/* 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/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 "internal.h"

#include <asm/uaccess.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;
static int really_do_swap_account __initdata = 1; /* for remember boot option*/
#else
#define do_swap_account         (0)
#endif

/*
 * Per memcg event counter is incremented at every pagein/pageout. This counter
 * is used for trigger some periodic events. This is straightforward and better
 * than using jiffies etc. to handle periodic memcg event.
 *
 * These values will be used as !((event) & ((1 <<(thresh)) - 1))
 */
#define THRESHOLDS_EVENTS_THRESH (7) /* once in 128 */
#define SOFTLIMIT_EVENTS_THRESH (10) /* once in 1024 */

/*
 * 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_PGPGIN_COUNT,   /* # of pages paged in */
        MEM_CGROUP_STAT_PGPGOUT_COUNT,  /* # of pages paged out */
        MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
        MEM_CGROUP_EVENTS,      /* incremented at every  pagein/pageout */

        MEM_CGROUP_STAT_NSTATS,
};

struct mem_cgroup_stat_cpu {
        s64 count[MEM_CGROUP_STAT_NSTATS];
};

/*
 * per-zone information in memory controller.
 */
struct mem_cgroup_per_zone {
        /*
         * spin_lock to protect the per cgroup LRU
         */
        struct list_head        lists[NR_LRU_LISTS];
        unsigned long           count[NR_LRU_LISTS];

        struct zone_reclaim_stat reclaim_stat;
        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 *mem);
static void mem_cgroup_oom_notify(struct mem_cgroup *mem);

/*
 * The memory controller data structure. The memory controller controls both
 * page cache and RSS per cgroup. We would eventually like to provide
 * statistics based on the statistics developed by Rik Van Riel for clock-pro,
 * to help the administrator determine what knobs to tune.
 *
 * TODO: Add a water mark for the memory controller. Reclaim will begin when
 * we hit the water mark. May be even add a low water mark, such that
 * no reclaim occurs from a cgroup at it's low water mark, this is
 * a feature that will be implemented much later in the future.
 */
struct mem_cgroup {
        struct cgroup_subsys_state css;
        /*
         * the counter to account for memory usage
         */
        struct res_counter res;
        /*
         * the counter to account for mem+swap usage.
         */
        struct res_counter memsw;
        /*
         * Per cgroup active and inactive list, similar to the
         * per zone LRU lists.
         */
        struct mem_cgroup_lru_info info;

        /*
          protect against reclaim related member.
        */
        spinlock_t reclaim_param_lock;

        int     prev_priority;  /* for recording reclaim priority */

        /*
         * While reclaiming in a hierarchy, we cache the last child we
         * reclaimed from.
         */
        int last_scanned_child;
        /*
         * Should the accounting and control be hierarchical, per subtree?
         */
        bool use_hierarchy;
        atomic_t        oom_lock;
        atomic_t        refcnt;

        unsigned 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;
};

/* 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 {
        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 = {
        .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,
};

/* only for here (for easy reading.) */
#define PCGF_CACHE      (1UL << PCG_CACHE)
#define PCGF_USED       (1UL << PCG_USED)
#define PCGF_LOCK       (1UL << PCG_LOCK)
/* Not used, but added here for completeness */
#define PCGF_ACCT       (1UL << PCG_ACCT)

/* 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)
#define MEM_CGROUP_RECLAIM_SOFT_BIT     0x2
#define MEM_CGROUP_RECLAIM_SOFT         (1 << MEM_CGROUP_RECLAIM_SOFT_BIT)

static void mem_cgroup_get(struct mem_cgroup *mem);
static void mem_cgroup_put(struct mem_cgroup *mem);
static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
static void drain_all_stock_async(void);

static struct mem_cgroup_per_zone *
mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
{
        return &mem->info.nodeinfo[nid]->zoneinfo[zid];
}

struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *mem)
{
        return &mem->css;
}

static struct mem_cgroup_per_zone *
page_cgroup_zoneinfo(struct page_cgroup *pc)
{
        struct mem_cgroup *mem = pc->mem_cgroup;
        int nid = page_cgroup_nid(pc);
        int zid = page_cgroup_zid(pc);

        if (!mem)
                return NULL;

        return mem_cgroup_zoneinfo(mem, nid, zid);
}

static 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 *mem,
                                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 *mem,
                                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 *mem,
                                struct mem_cgroup_per_zone *mz,
                                struct mem_cgroup_tree_per_zone *mctz)
{
        spin_lock(&mctz->lock);
        __mem_cgroup_remove_exceeded(mem, mz, mctz);
        spin_unlock(&mctz->lock);
}


static void mem_cgroup_update_tree(struct mem_cgroup *mem, 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 (; mem; mem = parent_mem_cgroup(mem)) {
                mz = mem_cgroup_zoneinfo(mem, nid, zid);
                excess = res_counter_soft_limit_excess(&mem->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(mem, mz, mctz);
                        /*
                         * Insert again. mz->usage_in_excess will be updated.
                         * If excess is 0, no tree ops.
                         */
                        __mem_cgroup_insert_exceeded(mem, mz, mctz, excess);
                        spin_unlock(&mctz->lock);
                }
        }
}

static void mem_cgroup_remove_from_trees(struct mem_cgroup *mem)
{
        int node, zone;
        struct mem_cgroup_per_zone *mz;
        struct mem_cgroup_tree_per_zone *mctz;

        for_each_node_state(node, N_POSSIBLE) {
                for (zone = 0; zone < MAX_NR_ZONES; zone++) {
                        mz = mem_cgroup_zoneinfo(mem, node, zone);
                        mctz = soft_limit_tree_node_zone(node, zone);
                        mem_cgroup_remove_exceeded(mem, mz, mctz);
                }
        }
}

static inline unsigned long mem_cgroup_get_excess(struct mem_cgroup *mem)
{
        return res_counter_soft_limit_excess(&mem->res) >> PAGE_SHIFT;
}

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;
}

static s64 mem_cgroup_read_stat(struct mem_cgroup *mem,
                enum mem_cgroup_stat_index idx)
{
        int cpu;
        s64 val = 0;

        for_each_possible_cpu(cpu)
                val += per_cpu(mem->stat->count[idx], cpu);
        return val;
}

static s64 mem_cgroup_local_usage(struct mem_cgroup *mem)
{
        s64 ret;

        ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
        ret += mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
        return ret;
}

static void mem_cgroup_swap_statistics(struct mem_cgroup *mem,
                                         bool charge)
{
        int val = (charge) ? 1 : -1;
        this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_SWAPOUT], val);
}

static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
                                         struct page_cgroup *pc,
                                         bool charge)
{
        int val = (charge) ? 1 : -1;

        preempt_disable();

        if (PageCgroupCache(pc))
                __this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_CACHE], val);
        else
                __this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_RSS], val);

        if (charge)
                __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGIN_COUNT]);
        else
                __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGOUT_COUNT]);
        __this_cpu_inc(mem->stat->count[MEM_CGROUP_EVENTS]);

        preempt_enable();
}

static unsigned long mem_cgroup_get_local_zonestat(struct mem_cgroup *mem,
                                        enum lru_list idx)
{
        int nid, zid;
        struct mem_cgroup_per_zone *mz;
        u64 total = 0;

        for_each_online_node(nid)
                for (zid = 0; zid < MAX_NR_ZONES; zid++) {
                        mz = mem_cgroup_zoneinfo(mem, nid, zid);
                        total += MEM_CGROUP_ZSTAT(mz, idx);
                }
        return total;
}

static bool __memcg_event_check(struct mem_cgroup *mem, int event_mask_shift)
{
        s64 val;

        val = this_cpu_read(mem->stat->count[MEM_CGROUP_EVENTS]);

        return !(val & ((1 << event_mask_shift) - 1));
}

/*
 * Check events in order.
 *
 */
static void memcg_check_events(struct mem_cgroup *mem, struct page *page)
{
        /* threshold event is triggered in finer grain than soft limit */
        if (unlikely(__memcg_event_check(mem, THRESHOLDS_EVENTS_THRESH))) {
                mem_cgroup_threshold(mem);
                if (unlikely(__memcg_event_check(mem, SOFTLIMIT_EVENTS_THRESH)))
                        mem_cgroup_update_tree(mem, page);
        }
}

static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
{
        return container_of(cgroup_subsys_state(cont,
                                mem_cgroup_subsys_id), struct mem_cgroup,
                                css);
}

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

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

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

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

/*
 * Call callback function against all cgroup under hierarchy tree.
 */
static int mem_cgroup_walk_tree(struct mem_cgroup *root, void *data,
                          int (*func)(struct mem_cgroup *, void *))
{
        int found, ret, nextid;
        struct cgroup_subsys_state *css;
        struct mem_cgroup *mem;

        if (!root->use_hierarchy)
                return (*func)(root, data);

        nextid = 1;
        do {
                ret = 0;
                mem = NULL;

                rcu_read_lock();
                css = css_get_next(&mem_cgroup_subsys, nextid, &root->css,
                                   &found);
                if (css && css_tryget(css))
                        mem = container_of(css, struct mem_cgroup, css);
                rcu_read_unlock();

                if (mem) {
                        ret = (*func)(mem, data);
                        css_put(&mem->css);
                }
                nextid = found + 1;
        } while (!ret && css);

        return ret;
}

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

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

void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
{
        struct page_cgroup *pc;
        struct mem_cgroup_per_zone *mz;

        if (mem_cgroup_disabled())
                return;
        pc = lookup_page_cgroup(page);
        /* can happen while we handle swapcache. */
        if (!TestClearPageCgroupAcctLRU(pc))
                return;
        VM_BUG_ON(!pc->mem_cgroup);
        /*
         * We don't check PCG_USED bit. It's cleared when the "page" is finally
         * removed from global LRU.
         */
        mz = page_cgroup_zoneinfo(pc);
        MEM_CGROUP_ZSTAT(mz, lru) -= 1;
        if (mem_cgroup_is_root(pc->mem_cgroup))
                return;
        VM_BUG_ON(list_empty(&pc->lru));
        list_del_init(&pc->lru);
        return;
}

void mem_cgroup_del_lru(struct page *page)
{
        mem_cgroup_del_lru_list(page, page_lru(page));
}

void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
{
        struct mem_cgroup_per_zone *mz;
        struct page_cgroup *pc;

        if (mem_cgroup_disabled())
                return;

        pc = lookup_page_cgroup(page);
        /*
         * Used bit is set without atomic ops but after smp_wmb().
         * For making pc->mem_cgroup visible, insert smp_rmb() here.
         */
        smp_rmb();
        /* unused or root page is not rotated. */
        if (!PageCgroupUsed(pc) || mem_cgroup_is_root(pc->mem_cgroup))
                return;
        mz = page_cgroup_zoneinfo(pc);
        list_move(&pc->lru, &mz->lists[lru]);
}

void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
{
        struct page_cgroup *pc;
        struct mem_cgroup_per_zone *mz;

        if (mem_cgroup_disabled())
                return;
        pc = lookup_page_cgroup(page);
        VM_BUG_ON(PageCgroupAcctLRU(pc));
        /*
         * Used bit is set without atomic ops but after smp_wmb().
         * For making pc->mem_cgroup visible, insert smp_rmb() here.
         */
        smp_rmb();
        if (!PageCgroupUsed(pc))
                return;

        mz = page_cgroup_zoneinfo(pc);
        MEM_CGROUP_ZSTAT(mz, lru) += 1;
        SetPageCgroupAcctLRU(pc);
        if (mem_cgroup_is_root(pc->mem_cgroup))
                return;
        list_add(&pc->lru, &mz->lists[lru]);
}

/*
 * At handling SwapCache, pc->mem_cgroup may be changed while it's linked to
 * lru because the page may.be reused after it's fully uncharged (because of
 * SwapCache behavior).To handle that, unlink page_cgroup from LRU when charge
 * it again. This function is only used to charge SwapCache. It's done under
 * lock_page and expected that zone->lru_lock is never held.
 */
static void mem_cgroup_lru_del_before_commit_swapcache(struct page *page)
{
        unsigned long flags;
        struct zone *zone = page_zone(page);
        struct page_cgroup *pc = lookup_page_cgroup(page);

        spin_lock_irqsave(&zone->lru_lock, flags);
        /*
         * Forget old LRU when this page_cgroup is *not* used. This Used bit
         * is guarded by lock_page() because the page is SwapCache.
         */
        if (!PageCgroupUsed(pc))
                mem_cgroup_del_lru_list(page, page_lru(page));
        spin_unlock_irqrestore(&zone->lru_lock, flags);
}

static void mem_cgroup_lru_add_after_commit_swapcache(struct page *page)
{
        unsigned long flags;
        struct zone *zone = page_zone(page);
        struct page_cgroup *pc = lookup_page_cgroup(page);

        spin_lock_irqsave(&zone->lru_lock, flags);
        /* link when the page is linked to LRU but page_cgroup isn't */
        if (PageLRU(page) && !PageCgroupAcctLRU(pc))
                mem_cgroup_add_lru_list(page, page_lru(page));
        spin_unlock_irqrestore(&zone->lru_lock, flags);
}


void mem_cgroup_move_lists(struct page *page,
                           enum lru_list from, enum lru_list to)
{
        if (mem_cgroup_disabled())
                return;
        mem_cgroup_del_lru_list(page, from);
        mem_cgroup_add_lru_list(page, to);
}

int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
{
        int ret;
        struct mem_cgroup *curr = NULL;

        task_lock(task);
        rcu_read_lock();
        curr = try_get_mem_cgroup_from_mm(task->mm);
        rcu_read_unlock();
        task_unlock(task);
        if (!curr)
                return 0;
        /*
         * We should check use_hierarchy of "mem" not "curr". Because checking
         * use_hierarchy of "curr" here make this function true if hierarchy is
         * enabled in "curr" and "curr" is a child of "mem" in *cgroup*
         * hierarchy(even if use_hierarchy is disabled in "mem").
         */
        if (mem->use_hierarchy)
                ret = css_is_ancestor(&curr->css, &mem->css);
        else
                ret = (curr == mem);
        css_put(&curr->css);
        return ret;
}

/*
 * prev_priority control...this will be used in memory reclaim path.
 */
int mem_cgroup_get_reclaim_priority(struct mem_cgroup *mem)
{
        int prev_priority;

        spin_lock(&mem->reclaim_param_lock);
        prev_priority = mem->prev_priority;
        spin_unlock(&mem->reclaim_param_lock);

        return prev_priority;
}

void mem_cgroup_note_reclaim_priority(struct mem_cgroup *mem, int priority)
{
        spin_lock(&mem->reclaim_param_lock);
        if (priority < mem->prev_priority)
                mem->prev_priority = priority;
        spin_unlock(&mem->reclaim_param_lock);
}

void mem_cgroup_record_reclaim_priority(struct mem_cgroup *mem, int priority)
{
        spin_lock(&mem->reclaim_param_lock);
        mem->prev_priority = priority;
        spin_unlock(&mem->reclaim_param_lock);
}

static int calc_inactive_ratio(struct mem_cgroup *memcg, unsigned long *present_pages)
{
        unsigned long active;
        unsigned long inactive;
        unsigned long gb;
        unsigned long inactive_ratio;

        inactive = mem_cgroup_get_local_zonestat(memcg, LRU_INACTIVE_ANON);
        active = mem_cgroup_get_local_zonestat(memcg, LRU_ACTIVE_ANON);

        gb = (inactive + active) >> (30 - PAGE_SHIFT);
        if (gb)
                inactive_ratio = int_sqrt(10 * gb);
        else
                inactive_ratio = 1;

        if (present_pages) {
                present_pages[0] = inactive;
                present_pages[1] = active;
        }

        return inactive_ratio;
}

int mem_cgroup_inactive_anon_is_low(struct mem_cgroup *memcg)
{
        unsigned long active;
        unsigned long inactive;
        unsigned long present_pages[2];
        unsigned long inactive_ratio;

        inactive_ratio = calc_inactive_ratio(memcg, present_pages);

        inactive = present_pages[0];
        active = present_pages[1];

        if (inactive * inactive_ratio < active)
                return 1;

        return 0;
}

int mem_cgroup_inactive_file_is_low(struct mem_cgroup *memcg)
{
        unsigned long active;
        unsigned long inactive;

        inactive = mem_cgroup_get_local_zonestat(memcg, LRU_INACTIVE_FILE);
        active = mem_cgroup_get_local_zonestat(memcg, LRU_ACTIVE_FILE);

        return (active > inactive);
}

unsigned long mem_cgroup_zone_nr_pages(struct mem_cgroup *memcg,
                                       struct zone *zone,
                                       enum lru_list lru)
{
        int nid = zone->zone_pgdat->node_id;
        int zid = zone_idx(zone);
        struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);

        return MEM_CGROUP_ZSTAT(mz, lru);
}

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

        return &mz->reclaim_stat;
}

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

        if (mem_cgroup_disabled())
                return NULL;

        pc = lookup_page_cgroup(page);
        /*
         * Used bit is set without atomic ops but after smp_wmb().
         * For making pc->mem_cgroup visible, insert smp_rmb() here.
         */
        smp_rmb();
        if (!PageCgroupUsed(pc))
                return NULL;

        mz = page_cgroup_zoneinfo(pc);
        if (!mz)
                return NULL;

        return &mz->reclaim_stat;
}

unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
                                        struct list_head *dst,
                                        unsigned long *scanned, int order,
                                        int mode, struct zone *z,
                                        struct mem_cgroup *mem_cont,
                                        int active, int file)
{
        unsigned long nr_taken = 0;
        struct page *page;
        unsigned long scan;
        LIST_HEAD(pc_list);
        struct list_head *src;

        struct page_cgroup *pc, *tmp;
        int nid = z->zone_pgdat->node_id;
        int zid = zone_idx(z);
        struct mem_cgroup_per_zone *mz;
        int lru = LRU_FILE * file + active;
        int ret;

        BUG_ON(!mem_cont);
        mz = mem_cgroup_zoneinfo(mem_cont, nid, zid);
        src = &mz->lists[lru];

        scan = 0;
        list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
                if (scan >= nr_to_scan)
                        break;

                page = pc->page;
                if (unlikely(!PageCgroupUsed(pc)))
                        continue;
                if (unlikely(!PageLRU(page)))
                        continue;

                scan++;
                ret = __isolate_lru_page(page, mode, file);
                switch (ret) {
                case 0:
                        list_move(&page->lru, dst);
                        mem_cgroup_del_lru(page);
                        nr_taken++;
                        break;
                case -EBUSY:
                        /* we don't affect global LRU but rotate in our LRU */
                        mem_cgroup_rotate_lru_list(page, page_lru(page));
                        break;
                default:
                        break;
                }
        }

        *scanned = scan;
        return nr_taken;
}

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

static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem)
{
        if (do_swap_account) {
                if (res_counter_check_under_limit(&mem->res) &&
                        res_counter_check_under_limit(&mem->memsw))
                        return true;
        } else
                if (res_counter_check_under_limit(&mem->res))
                        return true;
        return false;
}

static unsigned int get_swappiness(struct mem_cgroup *memcg)
{
        struct cgroup *cgrp = memcg->css.cgroup;
        unsigned int swappiness;

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

        spin_lock(&memcg->reclaim_param_lock);
        swappiness = memcg->swappiness;
        spin_unlock(&memcg->reclaim_param_lock);

        return swappiness;
}

static int mem_cgroup_count_children_cb(struct mem_cgroup *mem, void *data)
{
        int *val = data;
        (*val)++;
        return 0;
}

/**
 * mem_cgroup_print_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 *mem)
{
        int num = 0;
        mem_cgroup_walk_tree(mem, &num, mem_cgroup_count_children_cb);
        return num;
}

/*
 * Visit the first child (need not be the first child as per the ordering
 * of the cgroup list, since we track last_scanned_child) of @mem and use
 * that to reclaim free pages from.
 */
static struct mem_cgroup *
mem_cgroup_select_victim(struct mem_cgroup *root_mem)
{
        struct mem_cgroup *ret = NULL;
        struct cgroup_subsys_state *css;
        int nextid, found;

        if (!root_mem->use_hierarchy) {
                css_get(&root_mem->css);
                ret = root_mem;
        }

        while (!ret) {
                rcu_read_lock();
                nextid = root_mem->last_scanned_child + 1;
                css = css_get_next(&mem_cgroup_subsys, nextid, &root_mem->css,
                                   &found);
                if (css && css_tryget(css))
                        ret = container_of(css, struct mem_cgroup, css);

                rcu_read_unlock();
                /* Updates scanning parameter */
                spin_lock(&root_mem->reclaim_param_lock);
                if (!css) {
                        /* this means start scan from ID:1 */
                        root_mem->last_scanned_child = 0;
                } else
                        root_mem->last_scanned_child = found;
                spin_unlock(&root_mem->reclaim_param_lock);
        }

        return ret;
}

/*
 * Scan the hierarchy if needed to reclaim memory. We remember the last child
 * we reclaimed from, so that we don't end up penalizing one child extensively
 * based on its position in the children list.
 *
 * root_mem is the original ancestor that we've been reclaim from.
 *
 * We give up and return to the caller when we visit root_mem twice.
 * (other groups can be removed while we're walking....)
 *
 * If shrink==true, for avoiding to free too much, this returns immedieately.
 */
static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
                                                struct zone *zone,
                                                gfp_t gfp_mask,
                                                unsigned long reclaim_options)
{
        struct mem_cgroup *victim;
        int ret, total = 0;
        int loop = 0;
        bool noswap = reclaim_options & MEM_CGROUP_RECLAIM_NOSWAP;
        bool shrink = reclaim_options & MEM_CGROUP_RECLAIM_SHRINK;
        bool check_soft = reclaim_options & MEM_CGROUP_RECLAIM_SOFT;
        unsigned long excess = mem_cgroup_get_excess(root_mem);

        /* If memsw_is_minimum==1, swap-out is of-no-use. */
        if (root_mem->memsw_is_minimum)
                noswap = true;

        while (1) {
                victim = mem_cgroup_select_victim(root_mem);
                if (victim == root_mem) {
                        loop++;
                        if (loop >= 1)
                                drain_all_stock_async();
                        if (loop >= 2) {
                                /*
                                 * If we have not been able to reclaim
                                 * anything, it might because there are
                                 * no reclaimable pages under this hierarchy
                                 */
                                if (!check_soft || !total) {
                                        css_put(&victim->css);
                                        break;
                                }
                                /*
                                 * We want to do more targetted 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)) {
                                        css_put(&victim->css);
                                        break;
                                }
                        }
                }
                if (!mem_cgroup_local_usage(victim)) {
                        /* this cgroup's local usage == 0 */
                        css_put(&victim->css);
                        continue;
                }
                /* we use swappiness of local cgroup */
                if (check_soft)
                        ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
                                noswap, get_swappiness(victim), zone,
                                zone->zone_pgdat->node_id);
                else
                        ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
                                                noswap, get_swappiness(victim));
                css_put(&victim->css);
                /*
                 * At shrinking usage, we can't check we should stop here or
                 * reclaim more. It's depends on callers. last_scanned_child
                 * will work enough for keeping fairness under tree.
                 */
                if (shrink)
                        return ret;
                total += ret;
                if (check_soft) {
                        if (res_counter_check_under_soft_limit(&root_mem->res))
                                return total;
                } else if (mem_cgroup_check_under_limit(root_mem))
                        return 1 + total;
        }
        return total;
}

static int mem_cgroup_oom_lock_cb(struct mem_cgroup *mem, void *data)
{
        int *val = (int *)data;
        int x;
        /*
         * Logically, we can stop scanning immediately when we find
         * a memcg is already locked. But condidering unlock ops and
         * creation/removal of memcg, scan-all is simple operation.
         */
        x = atomic_inc_return(&mem->oom_lock);
        *val = max(x, *val);
        return 0;
}
/*
 * Check OOM-Killer is already running under our hierarchy.
 * If someone is running, return false.
 */
static bool mem_cgroup_oom_lock(struct mem_cgroup *mem)
{
        int lock_count = 0;

        mem_cgroup_walk_tree(mem, &lock_count, mem_cgroup_oom_lock_cb);

        if (lock_count == 1)
                return true;
        return false;
}

static int mem_cgroup_oom_unlock_cb(struct mem_cgroup *mem, void *data)
{
        /*
         * 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.
         */
        atomic_add_unless(&mem->oom_lock, -1, 0);
        return 0;
}

static void mem_cgroup_oom_unlock(struct mem_cgroup *mem)
{
        mem_cgroup_walk_tree(mem, NULL, mem_cgroup_oom_unlock_cb);
}

static DEFINE_MUTEX(memcg_oom_mutex);
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_mem = (struct mem_cgroup *)arg;
        struct oom_wait_info *oom_wait_info;

        oom_wait_info = container_of(wait, struct oom_wait_info, wait);

        if (oom_wait_info->mem == wake_mem)
                goto wakeup;
        /* if no hierarchy, no match */
        if (!oom_wait_info->mem->use_hierarchy || !wake_mem->use_hierarchy)
                return 0;
        /*
         * 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 (!css_is_ancestor(&oom_wait_info->mem->css, &wake_mem->css) &&
            !css_is_ancestor(&wake_mem->css, &oom_wait_info->mem->css))
                return 0;

wakeup:
        return autoremove_wake_function(wait, mode, sync, arg);
}

static void memcg_wakeup_oom(struct mem_cgroup *mem)
{
        /* for filtering, pass "mem" as argument. */
        __wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, mem);
}

static void memcg_oom_recover(struct mem_cgroup *mem)
{
        if (atomic_read(&mem->oom_lock))
                memcg_wakeup_oom(mem);
}

/*
 * try to call OOM killer. returns false if we should exit memory-reclaim loop.
 */
bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
{
        struct oom_wait_info owait;
        bool locked, need_to_kill;

        owait.mem = mem;
        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;
        /* At first, try to OOM lock hierarchy under mem.*/
        mutex_lock(&memcg_oom_mutex);
        locked = mem_cgroup_oom_lock(mem);
        /*
         * 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 || mem->oom_kill_disable)
                need_to_kill = false;
        if (locked)
                mem_cgroup_oom_notify(mem);
        mutex_unlock(&memcg_oom_mutex);

        if (need_to_kill) {
                finish_wait(&memcg_oom_waitq, &owait.wait);
                mem_cgroup_out_of_memory(mem, mask);
        } else {
                schedule();
                finish_wait(&memcg_oom_waitq, &owait.wait);
        }
        mutex_lock(&memcg_oom_mutex);
        mem_cgroup_oom_unlock(mem);
        memcg_wakeup_oom(mem);
        mutex_unlock(&memcg_oom_mutex);

        if (test_thread_flag(TIF_MEMDIE) || fatal_signal_pending(current))
                return false;
        /* Give chance to dying process */
        schedule_timeout(1);
        return true;
}

/*
 * Currently used to update mapped file statistics, but the routine can be
 * generalized to update other statistics as well.
 */
void mem_cgroup_update_file_mapped(struct page *page, int val)
{
        struct mem_cgroup *mem;
        struct page_cgroup *pc;

        pc = lookup_page_cgroup(page);
        if (unlikely(!pc))
                return;

        lock_page_cgroup(pc);
        mem = pc->mem_cgroup;
        if (!mem || !PageCgroupUsed(pc))
                goto done;

        /*
         * Preemption is already disabled. We can use __this_cpu_xxx
         */
        if (val > 0) {
                __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
                SetPageCgroupFileMapped(pc);
        } else {
                __this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
                ClearPageCgroupFileMapped(pc);
        }

done:
        unlock_page_cgroup(pc);
}

/*
 * 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_SIZE     (32 * PAGE_SIZE)
struct memcg_stock_pcp {
        struct mem_cgroup *cached; /* this never be root cgroup */
        int charge;
        struct work_struct work;
};
static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock);
static atomic_t memcg_drain_count;

/*
 * Try to consume stocked charge on this cpu. If success, PAGE_SIZE 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 *mem)
{
        struct memcg_stock_pcp *stock;
        bool ret = true;

        stock = &get_cpu_var(memcg_stock);
        if (mem == stock->cached && stock->charge)
                stock->charge -= PAGE_SIZE;
        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->charge) {
                res_counter_uncharge(&old->res, stock->charge);
                if (do_swap_account)
                        res_counter_uncharge(&old->memsw, stock->charge);
        }
        stock->cached = NULL;
        stock->charge = 0;
}

/*
 * 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);
}

/*
 * 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 *mem, int val)
{
        struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock);

        if (stock->cached != mem) { /* reset if necessary */
                drain_stock(stock);
                stock->cached = mem;
        }
        stock->charge += val;
        put_cpu_var(memcg_stock);
}

/*
 * 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(void)
{
        int cpu;
        /* This function is for scheduling "drain" in asynchronous way.
         * The result of "drain" is not directly handled by callers. Then,
         * if someone is calling drain, we don't have to call drain more.
         * Anyway, WORK_STRUCT_PENDING check in queue_work_on() will catch if
         * there is a race. We just do loose check here.
         */
        if (atomic_read(&memcg_drain_count))
                return;
        /* Notify other cpus that system-wide "drain" is running */
        atomic_inc(&memcg_drain_count);
        get_online_cpus();
        for_each_online_cpu(cpu) {
                struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
                schedule_work_on(cpu, &stock->work);
        }
        put_online_cpus();
        atomic_dec(&memcg_drain_count);
        /* We don't wait for flush_work */
}

/* This is a synchronous drain interface. */
static void drain_all_stock_sync(void)
{
        /* called when force_empty is called */
        atomic_inc(&memcg_drain_count);
        schedule_on_each_cpu(drain_local_stock);
        atomic_dec(&memcg_drain_count);
}

static int __cpuinit memcg_stock_cpu_callback(struct notifier_block *nb,
                                        unsigned long action,
                                        void *hcpu)
{
        int cpu = (unsigned long)hcpu;
        struct memcg_stock_pcp *stock;

        if (action != CPU_DEAD)
                return NOTIFY_OK;
        stock = &per_cpu(memcg_stock, cpu);
        drain_stock(stock);
        return NOTIFY_OK;
}

/*
 * Unlike exported interface, "oom" parameter is added. if oom==true,
 * oom-killer can be invoked.
 */
static int __mem_cgroup_try_charge(struct mm_struct *mm,
                        gfp_t gfp_mask, struct mem_cgroup **memcg, bool oom)
{
        struct mem_cgroup *mem, *mem_over_limit;
        int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
        struct res_counter *fail_res;
        int csize = CHARGE_SIZE;

        /*
         * 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 init_mm (happens for pagecache usage).
         */
        mem = *memcg;
        if (likely(!mem)) {
                mem = try_get_mem_cgroup_from_mm(mm);
                *memcg = mem;
        } else {
                css_get(&mem->css);
        }
        if (unlikely(!mem))
                return 0;

        VM_BUG_ON(css_is_removed(&mem->css));
        if (mem_cgroup_is_root(mem))
                goto done;

        while (1) {
                int ret = 0;
                unsigned long flags = 0;

                if (consume_stock(mem))
                        goto done;

                ret = res_counter_charge(&mem->res, csize, &fail_res);
                if (likely(!ret)) {
                        if (!do_swap_account)
                                break;
                        ret = res_counter_charge(&mem->memsw, csize, &fail_res);
                        if (likely(!ret))
                                break;
                        /* mem+swap counter fails */
                        res_counter_uncharge(&mem->res, csize);
                        flags |= MEM_CGROUP_RECLAIM_NOSWAP;
                        mem_over_limit = mem_cgroup_from_res_counter(fail_res,
                                                                        memsw);
                } else
                        /* mem counter fails */
                        mem_over_limit = mem_cgroup_from_res_counter(fail_res,
                                                                        res);

                /* reduce request size and retry */
                if (csize > PAGE_SIZE) {
                        csize = PAGE_SIZE;
                        continue;
                }
                if (!(gfp_mask & __GFP_WAIT))
                        goto nomem;

                ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,
                                                gfp_mask, flags);
                if (ret)
                        continue;

                /*
                 * try_to_free_mem_cgroup_pages() might not give us a full
                 * picture of reclaim. Some pages are reclaimed and might be
                 * moved to swap cache or just unmapped from the cgroup.
                 * Check the limit again to see if the reclaim reduced the
                 * current usage of the cgroup before giving up
                 *
                 */
                if (mem_cgroup_check_under_limit(mem_over_limit))
                        continue;

                /* try to avoid oom while someone is moving charge */
                if (mc.moving_task && current != mc.moving_task) {
                        struct mem_cgroup *from, *to;
                        bool do_continue = false;
                        /*
                         * There is a small race that "from" or "to" can be
                         * freed by rmdir, so we use css_tryget().
                         */
                        from = mc.from;
                        to = mc.to;
                        if (from && css_tryget(&from->css)) {
                                if (mem_over_limit->use_hierarchy)
                                        do_continue = css_is_ancestor(
                                                        &from->css,
                                                        &mem_over_limit->css);
                                else
                                        do_continue = (from == mem_over_limit);
                                css_put(&from->css);
                        }
                        if (!do_continue && to && css_tryget(&to->css)) {
                                if (mem_over_limit->use_hierarchy)
                                        do_continue = css_is_ancestor(
                                                        &to->css,
                                                        &mem_over_limit->css);
                                else
                                        do_continue = (to == mem_over_limit);
                                css_put(&to->css);
                        }
                        if (do_continue) {
                                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);
                                continue;
                        }
                }

                if (!nr_retries--) {
                        if (!oom)
                                goto nomem;
                        if (mem_cgroup_handle_oom(mem_over_limit, gfp_mask)) {
                                nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
                                continue;
                        }
                        /* When we reach here, current task is dying .*/
                        css_put(&mem->css);
                        goto bypass;
                }
        }
        if (csize > PAGE_SIZE)
                refill_stock(mem, csize - PAGE_SIZE);
done:
        return 0;
nomem:
        css_put(&mem->css);
        return -ENOMEM;
bypass:
        *memcg = NULL;
        return 0;
}

/*
 * 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 *mem,
                                                        unsigned long count)
{
        if (!mem_cgroup_is_root(mem)) {
                res_counter_uncharge(&mem->res, PAGE_SIZE * count);
                if (do_swap_account)
                        res_counter_uncharge(&mem->memsw, PAGE_SIZE * count);
                VM_BUG_ON(test_bit(CSS_ROOT, &mem->css.flags));
                WARN_ON_ONCE(count > INT_MAX);
                __css_put(&mem->css, (int)count);
        }
        /* we don't need css_put for root */
}

static void mem_cgroup_cancel_charge(struct mem_cgroup *mem)
{
        __mem_cgroup_cancel_charge(mem, 1);
}

/*
 * A helper function to get mem_cgroup from ID. must be called under
 * rcu_read_lock(). The caller must check css_is_removed() or some if
 * it's concern. (dropping refcnt from swap can be called against removed
 * memcg.)
 */
static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
{
        struct cgroup_subsys_state *css;

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

struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
{
        struct mem_cgroup *mem = 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)) {
                mem = pc->mem_cgroup;
                if (mem && !css_tryget(&mem->css))
                        mem = NULL;
        } else if (PageSwapCache(page)) {
                ent.val = page_private(page);
                id = lookup_swap_cgroup(ent);
                rcu_read_lock();
                mem = mem_cgroup_lookup(id);
                if (mem && !css_tryget(&mem->css))
                        mem = NULL;
                rcu_read_unlock();
        }
        unlock_page_cgroup(pc);
        return mem;
}

/*
 * commit a charge got by __mem_cgroup_try_charge() and makes page_cgroup to be
 * USED state. If already USED, uncharge and return.
 */

static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
                                     struct page_cgroup *pc,
                                     enum charge_type ctype)
{
        /* try_charge() can return NULL to *memcg, taking care of it. */
        if (!mem)
                return;

        lock_page_cgroup(pc);
        if (unlikely(PageCgroupUsed(pc))) {
                unlock_page_cgroup(pc);
                mem_cgroup_cancel_charge(mem);
                return;
        }

        pc->mem_cgroup = mem;
        /*
         * 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();
        switch (ctype) {
        case MEM_CGROUP_CHARGE_TYPE_CACHE:
        case MEM_CGROUP_CHARGE_TYPE_SHMEM:
                SetPageCgroupCache(pc);
                SetPageCgroupUsed(pc);
                break;
        case MEM_CGROUP_CHARGE_TYPE_MAPPED:
                ClearPageCgroupCache(pc);
                SetPageCgroupUsed(pc);
                break;
        default:
                break;
        }

        mem_cgroup_charge_statistics(mem, pc, true);

        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(mem, pc->page);
}

/**
 * __mem_cgroup_move_account - move account of the page
 * @pc: page_cgroup of the page.
 * @from: mem_cgroup which the page is moved from.
 * @to: mem_cgroup which the page is moved to. @from != @to.
 * @uncharge: whether we should call uncharge and css_put against @from.
 *
 * The caller must confirm following.
 * - page is not on LRU (isolate_page() is useful.)
 * - the pc is locked, used, and ->mem_cgroup points to @from.
 *
 * This function doesn't do "charge" nor css_get to new cgroup. It should be
 * done by a caller(__mem_cgroup_try_charge would be usefull). If @uncharge is
 * true, this function does "uncharge" from old cgroup, but it doesn't if
 * @uncharge is false, so a caller should do "uncharge".
 */

static void __mem_cgroup_move_account(struct page_cgroup *pc,
        struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
{
        VM_BUG_ON(from == to);
        VM_BUG_ON(PageLRU(pc->page));
        VM_BUG_ON(!PageCgroupLocked(pc));
        VM_BUG_ON(!PageCgroupUsed(pc));
        VM_BUG_ON(pc->mem_cgroup != from);

        if (PageCgroupFileMapped(pc)) {
                /* 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, pc, false);
        if (uncharge)
                /* This is not "cancel", but cancel_charge does all we need. */
                mem_cgroup_cancel_charge(from);

        /* caller should have done css_get */
        pc->mem_cgroup = to;
        mem_cgroup_charge_statistics(to, pc, true);
        /*
         * 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
         * garanteed that "to" is never removed. So, we don't check rmdir
         * status here.
         */
}

/*
 * check whether the @pc is valid for moving account and call
 * __mem_cgroup_move_account()
 */
static int mem_cgroup_move_account(struct page_cgroup *pc,
                struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
{
        int ret = -EINVAL;
        lock_page_cgroup(pc);
        if (PageCgroupUsed(pc) && pc->mem_cgroup == from) {
                __mem_cgroup_move_account(pc, from, to, uncharge);
                ret = 0;
        }
        unlock_page_cgroup(pc);
        /*
         * check events
         */
        memcg_check_events(to, pc->page);
        memcg_check_events(from, pc->page);
        return ret;
}

/*
 * move charges to its parent.
 */

static int mem_cgroup_move_parent(struct page_cgroup *pc,
                                  struct mem_cgroup *child,
                                  gfp_t gfp_mask)
{
        struct page *page = pc->page;
        struct cgroup *cg = child->css.cgroup;
        struct cgroup *pcg = cg->parent;
        struct mem_cgroup *parent;
        int ret;

        /* Is ROOT ? */
        if (!pcg)
                return -EINVAL;

        ret = -EBUSY;
        if (!get_page_unless_zero(page))
                goto out;
        if (isolate_lru_page(page))
                goto put;

        parent = mem_cgroup_from_cont(pcg);
        ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false);
        if (ret || !parent)
                goto put_back;

        ret = mem_cgroup_move_account(pc, child, parent, true);
        if (ret)
                mem_cgroup_cancel_charge(parent);
put_back:
        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)
{
        struct mem_cgroup *mem;
        struct page_cgroup *pc;
        int ret;

        pc = lookup_page_cgroup(page);
        /* can happen at boot */
        if (unlikely(!pc))
                return 0;
        prefetchw(pc);

        mem = memcg;
        ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, true);
        if (ret || !mem)
                return ret;

        __mem_cgroup_commit_charge(mem, pc, ctype);