Commit | Line | Data |
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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 | ||
99 | static int add_to_swap_cache(struct page *page, swp_entry_t entry) | |
100 | { | |
101 | int error; | |
102 | ||
b55ed816 | 103 | BUG_ON(PageLocked(page)); |
1da177e4 LT |
104 | if (!swap_duplicate(entry)) { |
105 | INC_CACHE_INFO(noent_race); | |
106 | return -ENOENT; | |
107 | } | |
b55ed816 | 108 | SetPageLocked(page); |
1da177e4 LT |
109 | error = __add_to_swap_cache(page, entry, GFP_KERNEL); |
110 | /* | |
111 | * Anon pages are already on the LRU, we don't run lru_cache_add here. | |
112 | */ | |
113 | if (error) { | |
b55ed816 | 114 | ClearPageLocked(page); |
1da177e4 LT |
115 | swap_free(entry); |
116 | if (error == -EEXIST) | |
117 | INC_CACHE_INFO(exist_race); | |
118 | return error; | |
119 | } | |
120 | INC_CACHE_INFO(add_total); | |
121 | return 0; | |
122 | } | |
123 | ||
124 | /* | |
125 | * This must be called only on pages that have | |
126 | * been verified to be in the swap cache. | |
127 | */ | |
128 | void __delete_from_swap_cache(struct page *page) | |
129 | { | |
130 | BUG_ON(!PageLocked(page)); | |
131 | BUG_ON(!PageSwapCache(page)); | |
132 | BUG_ON(PageWriteback(page)); | |
3279ffd9 | 133 | BUG_ON(PagePrivate(page)); |
1da177e4 | 134 | |
4c21e2f2 HD |
135 | radix_tree_delete(&swapper_space.page_tree, page_private(page)); |
136 | set_page_private(page, 0); | |
1da177e4 LT |
137 | ClearPageSwapCache(page); |
138 | total_swapcache_pages--; | |
347ce434 | 139 | __dec_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
140 | INC_CACHE_INFO(del_total); |
141 | } | |
142 | ||
143 | /** | |
144 | * add_to_swap - allocate swap space for a page | |
145 | * @page: page we want to move to swap | |
146 | * | |
147 | * Allocate swap space for the page and add the page to the | |
148 | * swap cache. Caller needs to hold the page lock. | |
149 | */ | |
1480a540 | 150 | int add_to_swap(struct page * page, gfp_t gfp_mask) |
1da177e4 LT |
151 | { |
152 | swp_entry_t entry; | |
1da177e4 LT |
153 | int err; |
154 | ||
e74ca2b4 | 155 | BUG_ON(!PageLocked(page)); |
1da177e4 LT |
156 | |
157 | for (;;) { | |
158 | entry = get_swap_page(); | |
159 | if (!entry.val) | |
160 | return 0; | |
161 | ||
bd53b714 NP |
162 | /* |
163 | * Radix-tree node allocations from PF_MEMALLOC contexts could | |
164 | * completely exhaust the page allocator. __GFP_NOMEMALLOC | |
165 | * stops emergency reserves from being allocated. | |
1da177e4 | 166 | * |
bd53b714 NP |
167 | * TODO: this could cause a theoretical memory reclaim |
168 | * deadlock in the swap out path. | |
1da177e4 | 169 | */ |
1da177e4 LT |
170 | /* |
171 | * Add it to the swap cache and mark it dirty | |
172 | */ | |
bd53b714 | 173 | err = __add_to_swap_cache(page, entry, |
1480a540 | 174 | gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN); |
1da177e4 LT |
175 | |
176 | switch (err) { | |
177 | case 0: /* Success */ | |
178 | SetPageUptodate(page); | |
179 | SetPageDirty(page); | |
180 | INC_CACHE_INFO(add_total); | |
181 | return 1; | |
182 | case -EEXIST: | |
183 | /* Raced with "speculative" read_swap_cache_async */ | |
184 | INC_CACHE_INFO(exist_race); | |
185 | swap_free(entry); | |
186 | continue; | |
187 | default: | |
188 | /* -ENOMEM radix-tree allocation failure */ | |
189 | swap_free(entry); | |
190 | return 0; | |
191 | } | |
192 | } | |
193 | } | |
194 | ||
195 | /* | |
196 | * This must be called only on pages that have | |
197 | * been verified to be in the swap cache and locked. | |
198 | * It will never put the page into the free list, | |
199 | * the caller has a reference on the page. | |
200 | */ | |
201 | void delete_from_swap_cache(struct page *page) | |
202 | { | |
203 | swp_entry_t entry; | |
204 | ||
4c21e2f2 | 205 | entry.val = page_private(page); |
1da177e4 LT |
206 | |
207 | write_lock_irq(&swapper_space.tree_lock); | |
208 | __delete_from_swap_cache(page); | |
209 | write_unlock_irq(&swapper_space.tree_lock); | |
210 | ||
211 | swap_free(entry); | |
212 | page_cache_release(page); | |
213 | } | |
214 | ||
215 | /* | |
216 | * Strange swizzling function only for use by shmem_writepage | |
217 | */ | |
218 | int move_to_swap_cache(struct page *page, swp_entry_t entry) | |
219 | { | |
220 | int err = __add_to_swap_cache(page, entry, GFP_ATOMIC); | |
221 | if (!err) { | |
222 | remove_from_page_cache(page); | |
223 | page_cache_release(page); /* pagecache ref */ | |
224 | if (!swap_duplicate(entry)) | |
225 | BUG(); | |
226 | SetPageDirty(page); | |
227 | INC_CACHE_INFO(add_total); | |
228 | } else if (err == -EEXIST) | |
229 | INC_CACHE_INFO(exist_race); | |
230 | return err; | |
231 | } | |
232 | ||
233 | /* | |
234 | * Strange swizzling function for shmem_getpage (and shmem_unuse) | |
235 | */ | |
236 | int move_from_swap_cache(struct page *page, unsigned long index, | |
237 | struct address_space *mapping) | |
238 | { | |
239 | int err = add_to_page_cache(page, mapping, index, GFP_ATOMIC); | |
240 | if (!err) { | |
241 | delete_from_swap_cache(page); | |
242 | /* shift page from clean_pages to dirty_pages list */ | |
243 | ClearPageDirty(page); | |
244 | set_page_dirty(page); | |
245 | } | |
246 | return err; | |
247 | } | |
248 | ||
249 | /* | |
250 | * If we are the only user, then try to free up the swap cache. | |
251 | * | |
252 | * Its ok to check for PageSwapCache without the page lock | |
253 | * here because we are going to recheck again inside | |
254 | * exclusive_swap_page() _with_ the lock. | |
255 | * - Marcelo | |
256 | */ | |
257 | static inline void free_swap_cache(struct page *page) | |
258 | { | |
259 | if (PageSwapCache(page) && !TestSetPageLocked(page)) { | |
260 | remove_exclusive_swap_page(page); | |
261 | unlock_page(page); | |
262 | } | |
263 | } | |
264 | ||
265 | /* | |
266 | * Perform a free_page(), also freeing any swap cache associated with | |
b8072f09 | 267 | * this page if it is the last user of the page. |
1da177e4 LT |
268 | */ |
269 | void free_page_and_swap_cache(struct page *page) | |
270 | { | |
271 | free_swap_cache(page); | |
272 | page_cache_release(page); | |
273 | } | |
274 | ||
275 | /* | |
276 | * Passed an array of pages, drop them all from swapcache and then release | |
277 | * them. They are removed from the LRU and freed if this is their last use. | |
278 | */ | |
279 | void free_pages_and_swap_cache(struct page **pages, int nr) | |
280 | { | |
1da177e4 LT |
281 | struct page **pagep = pages; |
282 | ||
283 | lru_add_drain(); | |
284 | while (nr) { | |
c484d410 | 285 | int todo = min(nr, PAGEVEC_SIZE); |
1da177e4 LT |
286 | int i; |
287 | ||
288 | for (i = 0; i < todo; i++) | |
289 | free_swap_cache(pagep[i]); | |
290 | release_pages(pagep, todo, 0); | |
291 | pagep += todo; | |
292 | nr -= todo; | |
293 | } | |
294 | } | |
295 | ||
296 | /* | |
297 | * Lookup a swap entry in the swap cache. A found page will be returned | |
298 | * unlocked and with its refcount incremented - we rely on the kernel | |
299 | * lock getting page table operations atomic even if we drop the page | |
300 | * lock before returning. | |
301 | */ | |
302 | struct page * lookup_swap_cache(swp_entry_t entry) | |
303 | { | |
304 | struct page *page; | |
305 | ||
306 | page = find_get_page(&swapper_space, entry.val); | |
307 | ||
308 | if (page) | |
309 | INC_CACHE_INFO(find_success); | |
310 | ||
311 | INC_CACHE_INFO(find_total); | |
312 | return page; | |
313 | } | |
314 | ||
315 | /* | |
316 | * Locate a page of swap in physical memory, reserving swap cache space | |
317 | * and reading the disk if it is not already cached. | |
318 | * A failure return means that either the page allocation failed or that | |
319 | * the swap entry is no longer in use. | |
320 | */ | |
321 | struct page *read_swap_cache_async(swp_entry_t entry, | |
322 | struct vm_area_struct *vma, unsigned long addr) | |
323 | { | |
324 | struct page *found_page, *new_page = NULL; | |
325 | int err; | |
326 | ||
327 | do { | |
328 | /* | |
329 | * First check the swap cache. Since this is normally | |
330 | * called after lookup_swap_cache() failed, re-calling | |
331 | * that would confuse statistics. | |
332 | */ | |
333 | found_page = find_get_page(&swapper_space, entry.val); | |
334 | if (found_page) | |
335 | break; | |
336 | ||
337 | /* | |
338 | * Get a new page to read into from swap. | |
339 | */ | |
340 | if (!new_page) { | |
769848c0 MG |
341 | new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, |
342 | 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 | */ | |
357 | err = add_to_swap_cache(new_page, entry); | |
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 | */ | |
391 | struct page *swapin_readahead(swp_entry_t entry, | |
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), | |
410 | vma, addr); | |
411 | if (!page) | |
412 | break; | |
413 | page_cache_release(page); | |
414 | } | |
415 | lru_add_drain(); /* Push any new pages onto the LRU now */ | |
416 | return read_swap_cache_async(entry, vma, addr); | |
417 | } |