageCgroupMigration(pc);
         unlock_page_cgroup(pc);
 
         /*
          * If a page is a file cache, radix-tree replacement is very atomic
          * and we can skip this check. When it was an Anon page, its mapcount
          * goes down to 0. But because we added MIGRATION flage, it's not
          * uncharged yet. There are several case but page->mapcount check
          * and USED bit check in mem_cgroup_uncharge_page() will do enough
          * check. (see prepare_charge() also)
          */
         if (anon)
                 mem_cgroup_uncharge_page(used);
 }
 
 /*
  * At replace page cache, newpage is not under any memcg but it's on
  * LRU. So, this function doesn't touch res_counter but handles LRU
  * in correct way. Both pages are locked so we cannot race with uncharge.
  */
 void mem_cgroup_replace_page_cache(struct page *oldpage,
                                   struct page *newpage)
 {
         struct mem_cgroup *memcg = NULL;
         struct page_cgroup *pc;
         enum charge_type type = MEM_CGROUP_CHARGE_TYPE_CACHE;
 
         if (mem_cgroup_disabled())
                 return;
 
         pc = lookup_page_cgroup(oldpage);
         /* fix accounting on old pages */
         lock_page_cgroup(pc);
         if (PageCgroupUsed(pc)) {
                 memcg = pc->mem_cgroup;
                 mem_cgroup_charge_statistics(memcg, oldpage, false, -1);
                 ClearPageCgroupUsed(pc);
         }
         unlock_page_cgroup(pc);
 
         /*
          * When called from shmem_replace_page(), in some cases the
          * oldpage has already been charged, and in some cases not.
          */
         if (!memcg)
                 return;
         /*
          * Even if newpage->mapping was NULL before starting replacement,
          * the newpage may be on LRU(or pagevec for LRU) already. We lock
          * LRU while we overwrite pc->mem_cgroup.
          */
         __mem_cgroup_commit_charge(memcg, newpage, 1, type, true);
 }
 
 #ifdef CONFIG_DEBUG_VM
 static struct page_cgroup *lookup_page_cgroup_used(struct page *page)
 {
         struct page_cgroup *pc;
 
         pc = lookup_page_cgroup(page);
         /*
          * Can be NULL while feeding pages into the page allocator for
          * the first time, i.e. during boot or memory hotplug;
          * or when mem_cgroup_disabled().
          */
         if (likely(pc) && PageCgroupUsed(pc))
                 return pc;
         return NULL;
 }
 
 bool mem_cgroup_bad_page_check(struct page *page)
 {
         if (mem_cgroup_disabled())
                 return false;
 
         return lookup_page_cgroup_used(page) != NULL;
 }
 
 void mem_cgroup_print_bad_page(struct page *page)
 {
         struct page_cgroup *pc;
 
         pc = lookup_page_cgroup_used(page);
         if (pc) {
                 pr_alert("pc:%p pc->flags:%lx pc->mem_cgroup:%p\n",
                          pc, pc->flags, pc->mem_cgroup);
         }
 }
 #endif
 
 static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
                                 unsigned long long val)
 {
         int retry_count;
         u64 memswlimit, memlimit;
         int ret = 0;
         int children = mem_cgroup_count_children(memcg);
         u64 curusage, oldusage;
         int enlarge;
 
         /*
          * 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);
 
         enlarge = 0;
         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 memcg->res.limit <= memcg->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;
                 }
 
                 memlimit = res_counter_read_u64(&memcg->res, RES_LIMIT);
                 if (memlimit < val)
                         enlarge = 1;
 
                 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;
 
                 mem_cgroup_reclaim(memcg, GFP_KERNEL,
                                    MEM_CGROUP_RECLAIM_SHRINK);
                 curusage = res_counter_read_u64(&memcg->res, RES_USAGE);
                 /* Usage is reduced ? */
                 if (curusage >= oldusage)
                         retry_count--;
                 else
                         oldusage = curusage;
         }
         if (!ret && enlarge)
                 memcg_oom_recover(memcg);
 
         return ret;
 }
 
 static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
                                         unsigned long long val)
 {
         int retry_count;
         u64 memlimit, memswlimit, oldusage, curusage;
         int children = mem_cgroup_count_children(memcg);
         int ret = -EBUSY;
         int enlarge = 0;
 
         /* 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 memcg->res.limit <= memcg->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;
                 }
                 memswlimit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
                 if (memswlimit < val)
                         enlarge = 1;
                 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_reclaim(memcg, GFP_KERNEL,
                                    MEM_CGROUP_RECLAIM_NOSWAP |
                                    MEM_CGROUP_RECLAIM_SHRINK);
                 curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
                 /* Usage is reduced ? */
                 if (curusage >= oldusage)
                         retry_count--;
                 else
                         oldusage = curusage;
         }
         if (!ret && enlarge)
                 memcg_oom_recover(memcg);
         return ret;
 }
 
 unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
                                             gfp_t gfp_mask,
                                             unsigned long *total_scanned)
 {
         unsigned long nr_reclaimed = 0;
         struct mem_cgroup_per_zone *mz, *next_mz = NULL;
         unsigned long reclaimed;
         int loop = 0;
         struct mem_cgroup_tree_per_zone *mctz;
         unsigned long long excess;
         unsigned long nr_scanned;
 
         if (order > 0)
                 return 0;
 
         mctz = soft_limit_tree_node_zone(zone_to_nid(zone), zone_idx(zone));
         /*
          * This loop can run a while, specially if mem_cgroup's continuously
          * keep exceeding their soft limit and putting the system under
          * pressure
          */
         do {
                 if (next_mz)
                         mz = next_mz;
                 else
                         mz = mem_cgroup_largest_soft_limit_node(mctz);
                 if (!mz)
                         break;
 
                 nr_scanned = 0;
                 reclaimed = mem_cgroup_soft_reclaim(mz->memcg, zone,
                                                     gfp_mask, &nr_scanned);
                 nr_reclaimed += reclaimed;
                 *total_scanned += nr_scanned;
                 spin_lock(&mctz->lock);
 
                 /*
                  * If we failed to reclaim anything from this memory cgroup
                  * it is time to move on to the next cgroup
                  */
                 next_mz = NULL;
                 if (!reclaimed) {
                         do {
                                 /*
                                  * Loop until we find yet another one.
                                  *
                                  * By the time we get the soft_limit lock
                                  * again, someone might have aded the
                                  * group back on the RB tree. Iterate to
                                  * make sure we get a different mem.
                                  * mem_cgroup_largest_soft_limit_node returns
                                  * NULL if no other cgroup is present on
                                  * the tree
                                  */
                                 next_mz =
                                 __mem_cgroup_largest_soft_limit_node(mctz);
                                 if (next_mz == mz)
                                         css_put(&next_mz->memcg->css);
                                 else /* next_mz == NULL or other memcg */
                                         break;
                         } while (1);
                 }
                 __mem_cgroup_remove_exceeded(mz->memcg, mz, mctz);
                 excess = res_counter_soft_limit_excess(&mz->memcg->res);
                 /*
                  * One school of thought says that we should not add
                  * back the node to the tree if reclaim returns 0.
                  * But our reclaim could return 0, simply because due
                  * to priority we are exposing a smaller subset of
                  * memory to reclaim from. Consider this as a longer
                  * term TODO.
                  */
                 /* If excess == 0, no tree ops */
                 __mem_cgroup_insert_exceeded(mz->memcg, mz, mctz, excess);
                 spin_unlock(&mctz->lock);
                 css_put(&mz->memcg->css);
                 loop++;
                 /*
                  * Could not reclaim anything and there are no more
                  * mem cgroups to try or we seem to be looping without
                  * reclaiming anything.
                  */
                 if (!nr_reclaimed &&
                         (next_mz == NULL ||
                         loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
                         break;
         } while (!nr_reclaimed);
         if (next_mz)
                 css_put(&next_mz->memcg->css);
         return nr_reclaimed;
 }
 
 /**
  * mem_cgroup_force_empty_list - clears LRU of a group
  * @memcg: group to clear
  * @node: NUMA node
  * @zid: zone id
  * @lru: lru to to clear
  *
  * Traverse a specified page_cgroup list and try to drop them all.  This doesn't
  * reclaim the pages page themselves - pages are moved to the parent (or root)
  * group.
  */
 static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
                                 int node, int zid, enum lru_list lru)
 {
         struct lruvec *lruvec;
         unsigned long flags;
         struct list_head *list;
         struct page *busy;
         struct zone *zone;
 
         zone = &NODE_DATA(node)->node_zones[zid];
         lruvec = mem_cgroup_zone_lruvec(zone, memcg);
         list = &lruvec->lists[lru];
 
         busy = NULL;
         do {
                 struct page_cgroup *pc;
                 struct page *page;
 
                 spin_lock_irqsave(&zone->lru_lock, flags);
                 if (list_empty(list)) {
                         spin_unlock_irqrestore(&zone->lru_lock, flags);
                         break;
                 }
                 page = list_entry(list->prev, struct page, lru);
                 if (busy == page) {
                         list_move(&page->lru, list);
                         busy = NULL;
                         spin_unlock_irqrestore(&zone->lru_lock, flags);
                         continue;
                 }
                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 
                 pc = lookup_page_cgroup(page);
 
                 if (mem_cgroup_move_parent(page, pc, memcg)) {
                         /* found lock contention or "pc" is obsolete. */
                         busy = page;
                         cond_resched();
                 } else
                         busy = NULL;
         } while (!list_empty(list));
 }
 
 /*
  * make mem_cgroup's charge to be 0 if there is no task by moving
  * all the charges and pages to the parent.
  * This enables deleting this mem_cgroup.
  *
  * Caller is responsible for holding css reference on the memcg.
  */
 static void mem_cgroup_reparent_charges(struct mem_cgroup *memcg)
 {
         int node, zid;
         u64 usage;
 
         do {
                 /* This is for making all *used* pages to be on LRU. */
                 lru_add_drain_all();
                 drain_all_stock_sync(memcg);
                 mem_cgroup_start_move(memcg);
                 for_each_node_state(node, N_MEMORY) {
                         for (zid = 0; zid < MAX_NR_ZONES; zid++) {
                                 enum lru_list lru;
                                 for_each_lru(lru) {
                                         mem_cgroup_force_empty_list(memcg,
                                                         node, zid, lru);
                                 }
                         }
                 }
                 mem_cgroup_end_move(memcg);
                 memcg_oom_recover(memcg);
                 cond_resched();
 
                 /*
                  * Kernel memory may not necessarily be trackable to a specific
                  * process. So they are not migrated, and therefore we can't
                  * expect their value to drop to 0 here.
                  * Having res filled up with kmem only is enough.
                  *
                  * This is a safety check because mem_cgroup_force_empty_list
                  * could have raced with mem_cgroup_replace_page_cache callers
                  * so the lru seemed empty but the page could have been added
                  * right after the check. RES_USAGE should be safe as we always
                  * charge before adding to the LRU.
                  */
                 usage = res_counter_read_u64(&memcg->res, RES_USAGE) -
                         res_counter_read_u64(&memcg->kmem, RES_USAGE);
         } while (usage > 0);
 }
 
 static inline bool memcg_has_children(struct mem_cgroup *memcg)
 {
         lockdep_assert_held(&memcg_create_mutex);
         /*
          * The lock does not prevent addition or deletion to the list
          * of children, but it prevents a new child from being
          * initialized based on this parent in css_online(), so it's
          * enough to decide whether hierarchically inherited
          * attributes can still be changed or not.
          */
         return memcg->use_hierarchy &&
                 !list_empty(&memcg->css.cgroup->children);
 }
 
 /*
  * Reclaims as many pages from the given memcg as possible and moves
  * the rest to the parent.
  *
  * Caller is responsible for holding css reference for memcg.
  */
 static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
 {
         int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
         struct cgroup *cgrp = memcg->css.cgroup;
 
         /* returns EBUSY if there is a task or if we come here twice. */
         if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
                 return -EBUSY;
 
         /* we call try-to-free pages for make this cgroup empty */
         lru_add_drain_all();
         /* try to free all pages in this cgroup */
         while (nr_retries && res_counter_read_u64(&memcg->res, RES_USAGE) > 0) {
                 int progress;
 
                 if (signal_pending(current))
                         return -EINTR;
 
                 progress = try_to_free_mem_cgroup_pages(memcg, GFP_KERNEL,
                                                 false);
                 if (!progress) {
                         nr_retries--;
                         /* maybe some writeback is necessary */
                         congestion_wait(BLK_RW_ASYNC, HZ/10);
                 }
 
         }
         lru_add_drain();
         mem_cgroup_reparent_charges(memcg);
 
         return 0;
 }
 
 static int mem_cgroup_force_empty_write(struct cgroup_subsys_state *css,
                                         unsigned int event)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
         if (mem_cgroup_is_root(memcg))
                 return -EINVAL;
         return mem_cgroup_force_empty(memcg);
 }
 
 static u64 mem_cgroup_hierarchy_read(struct cgroup_subsys_state *css,
                                      struct cftype *cft)
 {
         return mem_cgroup_from_css(css)->use_hierarchy;
 }
 
 static int mem_cgroup_hierarchy_write(struct cgroup_subsys_state *css,
                                       struct cftype *cft, u64 val)
 {
         int retval = 0;
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct mem_cgroup *parent_memcg = mem_cgroup_from_css(css_parent(&memcg->css));
 
         mutex_lock(&memcg_create_mutex);
 
         if (memcg->use_hierarchy == val)
                 goto out;
 
         /*
          * If parent's use_hierarchy 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_memcg || !parent_memcg->use_hierarchy) &&
                                 (val == 1 || val == 0)) {
                 if (list_empty(&memcg->css.cgroup->children))
                         memcg->use_hierarchy = val;
                 else
                         retval = -EBUSY;
         } else
                 retval = -EINVAL;
 
 out:
         mutex_unlock(&memcg_create_mutex);
 
         return retval;
 }
 
 
 static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *memcg,
                                                enum mem_cgroup_stat_index idx)
 {
         struct mem_cgroup *iter;
         long val = 0;
 
         /* Per-cpu values can be negative, use a signed accumulator */
         for_each_mem_cgroup_tree(iter, memcg)
                 val += mem_cgroup_read_stat(iter, idx);
 
         if (val < 0) /* race ? */
                 val = 0;
         return val;
 }
 
 static inline u64 mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
 {
         u64 val;
 
         if (!mem_cgroup_is_root(memcg)) {
                 if (!swap)
                         return res_counter_read_u64(&memcg->res, RES_USAGE);
                 else
                         return res_counter_read_u64(&memcg->memsw, RES_USAGE);
         }
 
         /*
          * Transparent hugepages are still accounted for in MEM_CGROUP_STAT_RSS
          * as well as in MEM_CGROUP_STAT_RSS_HUGE.
          */
         val = mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_CACHE);
         val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_RSS);
 
         if (swap)
                 val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_SWAP);
 
         return val << PAGE_SHIFT;
 }
 
 static ssize_t mem_cgroup_read(struct cgroup_subsys_state *css,
                                struct cftype *cft, struct file *file,
                                char __user *buf, size_t nbytes, loff_t *ppos)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         char str[64];
         u64 val;
         int name, len;
         enum res_type type;
 
         type = MEMFILE_TYPE(cft->private);
         name = MEMFILE_ATTR(cft->private);
 
         switch (type) {
         case _MEM:
                 if (name == RES_USAGE)
                         val = mem_cgroup_usage(memcg, false);
                 else
                         val = res_counter_read_u64(&memcg->res, name);
                 break;
         case _MEMSWAP:
                 if (name == RES_USAGE)
                         val = mem_cgroup_usage(memcg, true);
                 else
                         val = res_counter_read_u64(&memcg->memsw, name);
                 break;
         case _KMEM:
                 val = res_counter_read_u64(&memcg->kmem, name);
                 break;
         default:
                 BUG();
         }
 
         len = scnprintf(str, sizeof(str), "%llu\n", (unsigned long long)val);
         return simple_read_from_buffer(buf, nbytes, ppos, str, len);
 }
 
 static int memcg_update_kmem_limit(struct cgroup_subsys_state *css, u64 val)
 {
         int ret = -EINVAL;
 #ifdef CONFIG_MEMCG_KMEM
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         /*
          * For simplicity, we won't allow this to be disabled.  It also can't
          * be changed if the cgroup has children already, or if tasks had
          * already joined.
          *
          * If tasks join before we set the limit, a person looking at
          * kmem.usage_in_bytes will have no way to determine when it took
          * place, which makes the value quite meaningless.
          *
          * After it first became limited, changes in the value of the limit are
          * of course permitted.
          */
         mutex_lock(&memcg_create_mutex);
         mutex_lock(&set_limit_mutex);
         if (!memcg->kmem_account_flags && val != RES_COUNTER_MAX) {
                 if (cgroup_task_count(css->cgroup) || memcg_has_children(memcg)) {
                         ret = -EBUSY;
                         goto out;
                 }
                 ret = res_counter_set_limit(&memcg->kmem, val);
                 VM_BUG_ON(ret);
 
                 ret = memcg_update_cache_sizes(memcg);
                 if (ret) {
                         res_counter_set_limit(&memcg->kmem, RES_COUNTER_MAX);
                         goto out;
                 }
                 static_key_slow_inc(&memcg_kmem_enabled_key);
                 /*
                  * setting the active bit after the inc will guarantee no one
                  * starts accounting before all call sites are patched
                  */
                 memcg_kmem_set_active(memcg);
         } else
                 ret = res_counter_set_limit(&memcg->kmem, val);
 out:
         mutex_unlock(&set_limit_mutex);
         mutex_unlock(&memcg_create_mutex);
 #endif
         return ret;
 }
 
 #ifdef CONFIG_MEMCG_KMEM
 static int memcg_propagate_kmem(struct mem_cgroup *memcg)
 {
         int ret = 0;
         struct mem_cgroup *parent = parent_mem_cgroup(memcg);
         if (!parent)
                 goto out;
 
         memcg->kmem_account_flags = parent->kmem_account_flags;
         /*
          * When that happen, we need to disable the static branch only on those
          * memcgs that enabled it. To achieve this, we would be forced to
          * complicate the code by keeping track of which memcgs were the ones
          * that actually enabled limits, and which ones got it from its
          * parents.
          *
          * It is a lot simpler just to do static_key_slow_inc() on every child
          * that is accounted.
          */
         if (!memcg_kmem_is_active(memcg))
                 goto out;
 
         /*
          * __mem_cgroup_free() will issue static_key_slow_dec() because this
          * memcg is active already. If the later initialization fails then the
          * cgroup core triggers the cleanup so we do not have to do it here.
          */
         static_key_slow_inc(&memcg_kmem_enabled_key);
 
         mutex_lock(&set_limit_mutex);
         memcg_stop_kmem_account();
         ret = memcg_update_cache_sizes(memcg);
         memcg_resume_kmem_account();
         mutex_unlock(&set_limit_mutex);
 out:
         return ret;
 }
 #endif /* CONFIG_MEMCG_KMEM */
 
 /*
  * The user of this function is...
  * RES_LIMIT.
  */
 static int mem_cgroup_write(struct cgroup_subsys_state *css, struct cftype *cft,
                             const char *buffer)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         enum res_type type;
         int name;
         unsigned long long val;
         int ret;
 
         type = MEMFILE_TYPE(cft->private);
         name = MEMFILE_ATTR(cft->private);
 
         switch (name) {
         case RES_LIMIT:
                 if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
                         ret = -EINVAL;
                         break;
                 }
                 /* 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 if (type == _MEMSWAP)
                         ret = mem_cgroup_resize_memsw_limit(memcg, val);
                 else if (type == _KMEM)
                         ret = memcg_update_kmem_limit(css, val);
                 else
                         return -EINVAL;
                 break;
         case RES_SOFT_LIMIT:
                 ret = res_counter_memparse_write_strategy(buffer, &val);
                 if (ret)
                         break;
                 /*
                  * For memsw, soft limits are hard to implement in terms
                  * of semantics, for now, we support soft limits for
                  * control without swap
                  */
                 if (type == _MEM)
                         ret = res_counter_set_soft_limit(&memcg->res, val);
                 else
                         ret = -EINVAL;
                 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)
 {
         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);
         if (!memcg->use_hierarchy)
                 goto out;
 
         while (css_parent(&memcg->css)) {
                 memcg = mem_cgroup_from_css(css_parent(&memcg->css));
                 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;
 }
 
 static int mem_cgroup_reset(struct cgroup_subsys_state *css, unsigned int event)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         int name;
         enum res_type type;
 
         type = MEMFILE_TYPE(event);
         name = MEMFILE_ATTR(event);
 
         switch (name) {
         case RES_MAX_USAGE:
                 if (type == _MEM)
                         res_counter_reset_max(&memcg->res);
                 else if (type == _MEMSWAP)
                         res_counter_reset_max(&memcg->memsw);
                 else if (type == _KMEM)
                         res_counter_reset_max(&memcg->kmem);
                 else
                         return -EINVAL;
                 break;
         case RES_FAILCNT:
                 if (type == _MEM)
                         res_counter_reset_failcnt(&memcg->res);
                 else if (type == _MEMSWAP)
                         res_counter_reset_failcnt(&memcg->memsw);
                 else if (type == _KMEM)
                         res_counter_reset_failcnt(&memcg->kmem);
                 else
                         return -EINVAL;
                 break;
         }
 
         return 0;
 }
 
 static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state *css,
                                         struct cftype *cft)
 {
         return mem_cgroup_from_css(css)->move_charge_at_immigrate;
 }
 
 #ifdef CONFIG_MMU
 static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
                                         struct cftype *cft, u64 val)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
         if (val >= (1 << NR_MOVE_TYPE))
                 return -EINVAL;
 
         /*
          * No kind of locking is needed in here, because ->can_attach() will
          * check this value once in the beginning of the process, and then carry
          * on with stale data. This means that changes to this value will only
          * affect task migrations starting after the change.
          */
         memcg->move_charge_at_immigrate = val;
         return 0;
 }
 #else
 static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
                                         struct cftype *cft, u64 val)
 {
         return -ENOSYS;
 }
 #endif
 
 #ifdef CONFIG_NUMA
 static int memcg_numa_stat_show(struct cgroup_subsys_state *css,
                                 struct cftype *cft, struct seq_file *m)
 {
         struct numa_stat {
                 const char *name;
                 unsigned int lru_mask;
         };
 
         static const struct numa_stat stats[] = {
                 { "total", LRU_ALL },
                 { "file", LRU_ALL_FILE },
                 { "anon", LRU_ALL_ANON },
                 { "unevictable", BIT(LRU_UNEVICTABLE) },
         };
         const struct numa_stat *stat;
         int nid;
         unsigned long nr;
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
         for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
                 nr = mem_cgroup_nr_lru_pages(memcg, stat->lru_mask);
                 seq_printf(m, "%s=%lu", stat->name, nr);
                 for_each_node_state(nid, N_MEMORY) {
                         nr = mem_cgroup_node_nr_lru_pages(memcg, nid,
                                                           stat->lru_mask);
                         seq_printf(m, " N%d=%lu", nid, nr);
                 }
                 seq_putc(m, '\n');
         }
 
         for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
                 struct mem_cgroup *iter;
 
                 nr = 0;
                 for_each_mem_cgroup_tree(iter, memcg)
                         nr += mem_cgroup_nr_lru_pages(iter, stat->lru_mask);
                 seq_printf(m, "hierarchical_%s=%lu", stat->name, nr);
                 for_each_node_state(nid, N_MEMORY) {
                         nr = 0;
                         for_each_mem_cgroup_tree(iter, memcg)
                                 nr += mem_cgroup_node_nr_lru_pages(
                                         iter, nid, stat->lru_mask);
                         seq_printf(m, " N%d=%lu", nid, nr);
                 }
                 seq_putc(m, '\n');
         }
 
         return 0;
 }
 #endif /* CONFIG_NUMA */
 
 static inline void mem_cgroup_lru_names_not_uptodate(void)
 {
         BUILD_BUG_ON(ARRAY_SIZE(mem_cgroup_lru_names) != NR_LRU_LISTS);
 }
 
 static int memcg_stat_show(struct cgroup_subsys_state *css, struct cftype *cft,
                                  struct seq_file *m)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct mem_cgroup *mi;
         unsigned int i;
 
         for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
                 if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
                         continue;
                 seq_printf(m, "%s %ld\n", mem_cgroup_stat_names[i],
                            mem_cgroup_read_stat(memcg, i) * PAGE_SIZE);
         }
 
         for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++)
                 seq_printf(m, "%s %lu\n", mem_cgroup_events_names[i],
                            mem_cgroup_read_events(memcg, i));
 
         for (i = 0; i < NR_LRU_LISTS; i++)
                 seq_printf(m, "%s %lu\n", mem_cgroup_lru_names[i],
                            mem_cgroup_nr_lru_pages(memcg, BIT(i)) * PAGE_SIZE);
 
         /* Hierarchical information */
         {
                 unsigned long long limit, memsw_limit;
                 memcg_get_hierarchical_limit(memcg, &limit, &memsw_limit);
                 seq_printf(m, "hierarchical_memory_limit %llu\n", limit);
                 if (do_swap_account)
                         seq_printf(m, "hierarchical_memsw_limit %llu\n",
                                    memsw_limit);
         }
 
         for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
                 long long val = 0;
 
                 if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
                         continue;
                 for_each_mem_cgroup_tree(mi, memcg)
                         val += mem_cgroup_read_stat(mi, i) * PAGE_SIZE;
                 seq_printf(m, "total_%s %lld\n", mem_cgroup_stat_names[i], val);
         }
 
         for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++) {
                 unsigned long long val = 0;
 
                 for_each_mem_cgroup_tree(mi, memcg)
                         val += mem_cgroup_read_events(mi, i);
                 seq_printf(m, "total_%s %llu\n",
                            mem_cgroup_events_names[i], val);
         }
 
         for (i = 0; i < NR_LRU_LISTS; i++) {
                 unsigned long long val = 0;
 
                 for_each_mem_cgroup_tree(mi, memcg)
                         val += mem_cgroup_nr_lru_pages(mi, BIT(i)) * PAGE_SIZE;
                 seq_printf(m, "total_%s %llu\n", mem_cgroup_lru_names[i], val);
         }
 
 #ifdef CONFIG_DEBUG_VM
         {
                 int nid, zid;
                 struct mem_cgroup_per_zone *mz;
                 struct zone_reclaim_stat *rstat;
                 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(memcg, nid, zid);
                                 rstat = &mz->lruvec.reclaim_stat;
 
                                 recent_rotated[0] += rstat->recent_rotated[0];
                                 recent_rotated[1] += rstat->recent_rotated[1];
                                 recent_scanned[0] += rstat->recent_scanned[0];
                                 recent_scanned[1] += rstat->recent_scanned[1];
                         }
                 seq_printf(m, "recent_rotated_anon %lu\n", recent_rotated[0]);
                 seq_printf(m, "recent_rotated_file %lu\n", recent_rotated[1]);
                 seq_printf(m, "recent_scanned_anon %lu\n", recent_scanned[0]);
                 seq_printf(m, "recent_scanned_file %lu\n", recent_scanned[1]);
         }
 #endif
 
         return 0;
 }
 
 static u64 mem_cgroup_swappiness_read(struct cgroup_subsys_state *css,
                                       struct cftype *cft)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
         return mem_cgroup_swappiness(memcg);
 }
 
 static int mem_cgroup_swappiness_write(struct cgroup_subsys_state *css,
                                        struct cftype *cft, u64 val)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(&memcg->css));
 
         if (val > 100 || !parent)
                 return -EINVAL;
 
         mutex_lock(&memcg_create_mutex);
 
         /* If under hierarchy, only empty-root can set this value */
         if ((parent->use_hierarchy) || memcg_has_children(memcg)) {
                 mutex_unlock(&memcg_create_mutex);
                 return -EINVAL;
         }
 
         memcg->swappiness = val;
 
         mutex_unlock(&memcg_create_mutex);
 
         return 0;
 }
 
 static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
 {
         struct mem_cgroup_threshold_ary *t;
         u64 usage;
         int i;
 
         rcu_read_lock();
         if (!swap)
                 t = rcu_dereference(memcg->thresholds.primary);
         else
                 t = rcu_dereference(memcg->memsw_thresholds.primary);
 
         if (!t)
                 goto unlock;
 
         usage = mem_cgroup_usage(memcg, swap);
 
         /*
          * current_threshold points to threshold just below or equal to usage.
          * If it's not true, a threshold was crossed after last
          * call of __mem_cgroup_threshold().
          */
         i = t->current_threshold;
 
         /*
          * Iterate backward over array of thresholds starting from
          * current_threshold and check if a threshold is crossed.
          * If none of thresholds below usage is crossed, we read
          * only one element of the array here.
          */
         for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--)
                 eventfd_signal(t->entries[i].eventfd, 1);
 
         /* i = current_threshold + 1 */
         i++;
 
         /*
          * Iterate forward over array of thresholds starting from
          * current_threshold+1 and check if a threshold is crossed.
          * If none of thresholds above usage is crossed, we read
          * only one element of the array here.
          */
         for (; i < t->size && unlikely(t->entries[i].threshold <= usage); i++)
                 eventfd_signal(t->entries[i].eventfd, 1);
 
         /* Update current_threshold */
         t->current_threshold = i - 1;
 unlock:
         rcu_read_unlock();
 }
 
 static void mem_cgroup_threshold(struct mem_cgroup *memcg)
 {
         while (memcg) {
                 __mem_cgroup_threshold(memcg, false);
                 if (do_swap_account)
                         __mem_cgroup_threshold(memcg, true);
 
                 memcg = parent_mem_cgroup(memcg);
         }
 }
 
 static int compare_thresholds(const void *a, const void *b)
 {
         const struct mem_cgroup_threshold *_a = a;
         const struct mem_cgroup_threshold *_b = b;
 
         if (_a->threshold > _b->threshold)
                 return 1;
 
         if (_a->threshold < _b->threshold)
                 return -1;
 
         return 0;
 }
 
 static int mem_cgroup_oom_notify_cb(struct mem_cgroup *memcg)
 {
         struct mem_cgroup_eventfd_list *ev;
 
         list_for_each_entry(ev, &memcg->oom_notify, list)
                 eventfd_signal(ev->eventfd, 1);
         return 0;
 }
 
 static void mem_cgroup_oom_notify(struct mem_cgroup *memcg)
 {
         struct mem_cgroup *iter;
 
         for_each_mem_cgroup_tree(iter, memcg)
                 mem_cgroup_oom_notify_cb(iter);
 }
 
 static int mem_cgroup_usage_register_event(struct cgroup_subsys_state *css,
         struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct mem_cgroup_thresholds *thresholds;
         struct mem_cgroup_threshold_ary *new;
         enum res_type type = MEMFILE_TYPE(cft->private);
         u64 threshold, usage;
         int i, size, ret;
 
         ret = res_counter_memparse_write_strategy(args, &threshold);
         if (ret)
                 return ret;
 
         mutex_lock(&memcg->thresholds_lock);
 
         if (type == _MEM)
                 thresholds = &memcg->thresholds;
         else if (type == _MEMSWAP)
                 thresholds = &memcg->memsw_thresholds;
         else
                 BUG();
 
         usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
 
         /* Check if a threshold crossed before adding a new one */
         if (thresholds->primary)
                 __mem_cgroup_threshold(memcg, type == _MEMSWAP);
 
         size = thresholds->primary ? thresholds->primary->size + 1 : 1;
 
         /* Allocate memory for new array of thresholds */
         new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
                         GFP_KERNEL);
         if (!new) {
                 ret = -ENOMEM;
                 goto unlock;
         }
         new->size = size;
 
         /* Copy thresholds (if any) to new array */
         if (thresholds->primary) {
                 memcpy(new->entries, thresholds->primary->entries, (size - 1) *
                                 sizeof(struct mem_cgroup_threshold));
         }
 
         /* Add new threshold */
         new->entries[size - 1].eventfd = eventfd;
         new->entries[size - 1].threshold = threshold;
 
         /* Sort thresholds. Registering of new threshold isn't time-critical */
         sort(new->entries, size, sizeof(struct mem_cgroup_threshold),
                         compare_thresholds, NULL);
 
         /* Find current threshold */
         new->current_threshold = -1;
         for (i = 0; i < size; i++) {
                 if (new->entries[i].threshold <= usage) {
                         /*
                          * new->current_threshold will not be used until
                          * rcu_assign_pointer(), so it's safe to increment
                          * it here.
                          */
                         ++new->current_threshold;
                 } else
                         break;
         }
 
         /* Free old spare buffer and save old primary buffer as spare */
         kfree(thresholds->spare);
         thresholds->spare = thresholds->primary;
 
         rcu_assign_pointer(thresholds->primary, new);
 
         /* To be sure that nobody uses thresholds */
         synchronize_rcu();
 
 unlock:
         mutex_unlock(&memcg->thresholds_lock);
 
         return ret;
 }
 
 static void mem_cgroup_usage_unregister_event(struct cgroup_subsys_state *css,
         struct cftype *cft, struct eventfd_ctx *eventfd)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct mem_cgroup_thresholds *thresholds;
         struct mem_cgroup_threshold_ary *new;
         enum res_type type = MEMFILE_TYPE(cft->private);
         u64 usage;
         int i, j, size;
 
         mutex_lock(&memcg->thresholds_lock);
         if (type == _MEM)
                 thresholds = &memcg->thresholds;
         else if (type == _MEMSWAP)
                 thresholds = &memcg->memsw_thresholds;
         else
                 BUG();
 
         if (!thresholds->primary)
                 goto unlock;
 
         usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
 
         /* Check if a threshold crossed before removing */
         __mem_cgroup_threshold(memcg, type == _MEMSWAP);
 
         /* Calculate new number of threshold */
         size = 0;
         for (i = 0; i < thresholds->primary->size; i++) {
                 if (thresholds->primary->entries[i].eventfd != eventfd)
                         size++;
         }
 
         new = thresholds->spare;
 
         /* Set thresholds array to NULL if we don't have thresholds */
         if (!size) {
                 kfree(new);
                 new = NULL;
                 goto swap_buffers;
         }
 
         new->size = size;
 
         /* Copy thresholds and find current threshold */
         new->current_threshold = -1;
         for (i = 0, j = 0; i < thresholds->primary->size; i++) {
                 if (thresholds->primary->entries[i].eventfd == eventfd)
                         continue;
 
                 new->entries[j] = thresholds->primary->entries[i];
                 if (new->entries[j].threshold <= usage) {
                         /*
                          * new->current_threshold will not be used
                          * until rcu_assign_pointer(), so it's safe to increment
                          * it here.
                          */
                         ++new->current_threshold;
                 }
                 j++;
         }
 
 swap_buffers:
         /* Swap primary and spare array */
         thresholds->spare = thresholds->primary;
         /* If all events are unregistered, free the spare array */
         if (!new) {
                 kfree(thresholds->spare);
                 thresholds->spare = NULL;
         }
 
         rcu_assign_pointer(thresholds->primary, new);
 
         /* To be sure that nobody uses thresholds */
         synchronize_rcu();
 unlock:
         mutex_unlock(&memcg->thresholds_lock);
 }
 
 static int mem_cgroup_oom_register_event(struct cgroup_subsys_state *css,
         struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct mem_cgroup_eventfd_list *event;
         enum res_type type = MEMFILE_TYPE(cft->private);
 
         BUG_ON(type != _OOM_TYPE);
         event = kmalloc(sizeof(*event), GFP_KERNEL);
         if (!event)
                 return -ENOMEM;
 
         spin_lock(&memcg_oom_lock);
 
         event->eventfd = eventfd;
         list_add(&event->list, &memcg->oom_notify);
 
         /* already in OOM ? */
         if (atomic_read(&memcg->under_oom))
                 eventfd_signal(eventfd, 1);
         spin_unlock(&memcg_oom_lock);
 
         return 0;
 }
 
 static void mem_cgroup_oom_unregister_event(struct cgroup_subsys_state *css,
         struct cftype *cft, struct eventfd_ctx *eventfd)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct mem_cgroup_eventfd_list *ev, *tmp;
         enum res_type type = MEMFILE_TYPE(cft->private);
 
         BUG_ON(type != _OOM_TYPE);
 
         spin_lock(&memcg_oom_lock);
 
         list_for_each_entry_safe(ev, tmp, &memcg->oom_notify, list) {
                 if (ev->eventfd == eventfd) {
                         list_del(&ev->list);
                         kfree(ev);
                 }
         }
 
         spin_unlock(&memcg_oom_lock);
 }
 
 static int mem_cgroup_oom_control_read(struct cgroup_subsys_state *css,
         struct cftype *cft,  struct cgroup_map_cb *cb)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
         cb->fill(cb, "oom_kill_disable", memcg->oom_kill_disable);
 
         if (atomic_read(&memcg->under_oom))
                 cb->fill(cb, "under_oom", 1);
         else
                 cb->fill(cb, "under_oom", 0);
         return 0;
 }
 
 static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
         struct cftype *cft, u64 val)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(&memcg->css));
 
         /* cannot set to root cgroup and only 0 and 1 are allowed */
         if (!parent || !((val == 0) || (val == 1)))
                 return -EINVAL;
 
         mutex_lock(&memcg_create_mutex);
         /* oom-kill-disable is a flag for subhierarchy. */
         if ((parent->use_hierarchy) || memcg_has_children(memcg)) {
                 mutex_unlock(&memcg_create_mutex);
                 return -EINVAL;
         }
         memcg->oom_kill_disable = val;
         if (!val)
                 memcg_oom_recover(memcg);
         mutex_unlock(&memcg_create_mutex);
         return 0;
 }
 
 #ifdef CONFIG_MEMCG_KMEM
 static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
         int ret;
 
         memcg->kmemcg_id = -1;
         ret = memcg_propagate_kmem(memcg);
         if (ret)
                 return ret;
 
         return mem_cgroup_sockets_init(memcg, ss);
 }
 
 static void memcg_destroy_kmem(struct mem_cgroup *memcg)
 {
         mem_cgroup_sockets_destroy(memcg);
 }
 
 static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
 {
         if (!memcg_kmem_is_active(memcg))
                 return;
 
         /*
          * kmem charges can outlive the cgroup. In the case of slab
          * pages, for instance, a page contain objects from various
          * processes. As we prevent from taking a reference for every
          * such allocation we have to be careful when doing uncharge
          * (see memcg_uncharge_kmem) and here during offlining.
          *
          * The idea is that that only the _last_ uncharge which sees
          * the dead memcg will drop the last reference. An additional
          * reference is taken here before the group is marked dead
          * which is then paired with css_put during uncharge resp. here.
          *
          * Although this might sound strange as this path is called from
          * css_offline() when the referencemight have dropped down to 0
          * and shouldn't be incremented anymore (css_tryget would fail)
          * we do not have other options because of the kmem allocations
          * lifetime.
          */
         css_get(&memcg->css);
 
         memcg_kmem_mark_dead(memcg);
 
         if (res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0)
                 return;
 
         if (memcg_kmem_test_and_clear_dead(memcg))
                 css_put(&memcg->css);
 }
 #else
 static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
 {
         return 0;
 }
 
 static void memcg_destroy_kmem(struct mem_cgroup *memcg)
 {
 }
 
 static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
 {
 }
 #endif
 
 static struct cftype mem_cgroup_files[] = {
         {
                 .name = "usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
                 .read = mem_cgroup_read,
                 .register_event = mem_cgroup_usage_register_event,
                 .unregister_event = mem_cgroup_usage_unregister_event,
         },
         {
                 .name = "max_usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEM, RES_MAX_USAGE),
                 .trigger = mem_cgroup_reset,
                 .read = mem_cgroup_read,
         },
         {
                 .name = "limit_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEM, RES_LIMIT),
                 .write_string = mem_cgroup_write,
                 .read = mem_cgroup_read,
         },
         {
                 .name = "soft_limit_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEM, RES_SOFT_LIMIT),
                 .write_string = mem_cgroup_write,
                 .read = mem_cgroup_read,
         },
         {
                 .name = "failcnt",
                 .private = MEMFILE_PRIVATE(_MEM, RES_FAILCNT),
                 .trigger = mem_cgroup_reset,
                 .read = mem_cgroup_read,
         },
         {
                 .name = "stat",
                 .read_seq_string = memcg_stat_show,
         },
         {
                 .name = "force_empty",
                 .trigger = mem_cgroup_force_empty_write,
         },
         {
                 .name = "use_hierarchy",
                 .flags = CFTYPE_INSANE,
                 .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,
         },
         {
                 .name = "move_charge_at_immigrate",
                 .read_u64 = mem_cgroup_move_charge_read,
                 .write_u64 = mem_cgroup_move_charge_write,
         },
         {
                 .name = "oom_control",
                 .read_map = mem_cgroup_oom_control_read,
                 .write_u64 = mem_cgroup_oom_control_write,
                 .register_event = mem_cgroup_oom_register_event,
                 .unregister_event = mem_cgroup_oom_unregister_event,
                 .private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
         },
         {
                 .name = "pressure_level",
                 .register_event = vmpressure_register_event,
                 .unregister_event = vmpressure_unregister_event,
         },
 #ifdef CONFIG_NUMA
         {
                 .name = "numa_stat",
                 .read_seq_string = memcg_numa_stat_show,
         },
 #endif
 #ifdef CONFIG_MEMCG_KMEM
         {
                 .name = "kmem.limit_in_bytes",
                 .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
                 .write_string = mem_cgroup_write,
                 .read = mem_cgroup_read,
         },
         {
                 .name = "kmem.usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
                 .read = mem_cgroup_read,
         },
         {
                 .name = "kmem.failcnt",
                 .private = MEMFILE_PRIVATE(_KMEM, RES_FAILCNT),
                 .trigger = mem_cgroup_reset,
                 .read = mem_cgroup_read,
         },
         {
                 .name = "kmem.max_usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_KMEM, RES_MAX_USAGE),
                 .trigger = mem_cgroup_reset,
                 .read = mem_cgroup_read,
         },
 #ifdef CONFIG_SLABINFO
         {
                 .name = "kmem.slabinfo",
                 .read_seq_string = mem_cgroup_slabinfo_read,
         },
 #endif
 #endif
         { },    /* terminate */
 };
 
 #ifdef CONFIG_MEMCG_SWAP
 static struct cftype memsw_cgroup_files[] = {
         {
                 .name = "memsw.usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
                 .read = mem_cgroup_read,
                 .register_event = mem_cgroup_usage_register_event,
                 .unregister_event = mem_cgroup_usage_unregister_event,
         },
         {
                 .name = "memsw.max_usage_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
                 .trigger = mem_cgroup_reset,
                 .read = mem_cgroup_read,
         },
         {
                 .name = "memsw.limit_in_bytes",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_LIMIT),
                 .write_string = mem_cgroup_write,
                 .read = mem_cgroup_read,
         },
         {
                 .name = "memsw.failcnt",
                 .private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
                 .trigger = mem_cgroup_reset,
                 .read = mem_cgroup_read,
         },
         { },    /* terminate */
 };
 #endif
 static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
 {
         struct mem_cgroup_per_node *pn;
         struct mem_cgroup_per_zone *mz;
         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 = kzalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
         if (!pn)
                 return 1;
 
         for (zone = 0; zone < MAX_NR_ZONES; zone++) {
                 mz = &pn->zoneinfo[zone];
                 lruvec_init(&mz->lruvec);
                 mz->usage_in_excess = 0;
                 mz->on_tree = false;
                 mz->memcg = memcg;
         }
         memcg->nodeinfo[node] = pn;
         return 0;
 }
 
 static void free_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
 {
         kfree(memcg->nodeinfo[node]);
 }
 
 static struct mem_cgroup *mem_cgroup_alloc(void)
 {
         struct mem_cgroup *memcg;
         size_t size = memcg_size();
 
         /* Can be very big if nr_node_ids is very big */
         if (size < PAGE_SIZE)
                 memcg = kzalloc(size, GFP_KERNEL);
         else
                 memcg = vzalloc(size);
 
         if (!memcg)
                 return NULL;
 
         memcg->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
         if (!memcg->stat)
                 goto out_free;
         spin_lock_init(&memcg->pcp_counter_lock);
         return memcg;
 
 out_free:
         if (size < PAGE_SIZE)
                 kfree(memcg);
         else
                 vfree(memcg);
         return NULL;
 }
 
 /*
  * 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 *memcg)
 {
         int node;
         size_t size = memcg_size();
 
         mem_cgroup_remove_from_trees(memcg);
 
         for_each_node(node)
                 free_mem_cgroup_per_zone_info(memcg, node);
 
         free_percpu(memcg->stat);
 
         /*
          * We need to make sure that (at least for now), the jump label
          * destruction code runs outside of the cgroup lock. This is because
          * get_online_cpus(), which is called from the static_branch update,
          * can't be called inside the cgroup_lock. cpusets are the ones
          * enforcing this dependency, so if they ever change, we might as well.
          *
          * schedule_work() will guarantee this happens. Be careful if you need
          * to move this code around, and make sure it is outside
          * the cgroup_lock.
          */
         disarm_static_keys(memcg);
         if (size < PAGE_SIZE)
                 kfree(memcg);
         else
                 vfree(memcg);
 }
 
 /*
  * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.
  */
 struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
 {
         if (!memcg->res.parent)
                 return NULL;
         return mem_cgroup_from_res_counter(memcg->res.parent, res);
 }
 EXPORT_SYMBOL(parent_mem_cgroup);
 
 static void __init mem_cgroup_soft_limit_tree_init(void)
 {
         struct mem_cgroup_tree_per_node *rtpn;
         struct mem_cgroup_tree_per_zone *rtpz;
         int tmp, node, zone;
 
         for_each_node(node) {
                 tmp = node;
                 if (!node_state(node, N_NORMAL_MEMORY))
                         tmp = -1;
                 rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp);
                 BUG_ON(!rtpn);
 
                 soft_limit_tree.rb_tree_per_node[node] = rtpn;
 
                 for (zone = 0; zone < MAX_NR_ZONES; zone++) {
                         rtpz = &rtpn->rb_tree_per_zone[zone];
                         rtpz->rb_root = RB_ROOT;
                         spin_lock_init(&rtpz->lock);
                 }
         }
 }
 
 static struct cgroup_subsys_state * __ref
 mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
 {
         struct mem_cgroup *memcg;
         long error = -ENOMEM;
         int node;
 
         memcg = mem_cgroup_alloc();
         if (!memcg)
                 return ERR_PTR(error);
 
         for_each_node(node)
                 if (alloc_mem_cgroup_per_zone_info(memcg, node))
                         goto free_out;
 
         /* root ? */
         if (parent_css == NULL) {
                 root_mem_cgroup = memcg;
                 res_counter_init(&memcg->res, NULL);
                 res_counter_init(&memcg->memsw, NULL);
                 res_counter_init(&memcg->kmem, NULL);
         }
 
         memcg->last_scanned_node = MAX_NUMNODES;
         INIT_LIST_HEAD(&memcg->oom_notify);
         memcg->move_charge_at_immigrate = 0;
         mutex_init(&memcg->thresholds_lock);
         spin_lock_init(&memcg->move_lock);
         vmpressure_init(&memcg->vmpressure);
 
         return &memcg->css;
 
 free_out:
         __mem_cgroup_free(memcg);
         return ERR_PTR(error);
 }
 
 static int
 mem_cgroup_css_online(struct cgroup_subsys_state *css)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(css));
         int error = 0;
 
         if (css->cgroup->id > MEM_CGROUP_ID_MAX)
                 return -ENOSPC;
 
         if (!parent)
                 return 0;
 
         mutex_lock(&memcg_create_mutex);
 
         memcg->use_hierarchy = parent->use_hierarchy;
         memcg->oom_kill_disable = parent->oom_kill_disable;
         memcg->swappiness = mem_cgroup_swappiness(parent);
 
         if (parent->use_hierarchy) {
                 res_counter_init(&memcg->res, &parent->res);
                 res_counter_init(&memcg->memsw, &parent->memsw);
                 res_counter_init(&memcg->kmem, &parent->kmem);
 
                 /*
                  * No need to take a reference to the parent because cgroup
                  * core guarantees its existence.
                  */
         } else {
                 res_counter_init(&memcg->res, NULL);
                 res_counter_init(&memcg->memsw, NULL);
                 res_counter_init(&memcg->kmem, NULL);
                 /*
                  * Deeper hierachy with use_hierarchy == false doesn't make
                  * much sense so let cgroup subsystem know about this
                  * unfortunate state in our controller.
                  */
                 if (parent != root_mem_cgroup)
                         mem_cgroup_subsys.broken_hierarchy = true;
         }
 
         error = memcg_init_kmem(memcg, &mem_cgroup_subsys);
         mutex_unlock(&memcg_create_mutex);
         return error;
 }
 
 /*
  * Announce all parents that a group from their hierarchy is gone.
  */
 static void mem_cgroup_invalidate_reclaim_iterators(struct mem_cgroup *memcg)
 {
         struct mem_cgroup *parent = memcg;
 
         while ((parent = parent_mem_cgroup(parent)))
                 mem_cgroup_iter_invalidate(parent);
 
         /*
          * if the root memcg is not hierarchical we have to check it
          * explicitely.
          */
         if (!root_mem_cgroup->use_hierarchy)
                 mem_cgroup_iter_invalidate(root_mem_cgroup);
 }
 
 static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         struct cgroup_subsys_state *iter;
 
         kmem_cgroup_css_offline(memcg);
 
         mem_cgroup_invalidate_reclaim_iterators(memcg);
 
         /*
          * This requires that offlining is serialized.  Right now that is
          * guaranteed because css_killed_work_fn() holds the cgroup_mutex.
          */
         rcu_read_lock();
         css_for_each_descendant_post(iter, css) {
                 rcu_read_unlock();
                 mem_cgroup_reparent_charges(mem_cgroup_from_css(iter));
                 rcu_read_lock();
         }
         rcu_read_unlock();
 
         mem_cgroup_destroy_all_caches(memcg);
         vmpressure_cleanup(&memcg->vmpressure);
 }
 
 static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
 {
         struct mem_cgroup *memcg = mem_cgroup_from_css(css);
         /*
          * XXX: css_offline() would be where we should reparent all
          * memory to prepare the cgroup for destruction.  However,
          * memcg does not do css_tryget() and res_counter charging
          * under the same RCU lock region, which means that charging
          * could race with offlining.  Offlining only happens to
          * cgroups with no tasks in them but charges can show up
          * without any tasks from the swapin path when the target
          * memcg is looked up from the swapout record and not from the
          * current task as it usually is.  A race like this can leak
          * charges and put pages with stale cgroup pointers into
          * circulation:
          *
          * #0                        #1
          *                           lookup_swap_cgroup_id()
          *                           rcu_read_lock()
          *                           mem_cgroup_lookup()
          *                           css_tryget()
          *                           rcu_read_unlock()
          * disable css_tryget()
          * call_rcu()
          *   offline_css()
          *     reparent_charges()
          *                           res_counter_charge()
          *                           css_put()
          *                             css_free()
          *                           pc->mem_cgroup = dead memcg
          *                           add page to lru
          *
          * The bulk of the charges are still moved in offline_css() to
          * avoid pinning a lot of pages in case a long-term reference
          * like a swapout record is deferring the css_free() to long
          * after offlining.  But this makes sure we catch any charges
          * made after offlining:
          */
         mem_cgroup_reparent_charges(memcg);
 
         memcg_destroy_kmem(memcg);
         __mem_cgroup_free(memcg);
 }
 
 #ifdef CONFIG_MMU
 /* Handlers for move charge at task migration. */
 #define PRECHARGE_COUNT_AT_ONCE 256
 static int mem_cgroup_do_precharge(unsigned long count)
 {
         int ret = 0;
         int batch_count = PRECHARGE_COUNT_AT_ONCE;
         struct mem_cgroup *memcg = mc.to;
 
         if (mem_cgroup_is_root(memcg)) {
                 mc.precharge += count;
                 /* we don't need css_get for root */
                 return ret;
         }
         /* try to charge at once */
         if (count > 1) {
                 struct res_counter *dummy;
                 /*
                  * "memcg" cannot be under rmdir() because we've already checked
                  * by cgroup_lock_live_cgroup() that it is not removed and we
                  * are still under the same cgroup_mutex. So we can postpone
                  * css_get().
                  */
                 if (res_counter_charge(&memcg->res, PAGE_SIZE * count, &dummy))
                         goto one_by_one;
                 if (do_swap_account && res_counter_charge(&memcg->memsw,
                                                 PAGE_SIZE * count, &dummy)) {
                         res_counter_uncharge(&memcg->res, PAGE_SIZE * count);
                         goto one_by_one;
                 }
                 mc.precharge += count;
                 return ret;
         }
 one_by_one:
         /* fall back to one by one charge */
         while (count--) {
                 if (signal_pending(current)) {
                         ret = -EINTR;
                         break;
                 }
                 if (!batch_count--) {
                         batch_count = PRECHARGE_COUNT_AT_ONCE;
                         cond_resched();
                 }
                 ret = __mem_cgroup_try_charge(NULL,
                                         GFP_KERNEL, 1, &memcg, false);
                 if (ret)
                         /* mem_cgroup_clear_mc() will do uncharge later */
                         return ret;
                 mc.precharge++;
         }
         return ret;
 }
 
 /**
  * get_mctgt_type - get target type of moving charge
  * @vma: the vma the pte to be checked belongs
  * @addr: the address corresponding to the pte to be checked
  * @ptent: the pte to be checked
  * @target: the pointer the target page or swap ent will be stored(can be NULL)
  *
  * Returns
  *   0(MC_TARGET_NONE): if the pte is not a target for move charge.
  *   1(MC_TARGET_PAGE): if the page corresponding to this pte is a target for
  *     move charge. if @target is not NULL, the page is stored in target->page
  *     with extra refcnt got(Callers should handle it).
  *   2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
  *     target for charge migration. if @target is not NULL, the entry is stored
  *     in target->ent.
  *
  * Called with pte lock held.
  */
 union mc_target {
         struct page     *page;