Contributors: 54
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Huang Ying |
1211 |
33.11% |
20 |
10.10% |
| Matthew Wilcox |
545 |
14.90% |
31 |
15.66% |
| Hugh Dickins |
294 |
8.04% |
14 |
7.07% |
| Shaohua Li |
267 |
7.30% |
5 |
2.53% |
| Andrew Morton |
218 |
5.96% |
18 |
9.09% |
| Linus Torvalds (pre-git) |
177 |
4.84% |
27 |
13.64% |
| JoonSoo Kim |
175 |
4.79% |
2 |
1.01% |
| MinChan Kim |
100 |
2.73% |
5 |
2.53% |
| Linus Torvalds |
59 |
1.61% |
6 |
3.03% |
| Johannes Weiner |
50 |
1.37% |
3 |
1.52% |
| Dmitry Safonov |
48 |
1.31% |
1 |
0.51% |
| Kairui Song |
47 |
1.29% |
4 |
2.02% |
| Rik Van Riel |
44 |
1.20% |
2 |
1.01% |
| David Hildenbrand |
43 |
1.18% |
3 |
1.52% |
| Neil Brown |
41 |
1.12% |
3 |
1.52% |
| Christian Ehrhardt |
32 |
0.88% |
1 |
0.51% |
| Nicholas Piggin |
30 |
0.82% |
5 |
2.53% |
| Shakeel Butt |
30 |
0.82% |
2 |
1.01% |
| Akinobu Mita |
25 |
0.68% |
1 |
0.51% |
| Yang Yang |
24 |
0.66% |
1 |
0.51% |
| Christoph Hellwig |
22 |
0.60% |
3 |
1.52% |
| Domenico Cerasuolo |
21 |
0.57% |
1 |
0.51% |
| Miaohe Lin |
13 |
0.36% |
3 |
1.52% |
| Jagdish Gediya |
11 |
0.30% |
1 |
0.51% |
| Kamezawa Hiroyuki |
11 |
0.30% |
2 |
1.01% |
| Andrea Arcangeli |
10 |
0.27% |
1 |
0.51% |
| Tim Chen |
10 |
0.27% |
2 |
1.01% |
| Christoph Lameter |
10 |
0.27% |
3 |
1.52% |
| Nhat Pham |
10 |
0.27% |
2 |
1.01% |
| Sasha Levin |
8 |
0.22% |
1 |
0.51% |
| Qian Cai |
7 |
0.19% |
1 |
0.51% |
| Michal Hocko |
7 |
0.19% |
1 |
0.51% |
| ZhangPeng |
6 |
0.16% |
1 |
0.51% |
| Jason Gunthorpe |
5 |
0.14% |
1 |
0.51% |
| Tu Jinjiang |
5 |
0.14% |
1 |
0.51% |
| Gerald Schaefer |
5 |
0.14% |
1 |
0.51% |
| Daisuke Nishimura |
4 |
0.11% |
2 |
1.01% |
| Vladimir Davydov |
4 |
0.11% |
1 |
0.51% |
| Guo Ziliang |
4 |
0.11% |
1 |
0.51% |
| Avi Kivity |
3 |
0.08% |
1 |
0.51% |
| Kees Cook |
3 |
0.08% |
1 |
0.51% |
| Changbin Du |
3 |
0.08% |
1 |
0.51% |
| Colin Ian King |
2 |
0.05% |
1 |
0.51% |
| Ryan Roberts |
2 |
0.05% |
1 |
0.51% |
| Eric Sesterhenn / Snakebyte |
2 |
0.05% |
1 |
0.51% |
| Greg Kroah-Hartman |
1 |
0.03% |
1 |
0.51% |
| Aaron Lu |
1 |
0.03% |
1 |
0.51% |
| Rafael Aquini |
1 |
0.03% |
1 |
0.51% |
| Jason Low |
1 |
0.03% |
1 |
0.51% |
| Illia Ostapyshyn |
1 |
0.03% |
1 |
0.51% |
| Joe Perches |
1 |
0.03% |
1 |
0.51% |
| Rikard Falkeborn |
1 |
0.03% |
1 |
0.51% |
| Mike Kravetz |
1 |
0.03% |
1 |
0.51% |
| Kefeng Wang |
1 |
0.03% |
1 |
0.51% |
| Total |
3657 |
|
198 |
|
// 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/swapops.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/swap_slots.h>
#include <linux/huge_mm.h>
#include <linux/shmem_fs.h>
#include "internal.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 = {
.writepage = swap_writepage,
.dirty_folio = noop_dirty_folio,
#ifdef CONFIG_MIGRATION
.migrate_folio = migrate_folio,
#endif
};
struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
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));
}
void *get_shadow_from_swap_cache(swp_entry_t entry)
{
struct address_space *address_space = swap_address_space(entry);
pgoff_t idx = swap_cache_index(entry);
void *shadow;
shadow = xa_load(&address_space->i_pages, idx);
if (xa_is_value(shadow))
return shadow;
return NULL;
}
/*
* add_to_swap_cache resembles filemap_add_folio on swapper_space,
* but sets SwapCache flag and private instead of mapping and index.
*/
int add_to_swap_cache(struct folio *folio, swp_entry_t entry,
gfp_t gfp, void **shadowp)
{
struct address_space *address_space = swap_address_space(entry);
pgoff_t idx = swap_cache_index(entry);
XA_STATE_ORDER(xas, &address_space->i_pages, idx, folio_order(folio));
unsigned long i, nr = folio_nr_pages(folio);
void *old;
xas_set_update(&xas, workingset_update_node);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio), folio);
folio_ref_add(folio, nr);
folio_set_swapcache(folio);
folio->swap = entry;
do {
xas_lock_irq(&xas);
xas_create_range(&xas);
if (xas_error(&xas))
goto unlock;
for (i = 0; i < nr; i++) {
VM_BUG_ON_FOLIO(xas.xa_index != idx + i, folio);
if (shadowp) {
old = xas_load(&xas);
if (xa_is_value(old))
*shadowp = old;
}
xas_store(&xas, folio);
xas_next(&xas);
}
address_space->nrpages += nr;
__node_stat_mod_folio(folio, NR_FILE_PAGES, nr);
__lruvec_stat_mod_folio(folio, NR_SWAPCACHE, nr);
unlock:
xas_unlock_irq(&xas);
} while (xas_nomem(&xas, gfp));
if (!xas_error(&xas))
return 0;
folio_clear_swapcache(folio);
folio_ref_sub(folio, nr);
return xas_error(&xas);
}
/*
* This must be called only on folios that have
* been verified to be in the swap cache.
*/
void __delete_from_swap_cache(struct folio *folio,
swp_entry_t entry, void *shadow)
{
struct address_space *address_space = swap_address_space(entry);
int i;
long nr = folio_nr_pages(folio);
pgoff_t idx = swap_cache_index(entry);
XA_STATE(xas, &address_space->i_pages, idx);
xas_set_update(&xas, workingset_update_node);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
VM_BUG_ON_FOLIO(folio_test_writeback(folio), folio);
for (i = 0; i < nr; i++) {
void *entry = xas_store(&xas, shadow);
VM_BUG_ON_PAGE(entry != folio, entry);
xas_next(&xas);
}
folio->swap.val = 0;
folio_clear_swapcache(folio);
address_space->nrpages -= nr;
__node_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
__lruvec_stat_mod_folio(folio, NR_SWAPCACHE, -nr);
}
/**
* add_to_swap - allocate swap space for a folio
* @folio: folio we want to move to swap
*
* Allocate swap space for the folio and add the folio to the
* swap cache.
*
* Context: Caller needs to hold the folio lock.
* Return: Whether the folio was added to the swap cache.
*/
bool add_to_swap(struct folio *folio)
{
swp_entry_t entry;
int err;
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
VM_BUG_ON_FOLIO(!folio_test_uptodate(folio), folio);
entry = folio_alloc_swap(folio);
if (!entry.val)
return false;
/*
* XArray node allocations from PF_MEMALLOC contexts could
* completely exhaust the page allocator. __GFP_NOMEMALLOC
* stops emergency reserves from being allocated.
*
* TODO: this could cause a theoretical memory reclaim
* deadlock in the swap out path.
*/
/*
* Add it to the swap cache.
*/
err = add_to_swap_cache(folio, entry,
__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN, NULL);
if (err)
/*
* add_to_swap_cache() doesn't return -EEXIST, so we can safely
* clear SWAP_HAS_CACHE flag.
*/
goto fail;
/*
* Normally the folio will be dirtied in unmap because its
* pte should be dirty. A special case is MADV_FREE page. The
* page's pte could have dirty bit cleared but the folio's
* SwapBacked flag is still set because clearing the dirty bit
* and SwapBacked flag has no lock protected. For such folio,
* unmap will not set dirty bit for it, so folio reclaim will
* not write the folio out. This can cause data corruption when
* the folio is swapped in later. Always setting the dirty flag
* for the folio solves the problem.
*/
folio_mark_dirty(folio);
return true;
fail:
put_swap_folio(folio, entry);
return false;
}
/*
* This must be called only on folios that have
* been verified to be in the swap cache and locked.
* It will never put the folio into the free list,
* the caller has a reference on the folio.
*/
void delete_from_swap_cache(struct folio *folio)
{
swp_entry_t entry = folio->swap;
struct address_space *address_space = swap_address_space(entry);
xa_lock_irq(&address_space->i_pages);
__delete_from_swap_cache(folio, entry, NULL);
xa_unlock_irq(&address_space->i_pages);
put_swap_folio(folio, entry);
folio_ref_sub(folio, folio_nr_pages(folio));
}
void clear_shadow_from_swap_cache(int type, unsigned long begin,
unsigned long end)
{
unsigned long curr = begin;
void *old;
for (;;) {
swp_entry_t entry = swp_entry(type, curr);
unsigned long index = curr & SWAP_ADDRESS_SPACE_MASK;
struct address_space *address_space = swap_address_space(entry);
XA_STATE(xas, &address_space->i_pages, index);
xas_set_update(&xas, workingset_update_node);
xa_lock_irq(&address_space->i_pages);
xas_for_each(&xas, old, min(index + (end - curr), SWAP_ADDRESS_SPACE_PAGES)) {
if (!xa_is_value(old))
continue;
xas_store(&xas, NULL);
}
xa_unlock_irq(&address_space->i_pages);
/* search the next swapcache until we meet end */
curr >>= SWAP_ADDRESS_SPACE_SHIFT;
curr++;
curr <<= SWAP_ADDRESS_SPACE_SHIFT;
if (curr > end)
break;
}
}
/*
* 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);
}
}
/*
* Perform a free_page(), also freeing any swap cache associated with
* this page if it is the last user of the page.
*/
void free_page_and_swap_cache(struct page *page)
{
struct folio *folio = page_folio(page);
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];
lru_add_drain();
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);
}
/*
* Lookup a swap entry in the swap cache. A found folio will be returned
* unlocked and with its refcount incremented - we rely on the kernel
* lock getting page table operations atomic even if we drop the folio
* lock before returning.
*
* Caller must lock the swap device or hold a reference to keep it valid.
*/
struct folio *swap_cache_get_folio(swp_entry_t entry,
struct vm_area_struct *vma, unsigned long addr)
{
struct folio *folio;
folio = filemap_get_folio(swap_address_space(entry), swap_cache_index(entry));
if (!IS_ERR(folio)) {
bool vma_ra = swap_use_vma_readahead();
bool 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 folio;
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);
}
} else {
folio = NULL;
}
return folio;
}
/**
* filemap_get_incore_folio - Find and get a folio from the page or swap caches.
* @mapping: The address_space to search.
* @index: The page cache index.
*
* This differs from filemap_get_folio() in that it will also look for the
* folio in the swap cache.
*
* Return: The found folio or %NULL.
*/
struct folio *filemap_get_incore_folio(struct address_space *mapping,
pgoff_t index)
{
swp_entry_t swp;
struct swap_info_struct *si;
struct folio *folio = filemap_get_entry(mapping, index);
if (!folio)
return ERR_PTR(-ENOENT);
if (!xa_is_value(folio))
return folio;
if (!shmem_mapping(mapping))
return ERR_PTR(-ENOENT);
swp = radix_to_swp_entry(folio);
/* There might be swapin error entries in shmem mapping. */
if (non_swap_entry(swp))
return ERR_PTR(-ENOENT);
/* Prevent swapoff from happening to us */
si = get_swap_device(swp);
if (!si)
return ERR_PTR(-ENOENT);
index = swap_cache_index(swp);
folio = filemap_get_folio(swap_address_space(swp), index);
put_swap_device(si);
return folio;
}
struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated,
bool skip_if_exists)
{
struct swap_info_struct *si;
struct folio *folio;
void *shadow = NULL;
*new_page_allocated = false;
si = get_swap_device(entry);
if (!si)
return NULL;
for (;;) {
int err;
/*
* First check the swap cache. Since this is normally
* called after swap_cache_get_folio() failed, re-calling
* that would confuse statistics.
*/
folio = filemap_get_folio(swap_address_space(entry),
swap_cache_index(entry));
if (!IS_ERR(folio))
goto got_folio;
/*
* Just skip read ahead for unused swap slot.
* During swap_off when swap_slot_cache is disabled,
* we have to handle the race between putting
* swap entry in swap cache and marking swap slot
* as SWAP_HAS_CACHE. That's done in later part of code or
* else swap_off will be aborted if we return NULL.
*/
if (!swap_swapcount(si, entry) && swap_slot_cache_enabled)
goto fail_put_swap;
/*
* Get a new folio to read into from swap. Allocate it now,
* before marking swap_map SWAP_HAS_CACHE, when -EEXIST will
* cause any racers to loop around until we add it to cache.
*/
folio = folio_alloc_mpol(gfp_mask, 0, mpol, ilx, numa_node_id());
if (!folio)
goto fail_put_swap;
/*
* Swap entry may have been freed since our caller observed it.
*/
err = swapcache_prepare(entry);
if (!err)
break;
folio_put(folio);
if (err != -EEXIST)
goto fail_put_swap;
/*
* Protect against a recursive call to __read_swap_cache_async()
* on the same entry waiting forever here because SWAP_HAS_CACHE
* is set but the folio is not the swap cache yet. This can
* happen today if mem_cgroup_swapin_charge_folio() below
* triggers reclaim through zswap, which may call
* __read_swap_cache_async() in the writeback path.
*/
if (skip_if_exists)
goto fail_put_swap;
/*
* We might race against __delete_from_swap_cache(), and
* stumble across a swap_map entry whose SWAP_HAS_CACHE
* has not yet been cleared. Or race against another
* __read_swap_cache_async(), which has set SWAP_HAS_CACHE
* in swap_map, but not yet added its folio to swap cache.
*/
schedule_timeout_uninterruptible(1);
}
/*
* The swap entry is ours to swap in. Prepare the new folio.
*/
__folio_set_locked(folio);
__folio_set_swapbacked(folio);
if (mem_cgroup_swapin_charge_folio(folio, NULL, gfp_mask, entry))
goto fail_unlock;
/* May fail (-ENOMEM) if XArray node allocation failed. */
if (add_to_swap_cache(folio, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow))
goto fail_unlock;
mem_cgroup_swapin_uncharge_swap(entry);
if (shadow)
workingset_refault(folio, shadow);
/* Caller will initiate read into locked folio */
folio_add_lru(folio);
*new_page_allocated = true;
got_folio:
put_swap_device(si);
return folio;
fail_unlock:
put_swap_folio(folio, entry);
folio_unlock(folio);
folio_put(folio);
fail_put_swap:
put_swap_device(si);
return NULL;
}
/*
* 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.
*
* get/put_swap_device() aren't needed to call this function, because
* __read_swap_cache_async() call them and swap_read_folio() holds the
* swap cache folio lock.
*/
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)
{
bool page_allocated;
struct mempolicy *mpol;
pgoff_t ilx;
struct folio *folio;
mpol = get_vma_policy(vma, addr, 0, &ilx);
folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
&page_allocated, false);
mpol_cond_put(mpol);
if (page_allocated)
swap_read_folio(folio, plug);
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 = swp_swap_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 = __read_swap_cache_async(
swp_entry(swp_type(entry), offset),
gfp_mask, mpol, ilx, &page_allocated, false);
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 = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
&page_allocated, false);
if (unlikely(page_allocated)) {
zswap_folio_swapin(folio);
swap_read_folio(folio, NULL);
}
return folio;
}
int init_swap_address_space(unsigned int type, unsigned long nr_pages)
{
struct address_space *spaces, *space;
unsigned int i, nr;
nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
spaces = kvcalloc(nr, sizeof(struct address_space), GFP_KERNEL);
if (!spaces)
return -ENOMEM;
for (i = 0; i < nr; i++) {
space = spaces + i;
xa_init_flags(&space->i_pages, XA_FLAGS_LOCK_IRQ);
atomic_set(&space->i_mmap_writable, 0);
space->a_ops = &swap_aops;
/* swap cache doesn't use writeback related tags */
mapping_set_no_writeback_tags(space);
}
nr_swapper_spaces[type] = nr;
swapper_spaces[type] = spaces;
return 0;
}
void exit_swap_address_space(unsigned int type)
{
int i;
struct address_space *spaces = swapper_spaces[type];
for (i = 0; i < nr_swapper_spaces[type]; i++)
VM_WARN_ON_ONCE(!mapping_empty(&spaces[i]));
kvfree(spaces);
nr_swapper_spaces[type] = 0;
swapper_spaces[type] = NULL;
}
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;
swp_entry_t entry;
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) {
if (!pte++) {
pte = pte_offset_map(vmf->pmd, addr);
if (!pte)
break;
}
pentry = ptep_get_lockless(pte);
if (!is_swap_pte(pentry))
continue;
entry = pte_to_swp_entry(pentry);
if (unlikely(non_swap_entry(entry)))
continue;
pte_unmap(pte);
pte = NULL;
folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
&page_allocated, false);
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 = __read_swap_cache_async(targ_entry, gfp_mask, mpol, targ_ilx,
&page_allocated, false);
if (unlikely(page_allocated)) {
zswap_folio_swapin(folio);
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 page 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 page *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);
if (!folio)
return NULL;
return folio_file_page(folio, swp_offset(entry));
}
#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",
enable_vma_readahead ? "true" : "false");
}
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_sysfs(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;
}
return 0;
delete_obj:
kobject_put(swap_kobj);
return err;
}
subsys_initcall(swap_init_sysfs);
#endif