OSCL-LXR linux-6.0.1/​mm/​memcontrol.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* memcontrol.c - Memory Controller
  *
  * Copyright IBM Corporation, 2007
  * Author Balbir Singh <balbir@linux.vnet.ibm.com>
  *
  * Copyright 2007 OpenVZ SWsoft Inc
  * Author: Pavel Emelianov <xemul@openvz.org>
  *
  * Memory thresholds
  * Copyright (C) 2009 Nokia Corporation
  * Author: Kirill A. Shutemov
  *
  * Kernel Memory Controller
  * Copyright (C) 2012 Parallels Inc. and Google Inc.
  * Authors: Glauber Costa and Suleiman Souhlal
  *
  * Native page reclaim
  * Charge lifetime sanitation
  * Lockless page tracking & accounting
  * Unified hierarchy configuration model
  * Copyright (C) 2015 Red Hat, Inc., Johannes Weiner
  *
  * Per memcg lru locking
  * Copyright (C) 2020 Alibaba, Inc, Alex Shi
  */
 
 #include <linux/page_counter.h>
 #include <linux/memcontrol.h>
 #include <linux/cgroup.h>
 #include <linux/pagewalk.h>
 #include <linux/sched/mm.h>
 #include <linux/shmem_fs.h>
 #include <linux/hugetlb.h>
 #include <linux/pagemap.h>
 #include <linux/vm_event_item.h>
 #include <linux/smp.h>
 #include <linux/page-flags.h>
 #include <linux/backing-dev.h>
 #include <linux/bit_spinlock.h>
 #include <linux/rcupdate.h>
 #include <linux/limits.h>
 #include <linux/export.h>
 #include <linux/mutex.h>
 #include <linux/rbtree.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/swapops.h>
 #include <linux/spinlock.h>
 #include <linux/eventfd.h>
 #include <linux/poll.h>
 #include <linux/sort.h>
 #include <linux/fs.h>
 #include <linux/seq_file.h>
 #include <linux/vmpressure.h>
 #include <linux/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/file.h>
 #include <linux/resume_user_mode.h>
 #include <linux/psi.h>
 #include <linux/seq_buf.h>
 #include "internal.h"
 #include <net/sock.h>
 #include <net/ip.h>
 #include "slab.h"
 #include "swap.h"
 
 #include <linux/uaccess.h>
 
 #include <trace/events/vmscan.h>
 
 struct cgroup_subsys memory_cgrp_subsys __read_mostly;
 EXPORT_SYMBOL(memory_cgrp_subsys);
 
 struct mem_cgroup *root_mem_cgroup __read_mostly;
 
 /* Active memory cgroup to use from an interrupt context */
 DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
 EXPORT_PER_CPU_SYMBOL_GPL(int_active_memcg);
 
 /* Socket memory accounting disabled? */
 static bool cgroup_memory_nosocket __ro_after_init;
 
 /* Kernel memory accounting disabled? */
 static bool cgroup_memory_nokmem __ro_after_init;
 
 /* Whether the swap controller is active */
 #ifdef CONFIG_MEMCG_SWAP
 static bool cgroup_memory_noswap __ro_after_init;
 #else
 #define cgroup_memory_noswap        1
 #endif
 
 #ifdef CONFIG_CGROUP_WRITEBACK
 static DECLARE_WAIT_QUEUE_HEAD(memcg_cgwb_frn_waitq);
 #endif
 
 /* Whether legacy memory+swap accounting is active */
 static bool do_memsw_account(void)
 {
     return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_noswap;
 }
 
 #define THRESHOLDS_EVENTS_TARGET 128
 #define SOFTLIMIT_EVENTS_TARGET 1024
 
 /*
  * Cgroups above their limits are maintained in a RB-Tree, independent of
  * their hierarchy representation
  */
 
 struct mem_cgroup_tree_per_node {
     struct rb_root rb_root;
     struct rb_node *rb_rightmost;
     spinlock_t lock;
 };
 
 struct mem_cgroup_tree {
     struct mem_cgroup_tree_per_node *rb_tree_per_node[MAX_NUMNODES];
 };
 
 static struct mem_cgroup_tree soft_limit_tree __read_mostly;
 
 /* for OOM */
 struct mem_cgroup_eventfd_list {
     struct list_head list;
     struct eventfd_ctx *eventfd;
 };
 
 /*
  * cgroup_event represents events which userspace want to receive.
  */
 struct mem_cgroup_event {
     /*
      * memcg which the event belongs to.
      */
     struct mem_cgroup *memcg;
     /*
      * eventfd to signal userspace about the event.
      */
     struct eventfd_ctx *eventfd;
     /*
      * Each of these stored in a list by the cgroup.
      */
     struct list_head list;
     /*
      * register_event() callback will be used to add new userspace
      * waiter for changes related to this event.  Use eventfd_signal()
      * on eventfd to send notification to userspace.
      */
     int (*register_event)(struct mem_cgroup *memcg,
                   struct eventfd_ctx *eventfd, const char *args);
     /*
      * unregister_event() callback will be called when userspace closes
      * the eventfd or on cgroup removing.  This callback must be set,
      * if you want provide notification functionality.
      */
     void (*unregister_event)(struct mem_cgroup *memcg,
                  struct eventfd_ctx *eventfd);
     /*
      * All fields below needed to unregister event when
      * userspace closes eventfd.
      */
     poll_table pt;
     wait_queue_head_t *wqh;
     wait_queue_entry_t wait;
     struct work_struct remove;
 };
 
 static void mem_cgroup_threshold(struct mem_cgroup *memcg);
 static void mem_cgroup_oom_notify(struct mem_cgroup *memcg);
 
 /* Stuffs for move charges at task migration. */
 /*
  * Types of charges to be moved.
  */
 #define MOVE_ANON   0x1U
 #define MOVE_FILE   0x2U
 #define MOVE_MASK   (MOVE_ANON | MOVE_FILE)
 
 /* "mc" and its members are protected by cgroup_mutex */
 static struct move_charge_struct {
     spinlock_t    lock; /* for from, to */
     struct mm_struct  *mm;
     struct mem_cgroup *from;
     struct mem_cgroup *to;
     unsigned long flags;
     unsigned long precharge;
     unsigned long moved_charge;
     unsigned long moved_swap;
     struct task_struct *moving_task;    /* a task moving charges */
     wait_queue_head_t waitq;        /* a waitq for other context */
 } mc = {
     .lock = __SPIN_LOCK_UNLOCKED(mc.lock),
     .waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq),
 };
 
 /*
  * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
  * limit reclaim to prevent infinite loops, if they ever occur.
  */
 #define MEM_CGROUP_MAX_RECLAIM_LOOPS        100
 #define MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS 2
 
 /* for encoding cft->private value on file */
 enum res_type {
     _MEM,
     _MEMSWAP,
     _KMEM,
     _TCP,
 };
 
 #define MEMFILE_PRIVATE(x, val) ((x) << 16 | (val))
 #define MEMFILE_TYPE(val)   ((val) >> 16 & 0xffff)
 #define MEMFILE_ATTR(val)   ((val) & 0xffff)
 
 /*
  * Iteration constructs for visiting all cgroups (under a tree).  If
  * loops are exited prematurely (break), mem_cgroup_iter_break() must
  * be used for reference counting.
  */
 #define for_each_mem_cgroup_tree(iter, root)        \
     for (iter = mem_cgroup_iter(root, NULL, NULL);  \
          iter != NULL;              \
          iter = mem_cgroup_iter(root, iter, NULL))
 
 #define for_each_mem_cgroup(iter)           \
     for (iter = mem_cgroup_iter(NULL, NULL, NULL);  \
          iter != NULL;              \
          iter = mem_cgroup_iter(NULL, iter, NULL))
 
 static inline bool 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);
 }
 
 #ifdef CONFIG_MEMCG_KMEM
 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_pre_alloc_hook() are
  * conditional to this static branch, we'll have to allow modules that does
  * kmem_cache_alloc and the such to see this symbol as well
  */
 DEFINE_STATIC_KEY_FALSE(memcg_kmem_enabled_key);
 EXPORT_SYMBOL(memcg_kmem_enabled_key);
 #endif
 
 /**
  * mem_cgroup_css_from_page - css of the memcg associated with a page
  * @page: page of interest
  *
  * If memcg is bound to the default hierarchy, css of the memcg associated
  * with @page is returned.  The returned css remains associated with @page
  * until it is released.
  *
  * If memcg is bound to a traditional hierarchy, the css of root_mem_cgroup
  * is returned.
  */
 struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page)
 {
     struct mem_cgroup *memcg;
 
     memcg = page_memcg(page);
 
     if (!memcg || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
         memcg = root_mem_cgroup;
 
     return &memcg->css;
 }
 
 /**
  * page_cgroup_ino - return inode number of the memcg a page is charged to
  * @page: the page
  *
  * Look up the closest online ancestor of the memory cgroup @page is charged to
  * and return its inode number or 0 if @page is not charged to any cgroup. It
  * is safe to call this function without holding a reference to @page.
  *
  * Note, this function is inherently racy, because there is nothing to prevent
  * the cgroup inode from getting torn down and potentially reallocated a moment
  * after page_cgroup_ino() returns, so it only should be used by callers that
  * do not care (such as procfs interfaces).
  */
 ino_t page_cgroup_ino(struct page *page)
 {
     struct mem_cgroup *memcg;
     unsigned long ino = 0;
 
     rcu_read_lock();
     memcg = page_memcg_check(page);
 
     while (memcg && !(memcg->css.flags & CSS_ONLINE))
         memcg = parent_mem_cgroup(memcg);
     if (memcg)
         ino = cgroup_ino(memcg->css.cgroup);
     rcu_read_unlock();
     return ino;
 }
 
 static void __mem_cgroup_insert_exceeded(struct mem_cgroup_per_node *mz,
                      struct mem_cgroup_tree_per_node *mctz,
                      unsigned long new_usage_in_excess)
 {
     struct rb_node **p = &mctz->rb_root.rb_node;
     struct rb_node *parent = NULL;
     struct mem_cgroup_per_node *mz_node;
     bool rightmost = true;
 
     if (mz->on_tree)
         return;
 
     mz->usage_in_excess = new_usage_in_excess;
     if (!mz->usage_in_excess)
         return;
     while (*p) {
         parent = *p;
         mz_node = rb_entry(parent, struct mem_cgroup_per_node,
                     tree_node);
         if (mz->usage_in_excess < mz_node->usage_in_excess) {
             p = &(*p)->rb_left;
             rightmost = false;
         } else {
             p = &(*p)->rb_right;
         }
     }
 
     if (rightmost)
         mctz->rb_rightmost = &mz->tree_node;
 
     rb_link_node(&mz->tree_node, parent, p);
     rb_insert_color(&mz->tree_node, &mctz->rb_root);
     mz->on_tree = true;
 }
 
 static void __mem_cgroup_remove_exceeded(struct mem_cgroup_per_node *mz,
                      struct mem_cgroup_tree_per_node *mctz)
 {
     if (!mz->on_tree)
         return;
 
     if (&mz->tree_node == mctz->rb_rightmost)
         mctz->rb_rightmost = rb_prev(&mz->tree_node);
 
     rb_erase(&mz->tree_node, &mctz->rb_root);
     mz->on_tree = false;
 }
 
 static void mem_cgroup_remove_exceeded(struct mem_cgroup_per_node *mz,
                        struct mem_cgroup_tree_per_node *mctz)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&mctz->lock, flags);
     __mem_cgroup_remove_exceeded(mz, mctz);
     spin_unlock_irqrestore(&mctz->lock, flags);
 }
 
 static unsigned long soft_limit_excess(struct mem_cgroup *memcg)
 {
     unsigned long nr_pages = page_counter_read(&memcg->memory);
     unsigned long soft_limit = READ_ONCE(memcg->soft_limit);
     unsigned long excess = 0;
 
     if (nr_pages > soft_limit)
         excess = nr_pages - soft_limit;
 
     return excess;
 }
 
 static void mem_cgroup_update_tree(struct mem_cgroup *memcg, int nid)
 {
     unsigned long excess;
     struct mem_cgroup_per_node *mz;
     struct mem_cgroup_tree_per_node *mctz;
 
     mctz = soft_limit_tree.rb_tree_per_node[nid];
     if (!mctz)
         return;
     /*
      * Necessary to update all ancestors when hierarchy is used.
      * because their event counter is not touched.
      */
     for (; memcg; memcg = parent_mem_cgroup(memcg)) {
         mz = memcg->nodeinfo[nid];
         excess = soft_limit_excess(memcg);
         /*
          * We have to update the tree if mz is on RB-tree or
          * mem is over its softlimit.
          */
         if (excess || mz->on_tree) {
             unsigned long flags;
 
             spin_lock_irqsave(&mctz->lock, flags);
             /* if on-tree, remove it */
             if (mz->on_tree)
                 __mem_cgroup_remove_exceeded(mz, mctz);
             /*
              * Insert again. mz->usage_in_excess will be updated.
              * If excess is 0, no tree ops.
              */
             __mem_cgroup_insert_exceeded(mz, mctz, excess);
             spin_unlock_irqrestore(&mctz->lock, flags);
         }
     }
 }
 
 static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
 {
     struct mem_cgroup_tree_per_node *mctz;
     struct mem_cgroup_per_node *mz;
     int nid;
 
     for_each_node(nid) {
         mz = memcg->nodeinfo[nid];
         mctz = soft_limit_tree.rb_tree_per_node[nid];
         if (mctz)
             mem_cgroup_remove_exceeded(mz, mctz);
     }
 }
 
 static struct mem_cgroup_per_node *
 __mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz)
 {
     struct mem_cgroup_per_node *mz;
 
 retry:
     mz = NULL;
     if (!mctz->rb_rightmost)
         goto done;      /* Nothing to reclaim from */
 
     mz = rb_entry(mctz->rb_rightmost,
               struct mem_cgroup_per_node, tree_node);
     /*
      * Remove the node now but someone else can add it back,
      * we will to add it back at the end of reclaim to its correct
      * position in the tree.
      */
     __mem_cgroup_remove_exceeded(mz, mctz);
     if (!soft_limit_excess(mz->memcg) ||
         !css_tryget(&mz->memcg->css))
         goto retry;
 done:
     return mz;
 }
 
 static struct mem_cgroup_per_node *
 mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz)
 {
     struct mem_cgroup_per_node *mz;
 
     spin_lock_irq(&mctz->lock);
     mz = __mem_cgroup_largest_soft_limit_node(mctz);
     spin_unlock_irq(&mctz->lock);
     return mz;
 }
 
 /*
  * 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 DEFINE_SPINLOCK(stats_flush_lock);
 static DEFINE_PER_CPU(unsigned int, stats_updates);
 static atomic_t stats_flush_threshold = ATOMIC_INIT(0);
 static u64 flush_next_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)
 {
 #ifdef CONFIG_PREEMPT_RT
       preempt_disable();
 #else
       VM_BUG_ON(!irqs_disabled());
 #endif
 }
 
 static void __memcg_stats_lock(void)
 {
 #ifdef CONFIG_PREEMPT_RT
       preempt_disable();
 #endif
 }
 
 static void memcg_stats_unlock(void)
 {
 #ifdef CONFIG_PREEMPT_RT
       preempt_enable();
 #endif
 }
 
 static inline void memcg_rstat_updated(struct mem_cgroup *memcg, int val)
 {
     unsigned int x;
 
     cgroup_rstat_updated(memcg->css.cgroup, smp_processor_id());
 
     x = __this_cpu_add_return(stats_updates, abs(val));
     if (x > MEMCG_CHARGE_BATCH) {
         /*
          * If stats_flush_threshold exceeds the threshold
          * (>num_online_cpus()), cgroup stats update will be triggered
          * in __mem_cgroup_flush_stats(). Increasing this var further
          * is redundant and simply adds overhead in atomic update.
          */
         if (atomic_read(&stats_flush_threshold) <= num_online_cpus())
             atomic_add(x / MEMCG_CHARGE_BATCH, &stats_flush_threshold);
         __this_cpu_write(stats_updates, 0);
     }
 }
 
 static void __mem_cgroup_flush_stats(void)
 {
     unsigned long flag;
 
     if (!spin_trylock_irqsave(&stats_flush_lock, flag))
         return;
 
     flush_next_time = jiffies_64 + 2*FLUSH_TIME;
     cgroup_rstat_flush_irqsafe(root_mem_cgroup->css.cgroup);
     atomic_set(&stats_flush_threshold, 0);
     spin_unlock_irqrestore(&stats_flush_lock, flag);
 }
 
 void mem_cgroup_flush_stats(void)
 {
     if (atomic_read(&stats_flush_threshold) > num_online_cpus())
         __mem_cgroup_flush_stats();
 }
 
 void mem_cgroup_flush_stats_delayed(void)
 {
     if (time_after64(jiffies_64, flush_next_time))
         mem_cgroup_flush_stats();
 }
 
 static void flush_memcg_stats_dwork(struct work_struct *w)
 {
     __mem_cgroup_flush_stats();
     queue_delayed_work(system_unbound_wq, &stats_flush_dwork, FLUSH_TIME);
 }
 
 /**
  * __mod_memcg_state - update cgroup memory statistics
  * @memcg: the memory cgroup
  * @idx: the stat item - can be enum memcg_stat_item or enum node_stat_item
  * @val: delta to add to the counter, can be negative
  */
 void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val)
 {
     if (mem_cgroup_disabled())
         return;
 
     __this_cpu_add(memcg->vmstats_percpu->state[idx], val);
     memcg_rstat_updated(memcg, val);
 }
 
 /* idx can be of type enum memcg_stat_item or node_stat_item. */
 static unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx)
 {
     long x = 0;
     int cpu;
 
     for_each_possible_cpu(cpu)
         x += per_cpu(memcg->vmstats_percpu->state[idx], cpu);
 #ifdef CONFIG_SMP
     if (x < 0)
         x = 0;
 #endif
     return x;
 }
 
 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;
 
     pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
     memcg = pn->memcg;
 
     /*
      * The caller from rmap relay on disabled preemption becase 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) && !IS_ENABLED(CONFIG_PREEMPT_RT)) {
         switch (idx) {
         case NR_ANON_MAPPED:
         case NR_FILE_MAPPED:
         case NR_ANON_THPS:
         case NR_SHMEM_PMDMAPPED:
         case NR_FILE_PMDMAPPED:
             WARN_ON_ONCE(!in_task());
             break;
         default:
             WARN_ON_ONCE(!irqs_disabled());
         }
     }
 
     /* Update memcg */
     __this_cpu_add(memcg->vmstats_percpu->state[idx], val);
 
     /* Update lruvec */
     __this_cpu_add(pn->lruvec_stats_percpu->state[idx], val);
 
     memcg_rstat_updated(memcg, 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 __mod_lruvec_page_state(struct page *page, enum node_stat_item idx,
                  int val)
 {
     struct page *head = compound_head(page); /* rmap on tail pages */
     struct mem_cgroup *memcg;
     pg_data_t *pgdat = page_pgdat(page);
     struct lruvec *lruvec;
 
     rcu_read_lock();
     memcg = page_memcg(head);
     /* Untracked pages have no memcg, no lruvec. Update only the node */
     if (!memcg) {
         rcu_read_unlock();
         __mod_node_page_state(pgdat, idx, val);
         return;
     }
 
     lruvec = mem_cgroup_lruvec(memcg, pgdat);
     __mod_lruvec_state(lruvec, idx, val);
     rcu_read_unlock();
 }
 EXPORT_SYMBOL(__mod_lruvec_page_state);
 
 void __mod_lruvec_kmem_state(void *p, enum node_stat_item idx, int val)
 {
     pg_data_t *pgdat = page_pgdat(virt_to_page(p));
     struct mem_cgroup *memcg;
     struct lruvec *lruvec;
 
     rcu_read_lock();
     memcg = mem_cgroup_from_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)
 {
     if (mem_cgroup_disabled())
         return;
 
     memcg_stats_lock();
     __this_cpu_add(memcg->vmstats_percpu->events[idx], count);
     memcg_rstat_updated(memcg, count);
     memcg_stats_unlock();
 }
 
 static unsigned long memcg_events(struct mem_cgroup *memcg, int event)
 {
     return READ_ONCE(memcg->vmstats.events[event]);
 }
 
 static unsigned long memcg_events_local(struct mem_cgroup *memcg, int event)
 {
     long x = 0;
     int cpu;
 
     for_each_possible_cpu(cpu)
         x += per_cpu(memcg->vmstats_percpu->events[event], cpu);
     return x;
 }
 
 static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
                      int nr_pages)
 {
     /* pagein of a big page is an event. So, ignore page size */
     if (nr_pages > 0)
         __count_memcg_events(memcg, PGPGIN, 1);
     else {
         __count_memcg_events(memcg, PGPGOUT, 1);
         nr_pages = -nr_pages; /* for event */
     }
 
     __this_cpu_add(memcg->vmstats_percpu->nr_page_events, nr_pages);
 }
 
 static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
                        enum mem_cgroup_events_target target)
 {
     unsigned long val, next;
 
     val = __this_cpu_read(memcg->vmstats_percpu->nr_page_events);
     next = __this_cpu_read(memcg->vmstats_percpu->targets[target]);
     /* from time_after() in jiffies.h */
     if ((long)(next - val) < 0) {
         switch (target) {
         case MEM_CGROUP_TARGET_THRESH:
             next = val + THRESHOLDS_EVENTS_TARGET;
             break;
         case MEM_CGROUP_TARGET_SOFTLIMIT:
             next = val + SOFTLIMIT_EVENTS_TARGET;
             break;
         default:
             break;
         }
         __this_cpu_write(memcg->vmstats_percpu->targets[target], next);
         return true;
     }
     return false;
 }
 
 /*
  * Check events in order.
  *
  */
 static void memcg_check_events(struct mem_cgroup *memcg, int nid)
 {
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         return;
 
     /* threshold event is triggered in finer grain than soft limit */
     if (unlikely(mem_cgroup_event_ratelimit(memcg,
                         MEM_CGROUP_TARGET_THRESH))) {
         bool do_softlimit;
 
         do_softlimit = mem_cgroup_event_ratelimit(memcg,
                         MEM_CGROUP_TARGET_SOFTLIMIT);
         mem_cgroup_threshold(memcg);
         if (unlikely(do_softlimit))
             mem_cgroup_update_tree(memcg, nid);
     }
 }
 
 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);
 
 static __always_inline bool memcg_kmem_bypass(void)
 {
     /* Allow remote memcg charging from any context. */
     if (unlikely(active_memcg()))
         return false;
 
     /* Memcg to charge can't be determined. */
     if (!in_task() || !current->mm || (current->flags & PF_KTHREAD))
         return true;
 
     return false;
 }
 
 /**
  * mem_cgroup_iter - iterate over memory cgroup hierarchy
  * @root: hierarchy root
  * @prev: previously returned memcg, NULL on first invocation
  * @reclaim: cookie for shared reclaim walks, NULL for full walks
  *
  * Returns references to children of the hierarchy below @root, or
  * @root itself, or %NULL after a full round-trip.
  *
  * Caller must pass the return value in @prev on subsequent
  * invocations for reference counting, or use mem_cgroup_iter_break()
  * to cancel a hierarchy walk before the round-trip is complete.
  *
  * Reclaimers can specify a node in @reclaim to divide up the memcgs
  * in the hierarchy among all concurrent reclaimers operating on the
  * same node.
  */
 struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
                    struct mem_cgroup *prev,
                    struct mem_cgroup_reclaim_cookie *reclaim)
 {
     struct mem_cgroup_reclaim_iter *iter;
     struct cgroup_subsys_state *css = NULL;
     struct mem_cgroup *memcg = NULL;
     struct mem_cgroup *pos = NULL;
 
     if (mem_cgroup_disabled())
         return NULL;
 
     if (!root)
         root = root_mem_cgroup;
 
     rcu_read_lock();
 
     if (reclaim) {
         struct mem_cgroup_per_node *mz;
 
         mz = root->nodeinfo[reclaim->pgdat->node_id];
         iter = &mz->iter;
 
         /*
          * On start, join the current reclaim iteration cycle.
          * Exit when a concurrent walker completes it.
          */
         if (!prev)
             reclaim->generation = iter->generation;
         else if (reclaim->generation != iter->generation)
             goto out_unlock;
 
         while (1) {
             pos = READ_ONCE(iter->position);
             if (!pos || css_tryget(&pos->css))
                 break;
             /*
              * css reference reached zero, so iter->position will
              * be cleared by ->css_released. However, we should not
              * rely on this happening soon, because ->css_released
              * is called from a work queue, and by busy-waiting we
              * might block it. So we clear iter->position right
              * away.
              */
             (void)cmpxchg(&iter->position, pos, NULL);
         }
     } else if (prev) {
         pos = prev;
     }
 
     if (pos)
         css = &pos->css;
 
     for (;;) {
         css = css_next_descendant_pre(css, &root->css);
         if (!css) {
             /*
              * Reclaimers share the hierarchy walk, and a
              * new one might jump in right at the end of
              * the hierarchy - make sure they see at least
              * one group and restart from the beginning.
              */
             if (!prev)
                 continue;
             break;
         }
 
         /*
          * Verify the css and acquire a reference.  The root
          * is provided by the caller, so we know it's alive
          * and kicking, and don't take an extra reference.
          */
         if (css == &root->css || css_tryget(css)) {
             memcg = mem_cgroup_from_css(css);
             break;
         }
     }
 
     if (reclaim) {
         /*
          * The position could have already been updated by a competing
          * thread, so check that the value hasn't changed since we read
          * it to avoid reclaiming from the same cgroup twice.
          */
         (void)cmpxchg(&iter->position, pos, memcg);
 
         if (pos)
             css_put(&pos->css);
 
         if (!memcg)
             iter->generation++;
     }
 
 out_unlock:
     rcu_read_unlock();
     if (prev && prev != root)
         css_put(&prev->css);
 
     return memcg;
 }
 
 /**
  * mem_cgroup_iter_break - abort a hierarchy walk prematurely
  * @root: hierarchy root
  * @prev: last visited hierarchy member as returned by mem_cgroup_iter()
  */
 void mem_cgroup_iter_break(struct mem_cgroup *root,
                struct mem_cgroup *prev)
 {
     if (!root)
         root = root_mem_cgroup;
     if (prev && prev != root)
         css_put(&prev->css);
 }
 
 static void __invalidate_reclaim_iterators(struct mem_cgroup *from,
                     struct mem_cgroup *dead_memcg)
 {
     struct mem_cgroup_reclaim_iter *iter;
     struct mem_cgroup_per_node *mz;
     int nid;
 
     for_each_node(nid) {
         mz = from->nodeinfo[nid];
         iter = &mz->iter;
         cmpxchg(&iter->position, dead_memcg, NULL);
     }
 }
 
 static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg)
 {
     struct mem_cgroup *memcg = dead_memcg;
     struct mem_cgroup *last;
 
     do {
         __invalidate_reclaim_iterators(memcg, dead_memcg);
         last = memcg;
     } while ((memcg = parent_mem_cgroup(memcg)));
 
     /*
      * When cgruop1 non-hierarchy mode is used,
      * parent_mem_cgroup() does not walk all the way up to the
      * cgroup root (root_mem_cgroup). So we have to handle
      * dead_memcg from cgroup root separately.
      */
     if (last != root_mem_cgroup)
         __invalidate_reclaim_iterators(root_mem_cgroup,
                         dead_memcg);
 }
 
 /**
  * mem_cgroup_scan_tasks - iterate over tasks of a memory cgroup hierarchy
  * @memcg: hierarchy root
  * @fn: function to call for each task
  * @arg: argument passed to @fn
  *
  * This function iterates over tasks attached to @memcg or to any of its
  * descendants and calls @fn for each task. If @fn returns a non-zero
  * value, the function breaks the iteration loop and returns the value.
  * Otherwise, it will iterate over all tasks and return 0.
  *
  * This function must not be called for the root memory cgroup.
  */
 int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
               int (*fn)(struct task_struct *, void *), void *arg)
 {
     struct mem_cgroup *iter;
     int ret = 0;
 
     BUG_ON(memcg == root_mem_cgroup);
 
     for_each_mem_cgroup_tree(iter, memcg) {
         struct css_task_iter it;
         struct task_struct *task;
 
         css_task_iter_start(&iter->css, CSS_TASK_ITER_PROCS, &it);
         while (!ret && (task = css_task_iter_next(&it)))
             ret = fn(task, arg);
         css_task_iter_end(&it);
         if (ret) {
             mem_cgroup_iter_break(memcg, iter);
             break;
         }
     }
     return ret;
 }
 
 #ifdef CONFIG_DEBUG_VM
 void lruvec_memcg_debug(struct lruvec *lruvec, struct folio *folio)
 {
     struct mem_cgroup *memcg;
 
     if (mem_cgroup_disabled())
         return;
 
     memcg = folio_memcg(folio);
 
     if (!memcg)
         VM_BUG_ON_FOLIO(lruvec_memcg(lruvec) != root_mem_cgroup, 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_memcg_lock()
  * - 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_memcg_lock()
  * - 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_memcg_lock()
  * - 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;
 }
 
 /*
  * A routine for checking "mem" is under move_account() or not.
  *
  * Checking a cgroup is mc.from or mc.to or under hierarchy of
  * moving cgroups. This is for waiting at high-memory pressure
  * caused by "move".
  */
 static bool mem_cgroup_under_move(struct mem_cgroup *memcg)
 {
     struct mem_cgroup *from;
     struct mem_cgroup *to;
     bool ret = false;
     /*
      * Unlike task_move routines, we access mc.to, mc.from not under
      * mutual exclusion by cgroup_mutex. Here, we take spinlock instead.
      */
     spin_lock(&mc.lock);
     from = mc.from;
     to = mc.to;
     if (!from)
         goto unlock;
 
     ret = mem_cgroup_is_descendant(from, memcg) ||
         mem_cgroup_is_descendant(to, memcg);
 unlock:
     spin_unlock(&mc.lock);
     return ret;
 }
 
 static bool mem_cgroup_wait_acct_move(struct mem_cgroup *memcg)
 {
     if (mc.moving_task && current != mc.moving_task) {
         if (mem_cgroup_under_move(memcg)) {
             DEFINE_WAIT(wait);
             prepare_to_wait(&mc.waitq, &wait, TASK_INTERRUPTIBLE);
             /* moving charge context might have finished. */
             if (mc.moving_task)
                 schedule();
             finish_wait(&mc.waitq, &wait);
             return true;
         }
     }
     return false;
 }
 
 struct memory_stat {
     const char *name;
     unsigned int idx;
 };
 
 static const struct memory_stat memory_stats[] = {
     { "anon",           NR_ANON_MAPPED          },
     { "file",           NR_FILE_PAGES           },
     { "kernel",         MEMCG_KMEM          },
     { "kernel_stack",       NR_KERNEL_STACK_KB      },
     { "pagetables",         NR_PAGETABLE            },
     { "percpu",         MEMCG_PERCPU_B          },
     { "sock",           MEMCG_SOCK          },
     { "vmalloc",            MEMCG_VMALLOC           },
     { "shmem",          NR_SHMEM            },
 #if defined(CONFIG_MEMCG_KMEM) && defined(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     },
 
     /* The memory events */
     { "workingset_refault_anon",    WORKINGSET_REFAULT_ANON     },
     { "workingset_refault_file",    WORKINGSET_REFAULT_FILE     },
     { "workingset_activate_anon",   WORKINGSET_ACTIVATE_ANON    },
     { "workingset_activate_file",   WORKINGSET_ACTIVATE_FILE    },
     { "workingset_restore_anon",    WORKINGSET_RESTORE_ANON     },
     { "workingset_restore_file",    WORKINGSET_RESTORE_FILE     },
     { "workingset_nodereclaim", WORKINGSET_NODERECLAIM      },
 };
 
 /* Translate stat items to the correct unit for memory.stat output */
 static int memcg_page_state_unit(int item)
 {
     switch (item) {
     case MEMCG_PERCPU_B:
     case MEMCG_ZSWAP_B:
     case NR_SLAB_RECLAIMABLE_B:
     case NR_SLAB_UNRECLAIMABLE_B:
     case WORKINGSET_REFAULT_ANON:
     case WORKINGSET_REFAULT_FILE:
     case WORKINGSET_ACTIVATE_ANON:
     case WORKINGSET_ACTIVATE_FILE:
     case WORKINGSET_RESTORE_ANON:
     case WORKINGSET_RESTORE_FILE:
     case WORKINGSET_NODERECLAIM:
         return 1;
     case NR_KERNEL_STACK_KB:
         return SZ_1K;
     default:
         return PAGE_SIZE;
     }
 }
 
 static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg,
                             int item)
 {
     return memcg_page_state(memcg, item) * memcg_page_state_unit(item);
 }
 
 /* Subset of vm_event_item to report for memcg event stats */
 static const unsigned int memcg_vm_event_stat[] = {
     PGSCAN_KSWAPD,
     PGSCAN_DIRECT,
     PGSTEAL_KSWAPD,
     PGSTEAL_DIRECT,
     PGFAULT,
     PGMAJFAULT,
     PGREFILL,
     PGACTIVATE,
     PGDEACTIVATE,
     PGLAZYFREE,
     PGLAZYFREED,
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
     ZSWPIN,
     ZSWPOUT,
 #endif
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     THP_FAULT_ALLOC,
     THP_COLLAPSE_ALLOC,
 #endif
 };
 
 static void memory_stat_format(struct mem_cgroup *memcg, char *buf, int bufsize)
 {
     struct seq_buf s;
     int i;
 
     seq_buf_init(&s, buf, bufsize);
 
     /*
      * 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();
 
     for (i = 0; i < ARRAY_SIZE(memory_stats); i++) {
         u64 size;
 
         size = memcg_page_state_output(memcg, memory_stats[i].idx);
         seq_buf_printf(&s, "%s %llu\n", memory_stats[i].name, size);
 
         if (unlikely(memory_stats[i].idx == NR_SLAB_UNRECLAIMABLE_B)) {
             size += memcg_page_state_output(memcg,
                             NR_SLAB_RECLAIMABLE_B);
             seq_buf_printf(&s, "slab %llu\n", size);
         }
     }
 
     /* Accumulated memory events */
     seq_buf_printf(&s, "pgscan %lu\n",
                memcg_events(memcg, PGSCAN_KSWAPD) +
                memcg_events(memcg, PGSCAN_DIRECT));
     seq_buf_printf(&s, "pgsteal %lu\n",
                memcg_events(memcg, PGSTEAL_KSWAPD) +
                memcg_events(memcg, PGSTEAL_DIRECT));
 
     for (i = 0; i < ARRAY_SIZE(memcg_vm_event_stat); i++)
         seq_buf_printf(&s, "%s %lu\n",
                    vm_event_name(memcg_vm_event_stat[i]),
                    memcg_events(memcg, memcg_vm_event_stat[i]));
 
     /* The above should easily fit into one page */
     WARN_ON_ONCE(seq_buf_has_overflowed(&s));
 }
 
 #define K(x) ((x) << (PAGE_SHIFT-10))
 /**
  * mem_cgroup_print_oom_context: Print OOM information relevant to
  * memory controller.
  * @memcg: The memory cgroup that went over limit
  * @p: Task that is going to be killed
  *
  * NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
  * enabled
  */
 void mem_cgroup_print_oom_context(struct mem_cgroup *memcg, struct task_struct *p)
 {
     rcu_read_lock();
 
     if (memcg) {
         pr_cont(",oom_memcg=");
         pr_cont_cgroup_path(memcg->css.cgroup);
     } else
         pr_cont(",global_oom");
     if (p) {
         pr_cont(",task_memcg=");
         pr_cont_cgroup_path(task_cgroup(p, memory_cgrp_id));
     }
     rcu_read_unlock();
 }
 
 /**
  * mem_cgroup_print_oom_meminfo: Print OOM memory information relevant to
  * memory controller.
  * @memcg: The memory cgroup that went over limit
  */
 void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
 {
     /* Use static buffer, for the caller is holding oom_lock. */
     static char buf[PAGE_SIZE];
 
     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);
     else {
         pr_info("memory+swap: usage %llukB, limit %llukB, failcnt %lu\n",
             K((u64)page_counter_read(&memcg->memsw)),
             K((u64)memcg->memsw.max), memcg->memsw.failcnt);
         pr_info("kmem: usage %llukB, limit %llukB, failcnt %lu\n",
             K((u64)page_counter_read(&memcg->kmem)),
             K((u64)memcg->kmem.max), memcg->kmem.failcnt);
     }
 
     pr_info("Memory cgroup stats for ");
     pr_cont_cgroup_path(memcg->css.cgroup);
     pr_cont(":");
     memory_stat_format(memcg, buf, sizeof(buf));
     pr_info("%s", buf);
 }
 
 /*
  * Return the memory (and swap, if configured) limit for a memcg.
  */
 unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg)
 {
     unsigned long max = READ_ONCE(memcg->memory.max);
 
     if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
         if (mem_cgroup_swappiness(memcg))
             max += min(READ_ONCE(memcg->swap.max),
                    (unsigned long)total_swap_pages);
     } else { /* v1 */
         if (mem_cgroup_swappiness(memcg)) {
             /* Calculate swap excess capacity from memsw limit */
             unsigned long swap = READ_ONCE(memcg->memsw.max) - max;
 
             max += min(swap, (unsigned long)total_swap_pages);
         }
     }
     return max;
 }
 
 unsigned long mem_cgroup_size(struct mem_cgroup *memcg)
 {
     return page_counter_read(&memcg->memory);
 }
 
 static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
                      int order)
 {
     struct oom_control oc = {
         .zonelist = NULL,
         .nodemask = NULL,
         .memcg = memcg,
         .gfp_mask = gfp_mask,
         .order = order,
     };
     bool ret = true;
 
     if (mutex_lock_killable(&oom_lock))
         return true;
 
     if (mem_cgroup_margin(memcg) >= (1 << order))
         goto unlock;
 
     /*
      * A few threads which were not waiting at mutex_lock_killable() can
      * fail to bail out. Therefore, check again after holding oom_lock.
      */
     ret = task_is_dying() || out_of_memory(&oc);
 
 unlock:
     mutex_unlock(&oom_lock);
     return ret;
 }
 
 static int mem_cgroup_soft_reclaim(struct mem_cgroup *root_memcg,
                    pg_data_t *pgdat,
                    gfp_t gfp_mask,
                    unsigned long *total_scanned)
 {
     struct mem_cgroup *victim = NULL;
     int total = 0;
     int loop = 0;
     unsigned long excess;
     unsigned long nr_scanned;
     struct mem_cgroup_reclaim_cookie reclaim = {
         .pgdat = pgdat,
     };
 
     excess = soft_limit_excess(root_memcg);
 
     while (1) {
         victim = mem_cgroup_iter(root_memcg, victim, &reclaim);
         if (!victim) {
             loop++;
             if (loop >= 2) {
                 /*
                  * If we have not been able to reclaim
                  * anything, it might because there are
                  * no reclaimable pages under this hierarchy
                  */
                 if (!total)
                     break;
                 /*
                  * We want to do more targeted reclaim.
                  * excess >> 2 is not to excessive so as to
                  * reclaim too much, nor too less that we keep
                  * coming back to reclaim from this cgroup
                  */
                 if (total >= (excess >> 2) ||
                     (loop > MEM_CGROUP_MAX_RECLAIM_LOOPS))
                     break;
             }
             continue;
         }
         total += mem_cgroup_shrink_node(victim, gfp_mask, false,
                     pgdat, &nr_scanned);
         *total_scanned += nr_scanned;
         if (!soft_limit_excess(root_memcg))
             break;
     }
     mem_cgroup_iter_break(root_memcg, victim);
     return total;
 }
 
 #ifdef CONFIG_LOCKDEP
 static struct lockdep_map memcg_oom_lock_dep_map = {
     .name = "memcg_oom_lock",
 };
 #endif
 
 static DEFINE_SPINLOCK(memcg_oom_lock);
 
 /*
  * Check OOM-Killer is already running under our hierarchy.
  * If someone is running, return false.
  */
 static bool mem_cgroup_oom_trylock(struct mem_cgroup *memcg)
 {
     struct mem_cgroup *iter, *failed = NULL;
 
     spin_lock(&memcg_oom_lock);
 
     for_each_mem_cgroup_tree(iter, memcg) {
         if (iter->oom_lock) {
             /*
              * this subtree of our hierarchy is already locked
              * so we cannot give a lock.
              */
             failed = iter;
             mem_cgroup_iter_break(memcg, iter);
             break;
         } else
             iter->oom_lock = true;
     }
 
     if (failed) {
         /*
          * OK, we failed to lock the whole subtree so we have
          * to clean up what we set up to the failing subtree
          */
         for_each_mem_cgroup_tree(iter, memcg) {
             if (iter == failed) {
                 mem_cgroup_iter_break(memcg, iter);
                 break;
             }
             iter->oom_lock = false;
         }
     } else
         mutex_acquire(&memcg_oom_lock_dep_map, 0, 1, _RET_IP_);
 
     spin_unlock(&memcg_oom_lock);
 
     return !failed;
 }
 
 static void mem_cgroup_oom_unlock(struct mem_cgroup *memcg)
 {
     struct mem_cgroup *iter;
 
     spin_lock(&memcg_oom_lock);
     mutex_release(&memcg_oom_lock_dep_map, _RET_IP_);
     for_each_mem_cgroup_tree(iter, memcg)
         iter->oom_lock = false;
     spin_unlock(&memcg_oom_lock);
 }
 
 static void mem_cgroup_mark_under_oom(struct mem_cgroup *memcg)
 {
     struct mem_cgroup *iter;
 
     spin_lock(&memcg_oom_lock);
     for_each_mem_cgroup_tree(iter, memcg)
         iter->under_oom++;
     spin_unlock(&memcg_oom_lock);
 }
 
 static void mem_cgroup_unmark_under_oom(struct mem_cgroup *memcg)
 {
     struct mem_cgroup *iter;
 
     /*
      * Be careful about under_oom underflows because a child memcg
      * could have been added after mem_cgroup_mark_under_oom.
      */
     spin_lock(&memcg_oom_lock);
     for_each_mem_cgroup_tree(iter, memcg)
         if (iter->under_oom > 0)
             iter->under_oom--;
     spin_unlock(&memcg_oom_lock);
 }
 
 static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);
 
 struct oom_wait_info {
     struct mem_cgroup *memcg;
     wait_queue_entry_t  wait;
 };
 
 static int memcg_oom_wake_function(wait_queue_entry_t *wait,
     unsigned mode, int sync, void *arg)
 {
     struct mem_cgroup *wake_memcg = (struct mem_cgroup *)arg;
     struct mem_cgroup *oom_wait_memcg;
     struct oom_wait_info *oom_wait_info;
 
     oom_wait_info = container_of(wait, struct oom_wait_info, wait);
     oom_wait_memcg = oom_wait_info->memcg;
 
     if (!mem_cgroup_is_descendant(wake_memcg, oom_wait_memcg) &&
         !mem_cgroup_is_descendant(oom_wait_memcg, wake_memcg))
         return 0;
     return autoremove_wake_function(wait, mode, sync, arg);
 }
 
 static void memcg_oom_recover(struct mem_cgroup *memcg)
 {
     /*
      * For the following lockless ->under_oom test, the only required
      * guarantee is that it must see the state asserted by an OOM when
      * this function is called as a result of userland actions
      * triggered by the notification of the OOM.  This is trivially
      * achieved by invoking mem_cgroup_mark_under_oom() before
      * triggering notification.
      */
     if (memcg && memcg->under_oom)
         __wake_up(&memcg_oom_waitq, TASK_NORMAL, 0, memcg);
 }
 
 /*
  * 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);
 
     /*
      * We are in the middle of the charge context here, so we
      * don't want to block when potentially sitting on a callstack
      * that holds all kinds of filesystem and mm locks.
      *
      * cgroup1 allows disabling the OOM killer and waiting for outside
      * handling until the charge can succeed; remember the context and put
      * the task to sleep at the end of the page fault when all locks are
      * released.
      *
      * On the other hand, in-kernel OOM killer allows for an async victim
      * memory reclaim (oom_reaper) and that means that we are not solely
      * relying on the oom victim to make a forward progress and we can
      * invoke the oom killer here.
      *
      * Please note that mem_cgroup_out_of_memory might fail to find a
      * victim and then we have to bail out from the charge path.
      */
     if (memcg->oom_kill_disable) {
         if (current->in_user_fault) {
             css_get(&memcg->css);
             current->memcg_in_oom = memcg;
             current->memcg_oom_gfp_mask = mask;
             current->memcg_oom_order = order;
         }
         return false;
     }
 
     mem_cgroup_mark_under_oom(memcg);
 
     locked = mem_cgroup_oom_trylock(memcg);
 
     if (locked)
         mem_cgroup_oom_notify(memcg);
 
     mem_cgroup_unmark_under_oom(memcg);
     ret = mem_cgroup_out_of_memory(memcg, mask, order);
 
     if (locked)
         mem_cgroup_oom_unlock(memcg);
 
     return ret;
 }
 
 /**
  * mem_cgroup_oom_synchronize - complete memcg OOM handling
  * @handle: actually kill/wait or just clean up the OOM state
  *
  * This has to be called at the end of a page fault if the memcg OOM
  * handler was enabled.
  *
  * Memcg supports userspace OOM handling where failed allocations must
  * sleep on a waitqueue until the userspace task resolves the
  * situation.  Sleeping directly in the charge context with all kinds
  * of locks held is not a good idea, instead we remember an OOM state
  * in the task and mem_cgroup_oom_synchronize() has to be called at
  * the end of the page fault to complete the OOM handling.
  *
  * Returns %true if an ongoing memcg OOM situation was detected and
  * completed, %false otherwise.
  */
 bool mem_cgroup_oom_synchronize(bool handle)
 {
     struct mem_cgroup *memcg = current->memcg_in_oom;
     struct oom_wait_info owait;
     bool locked;
 
     /* OOM is global, do not handle */
     if (!memcg)
         return false;
 
     if (!handle)
         goto cleanup;
 
     owait.memcg = memcg;
     owait.wait.flags = 0;
     owait.wait.func = memcg_oom_wake_function;
     owait.wait.private = current;
     INIT_LIST_HEAD(&owait.wait.entry);
 
     prepare_to_wait(&memcg_oom_waitq, &owait.wait, TASK_KILLABLE);
     mem_cgroup_mark_under_oom(memcg);
 
     locked = mem_cgroup_oom_trylock(memcg);
 
     if (locked)
         mem_cgroup_oom_notify(memcg);
 
     if (locked && !memcg->oom_kill_disable) {
         mem_cgroup_unmark_under_oom(memcg);
         finish_wait(&memcg_oom_waitq, &owait.wait);
         mem_cgroup_out_of_memory(memcg, current->memcg_oom_gfp_mask,
                      current->memcg_oom_order);
     } else {
         schedule();
         mem_cgroup_unmark_under_oom(memcg);
         finish_wait(&memcg_oom_waitq, &owait.wait);
     }
 
     if (locked) {
         mem_cgroup_oom_unlock(memcg);
         /*
          * There is no guarantee that an OOM-lock contender
          * sees the wakeups triggered by the OOM kill
          * uncharges.  Wake any sleepers explicitly.
          */
         memcg_oom_recover(memcg);
     }
 cleanup:
     current->memcg_in_oom = NULL;
     css_put(&memcg->css);
     return true;
 }
 
 /**
  * mem_cgroup_get_oom_group - get a memory cgroup to clean up after OOM
  * @victim: task to be killed by the OOM killer
  * @oom_domain: memcg in case of memcg OOM, NULL in case of system-wide OOM
  *
  * Returns a pointer to a memory cgroup, which has to be cleaned up
  * by killing all belonging OOM-killable tasks.
  *
  * Caller has to call mem_cgroup_put() on the returned non-NULL memcg.
  */
 struct mem_cgroup *mem_cgroup_get_oom_group(struct task_struct *victim,
                         struct mem_cgroup *oom_domain)
 {
     struct mem_cgroup *oom_group = NULL;
     struct mem_cgroup *memcg;
 
     if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
         return NULL;
 
     if (!oom_domain)
         oom_domain = root_mem_cgroup;
 
     rcu_read_lock();
 
     memcg = mem_cgroup_from_task(victim);
     if (memcg == root_mem_cgroup)
         goto out;
 
     /*
      * If the victim task has been asynchronously moved to a different
      * memory cgroup, we might end up killing tasks outside oom_domain.
      * In this case it's better to ignore memory.group.oom.
      */
     if (unlikely(!mem_cgroup_is_descendant(memcg, oom_domain)))
         goto out;
 
     /*
      * Traverse the memory cgroup hierarchy from the victim task's
      * cgroup up to the OOMing cgroup (or root) to find the
      * highest-level memory cgroup with oom.group set.
      */
     for (; memcg; memcg = parent_mem_cgroup(memcg)) {
         if (memcg->oom_group)
             oom_group = memcg;
 
         if (memcg == oom_domain)
             break;
     }
 
     if (oom_group)
         css_get(&oom_group->css);
 out:
     rcu_read_unlock();
 
     return oom_group;
 }
 
 void mem_cgroup_print_oom_group(struct mem_cgroup *memcg)
 {
     pr_info("Tasks in ");
     pr_cont_cgroup_path(memcg->css.cgroup);
     pr_cont(" are going to be killed due to memory.oom.group set\n");
 }
 
 /**
  * folio_memcg_lock - Bind a folio to its memcg.
  * @folio: The folio.
  *
  * This function prevents unlocked LRU folios from being moved to
  * another cgroup.
  *
  * It ensures lifetime of the bound memcg.  The caller is responsible
  * for the lifetime of the folio.
  */
 void folio_memcg_lock(struct folio *folio)
 {
     struct mem_cgroup *memcg;
     unsigned long flags;
 
     /*
      * The RCU lock is held throughout the transaction.  The fast
      * path can get away without acquiring the memcg->move_lock
      * because page moving starts with an RCU grace period.
          */
     rcu_read_lock();
 
     if (mem_cgroup_disabled())
         return;
 again:
     memcg = folio_memcg(folio);
     if (unlikely(!memcg))
         return;
 
 #ifdef CONFIG_PROVE_LOCKING
     local_irq_save(flags);
     might_lock(&memcg->move_lock);
     local_irq_restore(flags);
 #endif
 
     if (atomic_read(&memcg->moving_account) <= 0)
         return;
 
     spin_lock_irqsave(&memcg->move_lock, flags);
     if (memcg != folio_memcg(folio)) {
         spin_unlock_irqrestore(&memcg->move_lock, flags);
         goto again;
     }
 
     /*
      * When charge migration first begins, we can have multiple
      * critical sections holding the fast-path RCU lock and one
      * holding the slowpath move_lock. Track the task who has the
      * move_lock for unlock_page_memcg().
      */
     memcg->move_lock_task = current;
     memcg->move_lock_flags = flags;
 }
 
 void lock_page_memcg(struct page *page)
 {
     folio_memcg_lock(page_folio(page));
 }
 
 static void __folio_memcg_unlock(struct mem_cgroup *memcg)
 {
     if (memcg && memcg->move_lock_task == current) {
         unsigned long flags = memcg->move_lock_flags;
 
         memcg->move_lock_task = NULL;
         memcg->move_lock_flags = 0;
 
         spin_unlock_irqrestore(&memcg->move_lock, flags);
     }
 
     rcu_read_unlock();
 }
 
 /**
  * folio_memcg_unlock - Release the binding between a folio and its memcg.
  * @folio: The folio.
  *
  * This releases the binding created by folio_memcg_lock().  This does
  * not change the accounting of this folio to its memcg, but it does
  * permit others to change it.
  */
 void folio_memcg_unlock(struct folio *folio)
 {
     __folio_memcg_unlock(folio_memcg(folio));
 }
 
 void unlock_page_memcg(struct page *page)
 {
     folio_memcg_unlock(page_folio(page));
 }
 
 struct memcg_stock_pcp {
     local_lock_t stock_lock;
     struct mem_cgroup *cached; /* this never be root cgroup */
     unsigned int nr_pages;
 
 #ifdef CONFIG_MEMCG_KMEM
     struct obj_cgroup *cached_objcg;
     struct pglist_data *cached_pgdat;
     unsigned int nr_bytes;
     int nr_slab_reclaimable_b;
     int nr_slab_unreclaimable_b;
 #endif
 
     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);
 
 #ifdef CONFIG_MEMCG_KMEM
 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);
 static void memcg_account_kmem(struct mem_cgroup *memcg, int nr_pages);
 
 #else
 static inline struct obj_cgroup *drain_obj_stock(struct memcg_stock_pcp *stock)
 {
     return NULL;
 }
 static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
                      struct mem_cgroup *root_memcg)
 {
     return false;
 }
 static void memcg_account_kmem(struct mem_cgroup *memcg, int nr_pages)
 {
 }
 #endif
 
 /**
  * consume_stock: Try to consume stocked charge on this cpu.
  * @memcg: memcg to consume from.
  * @nr_pages: how many pages to charge.
  *
  * The charges will only happen if @memcg matches the current cpu's memcg
  * stock, and at least @nr_pages are available in that stock.  Failure to
  * service an allocation will refill the stock.
  *
  * returns true if successful, false otherwise.
  */
 static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
     struct memcg_stock_pcp *stock;
     unsigned long flags;
     bool ret = false;
 
     if (nr_pages > MEMCG_CHARGE_BATCH)
         return ret;
 
     local_lock_irqsave(&memcg_stock.stock_lock, flags);
 
     stock = this_cpu_ptr(&memcg_stock);
     if (memcg == stock->cached && stock->nr_pages >= nr_pages) {
         stock->nr_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)
 {
     struct mem_cgroup *old = stock->cached;
 
     if (!old)
         return;
 
     if (stock->nr_pages) {
         page_counter_uncharge(&old->memory, stock->nr_pages);
         if (do_memsw_account())
             page_counter_uncharge(&old->memsw, stock->nr_pages);
         stock->nr_pages = 0;
     }
 
     css_put(&old->css);
     stock->cached = NULL;
 }
 
 static void drain_local_stock(struct work_struct *dummy)
 {
     struct memcg_stock_pcp *stock;
     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);
     if (old)
         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;
 
     stock = this_cpu_ptr(&memcg_stock);
     if (stock->cached != memcg) { /* reset if necessary */
         drain_stock(stock);
         css_get(&memcg->css);
         stock->cached = memcg;
     }
     stock->nr_pages += nr_pages;
 
     if (stock->nr_pages > MEMCG_CHARGE_BATCH)
         drain_stock(stock);
 }
 
 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.
  */
 static void drain_all_stock(struct mem_cgroup *root_memcg)
 {
     int cpu, curcpu;
 
     /* If someone's already draining, avoid adding running more workers. */
     if (!mutex_trylock(&percpu_charge_mutex))
         return;
     /*
      * Notify other cpus that system-wide "drain" is running
      * We do not care about races with the cpu hotplug because cpu down
      * as well as workers from this path always operate on the local
      * per-cpu data. CPU up doesn't touch memcg_stock at all.
      */
     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 = stock->cached;
         if (memcg && 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
                 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);
         psi_memstall_leave(&pflags);
     } while ((memcg = parent_mem_cgroup(memcg)) &&
          !mem_cgroup_is_root(memcg));
 
     return nr_reclaimed;
 }
 
 static void high_work_func(struct work_struct *work)
 {
     struct mem_cgroup *memcg;
 
     memcg = container_of(work, struct mem_cgroup, high_work);
     reclaim_high(memcg, MEMCG_CHARGE_BATCH, GFP_KERNEL);
 }
 
 /*
  * Clamp the maximum sleep time per allocation batch to 2 seconds. This is
  * enough to still cause a significant slowdown in most cases, while still
  * allowing diagnostics and tracing to proceed without becoming stuck.
  */
 #define MEMCG_MAX_HIGH_DELAY_JIFFIES (2UL*HZ)
 
 /*
  * When calculating the delay, we use these either side of the exponentiation to
  * maintain precision and scale to a reasonable number of jiffies (see the table
  * below.
  *
  * - MEMCG_DELAY_PRECISION_SHIFT: Extra precision bits while translating the
  *   overage ratio to a delay.
  * - MEMCG_DELAY_SCALING_SHIFT: The number of bits to scale down the
  *   proposed penalty in order to reduce to a reasonable number of jiffies, and
  *   to produce a reasonable delay curve.
  *
  * MEMCG_DELAY_SCALING_SHIFT just happens to be a number that produces a
  * reasonable delay curve compared to precision-adjusted overage, not
  * penalising heavily at first, but still making sure that growth beyond the
  * limit penalises misbehaviour cgroups by slowing them down exponentially. For
  * example, with a high of 100 megabytes:
  *
  *  +-------+------------------------+
  *  | usage | time to allocate in ms |
  *  +-------+------------------------+
  *  | 100M  |                      0 |
  *  | 101M  |                      6 |
  *  | 102M  |                     25 |
  *  | 103M  |                     57 |
  *  | 104M  |                    102 |
  *  | 105M  |                    159 |
  *  | 106M  |                    230 |
  *  | 107M  |                    313 |
  *  | 108M  |                    409 |
  *  | 109M  |                    518 |
  *  | 110M  |                    639 |
  *  | 111M  |                    774 |
  *  | 112M  |                    921 |
  *  | 113M  |                   1081 |
  *  | 114M  |                   1254 |
  *  | 115M  |                   1439 |
  *  | 116M  |                   1638 |
  *  | 117M  |                   1849 |
  *  | 118M  |                   2000 |
  *  | 119M  |                   2000 |
  *  | 120M  |                   2000 |
  *  +-------+------------------------+
  */
  #define MEMCG_DELAY_PRECISION_SHIFT 20
  #define MEMCG_DELAY_SCALING_SHIFT 14
 
 static u64 calculate_overage(unsigned long usage, unsigned long high)
 {
     u64 overage;
 
     if (usage <= high)
         return 0;
 
     /*
      * Prevent division by 0 in overage calculation by acting as if
      * it was a threshold of 1 page
      */
     high = max(high, 1UL);
 
     overage = usage - high;
     overage <<= MEMCG_DELAY_PRECISION_SHIFT;
     return div64_u64(overage, high);
 }
 
 static u64 mem_find_max_overage(struct mem_cgroup *memcg)
 {
     u64 overage, max_overage = 0;
 
     do {
         overage = calculate_overage(page_counter_read(&memcg->memory),
                         READ_ONCE(memcg->memory.high));
         max_overage = max(overage, max_overage);
     } while ((memcg = parent_mem_cgroup(memcg)) &&
          !mem_cgroup_is_root(memcg));
 
     return max_overage;
 }
 
 static u64 swap_find_max_overage(struct mem_cgroup *memcg)
 {
     u64 overage, max_overage = 0;
 
     do {
         overage = calculate_overage(page_counter_read(&memcg->swap),
                         READ_ONCE(memcg->swap.high));
         if (overage)
             memcg_memory_event(memcg, MEMCG_SWAP_HIGH);
         max_overage = max(overage, max_overage);
     } while ((memcg = parent_mem_cgroup(memcg)) &&
          !mem_cgroup_is_root(memcg));
 
     return max_overage;
 }
 
 /*
  * Get the number of jiffies that we should penalise a mischievous cgroup which
  * is exceeding its memory.high by checking both it and its ancestors.
  */
 static unsigned long calculate_high_delay(struct mem_cgroup *memcg,
                       unsigned int nr_pages,
                       u64 max_overage)
 {
     unsigned long penalty_jiffies;
 
     if (!max_overage)
         return 0;
 
     /*
      * We use overage compared to memory.high to calculate the number of
      * jiffies to sleep (penalty_jiffies). Ideally this value should be
      * fairly lenient on small overages, and increasingly harsh when the
      * memcg in question makes it clear that it has no intention of stopping
      * its crazy behaviour, so we exponentially increase the delay based on
      * overage amount.
      */
     penalty_jiffies = max_overage * max_overage * HZ;
     penalty_jiffies >>= MEMCG_DELAY_PRECISION_SHIFT;
     penalty_jiffies >>= MEMCG_DELAY_SCALING_SHIFT;
 
     /*
      * Factor in the task's own contribution to the overage, such that four
      * N-sized allocations are throttled approximately the same as one
      * 4N-sized allocation.
      *
      * MEMCG_CHARGE_BATCH pages is nominal, so work out how much smaller or
      * larger the current charge patch is than that.
      */
     return penalty_jiffies * nr_pages / MEMCG_CHARGE_BATCH;
 }
 
 /*
  * Scheduled by try_charge() to be executed from the userland return path
  * and reclaims memory over the high limit.
  */
 void mem_cgroup_handle_over_high(void)
 {
     unsigned long penalty_jiffies;
     unsigned long pflags;
     unsigned long nr_reclaimed;
     unsigned int nr_pages = current->memcg_nr_pages_over_high;
     int nr_retries = MAX_RECLAIM_RETRIES;
     struct mem_cgroup *memcg;
     bool in_retry = false;
 
     if (likely(!nr_pages))
         return;
 
     memcg = get_mem_cgroup_from_mm(current->mm);
     current->memcg_nr_pages_over_high = 0;
 
 retry_reclaim:
     /*
      * The allocating task should reclaim at least the batch size, but for
      * subsequent retries we only want to do what's necessary to prevent oom
      * or breaching resource isolation.
      *
      * This is distinct from memory.max or page allocator behaviour because
      * memory.high is currently batched, whereas memory.max and the page
      * allocator run every time an allocation is made.
      */
     nr_reclaimed = reclaim_high(memcg,
                     in_retry ? SWAP_CLUSTER_MAX : nr_pages,
                     GFP_KERNEL);
 
     /*
      * memory.high is breached and reclaim is unable to keep up. Throttle
      * allocators proactively to slow down excessive growth.
      */
     penalty_jiffies = calculate_high_delay(memcg, nr_pages,
                            mem_find_max_overage(memcg));
 
     penalty_jiffies += calculate_high_delay(memcg, nr_pages,
                         swap_find_max_overage(memcg));
 
     /*
      * Clamp the max delay per usermode return so as to still keep the
      * application moving forwards and also permit diagnostics, albeit
      * extremely slowly.
      */
     penalty_jiffies = min(penalty_jiffies, MEMCG_MAX_HIGH_DELAY_JIFFIES);
 
     /*
      * Don't sleep if the amount of jiffies this memcg owes us is so low
      * that it's not even worth doing, in an attempt to be nice to those who
      * go only a small amount over their memory.high value and maybe haven't
      * been aggressively reclaimed enough yet.
      */
     if (penalty_jiffies <= HZ / 100)
         goto out;
 
     /*
      * If reclaim is making forward progress but we're still over
      * memory.high, we want to encourage that rather than doing allocator
      * throttling.
      */
     if (nr_reclaimed || nr_retries--) {
         in_retry = true;
         goto retry_reclaim;
     }
 
     /*
      * If we exit early, we're guaranteed to die (since
      * schedule_timeout_killable sets TASK_KILLABLE). This means we don't
      * need to account for any ill-begotten jiffies to pay them off later.
      */
     psi_memstall_enter(&pflags);
     schedule_timeout_killable(penalty_jiffies);
     psi_memstall_leave(&pflags);
 
 out:
     css_put(&memcg->css);
 }
 
 static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
             unsigned int nr_pages)
 {
     unsigned int batch = max(MEMCG_CHARGE_BATCH, nr_pages);
     int nr_retries = MAX_RECLAIM_RETRIES;
     struct mem_cgroup *mem_over_limit;
     struct page_counter *counter;
     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);
     psi_memstall_leave(&pflags);
 
     if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
         goto retry;
 
     if (!drained) {
         drain_all_stock(mem_over_limit);
         drained = true;
         goto retry;
     }
 
     if (gfp_mask & __GFP_NORETRY)
         goto nomem;
     /*
      * Even though the limit is exceeded at this point, reclaim
      * may have been able to free some pages.  Retry the charge
      * before killing the task.
      *
      * Only for regular pages, though: huge pages are rather
      * unlikely to succeed so close to the limit, and we fall back
      * to regular pages anyway in case of failure.
      */
     if (nr_reclaimed && nr_pages <= (1 << PAGE_ALLOC_COSTLY_ORDER))
         goto retry;
     /*
      * At task move, charge accounts can be doubly counted. So, it's
      * better to wait until the end of task_move if something is going on.
      */
     if (mem_cgroup_wait_acct_move(mem_over_limit))
         goto retry;
 
     if (nr_retries--)
         goto retry;
 
     if (gfp_mask & __GFP_RETRY_MAYFAIL)
         goto nomem;
 
     /* 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)));
 
     if (current->memcg_nr_pages_over_high > MEMCG_CHARGE_BATCH &&
         !(current->flags & PF_MEMALLOC) &&
         gfpflags_allow_blocking(gfp_mask)) {
         mem_cgroup_handle_over_high();
     }
     return 0;
 }
 
 static inline int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
                  unsigned int nr_pages)
 {
     if (mem_cgroup_is_root(memcg))
         return 0;
 
     return try_charge_memcg(memcg, gfp_mask, nr_pages);
 }
 
 static inline void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
 {
     if (mem_cgroup_is_root(memcg))
         return;
 
     page_counter_uncharge(&memcg->memory, nr_pages);
     if (do_memsw_account())
         page_counter_uncharge(&memcg->memsw, nr_pages);
 }
 
 static void commit_charge(struct folio *folio, struct mem_cgroup *memcg)
 {
     VM_BUG_ON_FOLIO(folio_memcg(folio), folio);
     /*
      * Any of the following ensures page's memcg stability:
      *
      * - the page lock
      * - LRU isolation
      * - lock_page_memcg()
      * - exclusive reference
      */
     folio->memcg_data = (unsigned long)memcg;
 }
 
 #ifdef CONFIG_MEMCG_KMEM
 /*
  * The allocated objcg pointers array is not accounted directly.
  * Moreover, it should not come from DMA buffer and is not readily
  * reclaimable. So those GFP bits should be masked off.
  */
 #define OBJCGS_CLEAR_MASK   (__GFP_DMA | __GFP_RECLAIMABLE | __GFP_ACCOUNT)
 
 /*
  * mod_objcg_mlstate() may be called with irq enabled, so
  * mod_memcg_lruvec_state() should be used.
  */
 static inline void mod_objcg_mlstate(struct obj_cgroup *objcg,
                      struct pglist_data *pgdat,
                      enum node_stat_item idx, int nr)
 {
     struct mem_cgroup *memcg;
     struct lruvec *lruvec;
 
     rcu_read_lock();
     memcg = obj_cgroup_memcg(objcg);
     lruvec = mem_cgroup_lruvec(memcg, pgdat);
     mod_memcg_lruvec_state(lruvec, idx, nr);
     rcu_read_unlock();
 }
 
 int memcg_alloc_slab_cgroups(struct slab *slab, struct kmem_cache *s,
                  gfp_t gfp, bool new_slab)
 {
     unsigned int objects = objs_per_slab(s, slab);
     unsigned long memcg_data;
     void *vec;
 
     gfp &= ~OBJCGS_CLEAR_MASK;
     vec = kcalloc_node(objects, sizeof(struct obj_cgroup *), gfp,
                slab_nid(slab));
     if (!vec)
         return -ENOMEM;
 
     memcg_data = (unsigned long) vec | MEMCG_DATA_OBJCGS;
     if (new_slab) {
         /*
          * If the slab is brand new and nobody can yet access its
          * memcg_data, no synchronization is required and memcg_data can
          * be simply assigned.
          */
         slab->memcg_data = memcg_data;
     } else if (cmpxchg(&slab->memcg_data, 0, memcg_data)) {
         /*
          * If the slab is already in use, somebody can allocate and
          * assign obj_cgroups in parallel. In this case the existing
          * objcg vector should be reused.
          */
         kfree(vec);
         return 0;
     }
 
     kmemleak_not_leak(vec);
     return 0;
 }
 
 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->memcg_data.
      */
     if (folio_test_slab(folio)) {
         struct obj_cgroup **objcgs;
         struct slab *slab;
         unsigned int off;
 
         slab = folio_slab(folio);
         objcgs = slab_objcgs(slab);
         if (!objcgs)
             return NULL;
 
         off = obj_to_index(slab->slab_cache, slab, p);
         if (objcgs[off])
             return obj_cgroup_memcg(objcgs[off]);
 
         return NULL;
     }
 
     /*
      * page_memcg_check() is used here, because in theory we can encounter
      * a folio where the slab flag has been cleared already, but
      * slab->memcg_data has not been freed yet
      * page_memcg_check(page) will guarantee that a proper memory
      * cgroup pointer or NULL will be returned.
      */
     return page_memcg_check(folio_page(folio, 0));
 }
 
 /*
  * Returns a pointer to the memory cgroup to which the kernel object is charged.
  *
  * A passed kernel object can be a slab object, vmalloc object or a generic
  * kernel page, so different mechanisms for getting the memory cgroup pointer
  * should be used.
  *
  * In certain cases (e.g. kernel stacks or large kmallocs with SLUB) the caller
  * can not know for sure how the kernel object is implemented.
  * mem_cgroup_from_obj() can be safely used in such cases.
  *
  * The caller must ensure the memcg lifetime, e.g. by taking rcu_read_lock(),
  * cgroup_mutex, etc.
  */
 struct mem_cgroup *mem_cgroup_from_obj(void *p)
 {
     struct folio *folio;
 
     if (mem_cgroup_disabled())
         return NULL;
 
     if (unlikely(is_vmalloc_addr(p)))
         folio = page_folio(vmalloc_to_page(p));
     else
         folio = virt_to_folio(p);
 
     return mem_cgroup_from_obj_folio(folio, p);
 }
 
 /*
  * Returns a pointer to the memory cgroup to which the kernel object is charged.
  * Similar to mem_cgroup_from_obj(), but faster and 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 (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) {
         objcg = rcu_dereference(memcg->objcg);
         if (objcg && obj_cgroup_tryget(objcg))
             break;
         objcg = NULL;
     }
     return objcg;
 }
 
 __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
 {
     struct obj_cgroup *objcg = NULL;
     struct mem_cgroup *memcg;
 
     if (memcg_kmem_bypass())
         return NULL;
 
     rcu_read_lock();
     if (unlikely(active_memcg()))
         memcg = active_memcg();
     else
         memcg = mem_cgroup_from_task(current);
     objcg = __get_obj_cgroup_from_memcg(memcg);
     rcu_read_unlock();
     return objcg;
 }
 
 struct obj_cgroup *get_obj_cgroup_from_page(struct page *page)
 {
     struct obj_cgroup *objcg;
 
     if (!memcg_kmem_enabled() || memcg_kmem_bypass())
         return NULL;
 
     if (PageMemcgKmem(page)) {
         objcg = __folio_objcg(page_folio(page));
         obj_cgroup_get(objcg);
     } else {
         struct mem_cgroup *memcg;
 
         rcu_read_lock();
         memcg = __folio_memcg(page_folio(page));
         if (memcg)
             objcg = __get_obj_cgroup_from_memcg(memcg);
         else
             objcg = NULL;
         rcu_read_unlock();
     }
     return objcg;
 }
 
 static void memcg_account_kmem(struct mem_cgroup *memcg, int nr_pages)
 {
     mod_memcg_state(memcg, MEMCG_KMEM, nr_pages);
     if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
         if (nr_pages > 0)
             page_counter_charge(&memcg->kmem, nr_pages);
         else
             page_counter_uncharge(&memcg->kmem, -nr_pages);
     }
 }
 
 
 /*
  * 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);
 
     memcg_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;
 
     memcg_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 = get_obj_cgroup_from_current();
     if (objcg) {
         ret = obj_cgroup_charge_pages(objcg, gfp, 1 << order);
         if (!ret) {
             page->memcg_data = (unsigned long)objcg |
                 MEMCG_DATA_KMEM;
             return 0;
         }
         obj_cgroup_put(objcg);
     }
     return ret;
 }
 
 /**
  * __memcg_kmem_uncharge_page: uncharge a kmem page
  * @page: page to uncharge
  * @order: allocation order
  */
 void __memcg_kmem_uncharge_page(struct page *page, int order)
 {
     struct 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);
 }
 
 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 (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;
         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);
     if (old)
         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 == 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 = 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);
 
             memcg_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;
     }
 
     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 mem_cgroup *memcg;
 
     if (stock->cached_objcg) {
         memcg = obj_cgroup_memcg(stock->cached_objcg);
         if (memcg && mem_cgroup_is_descendant(memcg, root_memcg))
             return true;
     }
 
     return false;
 }
 
 static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
                  bool allow_uncharge)
 {
     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 (stock->cached_objcg != objcg) { /* reset if necessary */
         old = drain_obj_stock(stock);
         obj_cgroup_get(objcg);
         stock->cached_objcg = objcg;
         stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes)
                 ? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0;
         allow_uncharge = true;  /* Allow uncharge when objcg changes */
     }
     stock->nr_bytes += nr_bytes;
 
     if (allow_uncharge && (stock->nr_bytes > PAGE_SIZE)) {
         nr_pages = stock->nr_bytes >> PAGE_SHIFT;
         stock->nr_bytes &= (PAGE_SIZE - 1);
     }
 
     local_unlock_irqrestore(&memcg_stock.stock_lock, flags);
     if (old)
         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);
 }
 
 #endif /* CONFIG_MEMCG_KMEM */
 
 /*
  * Because page_memcg(head) is not set on tails, set it now.
  */
 void split_page_memcg(struct page *head, unsigned int nr)
 {
     struct folio *folio = page_folio(head);
     struct mem_cgroup *memcg = folio_memcg(folio);
     int i;
 
     if (mem_cgroup_disabled() || !memcg)
         return;
 
     for (i = 1; i < nr; i++)
         folio_page(folio, i)->memcg_data = folio->memcg_data;
 
     if (folio_memcg_kmem(folio))
         obj_cgroup_get_many(__folio_objcg(folio), nr - 1);
     else
         css_get_many(&memcg->css, nr - 1);
 }
 
 #ifdef CONFIG_MEMCG_SWAP
 /**
  * mem_cgroup_move_swap_account - move swap charge and swap_cgroup's record.
  * @entry: swap entry to be moved
  * @from:  mem_cgroup which the entry is moved from
  * @to:  mem_cgroup which the entry is moved to
  *
  * It succeeds only when the swap_cgroup's record for this entry is the same
  * as the mem_cgroup's id of @from.
  *
  * Returns 0 on success, -EINVAL on failure.
  *
  * The caller must have charged to @to, IOW, called page_counter_charge() about
  * both res and memsw, and called css_get().
  */
 static int mem_cgroup_move_swap_account(swp_entry_t entry,
                 struct mem_cgroup *from, struct mem_cgroup *to)
 {
     unsigned short old_id, new_id;
 
     old_id = mem_cgroup_id(from);
     new_id = mem_cgroup_id(to);
 
     if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
         mod_memcg_state(from, MEMCG_SWAP, -1);
         mod_memcg_state(to, MEMCG_SWAP, 1);
         return 0;
     }
     return -EINVAL;
 }
 #else
 static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
                 struct mem_cgroup *from, struct mem_cgroup *to)
 {
     return -EINVAL;
 }
 #endif
 
 static DEFINE_MUTEX(memcg_max_mutex);
 
 static int mem_cgroup_resize_max(struct mem_cgroup *memcg,
                  unsigned long max, bool memsw)
 {
     bool enlarge = false;
     bool drained = false;
     int ret;
     bool limits_invariant;
     struct page_counter *counter = memsw ? &memcg->memsw : &memcg->memory;
 
     do {
         if (signal_pending(current)) {
             ret = -EINTR;
             break;
         }
 
         mutex_lock(&memcg_max_mutex);
         /*
          * Make sure that the new limit (memsw or memory limit) doesn't
          * break our basic invariant rule memory.max <= memsw.max.
          */
         limits_invariant = memsw ? max >= READ_ONCE(memcg->memory.max) :
                        max <= memcg->memsw.max;
         if (!limits_invariant) {
             mutex_unlock(&memcg_max_mutex);
             ret = -EINVAL;
             break;
         }
         if (max > counter->max)
             enlarge = true;
         ret = page_counter_set_max(counter, max);
         mutex_unlock(&memcg_max_mutex);
 
         if (!ret)
             break;
 
         if (!drained) {
             drain_all_stock(memcg);
             drained = true;
             continue;
         }
 
         if (!try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL,
                     memsw ? 0 : MEMCG_RECLAIM_MAY_SWAP)) {
             ret = -EBUSY;
             break;
         }
     } while (true);
 
     if (!ret && enlarge)
         memcg_oom_recover(memcg);
 
     return ret;
 }
 
 unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
                         gfp_t gfp_mask,
                         unsigned long *total_scanned)
 {
     unsigned long nr_reclaimed = 0;
     struct mem_cgroup_per_node *mz, *next_mz = NULL;
     unsigned long reclaimed;
     int loop = 0;
     struct mem_cgroup_tree_per_node *mctz;
     unsigned long excess;
 
     if (order > 0)
         return 0;
 
     mctz = soft_limit_tree.rb_tree_per_node[pgdat->node_id];
 
     /*
      * Do not even bother to check the largest node if the root
      * is empty. Do it lockless to prevent lock bouncing. Races
      * are acceptable as soft limit is best effort anyway.
      */
     if (!mctz || RB_EMPTY_ROOT(&mctz->rb_root))
         return 0;
 
     /*
      * This loop can run a while, specially if mem_cgroup's continuously
      * keep exceeding their soft limit and putting the system under
      * pressure
      */
     do {
         if (next_mz)
             mz = next_mz;
         else
             mz = mem_cgroup_largest_soft_limit_node(mctz);
         if (!mz)
             break;
 
         reclaimed = mem_cgroup_soft_reclaim(mz->memcg, pgdat,
                             gfp_mask, total_scanned);
         nr_reclaimed += reclaimed;
         spin_lock_irq(&mctz->lock);
 
         /*
          * If we failed to reclaim anything from this memory cgroup
          * it is time to move on to the next cgroup
          */
         next_mz = NULL;
         if (!reclaimed)
             next_mz = __mem_cgroup_largest_soft_limit_node(mctz);
 
         excess = soft_limit_excess(mz->memcg);
         /*
          * One school of thought says that we should not add
          * back the node to the tree if reclaim returns 0.
          * But our reclaim could return 0, simply because due
          * to priority we are exposing a smaller subset of
          * memory to reclaim from. Consider this as a longer
          * term TODO.
          */
         /* If excess == 0, no tree ops */
         __mem_cgroup_insert_exceeded(mz, mctz, excess);
         spin_unlock_irq(&mctz->lock);
         css_put(&mz->memcg->css);
         loop++;
         /*
          * Could not reclaim anything and there are no more
          * mem cgroups to try or we seem to be looping without
          * reclaiming anything.
          */
         if (!nr_reclaimed &&
             (next_mz == NULL ||
             loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
             break;
     } while (!nr_reclaimed);
     if (next_mz)
         css_put(&next_mz->memcg->css);
     return nr_reclaimed;
 }
 
 /*
  * Reclaims as many pages from the given memcg as possible.
  *
  * Caller is responsible for holding css reference for memcg.
  */
 static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
 {
     int nr_retries = MAX_RECLAIM_RETRIES;
 
     /* we call try-to-free pages for make this cgroup empty */
     lru_add_drain_all();
 
     drain_all_stock(memcg);
 
     /* try to free all pages in this cgroup */
     while (nr_retries && page_counter_read(&memcg->memory)) {
         if (signal_pending(current))
             return -EINTR;
 
         if (!try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL,
                           MEMCG_RECLAIM_MAY_SWAP))
             nr_retries--;
     }
 
     return 0;
 }
 
 static ssize_t mem_cgroup_force_empty_write(struct kernfs_open_file *of,
                         char *buf, size_t nbytes,
                         loff_t off)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
 
     if (mem_cgroup_is_root(memcg))
         return -EINVAL;
     return mem_cgroup_force_empty(memcg) ?: nbytes;
 }
 
 static u64 mem_cgroup_hierarchy_read(struct cgroup_subsys_state *css,
                      struct cftype *cft)
 {
     return 1;
 }
 
 static int mem_cgroup_hierarchy_write(struct cgroup_subsys_state *css,
                       struct cftype *cft, u64 val)
 {
     if (val == 1)
         return 0;
 
     pr_warn_once("Non-hierarchical mode is deprecated. "
              "Please report your usecase to linux-mm@kvack.org if you "
              "depend on this functionality.\n");
 
     return -EINVAL;
 }
 
 static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
 {
     unsigned long val;
 
     if (mem_cgroup_is_root(memcg)) {
         mem_cgroup_flush_stats();
         val = memcg_page_state(memcg, NR_FILE_PAGES) +
             memcg_page_state(memcg, NR_ANON_MAPPED);
         if (swap)
             val += memcg_page_state(memcg, MEMCG_SWAP);
     } else {
         if (!swap)
             val = page_counter_read(&memcg->memory);
         else
             val = page_counter_read(&memcg->memsw);
     }
     return val;
 }
 
 enum {
     RES_USAGE,
     RES_LIMIT,
     RES_MAX_USAGE,
     RES_FAILCNT,
     RES_SOFT_LIMIT,
 };
 
 static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
                    struct cftype *cft)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_css(css);
     struct page_counter *counter;
 
     switch (MEMFILE_TYPE(cft->private)) {
     case _MEM:
         counter = &memcg->memory;
         break;
     case _MEMSWAP:
         counter = &memcg->memsw;
         break;
     case _KMEM:
         counter = &memcg->kmem;
         break;
     case _TCP:
         counter = &memcg->tcpmem;
         break;
     default:
         BUG();
     }
 
     switch (MEMFILE_ATTR(cft->private)) {
     case RES_USAGE:
         if (counter == &memcg->memory)
             return (u64)mem_cgroup_usage(memcg, false) * PAGE_SIZE;
         if (counter == &memcg->memsw)
             return (u64)mem_cgroup_usage(memcg, true) * PAGE_SIZE;
         return (u64)page_counter_read(counter) * PAGE_SIZE;
     case RES_LIMIT:
         return (u64)counter->max * PAGE_SIZE;
     case RES_MAX_USAGE:
         return (u64)counter->watermark * PAGE_SIZE;
     case RES_FAILCNT:
         return counter->failcnt;
     case RES_SOFT_LIMIT:
         return (u64)memcg->soft_limit * PAGE_SIZE;
     default:
         BUG();
     }
 }
 
 #ifdef CONFIG_MEMCG_KMEM
 static int memcg_online_kmem(struct mem_cgroup *memcg)
 {
     struct obj_cgroup *objcg;
 
     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);
 
     static_branch_enable(&memcg_kmem_enabled_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_objcgs(memcg, parent);
 
     /*
      * After we have finished memcg_reparent_objcgs(), all list_lrus
      * corresponding to this cgroup are guaranteed to remain empty.
      * The ordering is imposed by list_lru_node->lock taken by
      * memcg_reparent_list_lrus().
      */
     memcg_reparent_list_lrus(memcg, parent);
 }
 #else
 static int memcg_online_kmem(struct mem_cgroup *memcg)
 {
     return 0;
 }
 static void memcg_offline_kmem(struct mem_cgroup *memcg)
 {
 }
 #endif /* CONFIG_MEMCG_KMEM */
 
 static int memcg_update_tcp_max(struct mem_cgroup *memcg, unsigned long max)
 {
     int ret;
 
     mutex_lock(&memcg_max_mutex);
 
     ret = page_counter_set_max(&memcg->tcpmem, max);
     if (ret)
         goto out;
 
     if (!memcg->tcpmem_active) {
         /*
          * The active flag needs to be written after the static_key
          * update. This is what guarantees that the socket activation
          * function is the last one to run. See mem_cgroup_sk_alloc()
          * for details, and note that we don't mark any socket as
          * belonging to this memcg until that flag is up.
          *
          * We need to do this, because static_keys will span multiple
          * sites, but we can't control their order. If we mark a socket
          * as accounted, but the accounting functions are not patched in
          * yet, we'll lose accounting.
          *
          * We never race with the readers in mem_cgroup_sk_alloc(),
          * because when this value change, the code to process it is not
          * patched in yet.
          */
         static_branch_inc(&memcg_sockets_enabled_key);
         memcg->tcpmem_active = true;
     }
 out:
     mutex_unlock(&memcg_max_mutex);
     return ret;
 }
 
 /*
  * The user of this function is...
  * RES_LIMIT.
  */
 static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
                 char *buf, size_t nbytes, loff_t off)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
     unsigned long nr_pages;
     int ret;
 
     buf = strstrip(buf);
     ret = page_counter_memparse(buf, "-1", &nr_pages);
     if (ret)
         return ret;
 
     switch (MEMFILE_ATTR(of_cft(of)->private)) {
     case RES_LIMIT:
         if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
             ret = -EINVAL;
             break;
         }
         switch (MEMFILE_TYPE(of_cft(of)->private)) {
         case _MEM:
             ret = mem_cgroup_resize_max(memcg, nr_pages, false);
             break;
         case _MEMSWAP:
             ret = mem_cgroup_resize_max(memcg, nr_pages, true);
             break;
         case _KMEM:
             /* kmem.limit_in_bytes is deprecated. */
             ret = -EOPNOTSUPP;
             break;
         case _TCP:
             ret = memcg_update_tcp_max(memcg, nr_pages);
             break;
         }
         break;
     case RES_SOFT_LIMIT:
         if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
             ret = -EOPNOTSUPP;
         } else {
             memcg->soft_limit = nr_pages;
             ret = 0;
         }
         break;
     }
     return ret ?: nbytes;
 }
 
 static ssize_t mem_cgroup_reset(struct kernfs_open_file *of, char *buf,
                 size_t nbytes, loff_t off)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
     struct page_counter *counter;
 
     switch (MEMFILE_TYPE(of_cft(of)->private)) {
     case _MEM:
         counter = &memcg->memory;
         break;
     case _MEMSWAP:
         counter = &memcg->memsw;
         break;
     case _KMEM:
         counter = &memcg->kmem;
         break;
     case _TCP:
         counter = &memcg->tcpmem;
         break;
     default:
         BUG();
     }
 
     switch (MEMFILE_ATTR(of_cft(of)->private)) {
     case RES_MAX_USAGE:
         page_counter_reset_watermark(counter);
         break;
     case RES_FAILCNT:
         counter->failcnt = 0;
         break;
     default:
         BUG();
     }
 
     return nbytes;
 }
 
 static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state *css,
                     struct cftype *cft)
 {
     return mem_cgroup_from_css(css)->move_charge_at_immigrate;
 }
 
 #ifdef CONFIG_MMU
 static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
                     struct cftype *cft, u64 val)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
     if (val & ~MOVE_MASK)
         return -EINVAL;
 
     /*
      * No kind of locking is needed in here, because ->can_attach() will
      * check this value once in the beginning of the process, and then carry
      * on with stale data. This means that changes to this value will only
      * affect task migrations starting after the change.
      */
     memcg->move_charge_at_immigrate = val;
     return 0;
 }
 #else
 static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
                     struct cftype *cft, u64 val)
 {
     return -ENOSYS;
 }
 #endif
 
 #ifdef CONFIG_NUMA
 
 #define LRU_ALL_FILE (BIT(LRU_INACTIVE_FILE) | BIT(LRU_ACTIVE_FILE))
 #define LRU_ALL_ANON (BIT(LRU_INACTIVE_ANON) | BIT(LRU_ACTIVE_ANON))
 #define LRU_ALL      ((1 << NR_LRU_LISTS) - 1)
 
 static unsigned long mem_cgroup_node_nr_lru_pages(struct mem_cgroup *memcg,
                 int nid, unsigned int lru_mask, bool tree)
 {
     struct lruvec *lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(nid));
     unsigned long nr = 0;
     enum lru_list lru;
 
     VM_BUG_ON((unsigned)nid >= nr_node_ids);
 
     for_each_lru(lru) {
         if (!(BIT(lru) & lru_mask))
             continue;
         if (tree)
             nr += lruvec_page_state(lruvec, NR_LRU_BASE + lru);
         else
             nr += lruvec_page_state_local(lruvec, NR_LRU_BASE + lru);
     }
     return nr;
 }
 
 static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg,
                          unsigned int lru_mask,
                          bool tree)
 {
     unsigned long nr = 0;
     enum lru_list lru;
 
     for_each_lru(lru) {
         if (!(BIT(lru) & lru_mask))
             continue;
         if (tree)
             nr += memcg_page_state(memcg, NR_LRU_BASE + lru);
         else
             nr += memcg_page_state_local(memcg, NR_LRU_BASE + lru);
     }
     return nr;
 }
 
 static int memcg_numa_stat_show(struct seq_file *m, void *v)
 {
     struct numa_stat {
         const char *name;
         unsigned int lru_mask;
     };
 
     static const struct numa_stat stats[] = {
         { "total", LRU_ALL },
         { "file", LRU_ALL_FILE },
         { "anon", LRU_ALL_ANON },
         { "unevictable", BIT(LRU_UNEVICTABLE) },
     };
     const struct numa_stat *stat;
     int nid;
     struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
 
     mem_cgroup_flush_stats();
 
     for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
         seq_printf(m, "%s=%lu", stat->name,
                mem_cgroup_nr_lru_pages(memcg, stat->lru_mask,
                            false));
         for_each_node_state(nid, N_MEMORY)
             seq_printf(m, " N%d=%lu", nid,
                    mem_cgroup_node_nr_lru_pages(memcg, nid,
                             stat->lru_mask, false));
         seq_putc(m, '\n');
     }
 
     for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
 
         seq_printf(m, "hierarchical_%s=%lu", stat->name,
                mem_cgroup_nr_lru_pages(memcg, stat->lru_mask,
                            true));
         for_each_node_state(nid, N_MEMORY)
             seq_printf(m, " N%d=%lu", nid,
                    mem_cgroup_node_nr_lru_pages(memcg, nid,
                             stat->lru_mask, true));
         seq_putc(m, '\n');
     }
 
     return 0;
 }
 #endif /* CONFIG_NUMA */
 
 static const unsigned int memcg1_stats[] = {
     NR_FILE_PAGES,
     NR_ANON_MAPPED,
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     NR_ANON_THPS,
 #endif
     NR_SHMEM,
     NR_FILE_MAPPED,
     NR_FILE_DIRTY,
     NR_WRITEBACK,
     MEMCG_SWAP,
 };
 
 static const char *const memcg1_stat_names[] = {
     "cache",
     "rss",
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     "rss_huge",
 #endif
     "shmem",
     "mapped_file",
     "dirty",
     "writeback",
     "swap",
 };
 
 /* Universal VM events cgroup1 shows, original sort order */
 static const unsigned int memcg1_events[] = {
     PGPGIN,
     PGPGOUT,
     PGFAULT,
     PGMAJFAULT,
 };
 
 static int memcg_stat_show(struct seq_file *m, void *v)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
     unsigned long memory, memsw;
     struct mem_cgroup *mi;
     unsigned int i;
 
     BUILD_BUG_ON(ARRAY_SIZE(memcg1_stat_names) != ARRAY_SIZE(memcg1_stats));
 
     mem_cgroup_flush_stats();
 
     for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) {
         unsigned long nr;
 
         if (memcg1_stats[i] == MEMCG_SWAP && !do_memsw_account())
             continue;
         nr = memcg_page_state_local(memcg, memcg1_stats[i]);
         seq_printf(m, "%s %lu\n", memcg1_stat_names[i], nr * PAGE_SIZE);
     }
 
     for (i = 0; i < ARRAY_SIZE(memcg1_events); i++)
         seq_printf(m, "%s %lu\n", vm_event_name(memcg1_events[i]),
                memcg_events_local(memcg, memcg1_events[i]));
 
     for (i = 0; i < NR_LRU_LISTS; i++)
         seq_printf(m, "%s %lu\n", lru_list_name(i),
                memcg_page_state_local(memcg, NR_LRU_BASE + i) *
                PAGE_SIZE);
 
     /* Hierarchical information */
     memory = memsw = PAGE_COUNTER_MAX;
     for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) {
         memory = min(memory, READ_ONCE(mi->memory.max));
         memsw = min(memsw, READ_ONCE(mi->memsw.max));
     }
     seq_printf(m, "hierarchical_memory_limit %llu\n",
            (u64)memory * PAGE_SIZE);
     if (do_memsw_account())
         seq_printf(m, "hierarchical_memsw_limit %llu\n",
                (u64)memsw * PAGE_SIZE);
 
     for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) {
         unsigned long nr;
 
         if (memcg1_stats[i] == MEMCG_SWAP && !do_memsw_account())
             continue;
         nr = memcg_page_state(memcg, memcg1_stats[i]);
         seq_printf(m, "total_%s %llu\n", memcg1_stat_names[i],
                         (u64)nr * PAGE_SIZE);
     }
 
     for (i = 0; i < ARRAY_SIZE(memcg1_events); i++)
         seq_printf(m, "total_%s %llu\n",
                vm_event_name(memcg1_events[i]),
                (u64)memcg_events(memcg, memcg1_events[i]));
 
     for (i = 0; i < NR_LRU_LISTS; i++)
         seq_printf(m, "total_%s %llu\n", lru_list_name(i),
                (u64)memcg_page_state(memcg, NR_LRU_BASE + i) *
                PAGE_SIZE);
 
 #ifdef CONFIG_DEBUG_VM
     {
         pg_data_t *pgdat;
         struct mem_cgroup_per_node *mz;
         unsigned long anon_cost = 0;
         unsigned long file_cost = 0;
 
         for_each_online_pgdat(pgdat) {
             mz = memcg->nodeinfo[pgdat->node_id];
 
             anon_cost += mz->lruvec.anon_cost;
             file_cost += mz->lruvec.file_cost;
         }
         seq_printf(m, "anon_cost %lu\n", anon_cost);
         seq_printf(m, "file_cost %lu\n", file_cost);
     }
 #endif
 
     return 0;
 }
 
 static u64 mem_cgroup_swappiness_read(struct cgroup_subsys_state *css,
                       struct cftype *cft)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
     return mem_cgroup_swappiness(memcg);
 }
 
 static int mem_cgroup_swappiness_write(struct cgroup_subsys_state *css,
                        struct cftype *cft, u64 val)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
     if (val > 200)
         return -EINVAL;
 
     if (!mem_cgroup_is_root(memcg))
         memcg->swappiness = val;
     else
         vm_swappiness = val;
 
     return 0;
 }
 
 static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
 {
     struct mem_cgroup_threshold_ary *t;
     unsigned long usage;
     int i;
 
     rcu_read_lock();
     if (!swap)
         t = rcu_dereference(memcg->thresholds.primary);
     else
         t = rcu_dereference(memcg->memsw_thresholds.primary);
 
     if (!t)
         goto unlock;
 
     usage = mem_cgroup_usage(memcg, swap);
 
     /*
      * current_threshold points to threshold just below or equal to usage.
      * If it's not true, a threshold was crossed after last
      * call of __mem_cgroup_threshold().
      */
     i = t->current_threshold;
 
     /*
      * Iterate backward over array of thresholds starting from
      * current_threshold and check if a threshold is crossed.
      * If none of thresholds below usage is crossed, we read
      * only one element of the array here.
      */
     for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--)
         eventfd_signal(t->entries[i].eventfd, 1);
 
     /* i = current_threshold + 1 */
     i++;
 
     /*
      * Iterate forward over array of thresholds starting from
      * current_threshold+1 and check if a threshold is crossed.
      * If none of thresholds above usage is crossed, we read
      * only one element of the array here.
      */
     for (; i < t->size && unlikely(t->entries[i].threshold <= usage); i++)
         eventfd_signal(t->entries[i].eventfd, 1);
 
     /* Update current_threshold */
     t->current_threshold = i - 1;
 unlock:
     rcu_read_unlock();
 }
 
 static void mem_cgroup_threshold(struct mem_cgroup *memcg)
 {
     while (memcg) {
         __mem_cgroup_threshold(memcg, false);
         if (do_memsw_account())
             __mem_cgroup_threshold(memcg, true);
 
         memcg = parent_mem_cgroup(memcg);
     }
 }
 
 static int compare_thresholds(const void *a, const void *b)
 {
     const struct mem_cgroup_threshold *_a = a;
     const struct mem_cgroup_threshold *_b = b;
 
     if (_a->threshold > _b->threshold)
         return 1;
 
     if (_a->threshold < _b->threshold)
         return -1;
 
     return 0;
 }
 
 static int mem_cgroup_oom_notify_cb(struct mem_cgroup *memcg)
 {
     struct mem_cgroup_eventfd_list *ev;
 
     spin_lock(&memcg_oom_lock);
 
     list_for_each_entry(ev, &memcg->oom_notify, list)
         eventfd_signal(ev->eventfd, 1);
 
     spin_unlock(&memcg_oom_lock);
     return 0;
 }
 
 static void mem_cgroup_oom_notify(struct mem_cgroup *memcg)
 {
     struct mem_cgroup *iter;
 
     for_each_mem_cgroup_tree(iter, memcg)
         mem_cgroup_oom_notify_cb(iter);
 }
 
 static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
     struct eventfd_ctx *eventfd, const char *args, enum res_type type)
 {
     struct mem_cgroup_thresholds *thresholds;
     struct mem_cgroup_threshold_ary *new;
     unsigned long threshold;
     unsigned long usage;
     int i, size, ret;
 
     ret = page_counter_memparse(args, "-1", &threshold);
     if (ret)
         return ret;
 
     mutex_lock(&memcg->thresholds_lock);
 
     if (type == _MEM) {
         thresholds = &memcg->thresholds;
         usage = mem_cgroup_usage(memcg, false);
     } else if (type == _MEMSWAP) {
         thresholds = &memcg->memsw_thresholds;
         usage = mem_cgroup_usage(memcg, true);
     } else
         BUG();
 
     /* Check if a threshold crossed before adding a new one */
     if (thresholds->primary)
         __mem_cgroup_threshold(memcg, type == _MEMSWAP);
 
     size = thresholds->primary ? thresholds->primary->size + 1 : 1;
 
     /* Allocate memory for new array of thresholds */
     new = kmalloc(struct_size(new, entries, size), GFP_KERNEL);
     if (!new) {
         ret = -ENOMEM;
         goto unlock;
     }
     new->size = size;
 
     /* Copy thresholds (if any) to new array */
     if (thresholds->primary)
         memcpy(new->entries, thresholds->primary->entries,
                flex_array_size(new, entries, size - 1));
 
     /* Add new threshold */
     new->entries[size - 1].eventfd = eventfd;
     new->entries[size - 1].threshold = threshold;
 
     /* Sort thresholds. Registering of new threshold isn't time-critical */
     sort(new->entries, size, sizeof(*new->entries),
             compare_thresholds, NULL);
 
     /* Find current threshold */
     new->current_threshold = -1;
     for (i = 0; i < size; i++) {
         if (new->entries[i].threshold <= usage) {
             /*
              * new->current_threshold will not be used until
              * rcu_assign_pointer(), so it's safe to increment
              * it here.
              */
             ++new->current_threshold;
         } else
             break;
     }
 
     /* Free old spare buffer and save old primary buffer as spare */
     kfree(thresholds->spare);
     thresholds->spare = thresholds->primary;
 
     rcu_assign_pointer(thresholds->primary, new);
 
     /* To be sure that nobody uses thresholds */
     synchronize_rcu();
 
 unlock:
     mutex_unlock(&memcg->thresholds_lock);
 
     return ret;
 }
 
 static int mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
     struct eventfd_ctx *eventfd, const char *args)
 {
     return __mem_cgroup_usage_register_event(memcg, eventfd, args, _MEM);
 }
 
 static int memsw_cgroup_usage_register_event(struct mem_cgroup *memcg,
     struct eventfd_ctx *eventfd, const char *args)
 {
     return __mem_cgroup_usage_register_event(memcg, eventfd, args, _MEMSWAP);
 }
 
 static void __mem_cgroup_usage_unregister_event(struct mem_cgroup *memcg,
     struct eventfd_ctx *eventfd, enum res_type type)
 {
     struct mem_cgroup_thresholds *thresholds;
     struct mem_cgroup_threshold_ary *new;
     unsigned long usage;
     int i, j, size, entries;
 
     mutex_lock(&memcg->thresholds_lock);
 
     if (type == _MEM) {
         thresholds = &memcg->thresholds;
         usage = mem_cgroup_usage(memcg, false);
     } else if (type == _MEMSWAP) {
         thresholds = &memcg->memsw_thresholds;
         usage = mem_cgroup_usage(memcg, true);
     } else
         BUG();
 
     if (!thresholds->primary)
         goto unlock;
 
     /* Check if a threshold crossed before removing */
     __mem_cgroup_threshold(memcg, type == _MEMSWAP);
 
     /* Calculate new number of threshold */
     size = entries = 0;
     for (i = 0; i < thresholds->primary->size; i++) {
         if (thresholds->primary->entries[i].eventfd != eventfd)
             size++;
         else
             entries++;
     }
 
     new = thresholds->spare;
 
     /* If no items related to eventfd have been cleared, nothing to do */
     if (!entries)
         goto unlock;
 
     /* Set thresholds array to NULL if we don't have thresholds */
     if (!size) {
         kfree(new);
         new = NULL;
         goto swap_buffers;
     }
 
     new->size = size;
 
     /* Copy thresholds and find current threshold */
     new->current_threshold = -1;
     for (i = 0, j = 0; i < thresholds->primary->size; i++) {
         if (thresholds->primary->entries[i].eventfd == eventfd)
             continue;
 
         new->entries[j] = thresholds->primary->entries[i];
         if (new->entries[j].threshold <= usage) {
             /*
              * new->current_threshold will not be used
              * until rcu_assign_pointer(), so it's safe to increment
              * it here.
              */
             ++new->current_threshold;
         }
         j++;
     }
 
 swap_buffers:
     /* Swap primary and spare array */
     thresholds->spare = thresholds->primary;
 
     rcu_assign_pointer(thresholds->primary, new);
 
     /* To be sure that nobody uses thresholds */
     synchronize_rcu();
 
     /* If all events are unregistered, free the spare array */
     if (!new) {
         kfree(thresholds->spare);
         thresholds->spare = NULL;
     }
 unlock:
     mutex_unlock(&memcg->thresholds_lock);
 }
 
 static void mem_cgroup_usage_unregister_event(struct mem_cgroup *memcg,
     struct eventfd_ctx *eventfd)
 {
     return __mem_cgroup_usage_unregister_event(memcg, eventfd, _MEM);
 }
 
 static void memsw_cgroup_usage_unregister_event(struct mem_cgroup *memcg,
     struct eventfd_ctx *eventfd)
 {
     return __mem_cgroup_usage_unregister_event(memcg, eventfd, _MEMSWAP);
 }
 
 static int mem_cgroup_oom_register_event(struct mem_cgroup *memcg,
     struct eventfd_ctx *eventfd, const char *args)
 {
     struct mem_cgroup_eventfd_list *event;
 
     event = kmalloc(sizeof(*event), GFP_KERNEL);
     if (!event)
         return -ENOMEM;
 
     spin_lock(&memcg_oom_lock);
 
     event->eventfd = eventfd;
     list_add(&event->list, &memcg->oom_notify);
 
     /* already in OOM ? */
     if (memcg->under_oom)
         eventfd_signal(eventfd, 1);
     spin_unlock(&memcg_oom_lock);
 
     return 0;
 }
 
 static void mem_cgroup_oom_unregister_event(struct mem_cgroup *memcg,
     struct eventfd_ctx *eventfd)
 {
     struct mem_cgroup_eventfd_list *ev, *tmp;
 
     spin_lock(&memcg_oom_lock);
 
     list_for_each_entry_safe(ev, tmp, &memcg->oom_notify, list) {
         if (ev->eventfd == eventfd) {
             list_del(&ev->list);
             kfree(ev);
         }
     }
 
     spin_unlock(&memcg_oom_lock);
 }
 
 static int mem_cgroup_oom_control_read(struct seq_file *sf, void *v)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_seq(sf);
 
     seq_printf(sf, "oom_kill_disable %d\n", memcg->oom_kill_disable);
     seq_printf(sf, "under_oom %d\n", (bool)memcg->under_oom);
     seq_printf(sf, "oom_kill %lu\n",
            atomic_long_read(&memcg->memory_events[MEMCG_OOM_KILL]));
     return 0;
 }
 
 static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
     struct cftype *cft, u64 val)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
     /* cannot set to root cgroup and only 0 and 1 are allowed */
     if (mem_cgroup_is_root(memcg) || !((val == 0) || (val == 1)))
         return -EINVAL;
 
     memcg->oom_kill_disable = val;
     if (!val)
         memcg_oom_recover(memcg);
 
     return 0;
 }
 
 #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();
 
     *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 */
 
 /*
  * DO NOT USE IN NEW FILES.
  *
  * "cgroup.event_control" implementation.
  *
  * This is way over-engineered.  It tries to support fully configurable
  * events for each user.  Such level of flexibility is completely
  * unnecessary especially in the light of the planned unified hierarchy.
  *
  * Please deprecate this and replace with something simpler if at all
  * possible.
  */
 
 /*
  * Unregister event and free resources.
  *
  * Gets called from workqueue.
  */
 static void memcg_event_remove(struct work_struct *work)
 {
     struct mem_cgroup_event *event =
         container_of(work, struct mem_cgroup_event, remove);
     struct mem_cgroup *memcg = event->memcg;
 
     remove_wait_queue(event->wqh, &event->wait);
 
     event->unregister_event(memcg, event->eventfd);
 
     /* Notify userspace the event is going away. */
     eventfd_signal(event->eventfd, 1);
 
     eventfd_ctx_put(event->eventfd);
     kfree(event);
     css_put(&memcg->css);
 }
 
 /*
  * Gets called on EPOLLHUP on eventfd when user closes it.
  *
  * Called with wqh->lock held and interrupts disabled.
  */
 static int memcg_event_wake(wait_queue_entry_t *wait, unsigned mode,
                 int sync, void *key)
 {
     struct mem_cgroup_event *event =
         container_of(wait, struct mem_cgroup_event, wait);
     struct mem_cgroup *memcg = event->memcg;
     __poll_t flags = key_to_poll(key);
 
     if (flags & EPOLLHUP) {
         /*
          * If the event has been detached at cgroup removal, we
          * can simply return knowing the other side will cleanup
          * for us.
          *
          * We can't race against event freeing since the other
          * side will require wqh->lock via remove_wait_queue(),
          * which we hold.
          */
         spin_lock(&memcg->event_list_lock);
         if (!list_empty(&event->list)) {
             list_del_init(&event->list);
             /*
              * We are in atomic context, but cgroup_event_remove()
              * may sleep, so we have to call it in workqueue.
              */
             schedule_work(&event->remove);
         }
         spin_unlock(&memcg->event_list_lock);
     }
 
     return 0;
 }
 
 static void memcg_event_ptable_queue_proc(struct file *file,
         wait_queue_head_t *wqh, poll_table *pt)
 {
     struct mem_cgroup_event *event =
         container_of(pt, struct mem_cgroup_event, pt);
 
     event->wqh = wqh;
     add_wait_queue(wqh, &event->wait);
 }
 
 /*
  * DO NOT USE IN NEW FILES.
  *
  * Parse input and register new cgroup event handler.
  *
  * Input must be in format '<event_fd> <control_fd> <args>'.
  * Interpretation of args is defined by control file implementation.
  */
 static ssize_t memcg_write_event_control(struct kernfs_open_file *of,
                      char *buf, size_t nbytes, loff_t off)
 {
     struct cgroup_subsys_state *css = of_css(of);
     struct mem_cgroup *memcg = mem_cgroup_from_css(css);
     struct mem_cgroup_event *event;
     struct cgroup_subsys_state *cfile_css;
     unsigned int efd, cfd;
     struct fd efile;
     struct fd cfile;
     const char *name;
     char *endp;
     int ret;
 
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         return -EOPNOTSUPP;
 
     buf = strstrip(buf);
 
     efd = simple_strtoul(buf, &endp, 10);
     if (*endp != ' ')
         return -EINVAL;
     buf = endp + 1;
 
     cfd = simple_strtoul(buf, &endp, 10);
     if ((*endp != ' ') && (*endp != '\0'))
         return -EINVAL;
     buf = endp + 1;
 
     event = kzalloc(sizeof(*event), GFP_KERNEL);
     if (!event)
         return -ENOMEM;
 
     event->memcg = memcg;
     INIT_LIST_HEAD(&event->list);
     init_poll_funcptr(&event->pt, memcg_event_ptable_queue_proc);
     init_waitqueue_func_entry(&event->wait, memcg_event_wake);
     INIT_WORK(&event->remove, memcg_event_remove);
 
     efile = fdget(efd);
     if (!efile.file) {
         ret = -EBADF;
         goto out_kfree;
     }
 
     event->eventfd = eventfd_ctx_fileget(efile.file);
     if (IS_ERR(event->eventfd)) {
         ret = PTR_ERR(event->eventfd);
         goto out_put_efile;
     }
 
     cfile = fdget(cfd);
     if (!cfile.file) {
         ret = -EBADF;
         goto out_put_eventfd;
     }
 
     /* the process need read permission on control file */
     /* AV: shouldn't we check that it's been opened for read instead? */
     ret = file_permission(cfile.file, MAY_READ);
     if (ret < 0)
         goto out_put_cfile;
 
     /*
      * Determine the event callbacks and set them in @event.  This used
      * to be done via struct cftype but cgroup core no longer knows
      * about these events.  The following is crude but the whole thing
      * is for compatibility anyway.
      *
      * DO NOT ADD NEW FILES.
      */
     name = cfile.file->f_path.dentry->d_name.name;
 
     if (!strcmp(name, "memory.usage_in_bytes")) {
         event->register_event = mem_cgroup_usage_register_event;
         event->unregister_event = mem_cgroup_usage_unregister_event;
     } else if (!strcmp(name, "memory.oom_control")) {
         event->register_event = mem_cgroup_oom_register_event;
         event->unregister_event = mem_cgroup_oom_unregister_event;
     } else if (!strcmp(name, "memory.pressure_level")) {
         event->register_event = vmpressure_register_event;
         event->unregister_event = vmpressure_unregister_event;
     } else if (!strcmp(name, "memory.memsw.usage_in_bytes")) {
         event->register_event = memsw_cgroup_usage_register_event;
         event->unregister_event = memsw_cgroup_usage_unregister_event;
     } else {
         ret = -EINVAL;
         goto out_put_cfile;
     }
 
     /*
      * Verify @cfile should belong to @css.  Also, remaining events are
      * automatically removed on cgroup destruction but the removal is
      * asynchronous, so take an extra ref on @css.
      */
     cfile_css = css_tryget_online_from_dir(cfile.file->f_path.dentry->d_parent,
                            &memory_cgrp_subsys);
     ret = -EINVAL;
     if (IS_ERR(cfile_css))
         goto out_put_cfile;
     if (cfile_css != css) {
         css_put(cfile_css);
         goto out_put_cfile;
     }
 
     ret = event->register_event(memcg, event->eventfd, buf);
     if (ret)
         goto out_put_css;
 
     vfs_poll(efile.file, &event->pt);
 
     spin_lock_irq(&memcg->event_list_lock);
     list_add(&event->list, &memcg->event_list);
     spin_unlock_irq(&memcg->event_list_lock);
 
     fdput(cfile);
     fdput(efile);
 
     return nbytes;
 
 out_put_css:
     css_put(css);
 out_put_cfile:
     fdput(cfile);
 out_put_eventfd:
     eventfd_ctx_put(event->eventfd);
 out_put_efile:
     fdput(efile);
 out_kfree:
     kfree(event);
 
     return ret;
 }
 
 #if defined(CONFIG_MEMCG_KMEM) && (defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG))
 static int mem_cgroup_slab_show(struct seq_file *m, void *p)
 {
     /*
      * Deprecated.
      * Please, take a look at tools/cgroup/memcg_slabinfo.py .
      */
     return 0;
 }
 #endif
 
 static struct cftype mem_cgroup_legacy_files[] = {
     {
         .name = "usage_in_bytes",
         .private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "max_usage_in_bytes",
         .private = MEMFILE_PRIVATE(_MEM, RES_MAX_USAGE),
         .write = mem_cgroup_reset,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "limit_in_bytes",
         .private = MEMFILE_PRIVATE(_MEM, RES_LIMIT),
         .write = mem_cgroup_write,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "soft_limit_in_bytes",
         .private = MEMFILE_PRIVATE(_MEM, RES_SOFT_LIMIT),
         .write = mem_cgroup_write,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "failcnt",
         .private = MEMFILE_PRIVATE(_MEM, RES_FAILCNT),
         .write = mem_cgroup_reset,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "stat",
         .seq_show = memcg_stat_show,
     },
     {
         .name = "force_empty",
         .write = mem_cgroup_force_empty_write,
     },
     {
         .name = "use_hierarchy",
         .write_u64 = mem_cgroup_hierarchy_write,
         .read_u64 = mem_cgroup_hierarchy_read,
     },
     {
         .name = "cgroup.event_control",     /* XXX: for compat */
         .write = memcg_write_event_control,
         .flags = CFTYPE_NO_PREFIX | CFTYPE_WORLD_WRITABLE,
     },
     {
         .name = "swappiness",
         .read_u64 = mem_cgroup_swappiness_read,
         .write_u64 = mem_cgroup_swappiness_write,
     },
     {
         .name = "move_charge_at_immigrate",
         .read_u64 = mem_cgroup_move_charge_read,
         .write_u64 = mem_cgroup_move_charge_write,
     },
     {
         .name = "oom_control",
         .seq_show = mem_cgroup_oom_control_read,
         .write_u64 = mem_cgroup_oom_control_write,
     },
     {
         .name = "pressure_level",
     },
 #ifdef CONFIG_NUMA
     {
         .name = "numa_stat",
         .seq_show = memcg_numa_stat_show,
     },
 #endif
     {
         .name = "kmem.limit_in_bytes",
         .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
         .write = mem_cgroup_write,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "kmem.usage_in_bytes",
         .private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "kmem.failcnt",
         .private = MEMFILE_PRIVATE(_KMEM, RES_FAILCNT),
         .write = mem_cgroup_reset,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "kmem.max_usage_in_bytes",
         .private = MEMFILE_PRIVATE(_KMEM, RES_MAX_USAGE),
         .write = mem_cgroup_reset,
         .read_u64 = mem_cgroup_read_u64,
     },
 #if defined(CONFIG_MEMCG_KMEM) && \
     (defined(CONFIG_SLAB) || defined(CONFIG_SLUB_DEBUG))
     {
         .name = "kmem.slabinfo",
         .seq_show = mem_cgroup_slab_show,
     },
 #endif
     {
         .name = "kmem.tcp.limit_in_bytes",
         .private = MEMFILE_PRIVATE(_TCP, RES_LIMIT),
         .write = mem_cgroup_write,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "kmem.tcp.usage_in_bytes",
         .private = MEMFILE_PRIVATE(_TCP, RES_USAGE),
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "kmem.tcp.failcnt",
         .private = MEMFILE_PRIVATE(_TCP, RES_FAILCNT),
         .write = mem_cgroup_reset,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "kmem.tcp.max_usage_in_bytes",
         .private = MEMFILE_PRIVATE(_TCP, RES_MAX_USAGE),
         .write = mem_cgroup_reset,
         .read_u64 = mem_cgroup_read_u64,
     },
     { },    /* terminate */
 };
 
 /*
  * 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.
  */
 
 static DEFINE_IDR(mem_cgroup_idr);
 
 static void mem_cgroup_id_remove(struct mem_cgroup *memcg)
 {
     if (memcg->id.id > 0) {
         idr_remove(&mem_cgroup_idr, memcg->id.id);
         memcg->id.id = 0;
     }
 }
 
 static void __maybe_unused mem_cgroup_id_get_many(struct mem_cgroup *memcg,
                           unsigned int n)
 {
     refcount_add(n, &memcg->id.ref);
 }
 
 static 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 idr_find(&mem_cgroup_idr, 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 (!cgrp)
         return ERR_PTR(-ENOENT);
 
     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 int 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 1;
 
     pn->lruvec_stats_percpu = alloc_percpu_gfp(struct lruvec_stats_percpu,
                            GFP_KERNEL_ACCOUNT);
     if (!pn->lruvec_stats_percpu) {
         kfree(pn);
         return 1;
     }
 
     lruvec_init(&pn->lruvec);
     pn->memcg = memcg;
 
     memcg->nodeinfo[node] = pn;
     return 0;
 }
 
 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);
 }
 
 static void __mem_cgroup_free(struct mem_cgroup *memcg)
 {
     int node;
 
     for_each_node(node)
         free_mem_cgroup_per_node_info(memcg, node);
     free_percpu(memcg->vmstats_percpu);
     kfree(memcg);
 }
 
 static void mem_cgroup_free(struct mem_cgroup *memcg)
 {
     memcg_wb_domain_exit(memcg);
     __mem_cgroup_free(memcg);
 }
 
 static struct mem_cgroup *mem_cgroup_alloc(void)
 {
     struct mem_cgroup *memcg;
     int node;
     int __maybe_unused i;
     long error = -ENOMEM;
 
     memcg = kzalloc(struct_size(memcg, nodeinfo, nr_node_ids), GFP_KERNEL);
     if (!memcg)
         return ERR_PTR(error);
 
     memcg->id.id = idr_alloc(&mem_cgroup_idr, NULL,
                  1, MEM_CGROUP_ID_MAX + 1, GFP_KERNEL);
     if (memcg->id.id < 0) {
         error = memcg->id.id;
         goto fail;
     }
 
     memcg->vmstats_percpu = alloc_percpu_gfp(struct memcg_vmstats_percpu,
                          GFP_KERNEL_ACCOUNT);
     if (!memcg->vmstats_percpu)
         goto fail;
 
     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);
     INIT_LIST_HEAD(&memcg->oom_notify);
     mutex_init(&memcg->thresholds_lock);
     spin_lock_init(&memcg->move_lock);
     vmpressure_init(&memcg->vmpressure);
     INIT_LIST_HEAD(&memcg->event_list);
     spin_lock_init(&memcg->event_list_lock);
     memcg->socket_pressure = jiffies;
 #ifdef CONFIG_MEMCG_KMEM
     memcg->kmemcg_id = -1;
     INIT_LIST_HEAD(&memcg->objcg_list);
 #endif
 #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
     idr_replace(&mem_cgroup_idr, memcg, memcg->id.id);
     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();
     set_active_memcg(old_memcg);
     if (IS_ERR(memcg))
         return ERR_CAST(memcg);
 
     page_counter_set_high(&memcg->memory, PAGE_COUNTER_MAX);
     memcg->soft_limit = PAGE_COUNTER_MAX;
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
     memcg->zswap_max = PAGE_COUNTER_MAX;
 #endif
     page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
     if (parent) {
         memcg->swappiness = mem_cgroup_swappiness(parent);
         memcg->oom_kill_disable = parent->oom_kill_disable;
 
         page_counter_init(&memcg->memory, &parent->memory);
         page_counter_init(&memcg->swap, &parent->swap);
         page_counter_init(&memcg->kmem, &parent->kmem);
         page_counter_init(&memcg->tcpmem, &parent->tcpmem);
     } else {
         page_counter_init(&memcg->memory, NULL);
         page_counter_init(&memcg->swap, NULL);
         page_counter_init(&memcg->kmem, NULL);
         page_counter_init(&memcg->tcpmem, NULL);
 
         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);
 
     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;
 
     /* Online state pins memcg ID, memcg ID pins CSS */
     refcount_set(&memcg->id.ref, 1);
     css_get(css);
 
     if (unlikely(mem_cgroup_is_root(memcg)))
         queue_delayed_work(system_unbound_wq, &stats_flush_dwork,
                    2UL*HZ);
     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);
     struct mem_cgroup_event *event, *tmp;
 
     /*
      * Unregister events and notify userspace.
      * Notify userspace about cgroup removing only after rmdir of cgroup
      * directory to avoid race between userspace and kernelspace.
      */
     spin_lock_irq(&memcg->event_list_lock);
     list_for_each_entry_safe(event, tmp, &memcg->event_list, list) {
         list_del_init(&event->list);
         schedule_work(&event->remove);
     }
     spin_unlock_irq(&memcg->event_list_lock);
 
     page_counter_set_min(&memcg->memory, 0);
     page_counter_set_low(&memcg->memory, 0);
 
     memcg_offline_kmem(memcg);
     reparent_shrinker_deferred(memcg);
     wb_memcg_offline(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);
 }
 
 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) && memcg->tcpmem_active)
         static_branch_dec(&memcg_sockets_enabled_key);
 
     vmpressure_cleanup(&memcg->vmpressure);
     cancel_work_sync(&memcg->high_work);
     mem_cgroup_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);
     page_counter_set_max(&memcg->kmem, PAGE_COUNTER_MAX);
     page_counter_set_max(&memcg->tcpmem, PAGE_COUNTER_MAX);
     page_counter_set_min(&memcg->memory, 0);
     page_counter_set_low(&memcg->memory, 0);
     page_counter_set_high(&memcg->memory, PAGE_COUNTER_MAX);
     memcg->soft_limit = PAGE_COUNTER_MAX;
     page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
     memcg_wb_domain_size_changed(memcg);
 }
 
 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;
     long delta, v;
     int i, nid;
 
     statc = per_cpu_ptr(memcg->vmstats_percpu, cpu);
 
     for (i = 0; i < MEMCG_NR_STAT; 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 = memcg->vmstats.state_pending[i];
         if (delta)
             memcg->vmstats.state_pending[i] = 0;
 
         /* Add CPU changes on this level since the last flush */
         v = READ_ONCE(statc->state[i]);
         if (v != statc->state_prev[i]) {
             delta += v - statc->state_prev[i];
             statc->state_prev[i] = v;
         }
 
         if (!delta)
             continue;
 
         /* Aggregate counts on this level and propagate upwards */
         memcg->vmstats.state[i] += delta;
         if (parent)
             parent->vmstats.state_pending[i] += delta;
     }
 
     for (i = 0; i < NR_VM_EVENT_ITEMS; i++) {
         delta = memcg->vmstats.events_pending[i];
         if (delta)
             memcg->vmstats.events_pending[i] = 0;
 
         v = READ_ONCE(statc->events[i]);
         if (v != statc->events_prev[i]) {
             delta += v - statc->events_prev[i];
             statc->events_prev[i] = v;
         }
 
         if (!delta)
             continue;
 
         memcg->vmstats.events[i] += delta;
         if (parent)
             parent->vmstats.events_pending[i] += delta;
     }
 
     for_each_node_state(nid, N_MEMORY) {
         struct mem_cgroup_per_node *pn = memcg->nodeinfo[nid];
         struct mem_cgroup_per_node *ppn = NULL;
         struct lruvec_stats_percpu *lstatc;
 
         if (parent)
             ppn = parent->nodeinfo[nid];
 
         lstatc = per_cpu_ptr(pn->lruvec_stats_percpu, cpu);
 
         for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
             delta = pn->lruvec_stats.state_pending[i];
             if (delta)
                 pn->lruvec_stats.state_pending[i] = 0;
 
             v = READ_ONCE(lstatc->state[i]);
             if (v != lstatc->state_prev[i]) {
                 delta += v - lstatc->state_prev[i];
                 lstatc->state_prev[i] = v;
             }
 
             if (!delta)
                 continue;
 
             pn->lruvec_stats.state[i] += delta;
             if (ppn)
                 ppn->lruvec_stats.state_pending[i] += delta;
         }
     }
 }
 
 #ifdef CONFIG_MMU
 /* Handlers for move charge at task migration. */
 static int mem_cgroup_do_precharge(unsigned long count)
 {
     int ret;
 
     /* Try a single bulk charge without reclaim first, kswapd may wake */
     ret = try_charge(mc.to, GFP_KERNEL & ~__GFP_DIRECT_RECLAIM, count);
     if (!ret) {
         mc.precharge += count;
         return ret;
     }
 
     /* Try charges one by one with reclaim, but do not retry */
     while (count--) {
         ret = try_charge(mc.to, GFP_KERNEL | __GFP_NORETRY, 1);
         if (ret)
             return ret;
         mc.precharge++;
         cond_resched();
     }
     return 0;
 }
 
 union mc_target {
     struct page *page;
     swp_entry_t ent;
 };
 
 enum mc_target_type {
     MC_TARGET_NONE = 0,
     MC_TARGET_PAGE,
     MC_TARGET_SWAP,
     MC_TARGET_DEVICE,
 };
 
 static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
                         unsigned long addr, pte_t ptent)
 {
     struct page *page = vm_normal_page(vma, addr, ptent);
 
     if (!page || !page_mapped(page))
         return NULL;
     if (PageAnon(page)) {
         if (!(mc.flags & MOVE_ANON))
             return NULL;
     } else {
         if (!(mc.flags & MOVE_FILE))
             return NULL;
     }
     if (!get_page_unless_zero(page))
         return NULL;
 
     return page;
 }
 
 #if defined(CONFIG_SWAP) || defined(CONFIG_DEVICE_PRIVATE)
 static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
             pte_t ptent, swp_entry_t *entry)
 {
     struct page *page = NULL;
     swp_entry_t ent = pte_to_swp_entry(ptent);
 
     if (!(mc.flags & MOVE_ANON))
         return NULL;
 
     /*
      * Handle device private pages that are not accessible by the CPU, but
      * stored as special swap entries in the page table.
      */
     if (is_device_private_entry(ent)) {
         page = pfn_swap_entry_to_page(ent);
         if (!get_page_unless_zero(page))
             return NULL;
         return page;
     }
 
     if (non_swap_entry(ent))
         return NULL;
 
     /*
      * Because lookup_swap_cache() updates some statistics counter,
      * we call find_get_page() with swapper_space directly.
      */
     page = find_get_page(swap_address_space(ent), swp_offset(ent));
     entry->val = ent.val;
 
     return page;
 }
 #else
 static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
             pte_t ptent, swp_entry_t *entry)
 {
     return NULL;
 }
 #endif
 
 static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
             unsigned long addr, pte_t ptent)
 {
     if (!vma->vm_file) /* anonymous vma */
         return NULL;
     if (!(mc.flags & MOVE_FILE))
         return NULL;
 
     /* page is moved even if it's not RSS of this task(page-faulted). */
     /* shmem/tmpfs may report page out on swap: account for that too. */
     return find_get_incore_page(vma->vm_file->f_mapping,
             linear_page_index(vma, addr));
 }
 
 /**
  * mem_cgroup_move_account - move account of the page
  * @page: the page
  * @compound: charge the page as compound or small page
  * @from: mem_cgroup which the page is moved from.
  * @to: mem_cgroup which the page is moved to. @from != @to.
  *
  * The caller must make sure the page is not on LRU (isolate_page() is useful.)
  *
  * This function doesn't do "charge" to new cgroup and doesn't do "uncharge"
  * from old cgroup.
  */
 static int mem_cgroup_move_account(struct page *page,
                    bool compound,
                    struct mem_cgroup *from,
                    struct mem_cgroup *to)
 {
     struct folio *folio = page_folio(page);
     struct lruvec *from_vec, *to_vec;
     struct pglist_data *pgdat;
     unsigned int nr_pages = compound ? folio_nr_pages(folio) : 1;
     int nid, ret;
 
     VM_BUG_ON(from == to);
     VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
     VM_BUG_ON(compound && !folio_test_large(folio));
 
     /*
      * Prevent mem_cgroup_migrate() from looking at
      * page's memory cgroup of its source page while we change it.
      */
     ret = -EBUSY;
     if (!folio_trylock(folio))
         goto out;
 
     ret = -EINVAL;
     if (folio_memcg(folio) != from)
         goto out_unlock;
 
     pgdat = folio_pgdat(folio);
     from_vec = mem_cgroup_lruvec(from, pgdat);
     to_vec = mem_cgroup_lruvec(to, pgdat);
 
     folio_memcg_lock(folio);
 
     if (folio_test_anon(folio)) {
         if (folio_mapped(folio)) {
             __mod_lruvec_state(from_vec, NR_ANON_MAPPED, -nr_pages);
             __mod_lruvec_state(to_vec, NR_ANON_MAPPED, nr_pages);
             if (folio_test_transhuge(folio)) {
                 __mod_lruvec_state(from_vec, NR_ANON_THPS,
                            -nr_pages);
                 __mod_lruvec_state(to_vec, NR_ANON_THPS,
                            nr_pages);
             }
         }
     } else {
         __mod_lruvec_state(from_vec, NR_FILE_PAGES, -nr_pages);
         __mod_lruvec_state(to_vec, NR_FILE_PAGES, nr_pages);
 
         if (folio_test_swapbacked(folio)) {
             __mod_lruvec_state(from_vec, NR_SHMEM, -nr_pages);
             __mod_lruvec_state(to_vec, NR_SHMEM, nr_pages);
         }
 
         if (folio_mapped(folio)) {
             __mod_lruvec_state(from_vec, NR_FILE_MAPPED, -nr_pages);
             __mod_lruvec_state(to_vec, NR_FILE_MAPPED, nr_pages);
         }
 
         if (folio_test_dirty(folio)) {
             struct address_space *mapping = folio_mapping(folio);
 
             if (mapping_can_writeback(mapping)) {
                 __mod_lruvec_state(from_vec, NR_FILE_DIRTY,
                            -nr_pages);
                 __mod_lruvec_state(to_vec, NR_FILE_DIRTY,
                            nr_pages);
             }
         }
     }
 
     if (folio_test_writeback(folio)) {
         __mod_lruvec_state(from_vec, NR_WRITEBACK, -nr_pages);
         __mod_lruvec_state(to_vec, NR_WRITEBACK, nr_pages);
     }
 
     /*
      * All state has been migrated, let's switch to the new memcg.
      *
      * It is safe to change page's memcg here because the page
      * is referenced, charged, isolated, and locked: we can't race
      * with (un)charging, migration, LRU putback, or anything else
      * that would rely on a stable page's memory cgroup.
      *
      * Note that lock_page_memcg is a memcg lock, not a page lock,
      * to save space. As soon as we switch page's memory cgroup to a
      * new memcg that isn't locked, the above state can change
      * concurrently again. Make sure we're truly done with it.
      */
     smp_mb();
 
     css_get(&to->css);
     css_put(&from->css);
 
     folio->memcg_data = (unsigned long)to;
 
     __folio_memcg_unlock(from);
 
     ret = 0;
     nid = folio_nid(folio);
 
     local_irq_disable();
     mem_cgroup_charge_statistics(to, nr_pages);
     memcg_check_events(to, nid);
     mem_cgroup_charge_statistics(from, -nr_pages);
     memcg_check_events(from, nid);
     local_irq_enable();
 out_unlock:
     folio_unlock(folio);
 out:
     return ret;
 }
 
 /**
  * get_mctgt_type - get target type of moving charge
  * @vma: the vma the pte to be checked belongs
  * @addr: the address corresponding to the pte to be checked
  * @ptent: the pte to be checked
  * @target: the pointer the target page or swap ent will be stored(can be NULL)
  *
  * Returns
  *   0(MC_TARGET_NONE): if the pte is not a target for move charge.
  *   1(MC_TARGET_PAGE): if the page corresponding to this pte is a target for
  *     move charge. if @target is not NULL, the page is stored in target->page
  *     with extra refcnt got(Callers should handle it).
  *   2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
  *     target for charge migration. if @target is not NULL, the entry is stored
  *     in target->ent.
  *   3(MC_TARGET_DEVICE): like MC_TARGET_PAGE  but page is device memory and
  *   thus not on the lru.
  *     For now we such page is charge like a regular page would be as for all
  *     intent and purposes it is just special memory taking the place of a
  *     regular page.
  *
  *     See Documentations/vm/hmm.txt and include/linux/hmm.h
  *
  * Called with pte lock held.
  */
 
 static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
         unsigned long addr, pte_t ptent, union mc_target *target)
 {
     struct page *page = NULL;
     enum mc_target_type ret = MC_TARGET_NONE;
     swp_entry_t ent = { .val = 0 };
 
     if (pte_present(ptent))
         page = mc_handle_present_pte(vma, addr, ptent);
     else if (pte_none_mostly(ptent))
         /*
          * PTE markers should be treated as a none pte here, separated
          * from other swap handling below.
          */
         page = mc_handle_file_pte(vma, addr, ptent);
     else if (is_swap_pte(ptent))
         page = mc_handle_swap_pte(vma, ptent, &ent);
 
     if (!page && !ent.val)
         return ret;
     if (page) {
         /*
          * Do only loose check w/o serialization.
          * mem_cgroup_move_account() checks the page is valid or
          * not under LRU exclusion.
          */
         if (page_memcg(page) == mc.from) {
             ret = MC_TARGET_PAGE;
             if (is_device_private_page(page) ||
                 is_device_coherent_page(page))
                 ret = MC_TARGET_DEVICE;
             if (target)
                 target->page = page;
         }
         if (!ret || !target)
             put_page(page);
     }
     /*
      * There is a swap entry and a page doesn't exist or isn't charged.
      * But we cannot move a tail-page in a THP.
      */
     if (ent.val && !ret && (!page || !PageTransCompound(page)) &&
         mem_cgroup_id(mc.from) == lookup_swap_cgroup_id(ent)) {
         ret = MC_TARGET_SWAP;
         if (target)
             target->ent = ent;
     }
     return ret;
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 /*
  * We don't consider PMD mapped swapping or file mapped pages because THP does
  * not support them for now.
  * Caller should make sure that pmd_trans_huge(pmd) is true.
  */
 static enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma,
         unsigned long addr, pmd_t pmd, union mc_target *target)
 {
     struct page *page = NULL;
     enum mc_target_type ret = MC_TARGET_NONE;
 
     if (unlikely(is_swap_pmd(pmd))) {
         VM_BUG_ON(thp_migration_supported() &&
                   !is_pmd_migration_entry(pmd));
         return ret;
     }
     page = pmd_page(pmd);
     VM_BUG_ON_PAGE(!page || !PageHead(page), page);
     if (!(mc.flags & MOVE_ANON))
         return ret;
     if (page_memcg(page) == mc.from) {
         ret = MC_TARGET_PAGE;
         if (target) {
             get_page(page);
             target->page = page;
         }
     }
     return ret;
 }
 #else
 static inline enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma,
         unsigned long addr, pmd_t pmd, union mc_target *target)
 {
     return MC_TARGET_NONE;
 }
 #endif
 
 static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
                     unsigned long addr, unsigned long end,
                     struct mm_walk *walk)
 {
     struct vm_area_struct *vma = walk->vma;
     pte_t *pte;
     spinlock_t *ptl;
 
     ptl = pmd_trans_huge_lock(pmd, vma);
     if (ptl) {
         /*
          * Note their can not be MC_TARGET_DEVICE for now as we do not
          * support transparent huge page with MEMORY_DEVICE_PRIVATE but
          * this might change.
          */
         if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
             mc.precharge += HPAGE_PMD_NR;
         spin_unlock(ptl);
         return 0;
     }
 
     if (pmd_trans_unstable(pmd))
         return 0;
     pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
     for (; addr != end; pte++, addr += PAGE_SIZE)
         if (get_mctgt_type(vma, addr, *pte, NULL))
             mc.precharge++; /* increment precharge temporarily */
     pte_unmap_unlock(pte - 1, ptl);
     cond_resched();
 
     return 0;
 }
 
 static const struct mm_walk_ops precharge_walk_ops = {
     .pmd_entry  = mem_cgroup_count_precharge_pte_range,
 };
 
 static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm)
 {
     unsigned long precharge;
 
     mmap_read_lock(mm);
     walk_page_range(mm, 0, mm->highest_vm_end, &precharge_walk_ops, NULL);
     mmap_read_unlock(mm);
 
     precharge = mc.precharge;
     mc.precharge = 0;
 
     return precharge;
 }
 
 static int mem_cgroup_precharge_mc(struct mm_struct *mm)
 {
     unsigned long precharge = mem_cgroup_count_precharge(mm);
 
     VM_BUG_ON(mc.moving_task);
     mc.moving_task = current;
     return mem_cgroup_do_precharge(precharge);
 }
 
 /* cancels all extra charges on mc.from and mc.to, and wakes up all waiters. */
 static void __mem_cgroup_clear_mc(void)
 {
     struct mem_cgroup *from = mc.from;
     struct mem_cgroup *to = mc.to;
 
     /* we must uncharge all the leftover precharges from mc.to */
     if (mc.precharge) {
         cancel_charge(mc.to, mc.precharge);
         mc.precharge = 0;
     }
     /*
      * we didn't uncharge from mc.from at mem_cgroup_move_account(), so
      * we must uncharge here.
      */
     if (mc.moved_charge) {
         cancel_charge(mc.from, mc.moved_charge);
         mc.moved_charge = 0;
     }
     /* we must fixup refcnts and charges */
     if (mc.moved_swap) {
         /* uncharge swap account from the old cgroup */
         if (!mem_cgroup_is_root(mc.from))
             page_counter_uncharge(&mc.from->memsw, mc.moved_swap);
 
         mem_cgroup_id_put_many(mc.from, mc.moved_swap);
 
         /*
          * we charged both to->memory and to->memsw, so we
          * should uncharge to->memory.
          */
         if (!mem_cgroup_is_root(mc.to))
             page_counter_uncharge(&mc.to->memory, mc.moved_swap);
 
         mc.moved_swap = 0;
     }
     memcg_oom_recover(from);
     memcg_oom_recover(to);
     wake_up_all(&mc.waitq);
 }
 
 static void mem_cgroup_clear_mc(void)
 {
     struct mm_struct *mm = mc.mm;
 
     /*
      * we must clear moving_task before waking up waiters at the end of
      * task migration.
      */
     mc.moving_task = NULL;
     __mem_cgroup_clear_mc();
     spin_lock(&mc.lock);
     mc.from = NULL;
     mc.to = NULL;
     mc.mm = NULL;
     spin_unlock(&mc.lock);
 
     mmput(mm);
 }
 
 static int mem_cgroup_can_attach(struct cgroup_taskset *tset)
 {
     struct cgroup_subsys_state *css;
     struct mem_cgroup *memcg = NULL; /* unneeded init to make gcc happy */
     struct mem_cgroup *from;
     struct task_struct *leader, *p;
     struct mm_struct *mm;
     unsigned long move_flags;
     int ret = 0;
 
     /* charge immigration isn't supported on the default hierarchy */
     if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
         return 0;
 
     /*
      * Multi-process migrations only happen on the default hierarchy
      * where charge immigration is not used.  Perform charge
      * immigration if @tset contains a leader and whine if there are
      * multiple.
      */
     p = NULL;
     cgroup_taskset_for_each_leader(leader, css, tset) {
         WARN_ON_ONCE(p);
         p = leader;
         memcg = mem_cgroup_from_css(css);
     }
     if (!p)
         return 0;
 
     /*
      * We are now committed to this value whatever it is. Changes in this
      * tunable will only affect upcoming migrations, not the current one.
      * So we need to save it, and keep it going.
      */
     move_flags = READ_ONCE(memcg->move_charge_at_immigrate);
     if (!move_flags)
         return 0;
 
     from = mem_cgroup_from_task(p);
 
     VM_BUG_ON(from == memcg);
 
     mm = get_task_mm(p);
     if (!mm)
         return 0;
     /* We move charges only when we move a owner of the mm */
     if (mm->owner == p) {
         VM_BUG_ON(mc.from);
         VM_BUG_ON(mc.to);
         VM_BUG_ON(mc.precharge);
         VM_BUG_ON(mc.moved_charge);
         VM_BUG_ON(mc.moved_swap);
 
         spin_lock(&mc.lock);
         mc.mm = mm;
         mc.from = from;
         mc.to = memcg;
         mc.flags = move_flags;
         spin_unlock(&mc.lock);
         /* We set mc.moving_task later */
 
         ret = mem_cgroup_precharge_mc(mm);
         if (ret)
             mem_cgroup_clear_mc();
     } else {
         mmput(mm);
     }
     return ret;
 }
 
 static void mem_cgroup_cancel_attach(struct cgroup_taskset *tset)
 {
     if (mc.to)
         mem_cgroup_clear_mc();
 }
 
 static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
                 unsigned long addr, unsigned long end,
                 struct mm_walk *walk)
 {
     int ret = 0;
     struct vm_area_struct *vma = walk->vma;
     pte_t *pte;
     spinlock_t *ptl;
     enum mc_target_type target_type;
     union mc_target target;
     struct page *page;
 
     ptl = pmd_trans_huge_lock(pmd, vma);
     if (ptl) {
         if (mc.precharge < HPAGE_PMD_NR) {
             spin_unlock(ptl);
             return 0;
         }
         target_type = get_mctgt_type_thp(vma, addr, *pmd, &target);
         if (target_type == MC_TARGET_PAGE) {
             page = target.page;
             if (!isolate_lru_page(page)) {
                 if (!mem_cgroup_move_account(page, true,
                                  mc.from, mc.to)) {
                     mc.precharge -= HPAGE_PMD_NR;
                     mc.moved_charge += HPAGE_PMD_NR;
                 }
                 putback_lru_page(page);
             }
             put_page(page);
         } else if (target_type == MC_TARGET_DEVICE) {
             page = target.page;
             if (!mem_cgroup_move_account(page, true,
                              mc.from, mc.to)) {
                 mc.precharge -= HPAGE_PMD_NR;
                 mc.moved_charge += HPAGE_PMD_NR;
             }
             put_page(page);
         }
         spin_unlock(ptl);
         return 0;
     }
 
     if (pmd_trans_unstable(pmd))
         return 0;
 retry:
     pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
     for (; addr != end; addr += PAGE_SIZE) {
         pte_t ptent = *(pte++);
         bool device = false;
         swp_entry_t ent;
 
         if (!mc.precharge)
             break;
 
         switch (get_mctgt_type(vma, addr, ptent, &target)) {
         case MC_TARGET_DEVICE:
             device = true;
             fallthrough;
         case MC_TARGET_PAGE:
             page = target.page;
             /*
              * We can have a part of the split pmd here. Moving it
              * can be done but it would be too convoluted so simply
              * ignore such a partial THP and keep it in original
              * memcg. There should be somebody mapping the head.
              */
             if (PageTransCompound(page))
                 goto put;
             if (!device && isolate_lru_page(page))
                 goto put;
             if (!mem_cgroup_move_account(page, false,
                         mc.from, mc.to)) {
                 mc.precharge--;
                 /* we uncharge from mc.from later. */
                 mc.moved_charge++;
             }
             if (!device)
                 putback_lru_page(page);
 put:            /* get_mctgt_type() gets the page */
             put_page(page);
             break;
         case MC_TARGET_SWAP:
             ent = target.ent;
             if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to)) {
                 mc.precharge--;
                 mem_cgroup_id_get_many(mc.to, 1);
                 /* we fixup other refcnts and charges later. */
                 mc.moved_swap++;
             }
             break;
         default:
             break;
         }
     }
     pte_unmap_unlock(pte - 1, ptl);
     cond_resched();
 
     if (addr != end) {
         /*
          * We have consumed all precharges we got in can_attach().
          * We try charge one by one, but don't do any additional
          * charges to mc.to if we have failed in charge once in attach()
          * phase.
          */
         ret = mem_cgroup_do_precharge(1);
         if (!ret)
             goto retry;
     }
 
     return ret;
 }
 
 static const struct mm_walk_ops charge_walk_ops = {
     .pmd_entry  = mem_cgroup_move_charge_pte_range,
 };
 
 static void mem_cgroup_move_charge(void)
 {
     lru_add_drain_all();
     /*
      * Signal lock_page_memcg() to take the memcg's move_lock
      * while we're moving its pages to another memcg. Then wait
      * for already started RCU-only updates to finish.
      */
     atomic_inc(&mc.from->moving_account);
     synchronize_rcu();
 retry:
     if (unlikely(!mmap_read_trylock(mc.mm))) {
         /*
          * Someone who are holding the mmap_lock might be waiting in
          * waitq. So we cancel all extra charges, wake up all waiters,
          * and retry. Because we cancel precharges, we might not be able
          * to move enough charges, but moving charge is a best-effort
          * feature anyway, so it wouldn't be a big problem.
          */
         __mem_cgroup_clear_mc();
         cond_resched();
         goto retry;
     }
     /*
      * When we have consumed all precharges and failed in doing
      * additional charge, the page walk just aborts.
      */
     walk_page_range(mc.mm, 0, mc.mm->highest_vm_end, &charge_walk_ops,
             NULL);
 
     mmap_read_unlock(mc.mm);
     atomic_dec(&mc.from->moving_account);
 }
 
 static void mem_cgroup_move_task(void)
 {
     if (mc.to) {
         mem_cgroup_move_charge();
         mem_cgroup_clear_mc();
     }
 }
 #else   /* !CONFIG_MMU */
 static int mem_cgroup_can_attach(struct cgroup_taskset *tset)
 {
     return 0;
 }
 static void mem_cgroup_cancel_attach(struct cgroup_taskset *tset)
 {
 }
 static void mem_cgroup_move_task(void)
 {
 }
 #endif
 
 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;
 }
 
 static u64 memory_peak_read(struct cgroup_subsys_state *css,
                 struct cftype *cft)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_css(css);
 
     return (u64)memcg->memory.watermark * PAGE_SIZE;
 }
 
 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);
 
         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))
                 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;
 }
 
 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;
 }
 
 static int memory_stat_show(struct seq_file *m, void *v)
 {
     struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
     char *buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
 
     if (!buf)
         return -ENOMEM;
     memory_stat_format(memcg, buf, PAGE_SIZE);
     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_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();
 
     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", 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;
 
     memcg->oom_group = oom_group;
 
     return nbytes;
 }
 
 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;
     unsigned int reclaim_options;
     int err;
 
     buf = strstrip(buf);
     err = page_counter_memparse(buf, "", &nr_to_reclaim);
     if (err)
         return err;
 
     reclaim_options = MEMCG_RECLAIM_MAY_SWAP | MEMCG_RECLAIM_PROACTIVE;
     while (nr_reclaimed < nr_to_reclaim) {
         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,
                         nr_to_reclaim - nr_reclaimed,
                         GFP_KERNEL, reclaim_options);
 
         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,
         .read_u64 = memory_peak_read,
     },
     {
         .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,
     .can_attach = mem_cgroup_can_attach,
     .cancel_attach = mem_cgroup_cancel_attach,
     .post_attach = mem_cgroup_move_task,
     .dfl_cftypes = memory_files,
     .legacy_cftypes = mem_cgroup_legacy_files,
     .early_init = 0,
 };
 
 /*
  * This function calculates an individual cgroup's effective
  * protection which is derived from its own memory.min/low, its
  * parent's and siblings' settings, as well as the actual memory
  * distribution in the tree.
  *
  * The following rules apply to the effective protection values:
  *
  * 1. At the first level of reclaim, effective protection is equal to
  *    the declared protection in memory.min and memory.low.
  *
  * 2. To enable safe delegation of the protection configuration, at
  *    subsequent levels the effective protection is capped to the
  *    parent's effective protection.
  *
  * 3. To make complex and dynamic subtrees easier to configure, the
  *    user is allowed to overcommit the declared protection at a given
  *    level. If that is the case, the parent's effective protection is
  *    distributed to the children in proportion to how much protection
  *    they have declared and how much of it they are utilizing.
  *
  *    This makes distribution proportional, but also work-conserving:
  *    if one cgroup claims much more protection than it uses memory,
  *    the unused remainder is available to its siblings.
  *
  * 4. Conversely, when the declared protection is undercommitted at a
  *    given level, the distribution of the larger parental protection
  *    budget is NOT proportional. A cgroup's protection from a sibling
  *    is capped to its own memory.min/low setting.
  *
  * 5. However, to allow protecting recursive subtrees from each other
  *    without having to declare each individual cgroup's fixed share
  *    of the ancestor's claim to protection, any unutilized -
  *    "floating" - protection from up the tree is distributed in
  *    proportion to each cgroup's *usage*. This makes the protection
  *    neutral wrt sibling cgroups and lets them compete freely over
  *    the shared parental protection budget, but it protects the
  *    subtree as a whole from neighboring subtrees.
  *
  * Note that 4. and 5. are not in conflict: 4. is about protecting
  * against immediate siblings whereas 5. is about protecting against
  * neighboring subtrees.
  */
 static unsigned long effective_protection(unsigned long usage,
                       unsigned long parent_usage,
                       unsigned long setting,
                       unsigned long parent_effective,
                       unsigned long siblings_protected)
 {
     unsigned long protected;
     unsigned long ep;
 
     protected = min(usage, setting);
     /*
      * If all cgroups at this level combined claim and use more
      * protection then what the parent affords them, distribute
      * shares in proportion to utilization.
      *
      * We are using actual utilization rather than the statically
      * claimed protection in order to be work-conserving: claimed
      * but unused protection is available to siblings that would
      * otherwise get a smaller chunk than what they claimed.
      */
     if (siblings_protected > parent_effective)
         return protected * parent_effective / siblings_protected;
 
     /*
      * Ok, utilized protection of all children is within what the
      * parent affords them, so we know whatever this child claims
      * and utilizes is effectively protected.
      *
      * If there is unprotected usage beyond this value, reclaim
      * will apply pressure in proportion to that amount.
      *
      * If there is unutilized protection, the cgroup will be fully
      * shielded from reclaim, but we do return a smaller value for
      * protection than what the group could enjoy in theory. This
      * is okay. With the overcommit distribution above, effective
      * protection is always dependent on how memory is actually
      * consumed among the siblings anyway.
      */
     ep = protected;
 
     /*
      * If the children aren't claiming (all of) the protection
      * afforded to them by the parent, distribute the remainder in
      * proportion to the (unprotected) memory of each cgroup. That
      * way, cgroups that aren't explicitly prioritized wrt each
      * other compete freely over the allowance, but they are
      * collectively protected from neighboring trees.
      *
      * We're using unprotected memory for the weight so that if
      * some cgroups DO claim explicit protection, we don't protect
      * the same bytes twice.
      *
      * Check both usage and parent_usage against the respective
      * protected values. One should imply the other, but they
      * aren't read atomically - make sure the division is sane.
      */
     if (!(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT))
         return ep;
     if (parent_effective > siblings_protected &&
         parent_usage > siblings_protected &&
         usage > protected) {
         unsigned long unclaimed;
 
         unclaimed = parent_effective - siblings_protected;
         unclaimed *= usage - protected;
         unclaimed /= parent_usage - siblings_protected;
 
         ep += unclaimed;
     }
 
     return ep;
 }
 
 /**
  * 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)
 {
     unsigned long usage, parent_usage;
     struct mem_cgroup *parent;
 
     if (mem_cgroup_disabled())
         return;
 
     if (!root)
         root = root_mem_cgroup;
 
     /*
      * Effective values of the reclaim targets are ignored so they
      * can be stale. Have a look at mem_cgroup_protection for more
      * details.
      * TODO: calculation should be more robust so that we do not need
      * that special casing.
      */
     if (memcg == root)
         return;
 
     usage = page_counter_read(&memcg->memory);
     if (!usage)
         return;
 
     parent = parent_mem_cgroup(memcg);
 
     if (parent == root) {
         memcg->memory.emin = READ_ONCE(memcg->memory.min);
         memcg->memory.elow = READ_ONCE(memcg->memory.low);
         return;
     }
 
     parent_usage = page_counter_read(&parent->memory);
 
     WRITE_ONCE(memcg->memory.emin, effective_protection(usage, parent_usage,
             READ_ONCE(memcg->memory.min),
             READ_ONCE(parent->memory.emin),
             atomic_long_read(&parent->memory.children_min_usage)));
 
     WRITE_ONCE(memcg->memory.elow, effective_protection(usage, parent_usage,
             READ_ONCE(memcg->memory.low),
             READ_ONCE(parent->memory.elow),
             atomic_long_read(&parent->memory.children_low_usage)));
 }
 
 static int charge_memcg(struct folio *folio, struct mem_cgroup *memcg,
             gfp_t gfp)
 {
     long nr_pages = folio_nr_pages(folio);
     int ret;
 
     ret = try_charge(memcg, gfp, nr_pages);
     if (ret)
         goto out;
 
     css_get(&memcg->css);
     commit_charge(folio, memcg);
 
     local_irq_disable();
     mem_cgroup_charge_statistics(memcg, nr_pages);
     memcg_check_events(memcg, folio_nid(folio));
     local_irq_enable();
 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_swapin_charge_page - charge a newly allocated page for swapin
  * @page: page to charge
  * @mm: mm context of the victim
  * @gfp: reclaim mode
  * @entry: swap entry for which the page is allocated
  *
  * This function charges a page allocated for swapin. Please call this before
  * adding the page to the swapcache.
  *
  * Returns 0 on success. Otherwise, an error code is returned.
  */
 int mem_cgroup_swapin_charge_page(struct page *page, struct mm_struct *mm,
                   gfp_t gfp, swp_entry_t entry)
 {
     struct folio *folio = page_folio(page);
     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: swap entry for which the page is charged
  *
  * 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)
 {
     /*
      * 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, 1);
     }
 }
 
 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)
 {
     unsigned long flags;
 
     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)
             memcg_account_kmem(ug->memcg, -ug->nr_kmem);
         memcg_oom_recover(ug->memcg);
     }
 
     local_irq_save(flags);
     __count_memcg_events(ug->memcg, PGPGOUT, ug->pgpgout);
     __this_cpu_add(ug->memcg->vmstats_percpu->nr_page_events, ug->nr_memory);
     memcg_check_events(ug->memcg, ug->nid);
     local_irq_restore(flags);
 
     /* 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++;
 
         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(folio))
         return;
 
     uncharge_gather_clear(&ug);
     uncharge_folio(folio, &ug);
     uncharge_batch(&ug);
 }
 
 /**
  * __mem_cgroup_uncharge_list - uncharge a list of page
  * @page_list: list of pages to uncharge
  *
  * Uncharge a list of pages previously charged with
  * __mem_cgroup_charge().
  */
 void __mem_cgroup_uncharge_list(struct list_head *page_list)
 {
     struct uncharge_gather ug;
     struct folio *folio;
 
     uncharge_gather_clear(&ug);
     list_for_each_entry(folio, page_list, lru)
         uncharge_folio(folio, &ug);
     if (ug.memcg)
         uncharge_batch(&ug);
 }
 
 /**
  * mem_cgroup_migrate - 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_migrate(struct folio *old, struct folio *new)
 {
     struct mem_cgroup *memcg;
     long nr_pages = folio_nr_pages(new);
     unsigned long flags;
 
     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(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);
 
     local_irq_save(flags);
     mem_cgroup_charge_statistics(memcg, nr_pages);
     memcg_check_events(memcg, folio_nid(new));
     local_irq_restore(flags);
 }
 
 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 (memcg == root_mem_cgroup)
         goto out;
     if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !memcg->tcpmem_active)
         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)) {
         struct page_counter *fail;
 
         if (page_counter_try_charge(&memcg->tcpmem, nr_pages, &fail)) {
             memcg->tcpmem_pressure = 0;
             return true;
         }
         memcg->tcpmem_pressure = 1;
         if (gfp_mask & __GFP_NOFAIL) {
             page_counter_charge(&memcg->tcpmem, nr_pages);
             return true;
         }
         return false;
     }
 
     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)) {
         page_counter_uncharge(&memcg->tcpmem, 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;
     }
     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, node;
 
     /*
      * 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);
 
     for_each_node(node) {
         struct mem_cgroup_tree_per_node *rtpn;
 
         rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL,
                     node_online(node) ? node : NUMA_NO_NODE);
 
         rtpn->rb_root = RB_ROOT;
         rtpn->rb_rightmost = NULL;
         spin_lock_init(&rtpn->lock);
         soft_limit_tree.rb_tree_per_node[node] = rtpn;
     }
 
     return 0;
 }
 subsys_initcall(mem_cgroup_init);
 
 #ifdef CONFIG_MEMCG_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(memcg == root_mem_cgroup)) {
             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 (cgroup_subsys_on_dfl(memory_cgrp_subsys))
         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->memcg_data = 0;
 
     if (!mem_cgroup_is_root(memcg))
         page_counter_uncharge(&memcg->memory, nr_entries);
 
     if (!cgroup_memory_noswap && memcg != swap_memcg) {
         if (!mem_cgroup_is_root(swap_memcg))
             page_counter_charge(&swap_memcg->memsw, nr_entries);
         page_counter_uncharge(&memcg->memsw, nr_entries);
     }
 
     /*
      * Interrupts should be disabled here because the caller holds the
      * i_pages lock which is taken with interrupts-off. It is
      * important here to have the interrupts disabled because it is the
      * only synchronisation we have for updating the per-CPU variables.
      */
     memcg_stats_lock();
     mem_cgroup_charge_statistics(memcg, -nr_entries);
     memcg_stats_unlock();
     memcg_check_events(memcg, folio_nid(folio));
 
     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 (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
         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 (!cgroup_memory_noswap && !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 (!cgroup_memory_noswap && !mem_cgroup_is_root(memcg)) {
             if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
                 page_counter_uncharge(&memcg->swap, nr_pages);
             else
                 page_counter_uncharge(&memcg->memsw, 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 (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
         return nr_swap_pages;
     for (; memcg != root_mem_cgroup; 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 page *page)
 {
     struct mem_cgroup *memcg;
 
     VM_BUG_ON_PAGE(!PageLocked(page), page);
 
     if (vm_swap_full())
         return true;
     if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
         return false;
 
     memcg = page_memcg(page);
     if (!memcg)
         return false;
 
     for (; memcg != root_mem_cgroup; 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)
 {
     if (!strcmp(s, "1"))
         cgroup_memory_noswap = false;
     else if (!strcmp(s, "0"))
         cgroup_memory_noswap = true;
     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_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.events",
         .flags = CFTYPE_NOT_ON_ROOT,
         .file_offset = offsetof(struct mem_cgroup, swap_events_file),
         .seq_show = swap_events_show,
     },
     { } /* terminate */
 };
 
 static struct cftype memsw_files[] = {
     {
         .name = "memsw.usage_in_bytes",
         .private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "memsw.max_usage_in_bytes",
         .private = MEMFILE_PRIVATE(_MEMSWAP, RES_MAX_USAGE),
         .write = mem_cgroup_reset,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "memsw.limit_in_bytes",
         .private = MEMFILE_PRIVATE(_MEMSWAP, RES_LIMIT),
         .write = mem_cgroup_write,
         .read_u64 = mem_cgroup_read_u64,
     },
     {
         .name = "memsw.failcnt",
         .private = MEMFILE_PRIVATE(_MEMSWAP, RES_FAILCNT),
         .write = mem_cgroup_reset,
         .read_u64 = mem_cgroup_read_u64,
     },
     { },    /* terminate */
 };
 
 #if defined(CONFIG_MEMCG_KMEM) && defined(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 occured, 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; memcg != root_mem_cgroup;
          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;
         }
 
         cgroup_rstat_flush(memcg->css.cgroup);
         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_swap() 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();
 }
 
 static u64 zswap_current_read(struct cgroup_subsys_state *css,
                   struct cftype *cft)
 {
     cgroup_rstat_flush(css->cgroup);
     return memcg_page_state(mem_cgroup_from_css(css), 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 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,
     },
     { } /* terminate */
 };
 #endif /* CONFIG_MEMCG_KMEM && CONFIG_ZSWAP */
 
 /*
  * If mem_cgroup_swap_init() is implemented as a subsys_initcall()
  * instead of a core_initcall(), this could mean cgroup_memory_noswap still
  * remains set to false even when memcg is disabled via "cgroup_disable=memory"
  * boot parameter. This may result in premature OOPS inside
  * mem_cgroup_get_nr_swap_pages() function in corner cases.
  */
 static int __init mem_cgroup_swap_init(void)
 {
     /* No memory control -> no swap control */
     if (mem_cgroup_disabled())
         cgroup_memory_noswap = true;
 
     if (cgroup_memory_noswap)
         return 0;
 
     WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, swap_files));
     WARN_ON(cgroup_add_legacy_cftypes(&memory_cgrp_subsys, memsw_files));
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
     WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, zswap_files));
 #endif
     return 0;
 }
 core_initcall(mem_cgroup_swap_init);
 
 #endif /* CONFIG_MEMCG_SWAP */