Contributors: 59
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Kairui Song |
1155 |
31.10% |
23 |
12.78% |
| Huang Ying |
930 |
25.04% |
14 |
7.78% |
| Hugh Dickins |
289 |
7.78% |
12 |
6.67% |
| Matthew Wilcox |
263 |
7.08% |
19 |
10.56% |
| Shaohua Li |
195 |
5.25% |
4 |
2.22% |
| Linus Torvalds (pre-git) |
147 |
3.96% |
27 |
15.00% |
| Andrew Morton |
116 |
3.12% |
10 |
5.56% |
| MinChan Kim |
97 |
2.61% |
3 |
1.67% |
| JoonSoo Kim |
90 |
2.42% |
2 |
1.11% |
| Neil Brown |
42 |
1.13% |
3 |
1.67% |
| Rik Van Riel |
40 |
1.08% |
2 |
1.11% |
| David Hildenbrand |
39 |
1.05% |
3 |
1.67% |
| Linus Torvalds |
36 |
0.97% |
4 |
2.22% |
| Dmitry Safonov |
34 |
0.92% |
1 |
0.56% |
| Christian Ehrhardt |
32 |
0.86% |
1 |
0.56% |
| Zhaoyu Liu |
25 |
0.67% |
1 |
0.56% |
| Alexandre Ghiti |
19 |
0.51% |
1 |
0.56% |
| Nicholas Piggin |
17 |
0.46% |
2 |
1.11% |
| Shakeel Butt |
15 |
0.40% |
2 |
1.11% |
| Johannes Weiner |
11 |
0.30% |
3 |
1.67% |
| Jagdish Gediya |
11 |
0.30% |
1 |
0.56% |
| Gerald Schaefer |
10 |
0.27% |
2 |
1.11% |
| Andrea Arcangeli |
10 |
0.27% |
1 |
0.56% |
| Christoph Lameter |
8 |
0.22% |
3 |
1.67% |
| Qian Cai |
7 |
0.19% |
1 |
0.56% |
| Lorenzo Stoakes |
7 |
0.19% |
1 |
0.56% |
| Sasha Levin |
6 |
0.16% |
1 |
0.56% |
| ZhangPeng |
6 |
0.16% |
1 |
0.56% |
| Suren Baghdasaryan |
5 |
0.13% |
1 |
0.56% |
| Tu Jinjiang |
5 |
0.13% |
1 |
0.56% |
| Fan Ni |
4 |
0.11% |
1 |
0.56% |
| Kamezawa Hiroyuki |
4 |
0.11% |
1 |
0.56% |
| Yang Yang |
4 |
0.11% |
1 |
0.56% |
| Thorsten Blum |
3 |
0.08% |
1 |
0.56% |
| Avi Kivity |
3 |
0.08% |
1 |
0.56% |
| David Howells |
2 |
0.05% |
1 |
0.56% |
| Colin Ian King |
2 |
0.05% |
1 |
0.56% |
| Christoph Hellwig |
2 |
0.05% |
2 |
1.11% |
| Daniel Jordan |
2 |
0.05% |
1 |
0.56% |
| Tim Chen |
2 |
0.05% |
1 |
0.56% |
| Daisuke Nishimura |
1 |
0.03% |
1 |
0.56% |
| Ryan Roberts |
1 |
0.03% |
1 |
0.56% |
| Jason Low |
1 |
0.03% |
1 |
0.56% |
| Aaron Lu |
1 |
0.03% |
1 |
0.56% |
| Domenico Cerasuolo |
1 |
0.03% |
1 |
0.56% |
| Darrick J. Wong |
1 |
0.03% |
1 |
0.56% |
| Barry Song |
1 |
0.03% |
1 |
0.56% |
| Greg Kroah-Hartman |
1 |
0.03% |
1 |
0.56% |
| Joe Perches |
1 |
0.03% |
1 |
0.56% |
| Michal Hocko |
1 |
0.03% |
1 |
0.56% |
| Changbin Du |
1 |
0.03% |
1 |
0.56% |
| robin.kuo |
1 |
0.03% |
1 |
0.56% |
| Kevin Lourenco |
1 |
0.03% |
1 |
0.56% |
| Illia Ostapyshyn |
1 |
0.03% |
1 |
0.56% |
| Youngjun Park |
1 |
0.03% |
1 |
0.56% |
| Mike Kravetz |
1 |
0.03% |
1 |
0.56% |
| Miaohe Lin |
1 |
0.03% |
1 |
0.56% |
| Taeyang Kim |
1 |
0.03% |
1 |
0.56% |
| Rikard Falkeborn |
1 |
0.03% |
1 |
0.56% |
| Total |
3714 |
|
180 |
|
// SPDX-License-Identifier: GPL-2.0
/*
* linux/mm/swap_state.c
*
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
* Swap reorganised 29.12.95, Stephen Tweedie
*
* Rewritten to use page cache, (C) 1998 Stephen Tweedie
*/
#include <linux/mm.h>
#include <linux/gfp.h>
#include <linux/kernel_stat.h>
#include <linux/mempolicy.h>
#include <linux/swap.h>
#include <linux/leafops.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/backing-dev.h>
#include <linux/blkdev.h>
#include <linux/migrate.h>
#include <linux/vmalloc.h>
#include <linux/huge_mm.h>
#include <linux/shmem_fs.h>
#include "internal.h"
#include "swap_table.h"
#include "swap.h"
/*
* swapper_space is a fiction, retained to simplify the path through
* vmscan's shrink_folio_list.
*/
static const struct address_space_operations swap_aops = {
.dirty_folio = noop_dirty_folio,
#ifdef CONFIG_MIGRATION
.migrate_folio = migrate_folio,
#endif
};
struct address_space swap_space __read_mostly = {
.a_ops = &swap_aops,
};
static bool enable_vma_readahead __read_mostly = true;
#define SWAP_RA_ORDER_CEILING 5
#define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2)
#define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1)
#define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK
#define SWAP_RA_WIN_MASK (~PAGE_MASK & ~SWAP_RA_HITS_MASK)
#define SWAP_RA_HITS(v) ((v) & SWAP_RA_HITS_MASK)
#define SWAP_RA_WIN(v) (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT)
#define SWAP_RA_ADDR(v) ((v) & PAGE_MASK)
#define SWAP_RA_VAL(addr, win, hits) \
(((addr) & PAGE_MASK) | \
(((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) | \
((hits) & SWAP_RA_HITS_MASK))
/* Initial readahead hits is 4 to start up with a small window */
#define GET_SWAP_RA_VAL(vma) \
(atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
void show_swap_cache_info(void)
{
printk("%lu pages in swap cache\n", total_swapcache_pages());
printk("Free swap = %ldkB\n", K(get_nr_swap_pages()));
printk("Total swap = %lukB\n", K(total_swap_pages));
}
/**
* swap_cache_get_folio - Looks up a folio in the swap cache.
* @entry: swap entry used for the lookup.
*
* A found folio will be returned unlocked and with its refcount increased.
*
* Context: Caller must ensure @entry is valid and protect the swap device
* with reference count or locks.
* Return: Returns the found folio on success, NULL otherwise. The caller
* must lock and check if the folio still matches the swap entry before
* use (e.g., folio_matches_swap_entry).
*/
struct folio *swap_cache_get_folio(swp_entry_t entry)
{
unsigned long swp_tb;
struct folio *folio;
for (;;) {
swp_tb = swap_table_get(__swap_entry_to_cluster(entry),
swp_cluster_offset(entry));
if (!swp_tb_is_folio(swp_tb))
return NULL;
folio = swp_tb_to_folio(swp_tb);
if (likely(folio_try_get(folio)))
return folio;
}
return NULL;
}
/**
* swap_cache_has_folio - Check if a swap slot has cache.
* @entry: swap entry indicating the slot.
*
* Context: Caller must ensure @entry is valid and protect the swap
* device with reference count or locks.
*/
bool swap_cache_has_folio(swp_entry_t entry)
{
unsigned long swp_tb;
swp_tb = swap_table_get(__swap_entry_to_cluster(entry),
swp_cluster_offset(entry));
return swp_tb_is_folio(swp_tb);
}
/**
* swap_cache_get_shadow - Looks up a shadow in the swap cache.
* @entry: swap entry used for the lookup.
*
* Context: Caller must ensure @entry is valid and protect the swap device
* with reference count or locks.
* Return: Returns either NULL or an XA_VALUE (shadow).
*/
void *swap_cache_get_shadow(swp_entry_t entry)
{
unsigned long swp_tb;
swp_tb = swap_table_get(__swap_entry_to_cluster(entry),
swp_cluster_offset(entry));
if (swp_tb_is_shadow(swp_tb))
return swp_tb_to_shadow(swp_tb);
return NULL;
}
void __swap_cache_add_folio(struct swap_cluster_info *ci,
struct folio *folio, swp_entry_t entry)
{
unsigned long new_tb;
unsigned int ci_start, ci_off, ci_end;
unsigned long nr_pages = folio_nr_pages(folio);
VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
VM_WARN_ON_ONCE_FOLIO(folio_test_swapcache(folio), folio);
VM_WARN_ON_ONCE_FOLIO(!folio_test_swapbacked(folio), folio);
new_tb = folio_to_swp_tb(folio);
ci_start = swp_cluster_offset(entry);
ci_off = ci_start;
ci_end = ci_start + nr_pages;
do {
VM_WARN_ON_ONCE(swp_tb_is_folio(__swap_table_get(ci, ci_off)));
__swap_table_set(ci, ci_off, new_tb);
} while (++ci_off < ci_end);
folio_ref_add(folio, nr_pages);
folio_set_swapcache(folio);
folio->swap = entry;
node_stat_mod_folio(folio, NR_FILE_PAGES, nr_pages);
lruvec_stat_mod_folio(folio, NR_SWAPCACHE, nr_pages);
}
/**
* swap_cache_add_folio - Add a folio into the swap cache.
* @folio: The folio to be added.
* @entry: The swap entry corresponding to the folio.
* @gfp: gfp_mask for XArray node allocation.
* @shadowp: If a shadow is found, return the shadow.
*
* Context: Caller must ensure @entry is valid and protect the swap device
* with reference count or locks.
*/
static int swap_cache_add_folio(struct folio *folio, swp_entry_t entry,
void **shadowp)
{
int err;
void *shadow = NULL;
unsigned long old_tb;
struct swap_info_struct *si;
struct swap_cluster_info *ci;
unsigned int ci_start, ci_off, ci_end, offset;
unsigned long nr_pages = folio_nr_pages(folio);
si = __swap_entry_to_info(entry);
ci_start = swp_cluster_offset(entry);
ci_end = ci_start + nr_pages;
ci_off = ci_start;
offset = swp_offset(entry);
ci = swap_cluster_lock(si, swp_offset(entry));
if (unlikely(!ci->table)) {
err = -ENOENT;
goto failed;
}
do {
old_tb = __swap_table_get(ci, ci_off);
if (unlikely(swp_tb_is_folio(old_tb))) {
err = -EEXIST;
goto failed;
}
if (unlikely(!__swap_count(swp_entry(swp_type(entry), offset)))) {
err = -ENOENT;
goto failed;
}
if (swp_tb_is_shadow(old_tb))
shadow = swp_tb_to_shadow(old_tb);
offset++;
} while (++ci_off < ci_end);
__swap_cache_add_folio(ci, folio, entry);
swap_cluster_unlock(ci);
if (shadowp)
*shadowp = shadow;
return 0;
failed:
swap_cluster_unlock(ci);
return err;
}
/**
* __swap_cache_del_folio - Removes a folio from the swap cache.
* @ci: The locked swap cluster.
* @folio: The folio.
* @entry: The first swap entry that the folio corresponds to.
* @shadow: shadow value to be filled in the swap cache.
*
* Removes a folio from the swap cache and fills a shadow in place.
* This won't put the folio's refcount. The caller has to do that.
*
* Context: Caller must ensure the folio is locked and in the swap cache
* using the index of @entry, and lock the cluster that holds the entries.
*/
void __swap_cache_del_folio(struct swap_cluster_info *ci, struct folio *folio,
swp_entry_t entry, void *shadow)
{
struct swap_info_struct *si;
unsigned long old_tb, new_tb;
unsigned int ci_start, ci_off, ci_end;
bool folio_swapped = false, need_free = false;
unsigned long nr_pages = folio_nr_pages(folio);
VM_WARN_ON_ONCE(__swap_entry_to_cluster(entry) != ci);
VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio);
VM_WARN_ON_ONCE_FOLIO(folio_test_writeback(folio), folio);
si = __swap_entry_to_info(entry);
new_tb = shadow_swp_to_tb(shadow);
ci_start = swp_cluster_offset(entry);
ci_end = ci_start + nr_pages;
ci_off = ci_start;
do {
/* If shadow is NULL, we sets an empty shadow */
old_tb = __swap_table_xchg(ci, ci_off, new_tb);
WARN_ON_ONCE(!swp_tb_is_folio(old_tb) ||
swp_tb_to_folio(old_tb) != folio);
if (__swap_count(swp_entry(si->type,
swp_offset(entry) + ci_off - ci_start)))
folio_swapped = true;
else
need_free = true;
} while (++ci_off < ci_end);
folio->swap.val = 0;
folio_clear_swapcache(folio);
node_stat_mod_folio(folio, NR_FILE_PAGES, -nr_pages);
lruvec_stat_mod_folio(folio, NR_SWAPCACHE, -nr_pages);
if (!folio_swapped) {
swap_entries_free(si, ci, swp_offset(entry), nr_pages);
} else if (need_free) {
do {
if (!__swap_count(entry))
swap_entries_free(si, ci, swp_offset(entry), 1);
entry.val++;
} while (--nr_pages);
}
}
/**
* swap_cache_del_folio - Removes a folio from the swap cache.
* @folio: The folio.
*
* Same as __swap_cache_del_folio, but handles lock and refcount. The
* caller must ensure the folio is either clean or has a swap count
* equal to zero, or it may cause data loss.
*
* Context: Caller must ensure the folio is locked and in the swap cache.
*/
void swap_cache_del_folio(struct folio *folio)
{
struct swap_cluster_info *ci;
swp_entry_t entry = folio->swap;
ci = swap_cluster_lock(__swap_entry_to_info(entry), swp_offset(entry));
__swap_cache_del_folio(ci, folio, entry, NULL);
swap_cluster_unlock(ci);
folio_ref_sub(folio, folio_nr_pages(folio));
}
/**
* __swap_cache_replace_folio - Replace a folio in the swap cache.
* @ci: The locked swap cluster.
* @old: The old folio to be replaced.
* @new: The new folio.
*
* Replace an existing folio in the swap cache with a new folio. The
* caller is responsible for setting up the new folio's flag and swap
* entries. Replacement will take the new folio's swap entry value as
* the starting offset to override all slots covered by the new folio.
*
* Context: Caller must ensure both folios are locked, and lock the
* cluster that holds the old folio to be replaced.
*/
void __swap_cache_replace_folio(struct swap_cluster_info *ci,
struct folio *old, struct folio *new)
{
swp_entry_t entry = new->swap;
unsigned long nr_pages = folio_nr_pages(new);
unsigned int ci_off = swp_cluster_offset(entry);
unsigned int ci_end = ci_off + nr_pages;
unsigned long old_tb, new_tb;
VM_WARN_ON_ONCE(!folio_test_swapcache(old) || !folio_test_swapcache(new));
VM_WARN_ON_ONCE(!folio_test_locked(old) || !folio_test_locked(new));
VM_WARN_ON_ONCE(!entry.val);
/* Swap cache still stores N entries instead of a high-order entry */
new_tb = folio_to_swp_tb(new);
do {
old_tb = __swap_table_xchg(ci, ci_off, new_tb);
WARN_ON_ONCE(!swp_tb_is_folio(old_tb) || swp_tb_to_folio(old_tb) != old);
} while (++ci_off < ci_end);
/*
* If the old folio is partially replaced (e.g., splitting a large
* folio, the old folio is shrunk, and new split sub folios replace
* the shrunk part), ensure the new folio doesn't overlap it.
*/
if (IS_ENABLED(CONFIG_DEBUG_VM) &&
folio_order(old) != folio_order(new)) {
ci_off = swp_cluster_offset(old->swap);
ci_end = ci_off + folio_nr_pages(old);
while (ci_off++ < ci_end)
WARN_ON_ONCE(swp_tb_to_folio(__swap_table_get(ci, ci_off)) != old);
}
}
/**
* __swap_cache_clear_shadow - Clears a set of shadows in the swap cache.
* @entry: The starting index entry.
* @nr_ents: How many slots need to be cleared.
*
* Context: Caller must ensure the range is valid, all in one single cluster,
* not occupied by any folio, and lock the cluster.
*/
void __swap_cache_clear_shadow(swp_entry_t entry, int nr_ents)
{
struct swap_cluster_info *ci = __swap_entry_to_cluster(entry);
unsigned int ci_off = swp_cluster_offset(entry), ci_end;
unsigned long old;
ci_end = ci_off + nr_ents;
do {
old = __swap_table_xchg(ci, ci_off, null_to_swp_tb());
WARN_ON_ONCE(swp_tb_is_folio(old));
} while (++ci_off < ci_end);
}
/*
* If we are the only user, then try to free up the swap cache.
*
* Its ok to check the swapcache flag without the folio lock
* here because we are going to recheck again inside
* folio_free_swap() _with_ the lock.
* - Marcelo
*/
void free_swap_cache(struct folio *folio)
{
if (folio_test_swapcache(folio) && !folio_mapped(folio) &&
folio_trylock(folio)) {
folio_free_swap(folio);
folio_unlock(folio);
}
}
/*
* Freeing a folio and also freeing any swap cache associated with
* this folio if it is the last user.
*/
void free_folio_and_swap_cache(struct folio *folio)
{
free_swap_cache(folio);
if (!is_huge_zero_folio(folio))
folio_put(folio);
}
/*
* Passed an array of pages, drop them all from swapcache and then release
* them. They are removed from the LRU and freed if this is their last use.
*/
void free_pages_and_swap_cache(struct encoded_page **pages, int nr)
{
struct folio_batch folios;
unsigned int refs[PAGEVEC_SIZE];
folio_batch_init(&folios);
for (int i = 0; i < nr; i++) {
struct folio *folio = page_folio(encoded_page_ptr(pages[i]));
free_swap_cache(folio);
refs[folios.nr] = 1;
if (unlikely(encoded_page_flags(pages[i]) &
ENCODED_PAGE_BIT_NR_PAGES_NEXT))
refs[folios.nr] = encoded_nr_pages(pages[++i]);
if (folio_batch_add(&folios, folio) == 0)
folios_put_refs(&folios, refs);
}
if (folios.nr)
folios_put_refs(&folios, refs);
}
static inline bool swap_use_vma_readahead(void)
{
return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap);
}
/**
* swap_update_readahead - Update the readahead statistics of VMA or globally.
* @folio: the swap cache folio that just got hit.
* @vma: the VMA that should be updated, could be NULL for global update.
* @addr: the addr that triggered the swapin, ignored if @vma is NULL.
*/
void swap_update_readahead(struct folio *folio, struct vm_area_struct *vma,
unsigned long addr)
{
bool readahead, vma_ra = swap_use_vma_readahead();
/*
* At the moment, we don't support PG_readahead for anon THP
* so let's bail out rather than confusing the readahead stat.
*/
if (unlikely(folio_test_large(folio)))
return;
readahead = folio_test_clear_readahead(folio);
if (vma && vma_ra) {
unsigned long ra_val;
int win, hits;
ra_val = GET_SWAP_RA_VAL(vma);
win = SWAP_RA_WIN(ra_val);
hits = SWAP_RA_HITS(ra_val);
if (readahead)
hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
atomic_long_set(&vma->swap_readahead_info,
SWAP_RA_VAL(addr, win, hits));
}
if (readahead) {
count_vm_event(SWAP_RA_HIT);
if (!vma || !vma_ra)
atomic_inc(&swapin_readahead_hits);
}
}
/**
* __swap_cache_prepare_and_add - Prepare the folio and add it to swap cache.
* @entry: swap entry to be bound to the folio.
* @folio: folio to be added.
* @gfp: memory allocation flags for charge, can be 0 if @charged if true.
* @charged: if the folio is already charged.
*
* Update the swap_map and add folio as swap cache, typically before swapin.
* All swap slots covered by the folio must have a non-zero swap count.
*
* Context: Caller must protect the swap device with reference count or locks.
* Return: Returns the folio being added on success. Returns the existing folio
* if @entry is already cached. Returns NULL if raced with swapin or swapoff.
*/
static struct folio *__swap_cache_prepare_and_add(swp_entry_t entry,
struct folio *folio,
gfp_t gfp, bool charged)
{
struct folio *swapcache = NULL;
void *shadow;
int ret;
__folio_set_locked(folio);
__folio_set_swapbacked(folio);
if (!charged && mem_cgroup_swapin_charge_folio(folio, NULL, gfp, entry))
goto failed;
for (;;) {
ret = swap_cache_add_folio(folio, entry, &shadow);
if (!ret)
break;
/*
* Large order allocation needs special handling on
* race: if a smaller folio exists in cache, swapin needs
* to fallback to order 0, and doing a swap cache lookup
* might return a folio that is irrelevant to the faulting
* entry because @entry is aligned down. Just return NULL.
*/
if (ret != -EEXIST || folio_test_large(folio))
goto failed;
swapcache = swap_cache_get_folio(entry);
if (swapcache)
goto failed;
}
memcg1_swapin(entry, folio_nr_pages(folio));
if (shadow)
workingset_refault(folio, shadow);
/* Caller will initiate read into locked folio */
folio_add_lru(folio);
return folio;
failed:
folio_unlock(folio);
return swapcache;
}
/**
* swap_cache_alloc_folio - Allocate folio for swapped out slot in swap cache.
* @entry: the swapped out swap entry to be binded to the folio.
* @gfp_mask: memory allocation flags
* @mpol: NUMA memory allocation policy to be applied
* @ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE
* @new_page_allocated: sets true if allocation happened, false otherwise
*
* Allocate a folio in the swap cache for one swap slot, typically before
* doing IO (e.g. swap in or zswap writeback). The swap slot indicated by
* @entry must have a non-zero swap count (swapped out).
* Currently only supports order 0.
*
* Context: Caller must protect the swap device with reference count or locks.
* Return: Returns the existing folio if @entry is cached already. Returns
* NULL if failed due to -ENOMEM or @entry have a swap count < 1.
*/
struct folio *swap_cache_alloc_folio(swp_entry_t entry, gfp_t gfp_mask,
struct mempolicy *mpol, pgoff_t ilx,
bool *new_page_allocated)
{
struct swap_info_struct *si = __swap_entry_to_info(entry);
struct folio *folio;
struct folio *result = NULL;
*new_page_allocated = false;
/* Check the swap cache again for readahead path. */
folio = swap_cache_get_folio(entry);
if (folio)
return folio;
/* Skip allocation for unused and bad swap slot for readahead. */
if (!swap_entry_swapped(si, entry))
return NULL;
/* Allocate a new folio to be added into the swap cache. */
folio = folio_alloc_mpol(gfp_mask, 0, mpol, ilx, numa_node_id());
if (!folio)
return NULL;
/* Try add the new folio, returns existing folio or NULL on failure. */
result = __swap_cache_prepare_and_add(entry, folio, gfp_mask, false);
if (result == folio)
*new_page_allocated = true;
else
folio_put(folio);
return result;
}
/**
* swapin_folio - swap-in one or multiple entries skipping readahead.
* @entry: starting swap entry to swap in
* @folio: a new allocated and charged folio
*
* Reads @entry into @folio, @folio will be added to the swap cache.
* If @folio is a large folio, the @entry will be rounded down to align
* with the folio size.
*
* Return: returns pointer to @folio on success. If folio is a large folio
* and this raced with another swapin, NULL will be returned to allow fallback
* to order 0. Else, if another folio was already added to the swap cache,
* return that swap cache folio instead.
*/
struct folio *swapin_folio(swp_entry_t entry, struct folio *folio)
{
struct folio *swapcache;
pgoff_t offset = swp_offset(entry);
unsigned long nr_pages = folio_nr_pages(folio);
entry = swp_entry(swp_type(entry), round_down(offset, nr_pages));
swapcache = __swap_cache_prepare_and_add(entry, folio, 0, true);
if (swapcache == folio)
swap_read_folio(folio, NULL);
return swapcache;
}
/*
* Locate a page of swap in physical memory, reserving swap cache space
* and reading the disk if it is not already cached.
* A failure return means that either the page allocation failed or that
* the swap entry is no longer in use.
*/
struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
struct vm_area_struct *vma, unsigned long addr,
struct swap_iocb **plug)
{
struct swap_info_struct *si;
bool page_allocated;
struct mempolicy *mpol;
pgoff_t ilx;
struct folio *folio;
si = get_swap_device(entry);
if (!si)
return NULL;
mpol = get_vma_policy(vma, addr, 0, &ilx);
folio = swap_cache_alloc_folio(entry, gfp_mask, mpol, ilx,
&page_allocated);
mpol_cond_put(mpol);
if (page_allocated)
swap_read_folio(folio, plug);
put_swap_device(si);
return folio;
}
static unsigned int __swapin_nr_pages(unsigned long prev_offset,
unsigned long offset,
int hits,
int max_pages,
int prev_win)
{
unsigned int pages, last_ra;
/*
* This heuristic has been found to work well on both sequential and
* random loads, swapping to hard disk or to SSD: please don't ask
* what the "+ 2" means, it just happens to work well, that's all.
*/
pages = hits + 2;
if (pages == 2) {
/*
* We can have no readahead hits to judge by: but must not get
* stuck here forever, so check for an adjacent offset instead
* (and don't even bother to check whether swap type is same).
*/
if (offset != prev_offset + 1 && offset != prev_offset - 1)
pages = 1;
} else {
unsigned int roundup = 4;
while (roundup < pages)
roundup <<= 1;
pages = roundup;
}
if (pages > max_pages)
pages = max_pages;
/* Don't shrink readahead too fast */
last_ra = prev_win / 2;
if (pages < last_ra)
pages = last_ra;
return pages;
}
static unsigned long swapin_nr_pages(unsigned long offset)
{
static unsigned long prev_offset;
unsigned int hits, pages, max_pages;
static atomic_t last_readahead_pages;
max_pages = 1 << READ_ONCE(page_cluster);
if (max_pages <= 1)
return 1;
hits = atomic_xchg(&swapin_readahead_hits, 0);
pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits,
max_pages,
atomic_read(&last_readahead_pages));
if (!hits)
WRITE_ONCE(prev_offset, offset);
atomic_set(&last_readahead_pages, pages);
return pages;
}
/**
* swap_cluster_readahead - swap in pages in hope we need them soon
* @entry: swap entry of this memory
* @gfp_mask: memory allocation flags
* @mpol: NUMA memory allocation policy to be applied
* @ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE
*
* Returns the struct folio for entry and addr, after queueing swapin.
*
* Primitive swap readahead code. We simply read an aligned block of
* (1 << page_cluster) entries in the swap area. This method is chosen
* because it doesn't cost us any seek time. We also make sure to queue
* the 'original' request together with the readahead ones...
*
* Note: it is intentional that the same NUMA policy and interleave index
* are used for every page of the readahead: neighbouring pages on swap
* are fairly likely to have been swapped out from the same node.
*/
struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
struct mempolicy *mpol, pgoff_t ilx)
{
struct folio *folio;
unsigned long entry_offset = swp_offset(entry);
unsigned long offset = entry_offset;
unsigned long start_offset, end_offset;
unsigned long mask;
struct swap_info_struct *si = __swap_entry_to_info(entry);
struct blk_plug plug;
struct swap_iocb *splug = NULL;
bool page_allocated;
mask = swapin_nr_pages(offset) - 1;
if (!mask)
goto skip;
/* Read a page_cluster sized and aligned cluster around offset. */
start_offset = offset & ~mask;
end_offset = offset | mask;
if (!start_offset) /* First page is swap header. */
start_offset++;
if (end_offset >= si->max)
end_offset = si->max - 1;
blk_start_plug(&plug);
for (offset = start_offset; offset <= end_offset ; offset++) {
/* Ok, do the async read-ahead now */
folio = swap_cache_alloc_folio(
swp_entry(swp_type(entry), offset), gfp_mask, mpol, ilx,
&page_allocated);
if (!folio)
continue;
if (page_allocated) {
swap_read_folio(folio, &splug);
if (offset != entry_offset) {
folio_set_readahead(folio);
count_vm_event(SWAP_RA);
}
}
folio_put(folio);
}
blk_finish_plug(&plug);
swap_read_unplug(splug);
lru_add_drain(); /* Push any new pages onto the LRU now */
skip:
/* The page was likely read above, so no need for plugging here */
folio = swap_cache_alloc_folio(entry, gfp_mask, mpol, ilx,
&page_allocated);
if (unlikely(page_allocated))
swap_read_folio(folio, NULL);
return folio;
}
static int swap_vma_ra_win(struct vm_fault *vmf, unsigned long *start,
unsigned long *end)
{
struct vm_area_struct *vma = vmf->vma;
unsigned long ra_val;
unsigned long faddr, prev_faddr, left, right;
unsigned int max_win, hits, prev_win, win;
max_win = 1 << min(READ_ONCE(page_cluster), SWAP_RA_ORDER_CEILING);
if (max_win == 1)
return 1;
faddr = vmf->address;
ra_val = GET_SWAP_RA_VAL(vma);
prev_faddr = SWAP_RA_ADDR(ra_val);
prev_win = SWAP_RA_WIN(ra_val);
hits = SWAP_RA_HITS(ra_val);
win = __swapin_nr_pages(PFN_DOWN(prev_faddr), PFN_DOWN(faddr), hits,
max_win, prev_win);
atomic_long_set(&vma->swap_readahead_info, SWAP_RA_VAL(faddr, win, 0));
if (win == 1)
return 1;
if (faddr == prev_faddr + PAGE_SIZE)
left = faddr;
else if (prev_faddr == faddr + PAGE_SIZE)
left = faddr - (win << PAGE_SHIFT) + PAGE_SIZE;
else
left = faddr - (((win - 1) / 2) << PAGE_SHIFT);
right = left + (win << PAGE_SHIFT);
if ((long)left < 0)
left = 0;
*start = max3(left, vma->vm_start, faddr & PMD_MASK);
*end = min3(right, vma->vm_end, (faddr & PMD_MASK) + PMD_SIZE);
return win;
}
/**
* swap_vma_readahead - swap in pages in hope we need them soon
* @targ_entry: swap entry of the targeted memory
* @gfp_mask: memory allocation flags
* @mpol: NUMA memory allocation policy to be applied
* @targ_ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE
* @vmf: fault information
*
* Returns the struct folio for entry and addr, after queueing swapin.
*
* Primitive swap readahead code. We simply read in a few pages whose
* virtual addresses are around the fault address in the same vma.
*
* Caller must hold read mmap_lock if vmf->vma is not NULL.
*
*/
static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
struct mempolicy *mpol, pgoff_t targ_ilx, struct vm_fault *vmf)
{
struct blk_plug plug;
struct swap_iocb *splug = NULL;
struct folio *folio;
pte_t *pte = NULL, pentry;
int win;
unsigned long start, end, addr;
pgoff_t ilx;
bool page_allocated;
win = swap_vma_ra_win(vmf, &start, &end);
if (win == 1)
goto skip;
ilx = targ_ilx - PFN_DOWN(vmf->address - start);
blk_start_plug(&plug);
for (addr = start; addr < end; ilx++, addr += PAGE_SIZE) {
struct swap_info_struct *si = NULL;
softleaf_t entry;
if (!pte++) {
pte = pte_offset_map(vmf->pmd, addr);
if (!pte)
break;
}
pentry = ptep_get_lockless(pte);
entry = softleaf_from_pte(pentry);
if (!softleaf_is_swap(entry))
continue;
pte_unmap(pte);
pte = NULL;
/*
* Readahead entry may come from a device that we are not
* holding a reference to, try to grab a reference, or skip.
*/
if (swp_type(entry) != swp_type(targ_entry)) {
si = get_swap_device(entry);
if (!si)
continue;
}
folio = swap_cache_alloc_folio(entry, gfp_mask, mpol, ilx,
&page_allocated);
if (si)
put_swap_device(si);
if (!folio)
continue;
if (page_allocated) {
swap_read_folio(folio, &splug);
if (addr != vmf->address) {
folio_set_readahead(folio);
count_vm_event(SWAP_RA);
}
}
folio_put(folio);
}
if (pte)
pte_unmap(pte);
blk_finish_plug(&plug);
swap_read_unplug(splug);
lru_add_drain();
skip:
/* The folio was likely read above, so no need for plugging here */
folio = swap_cache_alloc_folio(targ_entry, gfp_mask, mpol, targ_ilx,
&page_allocated);
if (unlikely(page_allocated))
swap_read_folio(folio, NULL);
return folio;
}
/**
* swapin_readahead - swap in pages in hope we need them soon
* @entry: swap entry of this memory
* @gfp_mask: memory allocation flags
* @vmf: fault information
*
* Returns the struct folio for entry and addr, after queueing swapin.
*
* It's a main entry function for swap readahead. By the configuration,
* it will read ahead blocks by cluster-based(ie, physical disk based)
* or vma-based(ie, virtual address based on faulty address) readahead.
*/
struct folio *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
struct vm_fault *vmf)
{
struct mempolicy *mpol;
pgoff_t ilx;
struct folio *folio;
mpol = get_vma_policy(vmf->vma, vmf->address, 0, &ilx);
folio = swap_use_vma_readahead() ?
swap_vma_readahead(entry, gfp_mask, mpol, ilx, vmf) :
swap_cluster_readahead(entry, gfp_mask, mpol, ilx);
mpol_cond_put(mpol);
return folio;
}
#ifdef CONFIG_SYSFS
static ssize_t vma_ra_enabled_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sysfs_emit(buf, "%s\n", str_true_false(enable_vma_readahead));
}
static ssize_t vma_ra_enabled_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
ssize_t ret;
ret = kstrtobool(buf, &enable_vma_readahead);
if (ret)
return ret;
return count;
}
static struct kobj_attribute vma_ra_enabled_attr = __ATTR_RW(vma_ra_enabled);
static struct attribute *swap_attrs[] = {
&vma_ra_enabled_attr.attr,
NULL,
};
static const struct attribute_group swap_attr_group = {
.attrs = swap_attrs,
};
static int __init swap_init(void)
{
int err;
struct kobject *swap_kobj;
swap_kobj = kobject_create_and_add("swap", mm_kobj);
if (!swap_kobj) {
pr_err("failed to create swap kobject\n");
return -ENOMEM;
}
err = sysfs_create_group(swap_kobj, &swap_attr_group);
if (err) {
pr_err("failed to register swap group\n");
goto delete_obj;
}
/* Swap cache writeback is LRU based, no tags for it */
mapping_set_no_writeback_tags(&swap_space);
return 0;
delete_obj:
kobject_put(swap_kobj);
return err;
}
subsys_initcall(swap_init);
#endif