// 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "internal.h" #include "swap.h" /* * swapper_space is a fiction, retained to simplify the path through * vmscan's shrink_page_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_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 = swp_offset(entry); struct page *page; page = xa_load(&address_space->i_pages, idx); if (xa_is_value(page)) return page; 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 = swp_offset(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 = swp_offset(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); struct address_space *address_space = swap_address_space(entry); XA_STATE(xas, &address_space->i_pages, curr); xas_set_update(&xas, workingset_update_node); xa_lock_irq(&address_space->i_pages); xas_for_each(&xas, old, end) { 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 page *page) { struct folio *folio = page_folio(page); 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) { free_swap_cache(page); if (!is_huge_zero_page(page)) put_page(page); } /* * 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) { lru_add_drain(); for (int i = 0; i < nr; i++) free_swap_cache(encoded_page_ptr(pages[i])); release_pages(pages, nr); } 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), swp_offset(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 = swp_offset(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), swp_offset(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 = (struct folio *)alloc_pages_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, false, 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, false, &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, false, 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; } #define SWAP_RA_ORDER_CEILING 5 struct vma_swap_readahead { unsigned short win; unsigned short offset; unsigned short nr_pte; }; static void swap_ra_info(struct vm_fault *vmf, struct vma_swap_readahead *ra_info) { struct vm_area_struct *vma = vmf->vma; unsigned long ra_val; unsigned long faddr, pfn, fpfn, lpfn, rpfn; unsigned long start, end; unsigned int max_win, hits, prev_win, win; max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster), SWAP_RA_ORDER_CEILING); if (max_win == 1) { ra_info->win = 1; return; } faddr = vmf->address; fpfn = PFN_DOWN(faddr); ra_val = GET_SWAP_RA_VAL(vma); pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val)); prev_win = SWAP_RA_WIN(ra_val); hits = SWAP_RA_HITS(ra_val); ra_info->win = win = __swapin_nr_pages(pfn, fpfn, hits, max_win, prev_win); atomic_long_set(&vma->swap_readahead_info, SWAP_RA_VAL(faddr, win, 0)); if (win == 1) return; if (fpfn == pfn + 1) { lpfn = fpfn; rpfn = fpfn + win; } else if (pfn == fpfn + 1) { lpfn = fpfn - win + 1; rpfn = fpfn + 1; } else { unsigned int left = (win - 1) / 2; lpfn = fpfn - left; rpfn = fpfn + win - left; } start = max3(lpfn, PFN_DOWN(vma->vm_start), PFN_DOWN(faddr & PMD_MASK)); end = min3(rpfn, PFN_DOWN(vma->vm_end), PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE)); ra_info->nr_pte = end - start; ra_info->offset = fpfn - start; } /** * 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; unsigned long addr; swp_entry_t entry; pgoff_t ilx; unsigned int i; bool page_allocated; struct vma_swap_readahead ra_info = { .win = 1, }; swap_ra_info(vmf, &ra_info); if (ra_info.win == 1) goto skip; addr = vmf->address - (ra_info.offset * PAGE_SIZE); ilx = targ_ilx - ra_info.offset; blk_start_plug(&plug); for (i = 0; i < ra_info.nr_pte; i++, 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, false, &splug); if (i != ra_info.offset) { 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, false, 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