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/swap.h>
14 #include <linux/swapops.h>
15 #include <linux/init.h>
16 #include <linux/pagemap.h>
17 #include <linux/backing-dev.h>
18 #include <linux/blkdev.h>
19 #include <linux/pagevec.h>
20 #include <linux/migrate.h>
21 #include <linux/vmalloc.h>
22 #include <linux/swap_slots.h>
23 #include <linux/huge_mm.h>
24 #include <linux/shmem_fs.h>
29 * swapper_space is a fiction, retained to simplify the path through
30 * vmscan's shrink_page_list.
32 static const struct address_space_operations swap_aops = {
33 .writepage = swap_writepage,
34 .dirty_folio = noop_dirty_folio,
35 #ifdef CONFIG_MIGRATION
36 .migratepage = migrate_page,
40 struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
41 static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
42 static bool enable_vma_readahead __read_mostly = true;
44 #define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2)
45 #define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1)
46 #define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK
47 #define SWAP_RA_WIN_MASK (~PAGE_MASK & ~SWAP_RA_HITS_MASK)
49 #define SWAP_RA_HITS(v) ((v) & SWAP_RA_HITS_MASK)
50 #define SWAP_RA_WIN(v) (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT)
51 #define SWAP_RA_ADDR(v) ((v) & PAGE_MASK)
53 #define SWAP_RA_VAL(addr, win, hits) \
54 (((addr) & PAGE_MASK) | \
55 (((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) | \
56 ((hits) & SWAP_RA_HITS_MASK))
58 /* Initial readahead hits is 4 to start up with a small window */
59 #define GET_SWAP_RA_VAL(vma) \
60 (atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
62 #define INC_CACHE_INFO(x) data_race(swap_cache_info.x++)
63 #define ADD_CACHE_INFO(x, nr) data_race(swap_cache_info.x += (nr))
66 unsigned long add_total;
67 unsigned long del_total;
68 unsigned long find_success;
69 unsigned long find_total;
72 static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
74 void show_swap_cache_info(void)
76 printk("%lu pages in swap cache\n", total_swapcache_pages());
77 printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
78 swap_cache_info.add_total, swap_cache_info.del_total,
79 swap_cache_info.find_success, swap_cache_info.find_total);
80 printk("Free swap = %ldkB\n",
81 get_nr_swap_pages() << (PAGE_SHIFT - 10));
82 printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
85 void *get_shadow_from_swap_cache(swp_entry_t entry)
87 struct address_space *address_space = swap_address_space(entry);
88 pgoff_t idx = swp_offset(entry);
91 page = xa_load(&address_space->i_pages, idx);
92 if (xa_is_value(page))
98 * add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
99 * but sets SwapCache flag and private instead of mapping and index.
101 int add_to_swap_cache(struct page *page, swp_entry_t entry,
102 gfp_t gfp, void **shadowp)
104 struct address_space *address_space = swap_address_space(entry);
105 pgoff_t idx = swp_offset(entry);
106 XA_STATE_ORDER(xas, &address_space->i_pages, idx, compound_order(page));
107 unsigned long i, nr = thp_nr_pages(page);
110 VM_BUG_ON_PAGE(!PageLocked(page), page);
111 VM_BUG_ON_PAGE(PageSwapCache(page), page);
112 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
114 page_ref_add(page, nr);
115 SetPageSwapCache(page);
119 xas_create_range(&xas);
122 for (i = 0; i < nr; i++) {
123 VM_BUG_ON_PAGE(xas.xa_index != idx + i, page);
124 old = xas_load(&xas);
125 if (xa_is_value(old)) {
129 set_page_private(page + i, entry.val + i);
130 xas_store(&xas, page);
133 address_space->nrpages += nr;
134 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
135 __mod_lruvec_page_state(page, NR_SWAPCACHE, nr);
136 ADD_CACHE_INFO(add_total, nr);
138 xas_unlock_irq(&xas);
139 } while (xas_nomem(&xas, gfp));
141 if (!xas_error(&xas))
144 ClearPageSwapCache(page);
145 page_ref_sub(page, nr);
146 return xas_error(&xas);
150 * This must be called only on pages that have
151 * been verified to be in the swap cache.
153 void __delete_from_swap_cache(struct page *page,
154 swp_entry_t entry, void *shadow)
156 struct address_space *address_space = swap_address_space(entry);
157 int i, nr = thp_nr_pages(page);
158 pgoff_t idx = swp_offset(entry);
159 XA_STATE(xas, &address_space->i_pages, idx);
161 VM_BUG_ON_PAGE(!PageLocked(page), page);
162 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
163 VM_BUG_ON_PAGE(PageWriteback(page), page);
165 for (i = 0; i < nr; i++) {
166 void *entry = xas_store(&xas, shadow);
167 VM_BUG_ON_PAGE(entry != page, entry);
168 set_page_private(page + i, 0);
171 ClearPageSwapCache(page);
172 address_space->nrpages -= nr;
173 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
174 __mod_lruvec_page_state(page, NR_SWAPCACHE, -nr);
175 ADD_CACHE_INFO(del_total, nr);
179 * add_to_swap - allocate swap space for a folio
180 * @folio: folio we want to move to swap
182 * Allocate swap space for the folio and add the folio to the
185 * Context: Caller needs to hold the folio lock.
186 * Return: Whether the folio was added to the swap cache.
188 bool add_to_swap(struct folio *folio)
193 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
194 VM_BUG_ON_FOLIO(!folio_test_uptodate(folio), folio);
196 entry = folio_alloc_swap(folio);
201 * XArray node allocations from PF_MEMALLOC contexts could
202 * completely exhaust the page allocator. __GFP_NOMEMALLOC
203 * stops emergency reserves from being allocated.
205 * TODO: this could cause a theoretical memory reclaim
206 * deadlock in the swap out path.
209 * Add it to the swap cache.
211 err = add_to_swap_cache(&folio->page, entry,
212 __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN, NULL);
215 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
216 * clear SWAP_HAS_CACHE flag.
220 * Normally the folio will be dirtied in unmap because its
221 * pte should be dirty. A special case is MADV_FREE page. The
222 * page's pte could have dirty bit cleared but the folio's
223 * SwapBacked flag is still set because clearing the dirty bit
224 * and SwapBacked flag has no lock protected. For such folio,
225 * unmap will not set dirty bit for it, so folio reclaim will
226 * not write the folio out. This can cause data corruption when
227 * the folio is swapped in later. Always setting the dirty flag
228 * for the folio solves the problem.
230 folio_mark_dirty(folio);
235 put_swap_page(&folio->page, entry);
240 * This must be called only on pages that have
241 * been verified to be in the swap cache and locked.
242 * It will never put the page into the free list,
243 * the caller has a reference on the page.
245 void delete_from_swap_cache(struct page *page)
247 swp_entry_t entry = { .val = page_private(page) };
248 struct address_space *address_space = swap_address_space(entry);
250 xa_lock_irq(&address_space->i_pages);
251 __delete_from_swap_cache(page, entry, NULL);
252 xa_unlock_irq(&address_space->i_pages);
254 put_swap_page(page, entry);
255 page_ref_sub(page, thp_nr_pages(page));
258 void clear_shadow_from_swap_cache(int type, unsigned long begin,
261 unsigned long curr = begin;
265 swp_entry_t entry = swp_entry(type, curr);
266 struct address_space *address_space = swap_address_space(entry);
267 XA_STATE(xas, &address_space->i_pages, curr);
269 xa_lock_irq(&address_space->i_pages);
270 xas_for_each(&xas, old, end) {
271 if (!xa_is_value(old))
273 xas_store(&xas, NULL);
275 xa_unlock_irq(&address_space->i_pages);
277 /* search the next swapcache until we meet end */
278 curr >>= SWAP_ADDRESS_SPACE_SHIFT;
280 curr <<= SWAP_ADDRESS_SPACE_SHIFT;
287 * If we are the only user, then try to free up the swap cache.
289 * Its ok to check for PageSwapCache without the page lock
290 * here because we are going to recheck again inside
291 * try_to_free_swap() _with_ the lock.
294 void free_swap_cache(struct page *page)
296 if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
297 try_to_free_swap(page);
303 * Perform a free_page(), also freeing any swap cache associated with
304 * this page if it is the last user of the page.
306 void free_page_and_swap_cache(struct page *page)
308 free_swap_cache(page);
309 if (!is_huge_zero_page(page))
314 * Passed an array of pages, drop them all from swapcache and then release
315 * them. They are removed from the LRU and freed if this is their last use.
317 void free_pages_and_swap_cache(struct page **pages, int nr)
319 struct page **pagep = pages;
323 for (i = 0; i < nr; i++)
324 free_swap_cache(pagep[i]);
325 release_pages(pagep, nr);
328 static inline bool swap_use_vma_readahead(void)
330 return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap);
334 * Lookup a swap entry in the swap cache. A found page will be returned
335 * unlocked and with its refcount incremented - we rely on the kernel
336 * lock getting page table operations atomic even if we drop the page
337 * lock before returning.
339 struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
343 struct swap_info_struct *si;
345 si = get_swap_device(entry);
348 page = find_get_page(swap_address_space(entry), swp_offset(entry));
351 INC_CACHE_INFO(find_total);
353 bool vma_ra = swap_use_vma_readahead();
356 INC_CACHE_INFO(find_success);
358 * At the moment, we don't support PG_readahead for anon THP
359 * so let's bail out rather than confusing the readahead stat.
361 if (unlikely(PageTransCompound(page)))
364 readahead = TestClearPageReadahead(page);
366 unsigned long ra_val;
369 ra_val = GET_SWAP_RA_VAL(vma);
370 win = SWAP_RA_WIN(ra_val);
371 hits = SWAP_RA_HITS(ra_val);
373 hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
374 atomic_long_set(&vma->swap_readahead_info,
375 SWAP_RA_VAL(addr, win, hits));
379 count_vm_event(SWAP_RA_HIT);
381 atomic_inc(&swapin_readahead_hits);
389 * find_get_incore_page - Find and get a page from the page or swap caches.
390 * @mapping: The address_space to search.
391 * @index: The page cache index.
393 * This differs from find_get_page() in that it will also look for the
394 * page in the swap cache.
396 * Return: The found page or %NULL.
398 struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
401 struct swap_info_struct *si;
402 struct page *page = pagecache_get_page(mapping, index,
403 FGP_ENTRY | FGP_HEAD, 0);
407 if (!xa_is_value(page))
408 return find_subpage(page, index);
409 if (!shmem_mapping(mapping))
412 swp = radix_to_swp_entry(page);
413 /* Prevent swapoff from happening to us */
414 si = get_swap_device(swp);
417 page = find_get_page(swap_address_space(swp), swp_offset(swp));
422 struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
423 struct vm_area_struct *vma, unsigned long addr,
424 bool *new_page_allocated)
426 struct swap_info_struct *si;
430 *new_page_allocated = false;
435 * First check the swap cache. Since this is normally
436 * called after lookup_swap_cache() failed, re-calling
437 * that would confuse statistics.
439 si = get_swap_device(entry);
442 page = find_get_page(swap_address_space(entry),
449 * Just skip read ahead for unused swap slot.
450 * During swap_off when swap_slot_cache is disabled,
451 * we have to handle the race between putting
452 * swap entry in swap cache and marking swap slot
453 * as SWAP_HAS_CACHE. That's done in later part of code or
454 * else swap_off will be aborted if we return NULL.
456 if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
460 * Get a new page to read into from swap. Allocate it now,
461 * before marking swap_map SWAP_HAS_CACHE, when -EEXIST will
462 * cause any racers to loop around until we add it to cache.
464 page = alloc_page_vma(gfp_mask, vma, addr);
469 * Swap entry may have been freed since our caller observed it.
471 err = swapcache_prepare(entry);
480 * We might race against __delete_from_swap_cache(), and
481 * stumble across a swap_map entry whose SWAP_HAS_CACHE
482 * has not yet been cleared. Or race against another
483 * __read_swap_cache_async(), which has set SWAP_HAS_CACHE
484 * in swap_map, but not yet added its page to swap cache.
486 schedule_timeout_uninterruptible(1);
490 * The swap entry is ours to swap in. Prepare the new page.
493 __SetPageLocked(page);
494 __SetPageSwapBacked(page);
496 if (mem_cgroup_swapin_charge_page(page, NULL, gfp_mask, entry))
499 /* May fail (-ENOMEM) if XArray node allocation failed. */
500 if (add_to_swap_cache(page, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow))
503 mem_cgroup_swapin_uncharge_swap(entry);
506 workingset_refault(page_folio(page), shadow);
508 /* Caller will initiate read into locked page */
510 *new_page_allocated = true;
514 put_swap_page(page, entry);
521 * Locate a page of swap in physical memory, reserving swap cache space
522 * and reading the disk if it is not already cached.
523 * A failure return means that either the page allocation failed or that
524 * the swap entry is no longer in use.
526 struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
527 struct vm_area_struct *vma,
528 unsigned long addr, bool do_poll,
529 struct swap_iocb **plug)
531 bool page_was_allocated;
532 struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
533 vma, addr, &page_was_allocated);
535 if (page_was_allocated)
536 swap_readpage(retpage, do_poll, plug);
541 static unsigned int __swapin_nr_pages(unsigned long prev_offset,
542 unsigned long offset,
547 unsigned int pages, last_ra;
550 * This heuristic has been found to work well on both sequential and
551 * random loads, swapping to hard disk or to SSD: please don't ask
552 * what the "+ 2" means, it just happens to work well, that's all.
557 * We can have no readahead hits to judge by: but must not get
558 * stuck here forever, so check for an adjacent offset instead
559 * (and don't even bother to check whether swap type is same).
561 if (offset != prev_offset + 1 && offset != prev_offset - 1)
564 unsigned int roundup = 4;
565 while (roundup < pages)
570 if (pages > max_pages)
573 /* Don't shrink readahead too fast */
574 last_ra = prev_win / 2;
581 static unsigned long swapin_nr_pages(unsigned long offset)
583 static unsigned long prev_offset;
584 unsigned int hits, pages, max_pages;
585 static atomic_t last_readahead_pages;
587 max_pages = 1 << READ_ONCE(page_cluster);
591 hits = atomic_xchg(&swapin_readahead_hits, 0);
592 pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits,
594 atomic_read(&last_readahead_pages));
596 WRITE_ONCE(prev_offset, offset);
597 atomic_set(&last_readahead_pages, pages);
603 * swap_cluster_readahead - swap in pages in hope we need them soon
604 * @entry: swap entry of this memory
605 * @gfp_mask: memory allocation flags
606 * @vmf: fault information
608 * Returns the struct page for entry and addr, after queueing swapin.
610 * Primitive swap readahead code. We simply read an aligned block of
611 * (1 << page_cluster) entries in the swap area. This method is chosen
612 * because it doesn't cost us any seek time. We also make sure to queue
613 * the 'original' request together with the readahead ones...
615 * This has been extended to use the NUMA policies from the mm triggering
618 * Caller must hold read mmap_lock if vmf->vma is not NULL.
620 struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
621 struct vm_fault *vmf)
624 unsigned long entry_offset = swp_offset(entry);
625 unsigned long offset = entry_offset;
626 unsigned long start_offset, end_offset;
628 struct swap_info_struct *si = swp_swap_info(entry);
629 struct blk_plug plug;
630 struct swap_iocb *splug = NULL;
631 bool do_poll = true, page_allocated;
632 struct vm_area_struct *vma = vmf->vma;
633 unsigned long addr = vmf->address;
635 mask = swapin_nr_pages(offset) - 1;
640 /* Read a page_cluster sized and aligned cluster around offset. */
641 start_offset = offset & ~mask;
642 end_offset = offset | mask;
643 if (!start_offset) /* First page is swap header. */
645 if (end_offset >= si->max)
646 end_offset = si->max - 1;
648 blk_start_plug(&plug);
649 for (offset = start_offset; offset <= end_offset ; offset++) {
650 /* Ok, do the async read-ahead now */
651 page = __read_swap_cache_async(
652 swp_entry(swp_type(entry), offset),
653 gfp_mask, vma, addr, &page_allocated);
656 if (page_allocated) {
657 swap_readpage(page, false, &splug);
658 if (offset != entry_offset) {
659 SetPageReadahead(page);
660 count_vm_event(SWAP_RA);
665 blk_finish_plug(&plug);
666 swap_read_unplug(splug);
668 lru_add_drain(); /* Push any new pages onto the LRU now */
670 /* The page was likely read above, so no need for plugging here */
671 return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll, NULL);
674 int init_swap_address_space(unsigned int type, unsigned long nr_pages)
676 struct address_space *spaces, *space;
679 nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
680 spaces = kvcalloc(nr, sizeof(struct address_space), GFP_KERNEL);
683 for (i = 0; i < nr; i++) {
685 xa_init_flags(&space->i_pages, XA_FLAGS_LOCK_IRQ);
686 atomic_set(&space->i_mmap_writable, 0);
687 space->a_ops = &swap_aops;
688 /* swap cache doesn't use writeback related tags */
689 mapping_set_no_writeback_tags(space);
691 nr_swapper_spaces[type] = nr;
692 swapper_spaces[type] = spaces;
697 void exit_swap_address_space(unsigned int type)
700 struct address_space *spaces = swapper_spaces[type];
702 for (i = 0; i < nr_swapper_spaces[type]; i++)
703 VM_WARN_ON_ONCE(!mapping_empty(&spaces[i]));
705 nr_swapper_spaces[type] = 0;
706 swapper_spaces[type] = NULL;
709 static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,
713 unsigned long *start,
716 *start = max3(lpfn, PFN_DOWN(vma->vm_start),
717 PFN_DOWN(faddr & PMD_MASK));
718 *end = min3(rpfn, PFN_DOWN(vma->vm_end),
719 PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
722 static void swap_ra_info(struct vm_fault *vmf,
723 struct vma_swap_readahead *ra_info)
725 struct vm_area_struct *vma = vmf->vma;
726 unsigned long ra_val;
727 unsigned long faddr, pfn, fpfn;
728 unsigned long start, end;
729 pte_t *pte, *orig_pte;
730 unsigned int max_win, hits, prev_win, win, left;
735 max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
736 SWAP_RA_ORDER_CEILING);
742 faddr = vmf->address;
743 orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
745 fpfn = PFN_DOWN(faddr);
746 ra_val = GET_SWAP_RA_VAL(vma);
747 pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
748 prev_win = SWAP_RA_WIN(ra_val);
749 hits = SWAP_RA_HITS(ra_val);
750 ra_info->win = win = __swapin_nr_pages(pfn, fpfn, hits,
752 atomic_long_set(&vma->swap_readahead_info,
753 SWAP_RA_VAL(faddr, win, 0));
760 /* Copy the PTEs because the page table may be unmapped */
762 swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
763 else if (pfn == fpfn + 1)
764 swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1,
767 left = (win - 1) / 2;
768 swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left,
771 ra_info->nr_pte = end - start;
772 ra_info->offset = fpfn - start;
773 pte -= ra_info->offset;
777 tpte = ra_info->ptes;
778 for (pfn = start; pfn != end; pfn++)
785 * swap_vma_readahead - swap in pages in hope we need them soon
786 * @fentry: swap entry of this memory
787 * @gfp_mask: memory allocation flags
788 * @vmf: fault information
790 * Returns the struct page for entry and addr, after queueing swapin.
792 * Primitive swap readahead code. We simply read in a few pages whose
793 * virtual addresses are around the fault address in the same vma.
795 * Caller must hold read mmap_lock if vmf->vma is not NULL.
798 static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
799 struct vm_fault *vmf)
801 struct blk_plug plug;
802 struct swap_iocb *splug = NULL;
803 struct vm_area_struct *vma = vmf->vma;
809 struct vma_swap_readahead ra_info = {
813 swap_ra_info(vmf, &ra_info);
814 if (ra_info.win == 1)
817 blk_start_plug(&plug);
818 for (i = 0, pte = ra_info.ptes; i < ra_info.nr_pte;
821 if (!is_swap_pte(pentry))
823 entry = pte_to_swp_entry(pentry);
824 if (unlikely(non_swap_entry(entry)))
826 page = __read_swap_cache_async(entry, gfp_mask, vma,
827 vmf->address, &page_allocated);
830 if (page_allocated) {
831 swap_readpage(page, false, &splug);
832 if (i != ra_info.offset) {
833 SetPageReadahead(page);
834 count_vm_event(SWAP_RA);
839 blk_finish_plug(&plug);
840 swap_read_unplug(splug);
843 /* The page was likely read above, so no need for plugging here */
844 return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
845 ra_info.win == 1, NULL);
849 * swapin_readahead - swap in pages in hope we need them soon
850 * @entry: swap entry of this memory
851 * @gfp_mask: memory allocation flags
852 * @vmf: fault information
854 * Returns the struct page for entry and addr, after queueing swapin.
856 * It's a main entry function for swap readahead. By the configuration,
857 * it will read ahead blocks by cluster-based(ie, physical disk based)
858 * or vma-based(ie, virtual address based on faulty address) readahead.
860 struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
861 struct vm_fault *vmf)
863 return swap_use_vma_readahead() ?
864 swap_vma_readahead(entry, gfp_mask, vmf) :
865 swap_cluster_readahead(entry, gfp_mask, vmf);
869 static ssize_t vma_ra_enabled_show(struct kobject *kobj,
870 struct kobj_attribute *attr, char *buf)
872 return sysfs_emit(buf, "%s\n",
873 enable_vma_readahead ? "true" : "false");
875 static ssize_t vma_ra_enabled_store(struct kobject *kobj,
876 struct kobj_attribute *attr,
877 const char *buf, size_t count)
881 ret = kstrtobool(buf, &enable_vma_readahead);
887 static struct kobj_attribute vma_ra_enabled_attr = __ATTR_RW(vma_ra_enabled);
889 static struct attribute *swap_attrs[] = {
890 &vma_ra_enabled_attr.attr,
894 static const struct attribute_group swap_attr_group = {
898 static int __init swap_init_sysfs(void)
901 struct kobject *swap_kobj;
903 swap_kobj = kobject_create_and_add("swap", mm_kobj);
905 pr_err("failed to create swap kobject\n");
908 err = sysfs_create_group(swap_kobj, &swap_attr_group);
910 pr_err("failed to register swap group\n");
916 kobject_put(swap_kobj);
919 subsys_initcall(swap_init_sysfs);