memcontrol.c

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/* memcontrol.c - Memory Controller
 *
 * Copyright IBM Corporation, 2007
 * Author Balbir Singh <[email protected]>
 *
 * Copyright 2007 OpenVZ SWsoft Inc
 * Author: Pavel Emelianov <[email protected]>
 *
 * Memory thresholds
 * Copyright (C) 2009 Nokia Corporation
 * Author: Kirill A. Shutemov
 *
 * 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;
#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;
    };

    /*
     * 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;

    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
};

/* 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 */
#define _MEM            (0)
#define _MEMSWAP        (1)
#define _OOM_TYPE       (2)
#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

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_HIGH_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;
}

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;
}

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;

    if (!mm)
        return;

    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);

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.
 */

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;
}

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)

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);
}

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));
}

/*
 * 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;
}

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;
}

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_HIGH_MEMORY];

    for_each_node_mask(nid, node_states[N_HIGH_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_HIGH_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);

/*
 * Try to consume stocked charge on this cpu. If success, one page is consumed
 * from local stock and true is returned. If the stock is 0 or charges from a
 * cgroup which is not current target, returns false. This stock will be
 * refilled.
 */
static bool consume_stock(struct mem_cgroup *memcg)
{
    struct memcg_stock_pcp *stock;
    bool ret = true;

    stock = &get_cpu_var(memcg_stock);
    if (memcg == stock->cached && stock->nr_pages)
        stock->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, 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);
    /*
     * nr_pages can be either a huge page (HPAGE_PMD_NR), a batch
     * of regular pages (CHARGE_BATCH), or a single regular page (1).
     *
     * Never reclaim on behalf of optional batching, retry with a
     * single page instead.
     */
    if (nr_pages == CHARGE_BATCH)
        return CHARGE_RETRY;

    if (!(gfp_mask & __GFP_WAIT))
        return CHARGE_WOULDBLOCK;

    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 && 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;
        VM_BUG_ON(css_is_removed(&memcg->css));
        if (mem_cgroup_is_root(memcg))
            goto done;
        if (nr_pages == 1 && consume_stock(memcg))
            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 (nr_pages == 1 && consume_stock(memcg)) {
            /*
             * 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, 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 must check css_is_removed() or some if
 * it's concern. (dropping refcnt from swap can be called against removed
 * memcg.)
 */
static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
{
    struct cgroup_subsys_state *css;

    /* ID 0 is unused ID */
    if (!id)
        return NULL;
    css = css_lookup(&mem_cgroup_subsys, id);
    if (!css)
        return NULL;
    return 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);
}

#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 */

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);
    /*
     * We charges against "to" which may not have any tasks. Then, "to"
     * can be under rmdir(). But in current implementation, caller of
     * this function is just force_empty() and move charge, so it's
     * guaranteed that "to" is never removed. So, we don't check rmdir
     * status here.
     */
    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;
}

/*
 * move charges to its parent.
 */

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;

    /* Is ROOT ? */
    if (mem_cgroup_is_root(child))
        return -EINVAL;

    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)
        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;
    cgroup_exclude_rmdir(&memcg->css);

    __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);
    }
    /*
     * At swapin, we may charge account against cgroup which has no tasks.
     * So, rmdir()->pre_destroy() can be called while we do this charge.
     * In that case, we need to call pre_destroy() again. check it here.
     */
    cgroup_release_and_wakeup_rmdir(&memcg->css);
}

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();
}

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;
    struct page_cgroup *pc;
    enum charge_type ctype;

    *memcgp = NULL;

    VM_BUG_ON(PageTransHuge(page));
    if (mem_cgroup_disabled())
        return;

    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, 1, 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;
    /* blocks rmdir() */
    cgroup_exclude_rmdir(&memcg->css);
    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 migration, we may charge account against cgroup which has no
     * tasks.
     * So, rmdir()->pre_destroy() can be called while we do this charge.
     * In that case, we need to call pre_destroy() again. check it here.
     */
    cgroup_release_and_wakeup_rmdir(&memcg->css);
}

/*
 * 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 DEFINE_MUTEX(set_limit_mutex);

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;
}

/*
 * Traverse a specified page_cgroup list and try to drop them all.  This doesn't
 * reclaim the pages page themselves - it just removes the page_cgroups.
 * Returns true if some page_cgroups were not freed, indicating that the caller
 * must retry this operation.
 */
static bool mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
                int node, int zid, enum lru_list lru)
{
    struct lruvec *lruvec;
    unsigned long flags, loop;
    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];

    loop = mem_cgroup_get_lru_size(lruvec, lru);
    /* give some margin against EBUSY etc...*/
    loop += 256;
    busy = NULL;
    while (loop--) {
        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;
    }
    return !list_empty(list);
}

/*
 * make mem_cgroup's charge to be 0 if there is no task.
 * This enables deleting this mem_cgroup.
 */
static int mem_cgroup_force_empty(struct mem_cgroup *memcg, bool free_all)
{
    int ret;
    int node, zid, shrink;
    int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
    struct cgroup *cgrp = memcg->css.cgroup;

    css_get(&memcg->css);

    shrink = 0;
    /* should free all ? */
    if (free_all)
        goto try_to_free;
move_account:
    do {
        ret = -EBUSY;
        if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
            goto out;
        /* This is for making all *used* pages to be on LRU. */
        lru_add_drain_all();
        drain_all_stock_sync(memcg);
        ret = 0;
        mem_cgroup_start_move(memcg);
        for_each_node_state(node, N_HIGH_MEMORY) {
            for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
                enum lru_list lru;
                for_each_lru(lru) {
                    ret = mem_cgroup_force_empty_list(memcg,
                            node, zid, lru);
                    if (ret)
                        break;
                }
            }
            if (ret)
                break;
        }
        mem_cgroup_end_move(memcg);
        memcg_oom_recover(memcg);
        cond_resched();
    /* "ret" should also be checked to ensure all lists are empty. */
    } while (res_counter_read_u64(&memcg->res, RES_USAGE) > 0 || ret);
out:
    css_put(&memcg->css);
    return ret;

try_to_free:
    /* returns EBUSY if there is a task or if we come here twice. */
    if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children) || shrink) {
        ret = -EBUSY;
        goto out;
    }
    /* we call try-to-free pages for make this cgroup empty */
    lru_add_drain_all();
    /* try to free all pages in this cgroup */
    shrink = 1;
    while (nr_retries && res_counter_read_u64(&memcg->res, RES_USAGE) > 0) {
        int progress;

        if (signal_pending(current)) {
            ret = -EINTR;
            goto out;
        }
        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();
    /* try move_account...there may be some *locked* pages. */
    goto move_account;
}

static int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
{
    return mem_cgroup_force_empty(mem_cgroup_from_cont(cont), true);
}


static u64 mem_cgroup_hierarchy_read(struct cgroup *cont, struct cftype *cft)
{
    return mem_cgroup_from_cont(cont)->use_hierarchy;
}

static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
                    u64 val)
{
    int retval = 0;
    struct mem_cgroup *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 type, name, len;

    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;
    default:
        BUG();
    }

    len = scnprintf(str, sizeof(str), "%llu\n", (unsigned long long)val);
    return simple_read_from_buffer(buf, nbytes, ppos, str, len);
}
/*
 * The user of this function is...
 * RES_LIMIT.
 */
static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
                const char *buffer)
{
    struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
    int type, name;
    unsigned long long val;
    int ret;

    type = MEMFILE_TYPE(cft->private);
    name = MEMFILE_ATTR(cft->private);

    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
            ret = mem_cgroup_resize_memsw_limit(memcg, val);
        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 type, name;

    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
            res_counter_reset_max(&memcg->memsw);
        break;
    case RES_FAILCNT:
        if (type == _MEM)
            res_counter_reset_failcnt(&memcg->res);
        else
            res_counter_reset_failcnt(&memcg->memsw);
        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_HIGH_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_HIGH_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_HIGH_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_HIGH_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;
    int 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;
    int 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;
    int 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;
    int 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)
{
    return mem_cgroup_sockets_init(memcg, ss);
};

static void kmem_cgroup_destroy(struct mem_cgroup *memcg)
{
    mem_cgroup_sockets_destroy(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
    { },    /* 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;
}

/*
 * 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;
    int size = sizeof(struct mem_cgroup);

    memcg = container_of(work, struct mem_cgroup, work_freeing);
    /*
     * 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_sock_keys(memcg);
    if (size < PAGE_SIZE)
        kfree(memcg);
    else
        vfree(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);
}

/*
 * 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;

    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);
    call_rcu(&memcg->rcu_freeing, free_rcu);
}

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);
        __mem_cgroup_free(memcg);
        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_create(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);
        }
        hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
    } 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);
        /*
         * 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);
        /*
         * 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 int mem_cgroup_pre_destroy(struct cgroup *cont)
{
    struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);

    return mem_cgroup_force_empty(memcg, false);
}

static void mem_cgroup_destroy(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;
}

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,
    .create = mem_cgroup_create,
    .pre_destroy = mem_cgroup_pre_destroy,
    .destroy = mem_cgroup_destroy,
    .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,
    .__DEPRECATED_clear_css_refs = true,
};

#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, "0"))
        really_do_swap_account = 0;
    return 1;
}
__setup("swapaccount=", enable_swap_account);

#endif