swap_state.rar_swap

/* * 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 <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 }; static struct backing_dev_info swap_backing_dev_info = { .name = "swap", .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED, }; struct address_space swapper_spaces[MAX_SWAPFILES] = { [0 ... MAX_SWAPFILES - 1] = { .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN), .i_mmap_writable = ATOMIC_INIT(0), .a_ops = &swap_aops, .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; unsigned long total_swapcache_pages(void) { int i; unsigned long ret = 0; for (i = 0; i < MAX_SWAPFILES; i++) ret += swapper_spaces[i].nrpages; 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; struct address_space *address_space; VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(PageSwapCache(page), page); VM_BUG_ON_PAGE(!PageSwapBacked(page), page); page_cache_get(page); SetPageSwapCache(page); set_page_private(page, entry.val); address_space = swap_address_space(entry); spin_lock_irq(&address_space->tree_lock); error = radix_tree_insert(&address_space->page_tree, entry.val, page); if (likely(!error)) { address_space->nrpages++; __inc_zone_page_state(page, NR_FILE_PAGES); INC_CACHE_INFO(add_total); } spin_unlock_irq(&address_space->tree_lock); if (unlikely(error)) { /* * 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, 0UL); ClearPageSwapCache(page); page_cache_release(page); } 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(gfp_mask); 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) { swp_entry_t entry; struct address_space *address_space; 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); radix_tree_delete(&address_space->page_tree, page_private(page)); set_page_private(page, 0); ClearPageSwapCache(page); address_space->nrpages--; __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 * * 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, struct list_head *list) { swp_entry_t entry; int err; VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageUptodate(page), page); entry = get_swap_page(); if (!entry.val) return 0; if (unlikely(PageTransHuge(page))) if (unlikely(split_huge_page_to_list(page, list))) { swapcache_free(entry); 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_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); if (!err) { /* Success */ SetPageDirty(page); return 1; } else { /* -ENOMEM radix-tree allocation failure */ /* * add_to_swap_cache() doesn't return -EEXIST, so we can safely * clear SWAP_HAS_CACHE flag. */ swapcache_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; struct address_space *address_space; entry.val = page_private(page); address_space = swap_address_space(entry); spin_lock_irq(&address_space->tree_lock); __delete_from_swap_cache(page); spin_unlock_irq(&address_space->tree_lock); swapcache_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 * 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); 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; int i; lru_add_drain(); for (i = 0; i < nr; i++) free_swap_cache(pagep[i]); release_pages(pagep, nr, false); } /* * 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(swap_address_space(entry), entry.val); if (page) { INC_CACHE_INFO(find_success); if (TestClearPageReadahead(page)) atomic_inc(&swapin_readahead_hits); } 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