// 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_table.h" #include "swap.h" /* * swapper_space is a fiction, retained to simplify the path through * vmscan's shrink_folio_list. */ static const struct address_space_operations swap_aops = { .dirty_folio = noop_dirty_folio, #ifdef CONFIG_MIGRATION .migrate_folio = migrate_folio, #endif }; struct address_space swap_space __read_mostly = { .a_ops = &swap_aops, }; static bool enable_vma_readahead __read_mostly = true; #define SWAP_RA_ORDER_CEILING 5 #define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2) #define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1) #define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK #define SWAP_RA_WIN_MASK (~PAGE_MASK & ~SWAP_RA_HITS_MASK) #define SWAP_RA_HITS(v) ((v) & SWAP_RA_HITS_MASK) #define SWAP_RA_WIN(v) (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT) #define SWAP_RA_ADDR(v) ((v) & PAGE_MASK) #define SWAP_RA_VAL(addr, win, hits) \ (((addr) & PAGE_MASK) | \ (((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) | \ ((hits) & SWAP_RA_HITS_MASK)) /* Initial readahead hits is 4 to start up with a small window */ #define GET_SWAP_RA_VAL(vma) \ (atomic_long_read(&(vma)->swap_readahead_info) ? : 4) static atomic_t swapin_readahead_hits = ATOMIC_INIT(4); void show_swap_cache_info(void) { printk("%lu pages in swap cache\n", total_swapcache_pages()); printk("Free swap = %ldkB\n", K(get_nr_swap_pages())); printk("Total swap = %lukB\n", K(total_swap_pages)); } /** * swap_cache_get_folio - Looks up a folio in the swap cache. * @entry: swap entry used for the lookup. * * A found folio will be returned unlocked and with its refcount increased. * * Context: Caller must ensure @entry is valid and protect the swap device * with reference count or locks. * Return: Returns the found folio on success, NULL otherwise. The caller * must lock and check if the folio still matches the swap entry before * use (e.g., folio_matches_swap_entry). */ struct folio *swap_cache_get_folio(swp_entry_t entry) { unsigned long swp_tb; struct folio *folio; for (;;) { swp_tb = swap_table_get(__swap_entry_to_cluster(entry), swp_cluster_offset(entry)); if (!swp_tb_is_folio(swp_tb)) return NULL; folio = swp_tb_to_folio(swp_tb); if (likely(folio_try_get(folio))) return folio; } return NULL; } /** * swap_cache_has_folio - Check if a swap slot has cache. * @entry: swap entry indicating the slot. * * Context: Caller must ensure @entry is valid and protect the swap * device with reference count or locks. */ bool swap_cache_has_folio(swp_entry_t entry) { unsigned long swp_tb; swp_tb = swap_table_get(__swap_entry_to_cluster(entry), swp_cluster_offset(entry)); return swp_tb_is_folio(swp_tb); } /** * swap_cache_get_shadow - Looks up a shadow in the swap cache. * @entry: swap entry used for the lookup. * * Context: Caller must ensure @entry is valid and protect the swap device * with reference count or locks. * Return: Returns either NULL or an XA_VALUE (shadow). */ void *swap_cache_get_shadow(swp_entry_t entry) { unsigned long swp_tb; swp_tb = swap_table_get(__swap_entry_to_cluster(entry), swp_cluster_offset(entry)); if (swp_tb_is_shadow(swp_tb)) return swp_tb_to_shadow(swp_tb); return NULL; } void __swap_cache_add_folio(struct swap_cluster_info *ci, struct folio *folio, swp_entry_t entry) { unsigned long new_tb; unsigned int ci_start, ci_off, ci_end; unsigned long nr_pages = folio_nr_pages(folio); VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_test_swapcache(folio), folio); VM_WARN_ON_ONCE_FOLIO(!folio_test_swapbacked(folio), folio); new_tb = folio_to_swp_tb(folio); ci_start = swp_cluster_offset(entry); ci_off = ci_start; ci_end = ci_start + nr_pages; do { VM_WARN_ON_ONCE(swp_tb_is_folio(__swap_table_get(ci, ci_off))); __swap_table_set(ci, ci_off, new_tb); } while (++ci_off < ci_end); folio_ref_add(folio, nr_pages); folio_set_swapcache(folio); folio->swap = entry; node_stat_mod_folio(folio, NR_FILE_PAGES, nr_pages); lruvec_stat_mod_folio(folio, NR_SWAPCACHE, nr_pages); } /** * swap_cache_add_folio - Add a folio into the swap cache. * @folio: The folio to be added. * @entry: The swap entry corresponding to the folio. * @gfp: gfp_mask for XArray node allocation. * @shadowp: If a shadow is found, return the shadow. * * Context: Caller must ensure @entry is valid and protect the swap device * with reference count or locks. */ static int swap_cache_add_folio(struct folio *folio, swp_entry_t entry, void **shadowp) { int err; void *shadow = NULL; unsigned long old_tb; struct swap_info_struct *si; struct swap_cluster_info *ci; unsigned int ci_start, ci_off, ci_end, offset; unsigned long nr_pages = folio_nr_pages(folio); si = __swap_entry_to_info(entry); ci_start = swp_cluster_offset(entry); ci_end = ci_start + nr_pages; ci_off = ci_start; offset = swp_offset(entry); ci = swap_cluster_lock(si, swp_offset(entry)); if (unlikely(!ci->table)) { err = -ENOENT; goto failed; } do { old_tb = __swap_table_get(ci, ci_off); if (unlikely(swp_tb_is_folio(old_tb))) { err = -EEXIST; goto failed; } if (unlikely(!__swap_count(swp_entry(swp_type(entry), offset)))) { err = -ENOENT; goto failed; } if (swp_tb_is_shadow(old_tb)) shadow = swp_tb_to_shadow(old_tb); offset++; } while (++ci_off < ci_end); __swap_cache_add_folio(ci, folio, entry); swap_cluster_unlock(ci); if (shadowp) *shadowp = shadow; return 0; failed: swap_cluster_unlock(ci); return err; } /** * __swap_cache_del_folio - Removes a folio from the swap cache. * @ci: The locked swap cluster. * @folio: The folio. * @entry: The first swap entry that the folio corresponds to. * @shadow: shadow value to be filled in the swap cache. * * Removes a folio from the swap cache and fills a shadow in place. * This won't put the folio's refcount. The caller has to do that. * * Context: Caller must ensure the folio is locked and in the swap cache * using the index of @entry, and lock the cluster that holds the entries. */ void __swap_cache_del_folio(struct swap_cluster_info *ci, struct folio *folio, swp_entry_t entry, void *shadow) { struct swap_info_struct *si; unsigned long old_tb, new_tb; unsigned int ci_start, ci_off, ci_end; bool folio_swapped = false, need_free = false; unsigned long nr_pages = folio_nr_pages(folio); VM_WARN_ON_ONCE(__swap_entry_to_cluster(entry) != ci); VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio); VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio); VM_WARN_ON_ONCE_FOLIO(folio_test_writeback(folio), folio); si = __swap_entry_to_info(entry); new_tb = shadow_swp_to_tb(shadow); ci_start = swp_cluster_offset(entry); ci_end = ci_start + nr_pages; ci_off = ci_start; do { /* If shadow is NULL, we sets an empty shadow */ old_tb = __swap_table_xchg(ci, ci_off, new_tb); WARN_ON_ONCE(!swp_tb_is_folio(old_tb) || swp_tb_to_folio(old_tb) != folio); if (__swap_count(swp_entry(si->type, swp_offset(entry) + ci_off - ci_start))) folio_swapped = true; else need_free = true; } while (++ci_off < ci_end); folio->swap.val = 0; folio_clear_swapcache(folio); node_stat_mod_folio(folio, NR_FILE_PAGES, -nr_pages); lruvec_stat_mod_folio(folio, NR_SWAPCACHE, -nr_pages); if (!folio_swapped) { swap_entries_free(si, ci, swp_offset(entry), nr_pages); } else if (need_free) { do { if (!__swap_count(entry)) swap_entries_free(si, ci, swp_offset(entry), 1); entry.val++; } while (--nr_pages); } } /** * swap_cache_del_folio - Removes a folio from the swap cache. * @folio: The folio. * * Same as __swap_cache_del_folio, but handles lock and refcount. The * caller must ensure the folio is either clean or has a swap count * equal to zero, or it may cause data loss. * * Context: Caller must ensure the folio is locked and in the swap cache. */ void swap_cache_del_folio(struct folio *folio) { struct swap_cluster_info *ci; swp_entry_t entry = folio->swap; ci = swap_cluster_lock(__swap_entry_to_info(entry), swp_offset(entry)); __swap_cache_del_folio(ci, folio, entry, NULL); swap_cluster_unlock(ci); folio_ref_sub(folio, folio_nr_pages(folio)); } /** * __swap_cache_replace_folio - Replace a folio in the swap cache. * @ci: The locked swap cluster. * @old: The old folio to be replaced. * @new: The new folio. * * Replace an existing folio in the swap cache with a new folio. The * caller is responsible for setting up the new folio's flag and swap * entries. Replacement will take the new folio's swap entry value as * the starting offset to override all slots covered by the new folio. * * Context: Caller must ensure both folios are locked, and lock the * cluster that holds the old folio to be replaced. */ void __swap_cache_replace_folio(struct swap_cluster_info *ci, struct folio *old, struct folio *new) { swp_entry_t entry = new->swap; unsigned long nr_pages = folio_nr_pages(new); unsigned int ci_off = swp_cluster_offset(entry); unsigned int ci_end = ci_off + nr_pages; unsigned long old_tb, new_tb; VM_WARN_ON_ONCE(!folio_test_swapcache(old) || !folio_test_swapcache(new)); VM_WARN_ON_ONCE(!folio_test_locked(old) || !folio_test_locked(new)); VM_WARN_ON_ONCE(!entry.val); /* Swap cache still stores N entries instead of a high-order entry */ new_tb = folio_to_swp_tb(new); do { old_tb = __swap_table_xchg(ci, ci_off, new_tb); WARN_ON_ONCE(!swp_tb_is_folio(old_tb) || swp_tb_to_folio(old_tb) != old); } while (++ci_off < ci_end); /* * If the old folio is partially replaced (e.g., splitting a large * folio, the old folio is shrunk, and new split sub folios replace * the shrunk part), ensure the new folio doesn't overlap it. */ if (IS_ENABLED(CONFIG_DEBUG_VM) && folio_order(old) != folio_order(new)) { ci_off = swp_cluster_offset(old->swap); ci_end = ci_off + folio_nr_pages(old); while (ci_off++ < ci_end) WARN_ON_ONCE(swp_tb_to_folio(__swap_table_get(ci, ci_off)) != old); } } /** * __swap_cache_clear_shadow - Clears a set of shadows in the swap cache. * @entry: The starting index entry. * @nr_ents: How many slots need to be cleared. * * Context: Caller must ensure the range is valid, all in one single cluster, * not occupied by any folio, and lock the cluster. */ void __swap_cache_clear_shadow(swp_entry_t entry, int nr_ents) { struct swap_cluster_info *ci = __swap_entry_to_cluster(entry); unsigned int ci_off = swp_cluster_offset(entry), ci_end; unsigned long old; ci_end = ci_off + nr_ents; do { old = __swap_table_xchg(ci, ci_off, null_to_swp_tb()); WARN_ON_ONCE(swp_tb_is_folio(old)); } while (++ci_off < ci_end); } /* * If we are the only user, then try to free up the swap cache. * * Its ok to check the swapcache flag without the folio lock * here because we are going to recheck again inside * folio_free_swap() _with_ the lock. * - Marcelo */ void free_swap_cache(struct folio *folio) { if (folio_test_swapcache(folio) && !folio_mapped(folio) && folio_trylock(folio)) { folio_free_swap(folio); folio_unlock(folio); } } /* * Freeing a folio and also freeing any swap cache associated with * this folio if it is the last user. */ void free_folio_and_swap_cache(struct folio *folio) { free_swap_cache(folio); if (!is_huge_zero_folio(folio)) folio_put(folio); } /* * Passed an array of pages, drop them all from swapcache and then release * them. They are removed from the LRU and freed if this is their last use. */ void free_pages_and_swap_cache(struct encoded_page **pages, int nr) { struct folio_batch folios; unsigned int refs[PAGEVEC_SIZE]; folio_batch_init(&folios); for (int i = 0; i < nr; i++) { struct folio *folio = page_folio(encoded_page_ptr(pages[i])); free_swap_cache(folio); refs[folios.nr] = 1; if (unlikely(encoded_page_flags(pages[i]) & ENCODED_PAGE_BIT_NR_PAGES_NEXT)) refs[folios.nr] = encoded_nr_pages(pages[++i]); if (folio_batch_add(&folios, folio) == 0) folios_put_refs(&folios, refs); } if (folios.nr) folios_put_refs(&folios, refs); } static inline bool swap_use_vma_readahead(void) { return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap); } /** * swap_update_readahead - Update the readahead statistics of VMA or globally. * @folio: the swap cache folio that just got hit. * @vma: the VMA that should be updated, could be NULL for global update. * @addr: the addr that triggered the swapin, ignored if @vma is NULL. */ void swap_update_readahead(struct folio *folio, struct vm_area_struct *vma, unsigned long addr) { bool readahead, vma_ra = swap_use_vma_readahead(); /* * At the moment, we don't support PG_readahead for anon THP * so let's bail out rather than confusing the readahead stat. */ if (unlikely(folio_test_large(folio))) return; readahead = folio_test_clear_readahead(folio); if (vma && vma_ra) { unsigned long ra_val; int win, hits; ra_val = GET_SWAP_RA_VAL(vma); win = SWAP_RA_WIN(ra_val); hits = SWAP_RA_HITS(ra_val); if (readahead) hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX); atomic_long_set(&vma->swap_readahead_info, SWAP_RA_VAL(addr, win, hits)); } if (readahead) { count_vm_event(SWAP_RA_HIT); if (!vma || !vma_ra) atomic_inc(&swapin_readahead_hits); } } /** * __swap_cache_prepare_and_add - Prepare the folio and add it to swap cache. * @entry: swap entry to be bound to the folio. * @folio: folio to be added. * @gfp: memory allocation flags for charge, can be 0 if @charged if true. * @charged: if the folio is already charged. * * Update the swap_map and add folio as swap cache, typically before swapin. * All swap slots covered by the folio must have a non-zero swap count. * * Context: Caller must protect the swap device with reference count or locks. * Return: Returns the folio being added on success. Returns the existing folio * if @entry is already cached. Returns NULL if raced with swapin or swapoff. */ static struct folio *__swap_cache_prepare_and_add(swp_entry_t entry, struct folio *folio, gfp_t gfp, bool charged) { struct folio *swapcache = NULL; void *shadow; int ret; __folio_set_locked(folio); __folio_set_swapbacked(folio); for (;;) { ret = swap_cache_add_folio(folio, entry, &shadow); if (!ret) break; /* * Large order allocation needs special handling on * race: if a smaller folio exists in cache, swapin needs * to fallback to order 0, and doing a swap cache lookup * might return a folio that is irrelevant to the faulting * entry because @entry is aligned down. Just return NULL. */ if (ret != -EEXIST || folio_test_large(folio)) goto failed; swapcache = swap_cache_get_folio(entry); if (swapcache) goto failed; } if (!charged && mem_cgroup_swapin_charge_folio(folio, NULL, gfp, entry)) { swap_cache_del_folio(folio); goto failed; } memcg1_swapin(entry, folio_nr_pages(folio)); if (shadow) workingset_refault(folio, shadow); /* Caller will initiate read into locked folio */ folio_add_lru(folio); return folio; failed: folio_unlock(folio); return swapcache; } /** * swap_cache_alloc_folio - Allocate folio for swapped out slot in swap cache. * @entry: the swapped out swap entry to be binded to the folio. * @gfp_mask: memory allocation flags * @mpol: NUMA memory allocation policy to be applied * @ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE * @new_page_allocated: sets true if allocation happened, false otherwise * * Allocate a folio in the swap cache for one swap slot, typically before * doing IO (e.g. swap in or zswap writeback). The swap slot indicated by * @entry must have a non-zero swap count (swapped out). * Currently only supports order 0. * * Context: Caller must protect the swap device with reference count or locks. * Return: Returns the existing folio if @entry is cached already. Returns * NULL if failed due to -ENOMEM or @entry have a swap count < 1. */ struct folio *swap_cache_alloc_folio(swp_entry_t entry, gfp_t gfp_mask, struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated) { struct swap_info_struct *si = __swap_entry_to_info(entry); struct folio *folio; struct folio *result = NULL; *new_page_allocated = false; /* Check the swap cache again for readahead path. */ folio = swap_cache_get_folio(entry); if (folio) return folio; /* Skip allocation for unused and bad swap slot for readahead. */ if (!swap_entry_swapped(si, entry)) return NULL; /* Allocate a new folio to be added into the swap cache. */ folio = folio_alloc_mpol(gfp_mask, 0, mpol, ilx, numa_node_id()); if (!folio) return NULL; /* Try add the new folio, returns existing folio or NULL on failure. */ result = __swap_cache_prepare_and_add(entry, folio, gfp_mask, false); if (result == folio) *new_page_allocated = true; else folio_put(folio); return result; } /** * swapin_folio - swap-in one or multiple entries skipping readahead. * @entry: starting swap entry to swap in * @folio: a new allocated and charged folio * * Reads @entry into @folio, @folio will be added to the swap cache. * If @folio is a large folio, the @entry will be rounded down to align * with the folio size. * * Return: returns pointer to @folio on success. If folio is a large folio * and this raced with another swapin, NULL will be returned to allow fallback * to order 0. Else, if another folio was already added to the swap cache, * return that swap cache folio instead. */ struct folio *swapin_folio(swp_entry_t entry, struct folio *folio) { struct folio *swapcache; pgoff_t offset = swp_offset(entry); unsigned long nr_pages = folio_nr_pages(folio); entry = swp_entry(swp_type(entry), round_down(offset, nr_pages)); swapcache = __swap_cache_prepare_and_add(entry, folio, 0, true); if (swapcache == folio) swap_read_folio(folio, NULL); return swapcache; } /* * Locate a page of swap in physical memory, reserving swap cache space * and reading the disk if it is not already cached. * A failure return means that either the page allocation failed or that * the swap entry is no longer in use. */ struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, struct vm_area_struct *vma, unsigned long addr, struct swap_iocb **plug) { struct swap_info_struct *si; bool page_allocated; struct mempolicy *mpol; pgoff_t ilx; struct folio *folio; si = get_swap_device(entry); if (!si) return NULL; mpol = get_vma_policy(vma, addr, 0, &ilx); folio = swap_cache_alloc_folio(entry, gfp_mask, mpol, ilx, &page_allocated); mpol_cond_put(mpol); if (page_allocated) swap_read_folio(folio, plug); put_swap_device(si); return folio; } static unsigned int __swapin_nr_pages(unsigned long prev_offset, unsigned long offset, int hits, int max_pages, int prev_win) { unsigned int pages, last_ra; /* * This heuristic has been found to work well on both sequential and * random loads, swapping to hard disk or to SSD: please don't ask * what the "+ 2" means, it just happens to work well, that's all. */ pages = hits + 2; if (pages == 2) { /* * We can have no readahead hits to judge by: but must not get * stuck here forever, so check for an adjacent offset instead * (and don't even bother to check whether swap type is same). */ if (offset != prev_offset + 1 && offset != prev_offset - 1) pages = 1; } else { unsigned int roundup = 4; while (roundup < pages) roundup <<= 1; pages = roundup; } if (pages > max_pages) pages = max_pages; /* Don't shrink readahead too fast */ last_ra = prev_win / 2; if (pages < last_ra) pages = last_ra; return pages; } static unsigned long swapin_nr_pages(unsigned long offset) { static unsigned long prev_offset; unsigned int hits, pages, max_pages; static atomic_t last_readahead_pages; max_pages = 1 << READ_ONCE(page_cluster); if (max_pages <= 1) return 1; hits = atomic_xchg(&swapin_readahead_hits, 0); pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits, max_pages, atomic_read(&last_readahead_pages)); if (!hits) WRITE_ONCE(prev_offset, offset); atomic_set(&last_readahead_pages, pages); return pages; } /** * swap_cluster_readahead - swap in pages in hope we need them soon * @entry: swap entry of this memory * @gfp_mask: memory allocation flags * @mpol: NUMA memory allocation policy to be applied * @ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE * * Returns the struct folio for entry and addr, after queueing swapin. * * Primitive swap readahead code. We simply read an aligned block of * (1 << page_cluster) entries in the swap area. This method is chosen * because it doesn't cost us any seek time. We also make sure to queue * the 'original' request together with the readahead ones... * * Note: it is intentional that the same NUMA policy and interleave index * are used for every page of the readahead: neighbouring pages on swap * are fairly likely to have been swapped out from the same node. */ struct folio *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, struct mempolicy *mpol, pgoff_t ilx) { struct folio *folio; unsigned long entry_offset = swp_offset(entry); unsigned long offset = entry_offset; unsigned long start_offset, end_offset; unsigned long mask; struct swap_info_struct *si = __swap_entry_to_info(entry); struct blk_plug plug; struct swap_iocb *splug = NULL; bool page_allocated; mask = swapin_nr_pages(offset) - 1; if (!mask) goto skip; /* Read a page_cluster sized and aligned cluster around offset. */ start_offset = offset & ~mask; end_offset = offset | mask; if (!start_offset) /* First page is swap header. */ start_offset++; if (end_offset >= si->max) end_offset = si->max - 1; blk_start_plug(&plug); for (offset = start_offset; offset <= end_offset ; offset++) { /* Ok, do the async read-ahead now */ folio = swap_cache_alloc_folio( swp_entry(swp_type(entry), offset), gfp_mask, mpol, ilx, &page_allocated); if (!folio) continue; if (page_allocated) { swap_read_folio(folio, &splug); if (offset != entry_offset) { folio_set_readahead(folio); count_vm_event(SWAP_RA); } } folio_put(folio); } blk_finish_plug(&plug); swap_read_unplug(splug); lru_add_drain(); /* Push any new pages onto the LRU now */ skip: /* The page was likely read above, so no need for plugging here */ folio = swap_cache_alloc_folio(entry, gfp_mask, mpol, ilx, &page_allocated); if (unlikely(page_allocated)) swap_read_folio(folio, NULL); return folio; } static int swap_vma_ra_win(struct vm_fault *vmf, unsigned long *start, unsigned long *end) { struct vm_area_struct *vma = vmf->vma; unsigned long ra_val; unsigned long faddr, prev_faddr, left, right; unsigned int max_win, hits, prev_win, win; max_win = 1 << min(READ_ONCE(page_cluster), SWAP_RA_ORDER_CEILING); if (max_win == 1) return 1; faddr = vmf->address; ra_val = GET_SWAP_RA_VAL(vma); prev_faddr = SWAP_RA_ADDR(ra_val); prev_win = SWAP_RA_WIN(ra_val); hits = SWAP_RA_HITS(ra_val); win = __swapin_nr_pages(PFN_DOWN(prev_faddr), PFN_DOWN(faddr), hits, max_win, prev_win); atomic_long_set(&vma->swap_readahead_info, SWAP_RA_VAL(faddr, win, 0)); if (win == 1) return 1; if (faddr == prev_faddr + PAGE_SIZE) left = faddr; else if (prev_faddr == faddr + PAGE_SIZE) left = faddr - (win << PAGE_SHIFT) + PAGE_SIZE; else left = faddr - (((win - 1) / 2) << PAGE_SHIFT); right = left + (win << PAGE_SHIFT); if ((long)left < 0) left = 0; *start = max3(left, vma->vm_start, faddr & PMD_MASK); *end = min3(right, vma->vm_end, (faddr & PMD_MASK) + PMD_SIZE); return win; } /** * swap_vma_readahead - swap in pages in hope we need them soon * @targ_entry: swap entry of the targeted memory * @gfp_mask: memory allocation flags * @mpol: NUMA memory allocation policy to be applied * @targ_ilx: NUMA interleave index, for use only when MPOL_INTERLEAVE * @vmf: fault information * * Returns the struct folio for entry and addr, after queueing swapin. * * Primitive swap readahead code. We simply read in a few pages whose * virtual addresses are around the fault address in the same vma. * * Caller must hold read mmap_lock if vmf->vma is not NULL. * */ static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask, struct mempolicy *mpol, pgoff_t targ_ilx, struct vm_fault *vmf) { struct blk_plug plug; struct swap_iocb *splug = NULL; struct folio *folio; pte_t *pte = NULL, pentry; int win; unsigned long start, end, addr; pgoff_t ilx; bool page_allocated; win = swap_vma_ra_win(vmf, &start, &end); if (win == 1) goto skip; ilx = targ_ilx - PFN_DOWN(vmf->address - start); blk_start_plug(&plug); for (addr = start; addr < end; ilx++, addr += PAGE_SIZE) { struct swap_info_struct *si = NULL; softleaf_t entry; if (!pte++) { pte = pte_offset_map(vmf->pmd, addr); if (!pte) break; } pentry = ptep_get_lockless(pte); entry = softleaf_from_pte(pentry); if (!softleaf_is_swap(entry)) continue; pte_unmap(pte); pte = NULL; /* * Readahead entry may come from a device that we are not * holding a reference to, try to grab a reference, or skip. */ if (swp_type(entry) != swp_type(targ_entry)) { si = get_swap_device(entry); if (!si) continue; } folio = swap_cache_alloc_folio(entry, gfp_mask, mpol, ilx, &page_allocated); if (si) put_swap_device(si); if (!folio) continue; if (page_allocated) { swap_read_folio(folio, &splug); if (addr != vmf->address) { folio_set_readahead(folio); count_vm_event(SWAP_RA); } } folio_put(folio); } if (pte) pte_unmap(pte); blk_finish_plug(&plug); swap_read_unplug(splug); lru_add_drain(); skip: /* The folio was likely read above, so no need for plugging here */ folio = swap_cache_alloc_folio(targ_entry, gfp_mask, mpol, targ_ilx, &page_allocated); if (unlikely(page_allocated)) swap_read_folio(folio, NULL); return folio; } /** * swapin_readahead - swap in pages in hope we need them soon * @entry: swap entry of this memory * @gfp_mask: memory allocation flags * @vmf: fault information * * Returns the struct folio for entry and addr, after queueing swapin. * * It's a main entry function for swap readahead. By the configuration, * it will read ahead blocks by cluster-based(ie, physical disk based) * or vma-based(ie, virtual address based on faulty address) readahead. */ struct folio *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, struct vm_fault *vmf) { struct mempolicy *mpol; pgoff_t ilx; struct folio *folio; mpol = get_vma_policy(vmf->vma, vmf->address, 0, &ilx); folio = swap_use_vma_readahead() ? swap_vma_readahead(entry, gfp_mask, mpol, ilx, vmf) : swap_cluster_readahead(entry, gfp_mask, mpol, ilx); mpol_cond_put(mpol); return folio; } #ifdef CONFIG_SYSFS static ssize_t vma_ra_enabled_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sysfs_emit(buf, "%s\n", str_true_false(enable_vma_readahead)); } static ssize_t vma_ra_enabled_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { ssize_t ret; ret = kstrtobool(buf, &enable_vma_readahead); if (ret) return ret; return count; } static struct kobj_attribute vma_ra_enabled_attr = __ATTR_RW(vma_ra_enabled); static struct attribute *swap_attrs[] = { &vma_ra_enabled_attr.attr, NULL, }; static const struct attribute_group swap_attr_group = { .attrs = swap_attrs, }; static int __init swap_init(void) { int err; struct kobject *swap_kobj; swap_kobj = kobject_create_and_add("swap", mm_kobj); if (!swap_kobj) { pr_err("failed to create swap kobject\n"); return -ENOMEM; } err = sysfs_create_group(swap_kobj, &swap_attr_group); if (err) { pr_err("failed to register swap group\n"); goto delete_obj; } /* Swap cache writeback is LRU based, no tags for it */ mapping_set_no_writeback_tags(&swap_space); return 0; delete_obj: kobject_put(swap_kobj); return err; } subsys_initcall(swap_init); #endif