Merge tag 'trace-printf-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...

[drm/drm-misc.git] / mm / memcontrol.c

// 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/cgroup-defs.h>
#include <linux/page_counter.h>
#include <linux/memcontrol.h>
#include <linux/cgroup.h>
#include <linux/sched/mm.h>
#include <linux/shmem_fs.h>
#include <linux/hugetlb.h>
#include <linux/pagemap.h>
#include <linux/pagevec.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/list.h>
#include <linux/mutex.h>
#include <linux/rbtree.h>
#include <linux/slab.h>
#include <linux/swapops.h>
#include <linux/spinlock.h>
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/parser.h>
#include <linux/vmpressure.h>
#include <linux/memremap.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/resume_user_mode.h>
#include <linux/psi.h>
#include <linux/seq_buf.h>
#include <linux/sched/isolation.h>
#include <linux/kmemleak.h>
#include "internal.h"
#include <net/sock.h>
#include <net/ip.h>
#include "slab.h"
#include "memcontrol-v1.h"

#include <linux/uaccess.h>

#define CREATE_TRACE_POINTS
#include <trace/events/memcg.h>
#undef CREATE_TRACE_POINTS

#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? */
static bool cgroup_memory_nokmem __ro_after_init;

/* BPF memory accounting disabled? */
static bool cgroup_memory_nobpf __ro_after_init;

#ifdef CONFIG_CGROUP_WRITEBACK
static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq);
#endif

static inline bool task_is_dying(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 mem_cgroup *vmpressure_to_memcg(struct vmpressure *vmpr)
{
        return container_of(vmpr, struct mem_cgroup, vmpressure);
}

#define SEQ_BUF_SIZE SZ_4K
#define CURRENT_OBJCG_UPDATE_BIT 0
#define CURRENT_OBJCG_UPDATE_FLAG (1UL << CURRENT_OBJCG_UPDATE_BIT)

static DEFINE_SPINLOCK(objcg_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(&objcg_lock, flags);
        list_del(&objcg->list);
        spin_unlock_irqrestore(&objcg_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(&objcg_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(&objcg_lock);

        percpu_ref_kill(&objcg->refcnt);
}

/*
 * A lot of the calls to the cache allocation functions are expected to be
 * inlined by the compiler. Since the calls to memcg_slab_post_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_online_key);
EXPORT_SYMBOL(memcg_kmem_online_key);

DEFINE_STATIC_KEY_FALSE(memcg_bpf_enabled_key);
EXPORT_SYMBOL(memcg_bpf_enabled_key);

/**
 * mem_cgroup_css_from_folio - css of the memcg associated with a folio
 * @folio: folio of interest
 *
 * If memcg is bound to the default hierarchy, css of the memcg associated
 * with @folio is returned.  The returned css remains associated with @folio
 * 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_folio(struct folio *folio)
{
        struct mem_cgroup *memcg = folio_memcg(folio);

        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();
        /* page_folio() is racy here, but the entire function is racy anyway */
        memcg = folio_memcg_check(page_folio(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;
}

/* Subset of node_stat_item for memcg stats */
static const unsigned int memcg_node_stat_items[] = {
        NR_INACTIVE_ANON,
        NR_ACTIVE_ANON,
        NR_INACTIVE_FILE,
        NR_ACTIVE_FILE,
        NR_UNEVICTABLE,
        NR_SLAB_RECLAIMABLE_B,
        NR_SLAB_UNRECLAIMABLE_B,
        WORKINGSET_REFAULT_ANON,
        WORKINGSET_REFAULT_FILE,
        WORKINGSET_ACTIVATE_ANON,
        WORKINGSET_ACTIVATE_FILE,
        WORKINGSET_RESTORE_ANON,
        WORKINGSET_RESTORE_FILE,
        WORKINGSET_NODERECLAIM,
        NR_ANON_MAPPED,
        NR_FILE_MAPPED,
        NR_FILE_PAGES,
        NR_FILE_DIRTY,
        NR_WRITEBACK,
        NR_SHMEM,
        NR_SHMEM_THPS,
        NR_FILE_THPS,
        NR_ANON_THPS,
        NR_KERNEL_STACK_KB,
        NR_PAGETABLE,
        NR_SECONDARY_PAGETABLE,
#ifdef CONFIG_SWAP
        NR_SWAPCACHE,
#endif
#ifdef CONFIG_NUMA_BALANCING
        PGPROMOTE_SUCCESS,
#endif
        PGDEMOTE_KSWAPD,
        PGDEMOTE_DIRECT,
        PGDEMOTE_KHUGEPAGED,
#ifdef CONFIG_HUGETLB_PAGE
        NR_HUGETLB,
#endif
};

static const unsigned int memcg_stat_items[] = {
        MEMCG_SWAP,
        MEMCG_SOCK,
        MEMCG_PERCPU_B,
        MEMCG_VMALLOC,
        MEMCG_KMEM,
        MEMCG_ZSWAP_B,
        MEMCG_ZSWAPPED,
};

#define NR_MEMCG_NODE_STAT_ITEMS ARRAY_SIZE(memcg_node_stat_items)
#define MEMCG_VMSTAT_SIZE (NR_MEMCG_NODE_STAT_ITEMS + \
                           ARRAY_SIZE(memcg_stat_items))
#define BAD_STAT_IDX(index) ((u32)(index) >= U8_MAX)
static u8 mem_cgroup_stats_index[MEMCG_NR_STAT] __read_mostly;

static void init_memcg_stats(void)
{
        u8 i, j = 0;

        BUILD_BUG_ON(MEMCG_NR_STAT >= U8_MAX);

        memset(mem_cgroup_stats_index, U8_MAX, sizeof(mem_cgroup_stats_index));

        for (i = 0; i < NR_MEMCG_NODE_STAT_ITEMS; ++i, ++j)
                mem_cgroup_stats_index[memcg_node_stat_items[i]] = j;

        for (i = 0; i < ARRAY_SIZE(memcg_stat_items); ++i, ++j)
                mem_cgroup_stats_index[memcg_stat_items[i]] = j;
}

static inline int memcg_stats_index(int idx)
{
        return mem_cgroup_stats_index[idx];
}

struct lruvec_stats_percpu {
        /* Local (CPU and cgroup) state */
        long state[NR_MEMCG_NODE_STAT_ITEMS];

        /* Delta calculation for lockless upward propagation */
        long state_prev[NR_MEMCG_NODE_STAT_ITEMS];
};

struct lruvec_stats {
        /* Aggregated (CPU and subtree) state */
        long state[NR_MEMCG_NODE_STAT_ITEMS];

        /* Non-hierarchical (CPU aggregated) state */
        long state_local[NR_MEMCG_NODE_STAT_ITEMS];

        /* Pending child counts during tree propagation */
        long state_pending[NR_MEMCG_NODE_STAT_ITEMS];
};

unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx)
{
        struct mem_cgroup_per_node *pn;
        long x;
        int i;

        if (mem_cgroup_disabled())
                return node_page_state(lruvec_pgdat(lruvec), idx);

        i = memcg_stats_index(idx);
        if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
                return 0;

        pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
        x = READ_ONCE(pn->lruvec_stats->state[i]);
#ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
#endif
        return x;
}

unsigned long lruvec_page_state_local(struct lruvec *lruvec,
                                      enum node_stat_item idx)
{
        struct mem_cgroup_per_node *pn;
        long x;
        int i;

        if (mem_cgroup_disabled())
                return node_page_state(lruvec_pgdat(lruvec), idx);

        i = memcg_stats_index(idx);
        if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
                return 0;

        pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
        x = READ_ONCE(pn->lruvec_stats->state_local[i]);
#ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
#endif
        return x;
}

/* Subset of vm_event_item to report for memcg event stats */
static const unsigned int memcg_vm_event_stat[] = {
#ifdef CONFIG_MEMCG_V1
        PGPGIN,
        PGPGOUT,
#endif
        PSWPIN,
        PSWPOUT,
        PGSCAN_KSWAPD,
        PGSCAN_DIRECT,
        PGSCAN_KHUGEPAGED,
        PGSTEAL_KSWAPD,
        PGSTEAL_DIRECT,
        PGSTEAL_KHUGEPAGED,
        PGFAULT,
        PGMAJFAULT,
        PGREFILL,
        PGACTIVATE,
        PGDEACTIVATE,
        PGLAZYFREE,
        PGLAZYFREED,
#ifdef CONFIG_SWAP
        SWPIN_ZERO,
        SWPOUT_ZERO,
#endif
#ifdef CONFIG_ZSWAP
        ZSWPIN,
        ZSWPOUT,
        ZSWPWB,
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        THP_FAULT_ALLOC,
        THP_COLLAPSE_ALLOC,
        THP_SWPOUT,
        THP_SWPOUT_FALLBACK,
#endif
#ifdef CONFIG_NUMA_BALANCING
        NUMA_PAGE_MIGRATE,
        NUMA_PTE_UPDATES,
        NUMA_HINT_FAULTS,
#endif
};

#define NR_MEMCG_EVENTS ARRAY_SIZE(memcg_vm_event_stat)
static u8 mem_cgroup_events_index[NR_VM_EVENT_ITEMS] __read_mostly;

static void init_memcg_events(void)
{
        u8 i;

        BUILD_BUG_ON(NR_VM_EVENT_ITEMS >= U8_MAX);

        memset(mem_cgroup_events_index, U8_MAX,
               sizeof(mem_cgroup_events_index));

        for (i = 0; i < NR_MEMCG_EVENTS; ++i)
                mem_cgroup_events_index[memcg_vm_event_stat[i]] = i;
}

static inline int memcg_events_index(enum vm_event_item idx)
{
        return mem_cgroup_events_index[idx];
}

struct memcg_vmstats_percpu {
        /* Stats updates since the last flush */
        unsigned int                    stats_updates;

        /* Cached pointers for fast iteration in memcg_rstat_updated() */
        struct memcg_vmstats_percpu     *parent;
        struct memcg_vmstats            *vmstats;

        /* The above should fit a single cacheline for memcg_rstat_updated() */

        /* Local (CPU and cgroup) page state & events */
        long                    state[MEMCG_VMSTAT_SIZE];
        unsigned long           events[NR_MEMCG_EVENTS];

        /* Delta calculation for lockless upward propagation */
        long                    state_prev[MEMCG_VMSTAT_SIZE];
        unsigned long           events_prev[NR_MEMCG_EVENTS];
} ____cacheline_aligned;

struct memcg_vmstats {
        /* Aggregated (CPU and subtree) page state & events */
        long                    state[MEMCG_VMSTAT_SIZE];
        unsigned long           events[NR_MEMCG_EVENTS];

        /* Non-hierarchical (CPU aggregated) page state & events */
        long                    state_local[MEMCG_VMSTAT_SIZE];
        unsigned long           events_local[NR_MEMCG_EVENTS];

        /* Pending child counts during tree propagation */
        long                    state_pending[MEMCG_VMSTAT_SIZE];
        unsigned long           events_pending[NR_MEMCG_EVENTS];

        /* Stats updates since the last flush */
        atomic64_t              stats_updates;
};

/*
 * memcg and lruvec stats flushing
 *
 * Many codepaths leading to stats update or read are performance sensitive and
 * adding stats flushing in such codepaths is not desirable. So, to optimize the
 * flushing the kernel does:
 *
 * 1) Periodically and asynchronously flush the stats every 2 seconds to not let
 *    rstat update tree grow unbounded.
 *
 * 2) Flush the stats synchronously on reader side only when there are more than
 *    (MEMCG_CHARGE_BATCH * nr_cpus) update events. Though this optimization
 *    will let stats be out of sync by atmost (MEMCG_CHARGE_BATCH * nr_cpus) but
 *    only for 2 seconds due to (1).
 */
static void flush_memcg_stats_dwork(struct work_struct *w);
static DECLARE_DEFERRABLE_WORK(stats_flush_dwork, flush_memcg_stats_dwork);
static u64 flush_last_time;

#define FLUSH_TIME (2UL*HZ)

/*
 * Accessors to ensure that preemption is disabled on PREEMPT_RT because it can
 * not rely on this as part of an acquired spinlock_t lock. These functions are
 * never used in hardirq context on PREEMPT_RT and therefore disabling preemtion
 * is sufficient.
 */
static void memcg_stats_lock(void)
{
        preempt_disable_nested();
        VM_WARN_ON_IRQS_ENABLED();
}

static void __memcg_stats_lock(void)
{
        preempt_disable_nested();
}

static void memcg_stats_unlock(void)
{
        preempt_enable_nested();
}


static bool memcg_vmstats_needs_flush(struct memcg_vmstats *vmstats)
{
        return atomic64_read(&vmstats->stats_updates) >
                MEMCG_CHARGE_BATCH * num_online_cpus();
}

static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val)
{
        struct memcg_vmstats_percpu *statc;
        int cpu = smp_processor_id();
        unsigned int stats_updates;

        if (!val)
                return;

        cgroup_rstat_updated(memcg->css.cgroup, cpu);
        statc = this_cpu_ptr(memcg->vmstats_percpu);
        for (; statc; statc = statc->parent) {
                stats_updates = READ_ONCE(statc->stats_updates) + abs(val);
                WRITE_ONCE(statc->stats_updates, stats_updates);
                if (stats_updates < MEMCG_CHARGE_BATCH)
                        continue;

                /*
                 * If @memcg is already flush-able, increasing stats_updates is
                 * redundant. Avoid the overhead of the atomic update.
                 */
                if (!memcg_vmstats_needs_flush(statc->vmstats))
                        atomic64_add(stats_updates,
                                     &statc->vmstats->stats_updates);
                WRITE_ONCE(statc->stats_updates, 0);
        }
}

static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force)
{
        bool needs_flush = memcg_vmstats_needs_flush(memcg->vmstats);

        trace_memcg_flush_stats(memcg, atomic64_read(&memcg->vmstats->stats_updates),
                force, needs_flush);

        if (!force && !needs_flush)
                return;

        if (mem_cgroup_is_root(memcg))
                WRITE_ONCE(flush_last_time, jiffies_64);

        cgroup_rstat_flush(memcg->css.cgroup);
}

/*
 * mem_cgroup_flush_stats - flush the stats of a memory cgroup subtree
 * @memcg: root of the subtree to flush
 *
 * Flushing is serialized by the underlying global rstat lock. There is also a
 * minimum amount of work to be done even if there are no stat updates to flush.
 * Hence, we only flush the stats if the updates delta exceeds a threshold. This
 * avoids unnecessary work and contention on the underlying lock.
 */
void mem_cgroup_flush_stats(struct mem_cgroup *memcg)
{
        if (mem_cgroup_disabled())
                return;

        if (!memcg)
                memcg = root_mem_cgroup;

        __mem_cgroup_flush_stats(memcg, false);
}

void mem_cgroup_flush_stats_ratelimited(struct mem_cgroup *memcg)
{
        /* Only flush if the periodic flusher is one full cycle late */
        if (time_after64(jiffies_64, READ_ONCE(flush_last_time) + 2*FLUSH_TIME))
                mem_cgroup_flush_stats(memcg);
}

static void flush_memcg_stats_dwork(struct work_struct *w)
{
        /*
         * Deliberately ignore memcg_vmstats_needs_flush() here so that flushing
         * in latency-sensitive paths is as cheap as possible.
         */
        __mem_cgroup_flush_stats(root_mem_cgroup, true);
        queue_delayed_work(system_unbound_wq, &stats_flush_dwork, FLUSH_TIME);
}

unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
{
        long x;
        int i = memcg_stats_index(idx);

        if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
                return 0;

        x = READ_ONCE(memcg->vmstats->state[i]);
#ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
#endif
        return x;
}

static int memcg_page_state_unit(int item);

/*
 * Normalize the value passed into memcg_rstat_updated() to be in pages. Round
 * up non-zero sub-page updates to 1 page as zero page updates are ignored.
 */
static int memcg_state_val_in_pages(int idx, int val)
{
        int unit = memcg_page_state_unit(idx);

        if (!val || unit == PAGE_SIZE)
                return val;
        else
                return max(val * unit / PAGE_SIZE, 1UL);
}

/**
 * __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, enum memcg_stat_item idx,
                       int val)
{
        int i = memcg_stats_index(idx);

        if (mem_cgroup_disabled())
                return;

        if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
                return;

        __this_cpu_add(memcg->vmstats_percpu->state[i], val);
        val = memcg_state_val_in_pages(idx, val);
        memcg_rstat_updated(memcg, val);
        trace_mod_memcg_state(memcg, idx, val);
}

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

        if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
                return 0;

        x = READ_ONCE(memcg->vmstats->state_local[i]);
#ifdef CONFIG_SMP
        if (x < 0)
                x = 0;
#endif
        return x;
}

static 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;
        int i = memcg_stats_index(idx);

        if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
                return;

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

        /*
         * The caller from rmap relies on disabled preemption because they never
         * update their counter from in-interrupt context. For these two
         * counters we check that the update is never performed from an
         * interrupt context while other caller need to have disabled interrupt.
         */
        __memcg_stats_lock();
        if (IS_ENABLED(CONFIG_DEBUG_VM)) {
                switch (idx) {
                case NR_ANON_MAPPED:
                case NR_FILE_MAPPED:
                case NR_ANON_THPS:
                        WARN_ON_ONCE(!in_task());
                        break;
                default:
                        VM_WARN_ON_IRQS_ENABLED();
                }
        }

        /* Update memcg */
        __this_cpu_add(memcg->vmstats_percpu->state[i], val);

        /* Update lruvec */
        __this_cpu_add(pn->lruvec_stats_percpu->state[i], val);

        val = memcg_state_val_in_pages(idx, val);
        memcg_rstat_updated(memcg, val);
        trace_mod_memcg_lruvec_state(memcg, idx, val);
        memcg_stats_unlock();
}

/**
 * __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 __lruvec_stat_mod_folio(struct folio *folio, enum node_stat_item idx,
                             int val)
{
        struct mem_cgroup *memcg;
        pg_data_t *pgdat = folio_pgdat(folio);
        struct lruvec *lruvec;

        rcu_read_lock();
        memcg = folio_memcg(folio);
        /* 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(__lruvec_stat_mod_folio);

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_slab_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();
}

/**
 * __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)
{
        int i = memcg_events_index(idx);

        if (mem_cgroup_disabled())
                return;

        if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx))
                return;

        memcg_stats_lock();
        __this_cpu_add(memcg->vmstats_percpu->events[i], count);
        memcg_rstat_updated(memcg, count);
        trace_count_memcg_events(memcg, idx, count);
        memcg_stats_unlock();
}

unsigned long memcg_events(struct mem_cgroup *memcg, int event)
{
        int i = memcg_events_index(event);

        if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, event))
                return 0;

        return READ_ONCE(memcg->vmstats->events[i]);
}

unsigned long memcg_events_local(struct mem_cgroup *memcg, int event)
{
        int i = memcg_events_index(event);

        if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, event))
                return 0;

        return READ_ONCE(memcg->vmstats->events_local[i]);
}

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_task())
                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);

/**
 * get_mem_cgroup_from_current - Obtain a reference on current task's memcg.
 */
struct mem_cgroup *get_mem_cgroup_from_current(void)
{
        struct mem_cgroup *memcg;

        if (mem_cgroup_disabled())
                return NULL;

again:
        rcu_read_lock();
        memcg = mem_cgroup_from_task(current);
        if (!css_tryget(&memcg->css)) {
                rcu_read_unlock();
                goto again;
        }
        rcu_read_unlock();
        return memcg;
}

/**
 * get_mem_cgroup_from_folio - Obtain a reference on a given folio's memcg.
 * @folio: folio from which memcg should be extracted.
 */
struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio)
{
        struct mem_cgroup *memcg = folio_memcg(folio);

        if (mem_cgroup_disabled())
                return NULL;

        rcu_read_lock();
        if (!memcg || WARN_ON_ONCE(!css_tryget(&memcg->css)))
                memcg = root_mem_cgroup;
        rcu_read_unlock();
        return memcg;
}

/**
 * mem_cgroup_iter - iterate over memory cgroup hierarchy
 * @root: hierarchy root
 * @prev: previously returned memcg, NULL on first invocation
 * @reclaim: cookie for shared reclaim walks, NULL for full walks
 *
 * Returns references to children of the hierarchy below @root, or
 * @root itself, or %NULL after a full round-trip.
 *
 * Caller must pass the return value in @prev on subsequent
 * invocations for reference counting, or use mem_cgroup_iter_break()
 * to cancel a hierarchy walk before the round-trip is complete.
 *
 * Reclaimers can specify a 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;
        struct mem_cgroup *pos;
        struct mem_cgroup *next;

        if (mem_cgroup_disabled())
                return NULL;

        if (!root)
                root = root_mem_cgroup;

        rcu_read_lock();
restart:
        next = NULL;

        if (reclaim) {
                int gen;
                int nid = reclaim->pgdat->node_id;

                iter = &root->nodeinfo[nid]->iter;
                gen = atomic_read(&iter->generation);

                /*
                 * On start, join the current reclaim iteration cycle.
                 * Exit when a concurrent walker completes it.
                 */
                if (!prev)
                        reclaim->generation = gen;
                else if (reclaim->generation != gen)
                        goto out_unlock;

                pos = READ_ONCE(iter->position);
        } else
                pos = prev;

        css = pos ? &pos->css : NULL;

        while ((css = css_next_descendant_pre(css, &root->css))) {
                /*
                 * 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.
                 */
                if (css == &root->css || css_tryget(css))
                        break;
        }

        next = mem_cgroup_from_css(css);

        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.
                 */
                if (cmpxchg(&iter->position, pos, next) != pos) {
                        if (css && css != &root->css)
                                css_put(css);
                        goto restart;
                }

                if (!next) {
                        atomic_inc(&iter->generation);

                        /*
                         * 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)
                                goto restart;
                }
        }

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

        return next;
}

/**
 * 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 cgroup1 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 (!mem_cgroup_is_root(last))
                __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. Otherwise, it will iterate
 * over all tasks and return 0.
 *
 * This function must not be called for the root memory cgroup.
 */
void 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(mem_cgroup_is_root(memcg));

        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;
                }
        }
}

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

        if (mem_cgroup_disabled())
                return;

        memcg = folio_memcg(folio);

        if (!memcg)
                VM_BUG_ON_FOLIO(!mem_cgroup_is_root(lruvec_memcg(lruvec)), folio);
        else
                VM_BUG_ON_FOLIO(lruvec_memcg(lruvec) != memcg, folio);
}
#endif

/**
 * folio_lruvec_lock - Lock the lruvec for a folio.
 * @folio: Pointer to the folio.
 *
 * These functions are safe to use under any of the following conditions:
 * - folio locked
 * - folio_test_lru false
 * - folio frozen (refcount of 0)
 *
 * Return: The lruvec this folio is on with its lock held.
 */
struct lruvec *folio_lruvec_lock(struct folio *folio)
{
        struct lruvec *lruvec = folio_lruvec(folio);

        spin_lock(&lruvec->lru_lock);
        lruvec_memcg_debug(lruvec, folio);

        return lruvec;
}

/**
 * folio_lruvec_lock_irq - Lock the lruvec for a folio.
 * @folio: Pointer to the folio.
 *
 * These functions are safe to use under any of the following conditions:
 * - folio locked
 * - folio_test_lru false
 * - folio frozen (refcount of 0)
 *
 * Return: The lruvec this folio is on with its lock held and interrupts
 * disabled.
 */
struct lruvec *folio_lruvec_lock_irq(struct folio *folio)
{
        struct lruvec *lruvec = folio_lruvec(folio);

        spin_lock_irq(&lruvec->lru_lock);
        lruvec_memcg_debug(lruvec, folio);

        return lruvec;
}

/**
 * folio_lruvec_lock_irqsave - Lock the lruvec for a folio.
 * @folio: Pointer to the folio.
 * @flags: Pointer to irqsave flags.
 *
 * These functions are safe to use under any of the following conditions:
 * - folio locked
 * - folio_test_lru false
 * - folio frozen (refcount of 0)
 *
 * Return: The lruvec this folio is on with its lock held and interrupts
 * disabled.
 */
struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio,
                unsigned long *flags)
{
        struct lruvec *lruvec = folio_lruvec(folio);

        spin_lock_irqsave(&lruvec->lru_lock, *flags);
        lruvec_memcg_debug(lruvec, folio);

        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.
 */
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;
}

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",                     MEMCG_KMEM                      },
        { "kernel_stack",               NR_KERNEL_STACK_KB              },
        { "pagetables",                 NR_PAGETABLE                    },
        { "sec_pagetables",             NR_SECONDARY_PAGETABLE          },
        { "percpu",                     MEMCG_PERCPU_B                  },
        { "sock",                       MEMCG_SOCK                      },
        { "vmalloc",                    MEMCG_VMALLOC                   },
        { "shmem",                      NR_SHMEM                        },
#ifdef CONFIG_ZSWAP
        { "zswap",                      MEMCG_ZSWAP_B                   },
        { "zswapped",                   MEMCG_ZSWAPPED                  },
#endif
        { "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         },
#ifdef CONFIG_HUGETLB_PAGE
        { "hugetlb",                    NR_HUGETLB                      },
#endif

        /* 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          },

        { "pgdemote_kswapd",            PGDEMOTE_KSWAPD         },
        { "pgdemote_direct",            PGDEMOTE_DIRECT         },
        { "pgdemote_khugepaged",        PGDEMOTE_KHUGEPAGED     },
#ifdef CONFIG_NUMA_BALANCING
        { "pgpromote_success",          PGPROMOTE_SUCCESS       },
#endif
};

/* The actual unit of the state item, not the same as the output unit */
static int memcg_page_state_unit(int item)
{
        switch (item) {
        case MEMCG_PERCPU_B:
        case MEMCG_ZSWAP_B:
        case NR_SLAB_RECLAIMABLE_B:
        case NR_SLAB_UNRECLAIMABLE_B:
                return 1;
        case NR_KERNEL_STACK_KB:
                return SZ_1K;
        default:
                return PAGE_SIZE;
        }
}

/* Translate stat items to the correct unit for memory.stat output */
static int memcg_page_state_output_unit(int item)
{
        /*
         * Workingset state is actually in pages, but we export it to userspace
         * as a scalar count of events, so special case it here.
         *
         * Demotion and promotion activities are exported in pages, consistent
         * with their global counterparts.
         */
        switch (item) {
        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:
        case PGDEMOTE_KSWAPD:
        case PGDEMOTE_DIRECT:
        case PGDEMOTE_KHUGEPAGED:
#ifdef CONFIG_NUMA_BALANCING
        case PGPROMOTE_SUCCESS:
#endif
                return 1;
        default:
                return memcg_page_state_unit(item);
        }
}

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

unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item)
{
        return memcg_page_state_local(memcg, item) *
                memcg_page_state_output_unit(item);
}

static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
{
        int i;

        /*
         * 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:
         */
        mem_cgroup_flush_stats(memcg);

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

#ifdef CONFIG_HUGETLB_PAGE
                if (unlikely(memory_stats[i].idx == NR_HUGETLB) &&
                    !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
                        continue;
#endif
                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, "pgscan %lu\n",
                       memcg_events(memcg, PGSCAN_KSWAPD) +
                       memcg_events(memcg, PGSCAN_DIRECT) +
                       memcg_events(memcg, PGSCAN_KHUGEPAGED));
        seq_buf_printf(s, "pgsteal %lu\n",
                       memcg_events(memcg, PGSTEAL_KSWAPD) +
                       memcg_events(memcg, PGSTEAL_DIRECT) +
                       memcg_events(memcg, PGSTEAL_KHUGEPAGED));

        for (i = 0; i < ARRAY_SIZE(memcg_vm_event_stat); i++) {
#ifdef CONFIG_MEMCG_V1
                if (memcg_vm_event_stat[i] == PGPGIN ||
                    memcg_vm_event_stat[i] == PGPGOUT)
                        continue;
#endif
                seq_buf_printf(s, "%s %lu\n",
                               vm_event_name(memcg_vm_event_stat[i]),
                               memcg_events(memcg, memcg_vm_event_stat[i]));
        }
}

static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
{
        if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
                memcg_stat_format(memcg, s);
        else
                memcg1_stat_format(memcg, s);
        if (seq_buf_has_overflowed(s))
                pr_warn("%s: Warning, stat buffer overflow, please report\n", __func__);
}

/**
 * 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)
{
        /* Use static buffer, for the caller is holding oom_lock. */
        static char buf[SEQ_BUF_SIZE];
        struct seq_buf s;

        lockdep_assert_held(&oom_lock);

        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);
#ifdef CONFIG_MEMCG_V1
        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);
        }
#endif

        pr_info("Memory cgroup stats for ");
        pr_cont_cgroup_path(memcg->css.cgroup);
        pr_cont(":");
        seq_buf_init(&s, buf, SEQ_BUF_SIZE);
        memory_stat_format(memcg, &s);
        seq_buf_do_printk(&s, KERN_INFO);
}

/*
 * 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 (do_memsw_account()) {
                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);
                }
        } else {
                if (mem_cgroup_swappiness(memcg))
                        max += min(READ_ONCE(memcg->swap.max),
                                   (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 = task_is_dying() || out_of_memory(&oc);

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

/*
 * Returns true if successfully killed one or more processes. Though in some
 * corner cases it can return true even without killing any process.
 */
static bool mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order)
{
        bool locked, ret;

        if (order > PAGE_ALLOC_COSTLY_ORDER)
                return false;

        memcg_memory_event(memcg, MEMCG_OOM);

        if (!memcg1_oom_prepare(memcg, &locked))
                return false;

        ret = mem_cgroup_out_of_memory(memcg, mask, order);

        memcg1_oom_finish(memcg, locked);

        return ret;
}

/**
 * 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 (mem_cgroup_is_root(memcg))
                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 (READ_ONCE(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");
}

struct memcg_stock_pcp {
        local_lock_t stock_lock;
        struct mem_cgroup *cached; /* this never be root cgroup */
        unsigned int nr_pages;

        struct obj_cgroup *cached_objcg;
        struct pglist_data *cached_pgdat;
        unsigned int nr_bytes;
        int nr_slab_reclaimable_b;
        int nr_slab_unreclaimable_b;

        struct work_struct work;
        unsigned long flags;
#define FLUSHING_CACHED_CHARGE  0
};
static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock) = {
        .stock_lock = INIT_LOCAL_LOCK(stock_lock),
};
static DEFINE_MUTEX(percpu_charge_mutex);

static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock);
static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
                                     struct mem_cgroup *root_memcg);

/**
 * 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 int stock_pages;
        unsigned long flags;
        bool ret = false;

        if (nr_pages > MEMCG_CHARGE_BATCH)
                return ret;

        local_lock_irqsave(&memcg_stock.stock_lock, flags);

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

        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);

        return ret;
}

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

        if (!old)
                return;

        if (stock_pages) {
                page_counter_uncharge(&old->memory, stock_pages);
                if (do_memsw_account())
                        page_counter_uncharge(&old->memsw, stock_pages);

                WRITE_ONCE(stock->nr_pages, 0);
        }

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

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

        /*
         * The only protection from cpu hotplug (memcg_hotplug_cpu_dead) vs.
         * drain_stock races is that we always operate on local CPU stock
         * here with IRQ disabled
         */
        local_lock_irqsave(&memcg_stock.stock_lock, flags);

        stock = this_cpu_ptr(&memcg_stock);
        old = drain_obj_stock(stock);
        drain_stock(stock);
        clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);

        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
        obj_cgroup_put(old);
}

/*
 * 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 int stock_pages;

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

        if (stock_pages > MEMCG_CHARGE_BATCH)
                drain_stock(stock);
}

static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
{
        unsigned long flags;

        local_lock_irqsave(&memcg_stock.stock_lock, flags);
        __refill_stock(memcg, nr_pages);
        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
}

/*
 * Drains all per-CPU charge caches for given root_memcg resp. subtree
 * of the hierarchy under it.
 */
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.
         */
        migrate_disable();
        curcpu = smp_processor_id();
        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 = READ_ONCE(stock->cached);
                if (memcg && READ_ONCE(stock->nr_pages) &&
                    mem_cgroup_is_descendant(memcg, root_memcg))
                        flush = true;
                else 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 if (!cpu_is_isolated(cpu))
                                schedule_work_on(cpu, &stock->work);
                }
        }
        migrate_enable();
        mutex_unlock(&percpu_charge_mutex);
}

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

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

        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,
                                                        MEMCG_RECLAIM_MAY_SWAP,
                                                        NULL);
                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;
}

/*
 * Reclaims memory over the high limit. Called directly from
 * try_charge() (context permitting), as well as from the userland
 * return path where reclaim is always able to block.
 */
void mem_cgroup_handle_over_high(gfp_t gfp_mask)
{
        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:
        /*
         * Bail if the task is already exiting. Unlike memory.max,
         * memory.high enforcement isn't as strict, and there is no
         * OOM killer involved, which means the excess could already
         * be much bigger (and still growing) than it could for
         * memory.max; the dying task could get stuck in fruitless
         * reclaim for a long time, which isn't desirable.
         */
        if (task_is_dying())
                goto out;

        /*
         * 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_mask);

        /*
         * 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;
        }

        /*
         * Reclaim didn't manage to push usage below the limit, slow
         * this allocating task down.
         *
         * 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);
}

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;
        unsigned long nr_reclaimed;
        bool passed_oom = false;
        unsigned int reclaim_options = MEMCG_RECLAIM_MAY_SWAP;
        bool drained = false;
        bool raised_max_event = 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);
                reclaim_options &= ~MEMCG_RECLAIM_MAY_SWAP;
        }

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

        /*
         * 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);
        raised_max_event = true;

        psi_memstall_enter(&pflags);
        nr_reclaimed = try_to_free_mem_cgroup_pages(mem_over_limit, nr_pages,
                                                    gfp_mask, reclaim_options, NULL);
        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;

        if (nr_retries--)
                goto retry;

        if (gfp_mask & __GFP_RETRY_MAYFAIL)
                goto nomem;

        /* Avoid endless loop for tasks bypassed by the oom killer */
        if (passed_oom && task_is_dying())
                goto nomem;

        /*
         * 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.
         */
        if (mem_cgroup_oom(mem_over_limit, gfp_mask,
                           get_order(nr_pages * PAGE_SIZE))) {
                passed_oom = true;
                nr_retries = MAX_RECLAIM_RETRIES;
                goto retry;
        }
nomem:
        /*
         * 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_NOFAIL | __GFP_HIGH)))
                return -ENOMEM;
force:
        /*
         * If the allocation has to be enforced, don't forget to raise
         * a MEMCG_MAX event.
         */
        if (!raised_max_event)
                memcg_memory_event(mem_over_limit, MEMCG_MAX);

        /*
         * 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_task()) {
                        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)));

        /*
         * Reclaim is set up above to be called from the userland
         * return path. But also attempt synchronous reclaim to avoid
         * excessive overrun while the task is still inside the
         * kernel. If this is successful, the return path will see it
         * when it rechecks the overage and simply bail out.
         */
        if (current->memcg_nr_pages_over_high > MEMCG_CHARGE_BATCH &&
            !(current->flags & PF_MEMALLOC) &&
            gfpflags_allow_blocking(gfp_mask))
                mem_cgroup_handle_over_high(gfp_mask);
        return 0;
}

/**
 * mem_cgroup_cancel_charge() - cancel an uncommitted try_charge() call.
 * @memcg: memcg previously charged.
 * @nr_pages: number of pages previously charged.
 */
void mem_cgroup_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);
}

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

/**
 * mem_cgroup_commit_charge - commit a previously successful try_charge().
 * @folio: folio to commit the charge to.
 * @memcg: memcg previously charged.
 */
void mem_cgroup_commit_charge(struct folio *folio, struct mem_cgroup *memcg)
{
        css_get(&memcg->css);
        commit_charge(folio, memcg);
        memcg1_commit_charge(folio, memcg);
}

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();
}

static __always_inline
struct mem_cgroup *mem_cgroup_from_obj_folio(struct folio *folio, void *p)
{
        /*
         * Slab objects are accounted individually, not per-page.
         * Memcg membership data for each individual object is saved in
         * slab->obj_exts.
         */
        if (folio_test_slab(folio)) {
                struct slabobj_ext *obj_exts;
                struct slab *slab;
                unsigned int off;

                slab = folio_slab(folio);
                obj_exts = slab_obj_exts(slab);
                if (!obj_exts)
                        return NULL;

                off = obj_to_index(slab->slab_cache, slab, p);
                if (obj_exts[off].objcg)
                        return obj_cgroup_memcg(obj_exts[off].objcg);

                return NULL;
        }

        /*
         * folio_memcg_check() is used here, because in theory we can encounter
         * a folio where the slab flag has been cleared already, but
         * slab->obj_exts has not been freed yet
         * folio_memcg_check() will guarantee that a proper memory
         * cgroup pointer or NULL will be returned.
         */
        return folio_memcg_check(folio);
}

/*
 * Returns a pointer to the memory cgroup to which the kernel object is charged.
 * It is not suitable for objects allocated using vmalloc().
 *
 * A passed kernel object must be a slab object or a generic kernel page.
 *
 * The caller must ensure the memcg lifetime, e.g. by taking rcu_read_lock(),
 * cgroup_mutex, etc.
 */
struct mem_cgroup *mem_cgroup_from_slab_obj(void *p)
{
        if (mem_cgroup_disabled())
                return NULL;

        return mem_cgroup_from_obj_folio(virt_to_folio(p), p);
}

static struct obj_cgroup *__get_obj_cgroup_from_memcg(struct mem_cgroup *memcg)
{
        struct obj_cgroup *objcg = NULL;

        for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) {
                objcg = rcu_dereference(memcg->objcg);
                if (likely(objcg && obj_cgroup_tryget(objcg)))
                        break;
                objcg = NULL;
        }
        return objcg;
}

static struct obj_cgroup *current_objcg_update(void)
{
        struct mem_cgroup *memcg;
        struct obj_cgroup *old, *objcg = NULL;

        do {
                /* Atomically drop the update bit. */
                old = xchg(&current->objcg, NULL);
                if (old) {
                        old = (struct obj_cgroup *)
                                ((unsigned long)old & ~CURRENT_OBJCG_UPDATE_FLAG);
                        obj_cgroup_put(old);

                        old = NULL;
                }

                /* If new objcg is NULL, no reason for the second atomic update. */
                if (!current->mm || (current->flags & PF_KTHREAD))
                        return NULL;

                /*
                 * Release the objcg pointer from the previous iteration,
                 * if try_cmpxcg() below fails.
                 */
                if (unlikely(objcg)) {
                        obj_cgroup_put(objcg);
                        objcg = NULL;
                }

                /*
                 * Obtain the new objcg pointer. The current task can be
                 * asynchronously moved to another memcg and the previous
                 * memcg can be offlined. So let's get the memcg pointer
                 * and try get a reference to objcg under a rcu read lock.
                 */

                rcu_read_lock();
                memcg = mem_cgroup_from_task(current);
                objcg = __get_obj_cgroup_from_memcg(memcg);
                rcu_read_unlock();

                /*
                 * Try set up a new objcg pointer atomically. If it
                 * fails, it means the update flag was set concurrently, so
                 * the whole procedure should be repeated.
                 */
        } while (!try_cmpxchg(&current->objcg, &old, objcg));

        return objcg;
}

__always_inline struct obj_cgroup *current_obj_cgroup(void)
{
        struct mem_cgroup *memcg;
        struct obj_cgroup *objcg;

        if (in_task()) {
                memcg = current->active_memcg;
                if (unlikely(memcg))
                        goto from_memcg;

                objcg = READ_ONCE(current->objcg);
                if (unlikely((unsigned long)objcg & CURRENT_OBJCG_UPDATE_FLAG))
                        objcg = current_objcg_update();
                /*
                 * Objcg reference is kept by the task, so it's safe
                 * to use the objcg by the current task.
                 */
                return objcg;
        }

        memcg = this_cpu_read(int_active_memcg);
        if (unlikely(memcg))
                goto from_memcg;

        return NULL;

from_memcg:
        objcg = NULL;
        for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) {
                /*
                 * Memcg pointer is protected by scope (see set_active_memcg())
                 * and is pinning the corresponding objcg, so objcg can't go
                 * away and can be used within the scope without any additional
                 * protection.
                 */
                objcg = rcu_dereference_check(memcg->objcg, 1);
                if (likely(objcg))
                        break;
        }

        return objcg;
}

struct obj_cgroup *get_obj_cgroup_from_folio(struct folio *folio)
{
        struct obj_cgroup *objcg;

        if (!memcg_kmem_online())
                return NULL;

        if (folio_memcg_kmem(folio)) {
                objcg = __folio_objcg(folio);
                obj_cgroup_get(objcg);
        } else {
                struct mem_cgroup *memcg;

                rcu_read_lock();
                memcg = __folio_memcg(folio);
                if (memcg)
                        objcg = __get_obj_cgroup_from_memcg(memcg);
                else
                        objcg = NULL;
                rcu_read_unlock();
        }
        return objcg;
}

/*
 * 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);

        mod_memcg_state(memcg, MEMCG_KMEM, -nr_pages);
        memcg1_account_kmem(memcg, -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 mem_cgroup *memcg;
        int ret;

        memcg = get_mem_cgroup_from_objcg(objcg);

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

        mod_memcg_state(memcg, MEMCG_KMEM, nr_pages);
        memcg1_account_kmem(memcg, nr_pages);
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 = current_obj_cgroup();
        if (objcg) {
                ret = obj_cgroup_charge_pages(objcg, gfp, 1 << order);
                if (!ret) {
                        obj_cgroup_get(objcg);
                        page->memcg_data = (unsigned long)objcg |
                                MEMCG_DATA_KMEM;
                        return 0;
                }
        }
        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 folio *folio = page_folio(page);
        struct obj_cgroup *objcg;
        unsigned int nr_pages = 1 << order;

        if (!folio_memcg_kmem(folio))
                return;

        objcg = __folio_objcg(folio);
        obj_cgroup_uncharge_pages(objcg, nr_pages);
        folio->memcg_data = 0;
        obj_cgroup_put(objcg);
}

static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
                     enum node_stat_item idx, int nr)
{
        struct memcg_stock_pcp *stock;
        struct obj_cgroup *old = NULL;
        unsigned long flags;
        int *bytes;

        local_lock_irqsave(&memcg_stock.stock_lock, flags);
        stock = this_cpu_ptr(&memcg_stock);

        /*
         * 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 (READ_ONCE(stock->cached_objcg) != objcg) {
                old = 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;
                WRITE_ONCE(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);

        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
        obj_cgroup_put(old);
}

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

        local_lock_irqsave(&memcg_stock.stock_lock, flags);

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

        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);

        return ret;
}

static struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock)
{
        struct obj_cgroup *old = READ_ONCE(stock->cached_objcg);

        if (!old)
                return NULL;

        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) {
                        struct mem_cgroup *memcg;

                        memcg = get_mem_cgroup_from_objcg(old);

                        mod_memcg_state(memcg, MEMCG_KMEM, -nr_pages);
                        memcg1_account_kmem(memcg, -nr_pages);
                        __refill_stock(memcg, nr_pages);

                        css_put(&memcg->css);
                }

                /*
                 * 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;
        }

        WRITE_ONCE(stock->cached_objcg, NULL);
        /*
         * The `old' objects needs to be released by the caller via
         * obj_cgroup_put() outside of memcg_stock_pcp::stock_lock.
         */
        return old;
}

static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
                                     struct mem_cgroup *root_memcg)
{
        struct obj_cgroup *objcg = READ_ONCE(stock->cached_objcg);
        struct mem_cgroup *memcg;

        if (objcg) {
                memcg = obj_cgroup_memcg(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)
{
        struct memcg_stock_pcp *stock;
        struct obj_cgroup *old = NULL;
        unsigned long flags;
        unsigned int nr_pages = 0;

        local_lock_irqsave(&memcg_stock.stock_lock, flags);

        stock = this_cpu_ptr(&memcg_stock);
        if (READ_ONCE(stock->cached_objcg) != objcg) { /* reset if necessary */
                old = drain_obj_stock(stock);
                obj_cgroup_get(objcg);
                WRITE_ONCE(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);
        }

        local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
        obj_cgroup_put(old);

        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);
}

static inline size_t obj_full_size(struct kmem_cache *s)
{
        /*
         * For each accounted object there is an extra space which is used
         * to store obj_cgroup membership. Charge it too.
         */
        return s->size + sizeof(struct obj_cgroup *);
}

bool __memcg_slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru,
                                  gfp_t flags, size_t size, void **p)
{
        struct obj_cgroup *objcg;
        struct slab *slab;
        unsigned long off;
        size_t i;

        /*
         * The obtained objcg pointer is safe to use within the current scope,
         * defined by current task or set_active_memcg() pair.
         * obj_cgroup_get() is used to get a permanent reference.
         */
        objcg = current_obj_cgroup();
        if (!objcg)
                return true;

        /*
         * slab_alloc_node() avoids the NULL check, so we might be called with a
         * single NULL object. kmem_cache_alloc_bulk() aborts if it can't fill
         * the whole requested size.
         * return success as there's nothing to free back
         */
        if (unlikely(*p == NULL))
                return true;

        flags &= gfp_allowed_mask;

        if (lru) {
                int ret;
                struct mem_cgroup *memcg;

                memcg = get_mem_cgroup_from_objcg(objcg);
                ret = memcg_list_lru_alloc(memcg, lru, flags);
                css_put(&memcg->css);

                if (ret)
                        return false;
        }

        if (obj_cgroup_charge(objcg, flags, size * obj_full_size(s)))
                return false;

        for (i = 0; i < size; i++) {
                slab = virt_to_slab(p[i]);

                if (!slab_obj_exts(slab) &&
                    alloc_slab_obj_exts(slab, s, flags, false)) {
                        obj_cgroup_uncharge(objcg, obj_full_size(s));
                        continue;
                }

                off = obj_to_index(s, slab, p[i]);
                obj_cgroup_get(objcg);
                slab_obj_exts(slab)[off].objcg = objcg;
                mod_objcg_state(objcg, slab_pgdat(slab),
                                cache_vmstat_idx(s), obj_full_size(s));
        }

        return true;
}

void __memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab,
                            void **p, int objects, struct slabobj_ext *obj_exts)
{
        for (int i = 0; i < objects; i++) {
                struct obj_cgroup *objcg;
                unsigned int off;

                off = obj_to_index(s, slab, p[i]);
                objcg = obj_exts[off].objcg;
                if (!objcg)
                        continue;

                obj_exts[off].objcg = NULL;
                obj_cgroup_uncharge(objcg, obj_full_size(s));
                mod_objcg_state(objcg, slab_pgdat(slab), cache_vmstat_idx(s),
                                -obj_full_size(s));
                obj_cgroup_put(objcg);
        }
}

/*
 * Because folio_memcg(head) is not set on tails, set it now.
 */
void split_page_memcg(struct page *head, int old_order, int new_order)
{
        struct folio *folio = page_folio(head);
        int i;
        unsigned int old_nr = 1 << old_order;
        unsigned int new_nr = 1 << new_order;

        if (mem_cgroup_disabled() || !folio_memcg_charged(folio))
                return;

        for (i = new_nr; i < old_nr; i += new_nr)
                folio_page(folio, i)->memcg_data = folio->memcg_data;

        if (folio_memcg_kmem(folio))
                obj_cgroup_get_many(__folio_objcg(folio), old_nr / new_nr - 1);
        else
                css_get_many(&folio_memcg(folio)->css, old_nr / new_nr - 1);
}

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 int memcg_online_kmem(struct mem_cgroup *memcg)
{
        struct obj_cgroup *objcg;

        if (mem_cgroup_kmem_disabled())
                return 0;

        if (unlikely(mem_cgroup_is_root(memcg)))
                return 0;

        objcg = obj_cgroup_alloc();
        if (!objcg)
                return -ENOMEM;

        objcg->memcg = memcg;
        rcu_assign_pointer(memcg->objcg, objcg);
        obj_cgroup_get(objcg);
        memcg->orig_objcg = objcg;

        static_branch_enable(&memcg_kmem_online_key);

        memcg->kmemcg_id = memcg->id.id;

        return 0;
}

static void memcg_offline_kmem(struct mem_cgroup *memcg)
{
        struct mem_cgroup *parent;

        if (mem_cgroup_kmem_disabled())
                return;

        if (unlikely(mem_cgroup_is_root(memcg)))
                return;

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

        memcg_reparent_list_lrus(memcg, parent);

        /*
         * Objcg's reparenting must be after list_lru's, make sure list_lru
         * helpers won't use parent's list_lru until child is drained.
         */
        memcg_reparent_objcgs(memcg, parent);
}

#ifdef CONFIG_CGROUP_WRITEBACK

#include <trace/events/writeback.h>

static int memcg_wb_domain_init(struct mem_cgroup *memcg, gfp_t gfp)
{
        return wb_domain_init(&memcg->cgwb_domain, gfp);
}

static void memcg_wb_domain_exit(struct mem_cgroup *memcg)
{
        wb_domain_exit(&memcg->cgwb_domain);
}

static void memcg_wb_domain_size_changed(struct mem_cgroup *memcg)
{
        wb_domain_size_changed(&memcg->cgwb_domain);
}

struct wb_domain *mem_cgroup_wb_domain(struct bdi_writeback *wb)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css);

        if (!memcg->css.parent)
                return NULL;

        return &memcg->cgwb_domain;
}

/**
 * mem_cgroup_wb_stats - retrieve writeback related stats from its memcg
 * @wb: bdi_writeback in question
 * @pfilepages: out parameter for number of file pages
 * @pheadroom: out parameter for number of allocatable pages according to memcg
 * @pdirty: out parameter for number of dirty pages
 * @pwriteback: out parameter for number of pages under writeback
 *
 * Determine the numbers of file, headroom, dirty, and writeback pages in
 * @wb's memcg.  File, dirty and writeback are self-explanatory.  Headroom
 * is a bit more involved.
 *
 * A memcg's headroom is "min(max, high) - used".  In the hierarchy, the
 * headroom is calculated as the lowest headroom of itself and the
 * ancestors.  Note that this doesn't consider the actual amount of
 * available memory in the system.  The caller should further cap
 * *@pheadroom accordingly.
 */
void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages,
                         unsigned long *pheadroom, unsigned long *pdirty,
                         unsigned long *pwriteback)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css);
        struct mem_cgroup *parent;

        mem_cgroup_flush_stats_ratelimited(memcg);

        *pdirty = memcg_page_state(memcg, NR_FILE_DIRTY);
        *pwriteback = memcg_page_state(memcg, NR_WRITEBACK);
        *pfilepages = memcg_page_state(memcg, NR_INACTIVE_FILE) +
                        memcg_page_state(memcg, NR_ACTIVE_FILE);

        *pheadroom = PAGE_COUNTER_MAX;
        while ((parent = parent_mem_cgroup(memcg))) {
                unsigned long ceiling = min(READ_ONCE(memcg->memory.max),
                                            READ_ONCE(memcg->memory.high));
                unsigned long used = page_counter_read(&memcg->memory);

                *pheadroom = min(*pheadroom, ceiling - min(ceiling, used));
                memcg = parent;
        }
}

/*
 * Foreign dirty flushing
 *
 * There's an inherent mismatch between memcg and writeback.  The former
 * tracks ownership per-page while the latter per-inode.  This was a
 * deliberate design decision because honoring per-page ownership in the
 * writeback path is complicated, may lead to higher CPU and IO overheads
 * and deemed unnecessary given that write-sharing an inode across
 * different cgroups isn't a common use-case.
 *
 * Combined with inode majority-writer ownership switching, this works well
 * enough in most cases but there are some pathological cases.  For
 * example, let's say there are two cgroups A and B which keep writing to
 * different but confined parts of the same inode.  B owns the inode and
 * A's memory is limited far below B's.  A's dirty ratio can rise enough to
 * trigger balance_dirty_pages() sleeps but B's can be low enough to avoid
 * triggering background writeback.  A will be slowed down without a way to
 * make writeback of the dirty pages happen.
 *
 * Conditions like the above can lead to a cgroup getting repeatedly and
 * severely throttled after making some progress after each
 * dirty_expire_interval while the underlying IO device is almost
 * completely idle.
 *
 * Solving this problem completely requires matching the ownership tracking
 * granularities between memcg and writeback in either direction.  However,
 * the more egregious behaviors can be avoided by simply remembering the
 * most recent foreign dirtying events and initiating remote flushes on
 * them when local writeback isn't enough to keep the memory clean enough.
 *
 * The following two functions implement such mechanism.  When a foreign
 * page - a page whose memcg and writeback ownerships don't match - is
 * dirtied, mem_cgroup_track_foreign_dirty() records the inode owning
 * bdi_writeback on the page owning memcg.  When balance_dirty_pages()
 * decides that the memcg needs to sleep due to high dirty ratio, it calls
 * mem_cgroup_flush_foreign() which queues writeback on the recorded
 * foreign bdi_writebacks which haven't expired.  Both the numbers of
 * recorded bdi_writebacks and concurrent in-flight foreign writebacks are
 * limited to MEMCG_CGWB_FRN_CNT.
 *
 * The mechanism only remembers IDs and doesn't hold any object references.
 * As being wrong occasionally doesn't matter, updates and accesses to the
 * records are lockless and racy.
 */
void mem_cgroup_track_foreign_dirty_slowpath(struct folio *folio,
                                             struct bdi_writeback *wb)
{
        struct mem_cgroup *memcg = folio_memcg(folio);
        struct memcg_cgwb_frn *frn;
        u64 now = get_jiffies_64();
        u64 oldest_at = now;
        int oldest = -1;
        int i;

        trace_track_foreign_dirty(folio, wb);

        /*
         * Pick the slot to use.  If there is already a slot for @wb, keep
         * using it.  If not replace the oldest one which isn't being
         * written out.
         */
        for (i = 0; i < MEMCG_CGWB_FRN_CNT; i++) {
                frn = &memcg->cgwb_frn[i];
                if (frn->bdi_id == wb->bdi->id &&
                    frn->memcg_id == wb->memcg_css->id)
                        break;
                if (time_before64(frn->at, oldest_at) &&
                    atomic_read(&frn->done.cnt) == 1) {
                        oldest = i;
                        oldest_at = frn->at;
                }
        }

        if (i < MEMCG_CGWB_FRN_CNT) {
                /*
                 * Re-using an existing one.  Update timestamp lazily to
                 * avoid making the cacheline hot.  We want them to be
                 * reasonably up-to-date and significantly shorter than
                 * dirty_expire_interval as that's what expires the record.
                 * Use the shorter of 1s and dirty_expire_interval / 8.
                 */
                unsigned long update_intv =
                        min_t(unsigned long, HZ,
                              msecs_to_jiffies(dirty_expire_interval * 10) / 8);

                if (time_before64(frn->at, now - update_intv))
                        frn->at = now;
        } else if (oldest >= 0) {
                /* replace the oldest free one */
                frn = &memcg->cgwb_frn[oldest];
                frn->bdi_id = wb->bdi->id;
                frn->memcg_id = wb->memcg_css->id;
                frn->at = now;
        }
}

/* issue foreign writeback flushes for recorded foreign dirtying events */
void mem_cgroup_flush_foreign(struct bdi_writeback *wb)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css);
        unsigned long intv = msecs_to_jiffies(dirty_expire_interval * 10);
        u64 now = jiffies_64;
        int i;

        for (i = 0; i < MEMCG_CGWB_FRN_CNT; i++) {
                struct memcg_cgwb_frn *frn = &memcg->cgwb_frn[i];

                /*
                 * If the record is older than dirty_expire_interval,
                 * writeback on it has already started.  No need to kick it
                 * off again.  Also, don't start a new one if there's
                 * already one in flight.
                 */
                if (time_after64(frn->at, now - intv) &&
                    atomic_read(&frn->done.cnt) == 1) {
                        frn->at = 0;
                        trace_flush_foreign(wb, frn->bdi_id, frn->memcg_id);
                        cgroup_writeback_by_id(frn->bdi_id, frn->memcg_id,
                                               WB_REASON_FOREIGN_FLUSH,
                                               &frn->done);
                }
        }
}

#else   /* CONFIG_CGROUP_WRITEBACK */

static int memcg_wb_domain_init(struct mem_cgroup *memcg, gfp_t gfp)
{
        return 0;
}

static void memcg_wb_domain_exit(struct mem_cgroup *memcg)
{
}

static void memcg_wb_domain_size_changed(struct mem_cgroup *memcg)
{
}

#endif  /* CONFIG_CGROUP_WRITEBACK */

/*
 * Private memory cgroup IDR
 *
 * Swap-out records and page cache shadow entries need to store memcg
 * references in constrained space, so we maintain an ID space that is
 * limited to 16 bit (MEM_CGROUP_ID_MAX), limiting the total number of
 * memory-controlled cgroups to 64k.
 *
 * However, there usually are many references to the offline CSS after
 * the cgroup has been destroyed, such as page cache or reclaimable
 * slab objects, that don't need to hang on to the ID. We want to keep
 * those dead CSS from occupying IDs, or we might quickly exhaust the
 * relatively small ID space and prevent the creation of new cgroups
 * even when there are much fewer than 64k cgroups - possibly none.
 *
 * Maintain a private 16-bit ID space for memcg, and allow the ID to
 * be freed and recycled when it's no longer needed, which is usually
 * when the CSS is offlined.
 *
 * The only exception to that are records of swapped out tmpfs/shmem
 * pages that need to be attributed to live ancestors on swapin. But
 * those references are manageable from userspace.
 */

#define MEM_CGROUP_ID_MAX       ((1UL << MEM_CGROUP_ID_SHIFT) - 1)
static DEFINE_XARRAY_ALLOC1(mem_cgroup_ids);

static void mem_cgroup_id_remove(struct mem_cgroup *memcg)
{
        if (memcg->id.id > 0) {
                xa_erase(&mem_cgroup_ids, memcg->id.id);
                memcg->id.id = 0;
        }
}

void __maybe_unused mem_cgroup_id_get_many(struct mem_cgroup *memcg,
                                           unsigned int n)
{
        refcount_add(n, &memcg->id.ref);
}

void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n)
{
        if (refcount_sub_and_test(n, &memcg->id.ref)) {
                mem_cgroup_id_remove(memcg);

                /* Memcg ID pins CSS */
                css_put(&memcg->css);
        }
}

static inline void mem_cgroup_id_put(struct mem_cgroup *memcg)
{
        mem_cgroup_id_put_many(memcg, 1);
}

/**
 * mem_cgroup_from_id - look up a memcg from a memcg id
 * @id: the memcg id to look up
 *
 * Caller must hold rcu_read_lock().
 */
struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
{
        WARN_ON_ONCE(!rcu_read_lock_held());
        return xa_load(&mem_cgroup_ids, id);
}

#ifdef CONFIG_SHRINKER_DEBUG
struct mem_cgroup *mem_cgroup_get_from_ino(unsigned long ino)
{
        struct cgroup *cgrp;
        struct cgroup_subsys_state *css;
        struct mem_cgroup *memcg;

        cgrp = cgroup_get_from_id(ino);
        if (IS_ERR(cgrp))
                return ERR_CAST(cgrp);

        css = cgroup_get_e_css(cgrp, &memory_cgrp_subsys);
        if (css)
                memcg = container_of(css, struct mem_cgroup, css);
        else
                memcg = ERR_PTR(-ENOENT);

        cgroup_put(cgrp);

        return memcg;
}
#endif

static bool alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
{
        struct mem_cgroup_per_node *pn;

        pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, node);
        if (!pn)
                return false;

        pn->lruvec_stats = kzalloc_node(sizeof(struct lruvec_stats),
                                        GFP_KERNEL_ACCOUNT, node);
        if (!pn->lruvec_stats)
                goto fail;

        pn->lruvec_stats_percpu = alloc_percpu_gfp(struct lruvec_stats_percpu,
                                                   GFP_KERNEL_ACCOUNT);
        if (!pn->lruvec_stats_percpu)
                goto fail;

        lruvec_init(&pn->lruvec);
        pn->memcg = memcg;

        memcg->nodeinfo[node] = pn;
        return true;
fail:
        kfree(pn->lruvec_stats);
        kfree(pn);
        return false;
}

static void free_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
{
        struct mem_cgroup_per_node *pn = memcg->nodeinfo[node];

        if (!pn)
                return;

        free_percpu(pn->lruvec_stats_percpu);
        kfree(pn->lruvec_stats);
        kfree(pn);
}

static void __mem_cgroup_free(struct mem_cgroup *memcg)
{
        int node;

        obj_cgroup_put(memcg->orig_objcg);

        for_each_node(node)
                free_mem_cgroup_per_node_info(memcg, node);
        memcg1_free_events(memcg);
        kfree(memcg->vmstats);
        free_percpu(memcg->vmstats_percpu);
        kfree(memcg);
}

static void mem_cgroup_free(struct mem_cgroup *memcg)
{
        lru_gen_exit_memcg(memcg);
        memcg_wb_domain_exit(memcg);
        __mem_cgroup_free(memcg);
}

static struct mem_cgroup *mem_cgroup_alloc(struct mem_cgroup *parent)
{
        struct memcg_vmstats_percpu *statc, *pstatc;
        struct mem_cgroup *memcg;
        int node, cpu;
        int __maybe_unused i;
        long error;

        memcg = kzalloc(struct_size(memcg, nodeinfo, nr_node_ids), GFP_KERNEL);
        if (!memcg)
                return ERR_PTR(-ENOMEM);

        error = xa_alloc(&mem_cgroup_ids, &memcg->id.id, NULL,
                         XA_LIMIT(1, MEM_CGROUP_ID_MAX), GFP_KERNEL);
        if (error)
                goto fail;
        error = -ENOMEM;

        memcg->vmstats = kzalloc(sizeof(struct memcg_vmstats),
                                 GFP_KERNEL_ACCOUNT);
        if (!memcg->vmstats)
                goto fail;

        memcg->vmstats_percpu = alloc_percpu_gfp(struct memcg_vmstats_percpu,
                                                 GFP_KERNEL_ACCOUNT);
        if (!memcg->vmstats_percpu)
                goto fail;

        if (!memcg1_alloc_events(memcg))
                goto fail;

        for_each_possible_cpu(cpu) {
                if (parent)
                        pstatc = per_cpu_ptr(parent->vmstats_percpu, cpu);
                statc = per_cpu_ptr(memcg->vmstats_percpu, cpu);
                statc->parent = parent ? pstatc : NULL;
                statc->vmstats = memcg->vmstats;
        }

        for_each_node(node)
                if (!alloc_mem_cgroup_per_node_info(memcg, node))
                        goto fail;

        if (memcg_wb_domain_init(memcg, GFP_KERNEL))
                goto fail;

        INIT_WORK(&memcg->high_work, high_work_func);
        vmpressure_init(&memcg->vmpressure);
        INIT_LIST_HEAD(&memcg->memory_peaks);
        INIT_LIST_HEAD(&memcg->swap_peaks);
        spin_lock_init(&memcg->peaks_lock);
        memcg->socket_pressure = jiffies;
        memcg1_memcg_init(memcg);
        memcg->kmemcg_id = -1;
        INIT_LIST_HEAD(&memcg->objcg_list);
#ifdef CONFIG_CGROUP_WRITEBACK
        INIT_LIST_HEAD(&memcg->cgwb_list);
        for (i = 0; i < MEMCG_CGWB_FRN_CNT; i++)
                memcg->cgwb_frn[i].done =
                        __WB_COMPLETION_INIT(&memcg_cgwb_frn_waitq);
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
        spin_lock_init(&memcg->deferred_split_queue.split_queue_lock);
        INIT_LIST_HEAD(&memcg->deferred_split_queue.split_queue);
        memcg->deferred_split_queue.split_queue_len = 0;
#endif
        lru_gen_init_memcg(memcg);
        return memcg;
fail:
        mem_cgroup_id_remove(memcg);
        __mem_cgroup_free(memcg);
        return ERR_PTR(error);
}

static struct cgroup_subsys_state * __ref
mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
{
        struct mem_cgroup *parent = mem_cgroup_from_css(parent_css);
        struct mem_cgroup *memcg, *old_memcg;

        old_memcg = set_active_memcg(parent);
        memcg = mem_cgroup_alloc(parent);
        set_active_memcg(old_memcg);
        if (IS_ERR(memcg))
                return ERR_CAST(memcg);

        page_counter_set_high(&memcg->memory, PAGE_COUNTER_MAX);
        memcg1_soft_limit_reset(memcg);
#ifdef CONFIG_ZSWAP
        memcg->zswap_max = PAGE_COUNTER_MAX;
        WRITE_ONCE(memcg->zswap_writeback, true);
#endif
        page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
        if (parent) {
                WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));

                page_counter_init(&memcg->memory, &parent->memory, true);
                page_counter_init(&memcg->swap, &parent->swap, false);
#ifdef CONFIG_MEMCG_V1
                WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable));
                page_counter_init(&memcg->kmem, &parent->kmem, false);
                page_counter_init(&memcg->tcpmem, &parent->tcpmem, false);
#endif
        } else {
                init_memcg_stats();
                init_memcg_events();
                page_counter_init(&memcg->memory, NULL, true);
                page_counter_init(&memcg->swap, NULL, false);
#ifdef CONFIG_MEMCG_V1
                page_counter_init(&memcg->kmem, NULL, false);
                page_counter_init(&memcg->tcpmem, NULL, false);
#endif
                root_mem_cgroup = memcg;
                return &memcg->css;
        }

        if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
                static_branch_inc(&memcg_sockets_enabled_key);

        if (!cgroup_memory_nobpf)
                static_branch_inc(&memcg_bpf_enabled_key);

        return &memcg->css;
}

static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);

        if (memcg_online_kmem(memcg))
                goto remove_id;

        /*
         * A memcg must be visible for expand_shrinker_info()
         * by the time the maps are allocated. So, we allocate maps
         * here, when for_each_mem_cgroup() can't skip it.
         */
        if (alloc_shrinker_info(memcg))
                goto offline_kmem;

        if (unlikely(mem_cgroup_is_root(memcg)) && !mem_cgroup_disabled())
                queue_delayed_work(system_unbound_wq, &stats_flush_dwork,
                                   FLUSH_TIME);
        lru_gen_online_memcg(memcg);

        /* Online state pins memcg ID, memcg ID pins CSS */
        refcount_set(&memcg->id.ref, 1);
        css_get(css);

        /*
         * Ensure mem_cgroup_from_id() works once we're fully online.
         *
         * We could do this earlier and require callers to filter with
         * css_tryget_online(). But right now there are no users that
         * need earlier access, and the workingset code relies on the
         * cgroup tree linkage (mem_cgroup_get_nr_swap_pages()). So
         * publish it here at the end of onlining. This matches the
         * regular ID destruction during offlining.
         */
        xa_store(&mem_cgroup_ids, memcg->id.id, memcg, GFP_KERNEL);

        return 0;
offline_kmem:
        memcg_offline_kmem(memcg);
remove_id:
        mem_cgroup_id_remove(memcg);
        return -ENOMEM;
}

static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);

        memcg1_css_offline(memcg);

        page_counter_set_min(&memcg->memory, 0);
        page_counter_set_low(&memcg->memory, 0);

        zswap_memcg_offline_cleanup(memcg);

        memcg_offline_kmem(memcg);
        reparent_shrinker_deferred(memcg);
        wb_memcg_offline(memcg);
        lru_gen_offline_memcg(memcg);

        drain_all_stock(memcg);

        mem_cgroup_id_put(memcg);
}

static void mem_cgroup_css_released(struct cgroup_subsys_state *css)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);

        invalidate_reclaim_iterators(memcg);
        lru_gen_release_memcg(memcg);
}

static void mem_cgroup_css_free(struct cgroup_subsys_state *css)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);
        int __maybe_unused i;

#ifdef CONFIG_CGROUP_WRITEBACK
        for (i = 0; i < MEMCG_CGWB_FRN_CNT; i++)
                wb_wait_for_completion(&memcg->cgwb_frn[i].done);
#endif
        if (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nosocket)
                static_branch_dec(&memcg_sockets_enabled_key);

        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && memcg1_tcpmem_active(memcg))
                static_branch_dec(&memcg_sockets_enabled_key);

        if (!cgroup_memory_nobpf)
                static_branch_dec(&memcg_bpf_enabled_key);

        vmpressure_cleanup(&memcg->vmpressure);
        cancel_work_sync(&memcg->high_work);
        memcg1_remove_from_trees(memcg);
        free_shrinker_info(memcg);
        mem_cgroup_free(memcg);
}

/**
 * mem_cgroup_css_reset - reset the states of a mem_cgroup
 * @css: the target css
 *
 * Reset the states of the mem_cgroup associated with @css.  This is
 * invoked when the userland requests disabling on the default hierarchy
 * but the memcg is pinned through dependency.  The memcg should stop
 * applying policies and should revert to the vanilla state as it may be
 * made visible again.
 *
 * The current implementation only resets the essential configurations.
 * This needs to be expanded to cover all the visible parts.
 */
static void mem_cgroup_css_reset(struct cgroup_subsys_state *css)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);

        page_counter_set_max(&memcg->memory, PAGE_COUNTER_MAX);
        page_counter_set_max(&memcg->swap, PAGE_COUNTER_MAX);
#ifdef CONFIG_MEMCG_V1
        page_counter_set_max(&memcg->kmem, PAGE_COUNTER_MAX);
        page_counter_set_max(&memcg->tcpmem, PAGE_COUNTER_MAX);
#endif
        page_counter_set_min(&memcg->memory, 0);
        page_counter_set_low(&memcg->memory, 0);
        page_counter_set_high(&memcg->memory, PAGE_COUNTER_MAX);
        memcg1_soft_limit_reset(memcg);
        page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
        memcg_wb_domain_size_changed(memcg);
}

struct aggregate_control {
        /* pointer to the aggregated (CPU and subtree aggregated) counters */
        long *aggregate;
        /* pointer to the non-hierarchichal (CPU aggregated) counters */
        long *local;
        /* pointer to the pending child counters during tree propagation */
        long *pending;
        /* pointer to the parent's pending counters, could be NULL */
        long *ppending;
        /* pointer to the percpu counters to be aggregated */
        long *cstat;
        /* pointer to the percpu counters of the last aggregation*/
        long *cstat_prev;
        /* size of the above counters */
        int size;
};

static void mem_cgroup_stat_aggregate(struct aggregate_control *ac)
{
        int i;
        long delta, delta_cpu, v;

        for (i = 0; i < ac->size; i++) {
                /*
                 * Collect the aggregated propagation counts of groups
                 * below us. We're in a per-cpu loop here and this is
                 * a global counter, so the first cycle will get them.
                 */
                delta = ac->pending[i];
                if (delta)
                        ac->pending[i] = 0;

                /* Add CPU changes on this level since the last flush */
                delta_cpu = 0;
                v = READ_ONCE(ac->cstat[i]);
                if (v != ac->cstat_prev[i]) {
                        delta_cpu = v - ac->cstat_prev[i];
                        delta += delta_cpu;
                        ac->cstat_prev[i] = v;
                }

                /* Aggregate counts on this level and propagate upwards */
                if (delta_cpu)
                        ac->local[i] += delta_cpu;

                if (delta) {
                        ac->aggregate[i] += delta;
                        if (ac->ppending)
                                ac->ppending[i] += delta;
                }
        }
}

static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);
        struct mem_cgroup *parent = parent_mem_cgroup(memcg);
        struct memcg_vmstats_percpu *statc;
        struct aggregate_control ac;
        int nid;

        statc = per_cpu_ptr(memcg->vmstats_percpu, cpu);

        ac = (struct aggregate_control) {
                .aggregate = memcg->vmstats->state,
                .local = memcg->vmstats->state_local,
                .pending = memcg->vmstats->state_pending,
                .ppending = parent ? parent->vmstats->state_pending : NULL,
                .cstat = statc->state,
                .cstat_prev = statc->state_prev,
                .size = MEMCG_VMSTAT_SIZE,
        };
        mem_cgroup_stat_aggregate(&ac);

        ac = (struct aggregate_control) {
                .aggregate = memcg->vmstats->events,
                .local = memcg->vmstats->events_local,
                .pending = memcg->vmstats->events_pending,
                .ppending = parent ? parent->vmstats->events_pending : NULL,
                .cstat = statc->events,
                .cstat_prev = statc->events_prev,
                .size = NR_MEMCG_EVENTS,
        };
        mem_cgroup_stat_aggregate(&ac);

        for_each_node_state(nid, N_MEMORY) {
                struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid];
                struct lruvec_stats *lstats = pn->lruvec_stats;
                struct lruvec_stats *plstats = NULL;
                struct lruvec_stats_percpu *lstatc;

                if (parent)
                        plstats = parent->nodeinfo[nid]->lruvec_stats;

                lstatc = per_cpu_ptr(pn->lruvec_stats_percpu, cpu);

                ac = (struct aggregate_control) {
                        .aggregate = lstats->state,
                        .local = lstats->state_local,
                        .pending = lstats->state_pending,
                        .ppending = plstats ? plstats->state_pending : NULL,
                        .cstat = lstatc->state,
                        .cstat_prev = lstatc->state_prev,
                        .size = NR_MEMCG_NODE_STAT_ITEMS,
                };
                mem_cgroup_stat_aggregate(&ac);

        }
        WRITE_ONCE(statc->stats_updates, 0);
        /* We are in a per-cpu loop here, only do the atomic write once */
        if (atomic64_read(&memcg->vmstats->stats_updates))
                atomic64_set(&memcg->vmstats->stats_updates, 0);
}

static void mem_cgroup_fork(struct task_struct *task)
{
        /*
         * Set the update flag to cause task->objcg to be initialized lazily
         * on the first allocation. It can be done without any synchronization
         * because it's always performed on the current task, so does
         * current_objcg_update().
         */
        task->objcg = (struct obj_cgroup *)CURRENT_OBJCG_UPDATE_FLAG;
}

static void mem_cgroup_exit(struct task_struct *task)
{
        struct obj_cgroup *objcg = task->objcg;

        objcg = (struct obj_cgroup *)
                ((unsigned long)objcg & ~CURRENT_OBJCG_UPDATE_FLAG);
        obj_cgroup_put(objcg);

        /*
         * Some kernel allocations can happen after this point,
         * but let's ignore them. It can be done without any synchronization
         * because it's always performed on the current task, so does
         * current_objcg_update().
         */
        task->objcg = NULL;
}

#ifdef CONFIG_LRU_GEN
static void mem_cgroup_lru_gen_attach(struct cgroup_taskset *tset)
{
        struct task_struct *task;
        struct cgroup_subsys_state *css;

        /* find the first leader if there is any */
        cgroup_taskset_for_each_leader(task, css, tset)
                break;

        if (!task)
                return;

        task_lock(task);
        if (task->mm && READ_ONCE(task->mm->owner) == task)
                lru_gen_migrate_mm(task->mm);
        task_unlock(task);
}
#else
static void mem_cgroup_lru_gen_attach(struct cgroup_taskset *tset) {}
#endif /* CONFIG_LRU_GEN */

static void mem_cgroup_kmem_attach(struct cgroup_taskset *tset)
{
        struct task_struct *task;
        struct cgroup_subsys_state *css;

        cgroup_taskset_for_each(task, css, tset) {
                /* atomically set the update bit */
                set_bit(CURRENT_OBJCG_UPDATE_BIT, (unsigned long *)&task->objcg);
        }
}

static void mem_cgroup_attach(struct cgroup_taskset *tset)
{
        mem_cgroup_lru_gen_attach(tset);
        mem_cgroup_kmem_attach(tset);
}

static int seq_puts_memcg_tunable(struct seq_file *m, unsigned long value)
{
        if (value == PAGE_COUNTER_MAX)
                seq_puts(m, "max\n");
        else
                seq_printf(m, "%llu\n", (u64)value * PAGE_SIZE);

        return 0;
}

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

        return (u64)page_counter_read(&memcg->memory) * PAGE_SIZE;
}

#define OFP_PEAK_UNSET (((-1UL)))

static int peak_show(struct seq_file *sf, void *v, struct page_counter *pc)
{
        struct cgroup_of_peak *ofp = of_peak(sf->private);
        u64 fd_peak = READ_ONCE(ofp->value), peak;

        /* User wants global or local peak? */
        if (fd_peak == OFP_PEAK_UNSET)
                peak = pc->watermark;
        else
                peak = max(fd_peak, READ_ONCE(pc->local_watermark));

        seq_printf(sf, "%llu\n", peak * PAGE_SIZE);
        return 0;
}

static int memory_peak_show(struct seq_file *sf, void *v)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(sf));

        return peak_show(sf, v, &memcg->memory);
}

static int peak_open(struct kernfs_open_file *of)
{
        struct cgroup_of_peak *ofp = of_peak(of);

        ofp->value = OFP_PEAK_UNSET;
        return 0;
}

static void peak_release(struct kernfs_open_file *of)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
        struct cgroup_of_peak *ofp = of_peak(of);

        if (ofp->value == OFP_PEAK_UNSET) {
                /* fast path (no writes on this fd) */
                return;
        }
        spin_lock(&memcg->peaks_lock);
        list_del(&ofp->list);
        spin_unlock(&memcg->peaks_lock);
}

static ssize_t peak_write(struct kernfs_open_file *of, char *buf, size_t nbytes,
                          loff_t off, struct page_counter *pc,
                          struct list_head *watchers)
{
        unsigned long usage;
        struct cgroup_of_peak *peer_ctx;
        struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
        struct cgroup_of_peak *ofp = of_peak(of);

        spin_lock(&memcg->peaks_lock);

        usage = page_counter_read(pc);
        WRITE_ONCE(pc->local_watermark, usage);

        list_for_each_entry(peer_ctx, watchers, list)
                if (usage > peer_ctx->value)
                        WRITE_ONCE(peer_ctx->value, usage);

        /* initial write, register watcher */
        if (ofp->value == -1)
                list_add(&ofp->list, watchers);

        WRITE_ONCE(ofp->value, usage);
        spin_unlock(&memcg->peaks_lock);

        return nbytes;
}

static ssize_t memory_peak_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));

        return peak_write(of, buf, nbytes, off, &memcg->memory,
                          &memcg->memory_peaks);
}

#undef OFP_PEAK_UNSET

static int memory_min_show(struct seq_file *m, void *v)
{
        return seq_puts_memcg_tunable(m,
                READ_ONCE(mem_cgroup_from_seq(m)->memory.min));
}

static ssize_t memory_min_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 min;
        int err;

        buf = strstrip(buf);
        err = page_counter_memparse(buf, "max", &min);
        if (err)
                return err;

        page_counter_set_min(&memcg->memory, min);

        return nbytes;
}

static int memory_low_show(struct seq_file *m, void *v)
{
        return seq_puts_memcg_tunable(m,
                READ_ONCE(mem_cgroup_from_seq(m)->memory.low));
}

static ssize_t memory_low_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 low;
        int err;

        buf = strstrip(buf);
        err = page_counter_memparse(buf, "max", &low);
        if (err)
                return err;

        page_counter_set_low(&memcg->memory, low);

        return nbytes;
}

static int memory_high_show(struct seq_file *m, void *v)
{
        return seq_puts_memcg_tunable(m,
                READ_ONCE(mem_cgroup_from_seq(m)->memory.high));
}

static ssize_t memory_high_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 int nr_retries = MAX_RECLAIM_RETRIES;
        bool drained = false;
        unsigned long high;
        int err;

        buf = strstrip(buf);
        err = page_counter_memparse(buf, "max", &high);
        if (err)
                return err;

        page_counter_set_high(&memcg->memory, high);

        for (;;) {
                unsigned long nr_pages = page_counter_read(&memcg->memory);
                unsigned long reclaimed;

                if (nr_pages <= high)
                        break;

                if (signal_pending(current))
                        break;

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

                reclaimed = try_to_free_mem_cgroup_pages(memcg, nr_pages - high,
                                        GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP, NULL);

                if (!reclaimed && !nr_retries--)
                        break;
        }

        memcg_wb_domain_size_changed(memcg);
        return nbytes;
}

static int memory_max_show(struct seq_file *m, void *v)
{
        return seq_puts_memcg_tunable(m,
                READ_ONCE(mem_cgroup_from_seq(m)->memory.max));
}

static ssize_t memory_max_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 int nr_reclaims = MAX_RECLAIM_RETRIES;
        bool drained = false;
        unsigned long max;
        int err;

        buf = strstrip(buf);
        err = page_counter_memparse(buf, "max", &max);
        if (err)
                return err;

        xchg(&memcg->memory.max, max);

        for (;;) {
                unsigned long nr_pages = page_counter_read(&memcg->memory);

                if (nr_pages <= max)
                        break;

                if (signal_pending(current))
                        break;

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

                if (nr_reclaims) {
                        if (!try_to_free_mem_cgroup_pages(memcg, nr_pages - max,
                                        GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP, NULL))
                                nr_reclaims--;
                        continue;
                }

                memcg_memory_event(memcg, MEMCG_OOM);
                if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0))
                        break;
        }

        memcg_wb_domain_size_changed(memcg);
        return nbytes;
}

/*
 * Note: don't forget to update the 'samples/cgroup/memcg_event_listener'
 * if any new events become available.
 */
static void __memory_events_show(struct seq_file *m, atomic_long_t *events)
{
        seq_printf(m, "low %lu\n", atomic_long_read(&events[MEMCG_LOW]));
        seq_printf(m, "high %lu\n", atomic_long_read(&events[MEMCG_HIGH]));
        seq_printf(m, "max %lu\n", atomic_long_read(&events[MEMCG_MAX]));
        seq_printf(m, "oom %lu\n", atomic_long_read(&events[MEMCG_OOM]));
        seq_printf(m, "oom_kill %lu\n",
                   atomic_long_read(&events[MEMCG_OOM_KILL]));
        seq_printf(m, "oom_group_kill %lu\n",
                   atomic_long_read(&events[MEMCG_OOM_GROUP_KILL]));
}

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

        __memory_events_show(m, memcg->memory_events);
        return 0;
}

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

        __memory_events_show(m, memcg->memory_events_local);
        return 0;
}

int memory_stat_show(struct seq_file *m, void *v)
{
        struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
        char *buf = kmalloc(SEQ_BUF_SIZE, GFP_KERNEL);
        struct seq_buf s;

        if (!buf)
                return -ENOMEM;
        seq_buf_init(&s, buf, SEQ_BUF_SIZE);
        memory_stat_format(memcg, &s);
        seq_puts(m, buf);
        kfree(buf);
        return 0;
}

#ifdef CONFIG_NUMA
static inline unsigned long lruvec_page_state_output(struct lruvec *lruvec,
                                                     int item)
{
        return lruvec_page_state(lruvec, item) *
                memcg_page_state_output_unit(item);
}

static int memory_numa_stat_show(struct seq_file *m, void *v)
{
        int i;
        struct mem_cgroup *memcg = mem_cgroup_from_seq(m);

        mem_cgroup_flush_stats(memcg);

        for (i = 0; i < ARRAY_SIZE(memory_stats); i++) {
                int nid;

                if (memory_stats[i].idx >= NR_VM_NODE_STAT_ITEMS)
                        continue;

                seq_printf(m, "%s", memory_stats[i].name);
                for_each_node_state(nid, N_MEMORY) {
                        u64 size;
                        struct lruvec *lruvec;

                        lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(nid));
                        size = lruvec_page_state_output(lruvec,
                                                        memory_stats[i].idx);
                        seq_printf(m, " N%d=%llu", nid, size);
                }
                seq_putc(m, '\n');
        }

        return 0;
}
#endif

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

        seq_printf(m, "%d\n", READ_ONCE(memcg->oom_group));

        return 0;
}

static ssize_t memory_oom_group_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));
        int ret, oom_group;

        buf = strstrip(buf);
        if (!buf)
                return -EINVAL;

        ret = kstrtoint(buf, 0, &oom_group);
        if (ret)
                return ret;

        if (oom_group != 0 && oom_group != 1)
                return -EINVAL;

        WRITE_ONCE(memcg->oom_group, oom_group);

        return nbytes;
}

enum {
        MEMORY_RECLAIM_SWAPPINESS = 0,
        MEMORY_RECLAIM_NULL,
};

static const match_table_t tokens = {
        { MEMORY_RECLAIM_SWAPPINESS, "swappiness=%d"},
        { MEMORY_RECLAIM_NULL, NULL },
};

static ssize_t memory_reclaim(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 int nr_retries = MAX_RECLAIM_RETRIES;
        unsigned long nr_to_reclaim, nr_reclaimed = 0;
        int swappiness = -1;
        unsigned int reclaim_options;
        char *old_buf, *start;
        substring_t args[MAX_OPT_ARGS];

        buf = strstrip(buf);

        old_buf = buf;
        nr_to_reclaim = memparse(buf, &buf) / PAGE_SIZE;
        if (buf == old_buf)
                return -EINVAL;

        buf = strstrip(buf);

        while ((start = strsep(&buf, " ")) != NULL) {
                if (!strlen(start))
                        continue;
                switch (match_token(start, tokens, args)) {
                case MEMORY_RECLAIM_SWAPPINESS:
                        if (match_int(&args[0], &swappiness))
                                return -EINVAL;
                        if (swappiness < MIN_SWAPPINESS || swappiness > MAX_SWAPPINESS)
                                return -EINVAL;
                        break;
                default:
                        return -EINVAL;
                }
        }

        reclaim_options = MEMCG_RECLAIM_MAY_SWAP | MEMCG_RECLAIM_PROACTIVE;
        while (nr_reclaimed < nr_to_reclaim) {
                /* Will converge on zero, but reclaim enforces a minimum */
                unsigned long batch_size = (nr_to_reclaim - nr_reclaimed) / 4;
                unsigned long reclaimed;

                if (signal_pending(current))
                        return -EINTR;

                /*
                 * This is the final attempt, drain percpu lru caches in the
                 * hope of introducing more evictable pages for
                 * try_to_free_mem_cgroup_pages().
                 */
                if (!nr_retries)
                        lru_add_drain_all();

                reclaimed = try_to_free_mem_cgroup_pages(memcg,
                                        batch_size, GFP_KERNEL,
                                        reclaim_options,
                                        swappiness == -1 ? NULL : &swappiness);

                if (!reclaimed && !nr_retries--)
                        return -EAGAIN;

                nr_reclaimed += reclaimed;
        }

        return nbytes;
}

static struct cftype memory_files[] = {
        {
                .name = "current",
                .flags = CFTYPE_NOT_ON_ROOT,
                .read_u64 = memory_current_read,
        },
        {
                .name = "peak",
                .flags = CFTYPE_NOT_ON_ROOT,
                .open = peak_open,
                .release = peak_release,
                .seq_show = memory_peak_show,
                .write = memory_peak_write,
        },
        {
                .name = "min",
                .flags = CFTYPE_NOT_ON_ROOT,
                .seq_show = memory_min_show,
                .write = memory_min_write,
        },
        {
                .name = "low",
                .flags = CFTYPE_NOT_ON_ROOT,
                .seq_show = memory_low_show,
                .write = memory_low_write,
        },
        {
                .name = "high",
                .flags = CFTYPE_NOT_ON_ROOT,
                .seq_show = memory_high_show,
                .write = memory_high_write,
        },
        {
                .name = "max",
                .flags = CFTYPE_NOT_ON_ROOT,
                .seq_show = memory_max_show,
                .write = memory_max_write,
        },
        {
                .name = "events",
                .flags = CFTYPE_NOT_ON_ROOT,
                .file_offset = offsetof(struct mem_cgroup, events_file),
                .seq_show = memory_events_show,
        },
        {
                .name = "events.local",
                .flags = CFTYPE_NOT_ON_ROOT,
                .file_offset = offsetof(struct mem_cgroup, events_local_file),
                .seq_show = memory_events_local_show,
        },
        {
                .name = "stat",
                .seq_show = memory_stat_show,
        },
#ifdef CONFIG_NUMA
        {
                .name = "numa_stat",
                .seq_show = memory_numa_stat_show,
        },
#endif
        {
                .name = "oom.group",
                .flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE,
                .seq_show = memory_oom_group_show,
                .write = memory_oom_group_write,
        },
        {
                .name = "reclaim",
                .flags = CFTYPE_NS_DELEGATABLE,
                .write = memory_reclaim,
        },
        { }     /* terminate */
};

struct cgroup_subsys memory_cgrp_subsys = {
        .css_alloc = mem_cgroup_css_alloc,
        .css_online = mem_cgroup_css_online,
        .css_offline = mem_cgroup_css_offline,
        .css_released = mem_cgroup_css_released,
        .css_free = mem_cgroup_css_free,
        .css_reset = mem_cgroup_css_reset,
        .css_rstat_flush = mem_cgroup_css_rstat_flush,
        .attach = mem_cgroup_attach,
        .fork = mem_cgroup_fork,
        .exit = mem_cgroup_exit,
        .dfl_cftypes = memory_files,
#ifdef CONFIG_MEMCG_V1
        .legacy_cftypes = mem_cgroup_legacy_files,
#endif
        .early_init = 0,
};

/**
 * mem_cgroup_calculate_protection - check if memory consumption is in the normal range
 * @root: the top ancestor of the sub-tree being checked
 * @memcg: the memory cgroup to check
 *
 * WARNING: This function is not stateless! It can only be used as part
 *          of a top-down tree iteration, not for isolated queries.
 */
void mem_cgroup_calculate_protection(struct mem_cgroup *root,
                                     struct mem_cgroup *memcg)
{
        bool recursive_protection =
                cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT;

        if (mem_cgroup_disabled())
                return;

        if (!root)
                root = root_mem_cgroup;

        page_counter_calculate_protection(&root->memory, &memcg->memory, recursive_protection);
}

static int charge_memcg(struct folio *folio, struct mem_cgroup *memcg,
                        gfp_t gfp)
{
        int ret;

        ret = try_charge(memcg, gfp, folio_nr_pages(folio));
        if (ret)
                goto out;

        mem_cgroup_commit_charge(folio, memcg);
out:
        return ret;
}

int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp)
{
        struct mem_cgroup *memcg;
        int ret;

        memcg = get_mem_cgroup_from_mm(mm);
        ret = charge_memcg(folio, memcg, gfp);
        css_put(&memcg->css);

        return ret;
}

/**
 * mem_cgroup_hugetlb_try_charge - try to charge the memcg for a hugetlb folio
 * @memcg: memcg to charge.
 * @gfp: reclaim mode.
 * @nr_pages: number of pages to charge.
 *
 * This function is called when allocating a huge page folio to determine if
 * the memcg has the capacity for it. It does not commit the charge yet,
 * as the hugetlb folio itself has not been obtained from the hugetlb pool.
 *
 * Once we have obtained the hugetlb folio, we can call
 * mem_cgroup_commit_charge() to commit the charge. If we fail to obtain the
 * folio, we should instead call mem_cgroup_cancel_charge() to undo the effect
 * of try_charge().
 *
 * Returns 0 on success. Otherwise, an error code is returned.
 */
int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
                        long nr_pages)
{
        /*
         * If hugetlb memcg charging is not enabled, do not fail hugetlb allocation,
         * but do not attempt to commit charge later (or cancel on error) either.
         */
        if (mem_cgroup_disabled() || !memcg ||
                !cgroup_subsys_on_dfl(memory_cgrp_subsys) ||
                !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
                return -EOPNOTSUPP;

        if (try_charge(memcg, gfp, nr_pages))
                return -ENOMEM;

        return 0;
}

/**
 * mem_cgroup_swapin_charge_folio - Charge a newly allocated folio for swapin.
 * @folio: folio to charge.
 * @mm: mm context of the victim
 * @gfp: reclaim mode
 * @entry: swap entry for which the folio is allocated
 *
 * This function charges a folio allocated for swapin. Please call this before
 * adding the folio to the swapcache.
 *
 * Returns 0 on success. Otherwise, an error code is returned.
 */
int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,
                                  gfp_t gfp, swp_entry_t entry)
{
        struct mem_cgroup *memcg;
        unsigned short id;
        int ret;

        if (mem_cgroup_disabled())
                return 0;

        id = lookup_swap_cgroup_id(entry);
        rcu_read_lock();
        memcg = mem_cgroup_from_id(id);
        if (!memcg || !css_tryget_online(&memcg->css))
                memcg = get_mem_cgroup_from_mm(mm);
        rcu_read_unlock();

        ret = charge_memcg(folio, memcg, gfp);

        css_put(&memcg->css);
        return ret;
}

/*
 * mem_cgroup_swapin_uncharge_swap - 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 mem_cgroup_swapin_uncharge_swap(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 (!mem_cgroup_disabled() && 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);
        }
}

struct uncharge_gather {
        struct mem_cgroup *memcg;
        unsigned long nr_memory;
        unsigned long pgpgout;
        unsigned long nr_kmem;
        int nid;
};

static inline void uncharge_gather_clear(struct uncharge_gather *ug)
{
        memset(ug, 0, sizeof(*ug));
}

static void uncharge_batch(const struct uncharge_gather *ug)
{
        if (ug->nr_memory) {
                page_counter_uncharge(&ug->memcg->memory, ug->nr_memory);
                if (do_memsw_account())
                        page_counter_uncharge(&ug->memcg->memsw, ug->nr_memory);
                if (ug->nr_kmem) {
                        mod_memcg_state(ug->memcg, MEMCG_KMEM, -ug->nr_kmem);
                        memcg1_account_kmem(ug->memcg, -ug->nr_kmem);
                }
                memcg1_oom_recover(ug->memcg);
        }

        memcg1_uncharge_batch(ug->memcg, ug->pgpgout, ug->nr_memory, ug->nid);

        /* drop reference from uncharge_folio */
        css_put(&ug->memcg->css);
}

static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)
{
        long nr_pages;
        struct mem_cgroup *memcg;
        struct obj_cgroup *objcg;

        VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);

        /*
         * Nobody should be changing or seriously looking at
         * folio memcg or objcg at this point, we have fully
         * exclusive access to the folio.
         */
        if (folio_memcg_kmem(folio)) {
                objcg = __folio_objcg(folio);
                /*
                 * This get matches the put at the end of the function and
                 * kmem pages do not hold memcg references anymore.
                 */
                memcg = get_mem_cgroup_from_objcg(objcg);
        } else {
                memcg = __folio_memcg(folio);
        }

        if (!memcg)
                return;

        if (ug->memcg != memcg) {
                if (ug->memcg) {
                        uncharge_batch(ug);
                        uncharge_gather_clear(ug);
                }
                ug->memcg = memcg;
                ug->nid = folio_nid(folio);

                /* pairs with css_put in uncharge_batch */
                css_get(&memcg->css);
        }

        nr_pages = folio_nr_pages(folio);

        if (folio_memcg_kmem(folio)) {
                ug->nr_memory += nr_pages;
                ug->nr_kmem += nr_pages;

                folio->memcg_data = 0;
                obj_cgroup_put(objcg);
        } else {
                /* LRU pages aren't accounted at the root level */
                if (!mem_cgroup_is_root(memcg))
                        ug->nr_memory += nr_pages;
                ug->pgpgout++;

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

        css_put(&memcg->css);
}

void __mem_cgroup_uncharge(struct folio *folio)
{
        struct uncharge_gather ug;

        /* Don't touch folio->lru of any random page, pre-check: */
        if (!folio_memcg_charged(folio))
                return;

        uncharge_gather_clear(&ug);
        uncharge_folio(folio, &ug);
        uncharge_batch(&ug);
}

void __mem_cgroup_uncharge_folios(struct folio_batch *folios)
{
        struct uncharge_gather ug;
        unsigned int i;

        uncharge_gather_clear(&ug);
        for (i = 0; i < folios->nr; i++)
                uncharge_folio(folios->folios[i], &ug);
        if (ug.memcg)
                uncharge_batch(&ug);
}

/**
 * mem_cgroup_replace_folio - Charge a folio's replacement.
 * @old: Currently circulating folio.
 * @new: Replacement folio.
 *
 * Charge @new as a replacement folio for @old. @old will
 * be uncharged upon free.
 *
 * Both folios must be locked, @new->mapping must be set up.
 */
void mem_cgroup_replace_folio(struct folio *old, struct folio *new)
{
        struct mem_cgroup *memcg;
        long nr_pages = folio_nr_pages(new);

        VM_BUG_ON_FOLIO(!folio_test_locked(old), old);
        VM_BUG_ON_FOLIO(!folio_test_locked(new), new);
        VM_BUG_ON_FOLIO(folio_test_anon(old) != folio_test_anon(new), new);
        VM_BUG_ON_FOLIO(folio_nr_pages(old) != nr_pages, new);

        if (mem_cgroup_disabled())
                return;

        /* Page cache replacement: new folio already charged? */
        if (folio_memcg_charged(new))
                return;

        memcg = folio_memcg(old);
        VM_WARN_ON_ONCE_FOLIO(!memcg, old);
        if (!memcg)
                return;

        /* Force-charge the new page. The old one will be freed soon */
        if (!mem_cgroup_is_root(memcg)) {
                page_counter_charge(&memcg->memory, nr_pages);
                if (do_memsw_account())
                        page_counter_charge(&memcg->memsw, nr_pages);
        }

        css_get(&memcg->css);
        commit_charge(new, memcg);
        memcg1_commit_charge(new, memcg);
}

/**
 * mem_cgroup_migrate - Transfer the memcg data from the old to the new folio.
 * @old: Currently circulating folio.
 * @new: Replacement folio.
 *
 * Transfer the memcg data from the old folio to the new folio for migration.
 * The old folio's data info will be cleared. Note that the memory counters
 * will remain unchanged throughout the process.
 *
 * Both folios must be locked, @new->mapping must be set up.
 */
void mem_cgroup_migrate(struct folio *old, struct folio *new)
{
        struct mem_cgroup *memcg;

        VM_BUG_ON_FOLIO(!folio_test_locked(old), old);
        VM_BUG_ON_FOLIO(!folio_test_locked(new), new);
        VM_BUG_ON_FOLIO(folio_test_anon(old) != folio_test_anon(new), new);
        VM_BUG_ON_FOLIO(folio_nr_pages(old) != folio_nr_pages(new), new);
        VM_BUG_ON_FOLIO(folio_test_lru(old), old);

        if (mem_cgroup_disabled())
                return;

        memcg = folio_memcg(old);
        /*
         * Note that it is normal to see !memcg for a hugetlb folio.
         * For e.g, itt could have been allocated when memory_hugetlb_accounting
         * was not selected.
         */
        VM_WARN_ON_ONCE_FOLIO(!folio_test_hugetlb(old) && !memcg, old);
        if (!memcg)
                return;

        /* Transfer the charge and the css ref */
        commit_charge(new, memcg);

        /* Warning should never happen, so don't worry about refcount non-0 */
        WARN_ON_ONCE(folio_unqueue_deferred_split(old));
        old->memcg_data = 0;
}

DEFINE_STATIC_KEY_FALSE(memcg_sockets_enabled_key);
EXPORT_SYMBOL(memcg_sockets_enabled_key);

void mem_cgroup_sk_alloc(struct sock *sk)
{
        struct mem_cgroup *memcg;

        if (!mem_cgroup_sockets_enabled)
                return;

        /* Do not associate the sock with unrelated interrupted task's memcg. */
        if (!in_task())
                return;

        rcu_read_lock();
        memcg = mem_cgroup_from_task(current);
        if (mem_cgroup_is_root(memcg))
                goto out;
        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !memcg1_tcpmem_active(memcg))
                goto out;
        if (css_tryget(&memcg->css))
                sk->sk_memcg = memcg;
out:
        rcu_read_unlock();
}

void mem_cgroup_sk_free(struct sock *sk)
{
        if (sk->sk_memcg)
                css_put(&sk->sk_memcg->css);
}

/**
 * mem_cgroup_charge_skmem - charge socket memory
 * @memcg: memcg to charge
 * @nr_pages: number of pages to charge
 * @gfp_mask: reclaim mode
 *
 * Charges @nr_pages to @memcg. Returns %true if the charge fit within
 * @memcg's configured limit, %false if it doesn't.
 */
bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages,
                             gfp_t gfp_mask)
{
        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
                return memcg1_charge_skmem(memcg, nr_pages, gfp_mask);

        if (try_charge(memcg, gfp_mask, nr_pages) == 0) {
                mod_memcg_state(memcg, MEMCG_SOCK, nr_pages);
                return true;
        }

        return false;
}

/**
 * mem_cgroup_uncharge_skmem - uncharge socket memory
 * @memcg: memcg to uncharge
 * @nr_pages: number of pages to uncharge
 */
void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
{
        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
                memcg1_uncharge_skmem(memcg, nr_pages);
                return;
        }

        mod_memcg_state(memcg, MEMCG_SOCK, -nr_pages);

        refill_stock(memcg, nr_pages);
}

static int __init cgroup_memory(char *s)
{
        char *token;

        while ((token = strsep(&s, ",")) != NULL) {
                if (!*token)
                        continue;
                if (!strcmp(token, "nosocket"))
                        cgroup_memory_nosocket = true;
                if (!strcmp(token, "nokmem"))
                        cgroup_memory_nokmem = true;
                if (!strcmp(token, "nobpf"))
                        cgroup_memory_nobpf = true;
        }
        return 1;
}
__setup("cgroup.memory=", cgroup_memory);

/*
 * subsys_initcall() for memory controller.
 *
 * Some parts like memcg_hotplug_cpu_dead() have to be initialized from this
 * context because of lock dependencies (cgroup_lock -> cpu hotplug) but
 * basically everything that doesn't depend on a specific mem_cgroup structure
 * should be initialized from here.
 */
static int __init mem_cgroup_init(void)
{
        int cpu;

        /*
         * Currently s32 type (can refer to struct batched_lruvec_stat) is
         * used for per-memcg-per-cpu caching of per-node statistics. In order
         * to work fine, we should make sure that the overfill threshold can't
         * exceed S32_MAX / PAGE_SIZE.
         */
        BUILD_BUG_ON(MEMCG_CHARGE_BATCH > S32_MAX / PAGE_SIZE);

        cpuhp_setup_state_nocalls(CPUHP_MM_MEMCQ_DEAD, "mm/memctrl:dead", NULL,
                                  memcg_hotplug_cpu_dead);

        for_each_possible_cpu(cpu)
                INIT_WORK(&per_cpu_ptr(&memcg_stock, cpu)->work,
                          drain_local_stock);

        return 0;
}
subsys_initcall(mem_cgroup_init);

#ifdef CONFIG_SWAP
static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
{
        while (!refcount_inc_not_zero(&memcg->id.ref)) {
                /*
                 * The root cgroup cannot be destroyed, so it's refcount must
                 * always be >= 1.
                 */
                if (WARN_ON_ONCE(mem_cgroup_is_root(memcg))) {
                        VM_BUG_ON(1);
                        break;
                }
                memcg = parent_mem_cgroup(memcg);
                if (!memcg)
                        memcg = root_mem_cgroup;
        }
        return memcg;
}

/**
 * mem_cgroup_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 mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
{
        struct mem_cgroup *memcg, *swap_memcg;
        unsigned int nr_entries;
        unsigned short oldid;

        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_id_get_online(memcg);
        nr_entries = folio_nr_pages(folio);
        /* Get references for the tail pages, too */
        if (nr_entries > 1)
                mem_cgroup_id_get_many(swap_memcg, nr_entries - 1);
        oldid = swap_cgroup_record(entry, mem_cgroup_id(swap_memcg),
                                   nr_entries);
        VM_BUG_ON_FOLIO(oldid, folio);
        mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);

        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);
        }

        memcg1_swapout(folio, memcg);
        css_put(&memcg->css);
}

/**
 * __mem_cgroup_try_charge_swap - try charging swap space for a folio
 * @folio: folio being added to swap
 * @entry: swap entry to charge
 *
 * Try to charge @folio's memcg for the swap space at @entry.
 *
 * Returns 0 on success, -ENOMEM on failure.
 */
int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry)
{
        unsigned int nr_pages = folio_nr_pages(folio);
        struct page_counter *counter;
        struct mem_cgroup *memcg;
        unsigned short oldid;

        if (do_memsw_account())
                return 0;

        memcg = folio_memcg(folio);

        VM_WARN_ON_ONCE_FOLIO(!memcg, folio);
        if (!memcg)
                return 0;

        if (!entry.val) {
                memcg_memory_event(memcg, MEMCG_SWAP_FAIL);
                return 0;
        }

        memcg = mem_cgroup_id_get_online(memcg);

        if (!mem_cgroup_is_root(memcg) &&
            !page_counter_try_charge(&memcg->swap, nr_pages, &counter)) {
                memcg_memory_event(memcg, MEMCG_SWAP_MAX);
                memcg_memory_event(memcg, MEMCG_SWAP_FAIL);
                mem_cgroup_id_put(memcg);
                return -ENOMEM;
        }

        /* Get references for the tail pages, too */
        if (nr_pages > 1)
                mem_cgroup_id_get_many(memcg, nr_pages - 1);
        oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg), nr_pages);
        VM_BUG_ON_FOLIO(oldid, folio);
        mod_memcg_state(memcg, MEMCG_SWAP, nr_pages);

        return 0;
}

/**
 * __mem_cgroup_uncharge_swap - uncharge swap space
 * @entry: swap entry to uncharge
 * @nr_pages: the amount of swap space to uncharge
 */
void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages)
{
        struct mem_cgroup *memcg;
        unsigned short id;

        id = swap_cgroup_record(entry, 0, nr_pages);
        rcu_read_lock();
        memcg = mem_cgroup_from_id(id);
        if (memcg) {
                if (!mem_cgroup_is_root(memcg)) {
                        if (do_memsw_account())
                                page_counter_uncharge(&memcg->memsw, nr_pages);
                        else
                                page_counter_uncharge(&memcg->swap, nr_pages);
                }
                mod_memcg_state(memcg, MEMCG_SWAP, -nr_pages);
                mem_cgroup_id_put_many(memcg, nr_pages);
        }
        rcu_read_unlock();
}

long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
{
        long nr_swap_pages = get_nr_swap_pages();

        if (mem_cgroup_disabled() || do_memsw_account())
                return nr_swap_pages;
        for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg))
                nr_swap_pages = min_t(long, nr_swap_pages,
                                      READ_ONCE(memcg->swap.max) -
                                      page_counter_read(&memcg->swap));
        return nr_swap_pages;
}

bool mem_cgroup_swap_full(struct folio *folio)
{
        struct mem_cgroup *memcg;

        VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);

        if (vm_swap_full())
                return true;
        if (do_memsw_account())
                return false;

        memcg = folio_memcg(folio);
        if (!memcg)
                return false;

        for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) {
                unsigned long usage = page_counter_read(&memcg->swap);

                if (usage * 2 >= READ_ONCE(memcg->swap.high) ||
                    usage * 2 >= READ_ONCE(memcg->swap.max))
                        return true;
        }

        return false;
}

static int __init setup_swap_account(char *s)
{
        bool res;

        if (!kstrtobool(s, &res) && !res)
                pr_warn_once("The swapaccount=0 commandline option is deprecated "
                             "in favor of configuring swap control via cgroupfs. "
                             "Please report your usecase to linux-mm@kvack.org if you "
                             "depend on this functionality.\n");
        return 1;
}
__setup("swapaccount=", setup_swap_account);

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

        return (u64)page_counter_read(&memcg->swap) * PAGE_SIZE;
}

static int swap_peak_show(struct seq_file *sf, void *v)
{
        struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(sf));

        return peak_show(sf, v, &memcg->swap);
}

static ssize_t swap_peak_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));

        return peak_write(of, buf, nbytes, off, &memcg->swap,
                          &memcg->swap_peaks);
}

static int swap_high_show(struct seq_file *m, void *v)
{
        return seq_puts_memcg_tunable(m,
                READ_ONCE(mem_cgroup_from_seq(m)->swap.high));
}

static ssize_t swap_high_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 high;
        int err;

        buf = strstrip(buf);
        err = page_counter_memparse(buf, "max", &high);
        if (err)
                return err;

        page_counter_set_high(&memcg->swap, high);

        return nbytes;
}

static int swap_max_show(struct seq_file *m, void *v)
{
        return seq_puts_memcg_tunable(m,
                READ_ONCE(mem_cgroup_from_seq(m)->swap.max));
}

static ssize_t swap_max_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 max;
        int err;

        buf = strstrip(buf);
        err = page_counter_memparse(buf, "max", &max);
        if (err)
                return err;

        xchg(&memcg->swap.max, max);

        return nbytes;
}

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

        seq_printf(m, "high %lu\n",
                   atomic_long_read(&memcg->memory_events[MEMCG_SWAP_HIGH]));
        seq_printf(m, "max %lu\n",
                   atomic_long_read(&memcg->memory_events[MEMCG_SWAP_MAX]));
        seq_printf(m, "fail %lu\n",
                   atomic_long_read(&memcg->memory_events[MEMCG_SWAP_FAIL]));

        return 0;
}

static struct cftype swap_files[] = {
        {
                .name = "swap.current",
                .flags = CFTYPE_NOT_ON_ROOT,
                .read_u64 = swap_current_read,
        },
        {
                .name = "swap.high",
                .flags = CFTYPE_NOT_ON_ROOT,
                .seq_show = swap_high_show,
                .write = swap_high_write,
        },
        {
                .name = "swap.max",
                .flags = CFTYPE_NOT_ON_ROOT,
                .seq_show = swap_max_show,
                .write = swap_max_write,
        },
        {
                .name = "swap.peak",
                .flags = CFTYPE_NOT_ON_ROOT,
                .open = peak_open,
                .release = peak_release,
                .seq_show = swap_peak_show,
                .write = swap_peak_write,
        },
        {
                .name = "swap.events",
                .flags = CFTYPE_NOT_ON_ROOT,
                .file_offset = offsetof(struct mem_cgroup, swap_events_file),
                .seq_show = swap_events_show,
        },
        { }     /* terminate */
};

#ifdef CONFIG_ZSWAP
/**
 * obj_cgroup_may_zswap - check if this cgroup can zswap
 * @objcg: the object cgroup
 *
 * Check if the hierarchical zswap limit has been reached.
 *
 * This doesn't check for specific headroom, and it is not atomic
 * either. But with zswap, the size of the allocation is only known
 * once compression has occurred, and this optimistic pre-check avoids
 * spending cycles on compression when there is already no room left
 * or zswap is disabled altogether somewhere in the hierarchy.
 */
bool obj_cgroup_may_zswap(struct obj_cgroup *objcg)
{
        struct mem_cgroup *memcg, *original_memcg;
        bool ret = true;

        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
                return true;

        original_memcg = get_mem_cgroup_from_objcg(objcg);
        for (memcg = original_memcg; !mem_cgroup_is_root(memcg);
             memcg = parent_mem_cgroup(memcg)) {
                unsigned long max = READ_ONCE(memcg->zswap_max);
                unsigned long pages;

                if (max == PAGE_COUNTER_MAX)
                        continue;
                if (max == 0) {
                        ret = false;
                        break;
                }

                /* Force flush to get accurate stats for charging */
                __mem_cgroup_flush_stats(memcg, true);
                pages = memcg_page_state(memcg, MEMCG_ZSWAP_B) / PAGE_SIZE;
                if (pages < max)
                        continue;
                ret = false;
                break;
        }
        mem_cgroup_put(original_memcg);
        return ret;
}

/**
 * obj_cgroup_charge_zswap - charge compression backend memory
 * @objcg: the object cgroup
 * @size: size of compressed object
 *
 * This forces the charge after obj_cgroup_may_zswap() allowed
 * compression and storage in zwap for this cgroup to go ahead.
 */
void obj_cgroup_charge_zswap(struct obj_cgroup *objcg, size_t size)
{
        struct mem_cgroup *memcg;

        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
                return;

        VM_WARN_ON_ONCE(!(current->flags & PF_MEMALLOC));

        /* PF_MEMALLOC context, charging must succeed */
        if (obj_cgroup_charge(objcg, GFP_KERNEL, size))
                VM_WARN_ON_ONCE(1);

        rcu_read_lock();
        memcg = obj_cgroup_memcg(objcg);
        mod_memcg_state(memcg, MEMCG_ZSWAP_B, size);
        mod_memcg_state(memcg, MEMCG_ZSWAPPED, 1);
        rcu_read_unlock();
}

/**
 * obj_cgroup_uncharge_zswap - uncharge compression backend memory
 * @objcg: the object cgroup
 * @size: size of compressed object
 *
 * Uncharges zswap memory on page in.
 */
void obj_cgroup_uncharge_zswap(struct obj_cgroup *objcg, size_t size)
{
        struct mem_cgroup *memcg;

        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
                return;

        obj_cgroup_uncharge(objcg, size);

        rcu_read_lock();
        memcg = obj_cgroup_memcg(objcg);
        mod_memcg_state(memcg, MEMCG_ZSWAP_B, -size);
        mod_memcg_state(memcg, MEMCG_ZSWAPPED, -1);
        rcu_read_unlock();
}

bool mem_cgroup_zswap_writeback_enabled(struct mem_cgroup *memcg)
{
        /* if zswap is disabled, do not block pages going to the swapping device */
        if (!zswap_is_enabled())
                return true;

        for (; memcg; memcg = parent_mem_cgroup(memcg))
                if (!READ_ONCE(memcg->zswap_writeback))
                        return false;

        return true;
}

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

        mem_cgroup_flush_stats(memcg);
        return memcg_page_state(memcg, MEMCG_ZSWAP_B);
}

static int zswap_max_show(struct seq_file *m, void *v)
{
        return seq_puts_memcg_tunable(m,
                READ_ONCE(mem_cgroup_from_seq(m)->zswap_max));
}

static ssize_t zswap_max_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 max;
        int err;

        buf = strstrip(buf);
        err = page_counter_memparse(buf, "max", &max);
        if (err)
                return err;

        xchg(&memcg->zswap_max, max);

        return nbytes;
}

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

        seq_printf(m, "%d\n", READ_ONCE(memcg->zswap_writeback));
        return 0;
}

static ssize_t zswap_writeback_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));
        int zswap_writeback;
        ssize_t parse_ret = kstrtoint(strstrip(buf), 0, &zswap_writeback);

        if (parse_ret)
                return parse_ret;

        if (zswap_writeback != 0 && zswap_writeback != 1)
                return -EINVAL;

        WRITE_ONCE(memcg->zswap_writeback, zswap_writeback);
        return nbytes;
}

static struct cftype zswap_files[] = {
        {
                .name = "zswap.current",
                .flags = CFTYPE_NOT_ON_ROOT,
                .read_u64 = zswap_current_read,
        },
        {
                .name = "zswap.max",
                .flags = CFTYPE_NOT_ON_ROOT,
                .seq_show = zswap_max_show,
                .write = zswap_max_write,
        },
        {
                .name = "zswap.writeback",
                .seq_show = zswap_writeback_show,
                .write = zswap_writeback_write,
        },
        { }     /* terminate */
};
#endif /* CONFIG_ZSWAP */

static int __init mem_cgroup_swap_init(void)
{
        if (mem_cgroup_disabled())
                return 0;

        WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, swap_files));
#ifdef CONFIG_MEMCG_V1
        WARN_ON(cgroup_add_legacy_cftypes(&memory_cgrp_subsys, memsw_files));
#endif
#ifdef CONFIG_ZSWAP
        WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, zswap_files));
#endif
        return 0;
}
subsys_initcall(mem_cgroup_swap_init);

#endif /* CONFIG_SWAP */