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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/swap.c
  *
  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  */
 
 /*
  * This file contains the default values for the operation of the
  * Linux VM subsystem. Fine-tuning documentation can be found in
  * Documentation/admin-guide/sysctl/vm.rst.
  * Started 18.12.91
  * Swap aging added 23.2.95, Stephen Tweedie.
  * Buffermem limits added 12.3.98, Rik van Riel.
  */
 
 #include <linux/mm.h>
 #include <linux/sched.h>
 #include <linux/kernel_stat.h>
 #include <linux/swap.h>
 #include <linux/mman.h>
 #include <linux/pagemap.h>
 #include <linux/pagevec.h>
 #include <linux/init.h>
 #include <linux/export.h>
 #include <linux/mm_inline.h>
 #include <linux/percpu_counter.h>
 #include <linux/memremap.h>
 #include <linux/percpu.h>
 #include <linux/cpu.h>
 #include <linux/notifier.h>
 #include <linux/backing-dev.h>
 #include <linux/memcontrol.h>
 #include <linux/gfp.h>
 #include <linux/uio.h>
 #include <linux/hugetlb.h>
 #include <linux/page_idle.h>
 #include <linux/local_lock.h>
 #include <linux/buffer_head.h>
 
 #include "internal.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/pagemap.h>
 
 /* How many pages do we try to swap or page in/out together? */
 int page_cluster;
 
 /* Protecting only lru_rotate.fbatch which requires disabling interrupts */
 struct lru_rotate {
     local_lock_t lock;
     struct folio_batch fbatch;
 };
 static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = {
     .lock = INIT_LOCAL_LOCK(lock),
 };
 
 /*
  * The following folio batches are grouped together because they are protected
  * by disabling preemption (and interrupts remain enabled).
  */
 struct cpu_fbatches {
     local_lock_t lock;
     struct folio_batch lru_add;
     struct folio_batch lru_deactivate_file;
     struct folio_batch lru_deactivate;
     struct folio_batch lru_lazyfree;
 #ifdef CONFIG_SMP
     struct folio_batch activate;
 #endif
 };
 static DEFINE_PER_CPU(struct cpu_fbatches, cpu_fbatches) = {
     .lock = INIT_LOCAL_LOCK(lock),
 };
 
 /*
  * This path almost never happens for VM activity - pages are normally freed
  * via pagevecs.  But it gets used by networking - and for compound pages.
  */
 static void __page_cache_release(struct folio *folio)
 {
     if (folio_test_lru(folio)) {
         struct lruvec *lruvec;
         unsigned long flags;
 
         lruvec = folio_lruvec_lock_irqsave(folio, &flags);
         lruvec_del_folio(lruvec, folio);
         __folio_clear_lru_flags(folio);
         unlock_page_lruvec_irqrestore(lruvec, flags);
     }
     /* See comment on folio_test_mlocked in release_pages() */
     if (unlikely(folio_test_mlocked(folio))) {
         long nr_pages = folio_nr_pages(folio);
 
         __folio_clear_mlocked(folio);
         zone_stat_mod_folio(folio, NR_MLOCK, -nr_pages);
         count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
     }
 }
 
 static void __folio_put_small(struct folio *folio)
 {
     __page_cache_release(folio);
     mem_cgroup_uncharge(folio);
     free_unref_page(&folio->page, 0);
 }
 
 static void __folio_put_large(struct folio *folio)
 {
     /*
      * __page_cache_release() is supposed to be called for thp, not for
      * hugetlb. This is because hugetlb page does never have PageLRU set
      * (it's never listed to any LRU lists) and no memcg routines should
      * be called for hugetlb (it has a separate hugetlb_cgroup.)
      */
     if (!folio_test_hugetlb(folio))
         __page_cache_release(folio);
     destroy_large_folio(folio);
 }
 
 void __folio_put(struct folio *folio)
 {
     if (unlikely(folio_is_zone_device(folio)))
         free_zone_device_page(&folio->page);
     else if (unlikely(folio_test_large(folio)))
         __folio_put_large(folio);
     else
         __folio_put_small(folio);
 }
 EXPORT_SYMBOL(__folio_put);
 
 /**
  * put_pages_list() - release a list of pages
  * @pages: list of pages threaded on page->lru
  *
  * Release a list of pages which are strung together on page.lru.
  */
 void put_pages_list(struct list_head *pages)
 {
     struct folio *folio, *next;
 
     list_for_each_entry_safe(folio, next, pages, lru) {
         if (!folio_put_testzero(folio)) {
             list_del(&folio->lru);
             continue;
         }
         if (folio_test_large(folio)) {
             list_del(&folio->lru);
             __folio_put_large(folio);
             continue;
         }
         /* LRU flag must be clear because it's passed using the lru */
     }
 
     free_unref_page_list(pages);
     INIT_LIST_HEAD(pages);
 }
 EXPORT_SYMBOL(put_pages_list);
 
 /*
  * get_kernel_pages() - pin kernel pages in memory
  * @kiov:   An array of struct kvec structures
  * @nr_segs:    number of segments to pin
  * @write:  pinning for read/write, currently ignored
  * @pages:  array that receives pointers to the pages pinned.
  *      Should be at least nr_segs long.
  *
  * Returns number of pages pinned. This may be fewer than the number requested.
  * If nr_segs is 0 or negative, returns 0.  If no pages were pinned, returns 0.
  * Each page returned must be released with a put_page() call when it is
  * finished with.
  */
 int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write,
         struct page **pages)
 {
     int seg;
 
     for (seg = 0; seg < nr_segs; seg++) {
         if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE))
             return seg;
 
         pages[seg] = kmap_to_page(kiov[seg].iov_base);
         get_page(pages[seg]);
     }
 
     return seg;
 }
 EXPORT_SYMBOL_GPL(get_kernel_pages);
 
 typedef void (*move_fn_t)(struct lruvec *lruvec, struct folio *folio);
 
 static void lru_add_fn(struct lruvec *lruvec, struct folio *folio)
 {
     int was_unevictable = folio_test_clear_unevictable(folio);
     long nr_pages = folio_nr_pages(folio);
 
     VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
 
     /*
      * Is an smp_mb__after_atomic() still required here, before
      * folio_evictable() tests the mlocked flag, to rule out the possibility
      * of stranding an evictable folio on an unevictable LRU?  I think
      * not, because __munlock_page() only clears the mlocked flag
      * while the LRU lock is held.
      *
      * (That is not true of __page_cache_release(), and not necessarily
      * true of release_pages(): but those only clear the mlocked flag after
      * folio_put_testzero() has excluded any other users of the folio.)
      */
     if (folio_evictable(folio)) {
         if (was_unevictable)
             __count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
     } else {
         folio_clear_active(folio);
         folio_set_unevictable(folio);
         /*
          * folio->mlock_count = !!folio_test_mlocked(folio)?
          * But that leaves __mlock_page() in doubt whether another
          * actor has already counted the mlock or not.  Err on the
          * safe side, underestimate, let page reclaim fix it, rather
          * than leaving a page on the unevictable LRU indefinitely.
          */
         folio->mlock_count = 0;
         if (!was_unevictable)
             __count_vm_events(UNEVICTABLE_PGCULLED, nr_pages);
     }
 
     lruvec_add_folio(lruvec, folio);
     trace_mm_lru_insertion(folio);
 }
 
 static void folio_batch_move_lru(struct folio_batch *fbatch, move_fn_t move_fn)
 {
     int i;
     struct lruvec *lruvec = NULL;
     unsigned long flags = 0;
 
     for (i = 0; i < folio_batch_count(fbatch); i++) {
         struct folio *folio = fbatch->folios[i];
 
         /* block memcg migration while the folio moves between lru */
         if (move_fn != lru_add_fn && !folio_test_clear_lru(folio))
             continue;
 
         lruvec = folio_lruvec_relock_irqsave(folio, lruvec, &flags);
         move_fn(lruvec, folio);
 
         folio_set_lru(folio);
     }
 
     if (lruvec)
         unlock_page_lruvec_irqrestore(lruvec, flags);
     folios_put(fbatch->folios, folio_batch_count(fbatch));
     folio_batch_init(fbatch);
 }
 
 static void folio_batch_add_and_move(struct folio_batch *fbatch,
         struct folio *folio, move_fn_t move_fn)
 {
     if (folio_batch_add(fbatch, folio) && !folio_test_large(folio) &&
         !lru_cache_disabled())
         return;
     folio_batch_move_lru(fbatch, move_fn);
 }
 
 static void lru_move_tail_fn(struct lruvec *lruvec, struct folio *folio)
 {
     if (!folio_test_unevictable(folio)) {
         lruvec_del_folio(lruvec, folio);
         folio_clear_active(folio);
         lruvec_add_folio_tail(lruvec, folio);
         __count_vm_events(PGROTATED, folio_nr_pages(folio));
     }
 }
 
 /*
  * Writeback is about to end against a folio which has been marked for
  * immediate reclaim.  If it still appears to be reclaimable, move it
  * to the tail of the inactive list.
  *
  * folio_rotate_reclaimable() must disable IRQs, to prevent nasty races.
  */
 void folio_rotate_reclaimable(struct folio *folio)
 {
     if (!folio_test_locked(folio) && !folio_test_dirty(folio) &&
         !folio_test_unevictable(folio) && folio_test_lru(folio)) {
         struct folio_batch *fbatch;
         unsigned long flags;
 
         folio_get(folio);
         local_lock_irqsave(&lru_rotate.lock, flags);
         fbatch = this_cpu_ptr(&lru_rotate.fbatch);
         folio_batch_add_and_move(fbatch, folio, lru_move_tail_fn);
         local_unlock_irqrestore(&lru_rotate.lock, flags);
     }
 }
 
 void lru_note_cost(struct lruvec *lruvec, bool file, unsigned int nr_pages)
 {
     do {
         unsigned long lrusize;
 
         /*
          * Hold lruvec->lru_lock is safe here, since
          * 1) The pinned lruvec in reclaim, or
          * 2) From a pre-LRU page during refault (which also holds the
          *    rcu lock, so would be safe even if the page was on the LRU
          *    and could move simultaneously to a new lruvec).
          */
         spin_lock_irq(&lruvec->lru_lock);
         /* Record cost event */
         if (file)
             lruvec->file_cost += nr_pages;
         else
             lruvec->anon_cost += nr_pages;
 
         /*
          * Decay previous events
          *
          * Because workloads change over time (and to avoid
          * overflow) we keep these statistics as a floating
          * average, which ends up weighing recent refaults
          * more than old ones.
          */
         lrusize = lruvec_page_state(lruvec, NR_INACTIVE_ANON) +
               lruvec_page_state(lruvec, NR_ACTIVE_ANON) +
               lruvec_page_state(lruvec, NR_INACTIVE_FILE) +
               lruvec_page_state(lruvec, NR_ACTIVE_FILE);
 
         if (lruvec->file_cost + lruvec->anon_cost > lrusize / 4) {
             lruvec->file_cost /= 2;
             lruvec->anon_cost /= 2;
         }
         spin_unlock_irq(&lruvec->lru_lock);
     } while ((lruvec = parent_lruvec(lruvec)));
 }
 
 void lru_note_cost_folio(struct folio *folio)
 {
     lru_note_cost(folio_lruvec(folio), folio_is_file_lru(folio),
             folio_nr_pages(folio));
 }
 
 static void folio_activate_fn(struct lruvec *lruvec, struct folio *folio)
 {
     if (!folio_test_active(folio) && !folio_test_unevictable(folio)) {
         long nr_pages = folio_nr_pages(folio);
 
         lruvec_del_folio(lruvec, folio);
         folio_set_active(folio);
         lruvec_add_folio(lruvec, folio);
         trace_mm_lru_activate(folio);
 
         __count_vm_events(PGACTIVATE, nr_pages);
         __count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE,
                      nr_pages);
     }
 }
 
 #ifdef CONFIG_SMP
 static void folio_activate_drain(int cpu)
 {
     struct folio_batch *fbatch = &per_cpu(cpu_fbatches.activate, cpu);
 
     if (folio_batch_count(fbatch))
         folio_batch_move_lru(fbatch, folio_activate_fn);
 }
 
 static void folio_activate(struct folio *folio)
 {
     if (folio_test_lru(folio) && !folio_test_active(folio) &&
         !folio_test_unevictable(folio)) {
         struct folio_batch *fbatch;
 
         folio_get(folio);
         local_lock(&cpu_fbatches.lock);
         fbatch = this_cpu_ptr(&cpu_fbatches.activate);
         folio_batch_add_and_move(fbatch, folio, folio_activate_fn);
         local_unlock(&cpu_fbatches.lock);
     }
 }
 
 #else
 static inline void folio_activate_drain(int cpu)
 {
 }
 
 static void folio_activate(struct folio *folio)
 {
     struct lruvec *lruvec;
 
     if (folio_test_clear_lru(folio)) {
         lruvec = folio_lruvec_lock_irq(folio);
         folio_activate_fn(lruvec, folio);
         unlock_page_lruvec_irq(lruvec);
         folio_set_lru(folio);
     }
 }
 #endif
 
 static void __lru_cache_activate_folio(struct folio *folio)
 {
     struct folio_batch *fbatch;
     int i;
 
     local_lock(&cpu_fbatches.lock);
     fbatch = this_cpu_ptr(&cpu_fbatches.lru_add);
 
     /*
      * Search backwards on the optimistic assumption that the folio being
      * activated has just been added to this batch. Note that only
      * the local batch is examined as a !LRU folio could be in the
      * process of being released, reclaimed, migrated or on a remote
      * batch that is currently being drained. Furthermore, marking
      * a remote batch's folio active potentially hits a race where
      * a folio is marked active just after it is added to the inactive
      * list causing accounting errors and BUG_ON checks to trigger.
      */
     for (i = folio_batch_count(fbatch) - 1; i >= 0; i--) {
         struct folio *batch_folio = fbatch->folios[i];
 
         if (batch_folio == folio) {
             folio_set_active(folio);
             break;
         }
     }
 
     local_unlock(&cpu_fbatches.lock);
 }
 
 /*
  * Mark a page as having seen activity.
  *
  * inactive,unreferenced    ->  inactive,referenced
  * inactive,referenced      ->  active,unreferenced
  * active,unreferenced      ->  active,referenced
  *
  * When a newly allocated page is not yet visible, so safe for non-atomic ops,
  * __SetPageReferenced(page) may be substituted for mark_page_accessed(page).
  */
 void folio_mark_accessed(struct folio *folio)
 {
     if (!folio_test_referenced(folio)) {
         folio_set_referenced(folio);
     } else if (folio_test_unevictable(folio)) {
         /*
          * Unevictable pages are on the "LRU_UNEVICTABLE" list. But,
          * this list is never rotated or maintained, so marking an
          * unevictable page accessed has no effect.
          */
     } else if (!folio_test_active(folio)) {
         /*
          * If the folio is on the LRU, queue it for activation via
          * cpu_fbatches.activate. Otherwise, assume the folio is in a
          * folio_batch, mark it active and it'll be moved to the active
          * LRU on the next drain.
          */
         if (folio_test_lru(folio))
             folio_activate(folio);
         else
             __lru_cache_activate_folio(folio);
         folio_clear_referenced(folio);
         workingset_activation(folio);
     }
     if (folio_test_idle(folio))
         folio_clear_idle(folio);
 }
 EXPORT_SYMBOL(folio_mark_accessed);
 
 /**
  * folio_add_lru - Add a folio to an LRU list.
  * @folio: The folio to be added to the LRU.
  *
  * Queue the folio for addition to the LRU. The decision on whether
  * to add the page to the [in]active [file|anon] list is deferred until the
  * folio_batch is drained. This gives a chance for the caller of folio_add_lru()
  * have the folio added to the active list using folio_mark_accessed().
  */
 void folio_add_lru(struct folio *folio)
 {
     struct folio_batch *fbatch;
 
     VM_BUG_ON_FOLIO(folio_test_active(folio) &&
             folio_test_unevictable(folio), folio);
     VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
 
     folio_get(folio);
     local_lock(&cpu_fbatches.lock);
     fbatch = this_cpu_ptr(&cpu_fbatches.lru_add);
     folio_batch_add_and_move(fbatch, folio, lru_add_fn);
     local_unlock(&cpu_fbatches.lock);
 }
 EXPORT_SYMBOL(folio_add_lru);
 
 /**
  * lru_cache_add_inactive_or_unevictable
  * @page:  the page to be added to LRU
  * @vma:   vma in which page is mapped for determining reclaimability
  *
  * Place @page on the inactive or unevictable LRU list, depending on its
  * evictability.
  */
 void lru_cache_add_inactive_or_unevictable(struct page *page,
                      struct vm_area_struct *vma)
 {
     VM_BUG_ON_PAGE(PageLRU(page), page);
 
     if (unlikely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED))
         mlock_new_page(page);
     else
         lru_cache_add(page);
 }
 
 /*
  * If the folio cannot be invalidated, it is moved to the
  * inactive list to speed up its reclaim.  It is moved to the
  * head of the list, rather than the tail, to give the flusher
  * threads some time to write it out, as this is much more
  * effective than the single-page writeout from reclaim.
  *
  * If the folio isn't mapped and dirty/writeback, the folio
  * could be reclaimed asap using the reclaim flag.
  *
  * 1. active, mapped folio -> none
  * 2. active, dirty/writeback folio -> inactive, head, reclaim
  * 3. inactive, mapped folio -> none
  * 4. inactive, dirty/writeback folio -> inactive, head, reclaim
  * 5. inactive, clean -> inactive, tail
  * 6. Others -> none
  *
  * In 4, it moves to the head of the inactive list so the folio is
  * written out by flusher threads as this is much more efficient
  * than the single-page writeout from reclaim.
  */
 static void lru_deactivate_file_fn(struct lruvec *lruvec, struct folio *folio)
 {
     bool active = folio_test_active(folio);
     long nr_pages = folio_nr_pages(folio);
 
     if (folio_test_unevictable(folio))
         return;
 
     /* Some processes are using the folio */
     if (folio_mapped(folio))
         return;
 
     lruvec_del_folio(lruvec, folio);
     folio_clear_active(folio);
     folio_clear_referenced(folio);
 
     if (folio_test_writeback(folio) || folio_test_dirty(folio)) {
         /*
          * Setting the reclaim flag could race with
          * folio_end_writeback() and confuse readahead.  But the
          * race window is _really_ small and  it's not a critical
          * problem.
          */
         lruvec_add_folio(lruvec, folio);
         folio_set_reclaim(folio);
     } else {
         /*
          * The folio's writeback ended while it was in the batch.
          * We move that folio to the tail of the inactive list.
          */
         lruvec_add_folio_tail(lruvec, folio);
         __count_vm_events(PGROTATED, nr_pages);
     }
 
     if (active) {
         __count_vm_events(PGDEACTIVATE, nr_pages);
         __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
                      nr_pages);
     }
 }
 
 static void lru_deactivate_fn(struct lruvec *lruvec, struct folio *folio)
 {
     if (folio_test_active(folio) && !folio_test_unevictable(folio)) {
         long nr_pages = folio_nr_pages(folio);
 
         lruvec_del_folio(lruvec, folio);
         folio_clear_active(folio);
         folio_clear_referenced(folio);
         lruvec_add_folio(lruvec, folio);
 
         __count_vm_events(PGDEACTIVATE, nr_pages);
         __count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
                      nr_pages);
     }
 }
 
 static void lru_lazyfree_fn(struct lruvec *lruvec, struct folio *folio)
 {
     if (folio_test_anon(folio) && folio_test_swapbacked(folio) &&
         !folio_test_swapcache(folio) && !folio_test_unevictable(folio)) {
         long nr_pages = folio_nr_pages(folio);
 
         lruvec_del_folio(lruvec, folio);
         folio_clear_active(folio);
         folio_clear_referenced(folio);
         /*
          * Lazyfree folios are clean anonymous folios.  They have
          * the swapbacked flag cleared, to distinguish them from normal
          * anonymous folios
          */
         folio_clear_swapbacked(folio);
         lruvec_add_folio(lruvec, folio);
 
         __count_vm_events(PGLAZYFREE, nr_pages);
         __count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE,
                      nr_pages);
     }
 }
 
 /*
  * Drain pages out of the cpu's folio_batch.
  * Either "cpu" is the current CPU, and preemption has already been
  * disabled; or "cpu" is being hot-unplugged, and is already dead.
  */
 void lru_add_drain_cpu(int cpu)
 {
     struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
     struct folio_batch *fbatch = &fbatches->lru_add;
 
     if (folio_batch_count(fbatch))
         folio_batch_move_lru(fbatch, lru_add_fn);
 
     fbatch = &per_cpu(lru_rotate.fbatch, cpu);
     /* Disabling interrupts below acts as a compiler barrier. */
     if (data_race(folio_batch_count(fbatch))) {
         unsigned long flags;
 
         /* No harm done if a racing interrupt already did this */
         local_lock_irqsave(&lru_rotate.lock, flags);
         folio_batch_move_lru(fbatch, lru_move_tail_fn);
         local_unlock_irqrestore(&lru_rotate.lock, flags);
     }
 
     fbatch = &fbatches->lru_deactivate_file;
     if (folio_batch_count(fbatch))
         folio_batch_move_lru(fbatch, lru_deactivate_file_fn);
 
     fbatch = &fbatches->lru_deactivate;
     if (folio_batch_count(fbatch))
         folio_batch_move_lru(fbatch, lru_deactivate_fn);
 
     fbatch = &fbatches->lru_lazyfree;
     if (folio_batch_count(fbatch))
         folio_batch_move_lru(fbatch, lru_lazyfree_fn);
 
     folio_activate_drain(cpu);
 }
 
 /**
  * deactivate_file_folio() - Deactivate a file folio.
  * @folio: Folio to deactivate.
  *
  * This function hints to the VM that @folio is a good reclaim candidate,
  * for example if its invalidation fails due to the folio being dirty
  * or under writeback.
  *
  * Context: Caller holds a reference on the folio.
  */
 void deactivate_file_folio(struct folio *folio)
 {
     struct folio_batch *fbatch;
 
     /* Deactivating an unevictable folio will not accelerate reclaim */
     if (folio_test_unevictable(folio))
         return;
 
     folio_get(folio);
     local_lock(&cpu_fbatches.lock);
     fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate_file);
     folio_batch_add_and_move(fbatch, folio, lru_deactivate_file_fn);
     local_unlock(&cpu_fbatches.lock);
 }
 
 /*
  * deactivate_page - deactivate a page
  * @page: page to deactivate
  *
  * deactivate_page() moves @page to the inactive list if @page was on the active
  * list and was not an unevictable page.  This is done to accelerate the reclaim
  * of @page.
  */
 void deactivate_page(struct page *page)
 {
     struct folio *folio = page_folio(page);
 
     if (folio_test_lru(folio) && folio_test_active(folio) &&
         !folio_test_unevictable(folio)) {
         struct folio_batch *fbatch;
 
         folio_get(folio);
         local_lock(&cpu_fbatches.lock);
         fbatch = this_cpu_ptr(&cpu_fbatches.lru_deactivate);
         folio_batch_add_and_move(fbatch, folio, lru_deactivate_fn);
         local_unlock(&cpu_fbatches.lock);
     }
 }
 
 /**
  * mark_page_lazyfree - make an anon page lazyfree
  * @page: page to deactivate
  *
  * mark_page_lazyfree() moves @page to the inactive file list.
  * This is done to accelerate the reclaim of @page.
  */
 void mark_page_lazyfree(struct page *page)
 {
     struct folio *folio = page_folio(page);
 
     if (folio_test_lru(folio) && folio_test_anon(folio) &&
         folio_test_swapbacked(folio) && !folio_test_swapcache(folio) &&
         !folio_test_unevictable(folio)) {
         struct folio_batch *fbatch;
 
         folio_get(folio);
         local_lock(&cpu_fbatches.lock);
         fbatch = this_cpu_ptr(&cpu_fbatches.lru_lazyfree);
         folio_batch_add_and_move(fbatch, folio, lru_lazyfree_fn);
         local_unlock(&cpu_fbatches.lock);
     }
 }
 
 void lru_add_drain(void)
 {
     local_lock(&cpu_fbatches.lock);
     lru_add_drain_cpu(smp_processor_id());
     local_unlock(&cpu_fbatches.lock);
     mlock_page_drain_local();
 }
 
 /*
  * It's called from per-cpu workqueue context in SMP case so
  * lru_add_drain_cpu and invalidate_bh_lrus_cpu should run on
  * the same cpu. It shouldn't be a problem in !SMP case since
  * the core is only one and the locks will disable preemption.
  */
 static void lru_add_and_bh_lrus_drain(void)
 {
     local_lock(&cpu_fbatches.lock);
     lru_add_drain_cpu(smp_processor_id());
     local_unlock(&cpu_fbatches.lock);
     invalidate_bh_lrus_cpu();
     mlock_page_drain_local();
 }
 
 void lru_add_drain_cpu_zone(struct zone *zone)
 {
     local_lock(&cpu_fbatches.lock);
     lru_add_drain_cpu(smp_processor_id());
     drain_local_pages(zone);
     local_unlock(&cpu_fbatches.lock);
     mlock_page_drain_local();
 }
 
 #ifdef CONFIG_SMP
 
 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
 
 static void lru_add_drain_per_cpu(struct work_struct *dummy)
 {
     lru_add_and_bh_lrus_drain();
 }
 
 static bool cpu_needs_drain(unsigned int cpu)
 {
     struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
 
     /* Check these in order of likelihood that they're not zero */
     return folio_batch_count(&fbatches->lru_add) ||
         data_race(folio_batch_count(&per_cpu(lru_rotate.fbatch, cpu))) ||
         folio_batch_count(&fbatches->lru_deactivate_file) ||
         folio_batch_count(&fbatches->lru_deactivate) ||
         folio_batch_count(&fbatches->lru_lazyfree) ||
         folio_batch_count(&fbatches->activate) ||
         need_mlock_page_drain(cpu) ||
         has_bh_in_lru(cpu, NULL);
 }
 
 /*
  * Doesn't need any cpu hotplug locking because we do rely on per-cpu
  * kworkers being shut down before our page_alloc_cpu_dead callback is
  * executed on the offlined cpu.
  * Calling this function with cpu hotplug locks held can actually lead
  * to obscure indirect dependencies via WQ context.
  */
 static inline void __lru_add_drain_all(bool force_all_cpus)
 {
     /*
      * lru_drain_gen - Global pages generation number
      *
      * (A) Definition: global lru_drain_gen = x implies that all generations
      *     0 < n <= x are already *scheduled* for draining.
      *
      * This is an optimization for the highly-contended use case where a
      * user space workload keeps constantly generating a flow of pages for
      * each CPU.
      */
     static unsigned int lru_drain_gen;
     static struct cpumask has_work;
     static DEFINE_MUTEX(lock);
     unsigned cpu, this_gen;
 
     /*
      * Make sure nobody triggers this path before mm_percpu_wq is fully
      * initialized.
      */
     if (WARN_ON(!mm_percpu_wq))
         return;
 
     /*
      * Guarantee folio_batch counter stores visible by this CPU
      * are visible to other CPUs before loading the current drain
      * generation.
      */
     smp_mb();
 
     /*
      * (B) Locally cache global LRU draining generation number
      *
      * The read barrier ensures that the counter is loaded before the mutex
      * is taken. It pairs with smp_mb() inside the mutex critical section
      * at (D).
      */
     this_gen = smp_load_acquire(&lru_drain_gen);
 
     mutex_lock(&lock);
 
     /*
      * (C) Exit the draining operation if a newer generation, from another
      * lru_add_drain_all(), was already scheduled for draining. Check (A).
      */
     if (unlikely(this_gen != lru_drain_gen && !force_all_cpus))
         goto done;
 
     /*
      * (D) Increment global generation number
      *
      * Pairs with smp_load_acquire() at (B), outside of the critical
      * section. Use a full memory barrier to guarantee that the
      * new global drain generation number is stored before loading
      * folio_batch counters.
      *
      * This pairing must be done here, before the for_each_online_cpu loop
      * below which drains the page vectors.
      *
      * Let x, y, and z represent some system CPU numbers, where x < y < z.
      * Assume CPU #z is in the middle of the for_each_online_cpu loop
      * below and has already reached CPU #y's per-cpu data. CPU #x comes
      * along, adds some pages to its per-cpu vectors, then calls
      * lru_add_drain_all().
      *
      * If the paired barrier is done at any later step, e.g. after the
      * loop, CPU #x will just exit at (C) and miss flushing out all of its
      * added pages.
      */
     WRITE_ONCE(lru_drain_gen, lru_drain_gen + 1);
     smp_mb();
 
     cpumask_clear(&has_work);
     for_each_online_cpu(cpu) {
         struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
 
         if (cpu_needs_drain(cpu)) {
             INIT_WORK(work, lru_add_drain_per_cpu);
             queue_work_on(cpu, mm_percpu_wq, work);
             __cpumask_set_cpu(cpu, &has_work);
         }
     }
 
     for_each_cpu(cpu, &has_work)
         flush_work(&per_cpu(lru_add_drain_work, cpu));
 
 done:
     mutex_unlock(&lock);
 }
 
 void lru_add_drain_all(void)
 {
     __lru_add_drain_all(false);
 }
 #else
 void lru_add_drain_all(void)
 {
     lru_add_drain();
 }
 #endif /* CONFIG_SMP */
 
 atomic_t lru_disable_count = ATOMIC_INIT(0);
 
 /*
  * lru_cache_disable() needs to be called before we start compiling
  * a list of pages to be migrated using isolate_lru_page().
  * It drains pages on LRU cache and then disable on all cpus until
  * lru_cache_enable is called.
  *
  * Must be paired with a call to lru_cache_enable().
  */
 void lru_cache_disable(void)
 {
     atomic_inc(&lru_disable_count);
     /*
      * Readers of lru_disable_count are protected by either disabling
      * preemption or rcu_read_lock:
      *
      * preempt_disable, local_irq_disable  [bh_lru_lock()]
      * rcu_read_lock               [rt_spin_lock CONFIG_PREEMPT_RT]
      * preempt_disable             [local_lock !CONFIG_PREEMPT_RT]
      *
      * Since v5.1 kernel, synchronize_rcu() is guaranteed to wait on
      * preempt_disable() regions of code. So any CPU which sees
      * lru_disable_count = 0 will have exited the critical
      * section when synchronize_rcu() returns.
      */
     synchronize_rcu_expedited();
 #ifdef CONFIG_SMP
     __lru_add_drain_all(true);
 #else
     lru_add_and_bh_lrus_drain();
 #endif
 }
 
 /**
  * release_pages - batched put_page()
  * @pages: array of pages to release
  * @nr: number of pages
  *
  * Decrement the reference count on all the pages in @pages.  If it
  * fell to zero, remove the page from the LRU and free it.
  */
 void release_pages(struct page **pages, int nr)
 {
     int i;
     LIST_HEAD(pages_to_free);
     struct lruvec *lruvec = NULL;
     unsigned long flags = 0;
     unsigned int lock_batch;
 
     for (i = 0; i < nr; i++) {
         struct folio *folio = page_folio(pages[i]);
 
         /*
          * Make sure the IRQ-safe lock-holding time does not get
          * excessive with a continuous string of pages from the
          * same lruvec. The lock is held only if lruvec != NULL.
          */
         if (lruvec && ++lock_batch == SWAP_CLUSTER_MAX) {
             unlock_page_lruvec_irqrestore(lruvec, flags);
             lruvec = NULL;
         }
 
         if (is_huge_zero_page(&folio->page))
             continue;
 
         if (folio_is_zone_device(folio)) {
             if (lruvec) {
                 unlock_page_lruvec_irqrestore(lruvec, flags);
                 lruvec = NULL;
             }
             if (put_devmap_managed_page(&folio->page))
                 continue;
             if (folio_put_testzero(folio))
                 free_zone_device_page(&folio->page);
             continue;
         }
 
         if (!folio_put_testzero(folio))
             continue;
 
         if (folio_test_large(folio)) {
             if (lruvec) {
                 unlock_page_lruvec_irqrestore(lruvec, flags);
                 lruvec = NULL;
             }
             __folio_put_large(folio);
             continue;
         }
 
         if (folio_test_lru(folio)) {
             struct lruvec *prev_lruvec = lruvec;
 
             lruvec = folio_lruvec_relock_irqsave(folio, lruvec,
                                     &flags);
             if (prev_lruvec != lruvec)
                 lock_batch = 0;
 
             lruvec_del_folio(lruvec, folio);
             __folio_clear_lru_flags(folio);
         }
 
         /*
          * In rare cases, when truncation or holepunching raced with
          * munlock after VM_LOCKED was cleared, Mlocked may still be
          * found set here.  This does not indicate a problem, unless
          * "unevictable_pgs_cleared" appears worryingly large.
          */
         if (unlikely(folio_test_mlocked(folio))) {
             __folio_clear_mlocked(folio);
             zone_stat_sub_folio(folio, NR_MLOCK);
             count_vm_event(UNEVICTABLE_PGCLEARED);
         }
 
         list_add(&folio->lru, &pages_to_free);
     }
     if (lruvec)
         unlock_page_lruvec_irqrestore(lruvec, flags);
 
     mem_cgroup_uncharge_list(&pages_to_free);
     free_unref_page_list(&pages_to_free);
 }
 EXPORT_SYMBOL(release_pages);
 
 /*
  * The pages which we're about to release may be in the deferred lru-addition
  * queues.  That would prevent them from really being freed right now.  That's
  * OK from a correctness point of view but is inefficient - those pages may be
  * cache-warm and we want to give them back to the page allocator ASAP.
  *
  * So __pagevec_release() will drain those queues here.
  * folio_batch_move_lru() calls folios_put() directly to avoid
  * mutual recursion.
  */
 void __pagevec_release(struct pagevec *pvec)
 {
     if (!pvec->percpu_pvec_drained) {
         lru_add_drain();
         pvec->percpu_pvec_drained = true;
     }
     release_pages(pvec->pages, pagevec_count(pvec));
     pagevec_reinit(pvec);
 }
 EXPORT_SYMBOL(__pagevec_release);
 
 /**
  * folio_batch_remove_exceptionals() - Prune non-folios from a batch.
  * @fbatch: The batch to prune
  *
  * find_get_entries() fills a batch with both folios and shadow/swap/DAX
  * entries.  This function prunes all the non-folio entries from @fbatch
  * without leaving holes, so that it can be passed on to folio-only batch
  * operations.
  */
 void folio_batch_remove_exceptionals(struct folio_batch *fbatch)
 {
     unsigned int i, j;
 
     for (i = 0, j = 0; i < folio_batch_count(fbatch); i++) {
         struct folio *folio = fbatch->folios[i];
         if (!xa_is_value(folio))
             fbatch->folios[j++] = folio;
     }
     fbatch->nr = j;
 }
 
 unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
         struct address_space *mapping, pgoff_t *index, pgoff_t end,
         xa_mark_t tag)
 {
     pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
                     PAGEVEC_SIZE, pvec->pages);
     return pagevec_count(pvec);
 }
 EXPORT_SYMBOL(pagevec_lookup_range_tag);
 
 /*
  * Perform any setup for the swap system
  */
 void __init swap_setup(void)
 {
     unsigned long megs = totalram_pages() >> (20 - PAGE_SHIFT);
 
     /* Use a smaller cluster for small-memory machines */
     if (megs < 16)
         page_cluster = 2;
     else
         page_cluster = 3;
     /*
      * Right now other parts of the system means that we
      * _really_ don't want to cluster much more
      */
 }

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