diff options
Diffstat (limited to 'mm/swap_state.c')
-rw-r--r-- | mm/swap_state.c | 855 |
1 files changed, 855 insertions, 0 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c new file mode 100644 index 000000000..3febffe0f --- /dev/null +++ b/mm/swap_state.c @@ -0,0 +1,855 @@ +// 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> +#include "internal.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; + + rcu_read_lock(); + for (i = 0; i < MAX_SWAPFILES; i++) { + /* + * The corresponding entries in nr_swapper_spaces and + * swapper_spaces will be reused only after at least + * one grace period. So it is impossible for them + * belongs to different usage. + */ + nr = nr_swapper_spaces[i]; + spaces = rcu_dereference(swapper_spaces[i]); + if (!nr || !spaces) + continue; + for (j = 0; j < nr; j++) + ret += spaces[j].nrpages; + } + rcu_read_unlock(); + 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) +{ + int error, i, nr = hpage_nr_pages(page); + struct address_space *address_space; + pgoff_t idx = swp_offset(entry); + + 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); + + address_space = swap_address_space(entry); + xa_lock_irq(&address_space->i_pages); + for (i = 0; i < nr; i++) { + set_page_private(page + i, entry.val + i); + error = radix_tree_insert(&address_space->i_pages, + idx + i, page + i); + if (unlikely(error)) + break; + } + if (likely(!error)) { + address_space->nrpages += nr; + __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr); + ADD_CACHE_INFO(add_total, nr); + } else { + /* + * Only the context which have set SWAP_HAS_CACHE flag + * would call add_to_swap_cache(). + * So add_to_swap_cache() doesn't returns -EEXIST. + */ + VM_BUG_ON(error == -EEXIST); + set_page_private(page + i, 0UL); + while (i--) { + radix_tree_delete(&address_space->i_pages, idx + i); + set_page_private(page + i, 0UL); + } + ClearPageSwapCache(page); + page_ref_sub(page, nr); + } + xa_unlock_irq(&address_space->i_pages); + + return error; +} + + +int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) +{ + int error; + + error = radix_tree_maybe_preload_order(gfp_mask, compound_order(page)); + if (!error) { + error = __add_to_swap_cache(page, entry); + radix_tree_preload_end(); + } + return error; +} + +/* + * 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) +{ + struct address_space *address_space; + int i, nr = hpage_nr_pages(page); + swp_entry_t entry; + pgoff_t idx; + + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(!PageSwapCache(page), page); + VM_BUG_ON_PAGE(PageWriteback(page), page); + + entry.val = page_private(page); + address_space = swap_address_space(entry); + idx = swp_offset(entry); + for (i = 0; i < nr; i++) { + radix_tree_delete(&address_space->i_pages, idx + i); + set_page_private(page + i, 0); + } + 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; + + /* + * Radix-tree 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); + /* -ENOMEM radix-tree allocation failure */ + 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; + struct address_space *address_space; + + entry.val = page_private(page); + + address_space = swap_address_space(entry); + xa_lock_irq(&address_space->i_pages); + __delete_from_swap_cache(page); + 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; + + page = find_get_page(swap_address_space(entry), swp_offset(entry)); + + 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, *new_page = NULL; + struct address_space *swapper_space = swap_address_space(entry); + 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. + */ + found_page = find_get_page(swapper_space, swp_offset(entry)); + 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 */ + } + + /* + * call radix_tree_preload() while we can wait. + */ + err = radix_tree_maybe_preload(gfp_mask & GFP_RECLAIM_MASK); + if (err) + break; + + /* + * Swap entry may have been freed since our caller observed it. + */ + err = swapcache_prepare(entry); + if (err == -EEXIST) { + radix_tree_preload_end(); + /* + * 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; + } + if (err) { /* swp entry is obsolete ? */ + radix_tree_preload_end(); + break; + } + + /* May fail (-ENOMEM) if radix-tree node allocation failed. */ + __SetPageLocked(new_page); + __SetPageSwapBacked(new_page); + err = __add_to_swap_cache(new_page, entry); + if (likely(!err)) { + radix_tree_preload_end(); + /* + * Initiate read into locked page and return. + */ + lru_cache_add_anon(new_page); + *new_page_allocated = true; + return new_page; + } + radix_tree_preload_end(); + __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 down_read on the vma->vm_mm 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; + + 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; + INIT_RADIX_TREE(&space->i_pages, GFP_ATOMIC|__GFP_NOWARN); + 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; + rcu_assign_pointer(swapper_spaces[type], spaces); + + return 0; +} + +void exit_swap_address_space(unsigned int type) +{ + struct address_space *spaces; + + spaces = swapper_spaces[type]; + nr_swapper_spaces[type] = 0; + rcu_assign_pointer(swapper_spaces[type], NULL); + synchronize_rcu(); + kvfree(spaces); +} + +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); +} + +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 |