Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * linux/mm/swap_state.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
| 5 | * Swap reorganised 29.12.95, Stephen Tweedie |
| 6 | * |
| 7 | * Rewritten to use page cache, (C) 1998 Stephen Tweedie |
| 8 | */ |
| 9 | #include <linux/module.h> |
| 10 | #include <linux/mm.h> |
| 11 | #include <linux/kernel_stat.h> |
| 12 | #include <linux/swap.h> |
Hugh Dickins | 46017e9 | 2008-02-04 22:28:41 -0800 | [diff] [blame] | 13 | #include <linux/swapops.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 14 | #include <linux/init.h> |
| 15 | #include <linux/pagemap.h> |
| 16 | #include <linux/buffer_head.h> |
| 17 | #include <linux/backing-dev.h> |
Hugh Dickins | c484d41 | 2006-01-06 00:10:55 -0800 | [diff] [blame] | 18 | #include <linux/pagevec.h> |
Christoph Lameter | b20a350 | 2006-03-22 00:09:12 -0800 | [diff] [blame] | 19 | #include <linux/migrate.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 20 | |
| 21 | #include <asm/pgtable.h> |
| 22 | |
| 23 | /* |
| 24 | * swapper_space is a fiction, retained to simplify the path through |
Anderson Briglia | 2706a1b | 2007-07-15 23:38:09 -0700 | [diff] [blame] | 25 | * vmscan's shrink_page_list, to make sync_page look nicer, and to allow |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 26 | * future use of radix_tree tags in the swap cache. |
| 27 | */ |
Christoph Hellwig | f5e54d6 | 2006-06-28 04:26:44 -0700 | [diff] [blame] | 28 | static const struct address_space_operations swap_aops = { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 29 | .writepage = swap_writepage, |
| 30 | .sync_page = block_sync_page, |
| 31 | .set_page_dirty = __set_page_dirty_nobuffers, |
Christoph Lameter | e965f96 | 2006-02-01 03:05:41 -0800 | [diff] [blame] | 32 | .migratepage = migrate_page, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 33 | }; |
| 34 | |
| 35 | static struct backing_dev_info swap_backing_dev_info = { |
| 36 | .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK, |
| 37 | .unplug_io_fn = swap_unplug_io_fn, |
| 38 | }; |
| 39 | |
| 40 | struct address_space swapper_space = { |
| 41 | .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN), |
Ingo Molnar | e4d9191 | 2006-07-03 00:24:34 -0700 | [diff] [blame] | 42 | .tree_lock = __RW_LOCK_UNLOCKED(swapper_space.tree_lock), |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 43 | .a_ops = &swap_aops, |
| 44 | .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear), |
| 45 | .backing_dev_info = &swap_backing_dev_info, |
| 46 | }; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 47 | |
| 48 | #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) |
| 49 | |
| 50 | static struct { |
| 51 | unsigned long add_total; |
| 52 | unsigned long del_total; |
| 53 | unsigned long find_success; |
| 54 | unsigned long find_total; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 55 | } swap_cache_info; |
| 56 | |
| 57 | void show_swap_cache_info(void) |
| 58 | { |
Hugh Dickins | bb63be0 | 2008-02-04 22:28:49 -0800 | [diff] [blame] | 59 | printk("Swap cache: add %lu, delete %lu, find %lu/%lu\n", |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 60 | swap_cache_info.add_total, swap_cache_info.del_total, |
Hugh Dickins | bb63be0 | 2008-02-04 22:28:49 -0800 | [diff] [blame] | 61 | swap_cache_info.find_success, swap_cache_info.find_total); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 62 | printk("Free swap = %lukB\n", nr_swap_pages << (PAGE_SHIFT - 10)); |
| 63 | printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); |
| 64 | } |
| 65 | |
| 66 | /* |
Hugh Dickins | f000944 | 2008-02-04 22:28:49 -0800 | [diff] [blame] | 67 | * add_to_swap_cache resembles add_to_page_cache on swapper_space, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 68 | * but sets SwapCache flag and private instead of mapping and index. |
| 69 | */ |
Hugh Dickins | 73b1262 | 2008-02-04 22:28:50 -0800 | [diff] [blame] | 70 | int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 71 | { |
| 72 | int error; |
| 73 | |
Nick Piggin | b55ed81 | 2007-10-16 01:24:42 -0700 | [diff] [blame] | 74 | BUG_ON(!PageLocked(page)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 75 | BUG_ON(PageSwapCache(page)); |
| 76 | BUG_ON(PagePrivate(page)); |
| 77 | error = radix_tree_preload(gfp_mask); |
| 78 | if (!error) { |
| 79 | write_lock_irq(&swapper_space.tree_lock); |
| 80 | error = radix_tree_insert(&swapper_space.page_tree, |
| 81 | entry.val, page); |
| 82 | if (!error) { |
| 83 | page_cache_get(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 84 | SetPageSwapCache(page); |
Hugh Dickins | 4c21e2f | 2005-10-29 18:16:40 -0700 | [diff] [blame] | 85 | set_page_private(page, entry.val); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 86 | total_swapcache_pages++; |
Christoph Lameter | 347ce43 | 2006-06-30 01:55:35 -0700 | [diff] [blame] | 87 | __inc_zone_page_state(page, NR_FILE_PAGES); |
Hugh Dickins | bb63be0 | 2008-02-04 22:28:49 -0800 | [diff] [blame] | 88 | INC_CACHE_INFO(add_total); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 89 | } |
| 90 | write_unlock_irq(&swapper_space.tree_lock); |
| 91 | radix_tree_preload_end(); |
| 92 | } |
| 93 | return error; |
| 94 | } |
| 95 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 96 | /* |
| 97 | * This must be called only on pages that have |
| 98 | * been verified to be in the swap cache. |
| 99 | */ |
| 100 | void __delete_from_swap_cache(struct page *page) |
| 101 | { |
| 102 | BUG_ON(!PageLocked(page)); |
| 103 | BUG_ON(!PageSwapCache(page)); |
| 104 | BUG_ON(PageWriteback(page)); |
Hugh Dickins | 3279ffd | 2005-09-03 15:54:43 -0700 | [diff] [blame] | 105 | BUG_ON(PagePrivate(page)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 106 | |
Hugh Dickins | 4c21e2f | 2005-10-29 18:16:40 -0700 | [diff] [blame] | 107 | radix_tree_delete(&swapper_space.page_tree, page_private(page)); |
| 108 | set_page_private(page, 0); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 109 | ClearPageSwapCache(page); |
| 110 | total_swapcache_pages--; |
Christoph Lameter | 347ce43 | 2006-06-30 01:55:35 -0700 | [diff] [blame] | 111 | __dec_zone_page_state(page, NR_FILE_PAGES); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 112 | INC_CACHE_INFO(del_total); |
| 113 | } |
| 114 | |
| 115 | /** |
| 116 | * add_to_swap - allocate swap space for a page |
| 117 | * @page: page we want to move to swap |
| 118 | * |
| 119 | * Allocate swap space for the page and add the page to the |
| 120 | * swap cache. Caller needs to hold the page lock. |
| 121 | */ |
Christoph Lameter | 1480a54 | 2006-01-08 01:00:53 -0800 | [diff] [blame] | 122 | int add_to_swap(struct page * page, gfp_t gfp_mask) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 123 | { |
| 124 | swp_entry_t entry; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 125 | int err; |
| 126 | |
Eric Sesterhenn | e74ca2b | 2006-04-01 01:25:12 +0200 | [diff] [blame] | 127 | BUG_ON(!PageLocked(page)); |
Nick Piggin | 0ed361d | 2008-02-04 22:29:34 -0800 | [diff] [blame^] | 128 | BUG_ON(!PageUptodate(page)); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 129 | |
| 130 | for (;;) { |
| 131 | entry = get_swap_page(); |
| 132 | if (!entry.val) |
| 133 | return 0; |
| 134 | |
Nick Piggin | bd53b71 | 2005-05-01 08:58:37 -0700 | [diff] [blame] | 135 | /* |
| 136 | * Radix-tree node allocations from PF_MEMALLOC contexts could |
| 137 | * completely exhaust the page allocator. __GFP_NOMEMALLOC |
| 138 | * stops emergency reserves from being allocated. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 139 | * |
Nick Piggin | bd53b71 | 2005-05-01 08:58:37 -0700 | [diff] [blame] | 140 | * TODO: this could cause a theoretical memory reclaim |
| 141 | * deadlock in the swap out path. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 142 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 143 | /* |
| 144 | * Add it to the swap cache and mark it dirty |
| 145 | */ |
Hugh Dickins | f000944 | 2008-02-04 22:28:49 -0800 | [diff] [blame] | 146 | err = add_to_swap_cache(page, entry, |
Christoph Lameter | 1480a54 | 2006-01-08 01:00:53 -0800 | [diff] [blame] | 147 | gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 148 | |
| 149 | switch (err) { |
| 150 | case 0: /* Success */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 151 | SetPageDirty(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 152 | return 1; |
| 153 | case -EEXIST: |
| 154 | /* Raced with "speculative" read_swap_cache_async */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 155 | swap_free(entry); |
| 156 | continue; |
| 157 | default: |
| 158 | /* -ENOMEM radix-tree allocation failure */ |
| 159 | swap_free(entry); |
| 160 | return 0; |
| 161 | } |
| 162 | } |
| 163 | } |
| 164 | |
| 165 | /* |
| 166 | * This must be called only on pages that have |
| 167 | * been verified to be in the swap cache and locked. |
| 168 | * It will never put the page into the free list, |
| 169 | * the caller has a reference on the page. |
| 170 | */ |
| 171 | void delete_from_swap_cache(struct page *page) |
| 172 | { |
| 173 | swp_entry_t entry; |
| 174 | |
Hugh Dickins | 4c21e2f | 2005-10-29 18:16:40 -0700 | [diff] [blame] | 175 | entry.val = page_private(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 176 | |
| 177 | write_lock_irq(&swapper_space.tree_lock); |
| 178 | __delete_from_swap_cache(page); |
| 179 | write_unlock_irq(&swapper_space.tree_lock); |
| 180 | |
| 181 | swap_free(entry); |
| 182 | page_cache_release(page); |
| 183 | } |
| 184 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 185 | /* |
| 186 | * If we are the only user, then try to free up the swap cache. |
| 187 | * |
| 188 | * Its ok to check for PageSwapCache without the page lock |
| 189 | * here because we are going to recheck again inside |
| 190 | * exclusive_swap_page() _with_ the lock. |
| 191 | * - Marcelo |
| 192 | */ |
| 193 | static inline void free_swap_cache(struct page *page) |
| 194 | { |
| 195 | if (PageSwapCache(page) && !TestSetPageLocked(page)) { |
| 196 | remove_exclusive_swap_page(page); |
| 197 | unlock_page(page); |
| 198 | } |
| 199 | } |
| 200 | |
| 201 | /* |
| 202 | * Perform a free_page(), also freeing any swap cache associated with |
Hugh Dickins | b8072f0 | 2005-10-29 18:16:41 -0700 | [diff] [blame] | 203 | * this page if it is the last user of the page. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 204 | */ |
| 205 | void free_page_and_swap_cache(struct page *page) |
| 206 | { |
| 207 | free_swap_cache(page); |
| 208 | page_cache_release(page); |
| 209 | } |
| 210 | |
| 211 | /* |
| 212 | * Passed an array of pages, drop them all from swapcache and then release |
| 213 | * them. They are removed from the LRU and freed if this is their last use. |
| 214 | */ |
| 215 | void free_pages_and_swap_cache(struct page **pages, int nr) |
| 216 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 217 | struct page **pagep = pages; |
| 218 | |
| 219 | lru_add_drain(); |
| 220 | while (nr) { |
Hugh Dickins | c484d41 | 2006-01-06 00:10:55 -0800 | [diff] [blame] | 221 | int todo = min(nr, PAGEVEC_SIZE); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 222 | int i; |
| 223 | |
| 224 | for (i = 0; i < todo; i++) |
| 225 | free_swap_cache(pagep[i]); |
| 226 | release_pages(pagep, todo, 0); |
| 227 | pagep += todo; |
| 228 | nr -= todo; |
| 229 | } |
| 230 | } |
| 231 | |
| 232 | /* |
| 233 | * Lookup a swap entry in the swap cache. A found page will be returned |
| 234 | * unlocked and with its refcount incremented - we rely on the kernel |
| 235 | * lock getting page table operations atomic even if we drop the page |
| 236 | * lock before returning. |
| 237 | */ |
| 238 | struct page * lookup_swap_cache(swp_entry_t entry) |
| 239 | { |
| 240 | struct page *page; |
| 241 | |
| 242 | page = find_get_page(&swapper_space, entry.val); |
| 243 | |
| 244 | if (page) |
| 245 | INC_CACHE_INFO(find_success); |
| 246 | |
| 247 | INC_CACHE_INFO(find_total); |
| 248 | return page; |
| 249 | } |
| 250 | |
| 251 | /* |
| 252 | * Locate a page of swap in physical memory, reserving swap cache space |
| 253 | * and reading the disk if it is not already cached. |
| 254 | * A failure return means that either the page allocation failed or that |
| 255 | * the swap entry is no longer in use. |
| 256 | */ |
Hugh Dickins | 02098fe | 2008-02-04 22:28:42 -0800 | [diff] [blame] | 257 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 258 | struct vm_area_struct *vma, unsigned long addr) |
| 259 | { |
| 260 | struct page *found_page, *new_page = NULL; |
| 261 | int err; |
| 262 | |
| 263 | do { |
| 264 | /* |
| 265 | * First check the swap cache. Since this is normally |
| 266 | * called after lookup_swap_cache() failed, re-calling |
| 267 | * that would confuse statistics. |
| 268 | */ |
| 269 | found_page = find_get_page(&swapper_space, entry.val); |
| 270 | if (found_page) |
| 271 | break; |
| 272 | |
| 273 | /* |
| 274 | * Get a new page to read into from swap. |
| 275 | */ |
| 276 | if (!new_page) { |
Hugh Dickins | 02098fe | 2008-02-04 22:28:42 -0800 | [diff] [blame] | 277 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 278 | if (!new_page) |
| 279 | break; /* Out of memory */ |
| 280 | } |
| 281 | |
| 282 | /* |
Hugh Dickins | f000944 | 2008-02-04 22:28:49 -0800 | [diff] [blame] | 283 | * Swap entry may have been freed since our caller observed it. |
| 284 | */ |
| 285 | if (!swap_duplicate(entry)) |
| 286 | break; |
| 287 | |
| 288 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 289 | * Associate the page with swap entry in the swap cache. |
Hugh Dickins | f000944 | 2008-02-04 22:28:49 -0800 | [diff] [blame] | 290 | * May fail (-EEXIST) if there is already a page associated |
| 291 | * with this entry in the swap cache: added by a racing |
| 292 | * read_swap_cache_async, or add_to_swap or shmem_writepage |
| 293 | * re-using the just freed swap entry for an existing page. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 294 | * May fail (-ENOMEM) if radix-tree node allocation failed. |
| 295 | */ |
Hugh Dickins | f000944 | 2008-02-04 22:28:49 -0800 | [diff] [blame] | 296 | SetPageLocked(new_page); |
| 297 | err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 298 | if (!err) { |
| 299 | /* |
| 300 | * Initiate read into locked page and return. |
| 301 | */ |
| 302 | lru_cache_add_active(new_page); |
| 303 | swap_readpage(NULL, new_page); |
| 304 | return new_page; |
| 305 | } |
Hugh Dickins | f000944 | 2008-02-04 22:28:49 -0800 | [diff] [blame] | 306 | ClearPageLocked(new_page); |
| 307 | swap_free(entry); |
| 308 | } while (err != -ENOMEM); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 309 | |
| 310 | if (new_page) |
| 311 | page_cache_release(new_page); |
| 312 | return found_page; |
| 313 | } |
Hugh Dickins | 46017e9 | 2008-02-04 22:28:41 -0800 | [diff] [blame] | 314 | |
| 315 | /** |
| 316 | * swapin_readahead - swap in pages in hope we need them soon |
| 317 | * @entry: swap entry of this memory |
| 318 | * @vma: user vma this address belongs to |
| 319 | * @addr: target address for mempolicy |
| 320 | * |
| 321 | * Returns the struct page for entry and addr, after queueing swapin. |
| 322 | * |
| 323 | * Primitive swap readahead code. We simply read an aligned block of |
| 324 | * (1 << page_cluster) entries in the swap area. This method is chosen |
| 325 | * because it doesn't cost us any seek time. We also make sure to queue |
| 326 | * the 'original' request together with the readahead ones... |
| 327 | * |
| 328 | * This has been extended to use the NUMA policies from the mm triggering |
| 329 | * the readahead. |
| 330 | * |
| 331 | * Caller must hold down_read on the vma->vm_mm if vma is not NULL. |
| 332 | */ |
Hugh Dickins | 02098fe | 2008-02-04 22:28:42 -0800 | [diff] [blame] | 333 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
Hugh Dickins | 46017e9 | 2008-02-04 22:28:41 -0800 | [diff] [blame] | 334 | struct vm_area_struct *vma, unsigned long addr) |
| 335 | { |
| 336 | int nr_pages; |
| 337 | struct page *page; |
| 338 | unsigned long offset; |
| 339 | unsigned long end_offset; |
| 340 | |
| 341 | /* |
| 342 | * Get starting offset for readaround, and number of pages to read. |
| 343 | * Adjust starting address by readbehind (for NUMA interleave case)? |
| 344 | * No, it's very unlikely that swap layout would follow vma layout, |
| 345 | * more likely that neighbouring swap pages came from the same node: |
| 346 | * so use the same "addr" to choose the same node for each swap read. |
| 347 | */ |
| 348 | nr_pages = valid_swaphandles(entry, &offset); |
| 349 | for (end_offset = offset + nr_pages; offset < end_offset; offset++) { |
| 350 | /* Ok, do the async read-ahead now */ |
| 351 | page = read_swap_cache_async(swp_entry(swp_type(entry), offset), |
Hugh Dickins | 02098fe | 2008-02-04 22:28:42 -0800 | [diff] [blame] | 352 | gfp_mask, vma, addr); |
Hugh Dickins | 46017e9 | 2008-02-04 22:28:41 -0800 | [diff] [blame] | 353 | if (!page) |
| 354 | break; |
| 355 | page_cache_release(page); |
| 356 | } |
| 357 | lru_add_drain(); /* Push any new pages onto the LRU now */ |
Hugh Dickins | 02098fe | 2008-02-04 22:28:42 -0800 | [diff] [blame] | 358 | return read_swap_cache_async(entry, gfp_mask, vma, addr); |
Hugh Dickins | 46017e9 | 2008-02-04 22:28:41 -0800 | [diff] [blame] | 359 | } |