/* memcontrol.c - Memory Controller
 *
 * Copyright IBM Corporation, 2007
 * Author Balbir Singh <balbir@linux.vnet.ibm.com>
 *
 * Copyright 2007 OpenVZ SWsoft Inc
 * Author: Pavel Emelianov <xemul@openvz.org>
 *
 * Memory thresholds
 * Copyright (C) 2009 Nokia Corporation
 * Author: Kirill A. Shutemov
 *
 * 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/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
struct mem_cgroup *root_mem_cgroup __read_mostly;

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
/* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
int do_swap_account __read_mostly;

/* for remember boot option*/
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_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_SWAPOUT, /* # of pages, swapped out */
        MEM_CGROUP_STAT_DATA, /* end of data requires synchronization */
        MEM_CGROUP_ON_MOVE,     /* someone is moving account between groups */
        MEM_CGROUP_STAT_NSTATS,
};

enum mem_cgroup_events_index {
        MEM_CGROUP_EVENTS_PGPGIN,       /* # of pages paged in */
        MEM_CGROUP_EVENTS_PGPGOUT,      /* # of pages paged out */
        MEM_CGROUP_EVENTS_COUNT,        /* # of pages paged in/out */
        MEM_CGROUP_EVENTS_PGFAULT,      /* # of page-faults */
        MEM_CGROUP_EVENTS_PGMAJFAULT,   /* # of major page-faults */
        MEM_CGROUP_EVENTS_NSTATS,
};
/*
 * 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 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           count[NR_LRU_LISTS];

        struct mem_cgroup_reclaim_iter reclaim_iter[DEF_PRIORITY + 1];

        struct zone_reclaim_stat reclaim_stat;
        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       *mem;           /* Back pointer, we cannot */
                                                /* use container_of        */
};
/* Macro for accessing counter */
#define MEM_CGROUP_ZSTAT(mz, idx)       ((mz)->count[(idx)])

struct mem_cgroup_per_node {
        struct mem_cgroup_per_zone zoneinfo[MAX_NR_ZONES];
};

struct mem_cgroup_lru_info {
        struct mem_cgroup_per_node *nodeinfo[MAX_NUMNODES];
};

/*
 * 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 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;
                /*
                 * But when using vfree(), that cannot be done at
                 * interrupt time, so we must then queue the work.
                 */
                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;
        /*
         * percpu counter.
         */
        struct mem_cgroup_stat_cpu *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;

#ifdef 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_MAPPED,
        MEM_CGROUP_CHARGE_TYPE_SHMEM,   /* used by page migration of shmem */
        MEM_CGROUP_CHARGE_TYPE_FORCE,   /* used by force_empty */
        MEM_CGROUP_CHARGE_TYPE_SWAPOUT, /* for accounting swapcache */
        MEM_CGROUP_CHARGE_TYPE_DROP,    /* a page was unused swap cache */
        NR_CHARGE_TYPE,
};

/* 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);

/* Writing them here to avoid exposing memcg's inner layout */
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
#include <net/sock.h>
#include <net/ip.h>

static bool mem_cgroup_is_root(struct mem_cgroup *memcg);
void sock_update_memcg(struct sock *sk)
{
        if (mem_cgroup_sockets_enabled) {
                struct mem_cgroup *memcg;

                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);
                if (!mem_cgroup_is_root(memcg)) {
                        mem_cgroup_get(memcg);
                        sk->sk_cgrp = sk->sk_prot->proto_cgroup(memcg);
                }
                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);
        }
}

#ifdef CONFIG_INET
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);
#endif /* CONFIG_INET */
#endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */

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->mem, mz, mctz);
        if (!res_counter_soft_limit_excess(&mz->mem->res) ||
                !css_tryget(&mz->mem->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_SWAPOUT], 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 file, int nr_pages)
{
        preempt_disable();

        if (file)
                __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
                                nr_pages);
        else
                __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
                                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->events[MEM_CGROUP_EVENTS_COUNT], nr_pages);

        preempt_enable();
}

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 l;
        unsigned long ret = 0;

        mz = mem_cgroup_zoneinfo(memcg, nid, zid);

        for_each_lru(l) {
                if (BIT(l) & lru_mask)
                        ret += MEM_CGROUP_ZSTAT(mz, l);
        }
        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->events[MEM_CGROUP_EVENTS_COUNT]);
        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 container_of(cgroup_subsys_state(cont,
                                mem_cgroup_subsys_id), struct mem_cgroup,
                                css);
}

struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p)
{
        /*
         * mm_update_next_owner() may clear mm->owner to NULL
         * if it races with swapoff, page migration, etc.
         * So this can be called with p == NULL.
         */
        if (unlikely(!p))
                return NULL;

        return container_of(task_subsys_state(p, mem_cgroup_subsys_id),
                                struct mem_cgroup, css);
}

struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
{
        struct mem_cgroup *memcg = NULL;

        if (!mm)
                return NULL;
        /*
         * Because we have no locks, mm->owner's may be being moved to other
         * cgroup. We use css_tryget() here even if this looks
         * pessimistic (rather than adding locks here).
         */
        rcu_read_lock();
        do {
                memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
                if (unlikely(!memcg))
                        break;
        } while (!css_tryget(&memcg->css));
        rcu_read_unlock();
        return memcg;
}

/**
 * mem_cgroup_iter - iterate over memory cgroup hierarchy
 * @root: hierarchy root
 * @prev: previously returned memcg, NULL on first invocation
 * @reclaim: cookie for shared reclaim walks, NULL for full walks
 *
 * Returns references to children of the hierarchy below @root, or
 * @root itself, or %NULL after a full round-trip.
 *
 * Caller must pass the return value in @prev on subsequent
 * invocations for reference counting, or use mem_cgroup_iter_break()
 * to cancel a hierarchy walk before the round-trip is complete.
 *
 * Reclaimers can specify a zone and a priority level in @reclaim to
 * divide up the memcgs in the hierarchy among all concurrent
 * reclaimers operating on the same zone and priority.
 */
struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
                                   struct mem_cgroup *prev,
                                   struct mem_cgroup_reclaim_cookie *reclaim)
{
        struct mem_cgroup *memcg = NULL;
        int id = 0;

        if (mem_cgroup_disabled())
                return NULL;

        if (!root)
                root = root_mem_cgroup;

        if (prev && !reclaim)
                id = css_id(&prev->css);

        if (prev && prev != root)
                css_put(&prev->css);

        if (!root->use_hierarchy && root != root_mem_cgroup) {
                if (prev)
                        return NULL;
                return root;
        }

        while (!memcg) {
                struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
                struct cgroup_subsys_state *css;

                if (reclaim) {
                        int nid = zone_to_nid(reclaim->zone);
                        int zid = zone_idx(reclaim->zone);
                        struct mem_cgroup_per_zone *mz;

                        mz = mem_cgroup_zoneinfo(root, nid, zid);
                        iter = &mz->reclaim_iter[reclaim->priority];
                        if (prev && reclaim->generation != iter->generation)
                                return NULL;
                        id = iter->position;
                }

                rcu_read_lock();
                css = css_get_next(&mem_cgroup_subsys, id + 1, &root->css, &id);
                if (css) {
                        if (css == &root->css || css_tryget(css))
                                memcg = container_of(css,
                                                     struct mem_cgroup, css);
                } else
                        id = 0;
                rcu_read_unlock();

                if (reclaim) {
                        iter->position = id;
                        if (!css)
                                iter->generation++;
                        else if (!prev && memcg)
                                reclaim->generation = iter->generation;
                }

                if (prev && !css)
                        return NULL;
        }
        return memcg;
}

/**
 * mem_cgroup_iter_break - abort a hierarchy walk prematurely
 * @root: hierarchy root
 * @prev: last visited hierarchy member as returned by mem_cgroup_iter()
 */
void mem_cgroup_iter_break(struct mem_cgroup *root,
                           struct mem_cgroup *prev)
{
        if (!root)
                root = root_mem_cgroup;
        if (prev && prev != root)
                css_put(&prev->css);
}

/*
 * Iteration constructs for visiting all cgroups (under a tree).  If
 * loops are exited prematurely (break), mem_cgroup_iter_break() must
 * be used for reference counting.
 */
#define for_each_mem_cgroup_tree(iter, root)            \
        for (iter = mem_cgroup_iter(root, NULL, NULL);  \
             iter != NULL;                              \
             iter = mem_cgroup_iter(root, iter, NULL))

#define for_each_mem_cgroup(iter)                       \
        for (iter = mem_cgroup_iter(NULL, NULL, NULL);  \
             iter != NULL;                              \
             iter = mem_cgroup_iter(NULL, iter, NULL))

static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
{
        return (memcg == root_mem_cgroup);
}

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);

/**
 * mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg
 * @zone: zone of the wanted lruvec
 * @mem: memcg of the wanted lruvec
 *
 * Returns the lru list vector holding pages for the given @zone and
 * @mem.  This can be the global zone lruvec, if the memory controller
 * is disabled.
 */
struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
                                      struct mem_cgroup *memcg)
{
        struct mem_cgroup_per_zone *mz;

        if (mem_cgroup_disabled())
                return &zone->lruvec;

        mz = mem_cgroup_zoneinfo(memcg, zone_to_nid(zone), zone_idx(zone));
        return &mz->lruvec;
}

/*
 * Following LRU functions are allowed to be used without PCG_LOCK.
 * Operations are called by routine of global LRU independently from memcg.
 * What we have to take care of here is validness of pc->mem_cgroup.
 *
 * Changes to pc->mem_cgroup happens when
 * 1. charge
 * 2. moving account
 * In typical case, "charge" is done before add-to-lru. Exception is SwapCache.
 * It is added to LRU before charge.
 * If PCG_USED bit is not set, page_cgroup is not added to this private LRU.
 * When moving account, the page is not on LRU. It's isolated.
 */

/**
 * mem_cgroup_lru_add_list - account for adding an lru page and return lruvec
 * @zone: zone of the page
 * @page: the page
 * @lru: current lru
 *
 * This function accounts for @page being added to @lru, and returns
 * the lruvec for the given @zone and the memcg @page is charged to.
 *
 * The callsite is then responsible for physically linking the page to
 * the returned lruvec->lists[@lru].
 */
struct lruvec *mem_cgroup_lru_add_list(struct zone *zone, struct page *page,
                                       enum lru_list lru)
{
        struct mem_cgroup_per_zone *mz;
        struct mem_cgroup *memcg;
        struct page_cgroup *pc;

        if (mem_cgroup_disabled())
                return &zone->lruvec;

        pc = lookup_page_cgroup(page);
        memcg = pc->mem_cgroup;

        /*
         * Surreptitiously switch any uncharged 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 (!PageCgroupUsed(pc) && memcg != root_mem_cgroup)
                pc->mem_cgroup = memcg = root_mem_cgroup;

        mz = page_cgroup_zoneinfo(memcg, page);
        /* compound_order() is stabilized through lru_lock */
        MEM_CGROUP_ZSTAT(mz, lru) += 1 << compound_order(page);
        return &mz->lruvec;
}

/**
 * mem_cgroup_lru_del_list - account for removing an lru page
 * @page: the page
 * @lru: target lru
 *
 * This function accounts for @page being removed from @lru.
 *
 * The callsite is then responsible for physically unlinking
 * @page->lru.
 */
void mem_cgroup_lru_del_list(struct page *page, enum lru_list lru)
{
        struct mem_cgroup_per_zone *mz;
        struct mem_cgroup *memcg;
        struct page_cgroup *pc;

        if (mem_cgroup_disabled())
                return;

        pc = lookup_page_cgroup(page);
        memcg = pc->mem_cgroup;
        VM_BUG_ON(!memcg);
        mz = page_cgroup_zoneinfo(memcg, page);
        /* huge page split is done under lru_lock. so, we have no races. */
        VM_BUG_ON(MEM_CGROUP_ZSTAT(mz, lru) < (1 << compound_order(page)));
        MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
}

void mem_cgroup_lru_del(struct page *page)
{
        mem_cgroup_lru_del_list(page, page_lru(page));
}

/**
 * mem_cgroup_lru_move_lists - account for moving a page between lrus
 * @zone: zone of the page
 * @page: the page
 * @from: current lru
 * @to: target lru
 *
 * This function accounts for @page being moved between the lrus @from
 * and @to, and returns the lruvec for the given @zone and the memcg
 * @page is charged to.
 *
 * The callsite is then responsible for physically relinking
 * @page->lru to the returned lruvec->lists[@to].
 */
struct lruvec *mem_cgroup_lru_move_lists(struct zone *zone,
                                         struct page *page,
                                         enum lru_list from,
                                         enum lru_list to)
{
        /* XXX: Optimize this, especially for @from == @to */
        mem_cgroup_lru_del_list(page, from);
        return mem_cgroup_lru_add_list(zone, page, to);
}

/*
 * Checks whether given mem is same or in the root_mem_cgroup's
 * hierarchy subtree
 */
static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
                struct mem_cgroup *memcg)
{
        if (root_memcg != memcg) {
                return (root_memcg->use_hierarchy &&
                        css_is_ancestor(&memcg->css, &root_memcg->css));
        }

        return true;
}

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 mem_cgroup *memcg, struct zone *zone)
{
        unsigned long inactive_ratio;
        int nid = zone_to_nid(zone);
        int zid = zone_idx(zone);
        unsigned long inactive;
        unsigned long active;
        unsigned long gb;

        inactive = mem_cgroup_zone_nr_lru_pages(memcg, nid, zid,
                                                BIT(LRU_INACTIVE_ANON));
        active = mem_cgroup_zone_nr_lru_pages(memcg, nid, zid,
                                              BIT(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 mem_cgroup *memcg, struct zone *zone)
{
        unsigned long active;
        unsigned long inactive;
        int zid = zone_idx(zone);
        int nid = zone_to_nid(zone);

        inactive = mem_cgroup_zone_nr_lru_pages(memcg, nid, zid,
                                                BIT(LRU_INACTIVE_FILE));
        active = mem_cgroup_zone_nr_lru_pages(memcg, nid, zid,
                                              BIT(LRU_ACTIVE_FILE));

        return (active > inactive);
}

struct zone_reclaim_stat *mem_cgroup_get_reclaim_stat(struct mem_cgroup *memcg,
                                                      struct zone *zone)
{
        int nid = zone_to_nid(zone);
        int zid = zone_idx(zone);
        struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);

        return &mz->reclaim_stat;
}

struct zone_reclaim_stat *
mem_cgroup_get_reclaim_stat_from_page(struct page *page)
{
        struct page_cgroup *pc;
        struct mem_cgroup_per_zone *mz;

        if (mem_cgroup_disabled())
                return NULL;

        pc = lookup_page_cgroup(page);
        if (!PageCgroupUsed(pc))
                return NULL;
        /* Ensure pc->mem_cgroup is visible after reading PCG_USED. */
        smp_rmb();
        mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
        return &mz->reclaim_stat;
}

#define mem_cgroup_from_res_counter(counter, member)    \
        container_of(counter, struct mem_cgroup, member)

/**
 * mem_cgroup_margin - calculate chargeable space of a memory cgroup
 * @mem: the memory cgroup
 *
 * Returns the maximum amount of memory @mem can be charged with, in
 * pages.
 */
static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
{
        unsigned long long margin;

        margin = res_counter_margin(&memcg->res);
        if (do_swap_account)
                margin = min(margin, res_counter_margin(&memcg->memsw));
        return margin >> PAGE_SHIFT;
}

int mem_cgroup_swappiness(struct mem_cgroup *memcg)
{
        struct cgroup *cgrp = memcg->css.cgroup;

        /* root ? */
        if (cgrp->parent == NULL)
                return vm_swappiness;

        return memcg->swappiness;
}

static void mem_cgroup_start_move(struct mem_cgroup *memcg)
{
        int cpu;

        get_online_cpus();
        spin_lock(&memcg->pcp_counter_lock);
        for_each_online_cpu(cpu)
                per_cpu(memcg->stat->count[MEM_CGROUP_ON_MOVE], cpu) += 1;
        memcg->nocpu_base.count[MEM_CGROUP_ON_MOVE] += 1;
        spin_unlock(&memcg->pcp_counter_lock);
        put_online_cpus();

        synchronize_rcu();
}

static void mem_cgroup_end_move(struct mem_cgroup *memcg)
{
        int cpu;

        if (!memcg)
                return;
        get_online_cpus();
        spin_lock(&memcg->pcp_counter_lock);
        for_each_online_cpu(cpu)
                per_cpu(memcg->stat->count[MEM_CGROUP_ON_MOVE], cpu) -= 1;
        memcg->nocpu_base.count[MEM_CGROUP_ON_MOVE] -= 1;
        spin_unlock(&memcg->pcp_counter_lock);
        put_online_cpus();
}
/*
 * 2 routines for checking "mem" is under move_account() or not.
 *
 * mem_cgroup_stealed() - checking a cgroup is mc.from or not. This is used
 *                        for avoiding race 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_stealed(struct mem_cgroup *memcg)
{
        VM_BUG_ON(!rcu_read_lock_held());
        return this_cpu_read(memcg->stat->count[MEM_CGROUP_ON_MOVE]) > 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;
}

/**
 * mem_cgroup_print_oom_info: Called from OOM with tasklist_lock held in read mode.
 * @memcg: The memory cgroup that went over limit
 * @p: Task that is going to be killed
 *
 * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
 * enabled
 */
void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
{
        struct cgroup *task_cgrp;
        struct cgroup *mem_cgrp;
        /*
         * Need a buffer in BSS, can't rely on allocations. The code relies
         * on the assumption that OOM is serialized for memory controller.
         * If this assumption is broken, revisit this code.
         */
        static char memcg_name[PATH_MAX];
        int ret;

        if (!memcg || !p)
                return;


        rcu_read_lock();

        mem_cgrp = memcg->css.cgroup;
        task_cgrp = task_cgroup(p, mem_cgroup_subsys_id);

        ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX);
        if (ret < 0) {
                /*
                 * Unfortunately, we are unable to convert to a useful name
                 * But we'll still print out the usage information
                 */
                rcu_read_unlock();
                goto done;
        }
        rcu_read_unlock();

        printk(KERN_INFO "Task in %s killed", memcg_name);

        rcu_read_lock();
        ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
        if (ret < 0) {
                rcu_read_unlock();
                goto done;
        }
        rcu_read_unlock();

        /*
         * Continues from above, so we don't need an KERN_ level
         */
        printk(KERN_CONT " as a result of limit of %s\n", memcg_name);
done:

        printk(KERN_INFO "memory: usage %llukB, limit %llukB, failcnt %llu\n",
                res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
                res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
                res_counter_read_u64(&memcg->res, RES_FAILCNT));
        printk(KERN_INFO "memory+swap: usage %llukB, limit %llukB, "
                "failcnt %llu\n",
                res_counter_read_u64(&memcg->memsw, RES_USAGE) >> 10,
                res_counter_read_u64(&memcg->memsw, RES_LIMIT) >> 10,
                res_counter_read_u64(&memcg->memsw, RES_FAILCNT));
}

/*
 * 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.
 */
u64 mem_cgroup_get_limit(struct mem_cgroup *memcg)
{
        u64 limit;
        u64 memsw;

        limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
        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.
         */
        return min(limit, memsw);
}

static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
                                        gfp_t gfp_mask,
                                        unsigned long flags)
{
        unsigned long total = 0;
        bool noswap = false;
        int loop;

        if (flags & MEM_CGROUP_RECLAIM_NOSWAP)
                noswap = true;
        if (!(flags & MEM_CGROUP_RECLAIM_SHRINK) && memcg->memsw_is_minimum)
                noswap = true;

        for (loop = 0; loop < MEM_CGROUP_MAX_RECLAIM_LOOPS; loop++) {
                if (loop)
                        drain_all_stock_async(memcg);
                total += try_to_free_mem_cgroup_pages(memcg, gfp_mask, noswap);
                /*
                 * Allow limit shrinkers, which are triggered directly
                 * by userspace, to catch signals and stop reclaim
                 * after minimal progress, regardless of the margin.
                 */
                if (total && (flags & MEM_CGROUP_RECLAIM_SHRINK))
                        break;
                if (mem_cgroup_margin(memcg))
                        break;
                /*
                 * If nothing was reclaimed after two attempts, there
                 * may be no reclaimable pages in this hierarchy.
                 */
                if (loop && !total)
                        break;
        }
        return total;
}

/**
 * test_mem_cgroup_node_reclaimable
 * @mem: the target memcg
 * @nid: the node ID to be checked.
 * @noswap : specify true here if the user wants flle only information.
 *
 * This function returns whether the specified memcg contains any
 * reclaimable pages on a node. Returns true if there are any reclaimable
 * pages in the node.
 */
static bool test_mem_cgroup_node_reclaimable(struct mem_cgroup *memcg,
                int nid, bool noswap)
{
        if (mem_cgroup_node_nr_lru_pages(memcg, nid, LRU_ALL_FILE))
                return true;
        if (noswap || !total_swap_pages)
                return false;
        if (mem_cgroup_node_nr_lru_pages(memcg, nid, LRU_ALL_ANON))
                return true;
        return false;

}
#if MAX_NUMNODES > 1

/*
 * Always updating the nodemask is not very good - even if we have an empty
 * list or the wrong list here, we can start from some node and traverse all
 * nodes based on the zonelist. So update the list loosely once per 10 secs.
 *
 */
static void mem_cgroup_may_update_nodemask(struct mem_cgroup *memcg)
{
        int nid;
        /*
         * numainfo_events > 0 means there was at least NUMAINFO_EVENTS_TARGET
         * pagein/pageout changes since the last update.
         */
        if (!atomic_read(&memcg->numainfo_events))
                return;
        if (atomic_inc_return(&memcg->numainfo_updating) > 1)
                return;

        /* make a nodemask where this memcg uses memory from */
        memcg->scan_nodes = node_states[N_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.
 */
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;
}

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 *mem;
        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,
                          *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->mem;

        /*
         * Both of oom_wait_info->mem and wake_mem 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.
 */
bool mem_cgroup_handle_oom(struct mem_cgroup *memcg, gfp_t mask)
{
        struct oom_wait_info owait;
        bool locked, need_to_kill;

        owait.mem = 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);
        } 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 MEM_CGROUP_ON_MOVE percpu value and detect there are
 * possibility of race condition. If there is, we take a lock.
 */

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);
        bool need_unlock = false;
        unsigned long uninitialized_var(flags);

        if (mem_cgroup_disabled())
                return;

        rcu_read_lock();
        memcg = pc->mem_cgroup;
        if (unlikely(!memcg || !PageCgroupUsed(pc)))
                goto out;
        /* pc->mem_cgroup is unstable ? */
        if (unlikely(mem_cgroup_stealed(memcg)) || PageTransHuge(page)) {
                /* take a lock against to access pc->mem_cgroup */
                move_lock_page_cgroup(pc, &flags);
                need_unlock = true;
                memcg = pc->mem_cgroup;
                if (!memcg || !PageCgroupUsed(pc))
                        goto out;
        }

        switch (idx) {
        case MEMCG_NR_FILE_MAPPED:
                if (val > 0)
                        SetPageCgroupFileMapped(pc);
                else if (!page_mapped(page))
                        ClearPageCgroupFileMapped(pc);
                idx = MEM_CGROUP_STAT_FILE_MAPPED;
                break;
        default:
                BUG();
        }

        this_cpu_add(memcg->stat->count[idx], val);

out:
        if (unlikely(need_unlock))
                move_unlock_page_cgroup(pc, &flags);
        rcu_read_unlock();
        return;
}
EXPORT_SYMBOL(mem_cgroup_update_page_stat);

/*
 * 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.