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linux-next/mm/swap.c
Miaohe Lin 133d2743ef mm/swap: fix the comment of get_kernel_pages
If no pages were pinned, 0 is returned in fact.  Fix the corresponding
comment.

[akpm@linux-foundation.org: s/nr_pages/nr_segs/ also, per David, reflow comment]
Link: https://lkml.kernel.org/r/20220509131416.17553-15-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-05-19 14:08:52 -07:00

1145 lines
32 KiB
C

// 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;
#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 - and for compound pages.
*/
static void __page_cache_release(struct page *page)
{
if (PageLRU(page)) {
struct folio *folio = page_folio(page);
struct lruvec *lruvec;
unsigned long flags;
lruvec = folio_lruvec_lock_irqsave(folio, &flags);
del_page_from_lru_list(page, lruvec);
__clear_page_lru_flags(page);
unlock_page_lruvec_irqrestore(lruvec, flags);
}
/* See comment on PageMlocked in release_pages() */
if (unlikely(PageMlocked(page))) {
int nr_pages = thp_nr_pages(page);
__ClearPageMlocked(page);
mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
}
}
static void __put_single_page(struct page *page)
{
__page_cache_release(page);
mem_cgroup_uncharge(page_folio(page));
free_unref_page(page, 0);
}
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 (unlikely(is_zone_device_page(page)))
free_zone_device_page(page);
else 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.
*/
void put_pages_list(struct list_head *pages)
{
struct page *page, *next;
list_for_each_entry_safe(page, next, pages, lru) {
if (!put_page_testzero(page)) {
list_del(&page->lru);
continue;
}
if (PageHead(page)) {
list_del(&page->lru);
__put_compound_page(page);
continue;
}
/* Cannot be PageLRU because it's passed to us 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);
static void pagevec_lru_move_fn(struct pagevec *pvec,
void (*move_fn)(struct page *page, struct lruvec *lruvec))
{
int i;
struct lruvec *lruvec = NULL;
unsigned long flags = 0;
for (i = 0; i < pagevec_count(pvec); i++) {
struct page *page = pvec->pages[i];
struct folio *folio = page_folio(page);
/* block memcg migration during page moving between lru */
if (!TestClearPageLRU(page))
continue;
lruvec = folio_lruvec_relock_irqsave(folio, lruvec, &flags);
(*move_fn)(page, lruvec);
SetPageLRU(page);
}
if (lruvec)
unlock_page_lruvec_irqrestore(lruvec, flags);
release_pages(pvec->pages, pvec->nr);
pagevec_reinit(pvec);
}
static void pagevec_move_tail_fn(struct page *page, struct lruvec *lruvec)
{
struct folio *folio = page_folio(page);
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));
}
}
/* 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 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 pagevec *pvec;
unsigned long flags;
folio_get(folio);
local_lock_irqsave(&lru_rotate.lock, flags);
pvec = this_cpu_ptr(&lru_rotate.pvec);
if (pagevec_add_and_need_flush(pvec, &folio->page))
pagevec_lru_move_fn(pvec, pagevec_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(struct folio *folio, struct lruvec *lruvec)
{
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 __activate_page(struct page *page, struct lruvec *lruvec)
{
return __folio_activate(page_folio(page), lruvec);
}
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);
}
static bool need_activate_page_drain(int cpu)
{
return pagevec_count(&per_cpu(lru_pvecs.activate_page, cpu)) != 0;
}
static void folio_activate(struct folio *folio)
{
if (folio_test_lru(folio) && !folio_test_active(folio) &&
!folio_test_unevictable(folio)) {
struct pagevec *pvec;
folio_get(folio);
local_lock(&lru_pvecs.lock);
pvec = this_cpu_ptr(&lru_pvecs.activate_page);
if (pagevec_add_and_need_flush(pvec, &folio->page))
pagevec_lru_move_fn(pvec, __activate_page);
local_unlock(&lru_pvecs.lock);
}
}
#else
static inline void activate_page_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(folio, lruvec);
unlock_page_lruvec_irq(lruvec);
folio_set_lru(folio);
}
}
#endif
static void __lru_cache_activate_folio(struct folio *folio)
{
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 == &folio->page) {
folio_set_active(folio);
break;
}
}
local_unlock(&lru_pvecs.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 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 (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
* pagevec 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 pagevec *pvec;
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(&lru_pvecs.lock);
pvec = this_cpu_ptr(&lru_pvecs.lru_add);
if (pagevec_add_and_need_flush(pvec, &folio->page))
__pagevec_lru_add(pvec);
local_unlock(&lru_pvecs.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 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)
{
bool active = PageActive(page);
int nr_pages = thp_nr_pages(page);
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 move that 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)
{
if (PageActive(page) && !PageUnevictable(page)) {
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)
{
if (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);
}
}
/*
* 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_lru_move_fn(pvec, pagevec_move_tail_fn);
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);
pvec = &per_cpu(lru_pvecs.lru_deactivate, cpu);
if (pagevec_count(pvec))
pagevec_lru_move_fn(pvec, lru_deactivate_fn);
pvec = &per_cpu(lru_pvecs.lru_lazyfree, cpu);
if (pagevec_count(pvec))
pagevec_lru_move_fn(pvec, lru_lazyfree_fn);
activate_page_drain(cpu);
}
/**
* deactivate_file_folio() - Forcefully 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 page.
*/
void deactivate_file_folio(struct folio *folio)
{
struct pagevec *pvec;
/*
* In a workload with many unevictable pages such as mprotect,
* unevictable folio deactivation for accelerating reclaim is pointless.
*/
if (folio_test_unevictable(folio))
return;
folio_get(folio);
local_lock(&lru_pvecs.lock);
pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate_file);
if (pagevec_add_and_need_flush(pvec, &folio->page))
pagevec_lru_move_fn(pvec, lru_deactivate_file_fn);
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) && PageActive(page) && !PageUnevictable(page)) {
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);
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);
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);
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(&lru_pvecs.lock);
lru_add_drain_cpu(smp_processor_id());
local_unlock(&lru_pvecs.lock);
invalidate_bh_lrus_cpu();
mlock_page_drain_local();
}
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);
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();
}
/*
* 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 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 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 (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)) ||
need_activate_page_drain(cpu) ||
need_mlock_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 */
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();
#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 page *page = pages[i];
struct folio *folio = page_folio(page);
/*
* 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;
}
page = &folio->page;
if (is_huge_zero_page(page))
continue;
if (is_zone_device_page(page)) {
if (lruvec) {
unlock_page_lruvec_irqrestore(lruvec, flags);
lruvec = NULL;
}
if (put_devmap_managed_page(page))
continue;
if (put_page_testzero(page))
free_zone_device_page(page);
continue;
}
if (!put_page_testzero(page))
continue;
if (PageCompound(page)) {
if (lruvec) {
unlock_page_lruvec_irqrestore(lruvec, flags);
lruvec = NULL;
}
__put_compound_page(page);
continue;
}
if (PageLRU(page)) {
struct lruvec *prev_lruvec = lruvec;
lruvec = folio_lruvec_relock_irqsave(folio, lruvec,
&flags);
if (prev_lruvec != lruvec)
lock_batch = 0;
del_page_from_lru_list(page, lruvec);
__clear_page_lru_flags(page);
}
/*
* 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(PageMlocked(page))) {
__ClearPageMlocked(page);
dec_zone_page_state(page, NR_MLOCK);
count_vm_event(UNEVICTABLE_PGCLEARED);
}
list_add(&page->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. __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);
static void __pagevec_lru_add_fn(struct folio *folio, struct lruvec *lruvec)
{
int was_unevictable = folio_test_clear_unevictable(folio);
long nr_pages = folio_nr_pages(folio);
VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
folio_set_lru(folio);
/*
* Is an smp_mb__after_atomic() still required here, before
* folio_evictable() tests PageMlocked, to rule out the possibility
* of stranding an evictable folio on an unevictable LRU? I think
* not, because __munlock_page() only clears PageMlocked 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 PageMlocked after
* put_page_testzero() has excluded any other users of the page.)
*/
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);
}
/*
* 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)
{
int i;
struct lruvec *lruvec = NULL;
unsigned long flags = 0;
for (i = 0; i < pagevec_count(pvec); i++) {
struct folio *folio = page_folio(pvec->pages[i]);
lruvec = folio_lruvec_relock_irqsave(folio, lruvec, &flags);
__pagevec_lru_add_fn(folio, lruvec);
}
if (lruvec)
unlock_page_lruvec_irqrestore(lruvec, flags);
release_pages(pvec->pages, pvec->nr);
pagevec_reinit(pvec);
}
/**
* 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;
}
/**
* 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);
/*
* 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
*/
}