| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * linux/mm/swap_state.c |
| * |
| * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
| * Swap reorganised 29.12.95, Stephen Tweedie |
| * |
| * Rewritten to use page cache, (C) 1998 Stephen Tweedie |
| */ |
| #include <linux/mm.h> |
| #include <linux/gfp.h> |
| #include <linux/kernel_stat.h> |
| #include <linux/swap.h> |
| #include <linux/swapops.h> |
| #include <linux/init.h> |
| #include <linux/pagemap.h> |
| #include <linux/backing-dev.h> |
| #include <linux/blkdev.h> |
| #include <linux/pagevec.h> |
| #include <linux/migrate.h> |
| #include <linux/vmalloc.h> |
| #include <linux/swap_slots.h> |
| #include <linux/huge_mm.h> |
| |
| #include <asm/pgtable.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, |
| .set_page_dirty = swap_set_page_dirty, |
| #ifdef CONFIG_MIGRATION |
| .migratepage = migrate_page, |
| #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) |
| |
| #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) |
| #define ADD_CACHE_INFO(x, nr) do { swap_cache_info.x += (nr); } while (0) |
| |
| static struct { |
| unsigned long add_total; |
| unsigned long del_total; |
| unsigned long find_success; |
| unsigned long find_total; |
| } swap_cache_info; |
| |
| unsigned long total_swapcache_pages(void) |
| { |
| unsigned int i, j, nr; |
| unsigned long ret = 0; |
| struct address_space *spaces; |
| struct swap_info_struct *si; |
| |
| for (i = 0; i < MAX_SWAPFILES; i++) { |
| swp_entry_t entry = swp_entry(i, 1); |
| |
| /* Avoid get_swap_device() to warn for bad swap entry */ |
| if (!swp_swap_info(entry)) |
| continue; |
| /* Prevent swapoff to free swapper_spaces */ |
| si = get_swap_device(entry); |
| if (!si) |
| continue; |
| nr = nr_swapper_spaces[i]; |
| spaces = swapper_spaces[i]; |
| for (j = 0; j < nr; j++) |
| ret += spaces[j].nrpages; |
| put_swap_device(si); |
| } |
| return ret; |
| } |
| |
| 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("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n", |
| swap_cache_info.add_total, swap_cache_info.del_total, |
| swap_cache_info.find_success, swap_cache_info.find_total); |
| printk("Free swap = %ldkB\n", |
| get_nr_swap_pages() << (PAGE_SHIFT - 10)); |
| printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); |
| } |
| |
| /* |
| * add_to_swap_cache resembles add_to_page_cache_locked on swapper_space, |
| * but sets SwapCache flag and private instead of mapping and index. |
| */ |
| int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp) |
| { |
| struct address_space *address_space = swap_address_space(entry); |
| pgoff_t idx = swp_offset(entry); |
| XA_STATE_ORDER(xas, &address_space->i_pages, idx, compound_order(page)); |
| unsigned long i, nr = hpage_nr_pages(page); |
| |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(PageSwapCache(page), page); |
| VM_BUG_ON_PAGE(!PageSwapBacked(page), page); |
| |
| page_ref_add(page, nr); |
| SetPageSwapCache(page); |
| |
| do { |
| xas_lock_irq(&xas); |
| xas_create_range(&xas); |
| if (xas_error(&xas)) |
| goto unlock; |
| for (i = 0; i < nr; i++) { |
| VM_BUG_ON_PAGE(xas.xa_index != idx + i, page); |
| set_page_private(page + i, entry.val + i); |
| xas_store(&xas, page); |
| xas_next(&xas); |
| } |
| address_space->nrpages += nr; |
| __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr); |
| ADD_CACHE_INFO(add_total, nr); |
| unlock: |
| xas_unlock_irq(&xas); |
| } while (xas_nomem(&xas, gfp)); |
| |
| if (!xas_error(&xas)) |
| return 0; |
| |
| ClearPageSwapCache(page); |
| page_ref_sub(page, nr); |
| return xas_error(&xas); |
| } |
| |
| /* |
| * This must be called only on pages that have |
| * been verified to be in the swap cache. |
| */ |
| void __delete_from_swap_cache(struct page *page, swp_entry_t entry) |
| { |
| struct address_space *address_space = swap_address_space(entry); |
| int i, nr = hpage_nr_pages(page); |
| pgoff_t idx = swp_offset(entry); |
| XA_STATE(xas, &address_space->i_pages, idx); |
| |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(!PageSwapCache(page), page); |
| VM_BUG_ON_PAGE(PageWriteback(page), page); |
| |
| for (i = 0; i < nr; i++) { |
| void *entry = xas_store(&xas, NULL); |
| VM_BUG_ON_PAGE(entry != page, entry); |
| set_page_private(page + i, 0); |
| xas_next(&xas); |
| } |
| ClearPageSwapCache(page); |
| address_space->nrpages -= nr; |
| __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr); |
| ADD_CACHE_INFO(del_total, nr); |
| } |
| |
| /** |
| * add_to_swap - allocate swap space for a page |
| * @page: page we want to move to swap |
| * |
| * Allocate swap space for the page and add the page to the |
| * swap cache. Caller needs to hold the page lock. |
| */ |
| int add_to_swap(struct page *page) |
| { |
| swp_entry_t entry; |
| int err; |
| |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(!PageUptodate(page), page); |
| |
| entry = get_swap_page(page); |
| if (!entry.val) |
| return 0; |
| |
| /* |
| * 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(page, entry, |
| __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); |
| if (err) |
| /* |
| * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
| * clear SWAP_HAS_CACHE flag. |
| */ |
| goto fail; |
| /* |
| * Normally the page will be dirtied in unmap because its pte should be |
| * dirty. A special case is MADV_FREE page. The page'e pte could have |
| * dirty bit cleared but the page's SwapBacked bit is still set because |
| * clearing the dirty bit and SwapBacked bit has no lock protected. For |
| * such page, unmap will not set dirty bit for it, so page reclaim will |
| * not write the page out. This can cause data corruption when the page |
| * is swap in later. Always setting the dirty bit for the page solves |
| * the problem. |
| */ |
| set_page_dirty(page); |
| |
| return 1; |
| |
| fail: |
| put_swap_page(page, entry); |
| return 0; |
| } |
| |
| /* |
| * This must be called only on pages that have |
| * been verified to be in the swap cache and locked. |
| * It will never put the page into the free list, |
| * the caller has a reference on the page. |
| */ |
| void delete_from_swap_cache(struct page *page) |
| { |
| swp_entry_t entry = { .val = page_private(page) }; |
| struct address_space *address_space = swap_address_space(entry); |
| |
| xa_lock_irq(&address_space->i_pages); |
| __delete_from_swap_cache(page, entry); |
| xa_unlock_irq(&address_space->i_pages); |
| |
| put_swap_page(page, entry); |
| page_ref_sub(page, hpage_nr_pages(page)); |
| } |
| |
| /* |
| * If we are the only user, then try to free up the swap cache. |
| * |
| * Its ok to check for PageSwapCache without the page lock |
| * here because we are going to recheck again inside |
| * try_to_free_swap() _with_ the lock. |
| * - Marcelo |
| */ |
| static inline void free_swap_cache(struct page *page) |
| { |
| if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { |
| try_to_free_swap(page); |
| unlock_page(page); |
| } |
| } |
| |
| /* |
| * 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 page **pages, int nr) |
| { |
| struct page **pagep = pages; |
| int i; |
| |
| lru_add_drain(); |
| for (i = 0; i < nr; i++) |
| free_swap_cache(pagep[i]); |
| release_pages(pagep, 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 page 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 page |
| * lock before returning. |
| */ |
| struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma, |
| unsigned long addr) |
| { |
| struct page *page; |
| struct swap_info_struct *si; |
| |
| si = get_swap_device(entry); |
| if (!si) |
| return NULL; |
| page = find_get_page(swap_address_space(entry), swp_offset(entry)); |
| put_swap_device(si); |
| |
| INC_CACHE_INFO(find_total); |
| if (page) { |
| bool vma_ra = swap_use_vma_readahead(); |
| bool readahead; |
| |
| INC_CACHE_INFO(find_success); |
| /* |
| * 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(PageTransCompound(page))) |
| return page; |
| |
| readahead = TestClearPageReadahead(page); |
| 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); |
| } |
| } |
| |
| return page; |
| } |
| |
| struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
| struct vm_area_struct *vma, unsigned long addr, |
| bool *new_page_allocated) |
| { |
| struct page *found_page = NULL, *new_page = NULL; |
| struct swap_info_struct *si; |
| int err; |
| *new_page_allocated = false; |
| |
| do { |
| /* |
| * First check the swap cache. Since this is normally |
| * called after lookup_swap_cache() failed, re-calling |
| * that would confuse statistics. |
| */ |
| si = get_swap_device(entry); |
| if (!si) |
| break; |
| found_page = find_get_page(swap_address_space(entry), |
| swp_offset(entry)); |
| put_swap_device(si); |
| if (found_page) |
| break; |
| |
| /* |
| * 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 (!__swp_swapcount(entry) && swap_slot_cache_enabled) |
| break; |
| |
| /* |
| * Get a new page to read into from swap. |
| */ |
| if (!new_page) { |
| new_page = alloc_page_vma(gfp_mask, vma, addr); |
| if (!new_page) |
| break; /* Out of memory */ |
| } |
| |
| /* |
| * Swap entry may have been freed since our caller observed it. |
| */ |
| err = swapcache_prepare(entry); |
| if (err == -EEXIST) { |
| /* |
| * We might race against get_swap_page() and stumble |
| * across a SWAP_HAS_CACHE swap_map entry whose page |
| * has not been brought into the swapcache yet. |
| */ |
| cond_resched(); |
| continue; |
| } else if (err) /* swp entry is obsolete ? */ |
| break; |
| |
| /* May fail (-ENOMEM) if XArray node allocation failed. */ |
| __SetPageLocked(new_page); |
| __SetPageSwapBacked(new_page); |
| err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL); |
| if (likely(!err)) { |
| /* Initiate read into locked page */ |
| SetPageWorkingset(new_page); |
| lru_cache_add_anon(new_page); |
| *new_page_allocated = true; |
| return new_page; |
| } |
| __ClearPageLocked(new_page); |
| /* |
| * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
| * clear SWAP_HAS_CACHE flag. |
| */ |
| put_swap_page(new_page, entry); |
| } while (err != -ENOMEM); |
| |
| if (new_page) |
| put_page(new_page); |
| return found_page; |
| } |
| |
| /* |
| * 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 page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
| struct vm_area_struct *vma, unsigned long addr, bool do_poll) |
| { |
| bool page_was_allocated; |
| struct page *retpage = __read_swap_cache_async(entry, gfp_mask, |
| vma, addr, &page_was_allocated); |
| |
| if (page_was_allocated) |
| swap_readpage(retpage, do_poll); |
| |
| return retpage; |
| } |
| |
| 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 |
| * @vmf: fault information |
| * |
| * Returns the struct page 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... |
| * |
| * This has been extended to use the NUMA policies from the mm triggering |
| * the readahead. |
| * |
| * Caller must hold read mmap_sem if vmf->vma is not NULL. |
| */ |
| struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, |
| struct vm_fault *vmf) |
| { |
| struct page *page; |
| 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; |
| bool do_poll = true, page_allocated; |
| struct vm_area_struct *vma = vmf->vma; |
| unsigned long addr = vmf->address; |
| |
| mask = swapin_nr_pages(offset) - 1; |
| if (!mask) |
| goto skip; |
| |
| /* Test swap type to make sure the dereference is safe */ |
| if (likely(si->flags & (SWP_BLKDEV | SWP_FS))) { |
| struct inode *inode = si->swap_file->f_mapping->host; |
| if (inode_read_congested(inode)) |
| goto skip; |
| } |
| |
| do_poll = false; |
| /* 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 */ |
| page = __read_swap_cache_async( |
| swp_entry(swp_type(entry), offset), |
| gfp_mask, vma, addr, &page_allocated); |
| if (!page) |
| continue; |
| if (page_allocated) { |
| swap_readpage(page, false); |
| if (offset != entry_offset) { |
| SetPageReadahead(page); |
| count_vm_event(SWAP_RA); |
| } |
| } |
| put_page(page); |
| } |
| blk_finish_plug(&plug); |
| |
| lru_add_drain(); /* Push any new pages onto the LRU now */ |
| skip: |
| return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll); |
| } |
| |
| 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) |
| { |
| kvfree(swapper_spaces[type]); |
| nr_swapper_spaces[type] = 0; |
| swapper_spaces[type] = NULL; |
| } |
| |
| static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma, |
| unsigned long faddr, |
| unsigned long lpfn, |
| unsigned long rpfn, |
| unsigned long *start, |
| unsigned long *end) |
| { |
| *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)); |
| } |
| |
| 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; |
| swp_entry_t entry; |
| unsigned long faddr, pfn, fpfn; |
| unsigned long start, end; |
| pte_t *pte, *orig_pte; |
| unsigned int max_win, hits, prev_win, win, left; |
| #ifndef CONFIG_64BIT |
| pte_t *tpte; |
| #endif |
| |
| 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; |
| orig_pte = pte = pte_offset_map(vmf->pmd, faddr); |
| entry = pte_to_swp_entry(*pte); |
| if ((unlikely(non_swap_entry(entry)))) { |
| pte_unmap(orig_pte); |
| return; |
| } |
| |
| 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) { |
| pte_unmap(orig_pte); |
| return; |
| } |
| |
| /* Copy the PTEs because the page table may be unmapped */ |
| if (fpfn == pfn + 1) |
| swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end); |
| else if (pfn == fpfn + 1) |
| swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1, |
| &start, &end); |
| else { |
| left = (win - 1) / 2; |
| swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left, |
| &start, &end); |
| } |
| ra_info->nr_pte = end - start; |
| ra_info->offset = fpfn - start; |
| pte -= ra_info->offset; |
| #ifdef CONFIG_64BIT |
| ra_info->ptes = pte; |
| #else |
| tpte = ra_info->ptes; |
| for (pfn = start; pfn != end; pfn++) |
| *tpte++ = *pte++; |
| #endif |
| pte_unmap(orig_pte); |
| } |
| |
| /** |
| * swap_vma_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. |
| * |
| * Primitive swap readahead code. We simply read in a few pages whoes |
| * virtual addresses are around the fault address in the same vma. |
| * |
| * Caller must hold read mmap_sem if vmf->vma is not NULL. |
| * |
| */ |
| static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask, |
| struct vm_fault *vmf) |
| { |
| struct blk_plug plug; |
| struct vm_area_struct *vma = vmf->vma; |
| struct page *page; |
| pte_t *pte, pentry; |
| swp_entry_t entry; |
| unsigned int i; |
| bool page_allocated; |
| struct vma_swap_readahead ra_info = {0,}; |
| |
| swap_ra_info(vmf, &ra_info); |
| if (ra_info.win == 1) |
| goto skip; |
| |
| blk_start_plug(&plug); |
| for (i = 0, pte = ra_info.ptes; i < ra_info.nr_pte; |
| i++, pte++) { |
| pentry = *pte; |
| if (pte_none(pentry)) |
| continue; |
| if (pte_present(pentry)) |
| continue; |
| entry = pte_to_swp_entry(pentry); |
| if (unlikely(non_swap_entry(entry))) |
| continue; |
| page = __read_swap_cache_async(entry, gfp_mask, vma, |
| vmf->address, &page_allocated); |
| if (!page) |
| continue; |
| if (page_allocated) { |
| swap_readpage(page, false); |
| if (i != ra_info.offset) { |
| SetPageReadahead(page); |
| count_vm_event(SWAP_RA); |
| } |
| } |
| put_page(page); |
| } |
| blk_finish_plug(&plug); |
| lru_add_drain(); |
| skip: |
| return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address, |
| ra_info.win == 1); |
| } |
| |
| /** |
| * 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) |
| { |
| return swap_use_vma_readahead() ? |
| swap_vma_readahead(entry, gfp_mask, vmf) : |
| swap_cluster_readahead(entry, gfp_mask, vmf); |
| } |
| |
| #ifdef CONFIG_SYSFS |
| static ssize_t vma_ra_enabled_show(struct kobject *kobj, |
| struct kobj_attribute *attr, char *buf) |
| { |
| return sprintf(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) |
| { |
| if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1)) |
| enable_vma_readahead = true; |
| else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1)) |
| enable_vma_readahead = false; |
| else |
| return -EINVAL; |
| |
| return count; |
| } |
| static struct kobj_attribute vma_ra_enabled_attr = |
| __ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show, |
| vma_ra_enabled_store); |
| |
| static struct attribute *swap_attrs[] = { |
| &vma_ra_enabled_attr.attr, |
| NULL, |
| }; |
| |
| static 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 |