| /* |
| * 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/module.h> |
| #include <linux/mm.h> |
| #include <linux/kernel_stat.h> |
| #include <linux/swap.h> |
| #include <linux/swapops.h> |
| #include <linux/init.h> |
| #include <linux/pagemap.h> |
| #include <linux/buffer_head.h> |
| #include <linux/backing-dev.h> |
| #include <linux/pagevec.h> |
| #include <linux/migrate.h> |
| |
| #include <asm/pgtable.h> |
| |
| /* |
| * swapper_space is a fiction, retained to simplify the path through |
| * vmscan's shrink_page_list, to make sync_page look nicer, and to allow |
| * future use of radix_tree tags in the swap cache. |
| */ |
| static const struct address_space_operations swap_aops = { |
| .writepage = swap_writepage, |
| .sync_page = block_sync_page, |
| .set_page_dirty = __set_page_dirty_nobuffers, |
| .migratepage = migrate_page, |
| }; |
| |
| static struct backing_dev_info swap_backing_dev_info = { |
| .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK, |
| .unplug_io_fn = swap_unplug_io_fn, |
| }; |
| |
| struct address_space swapper_space = { |
| .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN), |
| .tree_lock = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock), |
| .a_ops = &swap_aops, |
| .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear), |
| .backing_dev_info = &swap_backing_dev_info, |
| }; |
| |
| #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) |
| |
| static struct { |
| unsigned long add_total; |
| unsigned long del_total; |
| unsigned long find_success; |
| unsigned long find_total; |
| } swap_cache_info; |
| |
| 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", 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_mask) |
| { |
| int error; |
| |
| BUG_ON(!PageLocked(page)); |
| BUG_ON(PageSwapCache(page)); |
| BUG_ON(PagePrivate(page)); |
| BUG_ON(!PageSwapBacked(page)); |
| error = radix_tree_preload(gfp_mask); |
| if (!error) { |
| page_cache_get(page); |
| SetPageSwapCache(page); |
| set_page_private(page, entry.val); |
| |
| spin_lock_irq(&swapper_space.tree_lock); |
| error = radix_tree_insert(&swapper_space.page_tree, |
| entry.val, page); |
| if (likely(!error)) { |
| total_swapcache_pages++; |
| __inc_zone_page_state(page, NR_FILE_PAGES); |
| INC_CACHE_INFO(add_total); |
| } |
| spin_unlock_irq(&swapper_space.tree_lock); |
| radix_tree_preload_end(); |
| |
| if (unlikely(error)) { |
| set_page_private(page, 0UL); |
| ClearPageSwapCache(page); |
| page_cache_release(page); |
| } |
| } |
| 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) |
| { |
| BUG_ON(!PageLocked(page)); |
| BUG_ON(!PageSwapCache(page)); |
| BUG_ON(PageWriteback(page)); |
| BUG_ON(PagePrivate(page)); |
| |
| radix_tree_delete(&swapper_space.page_tree, page_private(page)); |
| set_page_private(page, 0); |
| ClearPageSwapCache(page); |
| total_swapcache_pages--; |
| __dec_zone_page_state(page, NR_FILE_PAGES); |
| INC_CACHE_INFO(del_total); |
| } |
| |
| /** |
| * add_to_swap - allocate swap space for a page |
| * @page: page we want to move to swap |
| * @gfp_mask: memory allocation flags |
| * |
| * 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, gfp_t gfp_mask) |
| { |
| swp_entry_t entry; |
| int err; |
| |
| BUG_ON(!PageLocked(page)); |
| BUG_ON(!PageUptodate(page)); |
| |
| for (;;) { |
| entry = get_swap_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 and mark it dirty |
| */ |
| err = add_to_swap_cache(page, entry, |
| gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN); |
| |
| switch (err) { |
| case 0: /* Success */ |
| SetPageDirty(page); |
| return 1; |
| case -EEXIST: |
| /* Raced with "speculative" read_swap_cache_async */ |
| swap_free(entry); |
| continue; |
| default: |
| /* -ENOMEM radix-tree allocation failure */ |
| swap_free(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; |
| |
| entry.val = page_private(page); |
| |
| spin_lock_irq(&swapper_space.tree_lock); |
| __delete_from_swap_cache(page); |
| spin_unlock_irq(&swapper_space.tree_lock); |
| |
| swap_free(entry); |
| page_cache_release(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 |
| * exclusive_swap_page() _with_ the lock. |
| * - Marcelo |
| */ |
| static inline void free_swap_cache(struct page *page) |
| { |
| if (PageSwapCache(page) && trylock_page(page)) { |
| remove_exclusive_swap_page(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); |
| page_cache_release(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; |
| |
| lru_add_drain(); |
| while (nr) { |
| int todo = min(nr, PAGEVEC_SIZE); |
| int i; |
| |
| for (i = 0; i < todo; i++) |
| free_swap_cache(pagep[i]); |
| release_pages(pagep, todo, 0); |
| pagep += todo; |
| nr -= todo; |
| } |
| } |
| |
| /* |
| * 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 page *page; |
| |
| page = find_get_page(&swapper_space, entry.val); |
| |
| if (page) |
| INC_CACHE_INFO(find_success); |
| |
| INC_CACHE_INFO(find_total); |
| return 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) |
| { |
| struct page *found_page, *new_page = NULL; |
| int err; |
| |
| 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, entry.val); |
| if (found_page) |
| 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. |
| */ |
| if (!swap_duplicate(entry)) |
| break; |
| |
| /* |
| * Associate the page with swap entry in the swap cache. |
| * May fail (-EEXIST) if there is already a page associated |
| * with this entry in the swap cache: added by a racing |
| * read_swap_cache_async, or add_to_swap or shmem_writepage |
| * re-using the just freed swap entry for an existing page. |
| * May fail (-ENOMEM) if radix-tree node allocation failed. |
| */ |
| set_page_locked(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 and return. |
| */ |
| lru_cache_add_active(new_page); |
| swap_readpage(NULL, new_page); |
| return new_page; |
| } |
| ClearPageSwapBacked(new_page); |
| clear_page_locked(new_page); |
| swap_free(entry); |
| } while (err != -ENOMEM); |
| |
| if (new_page) |
| page_cache_release(new_page); |
| return found_page; |
| } |
| |
| /** |
| * swapin_readahead - swap in pages in hope we need them soon |
| * @entry: swap entry of this memory |
| * @gfp_mask: memory allocation flags |
| * @vma: user vma this address belongs to |
| * @addr: target address for mempolicy |
| * |
| * 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 vma is not NULL. |
| */ |
| struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
| struct vm_area_struct *vma, unsigned long addr) |
| { |
| int nr_pages; |
| struct page *page; |
| unsigned long offset; |
| unsigned long end_offset; |
| |
| /* |
| * Get starting offset for readaround, and number of pages to read. |
| * Adjust starting address by readbehind (for NUMA interleave case)? |
| * No, it's very unlikely that swap layout would follow vma layout, |
| * more likely that neighbouring swap pages came from the same node: |
| * so use the same "addr" to choose the same node for each swap read. |
| */ |
| nr_pages = valid_swaphandles(entry, &offset); |
| for (end_offset = offset + nr_pages; 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); |
| if (!page) |
| break; |
| page_cache_release(page); |
| } |
| lru_add_drain(); /* Push any new pages onto the LRU now */ |
| return read_swap_cache_async(entry, gfp_mask, vma, addr); |
| } |