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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> |
c484d410 | 17 | #include <linux/pagevec.h> |
b20a3503 | 18 | #include <linux/migrate.h> |
8c7c6e34 | 19 | #include <linux/page_cgroup.h> |
1da177e4 LT |
20 | |
21 | #include <asm/pgtable.h> | |
22 | ||
23 | /* | |
24 | * swapper_space is a fiction, retained to simplify the path through | |
7eaceacc | 25 | * vmscan's shrink_page_list. |
1da177e4 | 26 | */ |
f5e54d6e | 27 | static const struct address_space_operations swap_aops = { |
1da177e4 | 28 | .writepage = swap_writepage, |
1da177e4 | 29 | .set_page_dirty = __set_page_dirty_nobuffers, |
e965f963 | 30 | .migratepage = migrate_page, |
1da177e4 LT |
31 | }; |
32 | ||
33 | static struct backing_dev_info swap_backing_dev_info = { | |
d993831f | 34 | .name = "swap", |
4f98a2fe | 35 | .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED, |
1da177e4 LT |
36 | }; |
37 | ||
38 | struct address_space swapper_space = { | |
39 | .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN), | |
19fd6231 | 40 | .tree_lock = __SPIN_LOCK_UNLOCKED(swapper_space.tree_lock), |
1da177e4 LT |
41 | .a_ops = &swap_aops, |
42 | .i_mmap_nonlinear = LIST_HEAD_INIT(swapper_space.i_mmap_nonlinear), | |
43 | .backing_dev_info = &swap_backing_dev_info, | |
44 | }; | |
1da177e4 LT |
45 | |
46 | #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) | |
47 | ||
48 | static struct { | |
49 | unsigned long add_total; | |
50 | unsigned long del_total; | |
51 | unsigned long find_success; | |
52 | unsigned long find_total; | |
1da177e4 LT |
53 | } swap_cache_info; |
54 | ||
55 | void show_swap_cache_info(void) | |
56 | { | |
2c97b7fc JW |
57 | printk("%lu pages in swap cache\n", total_swapcache_pages); |
58 | printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n", | |
1da177e4 | 59 | swap_cache_info.add_total, swap_cache_info.del_total, |
bb63be0a | 60 | swap_cache_info.find_success, swap_cache_info.find_total); |
07279cdf | 61 | printk("Free swap = %ldkB\n", nr_swap_pages << (PAGE_SHIFT - 10)); |
1da177e4 LT |
62 | printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); |
63 | } | |
64 | ||
65 | /* | |
31a56396 | 66 | * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space, |
1da177e4 LT |
67 | * but sets SwapCache flag and private instead of mapping and index. |
68 | */ | |
31a56396 | 69 | static int __add_to_swap_cache(struct page *page, swp_entry_t entry) |
1da177e4 LT |
70 | { |
71 | int error; | |
72 | ||
51726b12 HD |
73 | VM_BUG_ON(!PageLocked(page)); |
74 | VM_BUG_ON(PageSwapCache(page)); | |
75 | VM_BUG_ON(!PageSwapBacked(page)); | |
76 | ||
31a56396 DN |
77 | page_cache_get(page); |
78 | SetPageSwapCache(page); | |
79 | set_page_private(page, entry.val); | |
80 | ||
81 | spin_lock_irq(&swapper_space.tree_lock); | |
82 | error = radix_tree_insert(&swapper_space.page_tree, entry.val, page); | |
83 | if (likely(!error)) { | |
84 | total_swapcache_pages++; | |
85 | __inc_zone_page_state(page, NR_FILE_PAGES); | |
86 | INC_CACHE_INFO(add_total); | |
87 | } | |
88 | spin_unlock_irq(&swapper_space.tree_lock); | |
89 | ||
90 | if (unlikely(error)) { | |
2ca4532a DN |
91 | /* |
92 | * Only the context which have set SWAP_HAS_CACHE flag | |
93 | * would call add_to_swap_cache(). | |
94 | * So add_to_swap_cache() doesn't returns -EEXIST. | |
95 | */ | |
96 | VM_BUG_ON(error == -EEXIST); | |
31a56396 DN |
97 | set_page_private(page, 0UL); |
98 | ClearPageSwapCache(page); | |
99 | page_cache_release(page); | |
100 | } | |
101 | ||
102 | return error; | |
103 | } | |
104 | ||
105 | ||
106 | int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) | |
107 | { | |
108 | int error; | |
109 | ||
35c754d7 BS |
110 | error = radix_tree_preload(gfp_mask); |
111 | if (!error) { | |
31a56396 | 112 | error = __add_to_swap_cache(page, entry); |
1da177e4 | 113 | radix_tree_preload_end(); |
fa1de900 | 114 | } |
1da177e4 LT |
115 | return error; |
116 | } | |
117 | ||
1da177e4 LT |
118 | /* |
119 | * This must be called only on pages that have | |
120 | * been verified to be in the swap cache. | |
121 | */ | |
122 | void __delete_from_swap_cache(struct page *page) | |
123 | { | |
51726b12 HD |
124 | VM_BUG_ON(!PageLocked(page)); |
125 | VM_BUG_ON(!PageSwapCache(page)); | |
126 | VM_BUG_ON(PageWriteback(page)); | |
1da177e4 | 127 | |
4c21e2f2 HD |
128 | radix_tree_delete(&swapper_space.page_tree, page_private(page)); |
129 | set_page_private(page, 0); | |
1da177e4 LT |
130 | ClearPageSwapCache(page); |
131 | total_swapcache_pages--; | |
347ce434 | 132 | __dec_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
133 | INC_CACHE_INFO(del_total); |
134 | } | |
135 | ||
136 | /** | |
137 | * add_to_swap - allocate swap space for a page | |
138 | * @page: page we want to move to swap | |
139 | * | |
140 | * Allocate swap space for the page and add the page to the | |
141 | * swap cache. Caller needs to hold the page lock. | |
142 | */ | |
ac47b003 | 143 | int add_to_swap(struct page *page) |
1da177e4 LT |
144 | { |
145 | swp_entry_t entry; | |
1da177e4 LT |
146 | int err; |
147 | ||
51726b12 HD |
148 | VM_BUG_ON(!PageLocked(page)); |
149 | VM_BUG_ON(!PageUptodate(page)); | |
1da177e4 | 150 | |
2ca4532a DN |
151 | entry = get_swap_page(); |
152 | if (!entry.val) | |
153 | return 0; | |
154 | ||
3f04f62f AA |
155 | if (unlikely(PageTransHuge(page))) |
156 | if (unlikely(split_huge_page(page))) { | |
157 | swapcache_free(entry, NULL); | |
158 | return 0; | |
159 | } | |
160 | ||
2ca4532a DN |
161 | /* |
162 | * Radix-tree node allocations from PF_MEMALLOC contexts could | |
163 | * completely exhaust the page allocator. __GFP_NOMEMALLOC | |
164 | * stops emergency reserves from being allocated. | |
165 | * | |
166 | * TODO: this could cause a theoretical memory reclaim | |
167 | * deadlock in the swap out path. | |
168 | */ | |
169 | /* | |
170 | * Add it to the swap cache and mark it dirty | |
171 | */ | |
172 | err = add_to_swap_cache(page, entry, | |
173 | __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); | |
174 | ||
175 | if (!err) { /* Success */ | |
176 | SetPageDirty(page); | |
177 | return 1; | |
178 | } else { /* -ENOMEM radix-tree allocation failure */ | |
bd53b714 | 179 | /* |
2ca4532a DN |
180 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
181 | * clear SWAP_HAS_CACHE flag. | |
1da177e4 | 182 | */ |
2ca4532a DN |
183 | swapcache_free(entry, NULL); |
184 | return 0; | |
1da177e4 LT |
185 | } |
186 | } | |
187 | ||
188 | /* | |
189 | * This must be called only on pages that have | |
190 | * been verified to be in the swap cache and locked. | |
191 | * It will never put the page into the free list, | |
192 | * the caller has a reference on the page. | |
193 | */ | |
194 | void delete_from_swap_cache(struct page *page) | |
195 | { | |
196 | swp_entry_t entry; | |
197 | ||
4c21e2f2 | 198 | entry.val = page_private(page); |
1da177e4 | 199 | |
19fd6231 | 200 | spin_lock_irq(&swapper_space.tree_lock); |
1da177e4 | 201 | __delete_from_swap_cache(page); |
19fd6231 | 202 | spin_unlock_irq(&swapper_space.tree_lock); |
1da177e4 | 203 | |
cb4b86ba | 204 | swapcache_free(entry, page); |
1da177e4 LT |
205 | page_cache_release(page); |
206 | } | |
207 | ||
1da177e4 LT |
208 | /* |
209 | * If we are the only user, then try to free up the swap cache. | |
210 | * | |
211 | * Its ok to check for PageSwapCache without the page lock | |
a2c43eed HD |
212 | * here because we are going to recheck again inside |
213 | * try_to_free_swap() _with_ the lock. | |
1da177e4 LT |
214 | * - Marcelo |
215 | */ | |
216 | static inline void free_swap_cache(struct page *page) | |
217 | { | |
a2c43eed HD |
218 | if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { |
219 | try_to_free_swap(page); | |
1da177e4 LT |
220 | unlock_page(page); |
221 | } | |
222 | } | |
223 | ||
224 | /* | |
225 | * Perform a free_page(), also freeing any swap cache associated with | |
b8072f09 | 226 | * this page if it is the last user of the page. |
1da177e4 LT |
227 | */ |
228 | void free_page_and_swap_cache(struct page *page) | |
229 | { | |
230 | free_swap_cache(page); | |
231 | page_cache_release(page); | |
232 | } | |
233 | ||
234 | /* | |
235 | * Passed an array of pages, drop them all from swapcache and then release | |
236 | * them. They are removed from the LRU and freed if this is their last use. | |
237 | */ | |
238 | void free_pages_and_swap_cache(struct page **pages, int nr) | |
239 | { | |
1da177e4 LT |
240 | struct page **pagep = pages; |
241 | ||
242 | lru_add_drain(); | |
243 | while (nr) { | |
c484d410 | 244 | int todo = min(nr, PAGEVEC_SIZE); |
1da177e4 LT |
245 | int i; |
246 | ||
247 | for (i = 0; i < todo; i++) | |
248 | free_swap_cache(pagep[i]); | |
249 | release_pages(pagep, todo, 0); | |
250 | pagep += todo; | |
251 | nr -= todo; | |
252 | } | |
253 | } | |
254 | ||
255 | /* | |
256 | * Lookup a swap entry in the swap cache. A found page will be returned | |
257 | * unlocked and with its refcount incremented - we rely on the kernel | |
258 | * lock getting page table operations atomic even if we drop the page | |
259 | * lock before returning. | |
260 | */ | |
261 | struct page * lookup_swap_cache(swp_entry_t entry) | |
262 | { | |
263 | struct page *page; | |
264 | ||
265 | page = find_get_page(&swapper_space, entry.val); | |
266 | ||
267 | if (page) | |
268 | INC_CACHE_INFO(find_success); | |
269 | ||
270 | INC_CACHE_INFO(find_total); | |
271 | return page; | |
272 | } | |
273 | ||
274 | /* | |
275 | * Locate a page of swap in physical memory, reserving swap cache space | |
276 | * and reading the disk if it is not already cached. | |
277 | * A failure return means that either the page allocation failed or that | |
278 | * the swap entry is no longer in use. | |
279 | */ | |
02098fea | 280 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
1da177e4 LT |
281 | struct vm_area_struct *vma, unsigned long addr) |
282 | { | |
283 | struct page *found_page, *new_page = NULL; | |
284 | int err; | |
285 | ||
286 | do { | |
287 | /* | |
288 | * First check the swap cache. Since this is normally | |
289 | * called after lookup_swap_cache() failed, re-calling | |
290 | * that would confuse statistics. | |
291 | */ | |
292 | found_page = find_get_page(&swapper_space, entry.val); | |
293 | if (found_page) | |
294 | break; | |
295 | ||
296 | /* | |
297 | * Get a new page to read into from swap. | |
298 | */ | |
299 | if (!new_page) { | |
02098fea | 300 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
1da177e4 LT |
301 | if (!new_page) |
302 | break; /* Out of memory */ | |
303 | } | |
304 | ||
31a56396 DN |
305 | /* |
306 | * call radix_tree_preload() while we can wait. | |
307 | */ | |
308 | err = radix_tree_preload(gfp_mask & GFP_KERNEL); | |
309 | if (err) | |
310 | break; | |
311 | ||
f000944d HD |
312 | /* |
313 | * Swap entry may have been freed since our caller observed it. | |
314 | */ | |
355cfa73 | 315 | err = swapcache_prepare(entry); |
31a56396 DN |
316 | if (err == -EEXIST) { /* seems racy */ |
317 | radix_tree_preload_end(); | |
355cfa73 | 318 | continue; |
31a56396 DN |
319 | } |
320 | if (err) { /* swp entry is obsolete ? */ | |
321 | radix_tree_preload_end(); | |
f000944d | 322 | break; |
31a56396 | 323 | } |
f000944d | 324 | |
2ca4532a | 325 | /* May fail (-ENOMEM) if radix-tree node allocation failed. */ |
f45840b5 | 326 | __set_page_locked(new_page); |
b2e18538 | 327 | SetPageSwapBacked(new_page); |
31a56396 | 328 | err = __add_to_swap_cache(new_page, entry); |
529ae9aa | 329 | if (likely(!err)) { |
31a56396 | 330 | radix_tree_preload_end(); |
1da177e4 LT |
331 | /* |
332 | * Initiate read into locked page and return. | |
333 | */ | |
c5fdae46 | 334 | lru_cache_add_anon(new_page); |
aca8bf32 | 335 | swap_readpage(new_page); |
1da177e4 LT |
336 | return new_page; |
337 | } | |
31a56396 | 338 | radix_tree_preload_end(); |
b2e18538 | 339 | ClearPageSwapBacked(new_page); |
f45840b5 | 340 | __clear_page_locked(new_page); |
2ca4532a DN |
341 | /* |
342 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely | |
343 | * clear SWAP_HAS_CACHE flag. | |
344 | */ | |
cb4b86ba | 345 | swapcache_free(entry, NULL); |
f000944d | 346 | } while (err != -ENOMEM); |
1da177e4 LT |
347 | |
348 | if (new_page) | |
349 | page_cache_release(new_page); | |
350 | return found_page; | |
351 | } | |
46017e95 HD |
352 | |
353 | /** | |
354 | * swapin_readahead - swap in pages in hope we need them soon | |
355 | * @entry: swap entry of this memory | |
7682486b | 356 | * @gfp_mask: memory allocation flags |
46017e95 HD |
357 | * @vma: user vma this address belongs to |
358 | * @addr: target address for mempolicy | |
359 | * | |
360 | * Returns the struct page for entry and addr, after queueing swapin. | |
361 | * | |
362 | * Primitive swap readahead code. We simply read an aligned block of | |
363 | * (1 << page_cluster) entries in the swap area. This method is chosen | |
364 | * because it doesn't cost us any seek time. We also make sure to queue | |
365 | * the 'original' request together with the readahead ones... | |
366 | * | |
367 | * This has been extended to use the NUMA policies from the mm triggering | |
368 | * the readahead. | |
369 | * | |
370 | * Caller must hold down_read on the vma->vm_mm if vma is not NULL. | |
371 | */ | |
02098fea | 372 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
46017e95 HD |
373 | struct vm_area_struct *vma, unsigned long addr) |
374 | { | |
46017e95 | 375 | struct page *page; |
67f96aa2 RR |
376 | unsigned long offset = swp_offset(entry); |
377 | unsigned long start_offset, end_offset; | |
378 | unsigned long mask = (1UL << page_cluster) - 1; | |
46017e95 | 379 | |
67f96aa2 RR |
380 | /* Read a page_cluster sized and aligned cluster around offset. */ |
381 | start_offset = offset & ~mask; | |
382 | end_offset = offset | mask; | |
383 | if (!start_offset) /* First page is swap header. */ | |
384 | start_offset++; | |
385 | ||
386 | for (offset = start_offset; offset <= end_offset ; offset++) { | |
46017e95 HD |
387 | /* Ok, do the async read-ahead now */ |
388 | page = read_swap_cache_async(swp_entry(swp_type(entry), offset), | |
02098fea | 389 | gfp_mask, vma, addr); |
46017e95 | 390 | if (!page) |
67f96aa2 | 391 | continue; |
46017e95 HD |
392 | page_cache_release(page); |
393 | } | |
394 | lru_add_drain(); /* Push any new pages onto the LRU now */ | |
02098fea | 395 | return read_swap_cache_async(entry, gfp_mask, vma, addr); |
46017e95 | 396 | } |