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1da177e4 LT |
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> | |
46017e95 | 13 | #include <linux/swapops.h> |
1da177e4 LT |
14 | #include <linux/init.h> |
15 | #include <linux/pagemap.h> | |
16 | #include <linux/buffer_head.h> | |
17 | #include <linux/backing-dev.h> | |
c484d410 | 18 | #include <linux/pagevec.h> |
b20a3503 | 19 | #include <linux/migrate.h> |
1da177e4 LT |
20 | |
21 | #include <asm/pgtable.h> | |
22 | ||
23 | /* | |
24 | * swapper_space is a fiction, retained to simplify the path through | |
2706a1b8 | 25 | * vmscan's shrink_page_list, to make sync_page look nicer, and to allow |
1da177e4 LT |
26 | * future use of radix_tree tags in the swap cache. |
27 | */ | |
f5e54d6e | 28 | static const struct address_space_operations swap_aops = { |
1da177e4 LT |
29 | .writepage = swap_writepage, |
30 | .sync_page = block_sync_page, | |
31 | .set_page_dirty = __set_page_dirty_nobuffers, | |
e965f963 | 32 | .migratepage = migrate_page, |
1da177e4 LT |
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), | |
e4d91918 | 42 | .tree_lock = __RW_LOCK_UNLOCKED(swapper_space.tree_lock), |
1da177e4 LT |
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 | }; | |
1da177e4 LT |
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; | |
55 | unsigned long noent_race; | |
56 | unsigned long exist_race; | |
57 | } swap_cache_info; | |
58 | ||
59 | void show_swap_cache_info(void) | |
60 | { | |
61 | printk("Swap cache: add %lu, delete %lu, find %lu/%lu, race %lu+%lu\n", | |
62 | swap_cache_info.add_total, swap_cache_info.del_total, | |
63 | swap_cache_info.find_success, swap_cache_info.find_total, | |
64 | swap_cache_info.noent_race, swap_cache_info.exist_race); | |
65 | printk("Free swap = %lukB\n", nr_swap_pages << (PAGE_SHIFT - 10)); | |
66 | printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); | |
67 | } | |
68 | ||
69 | /* | |
70 | * __add_to_swap_cache resembles add_to_page_cache on swapper_space, | |
71 | * but sets SwapCache flag and private instead of mapping and index. | |
72 | */ | |
9de75d11 | 73 | static int __add_to_swap_cache(struct page *page, swp_entry_t entry, |
dd0fc66f | 74 | gfp_t gfp_mask) |
1da177e4 LT |
75 | { |
76 | int error; | |
77 | ||
b55ed816 | 78 | BUG_ON(!PageLocked(page)); |
1da177e4 LT |
79 | BUG_ON(PageSwapCache(page)); |
80 | BUG_ON(PagePrivate(page)); | |
81 | error = radix_tree_preload(gfp_mask); | |
82 | if (!error) { | |
83 | write_lock_irq(&swapper_space.tree_lock); | |
84 | error = radix_tree_insert(&swapper_space.page_tree, | |
85 | entry.val, page); | |
86 | if (!error) { | |
87 | page_cache_get(page); | |
1da177e4 | 88 | SetPageSwapCache(page); |
4c21e2f2 | 89 | set_page_private(page, entry.val); |
1da177e4 | 90 | total_swapcache_pages++; |
347ce434 | 91 | __inc_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
92 | } |
93 | write_unlock_irq(&swapper_space.tree_lock); | |
94 | radix_tree_preload_end(); | |
95 | } | |
96 | return error; | |
97 | } | |
98 | ||
02098fea HD |
99 | static int add_to_swap_cache(struct page *page, swp_entry_t entry, |
100 | gfp_t gfp_mask) | |
1da177e4 LT |
101 | { |
102 | int error; | |
103 | ||
b55ed816 | 104 | BUG_ON(PageLocked(page)); |
1da177e4 LT |
105 | if (!swap_duplicate(entry)) { |
106 | INC_CACHE_INFO(noent_race); | |
107 | return -ENOENT; | |
108 | } | |
b55ed816 | 109 | SetPageLocked(page); |
02098fea | 110 | error = __add_to_swap_cache(page, entry, gfp_mask & GFP_KERNEL); |
1da177e4 LT |
111 | /* |
112 | * Anon pages are already on the LRU, we don't run lru_cache_add here. | |
113 | */ | |
114 | if (error) { | |
b55ed816 | 115 | ClearPageLocked(page); |
1da177e4 LT |
116 | swap_free(entry); |
117 | if (error == -EEXIST) | |
118 | INC_CACHE_INFO(exist_race); | |
119 | return error; | |
120 | } | |
121 | INC_CACHE_INFO(add_total); | |
122 | return 0; | |
123 | } | |
124 | ||
125 | /* | |
126 | * This must be called only on pages that have | |
127 | * been verified to be in the swap cache. | |
128 | */ | |
129 | void __delete_from_swap_cache(struct page *page) | |
130 | { | |
131 | BUG_ON(!PageLocked(page)); | |
132 | BUG_ON(!PageSwapCache(page)); | |
133 | BUG_ON(PageWriteback(page)); | |
3279ffd9 | 134 | BUG_ON(PagePrivate(page)); |
1da177e4 | 135 | |
4c21e2f2 HD |
136 | radix_tree_delete(&swapper_space.page_tree, page_private(page)); |
137 | set_page_private(page, 0); | |
1da177e4 LT |
138 | ClearPageSwapCache(page); |
139 | total_swapcache_pages--; | |
347ce434 | 140 | __dec_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
141 | INC_CACHE_INFO(del_total); |
142 | } | |
143 | ||
144 | /** | |
145 | * add_to_swap - allocate swap space for a page | |
146 | * @page: page we want to move to swap | |
147 | * | |
148 | * Allocate swap space for the page and add the page to the | |
149 | * swap cache. Caller needs to hold the page lock. | |
150 | */ | |
1480a540 | 151 | int add_to_swap(struct page * page, gfp_t gfp_mask) |
1da177e4 LT |
152 | { |
153 | swp_entry_t entry; | |
1da177e4 LT |
154 | int err; |
155 | ||
e74ca2b4 | 156 | BUG_ON(!PageLocked(page)); |
1da177e4 LT |
157 | |
158 | for (;;) { | |
159 | entry = get_swap_page(); | |
160 | if (!entry.val) | |
161 | return 0; | |
162 | ||
bd53b714 NP |
163 | /* |
164 | * Radix-tree node allocations from PF_MEMALLOC contexts could | |
165 | * completely exhaust the page allocator. __GFP_NOMEMALLOC | |
166 | * stops emergency reserves from being allocated. | |
1da177e4 | 167 | * |
bd53b714 NP |
168 | * TODO: this could cause a theoretical memory reclaim |
169 | * deadlock in the swap out path. | |
1da177e4 | 170 | */ |
1da177e4 LT |
171 | /* |
172 | * Add it to the swap cache and mark it dirty | |
173 | */ | |
bd53b714 | 174 | err = __add_to_swap_cache(page, entry, |
1480a540 | 175 | gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN); |
1da177e4 LT |
176 | |
177 | switch (err) { | |
178 | case 0: /* Success */ | |
179 | SetPageUptodate(page); | |
180 | SetPageDirty(page); | |
181 | INC_CACHE_INFO(add_total); | |
182 | return 1; | |
183 | case -EEXIST: | |
184 | /* Raced with "speculative" read_swap_cache_async */ | |
185 | INC_CACHE_INFO(exist_race); | |
186 | swap_free(entry); | |
187 | continue; | |
188 | default: | |
189 | /* -ENOMEM radix-tree allocation failure */ | |
190 | swap_free(entry); | |
191 | return 0; | |
192 | } | |
193 | } | |
194 | } | |
195 | ||
196 | /* | |
197 | * This must be called only on pages that have | |
198 | * been verified to be in the swap cache and locked. | |
199 | * It will never put the page into the free list, | |
200 | * the caller has a reference on the page. | |
201 | */ | |
202 | void delete_from_swap_cache(struct page *page) | |
203 | { | |
204 | swp_entry_t entry; | |
205 | ||
4c21e2f2 | 206 | entry.val = page_private(page); |
1da177e4 LT |
207 | |
208 | write_lock_irq(&swapper_space.tree_lock); | |
209 | __delete_from_swap_cache(page); | |
210 | write_unlock_irq(&swapper_space.tree_lock); | |
211 | ||
212 | swap_free(entry); | |
213 | page_cache_release(page); | |
214 | } | |
215 | ||
216 | /* | |
217 | * Strange swizzling function only for use by shmem_writepage | |
218 | */ | |
219 | int move_to_swap_cache(struct page *page, swp_entry_t entry) | |
220 | { | |
221 | int err = __add_to_swap_cache(page, entry, GFP_ATOMIC); | |
222 | if (!err) { | |
223 | remove_from_page_cache(page); | |
224 | page_cache_release(page); /* pagecache ref */ | |
225 | if (!swap_duplicate(entry)) | |
226 | BUG(); | |
227 | SetPageDirty(page); | |
228 | INC_CACHE_INFO(add_total); | |
229 | } else if (err == -EEXIST) | |
230 | INC_CACHE_INFO(exist_race); | |
231 | return err; | |
232 | } | |
233 | ||
234 | /* | |
235 | * Strange swizzling function for shmem_getpage (and shmem_unuse) | |
236 | */ | |
237 | int move_from_swap_cache(struct page *page, unsigned long index, | |
238 | struct address_space *mapping) | |
239 | { | |
240 | int err = add_to_page_cache(page, mapping, index, GFP_ATOMIC); | |
241 | if (!err) { | |
242 | delete_from_swap_cache(page); | |
243 | /* shift page from clean_pages to dirty_pages list */ | |
244 | ClearPageDirty(page); | |
245 | set_page_dirty(page); | |
246 | } | |
247 | return err; | |
248 | } | |
249 | ||
250 | /* | |
251 | * If we are the only user, then try to free up the swap cache. | |
252 | * | |
253 | * Its ok to check for PageSwapCache without the page lock | |
254 | * here because we are going to recheck again inside | |
255 | * exclusive_swap_page() _with_ the lock. | |
256 | * - Marcelo | |
257 | */ | |
258 | static inline void free_swap_cache(struct page *page) | |
259 | { | |
260 | if (PageSwapCache(page) && !TestSetPageLocked(page)) { | |
261 | remove_exclusive_swap_page(page); | |
262 | unlock_page(page); | |
263 | } | |
264 | } | |
265 | ||
266 | /* | |
267 | * Perform a free_page(), also freeing any swap cache associated with | |
b8072f09 | 268 | * this page if it is the last user of the page. |
1da177e4 LT |
269 | */ |
270 | void free_page_and_swap_cache(struct page *page) | |
271 | { | |
272 | free_swap_cache(page); | |
273 | page_cache_release(page); | |
274 | } | |
275 | ||
276 | /* | |
277 | * Passed an array of pages, drop them all from swapcache and then release | |
278 | * them. They are removed from the LRU and freed if this is their last use. | |
279 | */ | |
280 | void free_pages_and_swap_cache(struct page **pages, int nr) | |
281 | { | |
1da177e4 LT |
282 | struct page **pagep = pages; |
283 | ||
284 | lru_add_drain(); | |
285 | while (nr) { | |
c484d410 | 286 | int todo = min(nr, PAGEVEC_SIZE); |
1da177e4 LT |
287 | int i; |
288 | ||
289 | for (i = 0; i < todo; i++) | |
290 | free_swap_cache(pagep[i]); | |
291 | release_pages(pagep, todo, 0); | |
292 | pagep += todo; | |
293 | nr -= todo; | |
294 | } | |
295 | } | |
296 | ||
297 | /* | |
298 | * Lookup a swap entry in the swap cache. A found page will be returned | |
299 | * unlocked and with its refcount incremented - we rely on the kernel | |
300 | * lock getting page table operations atomic even if we drop the page | |
301 | * lock before returning. | |
302 | */ | |
303 | struct page * lookup_swap_cache(swp_entry_t entry) | |
304 | { | |
305 | struct page *page; | |
306 | ||
307 | page = find_get_page(&swapper_space, entry.val); | |
308 | ||
309 | if (page) | |
310 | INC_CACHE_INFO(find_success); | |
311 | ||
312 | INC_CACHE_INFO(find_total); | |
313 | return page; | |
314 | } | |
315 | ||
316 | /* | |
317 | * Locate a page of swap in physical memory, reserving swap cache space | |
318 | * and reading the disk if it is not already cached. | |
319 | * A failure return means that either the page allocation failed or that | |
320 | * the swap entry is no longer in use. | |
321 | */ | |
02098fea | 322 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
1da177e4 LT |
323 | struct vm_area_struct *vma, unsigned long addr) |
324 | { | |
325 | struct page *found_page, *new_page = NULL; | |
326 | int err; | |
327 | ||
328 | do { | |
329 | /* | |
330 | * First check the swap cache. Since this is normally | |
331 | * called after lookup_swap_cache() failed, re-calling | |
332 | * that would confuse statistics. | |
333 | */ | |
334 | found_page = find_get_page(&swapper_space, entry.val); | |
335 | if (found_page) | |
336 | break; | |
337 | ||
338 | /* | |
339 | * Get a new page to read into from swap. | |
340 | */ | |
341 | if (!new_page) { | |
02098fea | 342 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
1da177e4 LT |
343 | if (!new_page) |
344 | break; /* Out of memory */ | |
345 | } | |
346 | ||
347 | /* | |
348 | * Associate the page with swap entry in the swap cache. | |
349 | * May fail (-ENOENT) if swap entry has been freed since | |
350 | * our caller observed it. May fail (-EEXIST) if there | |
351 | * is already a page associated with this entry in the | |
352 | * swap cache: added by a racing read_swap_cache_async, | |
353 | * or by try_to_swap_out (or shmem_writepage) re-using | |
354 | * the just freed swap entry for an existing page. | |
355 | * May fail (-ENOMEM) if radix-tree node allocation failed. | |
356 | */ | |
02098fea | 357 | err = add_to_swap_cache(new_page, entry, gfp_mask); |
1da177e4 LT |
358 | if (!err) { |
359 | /* | |
360 | * Initiate read into locked page and return. | |
361 | */ | |
362 | lru_cache_add_active(new_page); | |
363 | swap_readpage(NULL, new_page); | |
364 | return new_page; | |
365 | } | |
366 | } while (err != -ENOENT && err != -ENOMEM); | |
367 | ||
368 | if (new_page) | |
369 | page_cache_release(new_page); | |
370 | return found_page; | |
371 | } | |
46017e95 HD |
372 | |
373 | /** | |
374 | * swapin_readahead - swap in pages in hope we need them soon | |
375 | * @entry: swap entry of this memory | |
376 | * @vma: user vma this address belongs to | |
377 | * @addr: target address for mempolicy | |
378 | * | |
379 | * Returns the struct page for entry and addr, after queueing swapin. | |
380 | * | |
381 | * Primitive swap readahead code. We simply read an aligned block of | |
382 | * (1 << page_cluster) entries in the swap area. This method is chosen | |
383 | * because it doesn't cost us any seek time. We also make sure to queue | |
384 | * the 'original' request together with the readahead ones... | |
385 | * | |
386 | * This has been extended to use the NUMA policies from the mm triggering | |
387 | * the readahead. | |
388 | * | |
389 | * Caller must hold down_read on the vma->vm_mm if vma is not NULL. | |
390 | */ | |
02098fea | 391 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
46017e95 HD |
392 | struct vm_area_struct *vma, unsigned long addr) |
393 | { | |
394 | int nr_pages; | |
395 | struct page *page; | |
396 | unsigned long offset; | |
397 | unsigned long end_offset; | |
398 | ||
399 | /* | |
400 | * Get starting offset for readaround, and number of pages to read. | |
401 | * Adjust starting address by readbehind (for NUMA interleave case)? | |
402 | * No, it's very unlikely that swap layout would follow vma layout, | |
403 | * more likely that neighbouring swap pages came from the same node: | |
404 | * so use the same "addr" to choose the same node for each swap read. | |
405 | */ | |
406 | nr_pages = valid_swaphandles(entry, &offset); | |
407 | for (end_offset = offset + nr_pages; offset < end_offset; offset++) { | |
408 | /* Ok, do the async read-ahead now */ | |
409 | page = read_swap_cache_async(swp_entry(swp_type(entry), offset), | |
02098fea | 410 | gfp_mask, vma, addr); |
46017e95 HD |
411 | if (!page) |
412 | break; | |
413 | page_cache_release(page); | |
414 | } | |
415 | lru_add_drain(); /* Push any new pages onto the LRU now */ | |
02098fea | 416 | return read_swap_cache_async(entry, gfp_mask, vma, addr); |
46017e95 | 417 | } |