// 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? As a power of 2 */
int page_cluster;
const int page_cluster_max = 31;
/* 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
* in batches. 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);
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_folio() 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_folio() 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->