1 // SPDX-License-Identifier: GPL-2.0
3 * linux/mm/swap_state.c
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 * Swap reorganised 29.12.95, Stephen Tweedie
8 * Rewritten to use page cache, (C) 1998 Stephen Tweedie
11 #include <linux/gfp.h>
12 #include <linux/kernel_stat.h>
13 #include <linux/mempolicy.h>
14 #include <linux/swap.h>
15 #include <linux/swapops.h>
16 #include <linux/init.h>
17 #include <linux/pagemap.h>
18 #include <linux/pagevec.h>
19 #include <linux/backing-dev.h>
20 #include <linux/blkdev.h>
21 #include <linux/migrate.h>
22 #include <linux/vmalloc.h>
23 #include <linux/swap_slots.h>
24 #include <linux/huge_mm.h>
25 #include <linux/shmem_fs.h>
30 * swapper_space is a fiction, retained to simplify the path through
31 * vmscan's shrink_page_list.
33 static const struct address_space_operations swap_aops = {
34 .writepage = swap_writepage,
35 .dirty_folio = noop_dirty_folio,
36 #ifdef CONFIG_MIGRATION
37 .migrate_folio = migrate_folio,
41 struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
42 static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
43 static bool enable_vma_readahead __read_mostly = true;
45 #define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2)
46 #define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1)
47 #define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK
48 #define SWAP_RA_WIN_MASK (~PAGE_MASK & ~SWAP_RA_HITS_MASK)
50 #define SWAP_RA_HITS(v) ((v) & SWAP_RA_HITS_MASK)
51 #define SWAP_RA_WIN(v) (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT)
52 #define SWAP_RA_ADDR(v) ((v) & PAGE_MASK)
54 #define SWAP_RA_VAL(addr, win, hits) \
55 (((addr) & PAGE_MASK) | \
56 (((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) | \
57 ((hits) & SWAP_RA_HITS_MASK))
59 /* Initial readahead hits is 4 to start up with a small window */
60 #define GET_SWAP_RA_VAL(vma) \
61 (atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
63 static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
65 void show_swap_cache_info(void)
67 printk("%lu pages in swap cache\n", total_swapcache_pages());
68 printk("Free swap = %ldkB\n", K(get_nr_swap_pages()));
69 printk("Total swap = %lukB\n", K(total_swap_pages));
72 void *get_shadow_from_swap_cache(swp_entry_t entry)
74 struct address_space *address_space = swap_address_space(entry);
75 pgoff_t idx = swp_offset(entry);
78 page = xa_load(&address_space->i_pages, idx);
79 if (xa_is_value(page))
85 * add_to_swap_cache resembles filemap_add_folio on swapper_space,
86 * but sets SwapCache flag and private instead of mapping and index.
88 int add_to_swap_cache(struct folio *folio, swp_entry_t entry,
89 gfp_t gfp, void **shadowp)
91 struct address_space *address_space = swap_address_space(entry);
92 pgoff_t idx = swp_offset(entry);
93 XA_STATE_ORDER(xas, &address_space->i_pages, idx, folio_order(folio));
94 unsigned long i, nr = folio_nr_pages(folio);
97 xas_set_update(&xas, workingset_update_node);
99 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
100 VM_BUG_ON_FOLIO(folio_test_swapcache(folio), folio);
101 VM_BUG_ON_FOLIO(!folio_test_swapbacked(folio), folio);
103 folio_ref_add(folio, nr);
104 folio_set_swapcache(folio);
109 xas_create_range(&xas);
112 for (i = 0; i < nr; i++) {
113 VM_BUG_ON_FOLIO(xas.xa_index != idx + i, folio);
115 old = xas_load(&xas);
116 if (xa_is_value(old))
119 xas_store(&xas, folio);
122 address_space->nrpages += nr;
123 __node_stat_mod_folio(folio, NR_FILE_PAGES, nr);
124 __lruvec_stat_mod_folio(folio, NR_SWAPCACHE, nr);
126 xas_unlock_irq(&xas);
127 } while (xas_nomem(&xas, gfp));
129 if (!xas_error(&xas))
132 folio_clear_swapcache(folio);
133 folio_ref_sub(folio, nr);
134 return xas_error(&xas);
138 * This must be called only on folios that have
139 * been verified to be in the swap cache.
141 void __delete_from_swap_cache(struct folio *folio,
142 swp_entry_t entry, void *shadow)
144 struct address_space *address_space = swap_address_space(entry);
146 long nr = folio_nr_pages(folio);
147 pgoff_t idx = swp_offset(entry);
148 XA_STATE(xas, &address_space->i_pages, idx);
150 xas_set_update(&xas, workingset_update_node);
152 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
153 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
154 VM_BUG_ON_FOLIO(folio_test_writeback(folio), folio);
156 for (i = 0; i < nr; i++) {
157 void *entry = xas_store(&xas, shadow);
158 VM_BUG_ON_PAGE(entry != folio, entry);
162 folio_clear_swapcache(folio);
163 address_space->nrpages -= nr;
164 __node_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
165 __lruvec_stat_mod_folio(folio, NR_SWAPCACHE, -nr);
169 * add_to_swap - allocate swap space for a folio
170 * @folio: folio we want to move to swap
172 * Allocate swap space for the folio and add the folio to the
175 * Context: Caller needs to hold the folio lock.
176 * Return: Whether the folio was added to the swap cache.
178 bool add_to_swap(struct folio *folio)
183 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
184 VM_BUG_ON_FOLIO(!folio_test_uptodate(folio), folio);
186 entry = folio_alloc_swap(folio);
191 * XArray node allocations from PF_MEMALLOC contexts could
192 * completely exhaust the page allocator. __GFP_NOMEMALLOC
193 * stops emergency reserves from being allocated.
195 * TODO: this could cause a theoretical memory reclaim
196 * deadlock in the swap out path.
199 * Add it to the swap cache.
201 err = add_to_swap_cache(folio, entry,
202 __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN, NULL);
205 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
206 * clear SWAP_HAS_CACHE flag.
210 * Normally the folio will be dirtied in unmap because its
211 * pte should be dirty. A special case is MADV_FREE page. The
212 * page's pte could have dirty bit cleared but the folio's
213 * SwapBacked flag is still set because clearing the dirty bit
214 * and SwapBacked flag has no lock protected. For such folio,
215 * unmap will not set dirty bit for it, so folio reclaim will
216 * not write the folio out. This can cause data corruption when
217 * the folio is swapped in later. Always setting the dirty flag
218 * for the folio solves the problem.
220 folio_mark_dirty(folio);
225 put_swap_folio(folio, entry);
230 * This must be called only on folios that have
231 * been verified to be in the swap cache and locked.
232 * It will never put the folio into the free list,
233 * the caller has a reference on the folio.
235 void delete_from_swap_cache(struct folio *folio)
237 swp_entry_t entry = folio->swap;
238 struct address_space *address_space = swap_address_space(entry);
240 xa_lock_irq(&address_space->i_pages);
241 __delete_from_swap_cache(folio, entry, NULL);
242 xa_unlock_irq(&address_space->i_pages);
244 put_swap_folio(folio, entry);
245 folio_ref_sub(folio, folio_nr_pages(folio));
248 void clear_shadow_from_swap_cache(int type, unsigned long begin,
251 unsigned long curr = begin;
255 swp_entry_t entry = swp_entry(type, curr);
256 struct address_space *address_space = swap_address_space(entry);
257 XA_STATE(xas, &address_space->i_pages, curr);
259 xas_set_update(&xas, workingset_update_node);
261 xa_lock_irq(&address_space->i_pages);
262 xas_for_each(&xas, old, end) {
263 if (!xa_is_value(old))
265 xas_store(&xas, NULL);
267 xa_unlock_irq(&address_space->i_pages);
269 /* search the next swapcache until we meet end */
270 curr >>= SWAP_ADDRESS_SPACE_SHIFT;
272 curr <<= SWAP_ADDRESS_SPACE_SHIFT;
279 * If we are the only user, then try to free up the swap cache.
281 * Its ok to check the swapcache flag without the folio lock
282 * here because we are going to recheck again inside
283 * folio_free_swap() _with_ the lock.
286 void free_swap_cache(struct folio *folio)
288 if (folio_test_swapcache(folio) && !folio_mapped(folio) &&
289 folio_trylock(folio)) {
290 folio_free_swap(folio);
296 * Perform a free_page(), also freeing any swap cache associated with
297 * this page if it is the last user of the page.
299 void free_page_and_swap_cache(struct page *page)
301 struct folio *folio = page_folio(page);
303 free_swap_cache(folio);
304 if (!is_huge_zero_page(page))
309 * Passed an array of pages, drop them all from swapcache and then release
310 * them. They are removed from the LRU and freed if this is their last use.
312 void free_pages_and_swap_cache(struct encoded_page **pages, int nr)
314 struct folio_batch folios;
315 unsigned int refs[PAGEVEC_SIZE];
318 folio_batch_init(&folios);
319 for (int i = 0; i < nr; i++) {
320 struct folio *folio = page_folio(encoded_page_ptr(pages[i]));
322 free_swap_cache(folio);
324 if (unlikely(encoded_page_flags(pages[i]) &
325 ENCODED_PAGE_BIT_NR_PAGES_NEXT))
326 refs[folios.nr] = encoded_nr_pages(pages[++i]);
328 if (folio_batch_add(&folios, folio) == 0)
329 folios_put_refs(&folios, refs);
332 folios_put_refs(&folios, refs);
335 static inline bool swap_use_vma_readahead(void)
337 return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap);
341 * Lookup a swap entry in the swap cache. A found folio will be returned
342 * unlocked and with its refcount incremented - we rely on the kernel
343 * lock getting page table operations atomic even if we drop the folio
344 * lock before returning.
346 * Caller must lock the swap device or hold a reference to keep it valid.
348 struct folio *swap_cache_get_folio(swp_entry_t entry,
349 struct vm_area_struct *vma, unsigned long addr)
353 folio = filemap_get_folio(swap_address_space(entry), swp_offset(entry));
354 if (!IS_ERR(folio)) {
355 bool vma_ra = swap_use_vma_readahead();
359 * At the moment, we don't support PG_readahead for anon THP
360 * so let's bail out rather than confusing the readahead stat.
362 if (unlikely(folio_test_large(folio)))
365 readahead = folio_test_clear_readahead(folio);
367 unsigned long ra_val;
370 ra_val = GET_SWAP_RA_VAL(vma);
371 win = SWAP_RA_WIN(ra_val);
372 hits = SWAP_RA_HITS(ra_val);
374 hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
375 atomic_long_set(&vma->swap_readahead_info,
376 SWAP_RA_VAL(addr, win, hits));
380 count_vm_event(SWAP_RA_HIT);
382 atomic_inc(&swapin_readahead_hits);
392 * filemap_get_incore_folio - Find and get a folio from the page or swap caches.
393 * @mapping: The address_space to search.
394 * @index: The page cache index.
396 * This differs from filemap_get_folio() in that it will also look for the
397 * folio in the swap cache.
399 * Return: The found folio or %NULL.
401 struct folio *filemap_get_incore_folio(struct address_space *mapping,
405 struct swap_info_struct *si;
406 struct folio *folio = filemap_get_entry(mapping, index);
409 return ERR_PTR(-ENOENT);
410 if (!xa_is_value(folio))
412 if (!shmem_mapping(mapping))
413 return ERR_PTR(-ENOENT);
415 swp = radix_to_swp_entry(folio);
416 /* There might be swapin error entries in shmem mapping. */
417 if (non_swap_entry(swp))
418 return ERR_PTR(-ENOENT);
419 /* Prevent swapoff from happening to us */
420 si = get_swap_device(swp);
422 return ERR_PTR(-ENOENT);
423 index = swp_offset(swp);
424 folio = filemap_get_folio(swap_address_space(swp), index);
429 struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
430 struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated,
433 struct swap_info_struct *si;
437 *new_page_allocated = false;
438 si = get_swap_device(entry);
445 * First check the swap cache. Since this is normally
446 * called after swap_cache_get_folio() failed, re-calling
447 * that would confuse statistics.
449 folio = filemap_get_folio(swap_address_space(entry),
455 * Just skip read ahead for unused swap slot.
456 * During swap_off when swap_slot_cache is disabled,
457 * we have to handle the race between putting
458 * swap entry in swap cache and marking swap slot
459 * as SWAP_HAS_CACHE. That's done in later part of code or
460 * else swap_off will be aborted if we return NULL.
462 if (!swap_swapcount(si, entry) && swap_slot_cache_enabled)
466 * Get a new folio to read into from swap. Allocate it now,
467 * before marking swap_map SWAP_HAS_CACHE, when -EEXIST will
468 * cause any racers to loop around until we add it to cache.
470 folio = (struct folio *)alloc_pages_mpol(gfp_mask, 0,
471 mpol, ilx, numa_node_id());
476 * Swap entry may have been freed since our caller observed it.
478 err = swapcache_prepare(entry);
487 * Protect against a recursive call to __read_swap_cache_async()
488 * on the same entry waiting forever here because SWAP_HAS_CACHE
489 * is set but the folio is not the swap cache yet. This can
490 * happen today if mem_cgroup_swapin_charge_folio() below
491 * triggers reclaim through zswap, which may call
492 * __read_swap_cache_async() in the writeback path.
498 * We might race against __delete_from_swap_cache(), and
499 * stumble across a swap_map entry whose SWAP_HAS_CACHE
500 * has not yet been cleared. Or race against another
501 * __read_swap_cache_async(), which has set SWAP_HAS_CACHE
502 * in swap_map, but not yet added its folio to swap cache.
504 schedule_timeout_uninterruptible(1);
508 * The swap entry is ours to swap in. Prepare the new folio.
511 __folio_set_locked(folio);
512 __folio_set_swapbacked(folio);
514 if (mem_cgroup_swapin_charge_folio(folio, NULL, gfp_mask, entry))
517 /* May fail (-ENOMEM) if XArray node allocation failed. */
518 if (add_to_swap_cache(folio, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow))
521 mem_cgroup_swapin_uncharge_swap(entry);
524 workingset_refault(folio, shadow);
526 /* Caller will initiate read into locked folio */
527 folio_add_lru(folio);
528 *new_page_allocated = true;
534 put_swap_folio(folio, entry);
543 * Locate a page of swap in physical memory, reserving swap cache space
544 * and reading the disk if it is not already cached.
545 * A failure return means that either the page allocation failed or that
546 * the swap entry is no longer in use.
548 * get/put_swap_device() aren't needed to call this function, because
549 * __read_swap_cache_async() call them and swap_read_folio() holds the
550 * swap cache folio lock.
552 struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
553 struct vm_area_struct *vma, unsigned long addr,
554 struct swap_iocb **plug)
557 struct mempolicy *mpol;
561 mpol = get_vma_policy(vma, addr, 0, &ilx);
562 folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
563 &page_allocated, false);
567 swap_read_folio(folio, false, plug);
571 static unsigned int __swapin_nr_pages(unsigned long prev_offset,
572 unsigned long offset,
577 unsigned int pages, last_ra;
580 * This heuristic has been found to work well on both sequential and
581 * random loads, swapping to hard disk or to SSD: please don't ask
582 * what the "+ 2" means, it just happens to work well, that's all.
587 * We can have no readahead hits to judge by: but must not get
588 * stuck here forever, so check for an adjacent offset instead
589 * (and don't even bother to check whether swap type is same).
591 if (offset != prev_offset + 1 && offset != prev_offset - 1)
594 unsigned int roundup = 4;
595 while (roundup < pages)
600 if (pages > max_pages)
603 /* Don't shrink readahead too fast */
604 last_ra = prev_win / 2;
611 static unsigned long swapin_nr_pages(unsigned long offset)
613 static unsigned long prev_offset;
614 unsigned int hits, pages, max_pages;
615 static atomic_t last_readahead_pages;
617 max_pages = 1 << READ_ONCE(page_cluster);
621 hits = atomic_xchg(&swapin_readahead_hits, 0);
622 pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits,
624 atomic_read(&last_readahead_pages));
626 WRITE_ONCE(prev_offset, offset);
627 atomic_set(&last_readahead_pages, pages);
633 * swap_cluster_readahead - swap in pages in hope we need them soon
634 * @entry: swap entry of this memory
635 * @gfp_mask: memory allocation flags
636 * @mpol: NUMA memory allocation policy to be applied
637 * @ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE
639 * Returns the struct folio for entry and addr, after queueing swapin.
641 * Primitive swap readahead code. We simply read an aligned block of
642 * (1 << page_cluster) entries in the swap area. This method is chosen
643 * because it doesn't cost us any seek time. We also make sure to queue
644 * the 'original' request together with the readahead ones...
646 * Note: it is intentional that the same NUMA policy and interleave index
647 * are used for every page of the readahead: neighbouring pages on swap
648 * are fairly likely to have been swapped out from the same node.
650 struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
651 struct mempolicy *mpol, pgoff_t ilx)
654 unsigned long entry_offset = swp_offset(entry);
655 unsigned long offset = entry_offset;
656 unsigned long start_offset, end_offset;
658 struct swap_info_struct *si = swp_swap_info(entry);
659 struct blk_plug plug;
660 struct swap_iocb *splug = NULL;
663 mask = swapin_nr_pages(offset) - 1;
667 /* Read a page_cluster sized and aligned cluster around offset. */
668 start_offset = offset & ~mask;
669 end_offset = offset | mask;
670 if (!start_offset) /* First page is swap header. */
672 if (end_offset >= si->max)
673 end_offset = si->max - 1;
675 blk_start_plug(&plug);
676 for (offset = start_offset; offset <= end_offset ; offset++) {
677 /* Ok, do the async read-ahead now */
678 folio = __read_swap_cache_async(
679 swp_entry(swp_type(entry), offset),
680 gfp_mask, mpol, ilx, &page_allocated, false);
683 if (page_allocated) {
684 swap_read_folio(folio, false, &splug);
685 if (offset != entry_offset) {
686 folio_set_readahead(folio);
687 count_vm_event(SWAP_RA);
692 blk_finish_plug(&plug);
693 swap_read_unplug(splug);
694 lru_add_drain(); /* Push any new pages onto the LRU now */
696 /* The page was likely read above, so no need for plugging here */
697 folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
698 &page_allocated, false);
699 if (unlikely(page_allocated)) {
700 zswap_folio_swapin(folio);
701 swap_read_folio(folio, false, NULL);
706 int init_swap_address_space(unsigned int type, unsigned long nr_pages)
708 struct address_space *spaces, *space;
711 nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
712 spaces = kvcalloc(nr, sizeof(struct address_space), GFP_KERNEL);
715 for (i = 0; i < nr; i++) {
717 xa_init_flags(&space->i_pages, XA_FLAGS_LOCK_IRQ);
718 atomic_set(&space->i_mmap_writable, 0);
719 space->a_ops = &swap_aops;
720 /* swap cache doesn't use writeback related tags */
721 mapping_set_no_writeback_tags(space);
723 nr_swapper_spaces[type] = nr;
724 swapper_spaces[type] = spaces;
729 void exit_swap_address_space(unsigned int type)
732 struct address_space *spaces = swapper_spaces[type];
734 for (i = 0; i < nr_swapper_spaces[type]; i++)
735 VM_WARN_ON_ONCE(!mapping_empty(&spaces[i]));
737 nr_swapper_spaces[type] = 0;
738 swapper_spaces[type] = NULL;
741 #define SWAP_RA_ORDER_CEILING 5
743 struct vma_swap_readahead {
745 unsigned short offset;
746 unsigned short nr_pte;
749 static void swap_ra_info(struct vm_fault *vmf,
750 struct vma_swap_readahead *ra_info)
752 struct vm_area_struct *vma = vmf->vma;
753 unsigned long ra_val;
754 unsigned long faddr, pfn, fpfn, lpfn, rpfn;
755 unsigned long start, end;
756 unsigned int max_win, hits, prev_win, win;
758 max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
759 SWAP_RA_ORDER_CEILING);
765 faddr = vmf->address;
766 fpfn = PFN_DOWN(faddr);
767 ra_val = GET_SWAP_RA_VAL(vma);
768 pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
769 prev_win = SWAP_RA_WIN(ra_val);
770 hits = SWAP_RA_HITS(ra_val);
771 ra_info->win = win = __swapin_nr_pages(pfn, fpfn, hits,
773 atomic_long_set(&vma->swap_readahead_info,
774 SWAP_RA_VAL(faddr, win, 0));
778 if (fpfn == pfn + 1) {
781 } else if (pfn == fpfn + 1) {
782 lpfn = fpfn - win + 1;
785 unsigned int left = (win - 1) / 2;
788 rpfn = fpfn + win - left;
790 start = max3(lpfn, PFN_DOWN(vma->vm_start),
791 PFN_DOWN(faddr & PMD_MASK));
792 end = min3(rpfn, PFN_DOWN(vma->vm_end),
793 PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
795 ra_info->nr_pte = end - start;
796 ra_info->offset = fpfn - start;
800 * swap_vma_readahead - swap in pages in hope we need them soon
801 * @targ_entry: swap entry of the targeted memory
802 * @gfp_mask: memory allocation flags
803 * @mpol: NUMA memory allocation policy to be applied
804 * @targ_ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE
805 * @vmf: fault information
807 * Returns the struct folio for entry and addr, after queueing swapin.
809 * Primitive swap readahead code. We simply read in a few pages whose
810 * virtual addresses are around the fault address in the same vma.
812 * Caller must hold read mmap_lock if vmf->vma is not NULL.
815 static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
816 struct mempolicy *mpol, pgoff_t targ_ilx, struct vm_fault *vmf)
818 struct blk_plug plug;
819 struct swap_iocb *splug = NULL;
821 pte_t *pte = NULL, pentry;
827 struct vma_swap_readahead ra_info = {
831 swap_ra_info(vmf, &ra_info);
832 if (ra_info.win == 1)
835 addr = vmf->address - (ra_info.offset * PAGE_SIZE);
836 ilx = targ_ilx - ra_info.offset;
838 blk_start_plug(&plug);
839 for (i = 0; i < ra_info.nr_pte; i++, ilx++, addr += PAGE_SIZE) {
841 pte = pte_offset_map(vmf->pmd, addr);
845 pentry = ptep_get_lockless(pte);
846 if (!is_swap_pte(pentry))
848 entry = pte_to_swp_entry(pentry);
849 if (unlikely(non_swap_entry(entry)))
853 folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
854 &page_allocated, false);
857 if (page_allocated) {
858 swap_read_folio(folio, false, &splug);
859 if (i != ra_info.offset) {
860 folio_set_readahead(folio);
861 count_vm_event(SWAP_RA);
868 blk_finish_plug(&plug);
869 swap_read_unplug(splug);
872 /* The folio was likely read above, so no need for plugging here */
873 folio = __read_swap_cache_async(targ_entry, gfp_mask, mpol, targ_ilx,
874 &page_allocated, false);
875 if (unlikely(page_allocated)) {
876 zswap_folio_swapin(folio);
877 swap_read_folio(folio, false, NULL);
883 * swapin_readahead - swap in pages in hope we need them soon
884 * @entry: swap entry of this memory
885 * @gfp_mask: memory allocation flags
886 * @vmf: fault information
888 * Returns the struct page for entry and addr, after queueing swapin.
890 * It's a main entry function for swap readahead. By the configuration,
891 * it will read ahead blocks by cluster-based(ie, physical disk based)
892 * or vma-based(ie, virtual address based on faulty address) readahead.
894 struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
895 struct vm_fault *vmf)
897 struct mempolicy *mpol;
901 mpol = get_vma_policy(vmf->vma, vmf->address, 0, &ilx);
902 folio = swap_use_vma_readahead() ?
903 swap_vma_readahead(entry, gfp_mask, mpol, ilx, vmf) :
904 swap_cluster_readahead(entry, gfp_mask, mpol, ilx);
909 return folio_file_page(folio, swp_offset(entry));
913 static ssize_t vma_ra_enabled_show(struct kobject *kobj,
914 struct kobj_attribute *attr, char *buf)
916 return sysfs_emit(buf, "%s\n",
917 enable_vma_readahead ? "true" : "false");
919 static ssize_t vma_ra_enabled_store(struct kobject *kobj,
920 struct kobj_attribute *attr,
921 const char *buf, size_t count)
925 ret = kstrtobool(buf, &enable_vma_readahead);
931 static struct kobj_attribute vma_ra_enabled_attr = __ATTR_RW(vma_ra_enabled);
933 static struct attribute *swap_attrs[] = {
934 &vma_ra_enabled_attr.attr,
938 static const struct attribute_group swap_attr_group = {
942 static int __init swap_init_sysfs(void)
945 struct kobject *swap_kobj;
947 swap_kobj = kobject_create_and_add("swap", mm_kobj);
949 pr_err("failed to create swap kobject\n");
952 err = sysfs_create_group(swap_kobj, &swap_attr_group);
954 pr_err("failed to register swap group\n");
960 kobject_put(swap_kobj);
963 subsys_initcall(swap_init_sysfs);