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> | |
5a0e3ad6 | 11 | #include <linux/gfp.h> |
1da177e4 LT |
12 | #include <linux/kernel_stat.h> |
13 | #include <linux/swap.h> | |
46017e95 | 14 | #include <linux/swapops.h> |
1da177e4 LT |
15 | #include <linux/init.h> |
16 | #include <linux/pagemap.h> | |
17 | #include <linux/buffer_head.h> | |
18 | #include <linux/backing-dev.h> | |
c484d410 | 19 | #include <linux/pagevec.h> |
b20a3503 | 20 | #include <linux/migrate.h> |
8c7c6e34 | 21 | #include <linux/page_cgroup.h> |
1da177e4 LT |
22 | |
23 | #include <asm/pgtable.h> | |
24 | ||
25 | /* | |
26 | * swapper_space is a fiction, retained to simplify the path through | |
2706a1b8 | 27 | * vmscan's shrink_page_list, to make sync_page look nicer, and to allow |
1da177e4 LT |
28 | * future use of radix_tree tags in the swap cache. |
29 | */ | |
f5e54d6e | 30 | static const struct address_space_operations swap_aops = { |
1da177e4 LT |
31 | .writepage = swap_writepage, |
32 | .sync_page = block_sync_page, | |
33 | .set_page_dirty = __set_page_dirty_nobuffers, | |
e965f963 | 34 | .migratepage = migrate_page, |
1da177e4 LT |
35 | }; |
36 | ||
37 | static struct backing_dev_info swap_backing_dev_info = { | |
d993831f | 38 | .name = "swap", |
4f98a2fe | 39 | .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED, |
1da177e4 LT |
40 | .unplug_io_fn = swap_unplug_io_fn, |
41 | }; | |
42 | ||
43 | struct address_space swapper_space = { | |
44 | .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN), | |
19fd6231 | 45 | .tree_lock = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock), |
1da177e4 LT |
46 | .a_ops = &swap_aops, |
47 | .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear), | |
48 | .backing_dev_info = &swap_backing_dev_info, | |
49 | }; | |
1da177e4 LT |
50 | |
51 | #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) | |
52 | ||
53 | static struct { | |
54 | unsigned long add_total; | |
55 | unsigned long del_total; | |
56 | unsigned long find_success; | |
57 | unsigned long find_total; | |
1da177e4 LT |
58 | } swap_cache_info; |
59 | ||
60 | void show_swap_cache_info(void) | |
61 | { | |
2c97b7fc JW |
62 | printk("%lu pages in swap cache\n", total_swapcache_pages); |
63 | printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n", | |
1da177e4 | 64 | swap_cache_info.add_total, swap_cache_info.del_total, |
bb63be0a | 65 | swap_cache_info.find_success, swap_cache_info.find_total); |
07279cdf | 66 | printk("Free swap = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10)); |
1da177e4 LT |
67 | printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); |
68 | } | |
69 | ||
70 | /* | |
31a56396 | 71 | * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space, |
1da177e4 LT |
72 | * but sets SwapCache flag and private instead of mapping and index. |
73 | */ | |
31a56396 | 74 | static int __add_to_swap_cache(struct page *page, swp_entry_t entry) |
1da177e4 LT |
75 | { |
76 | int error; | |
77 | ||
51726b12 HD |
78 | VM_BUG_ON(!PageLocked(page)); |
79 | VM_BUG_ON(PageSwapCache(page)); | |
80 | VM_BUG_ON(!PageSwapBacked(page)); | |
81 | ||
31a56396 DN |
82 | page_cache_get(page); |
83 | SetPageSwapCache(page); | |
84 | set_page_private(page, entry.val); | |
85 | ||
86 | spin_lock_irq(&swapper_space.tree_lock); | |
87 | error = radix_tree_insert(&swapper_space.page_tree, entry.val, page); | |
88 | if (likely(!error)) { | |
89 | total_swapcache_pages++; | |
90 | __inc_zone_page_state(page, NR_FILE_PAGES); | |
91 | INC_CACHE_INFO(add_total); | |
92 | } | |
93 | spin_unlock_irq(&swapper_space.tree_lock); | |
94 | ||
95 | if (unlikely(error)) { | |
2ca4532a DN |
96 | /* |
97 | * Only the context which have set SWAP_HAS_CACHE flag | |
98 | * would call add_to_swap_cache(). | |
99 | * So add_to_swap_cache() doesn't returns -EEXIST. | |
100 | */ | |
101 | VM_BUG_ON(error == -EEXIST); | |
31a56396 DN |
102 | set_page_private(page, 0UL); |
103 | ClearPageSwapCache(page); | |
104 | page_cache_release(page); | |
105 | } | |
106 | ||
107 | return error; | |
108 | } | |
109 | ||
110 | ||
111 | int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) | |
112 | { | |
113 | int error; | |
114 | ||
35c754d7 BS |
115 | error = radix_tree_preload(gfp_mask); |
116 | if (!error) { | |
31a56396 | 117 | error = __add_to_swap_cache(page, entry); |
1da177e4 | 118 | radix_tree_preload_end(); |
fa1de900 | 119 | } |
1da177e4 LT |
120 | return error; |
121 | } | |
122 | ||
1da177e4 LT |
123 | /* |
124 | * This must be called only on pages that have | |
125 | * been verified to be in the swap cache. | |
126 | */ | |
127 | void __delete_from_swap_cache(struct page *page) | |
128 | { | |
51726b12 HD |
129 | VM_BUG_ON(!PageLocked(page)); |
130 | VM_BUG_ON(!PageSwapCache(page)); | |
131 | VM_BUG_ON(PageWriteback(page)); | |
1da177e4 | 132 | |
4c21e2f2 HD |
133 | radix_tree_delete(&swapper_space.page_tree, page_private(page)); |
134 | set_page_private(page, 0); | |
1da177e4 LT |
135 | ClearPageSwapCache(page); |
136 | total_swapcache_pages--; | |
347ce434 | 137 | __dec_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
138 | INC_CACHE_INFO(del_total); |
139 | } | |
140 | ||
141 | /** | |
142 | * add_to_swap - allocate swap space for a page | |
143 | * @page: page we want to move to swap | |
144 | * | |
145 | * Allocate swap space for the page and add the page to the | |
146 | * swap cache. Caller needs to hold the page lock. | |
147 | */ | |
ac47b003 | 148 | int add_to_swap(struct page *page) |
1da177e4 LT |
149 | { |
150 | swp_entry_t entry; | |
1da177e4 LT |
151 | int err; |
152 | ||
51726b12 HD |
153 | VM_BUG_ON(!PageLocked(page)); |
154 | VM_BUG_ON(!PageUptodate(page)); | |
1da177e4 | 155 | |
2ca4532a DN |
156 | entry = get_swap_page(); |
157 | if (!entry.val) | |
158 | return 0; | |
159 | ||
160 | /* | |
161 | * Radix-tree node allocations from PF_MEMALLOC contexts could | |
162 | * completely exhaust the page allocator. __GFP_NOMEMALLOC | |
163 | * stops emergency reserves from being allocated. | |
164 | * | |
165 | * TODO: this could cause a theoretical memory reclaim | |
166 | * deadlock in the swap out path. | |
167 | */ | |
168 | /* | |
169 | * Add it to the swap cache and mark it dirty | |
170 | */ | |
171 | err = add_to_swap_cache(page, entry, | |
172 | __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); | |
173 | ||
174 | if (!err) { /* Success */ | |
175 | SetPageDirty(page); | |
176 | return 1; | |
177 | } else { /* -ENOMEM radix-tree allocation failure */ | |
bd53b714 | 178 | /* |
2ca4532a DN |
179 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
180 | * clear SWAP_HAS_CACHE flag. | |
1da177e4 | 181 | */ |
2ca4532a DN |
182 | swapcache_free(entry, NULL); |
183 | return 0; | |
1da177e4 LT |
184 | } |
185 | } | |
186 | ||
187 | /* | |
188 | * This must be called only on pages that have | |
189 | * been verified to be in the swap cache and locked. | |
190 | * It will never put the page into the free list, | |
191 | * the caller has a reference on the page. | |
192 | */ | |
193 | void delete_from_swap_cache(struct page *page) | |
194 | { | |
195 | swp_entry_t entry; | |
196 | ||
4c21e2f2 | 197 | entry.val = page_private(page); |
1da177e4 | 198 | |
19fd6231 | 199 | spin_lock_irq(&swapper_space.tree_lock); |
1da177e4 | 200 | __delete_from_swap_cache(page); |
19fd6231 | 201 | spin_unlock_irq(&swapper_space.tree_lock); |
1da177e4 | 202 | |
cb4b86ba | 203 | swapcache_free(entry, page); |
1da177e4 LT |
204 | page_cache_release(page); |
205 | } | |
206 | ||
1da177e4 LT |
207 | /* |
208 | * If we are the only user, then try to free up the swap cache. | |
209 | * | |
210 | * Its ok to check for PageSwapCache without the page lock | |
a2c43eed HD |
211 | * here because we are going to recheck again inside |
212 | * try_to_free_swap() _with_ the lock. | |
1da177e4 LT |
213 | * - Marcelo |
214 | */ | |
215 | static inline void free_swap_cache(struct page *page) | |
216 | { | |
a2c43eed HD |
217 | if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { |
218 | try_to_free_swap(page); | |
1da177e4 LT |
219 | unlock_page(page); |
220 | } | |
221 | } | |
222 | ||
223 | /* | |
224 | * Perform a free_page(), also freeing any swap cache associated with | |
b8072f09 | 225 | * this page if it is the last user of the page. |
1da177e4 LT |
226 | */ |
227 | void free_page_and_swap_cache(struct page *page) | |
228 | { | |
229 | free_swap_cache(page); | |
230 | page_cache_release(page); | |
231 | } | |
232 | ||
233 | /* | |
234 | * Passed an array of pages, drop them all from swapcache and then release | |
235 | * them. They are removed from the LRU and freed if this is their last use. | |
236 | */ | |
237 | void free_pages_and_swap_cache(struct page **pages, int nr) | |
238 | { | |
1da177e4 LT |
239 | struct page **pagep = pages; |
240 | ||
241 | lru_add_drain(); | |
242 | while (nr) { | |
c484d410 | 243 | int todo = min(nr, PAGEVEC_SIZE); |
1da177e4 LT |
244 | int i; |
245 | ||
246 | for (i = 0; i < todo; i++) | |
247 | free_swap_cache(pagep[i]); | |
248 | release_pages(pagep, todo, 0); | |
249 | pagep += todo; | |
250 | nr -= todo; | |
251 | } | |
252 | } | |
253 | ||
254 | /* | |
255 | * Lookup a swap entry in the swap cache. A found page will be returned | |
256 | * unlocked and with its refcount incremented - we rely on the kernel | |
257 | * lock getting page table operations atomic even if we drop the page | |
258 | * lock before returning. | |
259 | */ | |
260 | struct page * lookup_swap_cache(swp_entry_t entry) | |
261 | { | |
262 | struct page *page; | |
263 | ||
264 | page = find_get_page(&swapper_space, entry.val); | |
265 | ||
266 | if (page) | |
267 | INC_CACHE_INFO(find_success); | |
268 | ||
269 | INC_CACHE_INFO(find_total); | |
270 | return page; | |
271 | } | |
272 | ||
273 | /* | |
274 | * Locate a page of swap in physical memory, reserving swap cache space | |
275 | * and reading the disk if it is not already cached. | |
276 | * A failure return means that either the page allocation failed or that | |
277 | * the swap entry is no longer in use. | |
278 | */ | |
02098fea | 279 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
1da177e4 LT |
280 | struct vm_area_struct *vma, unsigned long addr) |
281 | { | |
282 | struct page *found_page, *new_page = NULL; | |
283 | int err; | |
284 | ||
285 | do { | |
286 | /* | |
287 | * First check the swap cache. Since this is normally | |
288 | * called after lookup_swap_cache() failed, re-calling | |
289 | * that would confuse statistics. | |
290 | */ | |
291 | found_page = find_get_page(&swapper_space, entry.val); | |
292 | if (found_page) | |
293 | break; | |
294 | ||
295 | /* | |
296 | * Get a new page to read into from swap. | |
297 | */ | |
298 | if (!new_page) { | |
02098fea | 299 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
1da177e4 LT |
300 | if (!new_page) |
301 | break; /* Out of memory */ | |
302 | } | |
303 | ||
31a56396 DN |
304 | /* |
305 | * call radix_tree_preload() while we can wait. | |
306 | */ | |
307 | err = radix_tree_preload(gfp_mask & GFP_KERNEL); | |
308 | if (err) | |
309 | break; | |
310 | ||
f000944d HD |
311 | /* |
312 | * Swap entry may have been freed since our caller observed it. | |
313 | */ | |
355cfa73 | 314 | err = swapcache_prepare(entry); |
31a56396 DN |
315 | if (err == -EEXIST) { /* seems racy */ |
316 | radix_tree_preload_end(); | |
355cfa73 | 317 | continue; |
31a56396 DN |
318 | } |
319 | if (err) { /* swp entry is obsolete ? */ | |
320 | radix_tree_preload_end(); | |
f000944d | 321 | break; |
31a56396 | 322 | } |
f000944d | 323 | |
2ca4532a | 324 | /* May fail (-ENOMEM) if radix-tree node allocation failed. */ |
f45840b5 | 325 | __set_page_locked(new_page); |
b2e18538 | 326 | SetPageSwapBacked(new_page); |
31a56396 | 327 | err = __add_to_swap_cache(new_page, entry); |
529ae9aa | 328 | if (likely(!err)) { |
31a56396 | 329 | radix_tree_preload_end(); |
1da177e4 LT |
330 | /* |
331 | * Initiate read into locked page and return. | |
332 | */ | |
c5fdae46 | 333 | lru_cache_add_anon(new_page); |
aca8bf32 | 334 | swap_readpage(new_page); |
1da177e4 LT |
335 | return new_page; |
336 | } | |
31a56396 | 337 | radix_tree_preload_end(); |
b2e18538 | 338 | ClearPageSwapBacked(new_page); |
f45840b5 | 339 | __clear_page_locked(new_page); |
2ca4532a DN |
340 | /* |
341 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely | |
342 | * clear SWAP_HAS_CACHE flag. | |
343 | */ | |
cb4b86ba | 344 | swapcache_free(entry, NULL); |
f000944d | 345 | } while (err != -ENOMEM); |
1da177e4 LT |
346 | |
347 | if (new_page) | |
348 | page_cache_release(new_page); | |
349 | return found_page; | |
350 | } | |
46017e95 HD |
351 | |
352 | /** | |
353 | * swapin_readahead - swap in pages in hope we need them soon | |
354 | * @entry: swap entry of this memory | |
7682486b | 355 | * @gfp_mask: memory allocation flags |
46017e95 HD |
356 | * @vma: user vma this address belongs to |
357 | * @addr: target address for mempolicy | |
358 | * | |
359 | * Returns the struct page for entry and addr, after queueing swapin. | |
360 | * | |
361 | * Primitive swap readahead code. We simply read an aligned block of | |
362 | * (1 << page_cluster) entries in the swap area. This method is chosen | |
363 | * because it doesn't cost us any seek time. We also make sure to queue | |
364 | * the 'original' request together with the readahead ones... | |
365 | * | |
366 | * This has been extended to use the NUMA policies from the mm triggering | |
367 | * the readahead. | |
368 | * | |
369 | * Caller must hold down_read on the vma->vm_mm if vma is not NULL. | |
370 | */ | |
02098fea | 371 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
46017e95 HD |
372 | struct vm_area_struct *vma, unsigned long addr) |
373 | { | |
374 | int nr_pages; | |
375 | struct page *page; | |
376 | unsigned long offset; | |
377 | unsigned long end_offset; | |
378 | ||
379 | /* | |
380 | * Get starting offset for readaround, and number of pages to read. | |
381 | * Adjust starting address by readbehind (for NUMA interleave case)? | |
382 | * No, it's very unlikely that swap layout would follow vma layout, | |
383 | * more likely that neighbouring swap pages came from the same node: | |
384 | * so use the same "addr" to choose the same node for each swap read. | |
385 | */ | |
386 | nr_pages = valid_swaphandles(entry, &offset); | |
387 | for (end_offset = offset + nr_pages; offset < end_offset; offset++) { | |
388 | /* Ok, do the async read-ahead now */ | |
389 | page = read_swap_cache_async(swp_entry(swp_type(entry), offset), | |
02098fea | 390 | gfp_mask, vma, addr); |
46017e95 HD |
391 | if (!page) |
392 | break; | |
393 | page_cache_release(page); | |
394 | } | |
395 | lru_add_drain(); /* Push any new pages onto the LRU now */ | |
02098fea | 396 | return read_swap_cache_async(entry, gfp_mask, vma, addr); |
46017e95 | 397 | } |