// SPDX-License-Identifier: GPL-2.0-or-later

#include <linux/memcontrol.h>
#include <linux/swap.h>
#include <linux/mm_inline.h>
#include <linux/pagewalk.h>
#include <linux/backing-dev.h>
#include <linux/swap_cgroup.h>
#include <linux/eventfd.h>
#include <linux/poll.h>
#include <linux/sort.h>
#include <linux/file.h>
#include <linux/seq_buf.h>

#include "internal.h"
#include "swap.h"
#include "memcontrol-v1.h"

/*
 * 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;

/*
 * Maximum loops in mem_cgroup_soft_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 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;
};

#define MEMFILE_PRIVATE(x, val) ((x) << 16 | (val))
#define MEMFILE_TYPE(val)       ((val) >> 16 & 0xffff)
#define MEMFILE_ATTR(val)       ((val) & 0xffff)

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

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

DEFINE_SPINLOCK(memcg_oom_lock);

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 memcg1_update_tree(struct mem_cgroup *memcg, int nid)
{
        unsigned long excess;
        struct mem_cgroup_per_node *mz;
        struct mem_cgroup_tree_per_node *mctz;

        if (lru_gen_enabled()) {
                if (soft_limit_excess(memcg))
                        lru_gen_soft_reclaim(memcg, nid);
                return;
        }

        mctz = soft_limit_tree.rb_tree_per_node[nid];
        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 = memcg->nodeinfo[nid];
                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);
                }
        }
}

void memcg1_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.rb_tree_per_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;
}

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;
}

unsigned long memcg1_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;

        if (lru_gen_enabled())
                return 0;

        if (order > 0)
                return 0;

        mctz = soft_limit_tree.rb_tree_per_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;

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

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

static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state *css,
                                struct cftype *cft)
{
        return 0;
}

#ifdef CONFIG_MMU
static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
                                 struct cftype *cft, u64 val)
{
        pr_warn_once("Cgroup memory moving (move_charge_at_immigrate) is deprecated. "
                     "Please report your usecase to linux-mm@kvack.org if you "
                     "depend on this functionality.\n");

        if (val != 0)
                return -EINVAL;
        return 0;
}
#else
static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
                                 struct cftype *cft, u64 val)
{
        return -ENOSYS;
}
#endif

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

        if (mem_cgroup_is_root(memcg)) {
                /*
                 * Approximate root's usage from global state. This isn't
                 * perfect, but the root usage was always an approximation.
                 */
                val = global_node_page_state(NR_FILE_PAGES) +
                        global_node_page_state(NR_ANON_MAPPED);
                if (swap)
                        val += total_swap_pages - get_nr_swap_pages();
        } else {
                if (!swap)
                        val = page_counter_read(&memcg->memory);
                else
                        val = page_counter_read(&memcg->memsw);
        }
        return val;
}

static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
{
        struct mem_cgroup_threshold_ary *t;
        unsigned long usage;
        int i;

        rcu_read_lock();
        if (!swap)
                t = rcu_dereference(memcg->thresholds.primary);
        else
                t = rcu_dereference(memcg->memsw_thresholds.primary);

        if (!t)
                goto unlock;

        usage = mem_cgroup_usage(memcg, swap);

        /*
         * current_threshold points to threshold just below or equal to usage.
         * If it's not true, a threshold was crossed after last
         * call of __mem_cgroup_threshold().
         */
        i = t->current_threshold;

        /*
         * Iterate backward over array of thresholds starting from
         * current_threshold and check if a threshold is crossed.
         * If none of thresholds below usage is crossed, we read
         * only one element of the array here.
         */
        for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--)
                eventfd_signal(t->entries[i].eventfd);

        /* i = current_threshold + 1 */
        i++;

        /*
         * Iterate forward over array of thresholds starting from
         * current_threshold+1 and check if a threshold is crossed.
         * If none of thresholds above usage is crossed, we read
         * only one element of the array here.
         */
        for (; i < t->size && unlikely(t->entries[i].threshold <= usage); i++)
                eventfd_signal(t->entries[i].eventfd);

        /* Update current_threshold */
        t->current_threshold = i - 1;
unlock:
        rcu_read_unlock();
}

static void mem_cgroup_threshold(struct mem_cgroup *memcg)
{
        while (memcg) {
                __mem_cgroup_threshold(memcg, false);
                if (do_memsw_account())
                        __mem_cgroup_threshold(memcg, true);

                memcg = parent_mem_cgroup(memcg);
        }
}

/* Cgroup1: threshold notifications & softlimit tree updates */

/*
 * Per memcg event counter is incremented at every pagein/pageout. With THP,
 * it will be incremented by the number of pages. This counter is used
 * to trigger some periodic events. This is straightforward and better
 * than using jiffies etc. to handle periodic memcg event.
 */
enum mem_cgroup_events_target {
        MEM_CGROUP_TARGET_THRESH,
        MEM_CGROUP_TARGET_SOFTLIMIT,
        MEM_CGROUP_NTARGETS,
};

struct memcg1_events_percpu {
        unsigned long nr_page_events;
        unsigned long targets[MEM_CGROUP_NTARGETS];
};

static void memcg1_charge_statistics(struct mem_cgroup *memcg, 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->events_percpu->nr_page_events, nr_pages);
}

#define THRESHOLDS_EVENTS_TARGET 128
#define SOFTLIMIT_EVENTS_TARGET 1024

static bool memcg1_event_ratelimit(struct mem_cgroup *memcg,
                                enum mem_cgroup_events_target target)
{
        unsigned long val, next;

        val = __this_cpu_read(memcg->events_percpu->nr_page_events);
        next = __this_cpu_read(memcg->events_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->events_percpu->targets[target], next);
                return true;
        }
        return false;
}

/*
 * Check events in order.
 *
 */
static void memcg1_check_events(struct mem_cgroup *memcg, int nid)
{
        if (IS_ENABLED(CONFIG_PREEMPT_RT))
                return;

        /* threshold event is triggered in finer grain than soft limit */
        if (unlikely(memcg1_event_ratelimit(memcg,
                                                MEM_CGROUP_TARGET_THRESH))) {
                bool do_softlimit;

                do_softlimit = memcg1_event_ratelimit(memcg,
                                                MEM_CGROUP_TARGET_SOFTLIMIT);
                mem_cgroup_threshold(memcg);
                if (unlikely(do_softlimit))
                        memcg1_update_tree(memcg, nid);
        }
}

void memcg1_commit_charge(struct folio *folio, struct mem_cgroup *memcg)
{
        unsigned long flags;

        local_irq_save(flags);
        memcg1_charge_statistics(memcg, folio_nr_pages(folio));
        memcg1_check_events(memcg, folio_nid(folio));
        local_irq_restore(flags);
}

/**
 * memcg1_swapout - transfer a memsw charge to swap
 * @folio: folio whose memsw charge to transfer
 * @entry: swap entry to move the charge to
 *
 * Transfer the memsw charge of @folio to @entry.
 */
void memcg1_swapout(struct folio *folio, swp_entry_t entry)
{
        struct mem_cgroup *memcg, *swap_memcg;
        unsigned int nr_entries;

        VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
        VM_BUG_ON_FOLIO(folio_ref_count(folio), folio);

        if (mem_cgroup_disabled())
                return;

        if (!do_memsw_account())
                return;

        memcg = folio_memcg(folio);

        VM_WARN_ON_ONCE_FOLIO(!memcg, folio);
        if (!memcg)
                return;

        /*
         * In case the memcg owning these pages has been offlined and doesn't
         * have an ID allocated to it anymore, charge the closest online
         * ancestor for the swap instead and transfer the memory+swap charge.
         */
        swap_memcg = mem_cgroup_private_id_get_online(memcg);
        nr_entries = folio_nr_pages(folio);
        /* Get references for the tail pages, too */
        if (nr_entries > 1)
                mem_cgroup_private_id_get_many(swap_memcg, nr_entries - 1);
        mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);

        swap_cgroup_record(folio, mem_cgroup_private_id(swap_memcg), entry);

        folio_unqueue_deferred_split(folio);
        folio->memcg_data = 0;

        if (!mem_cgroup_is_root(memcg))
                page_counter_uncharge(&memcg->memory, nr_entries);

        if (memcg != swap_memcg) {
                if (!mem_cgroup_is_root(swap_memcg))
                        page_counter_charge(&swap_memcg->memsw, nr_entries);
                page_counter_uncharge(&memcg->memsw, nr_entries);
        }

        /*
         * Interrupts should be disabled here because the caller holds the
         * i_pages lock which is taken with interrupts-off. It is
         * important here to have the interrupts disabled because it is the
         * only synchronisation we have for updating the per-CPU variables.
         */
        preempt_disable_nested();
        VM_WARN_ON_IRQS_ENABLED();
        memcg1_charge_statistics(memcg, -folio_nr_pages(folio));
        preempt_enable_nested();
        memcg1_check_events(memcg, folio_nid(folio));

        css_put(&memcg->css);
}

/*
 * memcg1_swapin - uncharge swap slot
 * @entry: the first swap entry for which the pages are charged
 * @nr_pages: number of pages which will be uncharged
 *
 * Call this function after successfully adding the charged page to swapcache.
 *
 * Note: This function assumes the page for which swap slot is being uncharged
 * is order 0 page.
 */
void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages)
{
        /*
         * Cgroup1's unified memory+swap counter has been charged with the
         * new swapcache page, finish the transfer by uncharging the swap
         * slot. The swap slot would also get uncharged when it dies, but
         * it can stick around indefinitely and we'd count the page twice
         * the entire time.
         *
         * Cgroup2 has separate resource counters for memory and swap,
         * so this is a non-issue here. Memory and swap charge lifetimes
         * correspond 1:1 to page and swap slot lifetimes: we charge the
         * page to memory here, and uncharge swap when the slot is freed.
         */
        if (do_memsw_account()) {
                /*
                 * The swap entry might not get freed for a long time,
                 * let's not wait for it.  The page already received a
                 * memory+swap charge, drop the swap entry duplicate.
                 */
                mem_cgroup_uncharge_swap(entry, nr_pages);
        }
}

void memcg1_uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
                           unsigned long nr_memory, int nid)
{
        unsigned long flags;

        local_irq_save(flags);
        count_memcg_events(memcg, PGPGOUT, pgpgout);
        __this_cpu_add(memcg->events_percpu->nr_page_events, nr_memory);
        memcg1_check_events(memcg, nid);
        local_irq_restore(flags);
}

static int compare_thresholds(const void *a, const void *b)
{
        const struct mem_cgroup_threshold *_a = a;
        const struct mem_cgroup_threshold *_b = b;

        if (_a->threshold > _b->threshold)
                return 1;

        if (_a->threshold < _b->threshold)
                return -1;

        return 0;
}

static int mem_cgroup_oom_notify_cb(struct mem_cgroup *memcg)
{
        struct mem_cgroup_eventfd_list *ev;

        spin_lock(&memcg_oom_lock);

        list_for_each_entry(ev, &memcg->oom_notify, list)
                eventfd_signal(ev->eventfd);

        spin_unlock(&memcg_oom_lock);
        return 0;
}

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

        for_each_mem_cgroup_tree(iter, memcg)
                mem_cgroup_oom_notify_cb(iter);
}

static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
        struct eventfd_ctx *eventfd, const char *args, enum res_type type)
{
        struct mem_cgroup_thresholds *thresholds;
        struct mem_cgroup_threshold_ary *new;
        unsigned long threshold;
        unsigned long usage;
        int i, size, ret;

        ret = page_counter_memparse(args, "-1", &threshold);
        if (ret)
                return ret;

        mutex_lock(&memcg->thresholds_lock);

        if (type == _MEM) {
                thresholds = &memcg->thresholds;
                usage = mem_cgroup_usage(memcg, false);
        } else if (type == _MEMSWAP) {
                thresholds = &memcg->memsw_thresholds;
                usage = mem_cgroup_usage(memcg, true);
        } else
                BUG();

        /* Check if a threshold crossed before adding a new one */
        if (thresholds->primary)
                __mem_cgroup_threshold(memcg, type == _MEMSWAP);

        size = thresholds->primary ? thresholds->primary->size + 1 : 1;

        /* Allocate memory for new array of thresholds */
        new = kmalloc_flex(*new, entries, size, GFP_KERNEL_ACCOUNT);
        if (!new) {
                ret = -ENOMEM;
                goto unlock;
        }
        new->size = size;

        /* Copy thresholds (if any) to new array */
        if (thresholds->primary)
                memcpy(new->entries, thresholds->primary->entries,
                       flex_array_size(new, entries, size - 1));

        /* Add new threshold */
        new->entries[size - 1].eventfd = eventfd;
        new->entries[size - 1].threshold = threshold;

        /* Sort thresholds. Registering of new threshold isn't time-critical */
        sort(new->entries, size, sizeof(*new->entries),
                        compare_thresholds, NULL);

        /* Find current threshold */
        new->current_threshold = -1;
        for (i = 0; i < size; i++) {
                if (new->entries[i].threshold <= usage) {
                        /*
                         * new->current_threshold will not be used until
                         * rcu_assign_pointer(), so it's safe to increment
                         * it here.
                         */
                        ++new->current_threshold;
                } else
                        break;
        }

        /* Free old spare buffer and save old primary buffer as spare */
        kfree(thresholds->spare);
        thresholds->spare = thresholds->primary;

        rcu_assign_pointer(thresholds->primary, new);

        /* To be sure that nobody uses thresholds */
        synchronize_rcu();

unlock:
        mutex_unlock(&memcg->thresholds_lock);

        return ret;
}

static int mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
        struct eventfd_ctx *eventfd, const char *args)
{
        return __mem_cgroup_usage_register_event(memcg, eventfd, args, _MEM);
}

static int memsw_cgroup_usage_register_event(struct mem_cgroup *memcg,
        struct eventfd_ctx *eventfd, const char *args)
{
        return __mem_cgroup_usage_register_event(memcg, eventfd, args, _MEMSWAP);
}

static void __mem_cgroup_usage_unregister_event(struct mem_cgroup *memcg,
        struct eventfd_ctx *eventfd, enum res_type type)
{
        struct mem_cgroup_thresholds *thresholds;
        struct mem_cgroup_threshold_ary *new;
        unsigned long usage;
        int i, j, size, entries;

        mutex_lock(&memcg->thresholds_lock);

        if (type == _MEM) {
                thresholds = &memcg->thresholds;
                usage = mem_cgroup_usage(memcg, false);
        } else if (type == _MEMSWAP) {
                thresholds = &memcg->memsw_thresholds;
                usage = mem_cgroup_usage(memcg, true);
        } else
                BUG();

        if (!thresholds->primary)
                goto unlock;

        /* Check if a threshold crossed before removing */
        __mem_cgroup_threshold(memcg, type == _MEMSWAP);

        /* Calculate new number of threshold */
        size = entries = 0;
        for (i = 0; i < thresholds->primary->size; i++) {
                if (thresholds->primary->entries[i].eventfd != eventfd)
                        size++;
                else
                        entries++;
        }

        new = thresholds->spare;

        /* If no items related to eventfd have been cleared, nothing to do */
        if (!entries)
                goto unlock;

        /* Set thresholds array to NULL if we don't have thresholds */
        if (!size) {
                kfree(new);
                new = NULL;
                goto swap_buffers;
        }

        new->size = size;

        /* Copy thresholds and find current threshold */
        new->current_threshold = -1;
        for (i = 0, j = 0; i < thresholds->primary->size; i++) {
                if (thresholds->primary->entries[i].eventfd == eventfd)
                        continue;

                new->entries[j] = thresholds->primary->entries[i];
                if (new->entries[j].threshold <= usage) {
                        /*
                         * new->current_threshold will not be used
                         * until rcu_assign_pointer(), so it's safe to increment
                         * it here.
                         */
                        ++new->current_threshold;
                }
                j++;
        }

swap_buffers:
        /* Swap primary and spare array */
        thresholds->spare = thresholds->primary;

        rcu_assign_pointer(thresholds->primary, new);

        /* To be sure that nobody uses thresholds */
        synchronize_rcu();

        /* If all events are unregistered, free the spare array */
        if (!new) {
                kfree(thresholds->spare);
                thresholds->spare = NULL;
        }
unlock:
        mutex_unlock(&memcg->thresholds_lock);
}

static void mem_cgroup_usage_unregister_event(struct mem_cgroup *memcg,
        struct eventfd_ctx *eventfd)
{
        return __mem_cgroup_usage_unregister_event(memcg, eventfd, _MEM);
}

static void memsw_cgroup_usage_unregister_event(struct mem_cgroup *memcg,
        struct eventfd_ctx *eventfd)
{
        return __mem_cgroup_usage_unregister_event(memcg, eventfd, _MEMSWAP);
}

static int mem_cgroup_oom_register_event(struct mem_cgroup *memcg,
        struct eventfd_ctx *eventfd, const char *args)
{
        struct mem_cgroup_eventfd_list *event;

        event = kmalloc_obj(*event, GFP_KERNEL_ACCOUNT);
        if (!event)
                return -ENOMEM;

        spin_lock(&memcg_oom_lock);

        event->eventfd = eventfd;
        list_add(&event->list, &memcg->oom_notify);

        /* already in OOM ? */
        if (memcg->under_oom)
                eventfd_signal(eventfd);
        spin_unlock(&memcg_oom_lock);

        return 0;
}

static void mem_cgroup_oom_unregister_event(struct mem_cgroup *memcg,
        struct eventfd_ctx *eventfd)
{
        struct mem_cgroup_eventfd_list *ev, *tmp;

        spin_lock(&memcg_oom_lock);

        list_for_each_entry_safe(ev, tmp, &memcg->oom_notify, list) {
                if (ev->eventfd == eventfd) {
                        list_del(&ev->list);
                        kfree(ev);
                }
        }

        spin_unlock(&memcg_oom_lock);
}

/*
 * DO NOT USE IN NEW FILES.
 *
 * "cgroup.event_control" implementation.
 *
 * This is way over-engineered.  It tries to support fully configurable
 * events for each user.  Such level of flexibility is completely
 * unnecessary especially in the light of the planned unified hierarchy.
 *
 * Please deprecate this and replace with something simpler if at all
 * possible.
 */

/*
 * Unregister event and free resources.
 *
 * Gets called from workqueue.
 */
static void memcg_event_remove(struct work_struct *work)
{
        struct mem_cgroup_event *event =
                container_of(work, struct mem_cgroup_event, remove);
        struct mem_cgroup *memcg = event->memcg;

        remove_wait_queue(event->wqh, &event->wait);

        event->unregister_event(memcg, event->eventfd);

        /* Notify userspace the event is going away. */
        eventfd_signal(event->eventfd);

        eventfd_ctx_put(event->eventfd);
        kfree(event);
        css_put(&memcg->css);
}

/*
 * Gets called on EPOLLHUP on eventfd when user closes it.
 *
 * Called with wqh->lock held and interrupts disabled.
 */
static int memcg_event_wake(wait_queue_entry_t *wait, unsigned int mode,
                            int sync, void *key)
{
        struct mem_cgroup_event *event =
                container_of(wait, struct mem_cgroup_event, wait);
        struct mem_cgroup *memcg = event->memcg;
        __poll_t flags = key_to_poll(key);

        if (flags & EPOLLHUP) {
                /*
                 * If the event has been detached at cgroup removal, we
                 * can simply return knowing the other side will cleanup
                 * for us.
                 *
                 * We can't race against event freeing since the other
                 * side will require wqh->lock via remove_wait_queue(),
                 * which we hold.
                 */
                spin_lock(&memcg->event_list_lock);
                if (!list_empty(&event->list)) {
                        list_del_init(&event->list);
                        /*
                         * We are in atomic context, but cgroup_event_remove()
                         * may sleep, so we have to call it in workqueue.
                         */
                        schedule_work(&event->remove);
                }
                spin_unlock(&memcg->event_list_lock);
        }

        return 0;
}

static void memcg_event_ptable_queue_proc(struct file *file,
                wait_queue_head_t *wqh, poll_table *pt)
{
        struct mem_cgroup_event *event =
                container_of(pt, struct mem_cgroup_event, pt);

        event->wqh = wqh;
        add_wait_queue(wqh, &event->wait);
}

/*
 * DO NOT USE IN NEW FILES.
 *
 * Parse input and register new cgroup event handler.
 *
 * Input must be in format '<event_fd> <control_fd> <args>'.
 * Interpretation of args is defined by control file implementation.
 */
static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
                                         char *buf, size_t nbytes, loff_t off)
{
        struct cgroup_subsys_state *css = of_css(of);
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);
        struct mem_cgroup_event *event;
        struct cgroup_subsys_state *cfile_css;
        unsigned int efd, cfd;
        struct dentry *cdentry;
        const char *name;
        char *endp;
        int ret;

        if (IS_ENABLED(CONFIG_PREEMPT_RT))
                return -EOPNOTSUPP;

        buf = strstrip(buf);

        efd = simple_strtoul(buf, &endp, 10);
        if (*endp != ' ')
                return -EINVAL;
        buf = endp + 1;

        cfd = simple_strtoul(buf, &endp, 10);
        if (*endp == '\0')
                buf = endp;
        else if (*endp == ' ')
                buf = endp + 1;
        else
                return -EINVAL;

        CLASS(fd, efile)(efd);
        if (fd_empty(efile))
                return -EBADF;

        CLASS(fd, cfile)(cfd);

        event = kzalloc_obj(*event, GFP_KERNEL_ACCOUNT);
        if (!event)
                return -ENOMEM;

        event->memcg = memcg;
        INIT_LIST_HEAD(&event->list);
        init_poll_funcptr(&event->pt, memcg_event_ptable_queue_proc);
        init_waitqueue_func_entry(&event->wait, memcg_event_wake);
        INIT_WORK(&event->remove, memcg_event_remove);

        event->eventfd = eventfd_ctx_fileget(fd_file(efile));
        if (IS_ERR(event->eventfd)) {
                ret = PTR_ERR(event->eventfd);
                goto out_kfree;
        }

        if (fd_empty(cfile)) {
                ret = -EBADF;
                goto out_put_eventfd;
        }

        /* the process need read permission on control file */
        /* AV: shouldn't we check that it's been opened for read instead? */
        ret = file_permission(fd_file(cfile), MAY_READ);
        if (ret < 0)
                goto out_put_eventfd;

        /*
         * The control file must be a regular cgroup1 file. As a regular cgroup
         * file can't be renamed, it's safe to access its name afterwards.
         */
        cdentry = fd_file(cfile)->f_path.dentry;
        if (cdentry->d_sb->s_type != &cgroup_fs_type || !d_is_reg(cdentry)) {
                ret = -EINVAL;
                goto out_put_eventfd;
        }

        /*
         * Determine the event callbacks and set them in @event.  This used
         * to be done via struct cftype but cgroup core no longer knows
         * about these events.  The following is crude but the whole thing
         * is for compatibility anyway.
         *
         * DO NOT ADD NEW FILES.
         */
        name = cdentry->d_name.name;

        if (!strcmp(name, "memory.usage_in_bytes")) {
                event->register_event = mem_cgroup_usage_register_event;
                event->unregister_event = mem_cgroup_usage_unregister_event;
        } else if (!strcmp(name, "memory.oom_control")) {
                pr_warn_once("oom_control is deprecated and will be removed. "
                             "Please report your usecase to linux-mm-@kvack.org"
                             " if you depend on this functionality.\n");
                event->register_event = mem_cgroup_oom_register_event;
                event->unregister_event = mem_cgroup_oom_unregister_event;
        } else if (!strcmp(name, "memory.pressure_level")) {
                pr_warn_once("pressure_level is deprecated and will be removed. "
                             "Please report your usecase to linux-mm-@kvack.org "
                             "if you depend on this functionality.\n");
                event->register_event = vmpressure_register_event;
                event->unregister_event = vmpressure_unregister_event;
        } else if (!strcmp(name, "memory.memsw.usage_in_bytes")) {
                event->register_event = memsw_cgroup_usage_register_event;
                event->unregister_event = memsw_cgroup_usage_unregister_event;
        } else {
                ret = -EINVAL;
                goto out_put_eventfd;
        }

        /*
         * Verify @cfile should belong to @css.  Also, remaining events are
         * automatically removed on cgroup destruction but the removal is
         * asynchronous, so take an extra ref on @css.
         */
        cfile_css = css_tryget_online_from_dir(cdentry->d_parent,
                                               &memory_cgrp_subsys);
        ret = -EINVAL;
        if (IS_ERR(cfile_css))
                goto out_put_eventfd;
        if (cfile_css != css)
                goto out_put_css;

        ret = event->register_event(memcg, event->eventfd, buf);
        if (ret)
                goto out_put_css;

        vfs_poll(fd_file(efile), &event->pt);

        spin_lock_irq(&memcg->event_list_lock);
        list_add(&event->list, &memcg->event_list);
        spin_unlock_irq(&memcg->event_list_lock);
        return nbytes;

out_put_css:
        css_put(cfile_css);
out_put_eventfd:
        eventfd_ctx_put(event->eventfd);
out_kfree:
        kfree(event);
        return ret;
}

void memcg1_memcg_init(struct mem_cgroup *memcg)
{
        INIT_LIST_HEAD(&memcg->oom_notify);
        mutex_init(&memcg->thresholds_lock);
        INIT_LIST_HEAD(&memcg->event_list);
        spin_lock_init(&memcg->event_list_lock);
}

void memcg1_css_offline(struct mem_cgroup *memcg)
{
        struct mem_cgroup_event *event, *tmp;

        /*
         * Unregister events and notify userspace.
         * Notify userspace about cgroup removing only after rmdir of cgroup
         * directory to avoid race between userspace and kernelspace.
         */
        spin_lock_irq(&memcg->event_list_lock);
        list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
                list_del_init(&event->list);
                schedule_work(&event->remove);
        }
        spin_unlock_irq(&memcg->event_list_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;
                }
                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 int 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);
}

void memcg1_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);
}

/**
 * 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);

        schedule();
        mem_cgroup_unmark_under_oom(memcg);
        finish_wait(&memcg_oom_waitq, &owait.wait);

        if (locked)
                mem_cgroup_oom_unlock(memcg);
cleanup:
        current->memcg_in_oom = NULL;
        css_put(&memcg->css);
        return true;
}


bool memcg1_oom_prepare(struct mem_cgroup *memcg, bool *locked)
{
        /*
         * 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 (READ_ONCE(memcg->oom_kill_disable)) {
                if (current->in_user_fault) {
                        css_get(&memcg->css);
                        current->memcg_in_oom = memcg;
                }
                return false;
        }

        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);

        return true;
}

void memcg1_oom_finish(struct mem_cgroup *memcg, bool locked)
{
        if (locked)
                mem_cgroup_oom_unlock(memcg);
}

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 ? 0 : MEMCG_RECLAIM_MAY_SWAP, NULL)) {
                        ret = -EBUSY;
                        break;
                }
        } while (true);

        if (!ret && enlarge)
                memcg1_oom_recover(memcg);

        return ret;
}

/*
 * 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)) {
                if (signal_pending(current))
                        return -EINTR;

                if (!try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL,
                                                  MEMCG_RECLAIM_MAY_SWAP, NULL))
                        nr_retries--;
        }

        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 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)READ_ONCE(memcg->soft_limit) * PAGE_SIZE;
        default:
                BUG();
        }
}

/*
 * This function doesn't do anything useful. Its only job is to provide a read
 * handler for a file so that cgroup_file_mode() will add read permissions.
 */
static int mem_cgroup_dummy_seq_show(__always_unused struct seq_file *m,
                                     __always_unused void *v)
{
        return -EINVAL;
}

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. "
                                     "Writing any value to this file has no effect. "
                                     "Please report your usecase to linux-mm@kvack.org if you "
                                     "depend on this functionality.\n");
                        ret = 0;
                        break;
                case _TCP:
                        pr_warn_once("kmem.tcp.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_tcp_max(memcg, nr_pages);
                        break;
                }
                break;
        case RES_SOFT_LIMIT:
                if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
                        ret = -EOPNOTSUPP;
                } else {
                        pr_warn_once("soft_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");
                        WRITE_ONCE(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;
}

#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 int)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);

        mem_cgroup_flush_stats(memcg);

        for (stat = stats; stat < ARRAY_END(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 < ARRAY_END(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,
        WORKINGSET_REFAULT_ANON,
        WORKINGSET_REFAULT_FILE,
#ifdef CONFIG_SWAP
        MEMCG_SWAP,
        NR_SWAPCACHE,
#endif
};

static const char *const memcg1_stat_names[] = {
        "cache",
        "rss",
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        "rss_huge",
#endif
        "shmem",
        "mapped_file",
        "dirty",
        "writeback",
        "workingset_refault_anon",
        "workingset_refault_file",
#ifdef CONFIG_SWAP
        "swap",
        "swapcached",
#endif
};

/* Universal VM events cgroup1 shows, original sort order */
static const unsigned int memcg1_events[] = {
        PGPGIN,
        PGPGOUT,
        PGFAULT,
        PGMAJFAULT,
};

void memcg1_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
{
        unsigned long memory, memsw;
        struct mem_cgroup *mi;
        unsigned int i;

        BUILD_BUG_ON(ARRAY_SIZE(memcg1_stat_names) != ARRAY_SIZE(memcg1_stats));

        mem_cgroup_flush_stats(memcg);

        for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) {
                unsigned long nr;

                nr = memcg_page_state_local_output(memcg, memcg1_stats[i]);
                seq_buf_printf(s, "%s %lu\n", memcg1_stat_names[i], nr);
        }

        for (i = 0; i < ARRAY_SIZE(memcg1_events); i++)
                seq_buf_printf(s, "%s %lu\n", vm_event_name(memcg1_events[i]),
                               memcg_events_local(memcg, memcg1_events[i]));

        for (i = 0; i < NR_LRU_LISTS; i++)
                seq_buf_printf(s, "%s %lu\n", lru_list_name(i),
                               memcg_page_state_local(memcg, NR_LRU_BASE + i) *
                               PAGE_SIZE);

        /* Hierarchical information */
        memory = memsw = PAGE_COUNTER_MAX;
        for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) {
                memory = min(memory, READ_ONCE(mi->memory.max));
                memsw = min(memsw, READ_ONCE(mi->memsw.max));
        }
        seq_buf_printf(s, "hierarchical_memory_limit %llu\n",
                       (u64)memory * PAGE_SIZE);
        seq_buf_printf(s, "hierarchical_memsw_limit %llu\n",
                       (u64)memsw * PAGE_SIZE);

        for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) {
                unsigned long nr;

                nr = memcg_page_state_output(memcg, memcg1_stats[i]);
                seq_buf_printf(s, "total_%s %llu\n", memcg1_stat_names[i],
                               (u64)nr);
        }

        for (i = 0; i < ARRAY_SIZE(memcg1_events); i++)
                seq_buf_printf(s, "total_%s %llu\n",
                               vm_event_name(memcg1_events[i]),
                               (u64)memcg_events(memcg, memcg1_events[i]));

        for (i = 0; i < NR_LRU_LISTS; i++)
                seq_buf_printf(s, "total_%s %llu\n", lru_list_name(i),
                               (u64)memcg_page_state(memcg, NR_LRU_BASE + i) *
                               PAGE_SIZE);

#ifdef CONFIG_DEBUG_VM
        {
                pg_data_t *pgdat;
                struct mem_cgroup_per_node *mz;
                unsigned long anon_cost = 0;
                unsigned long file_cost = 0;

                for_each_online_pgdat(pgdat) {
                        mz = memcg->nodeinfo[pgdat->node_id];

                        anon_cost += mz->lruvec.anon_cost;
                        file_cost += mz->lruvec.file_cost;
                }
                seq_buf_printf(s, "anon_cost %lu\n", anon_cost);
                seq_buf_printf(s, "file_cost %lu\n", file_cost);
        }
#endif
}

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

        return mem_cgroup_swappiness(memcg);
}

static int mem_cgroup_swappiness_write(struct cgroup_subsys_state *css,
                                       struct cftype *cft, u64 val)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);

        if (val > MAX_SWAPPINESS)
                return -EINVAL;

        if (!mem_cgroup_is_root(memcg)) {
                pr_info_once("Per memcg swappiness does not exist in cgroup v2. "
                             "See memory.reclaim or memory.swap.max there\n ");
                WRITE_ONCE(memcg->swappiness, val);
        } else
                WRITE_ONCE(vm_swappiness, val);

        return 0;
}

static int mem_cgroup_oom_control_read(struct seq_file *sf, void *v)
{
        struct mem_cgroup *memcg = mem_cgroup_from_seq(sf);

        seq_printf(sf, "oom_kill_disable %d\n", READ_ONCE(memcg->oom_kill_disable));
        seq_printf(sf, "under_oom %d\n", (bool)memcg->under_oom);
        seq_printf(sf, "oom_kill %lu\n",
                   atomic_long_read(&memcg->memory_events[MEMCG_OOM_KILL]));
        return 0;
}

static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
        struct cftype *cft, u64 val)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);

        pr_warn_once("oom_control is deprecated and will be removed. "
                     "Please report your usecase to linux-mm-@kvack.org if you "
                     "depend on this functionality.\n");

        /* cannot set to root cgroup and only 0 and 1 are allowed */
        if (mem_cgroup_is_root(memcg) || !((val == 0) || (val == 1)))
                return -EINVAL;

        WRITE_ONCE(memcg->oom_kill_disable, val);
        if (!val)
                memcg1_oom_recover(memcg);

        return 0;
}

#ifdef CONFIG_SLUB_DEBUG
static int mem_cgroup_slab_show(struct seq_file *m, void *p)
{
        /*
         * Deprecated.
         * Please, take a look at tools/cgroup/memcg_slabinfo.py .
         */
        return 0;
}
#endif

struct cftype mem_cgroup_legacy_files[] = {
        {
                .name = "usage_in_bytes",
                .private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "max_usage_in_bytes",
                .private = MEMFILE_PRIVATE(_MEM, RES_MAX_USAGE),
                .write = mem_cgroup_reset,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "limit_in_bytes",
                .private = MEMFILE_PRIVATE(_MEM, RES_LIMIT),
                .write = mem_cgroup_write,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "soft_limit_in_bytes",
                .private = MEMFILE_PRIVATE(_MEM, RES_SOFT_LIMIT),
                .write = mem_cgroup_write,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "failcnt",
                .private = MEMFILE_PRIVATE(_MEM, RES_FAILCNT),
                .write = mem_cgroup_reset,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "stat",
                .seq_show = memory_stat_show,
        },
        {
                .name = "force_empty",
                .write = mem_cgroup_force_empty_write,
        },
        {
                .name = "use_hierarchy",
                .write_u64 = mem_cgroup_hierarchy_write,
                .read_u64 = mem_cgroup_hierarchy_read,
        },
        {
                .name = "cgroup.event_control",         /* XXX: for compat */
                .write = memcg_write_event_control,
                .flags = CFTYPE_NO_PREFIX,
        },
        {
                .name = "swappiness",
                .read_u64 = mem_cgroup_swappiness_read,
                .write_u64 = mem_cgroup_swappiness_write,
        },
        {
                .name = "move_charge_at_immigrate",
                .read_u64 = mem_cgroup_move_charge_read,
                .write_u64 = mem_cgroup_move_charge_write,
        },
        {
                .name = "oom_control",
                .seq_show = mem_cgroup_oom_control_read,
                .write_u64 = mem_cgroup_oom_control_write,
        },
        {
                .name = "pressure_level",
                .seq_show = mem_cgroup_dummy_seq_show,
        },
#ifdef CONFIG_NUMA
        {
                .name = "numa_stat",
                .seq_show = memcg_numa_stat_show,
        },
#endif
        {
                .name = "kmem.limit_in_bytes",
                .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
                .write = mem_cgroup_write,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "kmem.usage_in_bytes",
                .private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "kmem.failcnt",
                .private = MEMFILE_PRIVATE(_KMEM, RES_FAILCNT),
                .write = mem_cgroup_reset,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "kmem.max_usage_in_bytes",
                .private = MEMFILE_PRIVATE(_KMEM, RES_MAX_USAGE),
                .write = mem_cgroup_reset,
                .read_u64 = mem_cgroup_read_u64,
        },
#ifdef CONFIG_SLUB_DEBUG
        {
                .name = "kmem.slabinfo",
                .seq_show = mem_cgroup_slab_show,
        },
#endif
        {
                .name = "kmem.tcp.limit_in_bytes",
                .private = MEMFILE_PRIVATE(_TCP, RES_LIMIT),
                .write = mem_cgroup_write,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "kmem.tcp.usage_in_bytes",
                .private = MEMFILE_PRIVATE(_TCP, RES_USAGE),
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "kmem.tcp.failcnt",
                .private = MEMFILE_PRIVATE(_TCP, RES_FAILCNT),
                .write = mem_cgroup_reset,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "kmem.tcp.max_usage_in_bytes",
                .private = MEMFILE_PRIVATE(_TCP, RES_MAX_USAGE),
                .write = mem_cgroup_reset,
                .read_u64 = mem_cgroup_read_u64,
        },
        { },    /* terminate */
};

struct cftype memsw_files[] = {
        {
                .name = "memsw.usage_in_bytes",
                .private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "memsw.max_usage_in_bytes",
                .private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
                .write = mem_cgroup_reset,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "memsw.limit_in_bytes",
                .private = MEMFILE_PRIVATE(_MEMSWAP, RES_LIMIT),
                .write = mem_cgroup_write,
                .read_u64 = mem_cgroup_read_u64,
        },
        {
                .name = "memsw.failcnt",
                .private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
                .write = mem_cgroup_reset,
                .read_u64 = mem_cgroup_read_u64,
        },
        { },    /* terminate */
};

void memcg1_account_kmem(struct mem_cgroup *memcg, int nr_pages)
{
        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
                if (nr_pages > 0)
                        page_counter_charge(&memcg->kmem, nr_pages);
                else
                        page_counter_uncharge(&memcg->kmem, -nr_pages);
        }
}

bool memcg1_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages,
                         gfp_t gfp_mask)
{
        struct page_counter *fail;

        if (page_counter_try_charge(&memcg->tcpmem, nr_pages, &fail)) {
                memcg->tcpmem_pressure = 0;
                return true;
        }
        memcg->tcpmem_pressure = 1;
        if (gfp_mask & __GFP_NOFAIL) {
                page_counter_charge(&memcg->tcpmem, nr_pages);
                return true;
        }
        return false;
}

bool memcg1_alloc_events(struct mem_cgroup *memcg)
{
        memcg->events_percpu = alloc_percpu_gfp(struct memcg1_events_percpu,
                                                GFP_KERNEL_ACCOUNT);
        return !!memcg->events_percpu;
}

void memcg1_free_events(struct mem_cgroup *memcg)
{
        free_percpu(memcg->events_percpu);
}

static int __init memcg1_init(void)
{
        int node;

        for_each_node(node) {
                struct mem_cgroup_tree_per_node *rtpn;

                rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, node);

                rtpn->rb_root = RB_ROOT;
                rtpn->rb_rightmost = NULL;
                spin_lock_init(&rtpn->lock);
                soft_limit_tree.rb_tree_per_node[node] = rtpn;
        }

        return 0;
}
subsys_initcall(memcg1_init);