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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 | */ | |
1da177e4 | 9 | #include <linux/mm.h> |
5a0e3ad6 | 10 | #include <linux/gfp.h> |
1da177e4 LT |
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> | |
1da177e4 | 16 | #include <linux/backing-dev.h> |
3fb5c298 | 17 | #include <linux/blkdev.h> |
c484d410 | 18 | #include <linux/pagevec.h> |
b20a3503 | 19 | #include <linux/migrate.h> |
8c7c6e34 | 20 | #include <linux/page_cgroup.h> |
1da177e4 LT |
21 | |
22 | #include <asm/pgtable.h> | |
23 | ||
24 | /* | |
25 | * swapper_space is a fiction, retained to simplify the path through | |
7eaceacc | 26 | * vmscan's shrink_page_list. |
1da177e4 | 27 | */ |
f5e54d6e | 28 | static const struct address_space_operations swap_aops = { |
1da177e4 | 29 | .writepage = swap_writepage, |
62c230bc | 30 | .set_page_dirty = swap_set_page_dirty, |
e965f963 | 31 | .migratepage = migrate_page, |
1da177e4 LT |
32 | }; |
33 | ||
34 | static struct backing_dev_info swap_backing_dev_info = { | |
d993831f | 35 | .name = "swap", |
4f98a2fe | 36 | .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED, |
1da177e4 LT |
37 | }; |
38 | ||
33806f06 SL |
39 | struct address_space swapper_spaces[MAX_SWAPFILES] = { |
40 | [0 ... MAX_SWAPFILES - 1] = { | |
41 | .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN), | |
42 | .a_ops = &swap_aops, | |
43 | .backing_dev_info = &swap_backing_dev_info, | |
44 | } | |
1da177e4 | 45 | }; |
1da177e4 LT |
46 | |
47 | #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) | |
48 | ||
49 | static struct { | |
50 | unsigned long add_total; | |
51 | unsigned long del_total; | |
52 | unsigned long find_success; | |
53 | unsigned long find_total; | |
1da177e4 LT |
54 | } swap_cache_info; |
55 | ||
33806f06 SL |
56 | unsigned long total_swapcache_pages(void) |
57 | { | |
58 | int i; | |
59 | unsigned long ret = 0; | |
60 | ||
61 | for (i = 0; i < MAX_SWAPFILES; i++) | |
62 | ret += swapper_spaces[i].nrpages; | |
63 | return ret; | |
64 | } | |
65 | ||
1da177e4 LT |
66 | void show_swap_cache_info(void) |
67 | { | |
33806f06 | 68 | printk("%lu pages in swap cache\n", total_swapcache_pages()); |
2c97b7fc | 69 | printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n", |
1da177e4 | 70 | swap_cache_info.add_total, swap_cache_info.del_total, |
bb63be0a | 71 | swap_cache_info.find_success, swap_cache_info.find_total); |
07279cdf | 72 | printk("Free swap = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10)); |
1da177e4 LT |
73 | printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); |
74 | } | |
75 | ||
76 | /* | |
31a56396 | 77 | * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space, |
1da177e4 LT |
78 | * but sets SwapCache flag and private instead of mapping and index. |
79 | */ | |
31a56396 | 80 | static int __add_to_swap_cache(struct page *page, swp_entry_t entry) |
1da177e4 LT |
81 | { |
82 | int error; | |
33806f06 | 83 | struct address_space *address_space; |
1da177e4 | 84 | |
51726b12 HD |
85 | VM_BUG_ON(!PageLocked(page)); |
86 | VM_BUG_ON(PageSwapCache(page)); | |
87 | VM_BUG_ON(!PageSwapBacked(page)); | |
88 | ||
31a56396 DN |
89 | page_cache_get(page); |
90 | SetPageSwapCache(page); | |
91 | set_page_private(page, entry.val); | |
92 | ||
33806f06 SL |
93 | address_space = swap_address_space(entry); |
94 | spin_lock_irq(&address_space->tree_lock); | |
95 | error = radix_tree_insert(&address_space->page_tree, | |
96 | entry.val, page); | |
31a56396 | 97 | if (likely(!error)) { |
33806f06 | 98 | address_space->nrpages++; |
31a56396 DN |
99 | __inc_zone_page_state(page, NR_FILE_PAGES); |
100 | INC_CACHE_INFO(add_total); | |
101 | } | |
33806f06 | 102 | spin_unlock_irq(&address_space->tree_lock); |
31a56396 DN |
103 | |
104 | if (unlikely(error)) { | |
2ca4532a DN |
105 | /* |
106 | * Only the context which have set SWAP_HAS_CACHE flag | |
107 | * would call add_to_swap_cache(). | |
108 | * So add_to_swap_cache() doesn't returns -EEXIST. | |
109 | */ | |
110 | VM_BUG_ON(error == -EEXIST); | |
31a56396 DN |
111 | set_page_private(page, 0UL); |
112 | ClearPageSwapCache(page); | |
113 | page_cache_release(page); | |
114 | } | |
115 | ||
116 | return error; | |
117 | } | |
118 | ||
119 | ||
120 | int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) | |
121 | { | |
122 | int error; | |
123 | ||
35c754d7 BS |
124 | error = radix_tree_preload(gfp_mask); |
125 | if (!error) { | |
31a56396 | 126 | error = __add_to_swap_cache(page, entry); |
1da177e4 | 127 | radix_tree_preload_end(); |
fa1de900 | 128 | } |
1da177e4 LT |
129 | return error; |
130 | } | |
131 | ||
1da177e4 LT |
132 | /* |
133 | * This must be called only on pages that have | |
134 | * been verified to be in the swap cache. | |
135 | */ | |
136 | void __delete_from_swap_cache(struct page *page) | |
137 | { | |
33806f06 SL |
138 | swp_entry_t entry; |
139 | struct address_space *address_space; | |
140 | ||
51726b12 HD |
141 | VM_BUG_ON(!PageLocked(page)); |
142 | VM_BUG_ON(!PageSwapCache(page)); | |
143 | VM_BUG_ON(PageWriteback(page)); | |
1da177e4 | 144 | |
33806f06 SL |
145 | entry.val = page_private(page); |
146 | address_space = swap_address_space(entry); | |
147 | radix_tree_delete(&address_space->page_tree, page_private(page)); | |
4c21e2f2 | 148 | set_page_private(page, 0); |
1da177e4 | 149 | ClearPageSwapCache(page); |
33806f06 | 150 | address_space->nrpages--; |
347ce434 | 151 | __dec_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
152 | INC_CACHE_INFO(del_total); |
153 | } | |
154 | ||
155 | /** | |
156 | * add_to_swap - allocate swap space for a page | |
157 | * @page: page we want to move to swap | |
158 | * | |
159 | * Allocate swap space for the page and add the page to the | |
160 | * swap cache. Caller needs to hold the page lock. | |
161 | */ | |
ac47b003 | 162 | int add_to_swap(struct page *page) |
1da177e4 LT |
163 | { |
164 | swp_entry_t entry; | |
1da177e4 LT |
165 | int err; |
166 | ||
51726b12 HD |
167 | VM_BUG_ON(!PageLocked(page)); |
168 | VM_BUG_ON(!PageUptodate(page)); | |
1da177e4 | 169 | |
2ca4532a DN |
170 | entry = get_swap_page(); |
171 | if (!entry.val) | |
172 | return 0; | |
173 | ||
3f04f62f AA |
174 | if (unlikely(PageTransHuge(page))) |
175 | if (unlikely(split_huge_page(page))) { | |
176 | swapcache_free(entry, NULL); | |
177 | return 0; | |
178 | } | |
179 | ||
2ca4532a DN |
180 | /* |
181 | * Radix-tree node allocations from PF_MEMALLOC contexts could | |
182 | * completely exhaust the page allocator. __GFP_NOMEMALLOC | |
183 | * stops emergency reserves from being allocated. | |
184 | * | |
185 | * TODO: this could cause a theoretical memory reclaim | |
186 | * deadlock in the swap out path. | |
187 | */ | |
188 | /* | |
189 | * Add it to the swap cache and mark it dirty | |
190 | */ | |
191 | err = add_to_swap_cache(page, entry, | |
192 | __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); | |
193 | ||
194 | if (!err) { /* Success */ | |
195 | SetPageDirty(page); | |
196 | return 1; | |
197 | } else { /* -ENOMEM radix-tree allocation failure */ | |
bd53b714 | 198 | /* |
2ca4532a DN |
199 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
200 | * clear SWAP_HAS_CACHE flag. | |
1da177e4 | 201 | */ |
2ca4532a DN |
202 | swapcache_free(entry, NULL); |
203 | return 0; | |
1da177e4 LT |
204 | } |
205 | } | |
206 | ||
207 | /* | |
208 | * This must be called only on pages that have | |
209 | * been verified to be in the swap cache and locked. | |
210 | * It will never put the page into the free list, | |
211 | * the caller has a reference on the page. | |
212 | */ | |
213 | void delete_from_swap_cache(struct page *page) | |
214 | { | |
215 | swp_entry_t entry; | |
33806f06 | 216 | struct address_space *address_space; |
1da177e4 | 217 | |
4c21e2f2 | 218 | entry.val = page_private(page); |
1da177e4 | 219 | |
33806f06 SL |
220 | address_space = swap_address_space(entry); |
221 | spin_lock_irq(&address_space->tree_lock); | |
1da177e4 | 222 | __delete_from_swap_cache(page); |
33806f06 | 223 | spin_unlock_irq(&address_space->tree_lock); |
1da177e4 | 224 | |
cb4b86ba | 225 | swapcache_free(entry, page); |
1da177e4 LT |
226 | page_cache_release(page); |
227 | } | |
228 | ||
1da177e4 LT |
229 | /* |
230 | * If we are the only user, then try to free up the swap cache. | |
231 | * | |
232 | * Its ok to check for PageSwapCache without the page lock | |
a2c43eed HD |
233 | * here because we are going to recheck again inside |
234 | * try_to_free_swap() _with_ the lock. | |
1da177e4 LT |
235 | * - Marcelo |
236 | */ | |
237 | static inline void free_swap_cache(struct page *page) | |
238 | { | |
a2c43eed HD |
239 | if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { |
240 | try_to_free_swap(page); | |
1da177e4 LT |
241 | unlock_page(page); |
242 | } | |
243 | } | |
244 | ||
245 | /* | |
246 | * Perform a free_page(), also freeing any swap cache associated with | |
b8072f09 | 247 | * this page if it is the last user of the page. |
1da177e4 LT |
248 | */ |
249 | void free_page_and_swap_cache(struct page *page) | |
250 | { | |
251 | free_swap_cache(page); | |
252 | page_cache_release(page); | |
253 | } | |
254 | ||
255 | /* | |
256 | * Passed an array of pages, drop them all from swapcache and then release | |
257 | * them. They are removed from the LRU and freed if this is their last use. | |
258 | */ | |
259 | void free_pages_and_swap_cache(struct page **pages, int nr) | |
260 | { | |
1da177e4 LT |
261 | struct page **pagep = pages; |
262 | ||
263 | lru_add_drain(); | |
264 | while (nr) { | |
c484d410 | 265 | int todo = min(nr, PAGEVEC_SIZE); |
1da177e4 LT |
266 | int i; |
267 | ||
268 | for (i = 0; i < todo; i++) | |
269 | free_swap_cache(pagep[i]); | |
270 | release_pages(pagep, todo, 0); | |
271 | pagep += todo; | |
272 | nr -= todo; | |
273 | } | |
274 | } | |
275 | ||
276 | /* | |
277 | * Lookup a swap entry in the swap cache. A found page will be returned | |
278 | * unlocked and with its refcount incremented - we rely on the kernel | |
279 | * lock getting page table operations atomic even if we drop the page | |
280 | * lock before returning. | |
281 | */ | |
282 | struct page * lookup_swap_cache(swp_entry_t entry) | |
283 | { | |
284 | struct page *page; | |
285 | ||
33806f06 | 286 | page = find_get_page(swap_address_space(entry), entry.val); |
1da177e4 LT |
287 | |
288 | if (page) | |
289 | INC_CACHE_INFO(find_success); | |
290 | ||
291 | INC_CACHE_INFO(find_total); | |
292 | return page; | |
293 | } | |
294 | ||
295 | /* | |
296 | * Locate a page of swap in physical memory, reserving swap cache space | |
297 | * and reading the disk if it is not already cached. | |
298 | * A failure return means that either the page allocation failed or that | |
299 | * the swap entry is no longer in use. | |
300 | */ | |
02098fea | 301 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
1da177e4 LT |
302 | struct vm_area_struct *vma, unsigned long addr) |
303 | { | |
304 | struct page *found_page, *new_page = NULL; | |
305 | int err; | |
306 | ||
307 | do { | |
308 | /* | |
309 | * First check the swap cache. Since this is normally | |
310 | * called after lookup_swap_cache() failed, re-calling | |
311 | * that would confuse statistics. | |
312 | */ | |
33806f06 SL |
313 | found_page = find_get_page(swap_address_space(entry), |
314 | entry.val); | |
1da177e4 LT |
315 | if (found_page) |
316 | break; | |
317 | ||
318 | /* | |
319 | * Get a new page to read into from swap. | |
320 | */ | |
321 | if (!new_page) { | |
02098fea | 322 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
1da177e4 LT |
323 | if (!new_page) |
324 | break; /* Out of memory */ | |
325 | } | |
326 | ||
31a56396 DN |
327 | /* |
328 | * call radix_tree_preload() while we can wait. | |
329 | */ | |
330 | err = radix_tree_preload(gfp_mask & GFP_KERNEL); | |
331 | if (err) | |
332 | break; | |
333 | ||
f000944d HD |
334 | /* |
335 | * Swap entry may have been freed since our caller observed it. | |
336 | */ | |
355cfa73 | 337 | err = swapcache_prepare(entry); |
31a56396 DN |
338 | if (err == -EEXIST) { /* seems racy */ |
339 | radix_tree_preload_end(); | |
355cfa73 | 340 | continue; |
31a56396 DN |
341 | } |
342 | if (err) { /* swp entry is obsolete ? */ | |
343 | radix_tree_preload_end(); | |
f000944d | 344 | break; |
31a56396 | 345 | } |
f000944d | 346 | |
2ca4532a | 347 | /* May fail (-ENOMEM) if radix-tree node allocation failed. */ |
f45840b5 | 348 | __set_page_locked(new_page); |
b2e18538 | 349 | SetPageSwapBacked(new_page); |
31a56396 | 350 | err = __add_to_swap_cache(new_page, entry); |
529ae9aa | 351 | if (likely(!err)) { |
31a56396 | 352 | radix_tree_preload_end(); |
1da177e4 LT |
353 | /* |
354 | * Initiate read into locked page and return. | |
355 | */ | |
c5fdae46 | 356 | lru_cache_add_anon(new_page); |
aca8bf32 | 357 | swap_readpage(new_page); |
1da177e4 LT |
358 | return new_page; |
359 | } | |
31a56396 | 360 | radix_tree_preload_end(); |
b2e18538 | 361 | ClearPageSwapBacked(new_page); |
f45840b5 | 362 | __clear_page_locked(new_page); |
2ca4532a DN |
363 | /* |
364 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely | |
365 | * clear SWAP_HAS_CACHE flag. | |
366 | */ | |
cb4b86ba | 367 | swapcache_free(entry, NULL); |
f000944d | 368 | } while (err != -ENOMEM); |
1da177e4 LT |
369 | |
370 | if (new_page) | |
371 | page_cache_release(new_page); | |
372 | return found_page; | |
373 | } | |
46017e95 HD |
374 | |
375 | /** | |
376 | * swapin_readahead - swap in pages in hope we need them soon | |
377 | * @entry: swap entry of this memory | |
7682486b | 378 | * @gfp_mask: memory allocation flags |
46017e95 HD |
379 | * @vma: user vma this address belongs to |
380 | * @addr: target address for mempolicy | |
381 | * | |
382 | * Returns the struct page for entry and addr, after queueing swapin. | |
383 | * | |
384 | * Primitive swap readahead code. We simply read an aligned block of | |
385 | * (1 << page_cluster) entries in the swap area. This method is chosen | |
386 | * because it doesn't cost us any seek time. We also make sure to queue | |
387 | * the 'original' request together with the readahead ones... | |
388 | * | |
389 | * This has been extended to use the NUMA policies from the mm triggering | |
390 | * the readahead. | |
391 | * | |
392 | * Caller must hold down_read on the vma->vm_mm if vma is not NULL. | |
393 | */ | |
02098fea | 394 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
46017e95 HD |
395 | struct vm_area_struct *vma, unsigned long addr) |
396 | { | |
46017e95 | 397 | struct page *page; |
67f96aa2 RR |
398 | unsigned long offset = swp_offset(entry); |
399 | unsigned long start_offset, end_offset; | |
400 | unsigned long mask = (1UL << page_cluster) - 1; | |
3fb5c298 | 401 | struct blk_plug plug; |
46017e95 | 402 | |
67f96aa2 RR |
403 | /* Read a page_cluster sized and aligned cluster around offset. */ |
404 | start_offset = offset & ~mask; | |
405 | end_offset = offset | mask; | |
406 | if (!start_offset) /* First page is swap header. */ | |
407 | start_offset++; | |
408 | ||
3fb5c298 | 409 | blk_start_plug(&plug); |
67f96aa2 | 410 | for (offset = start_offset; offset <= end_offset ; offset++) { |
46017e95 HD |
411 | /* Ok, do the async read-ahead now */ |
412 | page = read_swap_cache_async(swp_entry(swp_type(entry), offset), | |
02098fea | 413 | gfp_mask, vma, addr); |
46017e95 | 414 | if (!page) |
67f96aa2 | 415 | continue; |
46017e95 HD |
416 | page_cache_release(page); |
417 | } | |
3fb5c298 CE |
418 | blk_finish_plug(&plug); |
419 | ||
46017e95 | 420 | lru_add_drain(); /* Push any new pages onto the LRU now */ |
02098fea | 421 | return read_swap_cache_async(entry, gfp_mask, vma, addr); |
46017e95 | 422 | } |