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	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-only
 /*
  *  linux/mm/vmstat.c
  *
  *  Manages VM statistics
  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  *
  *  zoned VM statistics
  *  Copyright (C) 2006 Silicon Graphics, Inc.,
  *      Christoph Lameter <christoph@lameter.com>
  *  Copyright (C) 2008-2014 Christoph Lameter
  */
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/err.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/cpu.h>
 #include <linux/cpumask.h>
 #include <linux/vmstat.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <linux/debugfs.h>
 #include <linux/sched.h>
 #include <linux/math64.h>
 #include <linux/writeback.h>
 #include <linux/compaction.h>
 #include <linux/mm_inline.h>
 #include <linux/page_ext.h>
 #include <linux/page_owner.h>
 #include <linux/migrate.h>
 
 #include "internal.h"
 
 #ifdef CONFIG_NUMA
 int sysctl_vm_numa_stat = ENABLE_NUMA_STAT;
 
 /* zero numa counters within a zone */
 static void zero_zone_numa_counters(struct zone *zone)
 {
     int item, cpu;
 
     for (item = 0; item < NR_VM_NUMA_EVENT_ITEMS; item++) {
         atomic_long_set(&zone->vm_numa_event[item], 0);
         for_each_online_cpu(cpu) {
             per_cpu_ptr(zone->per_cpu_zonestats, cpu)->vm_numa_event[item]
                         = 0;
         }
     }
 }
 
 /* zero numa counters of all the populated zones */
 static void zero_zones_numa_counters(void)
 {
     struct zone *zone;
 
     for_each_populated_zone(zone)
         zero_zone_numa_counters(zone);
 }
 
 /* zero global numa counters */
 static void zero_global_numa_counters(void)
 {
     int item;
 
     for (item = 0; item < NR_VM_NUMA_EVENT_ITEMS; item++)
         atomic_long_set(&vm_numa_event[item], 0);
 }
 
 static void invalid_numa_statistics(void)
 {
     zero_zones_numa_counters();
     zero_global_numa_counters();
 }
 
 static DEFINE_MUTEX(vm_numa_stat_lock);
 
 int sysctl_vm_numa_stat_handler(struct ctl_table *table, int write,
         void *buffer, size_t *length, loff_t *ppos)
 {
     int ret, oldval;
 
     mutex_lock(&vm_numa_stat_lock);
     if (write)
         oldval = sysctl_vm_numa_stat;
     ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
     if (ret || !write)
         goto out;
 
     if (oldval == sysctl_vm_numa_stat)
         goto out;
     else if (sysctl_vm_numa_stat == ENABLE_NUMA_STAT) {
         static_branch_enable(&vm_numa_stat_key);
         pr_info("enable numa statistics\n");
     } else {
         static_branch_disable(&vm_numa_stat_key);
         invalid_numa_statistics();
         pr_info("disable numa statistics, and clear numa counters\n");
     }
 
 out:
     mutex_unlock(&vm_numa_stat_lock);
     return ret;
 }
 #endif
 
 #ifdef CONFIG_VM_EVENT_COUNTERS
 DEFINE_PER_CPU(struct vm_event_state, vm_event_states) = {{0}};
 EXPORT_PER_CPU_SYMBOL(vm_event_states);
 
 static void sum_vm_events(unsigned long *ret)
 {
     int cpu;
     int i;
 
     memset(ret, 0, NR_VM_EVENT_ITEMS * sizeof(unsigned long));
 
     for_each_online_cpu(cpu) {
         struct vm_event_state *this = &per_cpu(vm_event_states, cpu);
 
         for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
             ret[i] += this->event[i];
     }
 }
 
 /*
  * Accumulate the vm event counters across all CPUs.
  * The result is unavoidably approximate - it can change
  * during and after execution of this function.
 */
 void all_vm_events(unsigned long *ret)
 {
     cpus_read_lock();
     sum_vm_events(ret);
     cpus_read_unlock();
 }
 EXPORT_SYMBOL_GPL(all_vm_events);
 
 /*
  * Fold the foreign cpu events into our own.
  *
  * This is adding to the events on one processor
  * but keeps the global counts constant.
  */
 void vm_events_fold_cpu(int cpu)
 {
     struct vm_event_state *fold_state = &per_cpu(vm_event_states, cpu);
     int i;
 
     for (i = 0; i < NR_VM_EVENT_ITEMS; i++) {
         count_vm_events(i, fold_state->event[i]);
         fold_state->event[i] = 0;
     }
 }
 
 #endif /* CONFIG_VM_EVENT_COUNTERS */
 
 /*
  * Manage combined zone based / global counters
  *
  * vm_stat contains the global counters
  */
 atomic_long_t vm_zone_stat[NR_VM_ZONE_STAT_ITEMS] __cacheline_aligned_in_smp;
 atomic_long_t vm_node_stat[NR_VM_NODE_STAT_ITEMS] __cacheline_aligned_in_smp;
 atomic_long_t vm_numa_event[NR_VM_NUMA_EVENT_ITEMS] __cacheline_aligned_in_smp;
 EXPORT_SYMBOL(vm_zone_stat);
 EXPORT_SYMBOL(vm_node_stat);
 
 #ifdef CONFIG_NUMA
 static void fold_vm_zone_numa_events(struct zone *zone)
 {
     unsigned long zone_numa_events[NR_VM_NUMA_EVENT_ITEMS] = { 0, };
     int cpu;
     enum numa_stat_item item;
 
     for_each_online_cpu(cpu) {
         struct per_cpu_zonestat *pzstats;
 
         pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
         for (item = 0; item < NR_VM_NUMA_EVENT_ITEMS; item++)
             zone_numa_events[item] += xchg(&pzstats->vm_numa_event[item], 0);
     }
 
     for (item = 0; item < NR_VM_NUMA_EVENT_ITEMS; item++)
         zone_numa_event_add(zone_numa_events[item], zone, item);
 }
 
 void fold_vm_numa_events(void)
 {
     struct zone *zone;
 
     for_each_populated_zone(zone)
         fold_vm_zone_numa_events(zone);
 }
 #endif
 
 #ifdef CONFIG_SMP
 
 int calculate_pressure_threshold(struct zone *zone)
 {
     int threshold;
     int watermark_distance;
 
     /*
      * As vmstats are not up to date, there is drift between the estimated
      * and real values. For high thresholds and a high number of CPUs, it
      * is possible for the min watermark to be breached while the estimated
      * value looks fine. The pressure threshold is a reduced value such
      * that even the maximum amount of drift will not accidentally breach
      * the min watermark
      */
     watermark_distance = low_wmark_pages(zone) - min_wmark_pages(zone);
     threshold = max(1, (int)(watermark_distance / num_online_cpus()));
 
     /*
      * Maximum threshold is 125
      */
     threshold = min(125, threshold);
 
     return threshold;
 }
 
 int calculate_normal_threshold(struct zone *zone)
 {
     int threshold;
     int mem;    /* memory in 128 MB units */
 
     /*
      * The threshold scales with the number of processors and the amount
      * of memory per zone. More memory means that we can defer updates for
      * longer, more processors could lead to more contention.
      * fls() is used to have a cheap way of logarithmic scaling.
      *
      * Some sample thresholds:
      *
      * Threshold    Processors  (fls)   Zonesize    fls(mem)+1
      * ------------------------------------------------------------------
      * 8        1       1   0.9-1 GB    4
      * 16       2       2   0.9-1 GB    4
      * 20       2       2   1-2 GB      5
      * 24       2       2   2-4 GB      6
      * 28       2       2   4-8 GB      7
      * 32       2       2   8-16 GB     8
      * 4        2       2   <128M       1
      * 30       4       3   2-4 GB      5
      * 48       4       3   8-16 GB     8
      * 32       8       4   1-2 GB      4
      * 32       8       4   0.9-1GB     4
      * 10       16      5   <128M       1
      * 40       16      5   900M        4
      * 70       64      7   2-4 GB      5
      * 84       64      7   4-8 GB      6
      * 108      512     9   4-8 GB      6
      * 125      1024        10  8-16 GB     8
      * 125      1024        10  16-32 GB    9
      */
 
     mem = zone_managed_pages(zone) >> (27 - PAGE_SHIFT);
 
     threshold = 2 * fls(num_online_cpus()) * (1 + fls(mem));
 
     /*
      * Maximum threshold is 125
      */
     threshold = min(125, threshold);
 
     return threshold;
 }
 
 /*
  * Refresh the thresholds for each zone.
  */
 void refresh_zone_stat_thresholds(void)
 {
     struct pglist_data *pgdat;
     struct zone *zone;
     int cpu;
     int threshold;
 
     /* Zero current pgdat thresholds */
     for_each_online_pgdat(pgdat) {
         for_each_online_cpu(cpu) {
             per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold = 0;
         }
     }
 
     for_each_populated_zone(zone) {
         struct pglist_data *pgdat = zone->zone_pgdat;
         unsigned long max_drift, tolerate_drift;
 
         threshold = calculate_normal_threshold(zone);
 
         for_each_online_cpu(cpu) {
             int pgdat_threshold;
 
             per_cpu_ptr(zone->per_cpu_zonestats, cpu)->stat_threshold
                             = threshold;
 
             /* Base nodestat threshold on the largest populated zone. */
             pgdat_threshold = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold;
             per_cpu_ptr(pgdat->per_cpu_nodestats, cpu)->stat_threshold
                 = max(threshold, pgdat_threshold);
         }
 
         /*
          * Only set percpu_drift_mark if there is a danger that
          * NR_FREE_PAGES reports the low watermark is ok when in fact
          * the min watermark could be breached by an allocation
          */
         tolerate_drift = low_wmark_pages(zone) - min_wmark_pages(zone);
         max_drift = num_online_cpus() * threshold;
         if (max_drift > tolerate_drift)
             zone->percpu_drift_mark = high_wmark_pages(zone) +
                     max_drift;
     }
 }
 
 void set_pgdat_percpu_threshold(pg_data_t *pgdat,
                 int (*calculate_pressure)(struct zone *))
 {
     struct zone *zone;
     int cpu;
     int threshold;
     int i;
 
     for (i = 0; i < pgdat->nr_zones; i++) {
         zone = &pgdat->node_zones[i];
         if (!zone->percpu_drift_mark)
             continue;
 
         threshold = (*calculate_pressure)(zone);
         for_each_online_cpu(cpu)
             per_cpu_ptr(zone->per_cpu_zonestats, cpu)->stat_threshold
                             = threshold;
     }
 }
 
 /*
  * For use when we know that interrupts are disabled,
  * or when we know that preemption is disabled and that
  * particular counter cannot be updated from interrupt context.
  */
 void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
                long delta)
 {
     struct per_cpu_zonestat __percpu *pcp = zone->per_cpu_zonestats;
     s8 __percpu *p = pcp->vm_stat_diff + item;
     long x;
     long t;
 
     /*
      * Accurate vmstat updates require a RMW. On !PREEMPT_RT kernels,
      * atomicity is provided by IRQs being disabled -- either explicitly
      * or via local_lock_irq. On PREEMPT_RT, local_lock_irq only disables
      * CPU migrations and preemption potentially corrupts a counter so
      * disable preemption.
      */
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_disable();
 
     x = delta + __this_cpu_read(*p);
 
     t = __this_cpu_read(pcp->stat_threshold);
 
     if (unlikely(abs(x) > t)) {
         zone_page_state_add(x, zone, item);
         x = 0;
     }
     __this_cpu_write(*p, x);
 
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_enable();
 }
 EXPORT_SYMBOL(__mod_zone_page_state);
 
 void __mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
                 long delta)
 {
     struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats;
     s8 __percpu *p = pcp->vm_node_stat_diff + item;
     long x;
     long t;
 
     if (vmstat_item_in_bytes(item)) {
         /*
          * Only cgroups use subpage accounting right now; at
          * the global level, these items still change in
          * multiples of whole pages. Store them as pages
          * internally to keep the per-cpu counters compact.
          */
         VM_WARN_ON_ONCE(delta & (PAGE_SIZE - 1));
         delta >>= PAGE_SHIFT;
     }
 
     /* See __mod_node_page_state */
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_disable();
 
     x = delta + __this_cpu_read(*p);
 
     t = __this_cpu_read(pcp->stat_threshold);
 
     if (unlikely(abs(x) > t)) {
         node_page_state_add(x, pgdat, item);
         x = 0;
     }
     __this_cpu_write(*p, x);
 
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_enable();
 }
 EXPORT_SYMBOL(__mod_node_page_state);
 
 /*
  * Optimized increment and decrement functions.
  *
  * These are only for a single page and therefore can take a struct page *
  * argument instead of struct zone *. This allows the inclusion of the code
  * generated for page_zone(page) into the optimized functions.
  *
  * No overflow check is necessary and therefore the differential can be
  * incremented or decremented in place which may allow the compilers to
  * generate better code.
  * The increment or decrement is known and therefore one boundary check can
  * be omitted.
  *
  * NOTE: These functions are very performance sensitive. Change only
  * with care.
  *
  * Some processors have inc/dec instructions that are atomic vs an interrupt.
  * However, the code must first determine the differential location in a zone
  * based on the processor number and then inc/dec the counter. There is no
  * guarantee without disabling preemption that the processor will not change
  * in between and therefore the atomicity vs. interrupt cannot be exploited
  * in a useful way here.
  */
 void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
 {
     struct per_cpu_zonestat __percpu *pcp = zone->per_cpu_zonestats;
     s8 __percpu *p = pcp->vm_stat_diff + item;
     s8 v, t;
 
     /* See __mod_node_page_state */
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_disable();
 
     v = __this_cpu_inc_return(*p);
     t = __this_cpu_read(pcp->stat_threshold);
     if (unlikely(v > t)) {
         s8 overstep = t >> 1;
 
         zone_page_state_add(v + overstep, zone, item);
         __this_cpu_write(*p, -overstep);
     }
 
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_enable();
 }
 
 void __inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
 {
     struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats;
     s8 __percpu *p = pcp->vm_node_stat_diff + item;
     s8 v, t;
 
     VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));
 
     /* See __mod_node_page_state */
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_disable();
 
     v = __this_cpu_inc_return(*p);
     t = __this_cpu_read(pcp->stat_threshold);
     if (unlikely(v > t)) {
         s8 overstep = t >> 1;
 
         node_page_state_add(v + overstep, pgdat, item);
         __this_cpu_write(*p, -overstep);
     }
 
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_enable();
 }
 
 void __inc_zone_page_state(struct page *page, enum zone_stat_item item)
 {
     __inc_zone_state(page_zone(page), item);
 }
 EXPORT_SYMBOL(__inc_zone_page_state);
 
 void __inc_node_page_state(struct page *page, enum node_stat_item item)
 {
     __inc_node_state(page_pgdat(page), item);
 }
 EXPORT_SYMBOL(__inc_node_page_state);
 
 void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
 {
     struct per_cpu_zonestat __percpu *pcp = zone->per_cpu_zonestats;
     s8 __percpu *p = pcp->vm_stat_diff + item;
     s8 v, t;
 
     /* See __mod_node_page_state */
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_disable();
 
     v = __this_cpu_dec_return(*p);
     t = __this_cpu_read(pcp->stat_threshold);
     if (unlikely(v < - t)) {
         s8 overstep = t >> 1;
 
         zone_page_state_add(v - overstep, zone, item);
         __this_cpu_write(*p, overstep);
     }
 
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_enable();
 }
 
 void __dec_node_state(struct pglist_data *pgdat, enum node_stat_item item)
 {
     struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats;
     s8 __percpu *p = pcp->vm_node_stat_diff + item;
     s8 v, t;
 
     VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));
 
     /* See __mod_node_page_state */
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_disable();
 
     v = __this_cpu_dec_return(*p);
     t = __this_cpu_read(pcp->stat_threshold);
     if (unlikely(v < - t)) {
         s8 overstep = t >> 1;
 
         node_page_state_add(v - overstep, pgdat, item);
         __this_cpu_write(*p, overstep);
     }
 
     if (IS_ENABLED(CONFIG_PREEMPT_RT))
         preempt_enable();
 }
 
 void __dec_zone_page_state(struct page *page, enum zone_stat_item item)
 {
     __dec_zone_state(page_zone(page), item);
 }
 EXPORT_SYMBOL(__dec_zone_page_state);
 
 void __dec_node_page_state(struct page *page, enum node_stat_item item)
 {
     __dec_node_state(page_pgdat(page), item);
 }
 EXPORT_SYMBOL(__dec_node_page_state);
 
 #ifdef CONFIG_HAVE_CMPXCHG_LOCAL
 /*
  * If we have cmpxchg_local support then we do not need to incur the overhead
  * that comes with local_irq_save/restore if we use this_cpu_cmpxchg.
  *
  * mod_state() modifies the zone counter state through atomic per cpu
  * operations.
  *
  * Overstep mode specifies how overstep should handled:
  *     0       No overstepping
  *     1       Overstepping half of threshold
  *     -1      Overstepping minus half of threshold
 */
 static inline void mod_zone_state(struct zone *zone,
        enum zone_stat_item item, long delta, int overstep_mode)
 {
     struct per_cpu_zonestat __percpu *pcp = zone->per_cpu_zonestats;
     s8 __percpu *p = pcp->vm_stat_diff + item;
     long o, n, t, z;
 
     do {
         z = 0;  /* overflow to zone counters */
 
         /*
          * The fetching of the stat_threshold is racy. We may apply
          * a counter threshold to the wrong the cpu if we get
          * rescheduled while executing here. However, the next
          * counter update will apply the threshold again and
          * therefore bring the counter under the threshold again.
          *
          * Most of the time the thresholds are the same anyways
          * for all cpus in a zone.
          */
         t = this_cpu_read(pcp->stat_threshold);
 
         o = this_cpu_read(*p);
         n = delta + o;
 
         if (abs(n) > t) {
             int os = overstep_mode * (t >> 1) ;
 
             /* Overflow must be added to zone counters */
             z = n + os;
             n = -os;
         }
     } while (this_cpu_cmpxchg(*p, o, n) != o);
 
     if (z)
         zone_page_state_add(z, zone, item);
 }
 
 void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
              long delta)
 {
     mod_zone_state(zone, item, delta, 0);
 }
 EXPORT_SYMBOL(mod_zone_page_state);
 
 void inc_zone_page_state(struct page *page, enum zone_stat_item item)
 {
     mod_zone_state(page_zone(page), item, 1, 1);
 }
 EXPORT_SYMBOL(inc_zone_page_state);
 
 void dec_zone_page_state(struct page *page, enum zone_stat_item item)
 {
     mod_zone_state(page_zone(page), item, -1, -1);
 }
 EXPORT_SYMBOL(dec_zone_page_state);
 
 static inline void mod_node_state(struct pglist_data *pgdat,
        enum node_stat_item item, int delta, int overstep_mode)
 {
     struct per_cpu_nodestat __percpu *pcp = pgdat->per_cpu_nodestats;
     s8 __percpu *p = pcp->vm_node_stat_diff + item;
     long o, n, t, z;
 
     if (vmstat_item_in_bytes(item)) {
         /*
          * Only cgroups use subpage accounting right now; at
          * the global level, these items still change in
          * multiples of whole pages. Store them as pages
          * internally to keep the per-cpu counters compact.
          */
         VM_WARN_ON_ONCE(delta & (PAGE_SIZE - 1));
         delta >>= PAGE_SHIFT;
     }
 
     do {
         z = 0;  /* overflow to node counters */
 
         /*
          * The fetching of the stat_threshold is racy. We may apply
          * a counter threshold to the wrong the cpu if we get
          * rescheduled while executing here. However, the next
          * counter update will apply the threshold again and
          * therefore bring the counter under the threshold again.
          *
          * Most of the time the thresholds are the same anyways
          * for all cpus in a node.
          */
         t = this_cpu_read(pcp->stat_threshold);
 
         o = this_cpu_read(*p);
         n = delta + o;
 
         if (abs(n) > t) {
             int os = overstep_mode * (t >> 1) ;
 
             /* Overflow must be added to node counters */
             z = n + os;
             n = -os;
         }
     } while (this_cpu_cmpxchg(*p, o, n) != o);
 
     if (z)
         node_page_state_add(z, pgdat, item);
 }
 
 void mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
                     long delta)
 {
     mod_node_state(pgdat, item, delta, 0);
 }
 EXPORT_SYMBOL(mod_node_page_state);
 
 void inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
 {
     mod_node_state(pgdat, item, 1, 1);
 }
 
 void inc_node_page_state(struct page *page, enum node_stat_item item)
 {
     mod_node_state(page_pgdat(page), item, 1, 1);
 }
 EXPORT_SYMBOL(inc_node_page_state);
 
 void dec_node_page_state(struct page *page, enum node_stat_item item)
 {
     mod_node_state(page_pgdat(page), item, -1, -1);
 }
 EXPORT_SYMBOL(dec_node_page_state);
 #else
 /*
  * Use interrupt disable to serialize counter updates
  */
 void mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
              long delta)
 {
     unsigned long flags;
 
     local_irq_save(flags);
     __mod_zone_page_state(zone, item, delta);
     local_irq_restore(flags);
 }
 EXPORT_SYMBOL(mod_zone_page_state);
 
 void inc_zone_page_state(struct page *page, enum zone_stat_item item)
 {
     unsigned long flags;
     struct zone *zone;
 
     zone = page_zone(page);
     local_irq_save(flags);
     __inc_zone_state(zone, item);
     local_irq_restore(flags);
 }
 EXPORT_SYMBOL(inc_zone_page_state);
 
 void dec_zone_page_state(struct page *page, enum zone_stat_item item)
 {
     unsigned long flags;
 
     local_irq_save(flags);
     __dec_zone_page_state(page, item);
     local_irq_restore(flags);
 }
 EXPORT_SYMBOL(dec_zone_page_state);
 
 void inc_node_state(struct pglist_data *pgdat, enum node_stat_item item)
 {
     unsigned long flags;
 
     local_irq_save(flags);
     __inc_node_state(pgdat, item);
     local_irq_restore(flags);
 }
 EXPORT_SYMBOL(inc_node_state);
 
 void mod_node_page_state(struct pglist_data *pgdat, enum node_stat_item item,
                     long delta)
 {
     unsigned long flags;
 
     local_irq_save(flags);
     __mod_node_page_state(pgdat, item, delta);
     local_irq_restore(flags);
 }
 EXPORT_SYMBOL(mod_node_page_state);
 
 void inc_node_page_state(struct page *page, enum node_stat_item item)
 {
     unsigned long flags;
     struct pglist_data *pgdat;
 
     pgdat = page_pgdat(page);
     local_irq_save(flags);
     __inc_node_state(pgdat, item);
     local_irq_restore(flags);
 }
 EXPORT_SYMBOL(inc_node_page_state);
 
 void dec_node_page_state(struct page *page, enum node_stat_item item)
 {
     unsigned long flags;
 
     local_irq_save(flags);
     __dec_node_page_state(page, item);
     local_irq_restore(flags);
 }
 EXPORT_SYMBOL(dec_node_page_state);
 #endif
 
 /*
  * Fold a differential into the global counters.
  * Returns the number of counters updated.
  */
 static int fold_diff(int *zone_diff, int *node_diff)
 {
     int i;
     int changes = 0;
 
     for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
         if (zone_diff[i]) {
             atomic_long_add(zone_diff[i], &vm_zone_stat[i]);
             changes++;
     }
 
     for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
         if (node_diff[i]) {
             atomic_long_add(node_diff[i], &vm_node_stat[i]);
             changes++;
     }
     return changes;
 }
 
 /*
  * Update the zone counters for the current cpu.
  *
  * Note that refresh_cpu_vm_stats strives to only access
  * node local memory. The per cpu pagesets on remote zones are placed
  * in the memory local to the processor using that pageset. So the
  * loop over all zones will access a series of cachelines local to
  * the processor.
  *
  * The call to zone_page_state_add updates the cachelines with the
  * statistics in the remote zone struct as well as the global cachelines
  * with the global counters. These could cause remote node cache line
  * bouncing and will have to be only done when necessary.
  *
  * The function returns the number of global counters updated.
  */
 static int refresh_cpu_vm_stats(bool do_pagesets)
 {
     struct pglist_data *pgdat;
     struct zone *zone;
     int i;
     int global_zone_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
     int global_node_diff[NR_VM_NODE_STAT_ITEMS] = { 0, };
     int changes = 0;
 
     for_each_populated_zone(zone) {
         struct per_cpu_zonestat __percpu *pzstats = zone->per_cpu_zonestats;
 #ifdef CONFIG_NUMA
         struct per_cpu_pages __percpu *pcp = zone->per_cpu_pageset;
 #endif
 
         for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
             int v;
 
             v = this_cpu_xchg(pzstats->vm_stat_diff[i], 0);
             if (v) {
 
                 atomic_long_add(v, &zone->vm_stat[i]);
                 global_zone_diff[i] += v;
 #ifdef CONFIG_NUMA
                 /* 3 seconds idle till flush */
                 __this_cpu_write(pcp->expire, 3);
 #endif
             }
         }
 #ifdef CONFIG_NUMA
 
         if (do_pagesets) {
             cond_resched();
             /*
              * Deal with draining the remote pageset of this
              * processor
              *
              * Check if there are pages remaining in this pageset
              * if not then there is nothing to expire.
              */
             if (!__this_cpu_read(pcp->expire) ||
                    !__this_cpu_read(pcp->count))
                 continue;
 
             /*
              * We never drain zones local to this processor.
              */
             if (zone_to_nid(zone) == numa_node_id()) {
                 __this_cpu_write(pcp->expire, 0);
                 continue;
             }
 
             if (__this_cpu_dec_return(pcp->expire))
                 continue;
 
             if (__this_cpu_read(pcp->count)) {
                 drain_zone_pages(zone, this_cpu_ptr(pcp));
                 changes++;
             }
         }
 #endif
     }
 
     for_each_online_pgdat(pgdat) {
         struct per_cpu_nodestat __percpu *p = pgdat->per_cpu_nodestats;
 
         for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
             int v;
 
             v = this_cpu_xchg(p->vm_node_stat_diff[i], 0);
             if (v) {
                 atomic_long_add(v, &pgdat->vm_stat[i]);
                 global_node_diff[i] += v;
             }
         }
     }
 
     changes += fold_diff(global_zone_diff, global_node_diff);
     return changes;
 }
 
 /*
  * Fold the data for an offline cpu into the global array.
  * There cannot be any access by the offline cpu and therefore
  * synchronization is simplified.
  */
 void cpu_vm_stats_fold(int cpu)
 {
     struct pglist_data *pgdat;
     struct zone *zone;
     int i;
     int global_zone_diff[NR_VM_ZONE_STAT_ITEMS] = { 0, };
     int global_node_diff[NR_VM_NODE_STAT_ITEMS] = { 0, };
 
     for_each_populated_zone(zone) {
         struct per_cpu_zonestat *pzstats;
 
         pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
 
         for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
             if (pzstats->vm_stat_diff[i]) {
                 int v;
 
                 v = pzstats->vm_stat_diff[i];
                 pzstats->vm_stat_diff[i] = 0;
                 atomic_long_add(v, &zone->vm_stat[i]);
                 global_zone_diff[i] += v;
             }
         }
 #ifdef CONFIG_NUMA
         for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++) {
             if (pzstats->vm_numa_event[i]) {
                 unsigned long v;
 
                 v = pzstats->vm_numa_event[i];
                 pzstats->vm_numa_event[i] = 0;
                 zone_numa_event_add(v, zone, i);
             }
         }
 #endif
     }
 
     for_each_online_pgdat(pgdat) {
         struct per_cpu_nodestat *p;
 
         p = per_cpu_ptr(pgdat->per_cpu_nodestats, cpu);
 
         for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
             if (p->vm_node_stat_diff[i]) {
                 int v;
 
                 v = p->vm_node_stat_diff[i];
                 p->vm_node_stat_diff[i] = 0;
                 atomic_long_add(v, &pgdat->vm_stat[i]);
                 global_node_diff[i] += v;
             }
     }
 
     fold_diff(global_zone_diff, global_node_diff);
 }
 
 /*
  * this is only called if !populated_zone(zone), which implies no other users of
  * pset->vm_stat_diff[] exist.
  */
 void drain_zonestat(struct zone *zone, struct per_cpu_zonestat *pzstats)
 {
     unsigned long v;
     int i;
 
     for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
         if (pzstats->vm_stat_diff[i]) {
             v = pzstats->vm_stat_diff[i];
             pzstats->vm_stat_diff[i] = 0;
             zone_page_state_add(v, zone, i);
         }
     }
 
 #ifdef CONFIG_NUMA
     for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++) {
         if (pzstats->vm_numa_event[i]) {
             v = pzstats->vm_numa_event[i];
             pzstats->vm_numa_event[i] = 0;
             zone_numa_event_add(v, zone, i);
         }
     }
 #endif
 }
 #endif
 
 #ifdef CONFIG_NUMA
 /*
  * Determine the per node value of a stat item. This function
  * is called frequently in a NUMA machine, so try to be as
  * frugal as possible.
  */
 unsigned long sum_zone_node_page_state(int node,
                  enum zone_stat_item item)
 {
     struct zone *zones = NODE_DATA(node)->node_zones;
     int i;
     unsigned long count = 0;
 
     for (i = 0; i < MAX_NR_ZONES; i++)
         count += zone_page_state(zones + i, item);
 
     return count;
 }
 
 /* Determine the per node value of a numa stat item. */
 unsigned long sum_zone_numa_event_state(int node,
                  enum numa_stat_item item)
 {
     struct zone *zones = NODE_DATA(node)->node_zones;
     unsigned long count = 0;
     int i;
 
     for (i = 0; i < MAX_NR_ZONES; i++)
         count += zone_numa_event_state(zones + i, item);
 
     return count;
 }
 
 /*
  * Determine the per node value of a stat item.
  */
 unsigned long node_page_state_pages(struct pglist_data *pgdat,
                     enum node_stat_item item)
 {
     long x = atomic_long_read(&pgdat->vm_stat[item]);
 #ifdef CONFIG_SMP
     if (x < 0)
         x = 0;
 #endif
     return x;
 }
 
 unsigned long node_page_state(struct pglist_data *pgdat,
                   enum node_stat_item item)
 {
     VM_WARN_ON_ONCE(vmstat_item_in_bytes(item));
 
     return node_page_state_pages(pgdat, item);
 }
 #endif
 
 #ifdef CONFIG_COMPACTION
 
 struct contig_page_info {
     unsigned long free_pages;
     unsigned long free_blocks_total;
     unsigned long free_blocks_suitable;
 };
 
 /*
  * Calculate the number of free pages in a zone, how many contiguous
  * pages are free and how many are large enough to satisfy an allocation of
  * the target size. Note that this function makes no attempt to estimate
  * how many suitable free blocks there *might* be if MOVABLE pages were
  * migrated. Calculating that is possible, but expensive and can be
  * figured out from userspace
  */
 static void fill_contig_page_info(struct zone *zone,
                 unsigned int suitable_order,
                 struct contig_page_info *info)
 {
     unsigned int order;
 
     info->free_pages = 0;
     info->free_blocks_total = 0;
     info->free_blocks_suitable = 0;
 
     for (order = 0; order < MAX_ORDER; order++) {
         unsigned long blocks;
 
         /*
          * Count number of free blocks.
          *
          * Access to nr_free is lockless as nr_free is used only for
          * diagnostic purposes. Use data_race to avoid KCSAN warning.
          */
         blocks = data_race(zone->free_area[order].nr_free);
         info->free_blocks_total += blocks;
 
         /* Count free base pages */
         info->free_pages += blocks << order;
 
         /* Count the suitable free blocks */
         if (order >= suitable_order)
             info->free_blocks_suitable += blocks <<
                         (order - suitable_order);
     }
 }
 
 /*
  * A fragmentation index only makes sense if an allocation of a requested
  * size would fail. If that is true, the fragmentation index indicates
  * whether external fragmentation or a lack of memory was the problem.
  * The value can be used to determine if page reclaim or compaction
  * should be used
  */
 static int __fragmentation_index(unsigned int order, struct contig_page_info *info)
 {
     unsigned long requested = 1UL << order;
 
     if (WARN_ON_ONCE(order >= MAX_ORDER))
         return 0;
 
     if (!info->free_blocks_total)
         return 0;
 
     /* Fragmentation index only makes sense when a request would fail */
     if (info->free_blocks_suitable)
         return -1000;
 
     /*
      * Index is between 0 and 1 so return within 3 decimal places
      *
      * 0 => allocation would fail due to lack of memory
      * 1 => allocation would fail due to fragmentation
      */
     return 1000 - div_u64( (1000+(div_u64(info->free_pages * 1000ULL, requested))), info->free_blocks_total);
 }
 
 /*
  * Calculates external fragmentation within a zone wrt the given order.
  * It is defined as the percentage of pages found in blocks of size
  * less than 1 << order. It returns values in range [0, 100].
  */
 unsigned int extfrag_for_order(struct zone *zone, unsigned int order)
 {
     struct contig_page_info info;
 
     fill_contig_page_info(zone, order, &info);
     if (info.free_pages == 0)
         return 0;
 
     return div_u64((info.free_pages -
             (info.free_blocks_suitable << order)) * 100,
             info.free_pages);
 }
 
 /* Same as __fragmentation index but allocs contig_page_info on stack */
 int fragmentation_index(struct zone *zone, unsigned int order)
 {
     struct contig_page_info info;
 
     fill_contig_page_info(zone, order, &info);
     return __fragmentation_index(order, &info);
 }
 #endif
 
 #if defined(CONFIG_PROC_FS) || defined(CONFIG_SYSFS) || \
     defined(CONFIG_NUMA) || defined(CONFIG_MEMCG)
 #ifdef CONFIG_ZONE_DMA
 #define TEXT_FOR_DMA(xx) xx "_dma",
 #else
 #define TEXT_FOR_DMA(xx)
 #endif
 
 #ifdef CONFIG_ZONE_DMA32
 #define TEXT_FOR_DMA32(xx) xx "_dma32",
 #else
 #define TEXT_FOR_DMA32(xx)
 #endif
 
 #ifdef CONFIG_HIGHMEM
 #define TEXT_FOR_HIGHMEM(xx) xx "_high",
 #else
 #define TEXT_FOR_HIGHMEM(xx)
 #endif
 
 #ifdef CONFIG_ZONE_DEVICE
 #define TEXT_FOR_DEVICE(xx) xx "_device",
 #else
 #define TEXT_FOR_DEVICE(xx)
 #endif
 
 #define TEXTS_FOR_ZONES(xx) TEXT_FOR_DMA(xx) TEXT_FOR_DMA32(xx) xx "_normal", \
                     TEXT_FOR_HIGHMEM(xx) xx "_movable", \
                     TEXT_FOR_DEVICE(xx)
 
 const char * const vmstat_text[] = {
     /* enum zone_stat_item counters */
     "nr_free_pages",
     "nr_zone_inactive_anon",
     "nr_zone_active_anon",
     "nr_zone_inactive_file",
     "nr_zone_active_file",
     "nr_zone_unevictable",
     "nr_zone_write_pending",
     "nr_mlock",
     "nr_bounce",
 #if IS_ENABLED(CONFIG_ZSMALLOC)
     "nr_zspages",
 #endif
     "nr_free_cma",
 
     /* enum numa_stat_item counters */
 #ifdef CONFIG_NUMA
     "numa_hit",
     "numa_miss",
     "numa_foreign",
     "numa_interleave",
     "numa_local",
     "numa_other",
 #endif
 
     /* enum node_stat_item counters */
     "nr_inactive_anon",
     "nr_active_anon",
     "nr_inactive_file",
     "nr_active_file",
     "nr_unevictable",
     "nr_slab_reclaimable",
     "nr_slab_unreclaimable",
     "nr_isolated_anon",
     "nr_isolated_file",
     "workingset_nodes",
     "workingset_refault_anon",
     "workingset_refault_file",
     "workingset_activate_anon",
     "workingset_activate_file",
     "workingset_restore_anon",
     "workingset_restore_file",
     "workingset_nodereclaim",
     "nr_anon_pages",
     "nr_mapped",
     "nr_file_pages",
     "nr_dirty",
     "nr_writeback",
     "nr_writeback_temp",
     "nr_shmem",
     "nr_shmem_hugepages",
     "nr_shmem_pmdmapped",
     "nr_file_hugepages",
     "nr_file_pmdmapped",
     "nr_anon_transparent_hugepages",
     "nr_vmscan_write",
     "nr_vmscan_immediate_reclaim",
     "nr_dirtied",
     "nr_written",
     "nr_throttled_written",
     "nr_kernel_misc_reclaimable",
     "nr_foll_pin_acquired",
     "nr_foll_pin_released",
     "nr_kernel_stack",
 #if IS_ENABLED(CONFIG_SHADOW_CALL_STACK)
     "nr_shadow_call_stack",
 #endif
     "nr_page_table_pages",
 #ifdef CONFIG_SWAP
     "nr_swapcached",
 #endif
 #ifdef CONFIG_NUMA_BALANCING
     "pgpromote_success",
 #endif
 
     /* enum writeback_stat_item counters */
     "nr_dirty_threshold",
     "nr_dirty_background_threshold",
 
 #if defined(CONFIG_VM_EVENT_COUNTERS) || defined(CONFIG_MEMCG)
     /* enum vm_event_item counters */
     "pgpgin",
     "pgpgout",
     "pswpin",
     "pswpout",
 
     TEXTS_FOR_ZONES("pgalloc")
     TEXTS_FOR_ZONES("allocstall")
     TEXTS_FOR_ZONES("pgskip")
 
     "pgfree",
     "pgactivate",
     "pgdeactivate",
     "pglazyfree",
 
     "pgfault",
     "pgmajfault",
     "pglazyfreed",
 
     "pgrefill",
     "pgreuse",
     "pgsteal_kswapd",
     "pgsteal_direct",
     "pgdemote_kswapd",
     "pgdemote_direct",
     "pgscan_kswapd",
     "pgscan_direct",
     "pgscan_direct_throttle",
     "pgscan_anon",
     "pgscan_file",
     "pgsteal_anon",
     "pgsteal_file",
 
 #ifdef CONFIG_NUMA
     "zone_reclaim_failed",
 #endif
     "pginodesteal",
     "slabs_scanned",
     "kswapd_inodesteal",
     "kswapd_low_wmark_hit_quickly",
     "kswapd_high_wmark_hit_quickly",
     "pageoutrun",
 
     "pgrotated",
 
     "drop_pagecache",
     "drop_slab",
     "oom_kill",
 
 #ifdef CONFIG_NUMA_BALANCING
     "numa_pte_updates",
     "numa_huge_pte_updates",
     "numa_hint_faults",
     "numa_hint_faults_local",
     "numa_pages_migrated",
 #endif
 #ifdef CONFIG_MIGRATION
     "pgmigrate_success",
     "pgmigrate_fail",
     "thp_migration_success",
     "thp_migration_fail",
     "thp_migration_split",
 #endif
 #ifdef CONFIG_COMPACTION
     "compact_migrate_scanned",
     "compact_free_scanned",
     "compact_isolated",
     "compact_stall",
     "compact_fail",
     "compact_success",
     "compact_daemon_wake",
     "compact_daemon_migrate_scanned",
     "compact_daemon_free_scanned",
 #endif
 
 #ifdef CONFIG_HUGETLB_PAGE
     "htlb_buddy_alloc_success",
     "htlb_buddy_alloc_fail",
 #endif
 #ifdef CONFIG_CMA
     "cma_alloc_success",
     "cma_alloc_fail",
 #endif
     "unevictable_pgs_culled",
     "unevictable_pgs_scanned",
     "unevictable_pgs_rescued",
     "unevictable_pgs_mlocked",
     "unevictable_pgs_munlocked",
     "unevictable_pgs_cleared",
     "unevictable_pgs_stranded",
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
     "thp_fault_alloc",
     "thp_fault_fallback",
     "thp_fault_fallback_charge",
     "thp_collapse_alloc",
     "thp_collapse_alloc_failed",
     "thp_file_alloc",
     "thp_file_fallback",
     "thp_file_fallback_charge",
     "thp_file_mapped",
     "thp_split_page",
     "thp_split_page_failed",
     "thp_deferred_split_page",
     "thp_split_pmd",
     "thp_scan_exceed_none_pte",
     "thp_scan_exceed_swap_pte",
     "thp_scan_exceed_share_pte",
 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
     "thp_split_pud",
 #endif
     "thp_zero_page_alloc",
     "thp_zero_page_alloc_failed",
     "thp_swpout",
     "thp_swpout_fallback",
 #endif
 #ifdef CONFIG_MEMORY_BALLOON
     "balloon_inflate",
     "balloon_deflate",
 #ifdef CONFIG_BALLOON_COMPACTION
     "balloon_migrate",
 #endif
 #endif /* CONFIG_MEMORY_BALLOON */
 #ifdef CONFIG_DEBUG_TLBFLUSH
     "nr_tlb_remote_flush",
     "nr_tlb_remote_flush_received",
     "nr_tlb_local_flush_all",
     "nr_tlb_local_flush_one",
 #endif /* CONFIG_DEBUG_TLBFLUSH */
 
 #ifdef CONFIG_DEBUG_VM_VMACACHE
     "vmacache_find_calls",
     "vmacache_find_hits",
 #endif
 #ifdef CONFIG_SWAP
     "swap_ra",
     "swap_ra_hit",
 #ifdef CONFIG_KSM
     "ksm_swpin_copy",
 #endif
 #endif
 #ifdef CONFIG_KSM
     "cow_ksm",
 #endif
 #ifdef CONFIG_ZSWAP
     "zswpin",
     "zswpout",
 #endif
 #ifdef CONFIG_X86
     "direct_map_level2_splits",
     "direct_map_level3_splits",
 #endif
 #endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
 };
 #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA || CONFIG_MEMCG */
 
 #if (defined(CONFIG_DEBUG_FS) && defined(CONFIG_COMPACTION)) || \
      defined(CONFIG_PROC_FS)
 static void *frag_start(struct seq_file *m, loff_t *pos)
 {
     pg_data_t *pgdat;
     loff_t node = *pos;
 
     for (pgdat = first_online_pgdat();
          pgdat && node;
          pgdat = next_online_pgdat(pgdat))
         --node;
 
     return pgdat;
 }
 
 static void *frag_next(struct seq_file *m, void *arg, loff_t *pos)
 {
     pg_data_t *pgdat = (pg_data_t *)arg;
 
     (*pos)++;
     return next_online_pgdat(pgdat);
 }
 
 static void frag_stop(struct seq_file *m, void *arg)
 {
 }
 
 /*
  * Walk zones in a node and print using a callback.
  * If @assert_populated is true, only use callback for zones that are populated.
  */
 static void walk_zones_in_node(struct seq_file *m, pg_data_t *pgdat,
         bool assert_populated, bool nolock,
         void (*print)(struct seq_file *m, pg_data_t *, struct zone *))
 {
     struct zone *zone;
     struct zone *node_zones = pgdat->node_zones;
     unsigned long flags;
 
     for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
         if (assert_populated && !populated_zone(zone))
             continue;
 
         if (!nolock)
             spin_lock_irqsave(&zone->lock, flags);
         print(m, pgdat, zone);
         if (!nolock)
             spin_unlock_irqrestore(&zone->lock, flags);
     }
 }
 #endif
 
 #ifdef CONFIG_PROC_FS
 static void frag_show_print(struct seq_file *m, pg_data_t *pgdat,
                         struct zone *zone)
 {
     int order;
 
     seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
     for (order = 0; order < MAX_ORDER; ++order)
         /*
          * Access to nr_free is lockless as nr_free is used only for
          * printing purposes. Use data_race to avoid KCSAN warning.
          */
         seq_printf(m, "%6lu ", data_race(zone->free_area[order].nr_free));
     seq_putc(m, '\n');
 }
 
 /*
  * This walks the free areas for each zone.
  */
 static int frag_show(struct seq_file *m, void *arg)
 {
     pg_data_t *pgdat = (pg_data_t *)arg;
     walk_zones_in_node(m, pgdat, true, false, frag_show_print);
     return 0;
 }
 
 static void pagetypeinfo_showfree_print(struct seq_file *m,
                     pg_data_t *pgdat, struct zone *zone)
 {
     int order, mtype;
 
     for (mtype = 0; mtype < MIGRATE_TYPES; mtype++) {
         seq_printf(m, "Node %4d, zone %8s, type %12s ",
                     pgdat->node_id,
                     zone->name,
                     migratetype_names[mtype]);
         for (order = 0; order < MAX_ORDER; ++order) {
             unsigned long freecount = 0;
             struct free_area *area;
             struct list_head *curr;
             bool overflow = false;
 
             area = &(zone->free_area[order]);
 
             list_for_each(curr, &area->free_list[mtype]) {
                 /*
                  * Cap the free_list iteration because it might
                  * be really large and we are under a spinlock
                  * so a long time spent here could trigger a
                  * hard lockup detector. Anyway this is a
                  * debugging tool so knowing there is a handful
                  * of pages of this order should be more than
                  * sufficient.
                  */
                 if (++freecount >= 100000) {
                     overflow = true;
                     break;
                 }
             }
             seq_printf(m, "%s%6lu ", overflow ? ">" : "", freecount);
             spin_unlock_irq(&zone->lock);
             cond_resched();
             spin_lock_irq(&zone->lock);
         }
         seq_putc(m, '\n');
     }
 }
 
 /* Print out the free pages at each order for each migatetype */
 static void pagetypeinfo_showfree(struct seq_file *m, void *arg)
 {
     int order;
     pg_data_t *pgdat = (pg_data_t *)arg;
 
     /* Print header */
     seq_printf(m, "%-43s ", "Free pages count per migrate type at order");
     for (order = 0; order < MAX_ORDER; ++order)
         seq_printf(m, "%6d ", order);
     seq_putc(m, '\n');
 
     walk_zones_in_node(m, pgdat, true, false, pagetypeinfo_showfree_print);
 }
 
 static void pagetypeinfo_showblockcount_print(struct seq_file *m,
                     pg_data_t *pgdat, struct zone *zone)
 {
     int mtype;
     unsigned long pfn;
     unsigned long start_pfn = zone->zone_start_pfn;
     unsigned long end_pfn = zone_end_pfn(zone);
     unsigned long count[MIGRATE_TYPES] = { 0, };
 
     for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
         struct page *page;
 
         page = pfn_to_online_page(pfn);
         if (!page)
             continue;
 
         if (page_zone(page) != zone)
             continue;
 
         mtype = get_pageblock_migratetype(page);
 
         if (mtype < MIGRATE_TYPES)
             count[mtype]++;
     }
 
     /* Print counts */
     seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
     for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
         seq_printf(m, "%12lu ", count[mtype]);
     seq_putc(m, '\n');
 }
 
 /* Print out the number of pageblocks for each migratetype */
 static void pagetypeinfo_showblockcount(struct seq_file *m, void *arg)
 {
     int mtype;
     pg_data_t *pgdat = (pg_data_t *)arg;
 
     seq_printf(m, "\n%-23s", "Number of blocks type ");
     for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
         seq_printf(m, "%12s ", migratetype_names[mtype]);
     seq_putc(m, '\n');
     walk_zones_in_node(m, pgdat, true, false,
         pagetypeinfo_showblockcount_print);
 }
 
 /*
  * Print out the number of pageblocks for each migratetype that contain pages
  * of other types. This gives an indication of how well fallbacks are being
  * contained by rmqueue_fallback(). It requires information from PAGE_OWNER
  * to determine what is going on
  */
 static void pagetypeinfo_showmixedcount(struct seq_file *m, pg_data_t *pgdat)
 {
 #ifdef CONFIG_PAGE_OWNER
     int mtype;
 
     if (!static_branch_unlikely(&page_owner_inited))
         return;
 
     drain_all_pages(NULL);
 
     seq_printf(m, "\n%-23s", "Number of mixed blocks ");
     for (mtype = 0; mtype < MIGRATE_TYPES; mtype++)
         seq_printf(m, "%12s ", migratetype_names[mtype]);
     seq_putc(m, '\n');
 
     walk_zones_in_node(m, pgdat, true, true,
         pagetypeinfo_showmixedcount_print);
 #endif /* CONFIG_PAGE_OWNER */
 }
 
 /*
  * This prints out statistics in relation to grouping pages by mobility.
  * It is expensive to collect so do not constantly read the file.
  */
 static int pagetypeinfo_show(struct seq_file *m, void *arg)
 {
     pg_data_t *pgdat = (pg_data_t *)arg;
 
     /* check memoryless node */
     if (!node_state(pgdat->node_id, N_MEMORY))
         return 0;
 
     seq_printf(m, "Page block order: %d\n", pageblock_order);
     seq_printf(m, "Pages per block:  %lu\n", pageblock_nr_pages);
     seq_putc(m, '\n');
     pagetypeinfo_showfree(m, pgdat);
     pagetypeinfo_showblockcount(m, pgdat);
     pagetypeinfo_showmixedcount(m, pgdat);
 
     return 0;
 }
 
 static const struct seq_operations fragmentation_op = {
     .start  = frag_start,
     .next   = frag_next,
     .stop   = frag_stop,
     .show   = frag_show,
 };
 
 static const struct seq_operations pagetypeinfo_op = {
     .start  = frag_start,
     .next   = frag_next,
     .stop   = frag_stop,
     .show   = pagetypeinfo_show,
 };
 
 static bool is_zone_first_populated(pg_data_t *pgdat, struct zone *zone)
 {
     int zid;
 
     for (zid = 0; zid < MAX_NR_ZONES; zid++) {
         struct zone *compare = &pgdat->node_zones[zid];
 
         if (populated_zone(compare))
             return zone == compare;
     }
 
     return false;
 }
 
 static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
                             struct zone *zone)
 {
     int i;
     seq_printf(m, "Node %d, zone %8s", pgdat->node_id, zone->name);
     if (is_zone_first_populated(pgdat, zone)) {
         seq_printf(m, "\n  per-node stats");
         for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
             unsigned long pages = node_page_state_pages(pgdat, i);
 
             if (vmstat_item_print_in_thp(i))
                 pages /= HPAGE_PMD_NR;
             seq_printf(m, "\n      %-12s %lu", node_stat_name(i),
                    pages);
         }
     }
     seq_printf(m,
            "\n  pages free     %lu"
            "\n        boost    %lu"
            "\n        min      %lu"
            "\n        low      %lu"
            "\n        high     %lu"
            "\n        spanned  %lu"
            "\n        present  %lu"
            "\n        managed  %lu"
            "\n        cma      %lu",
            zone_page_state(zone, NR_FREE_PAGES),
            zone->watermark_boost,
            min_wmark_pages(zone),
            low_wmark_pages(zone),
            high_wmark_pages(zone),
            zone->spanned_pages,
            zone->present_pages,
            zone_managed_pages(zone),
            zone_cma_pages(zone));
 
     seq_printf(m,
            "\n        protection: (%ld",
            zone->lowmem_reserve[0]);
     for (i = 1; i < ARRAY_SIZE(zone->lowmem_reserve); i++)
         seq_printf(m, ", %ld", zone->lowmem_reserve[i]);
     seq_putc(m, ')');
 
     /* If unpopulated, no other information is useful */
     if (!populated_zone(zone)) {
         seq_putc(m, '\n');
         return;
     }
 
     for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
         seq_printf(m, "\n      %-12s %lu", zone_stat_name(i),
                zone_page_state(zone, i));
 
 #ifdef CONFIG_NUMA
     for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++)
         seq_printf(m, "\n      %-12s %lu", numa_stat_name(i),
                zone_numa_event_state(zone, i));
 #endif
 
     seq_printf(m, "\n  pagesets");
     for_each_online_cpu(i) {
         struct per_cpu_pages *pcp;
         struct per_cpu_zonestat __maybe_unused *pzstats;
 
         pcp = per_cpu_ptr(zone->per_cpu_pageset, i);
         seq_printf(m,
                "\n    cpu: %i"
                "\n              count: %i"
                "\n              high:  %i"
                "\n              batch: %i",
                i,
                pcp->count,
                pcp->high,
                pcp->batch);
 #ifdef CONFIG_SMP
         pzstats = per_cpu_ptr(zone->per_cpu_zonestats, i);
         seq_printf(m, "\n  vm stats threshold: %d",
                 pzstats->stat_threshold);
 #endif
     }
     seq_printf(m,
            "\n  node_unreclaimable:  %u"
            "\n  start_pfn:           %lu",
            pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES,
            zone->zone_start_pfn);
     seq_putc(m, '\n');
 }
 
 /*
  * Output information about zones in @pgdat.  All zones are printed regardless
  * of whether they are populated or not: lowmem_reserve_ratio operates on the
  * set of all zones and userspace would not be aware of such zones if they are
  * suppressed here (zoneinfo displays the effect of lowmem_reserve_ratio).
  */
 static int zoneinfo_show(struct seq_file *m, void *arg)
 {
     pg_data_t *pgdat = (pg_data_t *)arg;
     walk_zones_in_node(m, pgdat, false, false, zoneinfo_show_print);
     return 0;
 }
 
 static const struct seq_operations zoneinfo_op = {
     .start  = frag_start, /* iterate over all zones. The same as in
                    * fragmentation. */
     .next   = frag_next,
     .stop   = frag_stop,
     .show   = zoneinfo_show,
 };
 
 #define NR_VMSTAT_ITEMS (NR_VM_ZONE_STAT_ITEMS + \
              NR_VM_NUMA_EVENT_ITEMS + \
              NR_VM_NODE_STAT_ITEMS + \
              NR_VM_WRITEBACK_STAT_ITEMS + \
              (IS_ENABLED(CONFIG_VM_EVENT_COUNTERS) ? \
               NR_VM_EVENT_ITEMS : 0))
 
 static void *vmstat_start(struct seq_file *m, loff_t *pos)
 {
     unsigned long *v;
     int i;
 
     if (*pos >= NR_VMSTAT_ITEMS)
         return NULL;
 
     BUILD_BUG_ON(ARRAY_SIZE(vmstat_text) < NR_VMSTAT_ITEMS);
     fold_vm_numa_events();
     v = kmalloc_array(NR_VMSTAT_ITEMS, sizeof(unsigned long), GFP_KERNEL);
     m->private = v;
     if (!v)
         return ERR_PTR(-ENOMEM);
     for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
         v[i] = global_zone_page_state(i);
     v += NR_VM_ZONE_STAT_ITEMS;
 
 #ifdef CONFIG_NUMA
     for (i = 0; i < NR_VM_NUMA_EVENT_ITEMS; i++)
         v[i] = global_numa_event_state(i);
     v += NR_VM_NUMA_EVENT_ITEMS;
 #endif
 
     for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
         v[i] = global_node_page_state_pages(i);
         if (vmstat_item_print_in_thp(i))
             v[i] /= HPAGE_PMD_NR;
     }
     v += NR_VM_NODE_STAT_ITEMS;
 
     global_dirty_limits(v + NR_DIRTY_BG_THRESHOLD,
                 v + NR_DIRTY_THRESHOLD);
     v += NR_VM_WRITEBACK_STAT_ITEMS;
 
 #ifdef CONFIG_VM_EVENT_COUNTERS
     all_vm_events(v);
     v[PGPGIN] /= 2;     /* sectors -> kbytes */
     v[PGPGOUT] /= 2;
 #endif
     return (unsigned long *)m->private + *pos;
 }
 
 static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
 {
     (*pos)++;
     if (*pos >= NR_VMSTAT_ITEMS)
         return NULL;
     return (unsigned long *)m->private + *pos;
 }
 
 static int vmstat_show(struct seq_file *m, void *arg)
 {
     unsigned long *l = arg;
     unsigned long off = l - (unsigned long *)m->private;
 
     seq_puts(m, vmstat_text[off]);
     seq_put_decimal_ull(m, " ", *l);
     seq_putc(m, '\n');
 
     if (off == NR_VMSTAT_ITEMS - 1) {
         /*
          * We've come to the end - add any deprecated counters to avoid
          * breaking userspace which might depend on them being present.
          */
         seq_puts(m, "nr_unstable 0\n");
     }
     return 0;
 }
 
 static void vmstat_stop(struct seq_file *m, void *arg)
 {
     kfree(m->private);
     m->private = NULL;
 }
 
 static const struct seq_operations vmstat_op = {
     .start  = vmstat_start,
     .next   = vmstat_next,
     .stop   = vmstat_stop,
     .show   = vmstat_show,
 };
 #endif /* CONFIG_PROC_FS */
 
 #ifdef CONFIG_SMP
 static DEFINE_PER_CPU(struct delayed_work, vmstat_work);
 int sysctl_stat_interval __read_mostly = HZ;
 
 #ifdef CONFIG_PROC_FS
 static void refresh_vm_stats(struct work_struct *work)
 {
     refresh_cpu_vm_stats(true);
 }
 
 int vmstat_refresh(struct ctl_table *table, int write,
            void *buffer, size_t *lenp, loff_t *ppos)
 {
     long val;
     int err;
     int i;
 
     /*
      * The regular update, every sysctl_stat_interval, may come later
      * than expected: leaving a significant amount in per_cpu buckets.
      * This is particularly misleading when checking a quantity of HUGE
      * pages, immediately after running a test.  /proc/sys/vm/stat_refresh,
      * which can equally be echo'ed to or cat'ted from (by root),
      * can be used to update the stats just before reading them.
      *
      * Oh, and since global_zone_page_state() etc. are so careful to hide
      * transiently negative values, report an error here if any of
      * the stats is negative, so we know to go looking for imbalance.
      */
     err = schedule_on_each_cpu(refresh_vm_stats);
     if (err)
         return err;
     for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
         /*
          * Skip checking stats known to go negative occasionally.
          */
         switch (i) {
         case NR_ZONE_WRITE_PENDING:
         case NR_FREE_CMA_PAGES:
             continue;
         }
         val = atomic_long_read(&vm_zone_stat[i]);
         if (val < 0) {
             pr_warn("%s: %s %ld\n",
                 __func__, zone_stat_name(i), val);
         }
     }
     for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
         /*
          * Skip checking stats known to go negative occasionally.
          */
         switch (i) {
         case NR_WRITEBACK:
             continue;
         }
         val = atomic_long_read(&vm_node_stat[i]);
         if (val < 0) {
             pr_warn("%s: %s %ld\n",
                 __func__, node_stat_name(i), val);
         }
     }
     if (write)
         *ppos += *lenp;
     else
         *lenp = 0;
     return 0;
 }
 #endif /* CONFIG_PROC_FS */
 
 static void vmstat_update(struct work_struct *w)
 {
     if (refresh_cpu_vm_stats(true)) {
         /*
          * Counters were updated so we expect more updates
          * to occur in the future. Keep on running the
          * update worker thread.
          */
         queue_delayed_work_on(smp_processor_id(), mm_percpu_wq,
                 this_cpu_ptr(&vmstat_work),
                 round_jiffies_relative(sysctl_stat_interval));
     }
 }
 
 /*
  * Check if the diffs for a certain cpu indicate that
  * an update is needed.
  */
 static bool need_update(int cpu)
 {
     pg_data_t *last_pgdat = NULL;
     struct zone *zone;
 
     for_each_populated_zone(zone) {
         struct per_cpu_zonestat *pzstats = per_cpu_ptr(zone->per_cpu_zonestats, cpu);
         struct per_cpu_nodestat *n;
 
         /*
          * The fast way of checking if there are any vmstat diffs.
          */
         if (memchr_inv(pzstats->vm_stat_diff, 0, sizeof(pzstats->vm_stat_diff)))
             return true;
 
         if (last_pgdat == zone->zone_pgdat)
             continue;
         last_pgdat = zone->zone_pgdat;
         n = per_cpu_ptr(zone->zone_pgdat->per_cpu_nodestats, cpu);
         if (memchr_inv(n->vm_node_stat_diff, 0, sizeof(n->vm_node_stat_diff)))
             return true;
     }
     return false;
 }
 
 /*
  * Switch off vmstat processing and then fold all the remaining differentials
  * until the diffs stay at zero. The function is used by NOHZ and can only be
  * invoked when tick processing is not active.
  */
 void quiet_vmstat(void)
 {
     if (system_state != SYSTEM_RUNNING)
         return;
 
     if (!delayed_work_pending(this_cpu_ptr(&vmstat_work)))
         return;
 
     if (!need_update(smp_processor_id()))
         return;
 
     /*
      * Just refresh counters and do not care about the pending delayed
      * vmstat_update. It doesn't fire that often to matter and canceling
      * it would be too expensive from this path.
      * vmstat_shepherd will take care about that for us.
      */
     refresh_cpu_vm_stats(false);
 }
 
 /*
  * Shepherd worker thread that checks the
  * differentials of processors that have their worker
  * threads for vm statistics updates disabled because of
  * inactivity.
  */
 static void vmstat_shepherd(struct work_struct *w);
 
 static DECLARE_DEFERRABLE_WORK(shepherd, vmstat_shepherd);
 
 static void vmstat_shepherd(struct work_struct *w)
 {
     int cpu;
 
     cpus_read_lock();
     /* Check processors whose vmstat worker threads have been disabled */
     for_each_online_cpu(cpu) {
         struct delayed_work *dw = &per_cpu(vmstat_work, cpu);
 
         if (!delayed_work_pending(dw) && need_update(cpu))
             queue_delayed_work_on(cpu, mm_percpu_wq, dw, 0);
 
         cond_resched();
     }
     cpus_read_unlock();
 
     schedule_delayed_work(&shepherd,
         round_jiffies_relative(sysctl_stat_interval));
 }
 
 static void __init start_shepherd_timer(void)
 {
     int cpu;
 
     for_each_possible_cpu(cpu)
         INIT_DEFERRABLE_WORK(per_cpu_ptr(&vmstat_work, cpu),
             vmstat_update);
 
     schedule_delayed_work(&shepherd,
         round_jiffies_relative(sysctl_stat_interval));
 }
 
 static void __init init_cpu_node_state(void)
 {
     int node;
 
     for_each_online_node(node) {
         if (!cpumask_empty(cpumask_of_node(node)))
             node_set_state(node, N_CPU);
     }
 }
 
 static int vmstat_cpu_online(unsigned int cpu)
 {
     refresh_zone_stat_thresholds();
 
     if (!node_state(cpu_to_node(cpu), N_CPU)) {
         node_set_state(cpu_to_node(cpu), N_CPU);
         set_migration_target_nodes();
     }
 
     return 0;
 }
 
 static int vmstat_cpu_down_prep(unsigned int cpu)
 {
     cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
     return 0;
 }
 
 static int vmstat_cpu_dead(unsigned int cpu)
 {
     const struct cpumask *node_cpus;
     int node;
 
     node = cpu_to_node(cpu);
 
     refresh_zone_stat_thresholds();
     node_cpus = cpumask_of_node(node);
     if (!cpumask_empty(node_cpus))
         return 0;
 
     node_clear_state(node, N_CPU);
     set_migration_target_nodes();
 
     return 0;
 }
 
 #endif
 
 struct workqueue_struct *mm_percpu_wq;
 
 void __init init_mm_internals(void)
 {
     int ret __maybe_unused;
 
     mm_percpu_wq = alloc_workqueue("mm_percpu_wq", WQ_MEM_RECLAIM, 0);
 
 #ifdef CONFIG_SMP
     ret = cpuhp_setup_state_nocalls(CPUHP_MM_VMSTAT_DEAD, "mm/vmstat:dead",
                     NULL, vmstat_cpu_dead);
     if (ret < 0)
         pr_err("vmstat: failed to register 'dead' hotplug state\n");
 
     ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "mm/vmstat:online",
                     vmstat_cpu_online,
                     vmstat_cpu_down_prep);
     if (ret < 0)
         pr_err("vmstat: failed to register 'online' hotplug state\n");
 
     cpus_read_lock();
     init_cpu_node_state();
     cpus_read_unlock();
 
     start_shepherd_timer();
 #endif
     migrate_on_reclaim_init();
 #ifdef CONFIG_PROC_FS
     proc_create_seq("buddyinfo", 0444, NULL, &fragmentation_op);
     proc_create_seq("pagetypeinfo", 0400, NULL, &pagetypeinfo_op);
     proc_create_seq("vmstat", 0444, NULL, &vmstat_op);
     proc_create_seq("zoneinfo", 0444, NULL, &zoneinfo_op);
 #endif
 }
 
 #if defined(CONFIG_DEBUG_FS) && defined(CONFIG_COMPACTION)
 
 /*
  * Return an index indicating how much of the available free memory is
  * unusable for an allocation of the requested size.
  */
 static int unusable_free_index(unsigned int order,
                 struct contig_page_info *info)
 {
     /* No free memory is interpreted as all free memory is unusable */
     if (info->free_pages == 0)
         return 1000;
 
     /*
      * Index should be a value between 0 and 1. Return a value to 3
      * decimal places.
      *
      * 0 => no fragmentation
      * 1 => high fragmentation
      */
     return div_u64((info->free_pages - (info->free_blocks_suitable << order)) * 1000ULL, info->free_pages);
 
 }
 
 static void unusable_show_print(struct seq_file *m,
                     pg_data_t *pgdat, struct zone *zone)
 {
     unsigned int order;
     int index;
     struct contig_page_info info;
 
     seq_printf(m, "Node %d, zone %8s ",
                 pgdat->node_id,
                 zone->name);
     for (order = 0; order < MAX_ORDER; ++order) {
         fill_contig_page_info(zone, order, &info);
         index = unusable_free_index(order, &info);
         seq_printf(m, "%d.%03d ", index / 1000, index % 1000);
     }
 
     seq_putc(m, '\n');
 }
 
 /*
  * Display unusable free space index
  *
  * The unusable free space index measures how much of the available free
  * memory cannot be used to satisfy an allocation of a given size and is a
  * value between 0 and 1. The higher the value, the more of free memory is
  * unusable and by implication, the worse the external fragmentation is. This
  * can be expressed as a percentage by multiplying by 100.
  */
 static int unusable_show(struct seq_file *m, void *arg)
 {
     pg_data_t *pgdat = (pg_data_t *)arg;
 
     /* check memoryless node */
     if (!node_state(pgdat->node_id, N_MEMORY))
         return 0;
 
     walk_zones_in_node(m, pgdat, true, false, unusable_show_print);
 
     return 0;
 }
 
 static const struct seq_operations unusable_sops = {
     .start  = frag_start,
     .next   = frag_next,
     .stop   = frag_stop,
     .show   = unusable_show,
 };
 
 DEFINE_SEQ_ATTRIBUTE(unusable);
 
 static void extfrag_show_print(struct seq_file *m,
                     pg_data_t *pgdat, struct zone *zone)
 {
     unsigned int order;
     int index;
 
     /* Alloc on stack as interrupts are disabled for zone walk */
     struct contig_page_info info;
 
     seq_printf(m, "Node %d, zone %8s ",
                 pgdat->node_id,
                 zone->name);
     for (order = 0; order < MAX_ORDER; ++order) {
         fill_contig_page_info(zone, order, &info);
         index = __fragmentation_index(order, &info);
         seq_printf(m, "%2d.%03d ", index / 1000, index % 1000);
     }
 
     seq_putc(m, '\n');
 }
 
 /*
  * Display fragmentation index for orders that allocations would fail for
  */
 static int extfrag_show(struct seq_file *m, void *arg)
 {
     pg_data_t *pgdat = (pg_data_t *)arg;
 
     walk_zones_in_node(m, pgdat, true, false, extfrag_show_print);
 
     return 0;
 }
 
 static const struct seq_operations extfrag_sops = {
     .start  = frag_start,
     .next   = frag_next,
     .stop   = frag_stop,
     .show   = extfrag_show,
 };
 
 DEFINE_SEQ_ATTRIBUTE(extfrag);
 
 static int __init extfrag_debug_init(void)
 {
     struct dentry *extfrag_debug_root;
 
     extfrag_debug_root = debugfs_create_dir("extfrag", NULL);
 
     debugfs_create_file("unusable_index", 0444, extfrag_debug_root, NULL,
                 &unusable_fops);
 
     debugfs_create_file("extfrag_index", 0444, extfrag_debug_root, NULL,
                 &extfrag_fops);
 
     return 0;
 }
 
 module_init(extfrag_debug_init);
 #endif

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