// SPDX-License-Identifier: GPL-2.0-or-later
/* memcontrol.c - Memory Controller
 *
 * Copyright IBM Corporation, 2007
 * Author Balbir Singh <balbir@linux.vnet.ibm.com>
 *
 * Copyright 2007 OpenVZ SWsoft Inc
 * Author: Pavel Emelianov <xemul@openvz.org>
 *
 * Memory thresholds
 * Copyright (C) 2009 Nokia Corporation
 * Author: Kirill A. Shutemov
 *
 * Kernel Memory Controller
 * Copyright (C) 2012 Parallels Inc. and Google Inc.
 * Authors: Glauber Costa and Suleiman Souhlal
 *
 * Native page reclaim
 * Charge lifetime sanitation
 * Lockless page tracking & accounting
 * Unified hierarchy configuration model
 * Copyright (C) 2015 Red Hat, Inc., Johannes Weiner
 *
 * Per memcg lru locking
 * Copyright (C) 2020 Alibaba, Inc, Alex Shi
 */

#include <linux/page_counter.h>
#include <linux/memcontrol.h>
#include <linux/cgroup.h>
#include <linux/pagewalk.h>
#include <linux/sched/mm.h>
#include <linux/shmem_fs.h>
#include <linux/hugetlb.h>
#include <linux/pagemap.h>
#include <linux/vm_event_item.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/poll.h>
#include <linux/sort.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/vmpressure.h>
#include <linux/mm_inline.h>
#include <linux/swap_cgroup.h>
#include <linux/cpu.h>
#include <linux/oom.h>
#include <linux/lockdep.h>
#include <linux/file.h>
#include <linux/tracehook.h>
#include <linux/psi.h>
#include <linux/seq_buf.h>
#include "internal.h"
#include <net/sock.h>
#include <net/ip.h>
#include "slab.h"

#include <linux/uaccess.h>

#include <trace/events/vmscan.h>

struct cgroup_subsys memory_cgrp_subsys __read_mostly;
EXPORT_SYMBOL(memory_cgrp_subsys);

struct mem_cgroup *root_mem_cgroup __read_mostly;

/* Active memory cgroup to use from an interrupt context */
DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
EXPORT_PER_CPU_SYMBOL_GPL(int_active_memcg);

/* Socket memory accounting disabled? */
static bool cgroup_memory_nosocket __ro_after_init;

/* Kernel memory accounting disabled? */
bool cgroup_memory_nokmem __ro_after_init;

/* Whether the swap controller is active */
#ifdef CONFIG_MEMCG_SWAP
bool cgroup_memory_noswap __ro_after_init;
#else
#define cgroup_memory_noswap            1
#endif

#ifdef CONFIG_CGROUP_WRITEBACK
static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq);
#endif

/* Whether legacy memory+swap accounting is active */
static bool do_memsw_account(void)
{
        return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_noswap;
}

#define THRESHOLDS_EVENTS_TARGET 128
#define SOFTLIMIT_EVENTS_TARGET 1024

/*
 * Cgroups above their limits are maintained in a RB-Tree, independent of
 * their hierarchy representation
 */

struct mem_cgroup_tree_per_node {
        struct rb_root rb_root;
        struct rb_node *rb_rightmost;
        spinlock_t lock;
};

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;

/* for OOM */
struct mem_cgroup_eventfd_list {
        struct list_head list;
        struct eventfd_ctx *eventfd;
};

/*
 * cgroup_event represents events which userspace want to receive.
 */
struct mem_cgroup_event {
        /*
         * memcg which the event belongs to.
         */
        struct mem_cgroup *memcg;
        /*
         * eventfd to signal userspace about the event.
         */
        struct eventfd_ctx *eventfd;
        /*
         * Each of these stored in a list by the cgroup.
         */
        struct list_head list;
        /*
         * register_event() callback will be used to add new userspace
         * waiter for changes related to this event.  Use eventfd_signal()
         * on eventfd to send notification to userspace.
         */
        int (*register_event)(struct mem_cgroup *memcg,
                              struct eventfd_ctx *eventfd, const char *args);
        /*
         * unregister_event() callback will be called when userspace closes
         * the eventfd or on cgroup removing.  This callback must be set,
         * if you want provide notification functionality.
         */
        void (*unregister_event)(struct mem_cgroup *memcg,
                                 struct eventfd_ctx *eventfd);
        /*
         * All fields below needed to unregister event when
         * userspace closes eventfd.
         */
        poll_table pt;
        wait_queue_head_t *wqh;
        wait_queue_entry_t wait;
        struct work_struct remove;
};

static void mem_cgroup_threshold(struct mem_cgroup *memcg);
static void mem_cgroup_oom_notify(struct mem_cgroup *memcg);

/* Stuffs for move charges at task migration. */
/*
 * Types of charges to be moved.
 */
#define MOVE_ANON       0x1U
#define MOVE_FILE       0x2U
#define MOVE_MASK       (MOVE_ANON | MOVE_FILE)

/* "mc" and its members are protected by cgroup_mutex */
static struct move_charge_struct {
        spinlock_t        lock; /* for from, to */
        struct mm_struct  *mm;
        struct mem_cgroup *from;
        struct mem_cgroup *to;
        unsigned long flags;
        unsigned long precharge;
        unsigned long moved_charge;
        unsigned long moved_swap;
        struct task_struct *moving_task;        /* a task moving charges */
        wait_queue_head_t waitq;                /* a waitq for other context */
} mc = {
        .lock = __SPIN_LOCK_UNLOCKED(mc.lock),
        .waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq),
};

/*
 * 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

/* for encoding cft->private value on file */
enum res_type {
        _MEM,
        _MEMSWAP,
        _OOM_TYPE,
        _KMEM,
        _TCP,
};

#define MEMFILE_PRIVATE(x, val) ((x) << 16 | (val))
#define MEMFILE_TYPE(val)       ((val) >> 16 & 0xffff)
#define MEMFILE_ATTR(val)       ((val) & 0xffff)
/* Used for OOM notifier */
#define OOM_CONTROL             (0)

/*
 * 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 should_force_charge(void)
{
        return tsk_is_oom_victim(current) || fatal_signal_pending(current) ||
                (current->flags & PF_EXITING);
}

/* Some nice accessors for the vmpressure. */
struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg)
{
        if (!memcg)
                memcg = root_mem_cgroup;
        return &memcg->vmpressure;
}

struct cgroup_subsys_state *vmpressure_to_css(struct vmpressure *vmpr)
{
        return &container_of(vmpr, struct mem_cgroup, vmpressure)->css;
}

#ifdef CONFIG_MEMCG_KMEM
extern spinlock_t css_set_lock;

bool mem_cgroup_kmem_disabled(void)
{
        return cgroup_memory_nokmem;
}

static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg,
                                      unsigned int nr_pages);

static void obj_cgroup_release(struct percpu_ref *ref)
{
        struct obj_cgroup *objcg = container_of(ref, struct obj_cgroup, refcnt);
        unsigned int nr_bytes;
        unsigned int nr_pages;
        unsigned long flags;

        /*
         * At this point all allocated objects are freed, and
         * objcg->nr_charged_bytes can't have an arbitrary byte value.
         * However, it can be PAGE_SIZE or (x * PAGE_SIZE).
         *
         * The following sequence can lead to it:
         * 1) CPU0: objcg == stock->cached_objcg
         * 2) CPU1: we do a small allocation (e.g. 92 bytes),
         *          PAGE_SIZE bytes are charged
         * 3) CPU1: a process from another memcg is allocating something,
         *          the stock if flushed,
         *          objcg->nr_charged_bytes = PAGE_SIZE - 92
         * 5) CPU0: we do release this object,
         *          92 bytes are added to stock->nr_bytes
         * 6) CPU0: stock is flushed,
         *          92 bytes are added to objcg->nr_charged_bytes
         *
         * In the result, nr_charged_bytes == PAGE_SIZE.
         * This page will be uncharged in obj_cgroup_release().
         */
        nr_bytes = atomic_read(&objcg->nr_charged_bytes);
        WARN_ON_ONCE(nr_bytes & (PAGE_SIZE - 1));
        nr_pages = nr_bytes >> PAGE_SHIFT;

        if (nr_pages)
                obj_cgroup_uncharge_pages(objcg, nr_pages);

        spin_lock_irqsave(&css_set_lock, flags);
        list_del(&objcg->list);
        spin_unlock_irqrestore(&css_set_lock, flags);

        percpu_ref_exit(ref);
        kfree_rcu(objcg, rcu);
}

static struct obj_cgroup *obj_cgroup_alloc(void)
{
        struct obj_cgroup *objcg;
        int ret;

        objcg = kzalloc(sizeof(struct obj_cgroup), GFP_KERNEL);
        if (!objcg)
                return NULL;

        ret = percpu_ref_init(&objcg->refcnt, obj_cgroup_release, 0,
                              GFP_KERNEL);
        if (ret) {
                kfree(objcg);
                return NULL;
        }
        INIT_LIST_HEAD(&objcg->list);
        return objcg;
}

static void memcg_reparent_objcgs(struct mem_cgroup *memcg,
                                  struct mem_cgroup *parent)
{
        struct obj_cgroup *objcg, *iter;

        objcg = rcu_replace_pointer(memcg->objcg, NULL, true);

        spin_lock_irq(&css_set_lock);

        /* 1) Ready to reparent active objcg. */
        list_add(&objcg->list, &memcg->objcg_list);
        /* 2) Reparent active objcg and already reparented objcgs to parent. */
        list_for_each_entry(iter, &memcg->objcg_list, list)
                WRITE_ONCE(iter->memcg, parent);
        /* 3) Move already reparented objcgs to the parent's list */
        list_splice(&memcg->objcg_list, &parent->objcg_list);

        spin_unlock_irq(&css_set_lock);

        percpu_ref_kill(&objcg->refcnt);
}

/*
 * This will be used as a shrinker list's index.
 * The main reason for not using cgroup id for this:
 *  this works better in sparse environments, where we have a lot of memcgs,
 *  but only a few kmem-limited. Or also, if we have, for instance, 200
 *  memcgs, and none but the 200th is kmem-limited, we'd have to have a
 *  200 entry array for that.
 *
 * The current size of the caches array is stored in memcg_nr_cache_ids. It
 * will double each time we have to increase it.
 */
static DEFINE_IDA(memcg_cache_ida);
int memcg_nr_cache_ids;

/* Protects memcg_nr_cache_ids */
static DECLARE_RWSEM(memcg_cache_ids_sem);

void memcg_get_cache_ids(void)
{
        down_read(&memcg_cache_ids_sem);
}

void memcg_put_cache_ids(void)
{
        up_read(&memcg_cache_ids_sem);
}

/*
 * MIN_SIZE is different than 1, because we would like to avoid going through
 * the alloc/free process all the time. In a small machine, 4 kmem-limited
 * cgroups is a reasonable guess. In the future, it could be a parameter or
 * tunable, but that is strictly not necessary.
 *
 * MAX_SIZE should be as large as the number of cgrp_ids. Ideally, we could get
 * this constant directly from cgroup, but it is understandable that this is
 * better kept as an internal representation in cgroup.c. In any case, the
 * cgrp_id space is not getting any smaller, and we don't have to necessarily
 * increase ours as well if it increases.
 */
#define MEMCG_CACHES_MIN_SIZE 4
#define MEMCG_CACHES_MAX_SIZE MEM_CGROUP_ID_MAX

/*
 * A lot of the calls to the cache allocation functions are expected to be
 * inlined by the compiler. Since the calls to memcg_slab_pre_alloc_hook() are
 * conditional to this static branch, we'll have to allow modules that does
 * kmem_cache_alloc and the such to see this symbol as well
 */
DEFINE_STATIC_KEY_FALSE(memcg_kmem_enabled_key);
EXPORT_SYMBOL(memcg_kmem_enabled_key);
#endif

/**
 * mem_cgroup_css_from_page - css of the memcg associated with a page
 * @page: page of interest
 *
 * If memcg is bound to the default hierarchy, css of the memcg associated
 * with @page is returned.  The returned css remains associated with @page
 * until it is released.
 *
 * If memcg is bound to a traditional hierarchy, the css of root_mem_cgroup
 * is returned.
 */
struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page)
{
        struct mem_cgroup *memcg;

        memcg = page_memcg(page);

        if (!memcg || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
                memcg = root_mem_cgroup;

        return &memcg->css;
}

/**
 * page_cgroup_ino - return inode number of the memcg a page is charged to
 * @page: the page
 *
 * Look up the closest online ancestor of the memory cgroup @page is charged to
 * and return its inode number or 0 if @page is not charged to any cgroup. It
 * is safe to call this function without holding a reference to @page.
 *
 * Note, this function is inherently racy, because there is nothing to prevent
 * the cgroup inode from getting torn down and potentially reallocated a moment
 * after page_cgroup_ino() returns, so it only should be used by callers that
 * do not care (such as procfs interfaces).
 */
ino_t page_cgroup_ino(struct page *page)
{
        struct mem_cgroup *memcg;
        unsigned long ino = 0;

        rcu_read_lock();
        memcg = page_memcg_check(page);

        while (memcg && !(memcg->css.flags & CSS_ONLINE))
                memcg = parent_mem_cgroup(memcg);
        if (memcg)
                ino = cgroup_ino(memcg->css.cgroup);
        rcu_read_unlock();
        return ino;
}

static struct mem_cgroup_per_node *
mem_cgroup_page_nodeinfo(struct mem_cgroup *memcg, struct page *page)
{
        int nid = page_to_nid(page);

        return memcg->nodeinfo[nid];
}

static struct mem_cgroup_tree_per_node *
soft_limit_tree_node(int nid)
{
        return soft_limit_tree.rb_tree_per_node[nid];
}

static struct mem_cgroup_tree_per_node *
soft_limit_tree_from_page(struct page *page)
{
        int nid = page_to_nid(page);

        return soft_limit_tree.rb_tree_per_node[nid];
}

static void __mem_cgroup_insert_exceeded(struct mem_cgroup_per_node *mz,
                                         struct mem_cgroup_tree_per_node *mctz,
                                         unsigned long new_usage_in_excess)
{
        struct rb_node **p = &mctz->rb_root.rb_node;
        struct rb_node *parent = NULL;
        struct mem_cgroup_per_node *mz_node;
        bool rightmost = true;

        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_node,
                                        tree_node);
                if (mz->usage_in_excess < mz_node->usage_in_excess) {
                        p = &(*p)->rb_left;
                        rightmost = false;
                } else {
                        p = &(*p)->rb_right;
                }
        }

        if (rightmost)
                mctz->rb_rightmost = &mz->tree_node;

        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_per_node *mz,
                                         struct mem_cgroup_tree_per_node *mctz)
{
        if (!mz->on_tree)
                return;

        if (&mz->tree_node == mctz->rb_rightmost)
                mctz->rb_rightmost = rb_prev(&mz->tree_node);

        rb_erase(&mz->tree_node, &mctz->rb_root);
        mz->on_tree = false;
}

static void mem_cgroup_remove_exceeded(struct mem_cgroup_per_node *mz,
                                       struct mem_cgroup_tree_per_node *mctz)
{
        unsigned long flags;

        spin_lock_irqsave(&mctz->lock, flags);
        __mem_cgroup_remove_exceeded(mz, mctz);
        spin_unlock_irqrestore(&mctz->lock, flags);
}

static unsigned long soft_limit_excess(struct mem_cgroup *memcg)
{
        unsigned long nr_pages = page_counter_read(&memcg->memory);
        unsigned long soft_limit = READ_ONCE(memcg->soft_limit);
        unsigned long excess = 0;

        if (nr_pages > soft_limit)
                excess = nr_pages - soft_limit;

        return excess;
}

static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
{
        unsigned long excess;
        struct mem_cgroup_per_node *mz;
        struct mem_cgroup_tree_per_node *mctz;

        mctz = soft_limit_tree_from_page(page);
        if (!mctz)
                return;
        /*
         * 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_page_nodeinfo(memcg, page);
                excess = soft_limit_excess(memcg);
                /*
                 * We have to update the tree if mz is on RB-tree or
                 * mem is over its softlimit.
                 */
                if (excess || mz->on_tree) {
                        unsigned long flags;

                        spin_lock_irqsave(&mctz->lock, flags);
                        /* if on-tree, remove it */
                        if (mz->on_tree)
                                __mem_cgroup_remove_exceeded(mz, mctz);
                        /*
                         * Insert again. mz->usage_in_excess will be updated.
                         * If excess is 0, no tree ops.
                         */
                        __mem_cgroup_insert_exceeded(mz, mctz, excess);
                        spin_unlock_irqrestore(&mctz->lock, flags);
                }
        }
}

static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
{
        struct mem_cgroup_tree_per_node *mctz;
        struct mem_cgroup_per_node *mz;
        int nid;

        for_each_node(nid) {
                mz = memcg->nodeinfo[nid];
                mctz = soft_limit_tree_node(nid);
                if (mctz)
                        mem_cgroup_remove_exceeded(mz, mctz);
        }
}

static struct mem_cgroup_per_node *
__mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz)
{
        struct mem_cgroup_per_node *mz;

retry:
        mz = NULL;
        if (!mctz->rb_rightmost)
                goto done;              /* Nothing to reclaim from */

        mz = rb_entry(mctz->rb_rightmost,
                      struct mem_cgroup_per_node, 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, mctz);
        if (!soft_limit_excess(mz->memcg) ||
            !css_tryget(&mz->memcg->css))
                goto retry;
done:
        return mz;
}

static struct mem_cgroup_per_node *
mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz)
{
        struct mem_cgroup_per_node *mz;

        spin_lock_irq(&mctz->lock);
        mz = __mem_cgroup_largest_soft_limit_node(mctz);
        spin_unlock_irq(&mctz->lock);
        return mz;
}

/**
 * __mod_memcg_state - update cgroup memory statistics
 * @memcg: the memory cgroup
 * @idx: the stat item - can be enum memcg_stat_item or enum node_stat_item
 * @val: delta to add to the counter, can be negative
 */
void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val)
{
        if (mem_cgroup_disabled())
                return;

        __this_cpu_add(memcg->vmstats_percpu->state[idx], val);
        cgroup_rstat_updated(memcg->css.cgroup, smp_processor_id());
}

/* idx can be of type enum memcg_stat_item or node_stat_item. */
static unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
{
        long x = READ_ONCE(memcg->vmstats.state[idx]);
#ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
#endif
        return x;
}

/* idx can be of type enum memcg_stat_item or node_stat_item. */
static unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx)
{
        long x = 0;
        int cpu;

        for_each_possible_cpu(cpu)
                x += per_cpu(memcg->vmstats_percpu->state[idx], cpu);
#ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
#endif
        return x;
}

static struct mem_cgroup_per_node *
parent_nodeinfo(struct mem_cgroup_per_node *pn, int nid)
{
        struct mem_cgroup *parent;

        parent = parent_mem_cgroup(pn->memcg);
        if (!parent)
                return NULL;
        return parent->nodeinfo[nid];
}

void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx,
                              int val)
{
        struct mem_cgroup_per_node *pn;
        struct mem_cgroup *memcg;
        long x, threshold = MEMCG_CHARGE_BATCH;

        pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
        memcg = pn->memcg;

        /* Update memcg */
        __mod_memcg_state(memcg, idx, val);

        /* Update lruvec */
        __this_cpu_add(pn->lruvec_stat_local->count[idx], val);

        if (vmstat_item_in_bytes(idx))
                threshold <<= PAGE_SHIFT;

        x = val + __this_cpu_read(pn->lruvec_stat_cpu->count[idx]);
        if (unlikely(abs(x) > threshold)) {
                pg_data_t *pgdat = lruvec_pgdat(lruvec);
                struct mem_cgroup_per_node *pi;

                for (pi = pn; pi; pi = parent_nodeinfo(pi, pgdat->node_id))
                        atomic_long_add(x, &pi->lruvec_stat[idx]);
                x = 0;
        }
        __this_cpu_write(pn->lruvec_stat_cpu->count[idx], x);
}

/**
 * __mod_lruvec_state - update lruvec memory statistics
 * @lruvec: the lruvec
 * @idx: the stat item
 * @val: delta to add to the counter, can be negative
 *
 * The lruvec is the intersection of the NUMA node and a cgroup. This
 * function updates the all three counters that are affected by a
 * change of state at this level: per-node, per-cgroup, per-lruvec.
 */
void __mod_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx,
                        int val)
{
        /* Update node */
        __mod_node_page_state(lruvec_pgdat(lruvec), idx, val);

        /* Update memcg and lruvec */
        if (!mem_cgroup_disabled())
                __mod_memcg_lruvec_state(lruvec, idx, val);
}

void __mod_lruvec_page_state(struct page *page, enum node_stat_item idx,
                             int val)
{
        struct page *head = compound_head(page); /* rmap on tail pages */
        struct mem_cgroup *memcg;
        pg_data_t *pgdat = page_pgdat(page);
        struct lruvec *lruvec;

        rcu_read_lock();
        memcg = page_memcg(head);
        /* Untracked pages have no memcg, no lruvec. Update only the node */
        if (!memcg) {
                rcu_read_unlock();
                __mod_node_page_state(pgdat, idx, val);
                return;
        }

        lruvec = mem_cgroup_lruvec(memcg, pgdat);
        __mod_lruvec_state(lruvec, idx, val);
        rcu_read_unlock();
}
EXPORT_SYMBOL(__mod_lruvec_page_state);

void __mod_lruvec_kmem_state(void *p, enum node_stat_item idx, int val)
{
        pg_data_t *pgdat = page_pgdat(virt_to_page(p));
        struct mem_cgroup *memcg;
        struct lruvec *lruvec;

        rcu_read_lock();
        memcg = mem_cgroup_from_obj(p);

        /*
         * Untracked pages have no memcg, no lruvec. Update only the
         * node. If we reparent the slab objects to the root memcg,
         * when we free the slab object, we need to update the per-memcg
         * vmstats to keep it correct for the root memcg.
         */
        if (!memcg) {
                __mod_node_page_state(pgdat, idx, val);
        } else {
                lruvec = mem_cgroup_lruvec(memcg, pgdat);
                __mod_lruvec_state(lruvec, idx, val);
        }
        rcu_read_unlock();
}

/*
 * mod_objcg_mlstate() may be called with irq enabled, so
 * mod_memcg_lruvec_state() should be used.
 */
static inline void mod_objcg_mlstate(struct obj_cgroup *objcg,
                                     struct pglist_data *pgdat,
                                     enum node_stat_item idx, int nr)
{
        struct mem_cgroup *memcg;
        struct lruvec *lruvec;

        rcu_read_lock();
        memcg = obj_cgroup_memcg(objcg);
        lruvec = mem_cgroup_lruvec(memcg, pgdat);
        mod_memcg_lruvec_state(lruvec, idx, nr);
        rcu_read_unlock();
}

/**
 * __count_memcg_events - account VM events in a cgroup
 * @memcg: the memory cgroup
 * @idx: the event item
 * @count: the number of events that occurred
 */
void __count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx,
                          unsigned long count)
{
        if (mem_cgroup_disabled())
                return;

        __this_cpu_add(memcg->vmstats_percpu->events[idx], count);
        cgroup_rstat_updated(memcg->css.cgroup, smp_processor_id());
}

static unsigned long memcg_events(struct mem_cgroup *memcg, int event)
{
        return READ_ONCE(memcg->vmstats.events[event]);
}

static unsigned long memcg_events_local(struct mem_cgroup *memcg, int event)
{
        long x = 0;
        int cpu;

        for_each_possible_cpu(cpu)
                x += per_cpu(memcg->vmstats_percpu->events[event], cpu);
        return x;
}

static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
                                         struct page *page,
                                         int nr_pages)
{
        /* pagein of a big page is an event. So, ignore page size */
        if (nr_pages > 0)
                __count_memcg_events(memcg, PGPGIN, 1);
        else {
                __count_memcg_events(memcg, PGPGOUT, 1);
                nr_pages = -nr_pages; /* for event */
        }

        __this_cpu_add(memcg->vmstats_percpu->nr_page_events, nr_pages);
}

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->vmstats_percpu->nr_page_events);
        next = __this_cpu_read(memcg->vmstats_percpu->targets[target]);
        /* from time_after() in jiffies.h */
        if ((long)(next - 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;
                default:
                        break;
                }
                __this_cpu_write(memcg->vmstats_percpu->targets[target], next);
                return true;
        }
        return false;
}

/*
 * Check events in order.
 *
 */
static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
{
        /* threshold event is triggered in finer grain than soft limit */
        if (unlikely(mem_cgroup_event_ratelimit(memcg,
                                                MEM_CGROUP_TARGET_THRESH))) {
                bool do_softlimit;

                do_softlimit = mem_cgroup_event_ratelimit(memcg,
                                                MEM_CGROUP_TARGET_SOFTLIMIT);
                mem_cgroup_threshold(memcg);
                if (unlikely(do_softlimit))
                        mem_cgroup_update_tree(memcg, page);
        }
}

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

        return mem_cgroup_from_css(task_css(p, memory_cgrp_id));
}
EXPORT_SYMBOL(mem_cgroup_from_task);

static __always_inline struct mem_cgroup *active_memcg(void)
{
        if (in_interrupt())
                return this_cpu_read(int_active_memcg);
        else
                return current->active_memcg;
}

/**
 * get_mem_cgroup_from_mm: Obtain a reference on given mm_struct's memcg.
 * @mm: mm from which memcg should be extracted. It can be NULL.
 *
 * Obtain a reference on mm->memcg and returns it if successful. If mm
 * is NULL, then the memcg is chosen as follows:
 * 1) The active memcg, if set.
 * 2) current->mm->memcg, if available
 * 3) root memcg
 * If mem_cgroup is disabled, NULL is returned.
 */
struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
{
        struct mem_cgroup *memcg;

        if (mem_cgroup_disabled())
                return NULL;

        /*
         * Page cache insertions can happen without an
         * actual mm context, e.g. during disk probing
         * on boot, loopback IO, acct() writes etc.
         *
         * No need to css_get on root memcg as the reference
         * counting is disabled on the root level in the
         * cgroup core. See CSS_NO_REF.
         */
        if (unlikely(!mm)) {
                memcg = active_memcg();
                if (unlikely(memcg)) {
                        /* remote memcg must hold a ref */
                        css_get(&memcg->css);
                        return memcg;
                }
                mm = current->mm;
                if (unlikely(!mm))
                        return root_mem_cgroup;
        }

        rcu_read_lock();
        do {
                memcg = mem_cgroup_from_task(rcu_dereference(mm->owner));
                if (unlikely(!memcg))
                        memcg = root_mem_cgroup;
        } while (!css_tryget(&memcg->css));
        rcu_read_unlock();
        return memcg;
}
EXPORT_SYMBOL(get_mem_cgroup_from_mm);

static __always_inline bool memcg_kmem_bypass(void)
{
        /* Allow remote memcg charging from any context. */
        if (unlikely(active_memcg()))
                return false;

        /* Memcg to charge can't be determined. */
        if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD))
                return true;

        return false;
}

/**
 * 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 node in @reclaim to divide up the memcgs
 * in the hierarchy among all concurrent reclaimers operating on the
 * same node.
 */
struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
                                   struct mem_cgroup *prev,
                                   struct mem_cgroup_reclaim_cookie *reclaim)
{
        struct mem_cgroup_reclaim_iter *iter;
        struct cgroup_subsys_state *css = NULL;
        struct mem_cgroup *memcg = NULL;

        struct mem_cgroup *pos = NULL;

        if (mem_cgroup_disabled())
                return NULL;

        if (!root)
                root = root_mem_cgroup;

        if (prev && !reclaim)
                pos = prev;

        rcu_read_lock();

        if (reclaim) {
                struct mem_cgroup_per_node *mz;

                mz = root->nodeinfo[reclaim->pgdat->node_id];
                iter = &mz->iter;

                if (prev && reclaim->generation != iter->generation)
                        goto out_unlock;

                while (1) {
                        pos = READ_ONCE(iter->position);
                        if (!pos || css_tryget(&pos->css))
                                break;
                        /*
                         * css reference reached zero, so iter->position will
                         * be cleared by ->css_released. However, we should not
                         * rely on this happening soon, because ->css_released
                         * is called from a work queue, and by busy-waiting we
                         * might block it. So we clear iter->position right
                         * away.
                         */
                        (void)cmpxchg(&iter->position, pos, NULL);
                }
        }

        if (pos)
                css = &pos->css;

        for (;;) {
                css = css_next_descendant_pre(css, &root->css);
                if (!css) {
                        /*
                         * Reclaimers share the hierarchy walk, and a
                         * new one might jump in right at the end of
                         * the hierarchy - make sure they see at least
                         * one group and restart from the beginning.
                         */
                        if (!prev)
                                continue;
                        break;
                }

                /*
                 * Verify the css and acquire a reference.  The root
                 * is provided by the caller, so we know it's alive
                 * and kicking, and don't take an extra reference.
                 */
                memcg = mem_cgroup_from_css(css);

                if (css == &root->css)
                        break;

                if (css_tryget(css))
                        break;

                memcg = NULL;
        }

        if (reclaim) {
                /*
                 * The position could have already been updated by a competing
                 * thread, so check that the value hasn't changed since we read
                 * it to avoid reclaiming from the same cgroup twice.
                 */
                (void)cmpxchg(&iter->position, pos, memcg);

                if (pos)
                        css_put(&pos->css);

                if (!memcg)
                        iter->generation++;
                else if (!prev)
                        reclaim->generation = iter->generation;
        }

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

        return memcg;
}

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

static void __invalidate_reclaim_iterators(struct mem_cgroup *from,
                                        struct mem_cgroup *dead_memcg)
{
        struct mem_cgroup_reclaim_iter *iter;
        struct mem_cgroup_per_node *mz;
        int nid;

        for_each_node(nid) {
                mz = from->nodeinfo[nid];
                iter = &mz->iter;
                cmpxchg(&iter->position, dead_memcg, NULL);
        }
}

static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg)
{
        struct mem_cgroup *memcg = dead_memcg;
        struct mem_cgroup *last;

        do {
                __invalidate_reclaim_iterators(memcg, dead_memcg);
                last = memcg;
        } while ((memcg = parent_mem_cgroup(memcg)));

        /*
         * When cgruop1 non-hierarchy mode is used,
         * parent_mem_cgroup() does not walk all the way up to the
         * cgroup root (root_mem_cgroup). So we have to handle
         * dead_memcg from cgroup root separately.
         */
        if (last != root_mem_cgroup)
                __invalidate_reclaim_iterators(root_mem_cgroup,
                                                dead_memcg);
}

/**
 * mem_cgroup_scan_tasks - iterate over tasks of a memory cgroup hierarchy
 * @memcg: hierarchy root
 * @fn: function to call for each task
 * @arg: argument passed to @fn
 *
 * This function iterates over tasks attached to @memcg or to any of its
 * descendants and calls @fn for each task. If @fn returns a non-zero
 * value, the function breaks the iteration loop and returns the value.
 * Otherwise, it will iterate over all tasks and return 0.
 *
 * This function must not be called for the root memory cgroup.
 */
int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
                          int (*fn)(struct task_struct *, void *), void *arg)
{
        struct mem_cgroup *iter;
        int ret = 0;

        BUG_ON(memcg == root_mem_cgroup);

        for_each_mem_cgroup_tree(iter, memcg) {
                struct css_task_iter it;
                struct task_struct *task;

                css_task_iter_start(&iter->css, CSS_TASK_ITER_PROCS, &it);
                while (!ret && (task = css_task_iter_next(&it)))
                        ret = fn(task, arg);
                css_task_iter_end(&it);
                if (ret) {
                        mem_cgroup_iter_break(memcg, iter);
                        break;
                }
        }
        return ret;
}

#ifdef CONFIG_DEBUG_VM
void lruvec_memcg_debug(struct lruvec *lruvec, struct page *page)
{
        struct mem_cgroup *memcg;

        if (mem_cgroup_disabled())
                return;

        memcg = page_memcg(page);

        if (!memcg)
                VM_BUG_ON_PAGE(lruvec_memcg(lruvec) != root_mem_cgroup, page);
        else
                VM_BUG_ON_PAGE(lruvec_memcg(lruvec) != memcg, page);
}
#endif

/**
 * lock_page_lruvec - lock and return lruvec for a given page.
 * @page: the page
 *
 * These functions are safe to use under any of the following conditions:
 * - page locked
 * - PageLRU cleared
 * - lock_page_memcg()
 * - page->_refcount is zero
 */
struct lruvec *lock_page_lruvec(struct page *page)
{
        struct lruvec *lruvec;

        lruvec = mem_cgroup_page_lruvec(page);
        spin_lock(&lruvec->lru_lock);

        lruvec_memcg_debug(lruvec, page);

        return lruvec;
}

struct lruvec *lock_page_lruvec_irq(struct page *page)
{
        struct lruvec *lruvec;

        lruvec = mem_cgroup_page_lruvec(page);
        spin_lock_irq(&lruvec->lru_lock);

        lruvec_memcg_debug(lruvec, page);

        return lruvec;
}

struct lruvec *lock_page_lruvec_irqsave(struct page *page, unsigned long *flags)
{
        struct lruvec *lruvec;

        lruvec = mem_cgroup_page_lruvec(page);
        spin_lock_irqsave(&lruvec->lru_lock, *flags);

        lruvec_memcg_debug(lruvec, page);

        return lruvec;
}

/**
 * mem_cgroup_update_lru_size - account for adding or removing an lru page
 * @lruvec: mem_cgroup per zone lru vector
 * @lru: index of lru list the page is sitting on
 * @zid: zone id of the accounted pages
 * @nr_pages: positive when adding or negative when removing
 *
 * This function must be called under lru_lock, just before a page is added
 * to or just after a page is removed from an lru list (that ordering being
 * so as to allow it to check that lru_size 0 is consistent with list_empty).
 */
void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
                                int zid, int nr_pages)
{
        struct mem_cgroup_per_node *mz;
        unsigned long *lru_size;
        long size;

        if (mem_cgroup_disabled())
                return;

        mz = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
        lru_size = &mz->lru_zone_size[zid][lru];

        if (nr_pages < 0)
                *lru_size += nr_pages;

        size = *lru_size;
        if (WARN_ONCE(size < 0,
                "%s(%p, %d, %d): lru_size %ld\n",
                __func__, lruvec, lru, nr_pages, size)) {
                VM_BUG_ON(1);
                *lru_size = 0;
        }

        if (nr_pages > 0)
                *lru_size += nr_pages;
}

/**
 * mem_cgroup_margin - calculate chargeable space of a memory cgroup
 * @memcg: the memory cgroup
 *
 * Returns the maximum amount of memory @mem can be charged with, in
 * pages.
 */
static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
{
        unsigned long margin = 0;
        unsigned long count;
        unsigned long limit;

        count = page_counter_read(&memcg->memory);
        limit = READ_ONCE(memcg->memory.max);
        if (count < limit)
                margin = limit - count;

        if (do_memsw_account()) {
                count = page_counter_read(&memcg->memsw);
                limit = READ_ONCE(memcg->memsw.max);
                if (count < limit)
                        margin = min(margin, limit - count);
                else
                        margin = 0;
        }

        return margin;
}

/*
 * A routine for checking "mem" is under move_account() or not.
 *
 * Checking a cgroup is mc.from or mc.to or under hierarchy of
 * moving cgroups. This is for waiting at high-memory pressure
 * caused by "move".
 */
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_is_descendant(from, memcg) ||
                mem_cgroup_is_descendant(to, memcg);
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;
}

struct memory_stat {
        const char *name;
        unsigned int idx;
};

static const struct memory_stat memory_stats[] = {
        { "anon",                       NR_ANON_MAPPED                  },
        { "file",                       NR_FILE_PAGES                   },
        { "kernel_stack",               NR_KERNEL_STACK_KB              },
        { "pagetables",                 NR_PAGETABLE                    },
        { "percpu",                     MEMCG_PERCPU_B                  },
        { "sock",                       MEMCG_SOCK                      },
        { "shmem",                      NR_SHMEM                        },
        { "file_mapped",                NR_FILE_MAPPED                  },
        { "file_dirty",                 NR_FILE_DIRTY                   },
        { "file_writeback",             NR_WRITEBACK                    },
#ifdef CONFIG_SWAP
        { "swapcached",                 NR_SWAPCACHE                    },
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        { "anon_thp",                   NR_ANON_THPS                    },
        { "file_thp",                   NR_FILE_THPS                    },
        { "shmem_thp",                  NR_SHMEM_THPS                   },
#endif
        { "inactive_anon",              NR_INACTIVE_ANON                },
        { "active_anon",                NR_ACTIVE_ANON                  },
        { "inactive_file",              NR_INACTIVE_FILE                },
        { "active_file",                NR_ACTIVE_FILE                  },
        { "unevictable",                NR_UNEVICTABLE                  },
        { "slab_reclaimable",           NR_SLAB_RECLAIMABLE_B           },
        { "slab_unreclaimable",         NR_SLAB_UNRECLAIMABLE_B         },

        /* The memory events */
        { "workingset_refault_anon",    WORKINGSET_REFAULT_ANON         },
        { "workingset_refault_file",    WORKINGSET_REFAULT_FILE         },
        { "workingset_activate_anon",   WORKINGSET_ACTIVATE_ANON        },
        { "workingset_activate_file",   WORKINGSET_ACTIVATE_FILE        },
        { "workingset_restore_anon",    WORKINGSET_RESTORE_ANON         },
        { "workingset_restore_file",    WORKINGSET_RESTORE_FILE         },
        { "workingset_nodereclaim",     WORKINGSET_NODERECLAIM          },
};

/* Translate stat items to the correct unit for memory.stat output */
static int memcg_page_state_unit(int item)
{
        switch (item) {
        case MEMCG_PERCPU_B:
        case NR_SLAB_RECLAIMABLE_B:
        case NR_SLAB_UNRECLAIMABLE_B:
        case WORKINGSET_REFAULT_ANON:
        case WORKINGSET_REFAULT_FILE:
        case WORKINGSET_ACTIVATE_ANON:
        case WORKINGSET_ACTIVATE_FILE:
        case WORKINGSET_RESTORE_ANON:
        case WORKINGSET_RESTORE_FILE:
        case WORKINGSET_NODERECLAIM:
                return 1;
        case NR_KERNEL_STACK_KB:
                return SZ_1K;
        default:
                return PAGE_SIZE;
        }
}

static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg,
                                                    int item)
{
        return memcg_page_state(memcg, item) * memcg_page_state_unit(item);
}

static char *memory_stat_format(struct mem_cgroup *memcg)
{
        struct seq_buf s;
        int i;

        seq_buf_init(&s, kmalloc(PAGE_SIZE, GFP_KERNEL), PAGE_SIZE);
        if (!s.buffer)
                return NULL;

        /*
         * Provide statistics on the state of the memory subsystem as
         * well as cumulative event counters that show past behavior.
         *
         * This list is ordered following a combination of these gradients:
         * 1) generic big picture -> specifics and details
         * 2) reflecting userspace activity -> reflecting kernel heuristics
         *
         * Current memory state:
         */
        cgroup_rstat_flush(memcg->css.cgroup);

        for (i = 0; i < ARRAY_SIZE(memory_stats); i++) {
                u64 size;

                size = memcg_page_state_output(memcg, memory_stats[i].idx);
                seq_buf_printf(&s, "%s %llu\n", memory_stats[i].name, size);

                if (unlikely(memory_stats[i].idx == NR_SLAB_UNRECLAIMABLE_B)) {
                        size += memcg_page_state_output(memcg,
                                                        NR_SLAB_RECLAIMABLE_B);
                        seq_buf_printf(&s, "slab %llu\n", size);
                }
        }

        /* Accumulated memory events */

        seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGFAULT),
                       memcg_events(memcg, PGFAULT));
        seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGMAJFAULT),
                       memcg_events(memcg, PGMAJFAULT));
        seq_buf_printf(&s, "%s %lu\n",  vm_event_name(PGREFILL),
                       memcg_events(memcg, PGREFILL));
        seq_buf_printf(&s, "pgscan %lu\n",
                       memcg_events(memcg, PGSCAN_KSWAPD) +
                       memcg_events(memcg, PGSCAN_DIRECT));
        seq_buf_printf(&s, "pgsteal %lu\n",
                       memcg_events(memcg, PGSTEAL_KSWAPD) +
                       memcg_events(memcg, PGSTEAL_DIRECT));
        seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGACTIVATE),
                       memcg_events(memcg, PGACTIVATE));
        seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGDEACTIVATE),
                       memcg_events(memcg, PGDEACTIVATE));
        seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGLAZYFREE),
                       memcg_events(memcg, PGLAZYFREE));
        seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGLAZYFREED),
                       memcg_events(memcg, PGLAZYFREED));

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        seq_buf_printf(&s, "%s %lu\n", vm_event_name(THP_FAULT_ALLOC),
                       memcg_events(memcg, THP_FAULT_ALLOC));
        seq_buf_printf(&s, "%s %lu\n", vm_event_name(THP_COLLAPSE_ALLOC),
                       memcg_events(memcg, THP_COLLAPSE_ALLOC));
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

        /* The above should easily fit into one page */
        WARN_ON_ONCE(seq_buf_has_overflowed(&s));

        return s.buffer;
}

#define K(x) ((x) << (PAGE_SHIFT-10))
/**
 * mem_cgroup_print_oom_context: Print OOM information relevant to
 * memory controller.
 * @memcg: The memory cgroup that went over limit
 * @p: Task that is going to be killed
 *
 * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
 * enabled
 */
void mem_cgroup_print_oom_context(struct mem_cgroup *memcg, struct task_struct *p)
{
        rcu_read_lock();

        if (memcg) {
                pr_cont(",oom_memcg=");
                pr_cont_cgroup_path(memcg->css.cgroup);
        } else
                pr_cont(",global_oom");
        if (p) {
                pr_cont(",task_memcg=");
                pr_cont_cgroup_path(task_cgroup(p, memory_cgrp_id));
        }
        rcu_read_unlock();
}

/**
 * mem_cgroup_print_oom_meminfo: Print OOM memory information relevant to
 * memory controller.
 * @memcg: The memory cgroup that went over limit
 */
void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
{
        char *buf;

        pr_info("memory: usage %llukB, limit %llukB, failcnt %lu\n",
                K((u64)page_counter_read(&memcg->memory)),
                K((u64)READ_ONCE(memcg->memory.max)), memcg->memory.failcnt);
        if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
                pr_info("swap: usage %llukB, limit %llukB, failcnt %lu\n",
                        K((u64)page_counter_read(&memcg->swap)),
                        K((u64)READ_ONCE(memcg->swap.max)), memcg->swap.failcnt);
        else {
                pr_info("memory+swap: usage %llukB, limit %llukB, failcnt %lu\n",
                        K((u64)page_counter_read(&memcg->memsw)),
                        K((u64)memcg->memsw.max), memcg->memsw.failcnt);
                pr_info("kmem: usage %llukB, limit %llukB, failcnt %lu\n",
                        K((u64)page_counter_read(&memcg->kmem)),
                        K((u64)memcg->kmem.max), memcg->kmem.failcnt);
        }

        pr_info("Memory cgroup stats for ");
        pr_cont_cgroup_path(memcg->css.cgroup);
        pr_cont(":");
        buf = memory_stat_format(memcg);
        if (!buf)
                return;
        pr_info("%s", buf);
        kfree(buf);
}

/*
 * Return the memory (and swap, if configured) limit for a memcg.
 */
unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg)
{
        unsigned long max = READ_ONCE(memcg->memory.max);

        if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
                if (mem_cgroup_swappiness(memcg))
                        max += min(READ_ONCE(memcg->swap.max),
                                   (unsigned long)total_swap_pages);
        } else { /* v1 */
                if (mem_cgroup_swappiness(memcg)) {
                        /* Calculate swap excess capacity from memsw limit */
                        unsigned long swap = READ_ONCE(memcg->memsw.max) - max;

                        max += min(swap, (unsigned long)total_swap_pages);
                }
        }
        return max;
}

unsigned long mem_cgroup_size(struct mem_cgroup *memcg)
{
        return page_counter_read(&memcg->memory);
}

static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
                                     int order)
{
        struct oom_control oc = {
                .zonelist = NULL,
                .nodemask = NULL,
                .memcg = memcg,
                .gfp_mask = gfp_mask,
                .order = order,
        };
        bool ret = true;

        if (mutex_lock_killable(&oom_lock))
                return true;

        if (mem_cgroup_margin(memcg) >= (1 << order))
                goto unlock;

        /*
         * A few threads which were not waiting at mutex_lock_killable() can
         * fail to bail out. Therefore, check again after holding oom_lock.
         */
        ret = should_force_charge() || out_of_memory(&oc);

unlock:
        mutex_unlock(&oom_lock);
        return ret;
}

static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
                                   pg_data_t *pgdat,
                                   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 = {
                .pgdat = pgdat,
        };

        excess = soft_limit_excess(root_memcg);

        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;
                }
                total += mem_cgroup_shrink_node(victim, gfp_mask, false,
                                        pgdat, &nr_scanned);
                *total_scanned += nr_scanned;
                if (!soft_limit_excess(root_memcg))
                        break;
        }
        mem_cgroup_iter_break(root_memcg, victim);
        return total;
}

#ifdef CONFIG_LOCKDEP
static struct lockdep_map memcg_oom_lock_dep_map = {
        .name = "memcg_oom_lock",
};
#endif

static DEFINE_SPINLOCK(memcg_oom_lock);

/*
 * Check OOM-Killer is already running under our hierarchy.
 * If someone is running, return false.
 */
static bool mem_cgroup_oom_trylock(struct mem_cgroup *memcg)
{
        struct mem_cgroup *iter, *failed = NULL;

        spin_lock(&memcg_oom_lock);

        for_each_mem_cgroup_tree(iter, memcg) {
                if (iter->oom_lock) {
                        /*
                         * this subtree of our hierarchy is already locked
                         * so we cannot give a lock.
                         */
                        failed = iter;
                        mem_cgroup_iter_break(memcg, iter);
                        break;
                } else
                        iter->oom_lock = true;
        }

        if (failed) {
                /*
                 * OK, we failed to lock the whole subtree so we have
                 * to clean up what we set up to the failing subtree
                 */
                for_each_mem_cgroup_tree(iter, memcg) {
                        if (iter == failed) {
                                mem_cgroup_iter_break(memcg, iter);
                                break;
                        }
                        iter->oom_lock = false;
                }
        } else
                mutex_acquire(&memcg_oom_lock_dep_map, 0, 1, _RET_IP_);

        spin_unlock(&memcg_oom_lock);

        return !failed;
}

static void mem_cgroup_oom_unlock(struct mem_cgroup *memcg)
{
        struct mem_cgroup *iter;

        spin_lock(&memcg_oom_lock);
        mutex_release(&memcg_oom_lock_dep_map, _RET_IP_);
        for_each_mem_cgroup_tree(iter, memcg)
                iter->oom_lock = false;
        spin_unlock(&memcg_oom_lock);
}

static void mem_cgroup_mark_under_oom(struct mem_cgroup *memcg)
{
        struct mem_cgroup *iter;

        spin_lock(&memcg_oom_lock);
        for_each_mem_cgroup_tree(iter, memcg)
                iter->under_oom++;
        spin_unlock(&memcg_oom_lock);
}

static void mem_cgroup_unmark_under_oom(struct mem_cgroup *memcg)
{
        struct mem_cgroup *iter;

        /*
         * Be careful about under_oom underflows because a child memcg
         * could have been added after mem_cgroup_mark_under_oom.
         */
        spin_lock(&memcg_oom_lock);
        for_each_mem_cgroup_tree(iter, memcg)
                if (iter->under_oom > 0)
                        iter->under_oom--;
        spin_unlock(&memcg_oom_lock);
}

static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);

struct oom_wait_info {
        struct mem_cgroup *memcg;
        wait_queue_entry_t      wait;
};

static int memcg_oom_wake_function(wait_queue_entry_t *wait,
        unsigned mode, int sync, void *arg)
{
        struct mem_cgroup *wake_memcg = (struct mem_cgroup *)arg;
        struct mem_cgroup *oom_wait_memcg;
        struct oom_wait_info *oom_wait_info;

        oom_wait_info = container_of(wait, struct oom_wait_info, wait);
        oom_wait_memcg = oom_wait_info->memcg;

        if (!mem_cgroup_is_descendant(wake_memcg, oom_wait_memcg) &&
            !mem_cgroup_is_descendant(oom_wait_memcg, wake_memcg))
                return 0;
        return autoremove_wake_function(wait, mode, sync, arg);
}

static void memcg_oom_recover(struct mem_cgroup *memcg)
{
        /*
         * For the following lockless ->under_oom test, the only required
         * guarantee is that it must see the state asserted by an OOM when
         * this function is called as a result of userland actions
         * triggered by the notification of the OOM.  This is trivially
         * achieved by invoking mem_cgroup_mark_under_oom() before
         * triggering notification.
         */
        if (memcg && memcg->under_oom)
                __wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, memcg);
}

enum oom_status {
        OOM_SUCCESS,
        OOM_FAILED,
        OOM_ASYNC,
        OOM_SKIPPED
};

static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order)
{
        enum oom_status ret;
        bool locked;

        if (order > PAGE_ALLOC_COSTLY_ORDER)
                return OOM_SKIPPED;

        memcg_memory_event(memcg, MEMCG_OOM);

        /*
         * We are in the middle of the charge context here, so we
         * don't want to block when potentially sitting on a callstack
         * that holds all kinds of filesystem and mm locks.
         *
         * cgroup1 allows disabling the OOM killer and waiting for outside
         * handling until the charge can succeed; remember the context and put
         * the task to sleep at the end of the page fault when all locks are
         * released.
         *
         * On the other hand, in-kernel OOM killer allows for an async victim
         * memory reclaim (oom_reaper) and that means that we are not solely
         * relying on the oom victim to make a forward progress and we can
         * invoke the oom killer here.
         *
         * Please note that mem_cgroup_out_of_memory might fail to find a
         * victim and then we have to bail out from the charge path.
         */
        if (memcg->oom_kill_disable) {
                if (!current->in_user_fault)
                        return OOM_SKIPPED;
                css_get(&memcg->css);
                current->memcg_in_oom = memcg;
                current->memcg_oom_gfp_mask = mask;
                current->memcg_oom_order = order;

                return OOM_ASYNC;
        }

        mem_cgroup_mark_under_oom(memcg);

        locked = mem_cgroup_oom_trylock(memcg);

        if (locked)
                mem_cgroup_oom_notify(memcg);

        mem_cgroup_unmark_under_oom(memcg);
        if (mem_cgroup_out_of_memory(memcg, mask, order))
                ret = OOM_SUCCESS;
        else
                ret = OOM_FAILED;

        if (locked)
                mem_cgroup_oom_unlock(memcg);

        return ret;
}

/**
 * mem_cgroup_oom_synchronize - complete memcg OOM handling
 * @handle: actually kill/wait or just clean up the OOM state
 *
 * This has to be called at the end of a page fault if the memcg OOM
 * handler was enabled.
 *
 * Memcg supports userspace OOM handling where failed allocations must
 * sleep on a waitqueue until the userspace task resolves the
 * situation.  Sleeping directly in the charge context with all kinds
 * of locks held is not a good idea, instead we remember an OOM state
 * in the task and mem_cgroup_oom_synchronize() has to be called at
 * the end of the page fault to complete the OOM handling.
 *
 * Returns %true if an ongoing memcg OOM situation was detected and
 * completed, %false otherwise.
 */
bool mem_cgroup_oom_synchronize(bool handle)
{
        struct mem_cgroup *memcg = current->memcg_in_oom;
        struct oom_wait_info owait;
        bool locked;

        /* OOM is global, do not handle */
        if (!memcg)
                return false;

        if (!handle)
                goto cleanup;

        owait.memcg = memcg;
        owait.wait.flags = 0;
        owait.wait.func = memcg_oom_wake_function;
        owait.wait.private = current;
        INIT_LIST_HEAD(&owait.wait.entry);

        prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
        mem_cgroup_mark_under_oom(memcg);

        locked = mem_cgroup_oom_trylock(memcg);

        if (locked)
                mem_cgroup_oom_notify(memcg);

        if (locked && !memcg->oom_kill_disable) {
                mem_cgroup_unmark_under_oom(memcg);
                finish_wait(&memcg_oom_waitq, &owait.wait);
                mem_cgroup_out_of_memory(memcg, current->memcg_oom_gfp_mask,
                                         current->memcg_oom_order);
        } else {
                schedule();
                mem_cgroup_unmark_under_oom(memcg);
                finish_wait(&memcg_oom_waitq, &owait.wait);
        }

        if (locked) {
                mem_cgroup_oom_unlock(memcg);
                /*
                 * There is no guarantee that an OOM-lock contender
                 * sees the wakeups triggered by the OOM kill
                 * uncharges.  Wake any sleepers explicitly.
                 */
                memcg_oom_recover(memcg);
        }
cleanup:
        current->memcg_in_oom = NULL;
        css_put(&memcg->css);
        return true;
}

/**
 * mem_cgroup_get_oom_group - get a memory cgroup to clean up after OOM
 * @victim: task to be killed by the OOM killer
 * @oom_domain: memcg in case of memcg OOM, NULL in case of system-wide OOM
 *
 * Returns a pointer to a memory cgroup, which has to be cleaned up
 * by killing all belonging OOM-killable tasks.
 *
 * Caller has to call mem_cgroup_put() on the returned non-NULL memcg.
 */
struct mem_cgroup *mem_cgroup_get_oom_group(struct task_struct *victim,
                                            struct mem_cgroup *oom_domain)
{
        struct mem_cgroup *oom_group = NULL;
        struct mem_cgroup *memcg;

        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
                return NULL;

        if (!oom_domain)
                oom_domain = root_mem_cgroup;

        rcu_read_lock();

        memcg = mem_cgroup_from_task(victim);
        if (memcg == root_mem_cgroup)
                goto out;

        /*
         * If the victim task has been asynchronously moved to a different
         * memory cgroup, we might end up killing tasks outside oom_domain.
         * In this case it's better to ignore memory.group.oom.
         */
        if (unlikely(!mem_cgroup_is_descendant(memcg, oom_domain)))
                goto out;

        /*
         * Traverse the memory cgroup hierarchy from the victim task's
         * cgroup up to the OOMing cgroup (or root) to find the
         * highest-level memory cgroup with oom.group set.
         */
        for (; memcg; memcg = parent_mem_cgroup(memcg)) {
                if (memcg->oom_group)
                        oom_group = memcg;

                if (memcg == oom_domain)
                        break;
        }

        if (oom_group)
                css_get(&oom_group->css);
out:
        rcu_read_unlock();

        return oom_group;
}

void mem_cgroup_print_oom_group(struct mem_cgroup *memcg)
{
        pr_info("Tasks in ");
        pr_cont_cgroup_path(memcg->css.cgroup);
        pr_cont(" are going to be killed due to memory.oom.group set\n");
}

/**
 * lock_page_memcg - lock a page and memcg binding
 * @page: the page
 *
 * This function protects unlocked LRU pages from being moved to
 * another cgroup.
 *
 * It ensures lifetime of the locked memcg. Caller is responsible
 * for the lifetime of the page.
 */
void lock_page_memcg(struct page *page)

{
        struct page *head = compound_head(page); /* rmap on tail pages */
        struct mem_cgroup *memcg;
        unsigned long flags;

        /*
         * The RCU lock is held throughout the transaction.  The fast
         * path can get away without acquiring the memcg->move_lock
         * because page moving starts with an RCU grace period.
         */
        rcu_read_lock();

        if (mem_cgroup_disabled())
                return;
again:
        memcg = page_memcg(head);
        if (unlikely(!memcg))
                return;

#ifdef CONFIG_PROVE_LOCKING
        local_irq_save(flags);
        might_lock(&memcg->move_lock);
        local_irq_restore(flags);
#endif

        if (atomic_read(&memcg->moving_account) <= 0)
                return;

        spin_lock_irqsave(&memcg->move_lock, flags);
        if (memcg != page_memcg(head)) {
                spin_unlock_irqrestore(&memcg->move_lock, flags);
                goto again;
        }

        /*
         * When charge migration first begins, we can have multiple
         * critical sections holding the fast-path RCU lock and one
         * holding the slowpath move_lock. Track the task who has the
         * move_lock for unlock_page_memcg().
         */
        memcg->move_lock_task = current;
        memcg->move_lock_flags = flags;
}
EXPORT_SYMBOL(lock_page_memcg);

static void __unlock_page_memcg(struct mem_cgroup *memcg)
{
        if (memcg && memcg->move_lock_task == current) {
                unsigned long flags = memcg->move_lock_flags;

                memcg->move_lock_task = NULL;
                memcg->move_lock_flags = 0;

                spin_unlock_irqrestore(&memcg->move_lock, flags);
        }

        rcu_read_unlock();
}

/**
 * unlock_page_memcg - unlock a page and memcg binding
 * @page: the page
 */
void unlock_page_memcg(struct page *page)
{
        struct page *head = compound_head(page);

        __unlock_page_memcg(page_memcg(head));
}
EXPORT_SYMBOL(unlock_page_memcg);

struct obj_stock {
#ifdef CONFIG_MEMCG_KMEM
        struct obj_cgroup *cached_objcg;
        struct pglist_data *cached_pgdat;
        unsigned int nr_bytes;
        int nr_slab_reclaimable_b;
        int nr_slab_unreclaimable_b;
#else
        int dummy[0];
#endif
};

struct memcg_stock_pcp {
        struct mem_cgroup *cached; /* this never be root cgroup */
        unsigned int nr_pages;
        struct obj_stock task_obj;
        struct obj_stock irq_obj;

        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);

#ifdef CONFIG_MEMCG_KMEM
static void drain_obj_stock(struct obj_stock *stock);
static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
                                     struct mem_cgroup *root_memcg);

#else
static inline void drain_obj_stock(struct obj_stock *stock)
{
}
static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
                                     struct mem_cgroup *root_memcg)
{
        return false;
}
#endif

/*
 * Most kmem_cache_alloc() calls are from user context. The irq disable/enable
 * sequence used in this case to access content from object stock is slow.
 * To optimize for user context access, there are now two object stocks for
 * task context and interrupt context access respectively.
 *
 * The task context object stock can be accessed by disabling preemption only
 * which is cheap in non-preempt kernel. The interrupt context object stock
 * can only be accessed after disabling interrupt. User context code can
 * access interrupt object stock, but not vice versa.
 */
static inline struct obj_stock *get_obj_stock(unsigned long *pflags)
{
        struct memcg_stock_pcp *stock;

        if (likely(in_task())) {
                *pflags = 0UL;
                preempt_disable();
                stock = this_cpu_ptr(&memcg_stock);
                return &stock->task_obj;
        }

        local_irq_save(*pflags);
        stock = this_cpu_ptr(&memcg_stock);
        return &stock->irq_obj;
}

static inline void put_obj_stock(unsigned long flags)
{
        if (likely(in_task()))
                preempt_enable();
        else
                local_irq_restore(flags);
}

/**
 * consume_stock: Try to consume stocked charge on this cpu.
 * @memcg: memcg to consume from.
 * @nr_pages: how many pages to charge.
 *
 * The charges will only happen if @memcg matches the current cpu's memcg
 * stock, and at least @nr_pages are available in that stock.  Failure to
 * service an allocation will refill the stock.
 *
 * returns true if successful, false otherwise.
 */
static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
{
        struct memcg_stock_pcp *stock;
        unsigned long flags;
        bool ret = false;

        if (nr_pages > MEMCG_CHARGE_BATCH)
                return ret;

        local_irq_save(flags);

        stock = this_cpu_ptr(&memcg_stock);
        if (memcg == stock->cached && stock->nr_pages >= nr_pages) {
                stock->nr_pages -= nr_pages;
                ret = true;
        }

        local_irq_restore(flags);

        return ret;
}

/*
 * Returns stocks cached in percpu and reset cached information.
 */
static void drain_stock(struct memcg_stock_pcp *stock)
{
        struct mem_cgroup *old = stock->cached;

        if (!old)
                return;

        if (stock->nr_pages) {
                page_counter_uncharge(&old->memory, stock->nr_pages);
                if (do_memsw_account())
                        page_counter_uncharge(&old->memsw, stock->nr_pages);
                stock->nr_pages = 0;
        }

        css_put(&old->css);
        stock->cached = NULL;
}

static void drain_local_stock(struct work_struct *dummy)
{
        struct memcg_stock_pcp *stock;
        unsigned long flags;

        /*
         * The only protection from memory hotplug vs. drain_stock races is
         * that we always operate on local CPU stock here with IRQ disabled
         */
        local_irq_save(flags);

        stock = this_cpu_ptr(&memcg_stock);
        drain_obj_stock(&stock->irq_obj);
        if (in_task())
                drain_obj_stock(&stock->task_obj);
        drain_stock(stock);
        clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);

        local_irq_restore(flags);
}

/*
 * Cache charges(val) to local per_cpu area.
 * This will be consumed by consume_stock() function, later.
 */
static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
{
        struct memcg_stock_pcp *stock;
        unsigned long flags;

        local_irq_save(flags);

        stock = this_cpu_ptr(&memcg_stock);
        if (stock->cached != memcg) { /* reset if necessary */
                drain_stock(stock);
                css_get(&memcg->css);
                stock->cached = memcg;
        }
        stock->nr_pages += nr_pages;

        if (stock->nr_pages > MEMCG_CHARGE_BATCH)
                drain_stock(stock);

        local_irq_restore(flags);
}

/*
 * Drains all per-CPU charge caches for given root_memcg resp. subtree
 * of the hierarchy under it.
 */
static void drain_all_stock(struct mem_cgroup *root_memcg)
{
        int cpu, curcpu;

        /* If someone's already draining, avoid adding running more workers. */
        if (!mutex_trylock(&percpu_charge_mutex))
                return;
        /*
         * Notify other cpus that system-wide "drain" is running
         * We do not care about races with the cpu hotplug because cpu down
         * as well as workers from this path always operate on the local
         * per-cpu data. CPU up doesn't touch memcg_stock at all.
         */
        curcpu = get_cpu();
        for_each_online_cpu(cpu) {
                struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu);
                struct mem_cgroup *memcg;
                bool flush = false;

                rcu_read_lock();
                memcg = stock->cached;
                if (memcg && stock->nr_pages &&
                    mem_cgroup_is_descendant(memcg, root_memcg))
                        flush = true;
                if (obj_stock_flush_required(stock, root_memcg))
                        flush = true;
                rcu_read_unlock();

                if (flush &&
                    !test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) {
                        if (cpu == curcpu)
                                drain_local_stock(&stock->work);
                        else
                                schedule_work_on(cpu, &stock->work);
                }
        }
        put_cpu();
        mutex_unlock(&percpu_charge_mutex);
}

static void memcg_flush_lruvec_page_state(struct mem_cgroup *memcg, int cpu)
{
        int nid;

        for_each_node(nid) {
                struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid];
                unsigned long stat[NR_VM_NODE_STAT_ITEMS];
                struct batched_lruvec_stat *lstatc;
                int i;

                lstatc = per_cpu_ptr(pn->lruvec_stat_cpu, cpu);
                for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
                        stat[i] = lstatc->count[i];
                        lstatc->count[i] = 0;
                }

                do {
                        for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
                                atomic_long_add(stat[i], &pn->lruvec_stat[i]);
                } while ((pn = parent_nodeinfo(pn, nid)));
        }
}

static int memcg_hotplug_cpu_dead(unsigned int cpu)
{
        struct memcg_stock_pcp *stock;
        struct mem_cgroup *memcg;

        stock = &per_cpu(memcg_stock, cpu);
        drain_stock(stock);

        for_each_mem_cgroup(memcg)
                memcg_flush_lruvec_page_state(memcg, cpu);

        return 0;
}

static unsigned long reclaim_high(struct mem_cgroup *memcg,
                                  unsigned int nr_pages,
                                  gfp_t gfp_mask)
{
        unsigned long nr_reclaimed = 0;

        do {
                unsigned long pflags;

                if (page_counter_read(&memcg->memory) <=
                    READ_ONCE(memcg->memory.high))
                        continue;

                memcg_memory_event(memcg, MEMCG_HIGH);

                psi_memstall_enter(&pflags);
                nr_reclaimed += try_to_free_mem_cgroup_pages(memcg, nr_pages,
                                                             gfp_mask, true);
                psi_memstall_leave(&pflags);
        } while ((memcg = parent_mem_cgroup(memcg)) &&
                 !mem_cgroup_is_root(memcg));

        return nr_reclaimed;
}

static void high_work_func(struct work_struct *work)
{
        struct mem_cgroup *memcg;

        memcg = container_of(work, struct mem_cgroup, high_work);
        reclaim_high(memcg, MEMCG_CHARGE_BATCH, GFP_KERNEL);
}

/*
 * Clamp the maximum sleep time per allocation batch to 2 seconds. This is
 * enough to still cause a significant slowdown in most cases, while still
 * allowing diagnostics and tracing to proceed without becoming stuck.
 */
#define MEMCG_MAX_HIGH_DELAY_JIFFIES (2UL*HZ)

/*
 * When calculating the delay, we use these either side of the exponentiation to
 * maintain precision and scale to a reasonable number of jiffies (see the table
 * below.
 *
 * - MEMCG_DELAY_PRECISION_SHIFT: Extra precision bits while translating the
 *   overage ratio to a delay.
 * - MEMCG_DELAY_SCALING_SHIFT: The number of bits to scale down the
 *   proposed penalty in order to reduce to a reasonable number of jiffies, and
 *   to produce a reasonable delay curve.
 *
 * MEMCG_DELAY_SCALING_SHIFT just happens to be a number that produces a
 * reasonable delay curve compared to precision-adjusted overage, not
 * penalising heavily at first, but still making sure that growth beyond the
 * limit penalises misbehaviour cgroups by slowing them down exponentially. For
 * example, with a high of 100 megabytes:
 *
 *  +-------+------------------------+
 *  | usage | time to allocate in ms |
 *  +-------+------------------------+
 *  | 100M  |                      0 |
 *  | 101M  |                      6 |
 *  | 102M  |                     25 |
 *  | 103M  |                     57 |
 *  | 104M  |                    102 |
 *  | 105M  |                    159 |
 *  | 106M  |                    230 |
 *  | 107M  |                    313 |
 *  | 108M  |                    409 |
 *  | 109M  |                    518 |
 *  | 110M  |                    639 |
 *  | 111M  |                    774 |
 *  | 112M  |                    921 |
 *  | 113M  |                   1081 |
 *  | 114M  |                   1254 |
 *  | 115M  |                   1439 |
 *  | 116M  |                   1638 |
 *  | 117M  |                   1849 |
 *  | 118M  |                   2000 |
 *  | 119M  |                   2000 |
 *  | 120M  |                   2000 |
 *  +-------+------------------------+
 */
 #define MEMCG_DELAY_PRECISION_SHIFT 20
 #define MEMCG_DELAY_SCALING_SHIFT 14

static u64 calculate_overage(unsigned long usage, unsigned long high)
{
        u64 overage;

        if (usage <= high)
                return 0;

        /*
         * Prevent division by 0 in overage calculation by acting as if
         * it was a threshold of 1 page
         */
        high = max(high, 1UL);

        overage = usage - high;
        overage <<= MEMCG_DELAY_PRECISION_SHIFT;
        return div64_u64(overage, high);
}

static u64 mem_find_max_overage(struct mem_cgroup *memcg)
{
        u64 overage, max_overage = 0;

        do {
                overage = calculate_overage(page_counter_read(&memcg->memory),
                                            READ_ONCE(memcg->memory.high));
                max_overage = max(overage, max_overage);
        } while ((memcg = parent_mem_cgroup(memcg)) &&
                 !mem_cgroup_is_root(memcg));

        return max_overage;
}

static u64 swap_find_max_overage(struct mem_cgroup *memcg)
{
        u64 overage, max_overage = 0;

        do {
                overage = calculate_overage(page_counter_read(&memcg->swap),
                                            READ_ONCE(memcg->swap.high));
                if (overage)
                        memcg_memory_event(memcg, MEMCG_SWAP_HIGH);
                max_overage = max(overage, max_overage);
        } while ((memcg = parent_mem_cgroup(memcg)) &&
                 !mem_cgroup_is_root(memcg));

        return max_overage;
}

/*
 * Get the number of jiffies that we should penalise a mischievous cgroup which
 * is exceeding its memory.high by checking both it and its ancestors.
 */
static unsigned long calculate_high_delay(struct mem_cgroup *memcg,
                                          unsigned int nr_pages,
                                          u64 max_overage)
{
        unsigned long penalty_jiffies;

        if (!max_overage)
                return 0;

        /*
         * We use overage compared to memory.high to calculate the number of
         * jiffies to sleep (penalty_jiffies). Ideally this value should be
         * fairly lenient on small overages, and increasingly harsh when the
         * memcg in question makes it clear that it has no intention of stopping
         * its crazy behaviour, so we exponentially increase the delay based on
         * overage amount.
         */
        penalty_jiffies = max_overage * max_overage * HZ;
        penalty_jiffies >>= MEMCG_DELAY_PRECISION_SHIFT;
        penalty_jiffies >>= MEMCG_DELAY_SCALING_SHIFT;

        /*
         * Factor in the task's own contribution to the overage, such that four
         * N-sized allocations are throttled approximately the same as one
         * 4N-sized allocation.
         *
         * MEMCG_CHARGE_BATCH pages is nominal, so work out how much smaller or
         * larger the current charge patch is than that.
         */
        return penalty_jiffies * nr_pages / MEMCG_CHARGE_BATCH;
}

/*
 * Scheduled by try_charge() to be executed from the userland return path
 * and reclaims memory over the high limit.
 */
void mem_cgroup_handle_over_high(void)
{
        unsigned long penalty_jiffies;
        unsigned long pflags;
        unsigned long nr_reclaimed;
        unsigned int nr_pages = current->memcg_nr_pages_over_high;
        int nr_retries = MAX_RECLAIM_RETRIES;
        struct mem_cgroup *memcg;
        bool in_retry = false;

        if (likely(!nr_pages))
                return;

        memcg = get_mem_cgroup_from_mm(current->mm);
        current->memcg_nr_pages_over_high = 0;

retry_reclaim:
        /*
         * The allocating task should reclaim at least the batch size, but for
         * subsequent retries we only want to do what's necessary to prevent oom
         * or breaching resource isolation.
         *
         * This is distinct from memory.max or page allocator behaviour because
         * memory.high is currently batched, whereas memory.max and the page
         * allocator run every time an allocation is made.
         */
        nr_reclaimed = reclaim_high(memcg,
                                    in_retry ? SWAP_CLUSTER_MAX : nr_pages,
                                    GFP_KERNEL);

        /*
         * memory.high is breached and reclaim is unable to keep up. Throttle
         * allocators proactively to slow down excessive growth.
         */
        penalty_jiffies = calculate_high_delay(memcg, nr_pages,
                                               mem_find_max_overage(memcg));

        penalty_jiffies += calculate_high_delay(memcg, nr_pages,
                                                swap_find_max_overage(memcg));

        /*
         * Clamp the max delay per usermode return so as to still keep the
         * application moving forwards and also permit diagnostics, albeit
         * extremely slowly.
         */
        penalty_jiffies = min(penalty_jiffies, MEMCG_MAX_HIGH_DELAY_JIFFIES);

        /*
         * Don't sleep if the amount of jiffies this memcg owes us is so low
         * that it's not even worth doing, in an attempt to be nice to those who
         * go only a small amount over their memory.high value and maybe haven't
         * been aggressively reclaimed enough yet.
         */
        if (penalty_jiffies <= HZ / 100)
                goto out;

        /*
         * If reclaim is making forward progress but we're still over
         * memory.high, we want to encourage that rather than doing allocator
         * throttling.
         */
        if (nr_reclaimed || nr_retries--) {
                in_retry = true;
                goto retry_reclaim;
        }

        /*
         * If we exit early, we're guaranteed to die (since
         * schedule_timeout_killable sets TASK_KILLABLE). This means we don't
         * need to account for any ill-begotten jiffies to pay them off later.
         */
        psi_memstall_enter(&pflags);
        schedule_timeout_killable(penalty_jiffies);
        psi_memstall_leave(&pflags);

out:
        css_put(&memcg->css);
}

static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
                        unsigned int nr_pages)
{
        unsigned int batch = max(MEMCG_CHARGE_BATCH, nr_pages);
        int nr_retries = MAX_RECLAIM_RETRIES;
        struct mem_cgroup *mem_over_limit;
        struct page_counter *counter;
        enum oom_status oom_status;
        unsigned long nr_reclaimed;
        bool may_swap = true;
        bool drained = false;
        unsigned long pflags;

retry:
        if (consume_stock(memcg, nr_pages))
                return 0;

        if (!do_memsw_account() ||
            page_counter_try_charge(&memcg->memsw, batch, &counter)) {
                if (page_counter_try_charge(&memcg->memory, batch, &counter))
                        goto done_restock;
                if (do_memsw_account())
                        page_counter_uncharge(&memcg->memsw, batch);
                mem_over_limit = mem_cgroup_from_counter(counter, memory);
        } else {
                mem_over_limit = mem_cgroup_from_counter(counter, memsw);
                may_swap = false;
        }

        if (batch > nr_pages) {
                batch = nr_pages;
                goto retry;
        }

        /*
         * Memcg doesn't have a dedicated reserve for atomic
         * allocations. But like the global atomic pool, we need to
         * put the burden of reclaim on regular allocation requests
         * and let these go through as privileged allocations.
         */
        if (gfp_mask & __GFP_ATOMIC)
                goto force;

        /*
         * Unlike in global OOM situations, memcg is not in a physical
         * memory shortage.  Allow dying and OOM-killed tasks to
         * bypass the last charges so that they can exit quickly and
         * free their memory.
         */
        if (unlikely(should_force_charge()))
                goto force;

        /*
         * Prevent unbounded recursion when reclaim operations need to
         * allocate memory. This might exceed the limits temporarily,
         * but we prefer facilitating memory reclaim and getting back
         * under the limit over triggering OOM kills in these cases.
         */
        if (unlikely(current->flags & PF_MEMALLOC))
                goto force;

        if (unlikely(task_in_memcg_oom(current)))
                goto nomem;

        if (!gfpflags_allow_blocking(gfp_mask))
                goto nomem;

        memcg_memory_event(mem_over_limit, MEMCG_MAX);

        psi_memstall_enter(&pflags);
        nr_reclaimed = try_to_free_mem_cgroup_pages(mem_over_limit, nr_pages,
                                                    gfp_mask, may_swap);
        psi_memstall_leave(&pflags);

        if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
                goto retry;

        if (!drained) {
                drain_all_stock(mem_over_limit);
                drained = true;
                goto retry;
        }

        if (gfp_mask & __GFP_NORETRY)
                goto nomem;
        /*
         * Even though the limit is exceeded at this point, reclaim
         * may have been able to free some pages.  Retry the charge
         * before killing the task.
         *
         * Only for regular pages, though: huge pages are rather
         * unlikely to succeed so close to the limit, and we fall back
         * to regular pages anyway in case of failure.
         */
        if (nr_reclaimed && nr_pages <= (1 << PAGE_ALLOC_COSTLY_ORDER))
                goto retry;
        /*
         * At task move, charge accounts can be doubly counted. So, it's
         * better to wait until the end of task_move if something is going on.
         */
        if (mem_cgroup_wait_acct_move(mem_over_limit))
                goto retry;

        if (nr_retries--)
                goto retry;

        if (gfp_mask & __GFP_RETRY_MAYFAIL)
                goto nomem;

        if (fatal_signal_pending(current))
                goto force;

        /*
         * keep retrying as long as the memcg oom killer is able to make
         * a forward progress or bypass the charge if the oom killer
         * couldn't make any progress.
         */
        oom_status = mem_cgroup_oom(mem_over_limit, gfp_mask,
                       get_order(nr_pages * PAGE_SIZE));
        switch (oom_status) {
        case OOM_SUCCESS:
                nr_retries = MAX_RECLAIM_RETRIES;
                goto retry;
        case OOM_FAILED:
                goto force;
        default:
                goto nomem;
        }
nomem:
        if (!(gfp_mask & __GFP_NOFAIL))
                return -ENOMEM;
force:
        /*
         * The allocation either can't fail or will lead to more memory
         * being freed very soon.  Allow memory usage go over the limit
         * temporarily by force charging it.
         */
        page_counter_charge(&memcg->memory, nr_pages);
        if (do_memsw_account())
                page_counter_charge(&memcg->memsw, nr_pages);

        return 0;

done_restock:
        if (batch > nr_pages)
                refill_stock(memcg, batch - nr_pages);

        /*
         * If the hierarchy is above the normal consumption range, schedule
         * reclaim on returning to userland.  We can perform reclaim here
         * if __GFP_RECLAIM but let's always punt for simplicity and so that
         * GFP_KERNEL can consistently be used during reclaim.  @memcg is
         * not recorded as it most likely matches current's and won't
         * change in the meantime.  As high limit is checked again before
         * reclaim, the cost of mismatch is negligible.
         */
        do {
                bool mem_high, swap_high;

                mem_high = page_counter_read(&memcg->memory) >
                        READ_ONCE(memcg->memory.high);
                swap_high = page_counter_read(&memcg->swap) >
                        READ_ONCE(memcg->swap.high);

                /* Don't bother a random interrupted task */
                if (in_interrupt()) {
                        if (mem_high) {
                                schedule_work(&memcg->high_work);
                                break;
                        }
                        continue;
                }

                if (mem_high || swap_high) {
                        /*
                         * The allocating tasks in this cgroup will need to do
                         * reclaim or be throttled to prevent further growth
                         * of the memory or swap footprints.
                         *
                         * Target some best-effort fairness between the tasks,
                         * and distribute reclaim work and delay penalties
                         * based on how much each task is actually allocating.
                         */
                        current->memcg_nr_pages_over_high += batch;
                        set_notify_resume(current);
                        break;
                }
        } while ((memcg = parent_mem_cgroup(memcg)));

        return 0;
}

static inline int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
                             unsigned int nr_pages)
{
        if (mem_cgroup_is_root(memcg))
                return 0;

        return try_charge_memcg(memcg, gfp_mask, nr_pages);
}

#if defined(CONFIG_MEMCG_KMEM) || defined(CONFIG_MMU)
static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
{
        if (mem_cgroup_is_root(memcg))
                return;

        page_counter_uncharge(&memcg->memory, nr_pages);
        if (do_memsw_account())
                page_counter_uncharge(&memcg->memsw, nr_pages);
}
#endif

static void commit_charge(struct page *page, struct mem_cgroup *memcg)
{
        VM_BUG_ON_PAGE(page_memcg(page), page);
        /*
         * Any of the following ensures page's memcg stability:
         *
         * - the page lock
         * - LRU isolation
         * - lock_page_memcg()
         * - exclusive reference
         */
        page->memcg_data = (unsigned long)memcg;
}

static struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *objcg)
{
        struct mem_cgroup *memcg;

        rcu_read_lock();
retry:
        memcg = obj_cgroup_memcg(objcg);
        if (unlikely(!css_tryget(&memcg->css)))
                goto retry;
        rcu_read_unlock();

        return memcg;
}

#ifdef CONFIG_MEMCG_KMEM
/*
 * The allocated objcg pointers array is not accounted directly.
 * Moreover, it should not come from DMA buffer and is not readily
 * reclaimable. So those GFP bits should be masked off.
 */
#define OBJCGS_CLEAR_MASK       (__GFP_DMA | __GFP_RECLAIMABLE | __GFP_ACCOUNT)

int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
                                 gfp_t gfp, bool new_page)
{
        unsigned int objects = objs_per_slab_page(s, page);
        unsigned long memcg_data;
        void *vec;

        gfp &= ~OBJCGS_CLEAR_MASK;
        vec = kcalloc_node(objects, sizeof(struct obj_cgroup *), gfp,
                           page_to_nid(page));
        if (!vec)
                return -ENOMEM;

        memcg_data = (unsigned long) vec | MEMCG_DATA_OBJCGS;
        if (new_page) {
                /*
                 * If the slab page is brand new and nobody can yet access
                 * it's memcg_data, no synchronization is required and
                 * memcg_data can be simply assigned.
                 */
                page->memcg_data = memcg_data;
        } else if (cmpxchg(&page->memcg_data, 0, memcg_data)) {
                /*
                 * If the slab page is already in use, somebody can allocate
                 * and assign obj_cgroups in parallel. In this case the existing
                 * objcg vector should be reused.
                 */
                kfree(vec);
                return 0;
        }

        kmemleak_not_leak(vec);
        return 0;
}

/*
 * Returns a pointer to the memory cgroup to which the kernel object is charged.
 *
 * A passed kernel object can be a slab object or a generic kernel page, so
 * different mechanisms for getting the memory cgroup pointer should be used.
 * In certain cases (e.g. kernel stacks or large kmallocs with SLUB) the caller
 * can not know for sure how the kernel object is implemented.
 * mem_cgroup_from_obj() can be safely used in such cases.
 *
 * The caller must ensure the memcg lifetime, e.g. by taking rcu_read_lock(),
 * cgroup_mutex, etc.
 */
struct mem_cgroup *mem_cgroup_from_obj(void *p)
{
        struct page *page;

        if (mem_cgroup_disabled())
                return NULL;

        page = virt_to_head_page(p);

        /*
         * Slab objects are accounted individually, not per-page.
         * Memcg membership data for each individual object is saved in
         * the page->obj_cgroups.
         */
        if (page_objcgs_check(page)) {
                struct obj_cgroup *objcg;
                unsigned int off;

                off = obj_to_index(page->slab_cache, page, p);
                objcg = page_objcgs(page)[off];
                if (objcg)
                        return obj_cgroup_memcg(objcg);

                return NULL;
        }

        /*
         * page_memcg_check() is used here, because page_has_obj_cgroups()
         * check above could fail because the object cgroups vector wasn't set
         * at that moment, but it can be set concurrently.
         * page_memcg_check(page) will guarantee that a proper memory
         * cgroup pointer or NULL will be returned.
         */
        return page_memcg_check(page);
}

__always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
{
        struct obj_cgroup *objcg = NULL;
        struct mem_cgroup *memcg;

        if (memcg_kmem_bypass())
                return NULL;

        rcu_read_lock();
        if (unlikely(active_memcg()))
                memcg = active_memcg();
        else
                memcg = mem_cgroup_from_task(current);

        for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) {
                objcg = rcu_dereference(memcg->objcg);
                if (objcg && obj_cgroup_tryget(objcg))
                        break;
                objcg = NULL;
        }
        rcu_read_unlock();

        return objcg;
}

static int memcg_alloc_cache_id(void)
{
        int id, size;
        int err;

        id = ida_simple_get(&memcg_cache_ida,
                            0, MEMCG_CACHES_MAX_SIZE, GFP_KERNEL);
        if (id < 0)
                return id;

        if (id < memcg_nr_cache_ids)
                return id;

        /*
         * There's no space for the new id in memcg_caches arrays,
         * so we have to grow them.
         */
        down_write(&memcg_cache_ids_sem);

        size = 2 * (id + 1);
        if (size < MEMCG_CACHES_MIN_SIZE)
                size = MEMCG_CACHES_MIN_SIZE;
        else if (size > MEMCG_CACHES_MAX_SIZE)
                size = MEMCG_CACHES_MAX_SIZE;

        err = memcg_update_all_list_lrus(size);
        if (!err)
                memcg_nr_cache_ids = size;

        up_write(&memcg_cache_ids_sem);

        if (err) {
                ida_simple_remove(&memcg_cache_ida, id);
                return err;
        }
        return id;
}

static void memcg_free_cache_id(int id)
{
        ida_simple_remove(&memcg_cache_ida, id);
}

/*
 * obj_cgroup_uncharge_pages: uncharge a number of kernel pages from a objcg
 * @objcg: object cgroup to uncharge
 * @nr_pages: number of pages to uncharge
 */
static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg,
                                      unsigned int nr_pages)
{
        struct mem_cgroup *memcg;

        memcg = get_mem_cgroup_from_objcg(objcg);

        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
                page_counter_uncharge(&memcg->kmem, nr_pages);
        refill_stock(memcg, nr_pages);

        css_put(&memcg->css);
}

/*
 * obj_cgroup_charge_pages: charge a number of kernel pages to a objcg
 * @objcg: object cgroup to charge
 * @gfp: reclaim mode
 * @nr_pages: number of pages to charge
 *
 * Returns 0 on success, an error code on failure.
 */
static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp,
                                   unsigned int nr_pages)
{
        struct page_counter *counter;
        struct mem_cgroup *memcg;
        int ret;

        memcg = get_mem_cgroup_from_objcg(objcg);

        ret = try_charge_memcg(memcg, gfp, nr_pages);
        if (ret)
                goto out;

        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
            !page_counter_try_charge(&memcg->kmem, nr_pages, &counter)) {

                /*
                 * Enforce __GFP_NOFAIL allocation because callers are not
                 * prepared to see failures and likely do not have any failure
                 * handling code.
                 */
                if (gfp & __GFP_NOFAIL) {
                        page_counter_charge(&memcg->kmem, nr_pages);
                        goto out;
                }
                cancel_charge(memcg, nr_pages);
                ret = -ENOMEM;
        }
out:
        css_put(&memcg->css);

        return ret;
}

/**
 * __memcg_kmem_charge_page: charge a kmem page to the current memory cgroup
 * @page: page to charge
 * @gfp: reclaim mode
 * @order: allocation order
 *
 * Returns 0 on success, an error code on failure.
 */
int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
{
        struct obj_cgroup *objcg;
        int ret = 0;

        objcg = get_obj_cgroup_from_current();
        if (objcg) {
                ret = obj_cgroup_charge_pages(objcg, gfp, 1 << order);
                if (!ret) {
                        page->memcg_data = (unsigned long)objcg |
                                MEMCG_DATA_KMEM;
                        return 0;
                }
                obj_cgroup_put(objcg);
        }
        return ret;
}

/**
 * __memcg_kmem_uncharge_page: uncharge a kmem page
 * @page: page to uncharge
 * @order: allocation order
 */
void __memcg_kmem_uncharge_page(struct page *page, int order)
{
        struct obj_cgroup *objcg;
        unsigned int nr_pages = 1 << order;

        if (!PageMemcgKmem(page))
                return;

        objcg = __page_objcg(page);
        obj_cgroup_uncharge_pages(objcg, nr_pages);
        page->memcg_data = 0;
        obj_cgroup_put(objcg);
}

void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
                     enum node_stat_item idx, int nr)
{
        unsigned long flags;
        struct obj_stock *stock = get_obj_stock(&flags);
        int *bytes;

        /*
         * Save vmstat data in stock and skip vmstat array update unless
         * accumulating over a page of vmstat data or when pgdat or idx
         * changes.
         */
        if (stock->cached_objcg != objcg) {
                drain_obj_stock(stock);
                obj_cgroup_get(objcg);
                stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes)
                                ? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0;
                stock->cached_objcg = objcg;
                stock->cached_pgdat = pgdat;
        } else if (stock->cached_pgdat != pgdat) {
                /* Flush the existing cached vmstat data */
                struct pglist_data *oldpg = stock->cached_pgdat;

                if (stock->nr_slab_reclaimable_b) {
                        mod_objcg_mlstate(objcg, oldpg, NR_SLAB_RECLAIMABLE_B,
                                          stock->nr_slab_reclaimable_b);
                        stock->nr_slab_reclaimable_b = 0;
                }
                if (stock->nr_slab_unreclaimable_b) {
                        mod_objcg_mlstate(objcg, oldpg, NR_SLAB_UNRECLAIMABLE_B,
                                          stock->nr_slab_unreclaimable_b);
                        stock->nr_slab_unreclaimable_b = 0;
                }
                stock->cached_pgdat = pgdat;
        }

        bytes = (idx == NR_SLAB_RECLAIMABLE_B) ? &stock->nr_slab_reclaimable_b
                                               : &stock->nr_slab_unreclaimable_b;
        /*
         * Even for large object >= PAGE_SIZE, the vmstat data will still be
         * cached locally at least once before pushing it out.
         */
        if (!*bytes) {
                *bytes = nr;
                nr = 0;
        } else {
                *bytes += nr;
                if (abs(*bytes) > PAGE_SIZE) {
                        nr = *bytes;
                        *bytes = 0;
                } else {
                        nr = 0;
                }
        }
        if (nr)
                mod_objcg_mlstate(objcg, pgdat, idx, nr);

        put_obj_stock(flags);
}

static bool consume_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
{
        unsigned long flags;
        struct obj_stock *stock = get_obj_stock(&flags);
        bool ret = false;

        if (objcg == stock->cached_objcg && stock->nr_bytes >= nr_bytes) {
                stock->nr_bytes -= nr_bytes;
                ret = true;
        }

        put_obj_stock(flags);

        return ret;
}

static void drain_obj_stock(struct obj_stock *stock)
{
        struct obj_cgroup *old = stock->cached_objcg;

        if (!old)
                return;

        if (stock->nr_bytes) {
                unsigned int nr_pages = stock->nr_bytes >> PAGE_SHIFT;
                unsigned int nr_bytes = stock->nr_bytes & (PAGE_SIZE - 1);

                if (nr_pages)
                        obj_cgroup_uncharge_pages(old, nr_pages);

                /*
                 * The leftover is flushed to the centralized per-memcg value.
                 * On the next attempt to refill obj stock it will be moved
                 * to a per-cpu stock (probably, on an other CPU), see
                 * refill_obj_stock().
                 *
                 * How often it's flushed is a trade-off between the memory
                 * limit enforcement accuracy and potential CPU contention,
                 * so it might be changed in the future.
                 */
                atomic_add(nr_bytes, &old->nr_charged_bytes);
                stock->nr_bytes = 0;
        }

        /*
         * Flush the vmstat data in current stock
         */
        if (stock->nr_slab_reclaimable_b || stock->nr_slab_unreclaimable_b) {
                if (stock->nr_slab_reclaimable_b) {
                        mod_objcg_mlstate(old, stock->cached_pgdat,
                                          NR_SLAB_RECLAIMABLE_B,
                                          stock->nr_slab_reclaimable_b);
                        stock->nr_slab_reclaimable_b = 0;
                }
                if (stock->nr_slab_unreclaimable_b) {
                        mod_objcg_mlstate(old, stock->cached_pgdat,
                                          NR_SLAB_UNRECLAIMABLE_B,
                                          stock->nr_slab_unreclaimable_b);
                        stock->nr_slab_unreclaimable_b = 0;
                }
                stock->cached_pgdat = NULL;
        }

        obj_cgroup_put(old);
        stock->cached_objcg = NULL;
}

static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
                                     struct mem_cgroup *root_memcg)
{
        struct mem_cgroup *memcg;

        if (in_task() && stock->task_obj.cached_objcg) {
                memcg = obj_cgroup_memcg(stock->task_obj.cached_objcg);
                if (memcg && mem_cgroup_is_descendant(memcg, root_memcg))
                        return true;
        }
        if (stock->irq_obj.cached_objcg) {
                memcg = obj_cgroup_memcg(stock->irq_obj.cached_objcg);
                if (memcg && mem_cgroup_is_descendant(memcg, root_memcg))
                        return true;
        }

        return false;
}

static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
                             bool allow_uncharge)
{
        unsigned long flags;
        struct obj_stock *stock = get_obj_stock(&flags);
        unsigned int nr_pages = 0;

        if (stock->cached_objcg != objcg) { /* reset if necessary */
                drain_obj_stock(stock);
                obj_cgroup_get(objcg);
                stock->cached_objcg = objcg;
                stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes)
                                ? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0;
                allow_uncharge = true;  /* Allow uncharge when objcg changes */
        }
        stock->nr_bytes += nr_bytes;

        if (allow_uncharge && (stock->nr_bytes > PAGE_SIZE)) {
                nr_pages = stock->nr_bytes >> PAGE_SHIFT;
                stock->nr_bytes &= (PAGE_SIZE - 1);
        }

        put_obj_stock(flags);

        if (nr_pages)
                obj_cgroup_uncharge_pages(objcg, nr_pages);
}

int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size)
{
        unsigned int nr_pages, nr_bytes;
        int ret;

        if (consume_obj_stock(objcg, size))
                return 0;

        /*
         * In theory, objcg->nr_charged_bytes can have enough
         * pre-charged bytes to satisfy the allocation. However,
         * flushing objcg->nr_charged_bytes requires two atomic
         * operations, and objcg->nr_charged_bytes can't be big.
         * The shared objcg->nr_charged_bytes can also become a
         * performance bottleneck if all tasks of the same memcg are
         * trying to update it. So it's better to ignore it and try
         * grab some new pages. The stock's nr_bytes will be flushed to
         * objcg->nr_charged_bytes later on when objcg changes.
         *
         * The stock's nr_bytes may contain enough pre-charged bytes
         * to allow one less page from being charged, but we can't rely
         * on the pre-charged bytes not being changed outside of
         * consume_obj_stock() or refill_obj_stock(). So ignore those
         * pre-charged bytes as well when charging pages. To avoid a
         * page uncharge right after a page charge, we set the
         * allow_uncharge flag to false when calling refill_obj_stock()
         * to temporarily allow the pre-charged bytes to exceed the page
         * size limit. The maximum reachable value of the pre-charged
         * bytes is (sizeof(object) + PAGE_SIZE - 2) if there is no data
         * race.
         */
        nr_pages = size >> PAGE_SHIFT;
        nr_bytes = size & (PAGE_SIZE - 1);

        if (nr_bytes)
                nr_pages += 1;

        ret = obj_cgroup_charge_pages(objcg, gfp, nr_pages);
        if (!ret && nr_bytes)
                refill_obj_stock(objcg, PAGE_SIZE - nr_bytes, false);

        return ret;
}

void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size)
{
        refill_obj_stock(objcg, size, true);
}

#endif /* CONFIG_MEMCG_KMEM */

/*
 * Because page_memcg(head) is not set on tails, set it now.
 */
void split_page_memcg(struct page *head, unsigned int nr)
{
        struct mem_cgroup *memcg = page_memcg(head);
        int i;

        if (mem_cgroup_disabled() || !memcg)
                return;

        for (i = 1; i < nr; i++)
                head[i].memcg_data = head->memcg_data;

        if (PageMemcgKmem(head))
                obj_cgroup_get_many(__page_objcg(head), nr - 1);
        else
                css_get_many(&memcg->css, nr - 1);
}

#ifdef CONFIG_MEMCG_SWAP
/**
 * mem_cgroup_move_swap_account - move swap charge and swap_cgroup's record.
 * @entry: swap entry to be moved
 * @from:  mem_cgroup which the entry is moved from
 * @to:  mem_cgroup which the entry is moved to
 *
 * It succeeds only when the swap_cgroup's record for this entry is the same
 * as the mem_cgroup's id of @from.
 *
 * Returns 0 on success, -EINVAL on failure.
 *
 * The caller must have charged to @to, IOW, called page_counter_charge() about
 * both res and memsw, and called css_get().
 */
static int mem_cgroup_move_swap_account(swp_entry_t entry,
                                struct mem_cgroup *from, struct mem_cgroup *to)
{
        unsigned short old_id, new_id;

        old_id = mem_cgroup_id(from);
        new_id = mem_cgroup_id(to);

        if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
                mod_memcg_state(from, MEMCG_SWAP, -1);
                mod_memcg_state(to, MEMCG_SWAP, 1);
                return 0;
        }
        return -EINVAL;
}
#else
static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
                                struct mem_cgroup *from, struct mem_cgroup *to)
{
        return -EINVAL;
}
#endif

static DEFINE_MUTEX(memcg_max_mutex);

static int mem_cgroup_resize_max(struct mem_cgroup *memcg,
                                 unsigned long max, bool memsw)
{
        bool enlarge = false;
        bool drained = false;
        int ret;
        bool limits_invariant;
        struct page_counter *counter = memsw ? &memcg->memsw : &memcg->memory;

        do {
                if (signal_pending(current)) {
                        ret = -EINTR;
                        break;
                }

                mutex_lock(&memcg_max_mutex);
                /*
                 * Make sure that the new limit (memsw or memory limit) doesn't
                 * break our basic invariant rule memory.max <= memsw.max.
                 */
                limits_invariant = memsw ? max >= READ_ONCE(memcg->memory.max) :
                                           max <= memcg->memsw.max;
                if (!limits_invariant) {
                        mutex_unlock(&memcg_max_mutex);
                        ret = -EINVAL;
                        break;
                }
                if (max > counter->max)
                        enlarge = true;
                ret = page_counter_set_max(counter, max);
                mutex_unlock(&memcg_max_mutex);

                if (!ret)
                        break;

                if (!drained) {
                        drain_all_stock(memcg);
                        drained = true;
                        continue;
                }

                if (!try_to_free_mem_cgroup_pages(memcg, 1,
                                        GFP_KERNEL, !memsw)) {
                        ret = -EBUSY;
                        break;
                }
        } while (true);

        if (!ret && enlarge)
                memcg_oom_recover(memcg);

        return ret;
}

unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
                                            gfp_t gfp_mask,
                                            unsigned long *total_scanned)
{
        unsigned long nr_reclaimed = 0;
        struct mem_cgroup_per_node *mz, *next_mz = NULL;
        unsigned long reclaimed;
        int loop = 0;
        struct mem_cgroup_tree_per_node *mctz;
        unsigned long excess;
        unsigned long nr_scanned;

        if (order > 0)
                return 0;

        mctz = soft_limit_tree_node(pgdat->node_id);

        /*
         * Do not even bother to check the largest node if the root
         * is empty. Do it lockless to prevent lock bouncing. Races
         * are acceptable as soft limit is best effort anyway.
         */
        if (!mctz || RB_EMPTY_ROOT(&mctz->rb_root))
                return 0;

        /*
         * This loop can run a while, specially if mem_cgroup's continuously
         * keep exceeding their soft limit and putting the system under
         * pressure
         */
        do {
                if (next_mz)
                        mz = next_mz;
                else
                        mz = mem_cgroup_largest_soft_limit_node(mctz);
                if (!mz)
                        break;

                nr_scanned = 0;
                reclaimed = mem_cgroup_soft_reclaim(mz->memcg, pgdat,
                                                    gfp_mask, &nr_scanned);
                nr_reclaimed += reclaimed;
                *total_scanned += nr_scanned;
                spin_lock_irq(&mctz->lock);
                __mem_cgroup_remove_exceeded(mz, mctz);

                /*
                 * If we failed to reclaim anything from this memory cgroup
                 * it is time to move on to the next cgroup
                 */
                next_mz = NULL;
                if (!reclaimed)
                        next_mz = __mem_cgroup_largest_soft_limit_node(mctz);

                excess = soft_limit_excess(mz->memcg);
                /*
                 * One school of thought says that we should not add
                 * back the node to the tree if reclaim returns 0.
                 * But our reclaim could return 0, simply because due
                 * to priority we are exposing a smaller subset of
                 * memory to reclaim from. Consider this as a longer
                 * term TODO.
                 */
                /* If excess == 0, no tree ops */
                __mem_cgroup_insert_exceeded(mz, mctz, excess);
                spin_unlock_irq(&mctz->lock);
                css_put(&mz->memcg->css);
                loop++;
                /*
                 * Could not reclaim anything and there are no more
                 * mem cgroups to try or we seem to be looping without
                 * reclaiming anything.
                 */
                if (!nr_reclaimed &&
                        (next_mz == NULL ||
                        loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
                        break;
        } while (!nr_reclaimed);
        if (next_mz)
                css_put(&next_mz->memcg->css);
        return nr_reclaimed;
}

/*
 * Reclaims as many pages from the given memcg as possible.
 *
 * Caller is responsible for holding css reference for memcg.
 */
static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
{
        int nr_retries = MAX_RECLAIM_RETRIES;

        /* we call try-to-free pages for make this cgroup empty */
        lru_add_drain_all();

        drain_all_stock(memcg);

        /* try to free all pages in this cgroup */
        while (nr_retries && page_counter_read(&memcg->memory)) {
                int progress;

                if (signal_pending(current))
                        return -EINTR;

                progress = try_to_free_mem_cgroup_pages(memcg, 1,
                                                        GFP_KERNEL, true);
                if (!progress) {
                        nr_retries--;
                        /* maybe some writeback is necessary */
                        congestion_wait(BLK_RW_ASYNC, HZ/10);
                }

        }

        return 0;
}

static ssize_t mem_cgroup_force_empty_write(struct kernfs_open_file *of,
                                            char *buf, size_t nbytes,
                                            loff_t off)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));

        if (mem_cgroup_is_root(memcg))
                return -EINVAL;
        return mem_cgroup_force_empty(memcg) ?: nbytes;
}

static u64 mem_cgroup_hierarchy_read(struct cgroup_subsys_state *css,
                                     struct cftype *cft)
{
        return 1;
}

static int mem_cgroup_hierarchy_write(struct cgroup_subsys_state *css,
                                      struct cftype *cft, u64 val)
{
        if (val == 1)
                return 0;

        pr_warn_once("Non-hierarchical mode is deprecated. "
                     "Please report your usecase to linux-mm@kvack.org if you "
                     "depend on this functionality.\n");

        return -EINVAL;
}

static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
{
        unsigned long val;

        if (mem_cgroup_is_root(memcg)) {
                /* mem_cgroup_threshold() calls here from irqsafe context */
                cgroup_rstat_flush_irqsafe(memcg->css.cgroup);
                val = memcg_page_state(memcg, NR_FILE_PAGES) +
                        memcg_page_state(memcg, NR_ANON_MAPPED);
                if (swap)
                        val += memcg_page_state(memcg, MEMCG_SWAP);
        } else {
                if (!swap)
                        val = page_counter_read(&memcg->memory);
                else
                        val = page_counter_read(&memcg->memsw);
        }
        return val;
}

enum {
        RES_USAGE,
        RES_LIMIT,
        RES_MAX_USAGE,
        RES_FAILCNT,
        RES_SOFT_LIMIT,
};

static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
                               struct cftype *cft)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);
        struct page_counter *counter;

        switch (MEMFILE_TYPE(cft->private)) {
        case _MEM:
                counter = &memcg->memory;
                break;
        case _MEMSWAP:
                counter = &memcg->memsw;
                break;
        case _KMEM:
                counter = &memcg->kmem;
                break;
        case _TCP:
                counter = &memcg->tcpmem;
                break;
        default:
                BUG();
        }

        switch (MEMFILE_ATTR(cft->private)) {
        case RES_USAGE:
                if (counter == &memcg->memory)
                        return (u64)mem_cgroup_usage(memcg, false) * PAGE_SIZE;
                if (counter == &memcg->memsw)
                        return (u64)mem_cgroup_usage(memcg, true) * PAGE_SIZE;
                return (u64)page_counter_read(counter) * PAGE_SIZE;
        case RES_LIMIT:
                return (u64)counter->max * PAGE_SIZE;
        case RES_MAX_USAGE:
                return (u64)counter->watermark * PAGE_SIZE;
        case RES_FAILCNT:
                return counter->failcnt;
        case RES_SOFT_LIMIT:
                return (u64)memcg->soft_limit * PAGE_SIZE;
        default:
                BUG();
        }
}

#ifdef CONFIG_MEMCG_KMEM
static int memcg_online_kmem(struct mem_cgroup *memcg)
{
        struct obj_cgroup *objcg;
        int memcg_id;

        if (cgroup_memory_nokmem)
                return 0;

        BUG_ON(memcg->kmemcg_id >= 0);
        BUG_ON(memcg->kmem_state);

        memcg_id = memcg_alloc_cache_id();
        if (memcg_id < 0)
                return memcg_id;

        objcg = obj_cgroup_alloc();
        if (!objcg) {
                memcg_free_cache_id(memcg_id);
                return -ENOMEM;
        }
        objcg->memcg = memcg;
        rcu_assign_pointer(memcg->objcg, objcg);

        static_branch_enable(&memcg_kmem_enabled_key);

        memcg->kmemcg_id = memcg_id;
        memcg->kmem_state = KMEM_ONLINE;

        return 0;
}

static void memcg_offline_kmem(struct mem_cgroup *memcg)
{
        struct cgroup_subsys_state *css;
        struct mem_cgroup *parent, *child;
        int kmemcg_id;

        if (memcg->kmem_state != KMEM_ONLINE)
                return;

        memcg->kmem_state = KMEM_ALLOCATED;

        parent = parent_mem_cgroup(memcg);
        if (!parent)
                parent = root_mem_cgroup;

        memcg_reparent_objcgs(memcg, parent);

        kmemcg_id = memcg->kmemcg_id;
        BUG_ON(kmemcg_id < 0);

        /*
         * Change kmemcg_id of this cgroup and all its descendants to the
         * parent's id, and then move all entries from this cgroup's list_lrus
         * to ones of the parent. After we have finished, all list_lrus
         * corresponding to this cgroup are guaranteed to remain empty. The
         * ordering is imposed by list_lru_node->lock taken by
         * memcg_drain_all_list_lrus().
         */
        rcu_read_lock(); /* can be called from css_free w/o cgroup_mutex */
        css_for_each_descendant_pre(css, &memcg->css) {
                child = mem_cgroup_from_css(css);
                BUG_ON(child->kmemcg_id != kmemcg_id);
                child->kmemcg_id = parent->kmemcg_id;
        }
        rcu_read_unlock();

        memcg_drain_all_list_lrus(kmemcg_id, parent);

        memcg_free_cache_id(kmemcg_id);
}

static void memcg_free_kmem(struct mem_cgroup *memcg)
{
        /* css_alloc() failed, offlining didn't happen */
        if (unlikely(memcg->kmem_state == KMEM_ONLINE))
                memcg_offline_kmem(memcg);
}
#else
static int memcg_online_kmem(struct mem_cgroup *memcg)
{
        return 0;
}
static void memcg_offline_kmem(struct mem_cgroup *memcg)
{
}
static void memcg_free_kmem(struct mem_cgroup *memcg)
{
}
#endif /* CONFIG_MEMCG_KMEM */

static int memcg_update_kmem_max(struct mem_cgroup *memcg,
                                 unsigned long max)
{
        int ret;

        mutex_lock(&memcg_max_mutex);
        ret = page_counter_set_max(&memcg->kmem, max);
        mutex_unlock(&memcg_max_mutex);
        return ret;
}

static int memcg_update_tcp_max(struct mem_cgroup *memcg, unsigned long max)
{
        int ret;

        mutex_lock(&memcg_max_mutex);

        ret = page_counter_set_max(&memcg->tcpmem, max);
        if (ret)
                goto out;

        if (!memcg->tcpmem_active) {
                /*
                 * The active flag needs to be written after the static_key
                 * update. This is what guarantees that the socket activation
                 * function is the last one to run. See mem_cgroup_sk_alloc()
                 * for details, and note that we don't mark any socket as
                 * belonging to this memcg until that flag is up.
                 *
                 * We need to do this, because static_keys will span multiple
                 * sites, but we can't control their order. If we mark a socket
                 * as accounted, but the accounting functions are not patched in
                 * yet, we'll lose accounting.
                 *
                 * We never race with the readers in mem_cgroup_sk_alloc(),
                 * because when this value change, the code to process it is not
                 * patched in yet.
                 */
                static_branch_inc(&memcg_sockets_enabled_key);
                memcg->tcpmem_active = true;
        }
out:
        mutex_unlock(&memcg_max_mutex);
        return ret;
}

/*
 * The user of this function is...
 * RES_LIMIT.
 */
static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
                                char *buf, size_t nbytes, loff_t off)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
        unsigned long nr_pages;
        int ret;

        buf = strstrip(buf);
        ret = page_counter_memparse(buf, "-1", &nr_pages);
        if (ret)
                return ret;

        switch (MEMFILE_ATTR(of_cft(of)->private)) {
        case RES_LIMIT:
                if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
                        ret = -EINVAL;
                        break;
                }
                switch (MEMFILE_TYPE(of_cft(of)->private)) {
                case _MEM:
                        ret = mem_cgroup_resize_max(memcg, nr_pages, false);
                        break;
                case _MEMSWAP:
                        ret = mem_cgroup_resize_max(memcg, nr_pages, true);
                        break;
                case _KMEM:
                        pr_warn_once("kmem.limit_in_bytes is deprecated and will be removed. "
                                     "Please report your usecase to linux-mm@kvack.org if you "
                                     "depend on this functionality.\n");
                        ret = memcg_update_kmem_max(memcg, nr_pages);
                        break;
                case _TCP:
                        ret = memcg_update_tcp_max(memcg, nr_pages);
                        break;
                }
                break;
        case RES_SOFT_LIMIT:
                memcg->soft_limit = nr_pages;
                ret = 0;
                break;
        }
        return ret ?: nbytes;
}

static ssize_t mem_cgroup_reset(struct kernfs_open_file *of, char *buf,
                                size_t nbytes, loff_t off)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
        struct page_counter *counter;

        switch (MEMFILE_TYPE(of_cft(of)->private)) {
        case _MEM:
                counter = &memcg->memory;
                break;
        case _MEMSWAP:
                counter = &memcg->memsw;
                break;
        case _KMEM:
                counter = &memcg->kmem;
                break;
        case _TCP:
                counter = &memcg->tcpmem;
                break;
        default:
                BUG();
        }

        switch (MEMFILE_ATTR(of_cft(of)->private)) {
        case RES_MAX_USAGE:
                page_counter_reset_watermark(counter);
                break;
        case RES_FAILCNT:
                counter->failcnt = 0;
                break;
        default:
                BUG();
        }

        return nbytes;
}

static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state *css,
                                        struct cftype *cft)
{
        return mem_cgroup_from_css(css)->move_charge_at_immigrate;
}

#ifdef CONFIG_MMU
static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
                                        struct cftype *cft, u64 val)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);

        if (val & ~MOVE_MASK)
                return -EINVAL;

        /*
         * No kind of locking is needed in here, because ->can_attach() will
         * check this value once in the beginning of the process, and then carry
         * on with stale data. This means that changes to this value will only
         * affect task migrations starting after the change.
         */
        memcg->move_charge_at_immigrate = val;
        return 0;
}
#else
static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
                                        struct cftype *cft, u64 val)
{
        return -ENOSYS;
}
#endif

#ifdef CONFIG_NUMA

#define LRU_ALL_FILE (BIT(LRU_INACTIVE_FILE) | BIT(LRU_ACTIVE_FILE))
#define LRU_ALL_ANON (BIT(LRU_INACTIVE_ANON) | BIT(LRU_ACTIVE_ANON))
#define LRU_ALL      ((1 << NR_LRU_LISTS) - 1)

static unsigned long mem_cgroup_node_nr_lru_pages(struct mem_cgroup *memcg,
                                int nid, unsigned int lru_mask, bool tree)
{
        struct lruvec *lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(nid));
        unsigned long nr = 0;
        enum lru_list lru;

        VM_BUG_ON((unsigned)nid >= nr_node_ids);

        for_each_lru(lru) {
                if (!(BIT(lru) & lru_mask))
                        continue;
                if (tree)
                        nr += lruvec_page_state(lruvec, NR_LRU_BASE + lru);
                else
                        nr += lruvec_page_state_local(lruvec, NR_LRU_BASE + lru);
        }
        return nr;
}

static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg,
                                             unsigned int lru_mask,
                                             bool tree)
{
        unsigned long nr = 0;
        enum lru_list lru;

        for_each_lru(lru) {
                if (!(BIT(lru) & lru_mask))
                        continue;
                if (tree)
                        nr += memcg_page_state(memcg, NR_LRU_BASE + lru);
                else
                        nr += memcg_page_state_local(memcg, NR_LRU_BASE + lru);
        }
        return nr;
}

static int memcg_numa_stat_show(struct seq_file *m, void *v)
{
        struct numa_stat {
                const char *name;
                unsigned int lru_mask;
        };

        static const struct numa_stat stats[] = {
                { "total", LRU_ALL },
                { "file", LRU_ALL_FILE },
                { "anon", LRU_ALL_ANON },
                { "unevictable", BIT(LRU_UNEVICTABLE) },
        };
        const struct numa_stat *stat;
        int nid;
        struct mem_cgroup *memcg = mem_cgroup_from_seq(m);

        cgroup_rstat_flush(memcg->css.cgroup);

        for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
                seq_printf(m, "%s=%lu", stat->name,
                           mem_cgroup_nr_lru_pages(memcg, stat->lru_mask,
                                                   false));
                for_each_node_state(nid, N_MEMORY)
                        seq_printf(m, " N%d=%lu", nid,
                                   mem_cgroup_node_nr_lru_pages(memcg, nid,
                                                        stat->lru_mask, false));
                seq_putc(m, '\n');
        }

        for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {

                seq_printf(m, "hierarchical_%s=%lu", stat->name,
                           mem_cgroup_nr_lru_pages(memcg, stat->lru_mask,
                                                   true));
                for_each_node_state(nid, N_MEMORY)
                        seq_printf(m, " N%d=%lu", nid,
                                   mem_cgroup_node_nr_lru_pages(memcg, nid,
                                                        stat->lru_mask, true));
                seq_putc(m, '\n');
        }

        return 0;
}
#endif /* CONFIG_NUMA */

static const unsigned int memcg1_stats[] = {
        NR_FILE_PAGES,
        NR_ANON_MAPPED,
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        NR_ANON_THPS,
#endif
        NR_SHMEM,
        NR_FILE_MAPPED,
        NR_FILE_DIRTY,
        NR_WRITEBACK,
        MEMCG_SWAP,