FreeBSD/Linux Kernel Cross Reference
sys/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/mm_inline.h>
    #include <linux/page_cgroup.h>
    #include <linux/cpu.h>
    #include <linux/oom.h>
    #include "internal.h"
    #include <net/sock.h>
    #include <net/ip.h>
    #include <net/tcp_memcontrol.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
    
    
    /*
     * Statistics for memory cgroup.
     */
    enum mem_cgroup_stat_index {
            /*
             * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
             */
            MEM_CGROUP_STAT_CACHE,     /* # of pages charged as cache */
            MEM_CGROUP_STAT_RSS,       /* # of pages charged as anon rss */
            MEM_CGROUP_STAT_FILE_MAPPED,  /* # of pages charged as file rss */
            MEM_CGROUP_STAT_SWAP, /* # of pages, swapped out */
            MEM_CGROUP_STAT_NSTATS,
    };
   
   static const char * const mem_cgroup_stat_names[] = {
           "cache",
           "rss",
           "mapped_file",
           "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",
   };
   
   /*
    * 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 {
           /* css_id of the last scanned hierarchy member */
           int position;
           /* 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];
   };
   
   struct mem_cgroup_lru_info {
           struct mem_cgroup_per_node *nodeinfo[MAX_NUMNODES];
   };
   
   /*
    * 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;
   
           union {
                   /*
                    * the counter to account for mem+swap usage.
                    */
                   struct res_counter memsw;
   
                   /*
                    * rcu_freeing is used only when freeing struct mem_cgroup,
                    * so put it into a union to avoid wasting more memory.
                    * It must be disjoint from the css field.  It could be
                    * in a union with the res field, but res plays a much
                    * larger part in mem_cgroup life than memsw, and might
                    * be of interest, even at time of free, when debugging.
                    * So share rcu_head with the less interesting memsw.
                    */
                   struct rcu_head rcu_freeing;
                   /*
                    * We also need some space for a worker in deferred freeing.
                    * By the time we call it, rcu_freeing is no longer in use.
                    */
                   struct work_struct work_freeing;
           };
   
           /*
            * the counter to account for kernel memory usage.
            */
           struct res_counter kmem;
           /*
            * Per cgroup active and inactive list, similar to the
            * per zone LRU lists.
            */
           struct mem_cgroup_lru_info info;
           int last_scanned_node;
   #if MAX_NUMNODES > 1
           nodemask_t      scan_nodes;
           atomic_t        numainfo_events;
           atomic_t        numainfo_updating;
   #endif
           /*
            * 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        refcnt;
   
           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;
   
   #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_INET)
           struct tcp_memcontrol 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
   };
   
   /* 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)
   {
           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" is 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 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.to->move_charge_at_immigrate);
   }
   
   static bool move_file(void)
   {
           return test_bit(MOVE_CHARGE_TYPE_FILE,
                                           &mc.to->move_charge_at_immigrate);
   }
   
   /*
    * 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)
   
   static void mem_cgroup_get(struct mem_cgroup *memcg);
   static void mem_cgroup_put(struct mem_cgroup *memcg);
   
   static inline
   struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s)
   {
           return container_of(s, struct mem_cgroup, css);
   }
   
   static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
   {
           return (memcg == root_mem_cgroup);
   }
   
   /* 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));
                           mem_cgroup_get(sk->sk_cgrp->memcg);
                           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)) {
                           mem_cgroup_get(memcg);
                           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;
                   mem_cgroup_put(memcg);
           }
   }
   
   struct cg_proto *tcp_proto_cgroup(struct mem_cgroup *memcg)
   {
           if (!memcg || mem_cgroup_is_root(memcg))
                   return NULL;
   
           return &memcg->tcp_mem.cg_proto;
   }
   EXPORT_SYMBOL(tcp_proto_cgroup);
   
   static void disarm_sock_keys(struct mem_cgroup *memcg)
   {
           if (!memcg_proto_activated(&memcg->tcp_mem.cg_proto))
                   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.
    * There are two main reasons for not using the css_id for this:
    *  1) 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.
    *
    *  2) In order not to violate the cgroup API, we would like to do all memory
    *     allocation in ->create(). At that point, we haven't yet allocated the
    *     css_id. Having a separate index prevents us from messing with the cgroup
    *     core for this
    *
    * 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 css_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
    * css_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 65535
   
   /*
    * 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)
   {
           return &memcg->info.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;
   
           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
           return val;
   }
   
   static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
                                            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);
   
           /* 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_cont(struct cgroup *cont)
  {
          return mem_cgroup_from_css(
                  cgroup_subsys_state(cont, mem_cgroup_subsys_id));
  }
  
  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_subsys_state(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;
  }
  
  /**
   * 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;
          int id = 0;
  
          if (mem_cgroup_disabled())
                  return NULL;
  
          if (!root)
                  root = root_mem_cgroup;
  
          if (prev && !reclaim)
                  id = css_id(&prev->css);
  
          if (prev && prev != root)
                  css_put(&prev->css);
  
          if (!root->use_hierarchy && root != root_mem_cgroup) {
                  if (prev)
                          return NULL;
                  return root;
          }
  
          while (!memcg) {
                  struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
                  struct cgroup_subsys_state *css;
  
                  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)
                                  return NULL;
                          id = iter->position;
                  }
  
                  rcu_read_lock();
                  css = css_get_next(&mem_cgroup_subsys, id + 1, &root->css, &id);
                  if (css) {
                          if (css == &root->css || css_tryget(css))
                                  memcg = mem_cgroup_from_css(css);
                  } else
                          id = 0;
                  rcu_read_unlock();
  
                  if (reclaim) {
                          iter->position = id;
                          if (!css)
                                  iter->generation++;
                          else if (!prev && memcg)
                                  reclaim->generation = iter->generation;
                  }
  
                  if (prev && !css)
                          return NULL;
          }
          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 css_is_ancestor(&memcg->css, &root_memcg->css);
  }
  
  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;
  }
  
  int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *memcg)
  {
          int ret;
          struct mem_cgroup *curr = NULL;
          struct task_struct *p;
  
          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.
                   */
                  task_lock(task);
                  curr = mem_cgroup_from_task(task);
                  if (curr)
                          css_get(&curr->css);
                  task_unlock(task);
          }
          if (!curr)
                  return 0;
          /*
           * 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;
  }
  
  int mem_cgroup_inactive_file_is_low(struct lruvec *lruvec)
  {
          unsigned long active;
          unsigned long inactive;
  
          inactive = mem_cgroup_get_lru_size(lruvec, LRU_INACTIVE_FILE);
          active = mem_cgroup_get_lru_size(lruvec, LRU_ACTIVE_FILE);
  
          return (active > inactive);
  }
  
  #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)
  {
          struct cgroup *cgrp = memcg->css.cgroup;
  
          /* root ? */
          if (cgrp->parent == NULL)
                  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);
  }
  
  /**
   * mem_cgroup_print_oom_info: Called from OOM with tasklist_lock held in read mode.
   * @memcg: The memory cgroup that went over limit
   * @p: Task that is going to be killed
   *
   * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
   * enabled
   */
  void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
  {
          struct cgroup *task_cgrp;
          struct cgroup *mem_cgrp;
          /*
           * Need a buffer in BSS, can't rely on allocations. The code relies
           * on the assumption that OOM is serialized for memory controller.
           * If this assumption is broken, revisit this code.
           */
          static char memcg_name[PATH_MAX];
          int ret;
  
          if (!memcg || !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();
  
          printk(KERN_INFO "Task in %s killed", memcg_name);
  
          rcu_read_lock();
          ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
          if (ret < 0) {
                  rcu_read_unlock();
                  goto done;
          }
          rcu_read_unlock();
  
          /*
           * Continues from above, so we don't need an KERN_ level
           */
          printk(KERN_CONT " as a result of limit of %s\n", memcg_name);
  done:
  
          printk(KERN_INFO "memory: usage %llukB, limit %llukB, failcnt %llu\n",
                  res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
                  res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
                  res_counter_read_u64(&memcg->res, RES_FAILCNT));
          printk(KERN_INFO "memory+swap: usage %llukB, limit %llukB, "
                  "failcnt %llu\n",
                  res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
                  res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
                  res_counter_read_u64(&memcg->memsw, RES_FAILCNT));
          printk(KERN_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));
  }
  
  /*
   * 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, 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)) {
                  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 cgroup *cgroup = iter->css.cgroup;
                  struct cgroup_iter it;
                  struct task_struct *task;
  
                  cgroup_iter_start(cgroup, &it);
                  while ((task = cgroup_iter_next(cgroup, &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:
                                  cgroup_iter_end(cgroup, &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);
                          }
                  }
                  cgroup_iter_end(cgroup, &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;
  }
  
  /*
   * Check OOM-Killer is already running under our hierarchy.
   * If someone is running, return false.
   * Has to be called with memcg_oom_lock
   */
  static bool mem_cgroup_oom_lock(struct mem_cgroup *memcg)
  {
          struct mem_cgroup *iter, *failed = NULL;
  
          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)
                  return true;
  
          /*
           * 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;
          }
          return false;
  }
  
  /*
   * Has to be called with memcg_oom_lock
   */
  static int mem_cgroup_oom_unlock(struct mem_cgroup *memcg)
  {
          struct mem_cgroup *iter;
  
          for_each_mem_cgroup_tree(iter, memcg)
                  iter->oom_lock = false;
          return 0;
  }
  
  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 DEFINE_SPINLOCK(memcg_oom_lock);
  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)
  {
          /* 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);
  }
  
  /*
   * try to call OOM killer. returns false if we should exit memory-reclaim loop.
   */
  static bool mem_cgroup_handle_oom(struct mem_cgroup *memcg, gfp_t mask,
                                    int order)
  {
          struct oom_wait_info owait;
          bool locked, need_to_kill;
  
          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);
          need_to_kill = true;
          mem_cgroup_mark_under_oom(memcg);
  
          /* At first, try to OOM lock hierarchy under memcg.*/
          spin_lock(&memcg_oom_lock);
          locked = mem_cgroup_oom_lock(memcg);
          /*
           * Even if signal_pending(), we can't quit charge() loop without
           * accounting. So, UNINTERRUPTIBLE is appropriate. But SIGKILL
           * under OOM is always welcomed, use TASK_KILLABLE here.
           */
          prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
          if (!locked || memcg->oom_kill_disable)
                  need_to_kill = false;
          if (locked)
                  mem_cgroup_oom_notify(memcg);
          spin_unlock(&memcg_oom_lock);
  
          if (need_to_kill) {
                  finish_wait(&memcg_oom_waitq, &owait.wait);
                  mem_cgroup_out_of_memory(memcg, mask, order);
          } else {
                  schedule();
                  finish_wait(&memcg_oom_waitq, &owait.wait);
          }
          spin_lock(&memcg_oom_lock);
          if (locked)
                  mem_cgroup_oom_unlock(memcg);
          memcg_wakeup_oom(memcg);
          spin_unlock(&memcg_oom_lock);
  
          mem_cgroup_unmark_under_oom(memcg);
  
          if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))
                  return false;
          /* Give chance to dying process */
          schedule_timeout_uninterruptible(1);
          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_page_stat_item 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;
  
          memcg = pc->mem_cgroup;
          if (unlikely(!memcg || !PageCgroupUsed(pc)))
                  return;
  
          switch (idx) {
          case MEMCG_NR_FILE_MAPPED:
                  idx = MEM_CGROUP_STAT_FILE_MAPPED;
                  break;
          default:
                  BUG();
          }
  
          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);
  }
  
  /*
   * 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 __cpuinit 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. */
          CHARGE_OOM_DIE,         /* the current is killed because of OOM */
  };
  
  static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
                                  unsigned int nr_pages, unsigned int min_pages,
                                  bool oom_check)
  {
          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 we don't need to call oom-killer at el, return immediately */
          if (!oom_check)
                  return CHARGE_NOMEM;
          /* check OOM */
          if (!mem_cgroup_handle_oom(mem_over_limit, gfp_mask, get_order(csize)))
                  return CHARGE_OOM_DIE;
  
          return CHARGE_RETRY;
  }
  
  /*
   * __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;
  
          /*
           * 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 oom_check;
  
                  /* If killed, bypass charge */
                  if (fatal_signal_pending(current)) {
                          css_put(&memcg->css);
                          goto bypass;
                  }
  
                  oom_check = false;
                  if (oom && !nr_oom_retries) {
                          oom_check = true;
                          nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
                  }
  
                  ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, nr_pages,
                      oom_check);
                  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) {
                                  css_put(&memcg->css);
                                  goto nomem;
                          }
                          /* If oom, we never return -ENOMEM */
                          nr_oom_retries--;
                          break;
                  case CHARGE_OOM_DIE: /* Killed by OOM Killer */
                          css_put(&memcg->css);
                          goto bypass;
                  }
          } while (ret != CHARGE_OK);
  
          if (batch > nr_pages)
                  refill_stock(memcg, batch - nr_pages);
          css_put(&memcg->css);
  done:
          *ptr = memcg;
          return 0;
  nomem:
          *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)
  {
          struct cgroup_subsys_state *css;
  
          /* ID 0 is unused ID */
          if (!id)
                  return NULL;
          css = css_lookup(&mem_cgroup_subsys, id);
          if (!css)
                  return NULL;
          return mem_cgroup_from_css(css);
  }
  
  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, 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 cachep->memcg_params->memcg_caches[memcg_cache_id(p->memcg)];
  }
  
  #ifdef CONFIG_SLABINFO
  static int mem_cgroup_slabinfo_read(struct cgroup *cont, struct cftype *cft,
                                          struct seq_file *m)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
          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;
          bool may_oom;
  
          ret = res_counter_charge(&memcg->kmem, size, &fail_res);
          if (ret)
                  return ret;
  
          /*
           * Conditions under which we can wait for the oom_killer. Those are
           * the same conditions tested by the core page allocator
           */
          may_oom = (gfp & __GFP_FS) && !(gfp & __GFP_NORETRY);
  
          _memcg = memcg;
          ret = __mem_cgroup_try_charge(NULL, gfp, size >> PAGE_SHIFT,
                                        &_memcg, may_oom);
  
          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;
  
          if (memcg_kmem_test_and_clear_dead(memcg))
                  mem_cgroup_put(memcg);
  }
  
  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);
  }
  
  int memcg_update_cache_size(struct kmem_cache *s, int num_groups)
  {
          struct memcg_cache_params *cur_params = s->memcg_params;
  
          VM_BUG_ON(s->memcg_params && !s->memcg_params->is_root_cache);
  
          if (num_groups > memcg_limited_groups_array_size) {
                  int i;
                  ssize_t size = memcg_caches_array_size(num_groups);
  
                  size *= sizeof(void *);
                  size += sizeof(struct memcg_cache_params);
  
                  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 = sizeof(struct memcg_cache_params);
  
          if (!memcg_kmem_enabled())
                  return 0;
  
          if (!memcg)
                  size += memcg_limited_groups_array_size * sizeof(void *);
  
          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;
          }
          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;
          mem_cgroup_put(memcg);
  
          mutex_lock(&memcg->slab_caches_mutex);
          list_del(&s->memcg_params->list);
          mutex_unlock(&memcg->slab_caches_mutex);
  
  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);
  }
  
  static char *memcg_cache_name(struct mem_cgroup *memcg, struct kmem_cache *s)
  {
          char *name;
          struct dentry *dentry;
  
          rcu_read_lock();
          dentry = rcu_dereference(memcg->css.cgroup->dentry);
          rcu_read_unlock();
  
          BUG_ON(dentry == NULL);
  
          name = kasprintf(GFP_KERNEL, "%s(%d:%s)", s->name,
                           memcg_cache_id(memcg), dentry->d_name.name);
  
          return name;
  }
  
  static struct kmem_cache *kmem_cache_dup(struct mem_cgroup *memcg,
                                           struct kmem_cache *s)
  {
          char *name;
          struct kmem_cache *new;
  
          name = memcg_cache_name(memcg, s);
          if (!name)
                  return NULL;
  
          new = kmem_cache_create_memcg(memcg, name, s->object_size, s->align,
                                        (s->flags & ~SLAB_PANIC), s->ctor, s);
  
          if (new)
                  new->allocflags |= __GFP_KMEMCG;
  
          kfree(name);
          return new;
  }
  
  /*
   * 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);
  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 = cachep->memcg_params->memcg_caches[idx];
          if (new_cachep)
                  goto out;
  
          new_cachep = kmem_cache_dup(memcg, cachep);
          if (new_cachep == NULL) {
                  new_cachep = cachep;
                  goto out;
          }
  
          mem_cgroup_get(memcg);
          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 (i = 0; i < memcg_limited_groups_array_size; i++) {
                  c = s->memcg_params->memcg_caches[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;
                  INIT_WORK(&cachep->memcg_params->destroy,
                                    kmem_cache_destroy_work_func);
                  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);
          /* Drop the reference gotten when we enqueued. */
          css_put(&cw->memcg->css);
          kfree(cw);
  }
  
  /*
   * Enqueue the creation of a per-memcg kmem_cache.
   * Called with rcu_read_lock.
   */
  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)
                  return;
  
          /* The corresponding put will be done in the workqueue. */
          if (!css_tryget(&memcg->css)) {
                  kfree(cw);
                  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));
          rcu_read_unlock();
  
          if (!memcg_can_account_kmem(memcg))
                  return cachep;
  
          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 (unlikely(cachep->memcg_params->memcg_caches[idx] == NULL)) {
                  /*
                   * 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;
          }
  
          return cachep->memcg_params->memcg_caches[idx];
  }
  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;
          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;
          int i;
  
          if (mem_cgroup_disabled())
                  return;
          for (i = 1; i < HPAGE_PMD_NR; i++) {
                  pc = head_pc + i;
                  pc->mem_cgroup = head_pc->mem_cgroup;
                  smp_wmb();/* see __commit_charge() */
                  pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
          }
  }
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  
  /**
   * 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)) {
                  /* Update mapped_file data for mem_cgroup */
                  preempt_disable();
                  __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
                  __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
                  preempt_enable();
          }
          mem_cgroup_charge_statistics(from, anon, -nr_pages);
  
          /* caller should have done css_get */
          pc->mem_cgroup = to;
          mem_cgroup_charge_statistics(to, 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;
  
          VM_BUG_ON(PageSwapCache(page));
  
          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, 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.
           */
          memcg_check_events(memcg, page);
          if (do_swap_account && ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) {
                  mem_cgroup_swap_statistics(memcg, true);
                  mem_cgroup_get(memcg);
          }
          /*
           * 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 (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,
           * mem_cgroup_get() was called in uncharge().
           */
          if (do_swap_account && swapout && memcg)
                  swap_cgroup_record(ent, css_id(&memcg->css));
  }
  #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);
                  mem_cgroup_put(memcg);
          }
          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 = css_id(&from->css);
          new_id = css_id(&to->css);
  
          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 mem_cgroup_get(to)
                   * because if the process that has been moved to @to does
                   * swap-in, the refcount of @to might be decreased to 0.
                   */
                  mem_cgroup_get(to);
                  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, 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) {
                  printk(KERN_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);
  }
  
  /*
   * 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 *cont, unsigned int event)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
          int ret;
  
          if (mem_cgroup_is_root(memcg))
                  return -EINVAL;
          css_get(&memcg->css);
          ret = mem_cgroup_force_empty(memcg);
          css_put(&memcg->css);
  
          return ret;
  }
  
  
  static u64 mem_cgroup_hierarchy_read(struct cgroup *cont, struct cftype *cft)
  {
          return mem_cgroup_from_cont(cont)->use_hierarchy;
  }
  
  static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
                                          u64 val)
  {
          int retval = 0;
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
          struct cgroup *parent = cont->parent;
          struct mem_cgroup *parent_memcg = NULL;
  
          if (parent)
                  parent_memcg = mem_cgroup_from_cont(parent);
  
          cgroup_lock();
  
          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(&cont->children))
                          memcg->use_hierarchy = val;
                  else
                          retval = -EBUSY;
          } else
                  retval = -EINVAL;
  
  out:
          cgroup_unlock();
  
          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);
          }
  
          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 *cont, struct cftype *cft,
                                 struct file *file, char __user *buf,
                                 size_t nbytes, loff_t *ppos)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
          char str[64];
          u64 val;
          int name, len;
          enum res_type type;
  
          type = MEMFILE_TYPE(cft->private);
          name = MEMFILE_ATTR(cft->private);
  
          if (!do_swap_account && type == _MEMSWAP)
                  return -EOPNOTSUPP;
  
          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 *cont, u64 val)
  {
          int ret = -EINVAL;
  #ifdef CONFIG_MEMCG_KMEM
          bool must_inc_static_branch = false;
  
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
          /*
           * 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.
           *
           * Taking the cgroup_lock is really offensive, but it is so far the only
           * way to guarantee that no children will appear. There are plenty of
           * other offenders, and they should all go away. Fine grained locking
           * is probably the way to go here. When we are fully hierarchical, we
           * can also get rid of the use_hierarchy check.
           */
          cgroup_lock();
          mutex_lock(&set_limit_mutex);
          if (!memcg->kmem_account_flags && val != RESOURCE_MAX) {
                  if (cgroup_task_count(cont) || (memcg->use_hierarchy &&
                                                  !list_empty(&cont->children))) {
                          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, RESOURCE_MAX);
                          goto out;
                  }
                  must_inc_static_branch = true;
                  /*
                   * kmem charges can outlive the cgroup. In the case of slab
                   * pages, for instance, a page contain objects from various
                   * processes, so it is unfeasible to migrate them away. We
                   * need to reference count the memcg because of that.
                   */
                  mem_cgroup_get(memcg);
          } else
                  ret = res_counter_set_limit(&memcg->kmem, val);
  out:
          mutex_unlock(&set_limit_mutex);
          cgroup_unlock();
  
          /*
           * We are by now familiar with the fact that we can't inc the static
           * branch inside cgroup_lock. See disarm functions for details. A
           * worker here is overkill, but also wrong: After the limit is set, we
           * must start accounting right away. Since this operation can't fail,
           * we can safely defer it to here - no rollback will be needed.
           *
           * The boolean used to control this is also safe, because
           * KMEM_ACCOUNTED_ACTIVATED guarantees that only one process will be
           * able to set it to true;
           */
          if (must_inc_static_branch) {
                  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);
          }
  
  #endif
          return ret;
  }
  
  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;
  #ifdef CONFIG_MEMCG_KMEM
          /*
           * 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;
  
          /*
           * destroy(), called if we fail, will issue static_key_slow_inc() and
           * mem_cgroup_put() if kmem is enabled. We have to either call them
           * unconditionally, or clear the KMEM_ACTIVE flag. I personally find
           * this more consistent, since it always leads to the same destroy path
           */
          mem_cgroup_get(memcg);
          static_key_slow_inc(&memcg_kmem_enabled_key);
  
          mutex_lock(&set_limit_mutex);
          ret = memcg_update_cache_sizes(memcg);
          mutex_unlock(&set_limit_mutex);
  #endif
  out:
          return ret;
  }
  
  /*
   * The user of this function is...
   * RES_LIMIT.
   */
  static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
                              const char *buffer)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
          enum res_type type;
          int name;
          unsigned long long val;
          int ret;
  
          type = MEMFILE_TYPE(cft->private);
          name = MEMFILE_ATTR(cft->private);
  
          if (!do_swap_account && type == _MEMSWAP)
                  return -EOPNOTSUPP;
  
          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(cont, 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)
  {
          struct cgroup *cgroup;
          unsigned long long min_limit, min_memsw_limit, tmp;
  
          min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
          min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
          cgroup = memcg->css.cgroup;
          if (!memcg->use_hierarchy)
                  goto out;
  
          while (cgroup->parent) {
                  cgroup = cgroup->parent;
                  memcg = mem_cgroup_from_cont(cgroup);
                  if (!memcg->use_hierarchy)
                          break;
                  tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
                  min_limit = min(min_limit, tmp);
                  tmp = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
                  min_memsw_limit = min(min_memsw_limit, tmp);
          }
  out:
          *mem_limit = min_limit;
          *memsw_limit = min_memsw_limit;
  }
  
  static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
          int name;
          enum res_type type;
  
          type = MEMFILE_TYPE(event);
          name = MEMFILE_ATTR(event);
  
          if (!do_swap_account && type == _MEMSWAP)
                  return -EOPNOTSUPP;
  
          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 *cgrp,
                                          struct cftype *cft)
  {
          return mem_cgroup_from_cont(cgrp)->move_charge_at_immigrate;
  }
  
  #ifdef CONFIG_MMU
  static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
                                          struct cftype *cft, u64 val)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
  
          if (val >= (1 << NR_MOVE_TYPE))
                  return -EINVAL;
          /*
           * We check this value several times in both in can_attach() and
           * attach(), so we need cgroup lock to prevent this value from being
           * inconsistent.
           */
          cgroup_lock();
          memcg->move_charge_at_immigrate = val;
          cgroup_unlock();
  
          return 0;
  }
  #else
  static int mem_cgroup_move_charge_write(struct cgroup *cgrp,
                                          struct cftype *cft, u64 val)
  {
          return -ENOSYS;
  }
  #endif
  
  #ifdef CONFIG_NUMA
  static int memcg_numa_stat_show(struct cgroup *cont, struct cftype *cft,
                                        struct seq_file *m)
  {
          int nid;
          unsigned long total_nr, file_nr, anon_nr, unevictable_nr;
          unsigned long node_nr;
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
  
          total_nr = mem_cgroup_nr_lru_pages(memcg, LRU_ALL);
          seq_printf(m, "total=%lu", total_nr);
          for_each_node_state(nid, N_MEMORY) {
                  node_nr = mem_cgroup_node_nr_lru_pages(memcg, nid, LRU_ALL);
                  seq_printf(m, " N%d=%lu", nid, node_nr);
          }
          seq_putc(m, '\n');
  
          file_nr = mem_cgroup_nr_lru_pages(memcg, LRU_ALL_FILE);
          seq_printf(m, "file=%lu", file_nr);
          for_each_node_state(nid, N_MEMORY) {
                  node_nr = mem_cgroup_node_nr_lru_pages(memcg, nid,
                                  LRU_ALL_FILE);
                  seq_printf(m, " N%d=%lu", nid, node_nr);
          }
          seq_putc(m, '\n');
  
          anon_nr = mem_cgroup_nr_lru_pages(memcg, LRU_ALL_ANON);
          seq_printf(m, "anon=%lu", anon_nr);
          for_each_node_state(nid, N_MEMORY) {
                  node_nr = mem_cgroup_node_nr_lru_pages(memcg, nid,
                                  LRU_ALL_ANON);
                  seq_printf(m, " N%d=%lu", nid, node_nr);
          }
          seq_putc(m, '\n');
  
          unevictable_nr = mem_cgroup_nr_lru_pages(memcg, BIT(LRU_UNEVICTABLE));
          seq_printf(m, "unevictable=%lu", unevictable_nr);
          for_each_node_state(nid, N_MEMORY) {
                  node_nr = mem_cgroup_node_nr_lru_pages(memcg, nid,
                                  BIT(LRU_UNEVICTABLE));
                  seq_printf(m, " N%d=%lu", nid, node_nr);
          }
          seq_putc(m, '\n');
          return 0;
  }
  #endif /* CONFIG_NUMA */
  
  static const char * const mem_cgroup_lru_names[] = {
          "inactive_anon",
          "active_anon",
          "inactive_file",
          "active_file",
          "unevictable",
  };
  
  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 *cont, struct cftype *cft,
                                   struct seq_file *m)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
          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 *cgrp, struct cftype *cft)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
  
          return mem_cgroup_swappiness(memcg);
  }
  
  static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
                                         u64 val)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
          struct mem_cgroup *parent;
  
          if (val > 100)
                  return -EINVAL;
  
          if (cgrp->parent == NULL)
                  return -EINVAL;
  
          parent = mem_cgroup_from_cont(cgrp->parent);
  
          cgroup_lock();
  
          /* If under hierarchy, only empty-root can set this value */
          if ((parent->use_hierarchy) ||
              (memcg->use_hierarchy && !list_empty(&cgrp->children))) {
                  cgroup_unlock();
                  return -EINVAL;
          }
  
          memcg->swappiness = val;
  
          cgroup_unlock();
  
          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;
  
          return _a->threshold - _b->threshold;
  }
  
  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 *cgrp,
          struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
          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 *cgrp,
          struct cftype *cft, struct eventfd_ctx *eventfd)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
          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 *cgrp,
          struct cftype *cft, struct eventfd_ctx *eventfd, const char *args)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
          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 *cgrp,
          struct cftype *cft, struct eventfd_ctx *eventfd)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
          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 *cgrp,
          struct cftype *cft,  struct cgroup_map_cb *cb)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
  
          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 *cgrp,
          struct cftype *cft, u64 val)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
          struct mem_cgroup *parent;
  
          /* cannot set to root cgroup and only 0 and 1 are allowed */
          if (!cgrp->parent || !((val == 0) || (val == 1)))
                  return -EINVAL;
  
          parent = mem_cgroup_from_cont(cgrp->parent);
  
          cgroup_lock();
          /* oom-kill-disable is a flag for subhierarchy. */
          if ((parent->use_hierarchy) ||
              (memcg->use_hierarchy && !list_empty(&cgrp->children))) {
                  cgroup_unlock();
                  return -EINVAL;
          }
          memcg->oom_kill_disable = val;
          if (!val)
                  memcg_oom_recover(memcg);
          cgroup_unlock();
          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 kmem_cgroup_destroy(struct mem_cgroup *memcg)
  {
          mem_cgroup_sockets_destroy(memcg);
  
          memcg_kmem_mark_dead(memcg);
  
          if (res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0)
                  return;
  
          /*
           * Charges already down to 0, undo mem_cgroup_get() done in the charge
           * path here, being careful not to race with memcg_uncharge_kmem: it is
           * possible that the charges went down to 0 between mark_dead and the
           * res_counter read, so in that case, we don't need the put
           */
          if (memcg_kmem_test_and_clear_dead(memcg))
                  mem_cgroup_put(memcg);
  }
  #else
  static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
  {
          return 0;
  }
  
  static void kmem_cgroup_destroy(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",
                  .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),
          },
  #ifdef CONFIG_NUMA
          {
                  .name = "numa_stat",
                  .read_seq_string = memcg_numa_stat_show,
          },
  #endif
  #ifdef CONFIG_MEMCG_SWAP
          {
                  .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,
          },
  #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 */
  };
  
  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->info.nodeinfo[node] = pn;
          return 0;
  }
  
  static void free_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
  {
          kfree(memcg->info.nodeinfo[node]);
  }
  
  static struct mem_cgroup *mem_cgroup_alloc(void)
  {
          struct mem_cgroup *memcg;
          int size = sizeof(struct mem_cgroup);
  
          /* Can be very big if MAX_NUMNODES 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;
          int size = sizeof(struct mem_cgroup);
  
          mem_cgroup_remove_from_trees(memcg);
          free_css_id(&mem_cgroup_subsys, &memcg->css);
  
          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);
  }
  
  
  /*
   * Helpers for freeing a kmalloc()ed/vzalloc()ed mem_cgroup by RCU,
   * but in process context.  The work_freeing structure is overlaid
   * on the rcu_freeing structure, which itself is overlaid on memsw.
   */
  static void free_work(struct work_struct *work)
  {
          struct mem_cgroup *memcg;
  
          memcg = container_of(work, struct mem_cgroup, work_freeing);
          __mem_cgroup_free(memcg);
  }
  
  static void free_rcu(struct rcu_head *rcu_head)
  {
          struct mem_cgroup *memcg;
  
          memcg = container_of(rcu_head, struct mem_cgroup, rcu_freeing);
          INIT_WORK(&memcg->work_freeing, free_work);
          schedule_work(&memcg->work_freeing);
  }
  
  static void mem_cgroup_get(struct mem_cgroup *memcg)
  {
          atomic_inc(&memcg->refcnt);
  }
  
  static void __mem_cgroup_put(struct mem_cgroup *memcg, int count)
  {
          if (atomic_sub_and_test(count, &memcg->refcnt)) {
                  struct mem_cgroup *parent = parent_mem_cgroup(memcg);
                  call_rcu(&memcg->rcu_freeing, free_rcu);
                  if (parent)
                          mem_cgroup_put(parent);
          }
  }
  
  static void mem_cgroup_put(struct mem_cgroup *memcg)
  {
          __mem_cgroup_put(memcg, 1);
  }
  
  /*
   * 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);
  
  #ifdef CONFIG_MEMCG_SWAP
  static void __init enable_swap_cgroup(void)
  {
          if (!mem_cgroup_disabled() && really_do_swap_account)
                  do_swap_account = 1;
  }
  #else
  static void __init enable_swap_cgroup(void)
  {
  }
  #endif
  
  static int 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);
                  if (!rtpn)
                          goto err_cleanup;
  
                  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);
                  }
          }
          return 0;
  
  err_cleanup:
          for_each_node(node) {
                  if (!soft_limit_tree.rb_tree_per_node[node])
                          break;
                  kfree(soft_limit_tree.rb_tree_per_node[node]);
                  soft_limit_tree.rb_tree_per_node[node] = NULL;
          }
          return 1;
  
  }
  
  static struct cgroup_subsys_state * __ref
  mem_cgroup_css_alloc(struct cgroup *cont)
  {
          struct mem_cgroup *memcg, *parent;
          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 (cont->parent == NULL) {
                  int cpu;
                  enable_swap_cgroup();
                  parent = NULL;
                  if (mem_cgroup_soft_limit_tree_init())
                          goto free_out;
                  root_mem_cgroup = memcg;
                  for_each_possible_cpu(cpu) {
                          struct memcg_stock_pcp *stock =
                                                  &per_cpu(memcg_stock, cpu);
                          INIT_WORK(&stock->work, drain_local_stock);
                  }
          } else {
                  parent = mem_cgroup_from_cont(cont->parent);
                  memcg->use_hierarchy = parent->use_hierarchy;
                  memcg->oom_kill_disable = parent->oom_kill_disable;
          }
  
          if (parent && parent->use_hierarchy) {
                  res_counter_init(&memcg->res, &parent->res);
                  res_counter_init(&memcg->memsw, &parent->memsw);
                  res_counter_init(&memcg->kmem, &parent->kmem);
  
                  /*
                   * We increment refcnt of the parent to ensure that we can
                   * safely access it on res_counter_charge/uncharge.
                   * This refcnt will be decremented when freeing this
                   * mem_cgroup(see mem_cgroup_put).
                   */
                  mem_cgroup_get(parent);
          } else {
                  res_counter_init(&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 && parent != root_mem_cgroup)
                          mem_cgroup_subsys.broken_hierarchy = true;
          }
          memcg->last_scanned_node = MAX_NUMNODES;
          INIT_LIST_HEAD(&memcg->oom_notify);
  
          if (parent)
                  memcg->swappiness = mem_cgroup_swappiness(parent);
          atomic_set(&memcg->refcnt, 1);
          memcg->move_charge_at_immigrate = 0;
          mutex_init(&memcg->thresholds_lock);
          spin_lock_init(&memcg->move_lock);
  
          error = memcg_init_kmem(memcg, &mem_cgroup_subsys);
          if (error) {
                  /*
                   * We call put now because our (and parent's) refcnts
                   * are already in place. mem_cgroup_put() will internally
                   * call __mem_cgroup_free, so return directly
                   */
                  mem_cgroup_put(memcg);
                  return ERR_PTR(error);
          }
          return &memcg->css;
  free_out:
          __mem_cgroup_free(memcg);
          return ERR_PTR(error);
  }
  
  static void mem_cgroup_css_offline(struct cgroup *cont)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
  
          mem_cgroup_reparent_charges(memcg);
          mem_cgroup_destroy_all_caches(memcg);
  }
  
  static void mem_cgroup_css_free(struct cgroup *cont)
  {
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
  
          kmem_cgroup_destroy(memcg);
  
          mem_cgroup_put(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;
          swp_entry_t     ent;
  };
  
  enum mc_target_type {
          MC_TARGET_NONE = 0,
          MC_TARGET_PAGE,
          MC_TARGET_SWAP,
  };
  
  static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
                                                  unsigned long addr, pte_t ptent)
  {
          struct page *page = vm_normal_page(vma, addr, ptent);
  
          if (!page || !page_mapped(page))
                  return NULL;
          if (PageAnon(page)) {
                  /* we don't move shared anon */
                  if (!move_anon())
                          return NULL;
          } else if (!move_file())
                  /* we ignore mapcount for file pages */
                  return NULL;
          if (!get_page_unless_zero(page))
                  return NULL;
  
          return page;
  }
  
  #ifdef CONFIG_SWAP
  static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
                          unsigned long addr, pte_t ptent, swp_entry_t *entry)
  {
          struct page *page = NULL;
          swp_entry_t ent = pte_to_swp_entry(ptent);
  
          if (!move_anon() || non_swap_entry(ent))
                  return NULL;
          /*
           * Because lookup_swap_cache() updates some statistics counter,
           * we call find_get_page() with swapper_space directly.
           */
          page = find_get_page(&swapper_space, ent.val);
          if (do_swap_account)
                  entry->val = ent.val;
  
          return page;
  }
  #else
  static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
                          unsigned long addr, pte_t ptent, swp_entry_t *entry)
  {
          return NULL;
  }
  #endif
  
  static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
                          unsigned long addr, pte_t ptent, swp_entry_t *entry)
  {
          struct page *page = NULL;
          struct address_space *mapping;
          pgoff_t pgoff;
  
          if (!vma->vm_file) /* anonymous vma */
                  return NULL;
          if (!move_file())
                  return NULL;
  
          mapping = vma->vm_file->f_mapping;
          if (pte_none(ptent))
                  pgoff = linear_page_index(vma, addr);
          else /* pte_file(ptent) is true */
                  pgoff = pte_to_pgoff(ptent);
  
          /* page is moved even if it's not RSS of this task(page-faulted). */
          page = find_get_page(mapping, pgoff);
  
  #ifdef CONFIG_SWAP
          /* shmem/tmpfs may report page out on swap: account for that too. */
          if (radix_tree_exceptional_entry(page)) {
                  swp_entry_t swap = radix_to_swp_entry(page);
                  if (do_swap_account)
                          *entry = swap;
                  page = find_get_page(&swapper_space, swap.val);
          }
  #endif
          return page;
  }
  
  static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
                  unsigned long addr, pte_t ptent, union mc_target *target)
  {
          struct page *page = NULL;
          struct page_cgroup *pc;
          enum mc_target_type ret = MC_TARGET_NONE;
          swp_entry_t ent = { .val = 0 };
  
          if (pte_present(ptent))
                  page = mc_handle_present_pte(vma, addr, ptent);
          else if (is_swap_pte(ptent))
                  page = mc_handle_swap_pte(vma, addr, ptent, &ent);
          else if (pte_none(ptent) || pte_file(ptent))
                  page = mc_handle_file_pte(vma, addr, ptent, &ent);
  
          if (!page && !ent.val)
                  return ret;
          if (page) {
                  pc = lookup_page_cgroup(page);
                  /*
                   * Do only loose check w/o page_cgroup lock.
                   * mem_cgroup_move_account() checks the pc is valid or not under
                   * the lock.
                   */
                  if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
                          ret = MC_TARGET_PAGE;
                          if (target)
                                  target->page = page;
                  }
                  if (!ret || !target)
                          put_page(page);
          }
          /* There is a swap entry and a page doesn't exist or isn't charged */
          if (ent.val && !ret &&
                          css_id(&mc.from->css) == lookup_swap_cgroup_id(ent)) {
                  ret = MC_TARGET_SWAP;
                  if (target)
                          target->ent = ent;
          }
          return ret;
  }
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  /*
   * We don't consider swapping or file mapped pages because THP does not
   * support them for now.
   * Caller should make sure that pmd_trans_huge(pmd) is true.
   */
  static enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma,
                  unsigned long addr, pmd_t pmd, union mc_target *target)
  {
          struct page *page = NULL;
          struct page_cgroup *pc;
          enum mc_target_type ret = MC_TARGET_NONE;
  
          page = pmd_page(pmd);
          VM_BUG_ON(!page || !PageHead(page));
          if (!move_anon())
                  return ret;
          pc = lookup_page_cgroup(page);
          if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
                  ret = MC_TARGET_PAGE;
                  if (target) {
                          get_page(page);
                          target->page = page;
                  }
          }
          return ret;
  }
  #else
  static inline enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma,
                  unsigned long addr, pmd_t pmd, union mc_target *target)
  {
          return MC_TARGET_NONE;
  }
  #endif
  
  static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
                                          unsigned long addr, unsigned long end,
                                          struct mm_walk *walk)
  {
          struct vm_area_struct *vma = walk->private;
          pte_t *pte;
          spinlock_t *ptl;
  
          if (pmd_trans_huge_lock(pmd, vma) == 1) {
                  if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
                          mc.precharge += HPAGE_PMD_NR;
                  spin_unlock(&vma->vm_mm->page_table_lock);
                  return 0;
          }
  
          if (pmd_trans_unstable(pmd))
                  return 0;
          pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
          for (; addr != end; pte++, addr += PAGE_SIZE)
                  if (get_mctgt_type(vma, addr, *pte, NULL))
                          mc.precharge++; /* increment precharge temporarily */
          pte_unmap_unlock(pte - 1, ptl);
          cond_resched();
  
          return 0;
  }
  
  static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
  {
          unsigned long precharge;
          struct vm_area_struct *vma;
  
          down_read(&mm->mmap_sem);
          for (vma = mm->mmap; vma; vma = vma->vm_next) {
                  struct mm_walk mem_cgroup_count_precharge_walk = {
                          .pmd_entry = mem_cgroup_count_precharge_pte_range,
                          .mm = mm,
                          .private = vma,
                  };
                  if (is_vm_hugetlb_page(vma))
                          continue;
                  walk_page_range(vma->vm_start, vma->vm_end,
                                          &mem_cgroup_count_precharge_walk);
          }
          up_read(&mm->mmap_sem);
  
          precharge = mc.precharge;
          mc.precharge = 0;
  
          return precharge;
  }
  
  static int mem_cgroup_precharge_mc(struct mm_struct *mm)
  {
          unsigned long precharge = mem_cgroup_count_precharge(mm);
  
          VM_BUG_ON(mc.moving_task);
          mc.moving_task = current;
          return mem_cgroup_do_precharge(precharge);
  }
  
  /* cancels all extra charges on mc.from and mc.to, and wakes up all waiters. */
  static void __mem_cgroup_clear_mc(void)
  {
          struct mem_cgroup *from = mc.from;
          struct mem_cgroup *to = mc.to;
  
          /* we must uncharge all the leftover precharges from mc.to */
          if (mc.precharge) {
                  __mem_cgroup_cancel_charge(mc.to, mc.precharge);
                  mc.precharge = 0;
          }
          /*
           * we didn't uncharge from mc.from at mem_cgroup_move_account(), so
           * we must uncharge here.
           */
          if (mc.moved_charge) {
                  __mem_cgroup_cancel_charge(mc.from, mc.moved_charge);
                  mc.moved_charge = 0;
          }
          /* we must fixup refcnts and charges */
          if (mc.moved_swap) {
                  /* uncharge swap account from the old cgroup */
                  if (!mem_cgroup_is_root(mc.from))
                          res_counter_uncharge(&mc.from->memsw,
                                                  PAGE_SIZE * mc.moved_swap);
                  __mem_cgroup_put(mc.from, mc.moved_swap);
  
                  if (!mem_cgroup_is_root(mc.to)) {
                          /*
                           * we charged both to->res and to->memsw, so we should
                           * uncharge to->res.
                           */
                          res_counter_uncharge(&mc.to->res,
                                                  PAGE_SIZE * mc.moved_swap);
                  }
                  /* we've already done mem_cgroup_get(mc.to) */
                  mc.moved_swap = 0;
          }
          memcg_oom_recover(from);
          memcg_oom_recover(to);
          wake_up_all(&mc.waitq);
  }
  
  static void mem_cgroup_clear_mc(void)
  {
          struct mem_cgroup *from = mc.from;
  
          /*
           * we must clear moving_task before waking up waiters at the end of
           * task migration.
           */
          mc.moving_task = NULL;
          __mem_cgroup_clear_mc();
          spin_lock(&mc.lock);
          mc.from = NULL;
          mc.to = NULL;
          spin_unlock(&mc.lock);
          mem_cgroup_end_move(from);
  }
  
  static int mem_cgroup_can_attach(struct cgroup *cgroup,
                                   struct cgroup_taskset *tset)
  {
          struct task_struct *p = cgroup_taskset_first(tset);
          int ret = 0;
          struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
  
          if (memcg->move_charge_at_immigrate) {
                  struct mm_struct *mm;
                  struct mem_cgroup *from = mem_cgroup_from_task(p);
  
                  VM_BUG_ON(from == memcg);
  
                  mm = get_task_mm(p);
                  if (!mm)
                          return 0;
                  /* We move charges only when we move a owner of the mm */
                  if (mm->owner == p) {
                          VM_BUG_ON(mc.from);
                          VM_BUG_ON(mc.to);
                          VM_BUG_ON(mc.precharge);
                          VM_BUG_ON(mc.moved_charge);
                          VM_BUG_ON(mc.moved_swap);
                          mem_cgroup_start_move(from);
                          spin_lock(&mc.lock);
                          mc.from = from;
                          mc.to = memcg;
                          spin_unlock(&mc.lock);
                          /* We set mc.moving_task later */
  
                          ret = mem_cgroup_precharge_mc(mm);
                          if (ret)
                                  mem_cgroup_clear_mc();
                  }
                  mmput(mm);
          }
          return ret;
  }
  
  static void mem_cgroup_cancel_attach(struct cgroup *cgroup,
                                       struct cgroup_taskset *tset)
  {
          mem_cgroup_clear_mc();
  }
  
  static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
                                  unsigned long addr, unsigned long end,
                                  struct mm_walk *walk)
  {
          int ret = 0;
          struct vm_area_struct *vma = walk->private;
          pte_t *pte;
          spinlock_t *ptl;
          enum mc_target_type target_type;
          union mc_target target;
          struct page *page;
          struct page_cgroup *pc;
  
          /*
           * We don't take compound_lock() here but no race with splitting thp
           * happens because:
           *  - if pmd_trans_huge_lock() returns 1, the relevant thp is not
           *    under splitting, which means there's no concurrent thp split,
           *  - if another thread runs into split_huge_page() just after we
           *    entered this if-block, the thread must wait for page table lock
           *    to be unlocked in __split_huge_page_splitting(), where the main
           *    part of thp split is not executed yet.
           */
          if (pmd_trans_huge_lock(pmd, vma) == 1) {
                  if (mc.precharge < HPAGE_PMD_NR) {
                          spin_unlock(&vma->vm_mm->page_table_lock);
                          return 0;
                  }
                  target_type = get_mctgt_type_thp(vma, addr, *pmd, &target);
                  if (target_type == MC_TARGET_PAGE) {
                          page = target.page;
                          if (!isolate_lru_page(page)) {
                                  pc = lookup_page_cgroup(page);
                                  if (!mem_cgroup_move_account(page, HPAGE_PMD_NR,
                                                          pc, mc.from, mc.to)) {
                                          mc.precharge -= HPAGE_PMD_NR;
                                          mc.moved_charge += HPAGE_PMD_NR;
                                  }
                                  putback_lru_page(page);
                          }
                          put_page(page);
                  }
                  spin_unlock(&vma->vm_mm->page_table_lock);
                  return 0;
          }
  
          if (pmd_trans_unstable(pmd))
                  return 0;
  retry:
          pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
          for (; addr != end; addr += PAGE_SIZE) {
                  pte_t ptent = *(pte++);
                  swp_entry_t ent;
  
                  if (!mc.precharge)
                          break;
  
                  switch (get_mctgt_type(vma, addr, ptent, &target)) {
                  case MC_TARGET_PAGE:
                          page = target.page;
                          if (isolate_lru_page(page))
                                  goto put;
                          pc = lookup_page_cgroup(page);
                          if (!mem_cgroup_move_account(page, 1, pc,
                                                       mc.from, mc.to)) {
                                  mc.precharge--;
                                  /* we uncharge from mc.from later. */
                                  mc.moved_charge++;
                          }
                          putback_lru_page(page);
  put:                    /* get_mctgt_type() gets the page */
                          put_page(page);
                          break;
                  case MC_TARGET_SWAP:
                          ent = target.ent;
                          if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to)) {
                                  mc.precharge--;
                                  /* we fixup refcnts and charges later. */
                                  mc.moved_swap++;
                          }
                          break;
                  default:
                          break;
                  }
          }
          pte_unmap_unlock(pte - 1, ptl);
          cond_resched();
  
          if (addr != end) {
                  /*
                   * We have consumed all precharges we got in can_attach().
                   * We try charge one by one, but don't do any additional
                   * charges to mc.to if we have failed in charge once in attach()
                   * phase.
                   */
                  ret = mem_cgroup_do_precharge(1);
                  if (!ret)
                          goto retry;
          }
  
          return ret;
  }
  
  static void mem_cgroup_move_charge(struct mm_struct *mm)
  {
          struct vm_area_struct *vma;
  
          lru_add_drain_all();
  retry:
          if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
                  /*
                   * Someone who are holding the mmap_sem might be waiting in
                   * waitq. So we cancel all extra charges, wake up all waiters,
                   * and retry. Because we cancel precharges, we might not be able
                   * to move enough charges, but moving charge is a best-effort
                   * feature anyway, so it wouldn't be a big problem.
                   */
                  __mem_cgroup_clear_mc();
                  cond_resched();
                  goto retry;
          }
          for (vma = mm->mmap; vma; vma = vma->vm_next) {
                  int ret;
                  struct mm_walk mem_cgroup_move_charge_walk = {
                          .pmd_entry = mem_cgroup_move_charge_pte_range,
                          .mm = mm,
                          .private = vma,
                  };
                  if (is_vm_hugetlb_page(vma))
                          continue;
                  ret = walk_page_range(vma->vm_start, vma->vm_end,
                                                  &mem_cgroup_move_charge_walk);
                  if (ret)
                          /*
                           * means we have consumed all precharges and failed in
                           * doing additional charge. Just abandon here.
                           */
                          break;
          }
          up_read(&mm->mmap_sem);
  }
  
  static void mem_cgroup_move_task(struct cgroup *cont,
                                   struct cgroup_taskset *tset)
  {
          struct task_struct *p = cgroup_taskset_first(tset);
          struct mm_struct *mm = get_task_mm(p);
  
          if (mm) {
                  if (mc.to)
                          mem_cgroup_move_charge(mm);
                  mmput(mm);
          }
          if (mc.to)
                  mem_cgroup_clear_mc();
  }
  #else   /* !CONFIG_MMU */
  static int mem_cgroup_can_attach(struct cgroup *cgroup,
                                   struct cgroup_taskset *tset)
  {
          return 0;
  }
  static void mem_cgroup_cancel_attach(struct cgroup *cgroup,
                                       struct cgroup_taskset *tset)
  {
  }
  static void mem_cgroup_move_task(struct cgroup *cont,
                                   struct cgroup_taskset *tset)
  {
  }
  #endif
  
  struct cgroup_subsys mem_cgroup_subsys = {
          .name = "memory",
          .subsys_id = mem_cgroup_subsys_id,
          .css_alloc = mem_cgroup_css_alloc,
          .css_offline = mem_cgroup_css_offline,
          .css_free = mem_cgroup_css_free,
          .can_attach = mem_cgroup_can_attach,
          .cancel_attach = mem_cgroup_cancel_attach,
          .attach = mem_cgroup_move_task,
          .base_cftypes = mem_cgroup_files,
          .early_init = 0,
          .use_id = 1,
  };
  
  /*
   * The rest of init is performed during ->css_alloc() for root css which
   * happens before initcalls.  hotcpu_notifier() can't be done together as
   * it would introduce circular locking by adding cgroup_lock -> cpu hotplug
   * dependency.  Do it from a subsys_initcall().
   */
  static int __init mem_cgroup_init(void)
  {
          hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
          return 0;
  }
  subsys_initcall(mem_cgroup_init);
  
  #ifdef CONFIG_MEMCG_SWAP
  static int __init enable_swap_account(char *s)
  {
          /* consider enabled if no parameter or 1 is given */
          if (!strcmp(s, "1"))
                  really_do_swap_account = 1;
          else if (!strcmp(s, ""))
                  really_do_swap_account = 0;
          return 1;
  }
  __setup("swapaccount=", enable_swap_account);
  
  #endif