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; | |
1da177e4 LT |
55 | } swap_cache_info; |
56 | ||
57 | void show_swap_cache_info(void) | |
58 | { | |
bb63be0a | 59 | printk("Swap cache: add %lu, delete %lu, find %lu/%lu\n", |
1da177e4 | 60 | swap_cache_info.add_total, swap_cache_info.del_total, |
bb63be0a | 61 | swap_cache_info.find_success, swap_cache_info.find_total); |
1da177e4 LT |
62 | printk("Free swap = %lukB\n", nr_swap_pages << (PAGE_SHIFT - 10)); |
63 | printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); | |
64 | } | |
65 | ||
66 | /* | |
f000944d | 67 | * add_to_swap_cache resembles add_to_page_cache on swapper_space, |
1da177e4 LT |
68 | * but sets SwapCache flag and private instead of mapping and index. |
69 | */ | |
73b1262f | 70 | int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) |
1da177e4 LT |
71 | { |
72 | int error; | |
73 | ||
b55ed816 | 74 | BUG_ON(!PageLocked(page)); |
1da177e4 LT |
75 | BUG_ON(PageSwapCache(page)); |
76 | BUG_ON(PagePrivate(page)); | |
77 | error = radix_tree_preload(gfp_mask); | |
78 | if (!error) { | |
79 | write_lock_irq(&swapper_space.tree_lock); | |
80 | error = radix_tree_insert(&swapper_space.page_tree, | |
81 | entry.val, page); | |
82 | if (!error) { | |
83 | page_cache_get(page); | |
1da177e4 | 84 | SetPageSwapCache(page); |
4c21e2f2 | 85 | set_page_private(page, entry.val); |
1da177e4 | 86 | total_swapcache_pages++; |
347ce434 | 87 | __inc_zone_page_state(page, NR_FILE_PAGES); |
bb63be0a | 88 | INC_CACHE_INFO(add_total); |
1da177e4 LT |
89 | } |
90 | write_unlock_irq(&swapper_space.tree_lock); | |
91 | radix_tree_preload_end(); | |
92 | } | |
93 | return error; | |
94 | } | |
95 | ||
1da177e4 LT |
96 | /* |
97 | * This must be called only on pages that have | |
98 | * been verified to be in the swap cache. | |
99 | */ | |
100 | void __delete_from_swap_cache(struct page *page) | |
101 | { | |
102 | BUG_ON(!PageLocked(page)); | |
103 | BUG_ON(!PageSwapCache(page)); | |
104 | BUG_ON(PageWriteback(page)); | |
3279ffd9 | 105 | BUG_ON(PagePrivate(page)); |
1da177e4 | 106 | |
4c21e2f2 HD |
107 | radix_tree_delete(&swapper_space.page_tree, page_private(page)); |
108 | set_page_private(page, 0); | |
1da177e4 LT |
109 | ClearPageSwapCache(page); |
110 | total_swapcache_pages--; | |
347ce434 | 111 | __dec_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
112 | INC_CACHE_INFO(del_total); |
113 | } | |
114 | ||
115 | /** | |
116 | * add_to_swap - allocate swap space for a page | |
117 | * @page: page we want to move to swap | |
118 | * | |
119 | * Allocate swap space for the page and add the page to the | |
120 | * swap cache. Caller needs to hold the page lock. | |
121 | */ | |
1480a540 | 122 | int add_to_swap(struct page * page, gfp_t gfp_mask) |
1da177e4 LT |
123 | { |
124 | swp_entry_t entry; | |
1da177e4 LT |
125 | int err; |
126 | ||
e74ca2b4 | 127 | BUG_ON(!PageLocked(page)); |
0ed361de | 128 | BUG_ON(!PageUptodate(page)); |
1da177e4 LT |
129 | |
130 | for (;;) { | |
131 | entry = get_swap_page(); | |
132 | if (!entry.val) | |
133 | return 0; | |
134 | ||
bd53b714 NP |
135 | /* |
136 | * Radix-tree node allocations from PF_MEMALLOC contexts could | |
137 | * completely exhaust the page allocator. __GFP_NOMEMALLOC | |
138 | * stops emergency reserves from being allocated. | |
1da177e4 | 139 | * |
bd53b714 NP |
140 | * TODO: this could cause a theoretical memory reclaim |
141 | * deadlock in the swap out path. | |
1da177e4 | 142 | */ |
1da177e4 LT |
143 | /* |
144 | * Add it to the swap cache and mark it dirty | |
145 | */ | |
f000944d | 146 | err = add_to_swap_cache(page, entry, |
1480a540 | 147 | gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN); |
1da177e4 LT |
148 | |
149 | switch (err) { | |
150 | case 0: /* Success */ | |
1da177e4 | 151 | SetPageDirty(page); |
1da177e4 LT |
152 | return 1; |
153 | case -EEXIST: | |
154 | /* Raced with "speculative" read_swap_cache_async */ | |
1da177e4 LT |
155 | swap_free(entry); |
156 | continue; | |
157 | default: | |
158 | /* -ENOMEM radix-tree allocation failure */ | |
159 | swap_free(entry); | |
160 | return 0; | |
161 | } | |
162 | } | |
163 | } | |
164 | ||
165 | /* | |
166 | * This must be called only on pages that have | |
167 | * been verified to be in the swap cache and locked. | |
168 | * It will never put the page into the free list, | |
169 | * the caller has a reference on the page. | |
170 | */ | |
171 | void delete_from_swap_cache(struct page *page) | |
172 | { | |
173 | swp_entry_t entry; | |
174 | ||
4c21e2f2 | 175 | entry.val = page_private(page); |
1da177e4 LT |
176 | |
177 | write_lock_irq(&swapper_space.tree_lock); | |
178 | __delete_from_swap_cache(page); | |
179 | write_unlock_irq(&swapper_space.tree_lock); | |
180 | ||
181 | swap_free(entry); | |
182 | page_cache_release(page); | |
183 | } | |
184 | ||
1da177e4 LT |
185 | /* |
186 | * If we are the only user, then try to free up the swap cache. | |
187 | * | |
188 | * Its ok to check for PageSwapCache without the page lock | |
189 | * here because we are going to recheck again inside | |
190 | * exclusive_swap_page() _with_ the lock. | |
191 | * - Marcelo | |
192 | */ | |
193 | static inline void free_swap_cache(struct page *page) | |
194 | { | |
195 | if (PageSwapCache(page) && !TestSetPageLocked(page)) { | |
196 | remove_exclusive_swap_page(page); | |
197 | unlock_page(page); | |
198 | } | |
199 | } | |
200 | ||
201 | /* | |
202 | * Perform a free_page(), also freeing any swap cache associated with | |
b8072f09 | 203 | * this page if it is the last user of the page. |
1da177e4 LT |
204 | */ |
205 | void free_page_and_swap_cache(struct page *page) | |
206 | { | |
207 | free_swap_cache(page); | |
208 | page_cache_release(page); | |
209 | } | |
210 | ||
211 | /* | |
212 | * Passed an array of pages, drop them all from swapcache and then release | |
213 | * them. They are removed from the LRU and freed if this is their last use. | |
214 | */ | |
215 | void free_pages_and_swap_cache(struct page **pages, int nr) | |
216 | { | |
1da177e4 LT |
217 | struct page **pagep = pages; |
218 | ||
219 | lru_add_drain(); | |
220 | while (nr) { | |
c484d410 | 221 | int todo = min(nr, PAGEVEC_SIZE); |
1da177e4 LT |
222 | int i; |
223 | ||
224 | for (i = 0; i < todo; i++) | |
225 | free_swap_cache(pagep[i]); | |
226 | release_pages(pagep, todo, 0); | |
227 | pagep += todo; | |
228 | nr -= todo; | |
229 | } | |
230 | } | |
231 | ||
232 | /* | |
233 | * Lookup a swap entry in the swap cache. A found page will be returned | |
234 | * unlocked and with its refcount incremented - we rely on the kernel | |
235 | * lock getting page table operations atomic even if we drop the page | |
236 | * lock before returning. | |
237 | */ | |
238 | struct page * lookup_swap_cache(swp_entry_t entry) | |
239 | { | |
240 | struct page *page; | |
241 | ||
242 | page = find_get_page(&swapper_space, entry.val); | |
243 | ||
244 | if (page) | |
245 | INC_CACHE_INFO(find_success); | |
246 | ||
247 | INC_CACHE_INFO(find_total); | |
248 | return page; | |
249 | } | |
250 | ||
251 | /* | |
252 | * Locate a page of swap in physical memory, reserving swap cache space | |
253 | * and reading the disk if it is not already cached. | |
254 | * A failure return means that either the page allocation failed or that | |
255 | * the swap entry is no longer in use. | |
256 | */ | |
02098fea | 257 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
1da177e4 LT |
258 | struct vm_area_struct *vma, unsigned long addr) |
259 | { | |
260 | struct page *found_page, *new_page = NULL; | |
261 | int err; | |
262 | ||
263 | do { | |
264 | /* | |
265 | * First check the swap cache. Since this is normally | |
266 | * called after lookup_swap_cache() failed, re-calling | |
267 | * that would confuse statistics. | |
268 | */ | |
269 | found_page = find_get_page(&swapper_space, entry.val); | |
270 | if (found_page) | |
271 | break; | |
272 | ||
273 | /* | |
274 | * Get a new page to read into from swap. | |
275 | */ | |
276 | if (!new_page) { | |
02098fea | 277 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
1da177e4 LT |
278 | if (!new_page) |
279 | break; /* Out of memory */ | |
280 | } | |
281 | ||
f000944d HD |
282 | /* |
283 | * Swap entry may have been freed since our caller observed it. | |
284 | */ | |
285 | if (!swap_duplicate(entry)) | |
286 | break; | |
287 | ||
1da177e4 LT |
288 | /* |
289 | * Associate the page with swap entry in the swap cache. | |
f000944d HD |
290 | * May fail (-EEXIST) if there is already a page associated |
291 | * with this entry in the swap cache: added by a racing | |
292 | * read_swap_cache_async, or add_to_swap or shmem_writepage | |
293 | * re-using the just freed swap entry for an existing page. | |
1da177e4 LT |
294 | * May fail (-ENOMEM) if radix-tree node allocation failed. |
295 | */ | |
f000944d HD |
296 | SetPageLocked(new_page); |
297 | err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL); | |
1da177e4 LT |
298 | if (!err) { |
299 | /* | |
300 | * Initiate read into locked page and return. | |
301 | */ | |
302 | lru_cache_add_active(new_page); | |
303 | swap_readpage(NULL, new_page); | |
304 | return new_page; | |
305 | } | |
f000944d HD |
306 | ClearPageLocked(new_page); |
307 | swap_free(entry); | |
308 | } while (err != -ENOMEM); | |
1da177e4 LT |
309 | |
310 | if (new_page) | |
311 | page_cache_release(new_page); | |
312 | return found_page; | |
313 | } | |
46017e95 HD |
314 | |
315 | /** | |
316 | * swapin_readahead - swap in pages in hope we need them soon | |
317 | * @entry: swap entry of this memory | |
318 | * @vma: user vma this address belongs to | |
319 | * @addr: target address for mempolicy | |
320 | * | |
321 | * Returns the struct page for entry and addr, after queueing swapin. | |
322 | * | |
323 | * Primitive swap readahead code. We simply read an aligned block of | |
324 | * (1 << page_cluster) entries in the swap area. This method is chosen | |
325 | * because it doesn't cost us any seek time. We also make sure to queue | |
326 | * the 'original' request together with the readahead ones... | |
327 | * | |
328 | * This has been extended to use the NUMA policies from the mm triggering | |
329 | * the readahead. | |
330 | * | |
331 | * Caller must hold down_read on the vma->vm_mm if vma is not NULL. | |
332 | */ | |
02098fea | 333 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
46017e95 HD |
334 | struct vm_area_struct *vma, unsigned long addr) |
335 | { | |
336 | int nr_pages; | |
337 | struct page *page; | |
338 | unsigned long offset; | |
339 | unsigned long end_offset; | |
340 | ||
341 | /* | |
342 | * Get starting offset for readaround, and number of pages to read. | |
343 | * Adjust starting address by readbehind (for NUMA interleave case)? | |
344 | * No, it's very unlikely that swap layout would follow vma layout, | |
345 | * more likely that neighbouring swap pages came from the same node: | |
346 | * so use the same "addr" to choose the same node for each swap read. | |
347 | */ | |
348 | nr_pages = valid_swaphandles(entry, &offset); | |
349 | for (end_offset = offset + nr_pages; offset < end_offset; offset++) { | |
350 | /* Ok, do the async read-ahead now */ | |
351 | page = read_swap_cache_async(swp_entry(swp_type(entry), offset), | |
02098fea | 352 | gfp_mask, vma, addr); |
46017e95 HD |
353 | if (!page) |
354 | break; | |
355 | page_cache_release(page); | |
356 | } | |
357 | lru_add_drain(); /* Push any new pages onto the LRU now */ | |
02098fea | 358 | return read_swap_cache_async(entry, gfp_mask, vma, addr); |
46017e95 | 359 | } |