mm/swap.c - kernel/common - Git at Google

 // 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.pvec which requires disabling interrupts */
 struct lru_rotate {
 	local_lock_t lock;
 	struct pagevec pvec;
 };
 static DEFINE_PER_CPU(struct lru_rotate, lru_rotate) = {
 	.lock = INIT_LOCAL_LOCK(lock),
 };

 /*
  * The following struct pagevec are grouped together because they are protected
  * by disabling preemption (and interrupts remain enabled).
  */
 struct lru_pvecs {
 	local_lock_t lock;
 	struct pagevec lru_add;
 	struct pagevec lru_deactivate_file;
 	struct pagevec lru_deactivate;
 	struct pagevec lru_lazyfree;
 	struct pagevec lru_lazyfree_movetail;
 #ifdef CONFIG_SMP
 	struct pagevec activate_page;
 #endif
 };
 static DEFINE_PER_CPU(struct lru_pvecs, lru_pvecs) = {
 	.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.
  */
 static void __page_cache_release(struct page *page)
 {
 	if (PageLRU(page)) {
 		pg_data_t *pgdat = page_pgdat(page);
 		struct lruvec *lruvec;
 		unsigned long flags;

 		spin_lock_irqsave(&pgdat->lru_lock, flags);
 		lruvec = mem_cgroup_page_lruvec(page, pgdat);
 		del_page_from_lru_list(page, lruvec);
 		__clear_page_lru_flags(page);
 		spin_unlock_irqrestore(&pgdat->lru_lock, flags);
 	}
 	__ClearPageWaiters(page);
 }

 static void __put_single_page(struct page *page)
 {
 	__page_cache_release(page);
 	mem_cgroup_uncharge(page);
 	free_unref_page(page);
 }

 static void __put_compound_page(struct page *page)
 {
 	/*
 	 * __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 (!PageHuge(page))
 		__page_cache_release(page);
 	destroy_compound_page(page);
 }

 void __put_page(struct page *page)
 {
 	if (is_zone_device_page(page)) {
 		put_dev_pagemap(page->pgmap);

 		/*
 		 * The page belongs to the device that created pgmap. Do
 		 * not return it to page allocator.
 		 */
 		return;
 	}

 	if (unlikely(PageCompound(page)))
 		__put_compound_page(page);
 	else
 		__put_single_page(page);
 }
 EXPORT_SYMBOL(__put_page);

 /**
  * 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.  Currently
  * used by read_cache_pages() and related error recovery code.
  */
 void put_pages_list(struct list_head *pages)
 {
 	while (!list_empty(pages)) {
 		struct page *victim;

 		victim = lru_to_page(pages);
 		list_del(&victim->lru);
 		put_page(victim);
 	}
 }
 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_pages is 0 or negative, returns 0. If no pages
  * were pinned, returns -errno. 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);

 /*
  * get_kernel_page() - pin a kernel page in memory
  * @start:	starting kernel address
  * @write:	pinning for read/write, currently ignored
  * @pages:	array that receives pointer to the page pinned.
  *		Must be at least nr_segs long.
  *
  * Returns 1 if page is pinned. If the page was not pinned, returns
  * -errno. The page returned must be released with a put_page() call
  * when it is finished with.
  */
 int get_kernel_page(unsigned long start, int write, struct page **pages)
 {
 	const struct kvec kiov = {
 		.iov_base = (void *)start,
 		.iov_len = PAGE_SIZE
 	};

 	return get_kernel_pages(&kiov, 1, write, pages);
 }
 EXPORT_SYMBOL_GPL(get_kernel_page);

 static void pagevec_lru_move_fn(struct pagevec *pvec,
 	void (*move_fn)(struct page *page, struct lruvec *lruvec, void *arg),
 	void *arg)
 {
 	int i;
 	struct pglist_data *pgdat = NULL;
 	struct lruvec *lruvec;
 	unsigned long flags = 0;

 	for (i = 0; i < pagevec_count(pvec); i++) {
 		struct page *page = pvec->pages[i];
 		struct pglist_data *pagepgdat = page_pgdat(page);

 		if (pagepgdat != pgdat) {
 			if (pgdat)
 				spin_unlock_irqrestore(&pgdat->lru_lock, flags);
 			pgdat = pagepgdat;
 			spin_lock_irqsave(&pgdat->lru_lock, flags);
 		}

 		lruvec = mem_cgroup_page_lruvec(page, pgdat);
 		(*move_fn)(page, lruvec, arg);
 	}
 	if (pgdat)
 		spin_unlock_irqrestore(&pgdat->lru_lock, flags);
 	release_pages(pvec->pages, pvec->nr);
 	pagevec_reinit(pvec);
 }

 static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec,
 				 void *arg)
 {
 	int *pgmoved = arg;

 	if (PageLRU(page) && !PageUnevictable(page)) {
 		del_page_from_lru_list(page, lruvec);
 		ClearPageActive(page);
 		add_page_to_lru_list_tail(page, lruvec);
 		(*pgmoved) += thp_nr_pages(page);
 	}
 }

 /*
  * pagevec_move_tail() must be called with IRQ disabled.
  * Otherwise this may cause nasty races.
  */
 static void pagevec_move_tail(struct pagevec *pvec)
 {
 	int pgmoved = 0;

 	pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, &pgmoved);
 	__count_vm_events(PGROTATED, pgmoved);
 }

 /* return true if pagevec needs to drain */
 static bool pagevec_add_and_need_flush(struct pagevec *pvec, struct page *page)
 {
 	bool ret = false;

 	if (!pagevec_add(pvec, page) || PageCompound(page) ||
 			lru_cache_disabled())
 		ret = true;

 	return ret;
 }

 /*
  * Writeback is about to end against a page which has been marked for immediate
  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
  * inactive list.
  */
 void rotate_reclaimable_page(struct page *page)
 {
 	if (!PageLocked(page) && !PageDirty(page) &&
 	    !PageUnevictable(page) && PageLRU(page)) {
 		struct pagevec *pvec;
 		unsigned long flags;

 		get_page(page);
 		local_lock_irqsave(&lru_rotate.lock, flags);
 		pvec = this_cpu_ptr(&lru_rotate.pvec);
 		if (pagevec_add_and_need_flush(pvec, page))
 			pagevec_move_tail(pvec);
 		local_unlock_irqrestore(&lru_rotate.lock, flags);
 	}
 }

 void lru_note_cost(struct lruvec *lruvec, bool file, unsigned int nr_pages)
 {
 	do {
 		unsigned long lrusize;

 		/* 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;
 		}
 	} while ((lruvec = parent_lruvec(lruvec)));
 }

 void lru_note_cost_page(struct page *page)
 {
 	lru_note_cost(mem_cgroup_page_lruvec(page, page_pgdat(page)),
 		      page_is_file_lru(page), thp_nr_pages(page));
 }

 static void __activate_page(struct page *page, struct lruvec *lruvec,
 			    void *arg)
 {
 	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 		int nr_pages = thp_nr_pages(page);

 		del_page_from_lru_list(page, lruvec);
 		SetPageActive(page);
 		add_page_to_lru_list(page, lruvec);
 		trace_mm_lru_activate(page);

 		__count_vm_events(PGACTIVATE, nr_pages);
 		__count_memcg_events(lruvec_memcg(lruvec), PGACTIVATE,
 				     nr_pages);
 	}
 }

 #ifdef CONFIG_SMP
 static void activate_page_drain(int cpu)
 {
 	struct pagevec *pvec = &per_cpu(lru_pvecs.activate_page, cpu);

 	if (pagevec_count(pvec))
 		pagevec_lru_move_fn(pvec, __activate_page, NULL);
 }

 static bool need_activate_page_drain(int cpu)
 {
 	return pagevec_count(&per_cpu(lru_pvecs.activate_page, cpu)) != 0;
 }

 void activate_page(struct page *page)
 {
 	page = compound_head(page);
 	if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
 		struct pagevec *pvec;

 		local_lock(&lru_pvecs.lock);
 		pvec = this_cpu_ptr(&lru_pvecs.activate_page);
 		get_page(page);
 		if (pagevec_add_and_need_flush(pvec, page))
 			pagevec_lru_move_fn(pvec, __activate_page, NULL);
 		local_unlock(&lru_pvecs.lock);
 	}
 }

 #else
 static inline void activate_page_drain(int cpu)
 {
 }

 void activate_page(struct page *page)
 {
 	pg_data_t *pgdat = page_pgdat(page);

 	page = compound_head(page);
 	spin_lock_irq(&pgdat->lru_lock);
 	__activate_page(page, mem_cgroup_page_lruvec(page, pgdat), NULL);
 	spin_unlock_irq(&pgdat->lru_lock);
 }
 #endif

 static void __lru_cache_activate_page(struct page *page)
 {
 	struct pagevec *pvec;
 	int i;

 	local_lock(&lru_pvecs.lock);
 	pvec = this_cpu_ptr(&lru_pvecs.lru_add);

 	/*
 	 * Search backwards on the optimistic assumption that the page being
 	 * activated has just been added to this pagevec. Note that only
 	 * the local pagevec is examined as a !PageLRU page could be in the
 	 * process of being released, reclaimed, migrated or on a remote
 	 * pagevec that is currently being drained. Furthermore, marking
 	 * a remote pagevec's page PageActive potentially hits a race where
 	 * a page is marked PageActive just after it is added to the inactive
 	 * list causing accounting errors and BUG_ON checks to trigger.
 	 */
 	for (i = pagevec_count(pvec) - 1; i >= 0; i--) {
 		struct page *pagevec_page = pvec->pages[i];

 		if (pagevec_page == page) {
 			SetPageActive(page);
 			break;
 		}
 	}

 	local_unlock(&lru_pvecs.lock);
 }

 #ifdef CONFIG_LRU_GEN
 static void page_inc_refs(struct page *page)
 {
 	unsigned long refs;
 	unsigned long old_flags, new_flags;

 	if (PageUnevictable(page))
 		return;

 	/* see the comment on MAX_NR_TIERS */
 	do {
 		new_flags = old_flags = READ_ONCE(page->flags);

 		if (!(new_flags & BIT(PG_referenced))) {
 			new_flags |= BIT(PG_referenced);
 			continue;
 		}

 		if (!(new_flags & BIT(PG_workingset))) {
 			new_flags |= BIT(PG_workingset);
 			continue;
 		}

 		refs = new_flags & LRU_REFS_MASK;
 		refs = min(refs + BIT(LRU_REFS_PGOFF), LRU_REFS_MASK);

 		new_flags &= ~LRU_REFS_MASK;
 		new_flags |= refs;
 	} while (new_flags != old_flags &&
 		 cmpxchg(&page->flags, old_flags, new_flags) != old_flags);
 }
 #else
 static void page_inc_refs(struct page *page)
 {
 }
 #endif /* CONFIG_LRU_GEN */

 /*
  * 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 mark_page_accessed(struct page *page)
 {
 	page = compound_head(page);

 	if (lru_gen_enabled()) {
 		page_inc_refs(page);
 		return;
 	}

 	if (!PageReferenced(page)) {
 		SetPageReferenced(page);
 	} else if (PageUnevictable(page)) {
 		/*
 		 * Unevictable pages are on the "LRU_UNEVICTABLE" list. But,
 		 * this list is never rotated or maintained, so marking an
 		 * evictable page accessed has no effect.
 		 */
 	} else if (!PageActive(page)) {
 		/*
 		 * If the page is on the LRU, queue it for activation via
 		 * lru_pvecs.activate_page. Otherwise, assume the page is on a
 		 * pagevec, mark it active and it'll be moved to the active
 		 * LRU on the next drain.
 		 */
 		if (PageLRU(page))
 			activate_page(page);
 		else
 			__lru_cache_activate_page(page);
 		ClearPageReferenced(page);
 		workingset_activation(page);
 	}
 	if (page_is_idle(page))
 		clear_page_idle(page);
 }
 EXPORT_SYMBOL(mark_page_accessed);

 /**
  * lru_cache_add - add a page to a page list
  * @page: the page to be added to the LRU.
  *
  * Queue the page for addition to the LRU via pagevec. The decision on whether
  * to add the page to the [in]active [file|anon] list is deferred until the
  * pagevec is drained. This gives a chance for the caller of lru_cache_add()
  * have the page added to the active list using mark_page_accessed().
  */
 void lru_cache_add(struct page *page)
 {
 	struct pagevec *pvec;

 	VM_BUG_ON_PAGE(PageActive(page) && PageUnevictable(page), page);
 	VM_BUG_ON_PAGE(PageLRU(page), page);

 	/* see the comment in lru_gen_add_page() */
 	if (lru_gen_enabled() && !PageUnevictable(page) &&
 	    lru_gen_in_fault() && !(current->flags & PF_MEMALLOC))
 		SetPageActive(page);

 	get_page(page);
 	local_lock(&lru_pvecs.lock);
 	pvec = this_cpu_ptr(&lru_pvecs.lru_add);
 	if (pagevec_add_and_need_flush(pvec, page))
 		__pagevec_lru_add(pvec);
 	local_unlock(&lru_pvecs.lock);
 }
 EXPORT_SYMBOL(lru_cache_add);

 /**
  * 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,
 					 unsigned long vma_flags)
 {
 	bool unevictable;

 	VM_BUG_ON_PAGE(PageLRU(page), page);

 	unevictable = (vma_flags & (VM_LOCKED | VM_SPECIAL)) == VM_LOCKED;
 	if (unlikely(unevictable) && !TestSetPageMlocked(page)) {
 		int nr_pages = thp_nr_pages(page);
 		/*
 		 * We use the irq-unsafe __mod_zone_page_stat because this
 		 * counter is not modified from interrupt context, and the pte
 		 * lock is held(spinlock), which implies preemption disabled.
 		 */
 		__mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
 		count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
 	}
 	lru_cache_add(page);
 }

 /*
  * If the page can not 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 page isn't page_mapped and dirty/writeback, the page
  * could reclaim asap using PG_reclaim.
  *
  * 1. active, mapped page -> none
  * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
  * 3. inactive, mapped page -> none
  * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
  * 5. inactive, clean -> inactive, tail
  * 6. Others -> none
  *
  * In 4, why it moves inactive's head, the VM expects the page would
  * be write it out by flusher threads as this is much more effective
  * than the single-page writeout from reclaim.
  */
 static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec,
 			      void *arg)
 {
 	bool active = PageActive(page);
 	int nr_pages = thp_nr_pages(page);

 	if (!PageLRU(page))
 		return;

 	if (PageUnevictable(page))
 		return;

 	/* Some processes are using the page */
 	if (page_mapped(page))
 		return;

 	del_page_from_lru_list(page, lruvec);
 	ClearPageActive(page);
 	ClearPageReferenced(page);

 	if (PageWriteback(page) || PageDirty(page)) {
 		/*
 		 * PG_reclaim could be raced with end_page_writeback
 		 * It can make readahead confusing.  But race window
 		 * is _really_ small and  it's non-critical problem.
 		 */
 		add_page_to_lru_list(page, lruvec);
 		SetPageReclaim(page);
 	} else {
 		/*
 		 * The page's writeback ends up during pagevec
 		 * We moves tha page into tail of inactive.
 		 */
 		add_page_to_lru_list_tail(page, lruvec);
 		__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 page *page, struct lruvec *lruvec,
 			    void *arg)
 {
 	if (PageLRU(page) && !PageUnevictable(page) && (PageActive(page) || lru_gen_enabled())) {
 		int nr_pages = thp_nr_pages(page);

 		del_page_from_lru_list(page, lruvec);
 		ClearPageActive(page);
 		ClearPageReferenced(page);
 		add_page_to_lru_list(page, lruvec);

 		__count_vm_events(PGDEACTIVATE, nr_pages);
 		__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE,
 				     nr_pages);
 	}
 }

 static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
 			    void *arg)
 {
 	if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
 	    !PageSwapCache(page) && !PageUnevictable(page)) {
 		int nr_pages = thp_nr_pages(page);

 		del_page_from_lru_list(page, lruvec);
 		ClearPageActive(page);
 		ClearPageReferenced(page);
 		/*
 		 * Lazyfree pages are clean anonymous pages.  They have
 		 * PG_swapbacked flag cleared, to distinguish them from normal
 		 * anonymous pages
 		 */
 		ClearPageSwapBacked(page);
 		add_page_to_lru_list(page, lruvec);

 		__count_vm_events(PGLAZYFREE, nr_pages);
 		__count_memcg_events(lruvec_memcg(lruvec), PGLAZYFREE,
 				     nr_pages);
 	}
 }

 static void lru_lazyfree_movetail_fn(struct page *page, struct lruvec *lruvec,
 			    void *arg)
 {
 	bool *add_to_tail = (bool *)arg;

 	if (PageLRU(page) && !PageUnevictable(page) && PageSwapBacked(page) &&
 		!PageSwapCache(page)) {
 		del_page_from_lru_list(page, lruvec);
 		ClearPageActive(page);
 		ClearPageReferenced(page);
 		if (add_to_tail && *add_to_tail)
 			add_page_to_lru_list_tail(page, lruvec);
 		else
 			add_page_to_lru_list(page, lruvec);
 	}
 }

 /*
  * Drain pages out of the cpu's pagevecs.
  * 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 pagevec *pvec = &per_cpu(lru_pvecs.lru_add, cpu);

 	if (pagevec_count(pvec))
 		__pagevec_lru_add(pvec);

 	pvec = &per_cpu(lru_rotate.pvec, cpu);
 	/* Disabling interrupts below acts as a compiler barrier. */
 	if (data_race(pagevec_count(pvec))) {
 		unsigned long flags;

 		/* No harm done if a racing interrupt already did this */
 		local_lock_irqsave(&lru_rotate.lock, flags);
 		pagevec_move_tail(pvec);
 		local_unlock_irqrestore(&lru_rotate.lock, flags);
 	}

 	pvec = &per_cpu(lru_pvecs.lru_deactivate_file, cpu);
 	if (pagevec_count(pvec))
 		pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);

 	pvec = &per_cpu(lru_pvecs.lru_deactivate, cpu);
 	if (pagevec_count(pvec))
 		pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);

 	pvec = &per_cpu(lru_pvecs.lru_lazyfree, cpu);
 	if (pagevec_count(pvec))
 		pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);

 	pvec = &per_cpu(lru_pvecs.lru_lazyfree_movetail, cpu);
 	if (pagevec_count(pvec))
 		pagevec_lru_move_fn(pvec, lru_lazyfree_movetail_fn, NULL);

 	activate_page_drain(cpu);
 	invalidate_bh_lrus_cpu(cpu);
 }

 /**
  * deactivate_file_page - forcefully deactivate a file page
  * @page: page to deactivate
  *
  * This function hints the VM that @page is a good reclaim candidate,
  * for example if its invalidation fails due to the page being dirty
  * or under writeback.
  */
 void deactivate_file_page(struct page *page)
 {
 	/*
 	 * In a workload with many unevictable page such as mprotect,
 	 * unevictable page deactivation for accelerating reclaim is pointless.
 	 */
 	if (PageUnevictable(page))
 		return;

 	if (likely(get_page_unless_zero(page))) {
 		struct pagevec *pvec;

 		local_lock(&lru_pvecs.lock);
 		pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate_file);

 		if (pagevec_add_and_need_flush(pvec, page))
 			pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, NULL);
 		local_unlock(&lru_pvecs.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)
 {
 	if (PageLRU(page) && !PageUnevictable(page) && (PageActive(page) || lru_gen_enabled())) {
 		struct pagevec *pvec;

 		local_lock(&lru_pvecs.lock);
 		pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate);
 		get_page(page);
 		if (pagevec_add_and_need_flush(pvec, page))
 			pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
 		local_unlock(&lru_pvecs.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)
 {
 	if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
 	    !PageSwapCache(page) && !PageUnevictable(page)) {
 		struct pagevec *pvec;

 		local_lock(&lru_pvecs.lock);
 		pvec = this_cpu_ptr(&lru_pvecs.lru_lazyfree);
 		get_page(page);
 		if (pagevec_add_and_need_flush(pvec, page))
 			pagevec_lru_move_fn(pvec, lru_lazyfree_fn, NULL);
 		local_unlock(&lru_pvecs.lock);
 	}
 }

 /**
  * mark_page_lazyfree_movetail - make a swapbacked page lazyfree
  * @page: page to deactivate
  *
  * mark_page_lazyfree_movetail() moves @page to the tail of inactive file list.
  * This is done to accelerate the reclaim of @page.
  */
 void mark_page_lazyfree_movetail(struct page *page, bool tail)
 {
 	if (PageLRU(page) && !PageUnevictable(page) && PageSwapBacked(page) &&
 		!PageSwapCache(page)) {
 		struct pagevec *pvec;

 		local_lock(&lru_pvecs.lock);
 		pvec = this_cpu_ptr(&lru_pvecs.lru_lazyfree_movetail);
 		get_page(page);
 		if (pagevec_add_and_need_flush(pvec, page))
 			pagevec_lru_move_fn(pvec,
 					lru_lazyfree_movetail_fn, &tail);
 		local_unlock(&lru_pvecs.lock);
 	}
 }

 void lru_add_drain(void)
 {
 	local_lock(&lru_pvecs.lock);
 	lru_add_drain_cpu(smp_processor_id());
 	local_unlock(&lru_pvecs.lock);
 }

 void lru_add_drain_cpu_zone(struct zone *zone)
 {
 	local_lock(&lru_pvecs.lock);
 	lru_add_drain_cpu(smp_processor_id());
 	drain_local_pages(zone);
 	local_unlock(&lru_pvecs.lock);
 }

 #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_drain();
 }

 /*
  * 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.
  */
 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 pagevec 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 pagevec 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 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 (force_all_cpus ||
 		    pagevec_count(&per_cpu(lru_pvecs.lru_add, cpu)) ||
 		    data_race(pagevec_count(&per_cpu(lru_rotate.pvec, cpu))) ||
 		    pagevec_count(&per_cpu(lru_pvecs.lru_deactivate_file, cpu)) ||
 		    pagevec_count(&per_cpu(lru_pvecs.lru_deactivate, cpu)) ||
 		    pagevec_count(&per_cpu(lru_pvecs.lru_lazyfree, cpu)) ||
 		    pagevec_count(&per_cpu(lru_pvecs.lru_lazyfree_movetail, cpu)) ||
 		    need_activate_page_drain(cpu) ||
 		    has_bh_in_lru(cpu, NULL)) {
 			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 */

 static atomic_t lru_disable_count = ATOMIC_INIT(0);

 bool lru_cache_disabled(void)
 {
 	return atomic_read(&lru_disable_count) != 0;
 }

 void lru_cache_enable(void)
 {
 	atomic_dec(&lru_disable_count);
 }
 EXPORT_SYMBOL_GPL(lru_cache_enable);

 /*
  * 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)
 {
 	/*
 	 * If someone is already disabled lru_cache, just return with
 	 * increasing the lru_disable_count.
 	 */
 	if (atomic_inc_not_zero(&lru_disable_count))
 		return;
 #ifdef CONFIG_SMP
 	/*
 	 * lru_add_drain_all in the force mode will schedule draining on
 	 * all online CPUs so any calls of lru_cache_disabled wrapped by
 	 * local_lock or preemption disabled would be ordered by that.
 	 * The atomic operation doesn't need to have stronger ordering
 	 * requirements because that is enforeced by the scheduling
 	 * guarantees.
 	 */
 	__lru_add_drain_all(true);
 #else
 	lru_add_drain();
 #endif
 	atomic_inc(&lru_disable_count);
 }
 EXPORT_SYMBOL_GPL(lru_cache_disable);

 /**
  * 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 pglist_data *locked_pgdat = NULL;
 	struct lruvec *lruvec;
 	unsigned long flags;
 	unsigned int lock_batch;

 	for (i = 0; i < nr; i++) {
 		struct page *page = pages[i];

 		/*
 		 * Make sure the IRQ-safe lock-holding time does not get
 		 * excessive with a continuous string of pages from the
 		 * same pgdat. The lock is held only if pgdat != NULL.
 		 */
 		if (locked_pgdat && ++lock_batch == SWAP_CLUSTER_MAX) {
 			spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
 			locked_pgdat = NULL;
 		}

 		page = compound_head(page);
 		if (is_huge_zero_page(page))
 			continue;

 		if (is_zone_device_page(page)) {
 			if (locked_pgdat) {
 				spin_unlock_irqrestore(&locked_pgdat->lru_lock,
 						       flags);
 				locked_pgdat = NULL;
 			}
 			/*
 			 * ZONE_DEVICE pages that return 'false' from
 			 * page_is_devmap_managed() do not require special
 			 * processing, and instead, expect a call to
 			 * put_page_testzero().
 			 */
 			if (page_is_devmap_managed(page)) {
 				put_devmap_managed_page(page);
 				continue;
 			}
 		}

 		if (!put_page_testzero(page))
 			continue;

 		if (PageCompound(page)) {
 			if (locked_pgdat) {
 				spin_unlock_irqrestore(&locked_pgdat->lru_lock, flags);
 				locked_pgdat = NULL;
 			}
 			__put_compound_page(page);
 			continue;
 		}

 		if (PageLRU(page)) {
 			struct pglist_data *pgdat = page_pgdat(page);

 			if (pgdat != locked_pgdat) {
 				if (locked_pgdat)
 					spin_unlock_irqrestore(&locked_pgdat->lru_lock,
 									flags);
 				lock_batch = 0;
 				locked_pgdat = pgdat;
 				spin_lock_irqsave(&locked_pgdat->lru_lock, flags);
 			}

 			lruvec = mem_cgroup_page_lruvec(page, locked_pgdat);
 			del_page_from_lru_list(page, lruvec);
 			__clear_page_lru_flags(page);
 		}

 		__ClearPageWaiters(page);

 		list_add(&page->lru, &pages_to_free);
 	}
 	if (locked_pgdat)
 		spin_unlock_irqrestore(&locked_pgdat->lru_lock, 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.  __pagevec_lru_add()
  * and __pagevec_lru_add_active() call release_pages() 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);

 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 /* used by __split_huge_page_refcount() */
 void lru_add_page_tail(struct page *page, struct page *page_tail,
 		       struct lruvec *lruvec, struct list_head *list)
 {
 	VM_BUG_ON_PAGE(!PageHead(page), page);
 	VM_BUG_ON_PAGE(PageCompound(page_tail), page);
 	VM_BUG_ON_PAGE(PageLRU(page_tail), page);
 	lockdep_assert_held(&lruvec_pgdat(lruvec)->lru_lock);

 	if (!list)
 		SetPageLRU(page_tail);

 	if (likely(PageLRU(page)))
 		list_add_tail(&page_tail->lru, &page->lru);
 	else if (list) {
 		/* page reclaim is reclaiming a huge page */
 		get_page(page_tail);
 		list_add_tail(&page_tail->lru, list);
 	} else {
 		/*
 		 * Head page has not yet been counted, as an hpage,
 		 * so we must account for each subpage individually.
 		 *
 		 * Put page_tail on the list at the correct position
 		 * so they all end up in order.
 		 */
 		add_page_to_lru_list_tail(page_tail, lruvec);
 	}
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
 				 void *arg)
 {
 	int was_unevictable = TestClearPageUnevictable(page);
 	int nr_pages = thp_nr_pages(page);

 	VM_BUG_ON_PAGE(PageLRU(page), page);

 	/*
 	 * Page becomes evictable in two ways:
 	 * 1) Within LRU lock [munlock_vma_page() and __munlock_pagevec()].
 	 * 2) Before acquiring LRU lock to put the page to correct LRU and then
 	 *   a) do PageLRU check with lock [check_move_unevictable_pages]
 	 *   b) do PageLRU check before lock [clear_page_mlock]
 	 *
 	 * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need
 	 * following strict ordering:
 	 *
 	 * #0: __pagevec_lru_add_fn		#1: clear_page_mlock
 	 *
 	 * SetPageLRU()				TestClearPageMlocked()
 	 * smp_mb() // explicit ordering	// above provides strict
 	 *					// ordering
 	 * PageMlocked()			PageLRU()
 	 *
 	 *
 	 * if '#1' does not observe setting of PG_lru by '#0' and fails
 	 * isolation, the explicit barrier will make sure that page_evictable
 	 * check will put the page in correct LRU. Without smp_mb(), SetPageLRU
 	 * can be reordered after PageMlocked check and can make '#1' to fail
 	 * the isolation of the page whose Mlocked bit is cleared (#0 is also
 	 * looking at the same page) and the evictable page will be stranded
 	 * in an unevictable LRU.
 	 */
 	SetPageLRU(page);
 	smp_mb__after_atomic();

 	if (page_evictable(page)) {
 		if (was_unevictable)
 			__count_vm_events(UNEVICTABLE_PGRESCUED, nr_pages);
 	} else {
 		ClearPageActive(page);
 		SetPageUnevictable(page);
 		if (!was_unevictable)
 			__count_vm_events(UNEVICTABLE_PGCULLED, nr_pages);
 	}

 	add_page_to_lru_list(page, lruvec);
 	trace_mm_lru_insertion(page);
 }

 /*
  * Add the passed pages to the LRU, then drop the caller's refcount
  * on them.  Reinitialises the caller's pagevec.
  */
 void __pagevec_lru_add(struct pagevec *pvec)
 {
 	pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
 }

 /**
  * pagevec_lookup_entries - gang pagecache lookup
  * @pvec:	Where the resulting entries are placed
  * @mapping:	The address_space to search
  * @start:	The starting entry index
  * @nr_entries:	The maximum number of pages
  * @indices:	The cache indices corresponding to the entries in @pvec
  *
  * pagevec_lookup_entries() will search for and return a group of up
  * to @nr_pages pages and shadow entries in the mapping.  All
  * entries are placed in @pvec.  pagevec_lookup_entries() takes a
  * reference against actual pages in @pvec.
  *
  * The search returns a group of mapping-contiguous entries with
  * ascending indexes.  There may be holes in the indices due to
  * not-present entries.
  *
  * Only one subpage of a Transparent Huge Page is returned in one call:
  * allowing truncate_inode_pages_range() to evict the whole THP without
  * cycling through a pagevec of extra references.
  *
  * pagevec_lookup_entries() returns the number of entries which were
  * found.
  */
 unsigned pagevec_lookup_entries(struct pagevec *pvec,
 				struct address_space *mapping,
 				pgoff_t start, unsigned nr_entries,
 				pgoff_t *indices)
 {
 	pvec->nr = find_get_entries(mapping, start, nr_entries,
 				    pvec->pages, indices);
 	return pagevec_count(pvec);
 }

 /**
  * pagevec_remove_exceptionals - pagevec exceptionals pruning
  * @pvec:	The pagevec to prune
  *
  * pagevec_lookup_entries() fills both pages and exceptional radix
  * tree entries into the pagevec.  This function prunes all
  * exceptionals from @pvec without leaving holes, so that it can be
  * passed on to page-only pagevec operations.
  */
 void pagevec_remove_exceptionals(struct pagevec *pvec)
 {
 	int i, j;

 	for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
 		struct page *page = pvec->pages[i];
 		if (!xa_is_value(page))
 			pvec->pages[j++] = page;
 	}
 	pvec->nr = j;
 }

 /**
  * pagevec_lookup_range - gang pagecache lookup
  * @pvec:	Where the resulting pages are placed
  * @mapping:	The address_space to search
  * @start:	The starting page index
  * @end:	The final page index
  *
  * pagevec_lookup_range() will search for & return a group of up to PAGEVEC_SIZE
  * pages in the mapping starting from index @start and upto index @end
  * (inclusive).  The pages are placed in @pvec.  pagevec_lookup() takes a
  * reference against the pages in @pvec.
  *
  * The search returns a group of mapping-contiguous pages with ascending
  * indexes.  There may be holes in the indices due to not-present pages. We
  * also update @start to index the next page for the traversal.
  *
  * pagevec_lookup_range() returns the number of pages which were found. If this
  * number is smaller than PAGEVEC_SIZE, the end of specified range has been
  * reached.
  */
 unsigned pagevec_lookup_range(struct pagevec *pvec,
 		struct address_space *mapping, pgoff_t *start, pgoff_t end)
 {
 	pvec->nr = find_get_pages_range(mapping, start, end, PAGEVEC_SIZE,
 					pvec->pages);
 	return pagevec_count(pvec);
 }
 EXPORT_SYMBOL(pagevec_lookup_range);

 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);

 unsigned pagevec_lookup_range_nr_tag(struct pagevec *pvec,
 		struct address_space *mapping, pgoff_t *index, pgoff_t end,
 		xa_mark_t tag, unsigned max_pages)
 {
 	pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
 		min_t(unsigned int, max_pages, PAGEVEC_SIZE), pvec->pages);
 	return pagevec_count(pvec);
 }
 EXPORT_SYMBOL(pagevec_lookup_range_nr_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
 	 */
 }

 #ifdef CONFIG_DEV_PAGEMAP_OPS
 void put_devmap_managed_page(struct page *page)
 {
 	int count;

 	if (WARN_ON_ONCE(!page_is_devmap_managed(page)))
 		return;

 	count = page_ref_dec_return(page);

 	/*
 	 * devmap page refcounts are 1-based, rather than 0-based: if
 	 * refcount is 1, then the page is free and the refcount is
 	 * stable because nobody holds a reference on the page.
 	 */
 	if (count == 1)
 		free_devmap_managed_page(page);
 	else if (!count)
 		__put_page(page);
 }
 EXPORT_SYMBOL(put_devmap_managed_page);
 #endif