Commit | Line | Data |
---|---|---|
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, |
1c93923c | 31 | #ifdef CONFIG_MIGRATION |
e965f963 | 32 | .migratepage = migrate_page, |
1c93923c | 33 | #endif |
1da177e4 LT |
34 | }; |
35 | ||
36 | static struct backing_dev_info swap_backing_dev_info = { | |
d993831f | 37 | .name = "swap", |
4f98a2fe | 38 | .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED, |
1da177e4 LT |
39 | }; |
40 | ||
33806f06 SL |
41 | struct address_space swapper_spaces[MAX_SWAPFILES] = { |
42 | [0 ... MAX_SWAPFILES - 1] = { | |
43 | .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN), | |
4bb5f5d9 | 44 | .i_mmap_writable = ATOMIC_INIT(0), |
33806f06 SL |
45 | .a_ops = &swap_aops, |
46 | .backing_dev_info = &swap_backing_dev_info, | |
47 | } | |
1da177e4 | 48 | }; |
1da177e4 LT |
49 | |
50 | #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) | |
51 | ||
52 | static struct { | |
53 | unsigned long add_total; | |
54 | unsigned long del_total; | |
55 | unsigned long find_success; | |
56 | unsigned long find_total; | |
1da177e4 LT |
57 | } swap_cache_info; |
58 | ||
33806f06 SL |
59 | unsigned long total_swapcache_pages(void) |
60 | { | |
61 | int i; | |
62 | unsigned long ret = 0; | |
63 | ||
64 | for (i = 0; i < MAX_SWAPFILES; i++) | |
65 | ret += swapper_spaces[i].nrpages; | |
66 | return ret; | |
67 | } | |
68 | ||
579f8290 SL |
69 | static atomic_t swapin_readahead_hits = ATOMIC_INIT(4); |
70 | ||
1da177e4 LT |
71 | void show_swap_cache_info(void) |
72 | { | |
33806f06 | 73 | printk("%lu pages in swap cache\n", total_swapcache_pages()); |
2c97b7fc | 74 | printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n", |
1da177e4 | 75 | swap_cache_info.add_total, swap_cache_info.del_total, |
bb63be0a | 76 | swap_cache_info.find_success, swap_cache_info.find_total); |
ec8acf20 SL |
77 | printk("Free swap = %ldkB\n", |
78 | get_nr_swap_pages() << (PAGE_SHIFT - 10)); | |
1da177e4 LT |
79 | printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); |
80 | } | |
81 | ||
82 | /* | |
31a56396 | 83 | * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space, |
1da177e4 LT |
84 | * but sets SwapCache flag and private instead of mapping and index. |
85 | */ | |
2f772e6c | 86 | int __add_to_swap_cache(struct page *page, swp_entry_t entry) |
1da177e4 LT |
87 | { |
88 | int error; | |
33806f06 | 89 | struct address_space *address_space; |
1da177e4 | 90 | |
309381fe SL |
91 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
92 | VM_BUG_ON_PAGE(PageSwapCache(page), page); | |
93 | VM_BUG_ON_PAGE(!PageSwapBacked(page), page); | |
51726b12 | 94 | |
31a56396 DN |
95 | page_cache_get(page); |
96 | SetPageSwapCache(page); | |
97 | set_page_private(page, entry.val); | |
98 | ||
33806f06 SL |
99 | address_space = swap_address_space(entry); |
100 | spin_lock_irq(&address_space->tree_lock); | |
101 | error = radix_tree_insert(&address_space->page_tree, | |
102 | entry.val, page); | |
31a56396 | 103 | if (likely(!error)) { |
33806f06 | 104 | address_space->nrpages++; |
31a56396 DN |
105 | __inc_zone_page_state(page, NR_FILE_PAGES); |
106 | INC_CACHE_INFO(add_total); | |
107 | } | |
33806f06 | 108 | spin_unlock_irq(&address_space->tree_lock); |
31a56396 DN |
109 | |
110 | if (unlikely(error)) { | |
2ca4532a DN |
111 | /* |
112 | * Only the context which have set SWAP_HAS_CACHE flag | |
113 | * would call add_to_swap_cache(). | |
114 | * So add_to_swap_cache() doesn't returns -EEXIST. | |
115 | */ | |
116 | VM_BUG_ON(error == -EEXIST); | |
31a56396 DN |
117 | set_page_private(page, 0UL); |
118 | ClearPageSwapCache(page); | |
119 | page_cache_release(page); | |
120 | } | |
121 | ||
122 | return error; | |
123 | } | |
124 | ||
125 | ||
126 | int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) | |
127 | { | |
128 | int error; | |
129 | ||
5e4c0d97 | 130 | error = radix_tree_maybe_preload(gfp_mask); |
35c754d7 | 131 | if (!error) { |
31a56396 | 132 | error = __add_to_swap_cache(page, entry); |
1da177e4 | 133 | radix_tree_preload_end(); |
fa1de900 | 134 | } |
1da177e4 LT |
135 | return error; |
136 | } | |
137 | ||
1da177e4 LT |
138 | /* |
139 | * This must be called only on pages that have | |
140 | * been verified to be in the swap cache. | |
141 | */ | |
142 | void __delete_from_swap_cache(struct page *page) | |
143 | { | |
33806f06 SL |
144 | swp_entry_t entry; |
145 | struct address_space *address_space; | |
146 | ||
309381fe SL |
147 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
148 | VM_BUG_ON_PAGE(!PageSwapCache(page), page); | |
149 | VM_BUG_ON_PAGE(PageWriteback(page), page); | |
1da177e4 | 150 | |
33806f06 SL |
151 | entry.val = page_private(page); |
152 | address_space = swap_address_space(entry); | |
153 | radix_tree_delete(&address_space->page_tree, page_private(page)); | |
4c21e2f2 | 154 | set_page_private(page, 0); |
1da177e4 | 155 | ClearPageSwapCache(page); |
33806f06 | 156 | address_space->nrpages--; |
347ce434 | 157 | __dec_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
158 | INC_CACHE_INFO(del_total); |
159 | } | |
160 | ||
161 | /** | |
162 | * add_to_swap - allocate swap space for a page | |
163 | * @page: page we want to move to swap | |
164 | * | |
165 | * Allocate swap space for the page and add the page to the | |
166 | * swap cache. Caller needs to hold the page lock. | |
167 | */ | |
5bc7b8ac | 168 | int add_to_swap(struct page *page, struct list_head *list) |
1da177e4 LT |
169 | { |
170 | swp_entry_t entry; | |
1da177e4 LT |
171 | int err; |
172 | ||
309381fe SL |
173 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
174 | VM_BUG_ON_PAGE(!PageUptodate(page), page); | |
1da177e4 | 175 | |
2ca4532a DN |
176 | entry = get_swap_page(); |
177 | if (!entry.val) | |
178 | return 0; | |
179 | ||
3f04f62f | 180 | if (unlikely(PageTransHuge(page))) |
5bc7b8ac | 181 | if (unlikely(split_huge_page_to_list(page, list))) { |
0a31bc97 | 182 | swapcache_free(entry); |
3f04f62f AA |
183 | return 0; |
184 | } | |
185 | ||
2ca4532a DN |
186 | /* |
187 | * Radix-tree node allocations from PF_MEMALLOC contexts could | |
188 | * completely exhaust the page allocator. __GFP_NOMEMALLOC | |
189 | * stops emergency reserves from being allocated. | |
190 | * | |
191 | * TODO: this could cause a theoretical memory reclaim | |
192 | * deadlock in the swap out path. | |
193 | */ | |
194 | /* | |
195 | * Add it to the swap cache and mark it dirty | |
196 | */ | |
197 | err = add_to_swap_cache(page, entry, | |
198 | __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); | |
199 | ||
200 | if (!err) { /* Success */ | |
201 | SetPageDirty(page); | |
202 | return 1; | |
203 | } else { /* -ENOMEM radix-tree allocation failure */ | |
bd53b714 | 204 | /* |
2ca4532a DN |
205 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
206 | * clear SWAP_HAS_CACHE flag. | |
1da177e4 | 207 | */ |
0a31bc97 | 208 | swapcache_free(entry); |
2ca4532a | 209 | return 0; |
1da177e4 LT |
210 | } |
211 | } | |
212 | ||
213 | /* | |
214 | * This must be called only on pages that have | |
215 | * been verified to be in the swap cache and locked. | |
216 | * It will never put the page into the free list, | |
217 | * the caller has a reference on the page. | |
218 | */ | |
219 | void delete_from_swap_cache(struct page *page) | |
220 | { | |
221 | swp_entry_t entry; | |
33806f06 | 222 | struct address_space *address_space; |
1da177e4 | 223 | |
4c21e2f2 | 224 | entry.val = page_private(page); |
1da177e4 | 225 | |
33806f06 SL |
226 | address_space = swap_address_space(entry); |
227 | spin_lock_irq(&address_space->tree_lock); | |
1da177e4 | 228 | __delete_from_swap_cache(page); |
33806f06 | 229 | spin_unlock_irq(&address_space->tree_lock); |
1da177e4 | 230 | |
0a31bc97 | 231 | swapcache_free(entry); |
1da177e4 LT |
232 | page_cache_release(page); |
233 | } | |
234 | ||
1da177e4 LT |
235 | /* |
236 | * If we are the only user, then try to free up the swap cache. | |
237 | * | |
238 | * Its ok to check for PageSwapCache without the page lock | |
a2c43eed HD |
239 | * here because we are going to recheck again inside |
240 | * try_to_free_swap() _with_ the lock. | |
1da177e4 LT |
241 | * - Marcelo |
242 | */ | |
243 | static inline void free_swap_cache(struct page *page) | |
244 | { | |
a2c43eed HD |
245 | if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { |
246 | try_to_free_swap(page); | |
1da177e4 LT |
247 | unlock_page(page); |
248 | } | |
249 | } | |
250 | ||
251 | /* | |
252 | * Perform a free_page(), also freeing any swap cache associated with | |
b8072f09 | 253 | * this page if it is the last user of the page. |
1da177e4 LT |
254 | */ |
255 | void free_page_and_swap_cache(struct page *page) | |
256 | { | |
257 | free_swap_cache(page); | |
258 | page_cache_release(page); | |
259 | } | |
260 | ||
261 | /* | |
262 | * Passed an array of pages, drop them all from swapcache and then release | |
263 | * them. They are removed from the LRU and freed if this is their last use. | |
264 | */ | |
265 | void free_pages_and_swap_cache(struct page **pages, int nr) | |
266 | { | |
1da177e4 | 267 | struct page **pagep = pages; |
aabfb572 | 268 | int i; |
1da177e4 LT |
269 | |
270 | lru_add_drain(); | |
aabfb572 MH |
271 | for (i = 0; i < nr; i++) |
272 | free_swap_cache(pagep[i]); | |
273 | release_pages(pagep, nr, false); | |
1da177e4 LT |
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 | 287 | |
579f8290 | 288 | if (page) { |
1da177e4 | 289 | INC_CACHE_INFO(find_success); |
579f8290 SL |
290 | if (TestClearPageReadahead(page)) |
291 | atomic_inc(&swapin_readahead_hits); | |
292 | } | |
1da177e4 LT |
293 | |
294 | INC_CACHE_INFO(find_total); | |
295 | return page; | |
296 | } | |
297 | ||
298 | /* | |
299 | * Locate a page of swap in physical memory, reserving swap cache space | |
300 | * and reading the disk if it is not already cached. | |
301 | * A failure return means that either the page allocation failed or that | |
302 | * the swap entry is no longer in use. | |
303 | */ | |
02098fea | 304 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
1da177e4 LT |
305 | struct vm_area_struct *vma, unsigned long addr) |
306 | { | |
307 | struct page *found_page, *new_page = NULL; | |
308 | int err; | |
309 | ||
310 | do { | |
311 | /* | |
312 | * First check the swap cache. Since this is normally | |
313 | * called after lookup_swap_cache() failed, re-calling | |
314 | * that would confuse statistics. | |
315 | */ | |
33806f06 SL |
316 | found_page = find_get_page(swap_address_space(entry), |
317 | entry.val); | |
1da177e4 LT |
318 | if (found_page) |
319 | break; | |
320 | ||
321 | /* | |
322 | * Get a new page to read into from swap. | |
323 | */ | |
324 | if (!new_page) { | |
02098fea | 325 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
1da177e4 LT |
326 | if (!new_page) |
327 | break; /* Out of memory */ | |
328 | } | |
329 | ||
31a56396 DN |
330 | /* |
331 | * call radix_tree_preload() while we can wait. | |
332 | */ | |
5e4c0d97 | 333 | err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL); |
31a56396 DN |
334 | if (err) |
335 | break; | |
336 | ||
f000944d HD |
337 | /* |
338 | * Swap entry may have been freed since our caller observed it. | |
339 | */ | |
355cfa73 | 340 | err = swapcache_prepare(entry); |
cbab0e4e | 341 | if (err == -EEXIST) { |
31a56396 | 342 | radix_tree_preload_end(); |
cbab0e4e RA |
343 | /* |
344 | * We might race against get_swap_page() and stumble | |
345 | * across a SWAP_HAS_CACHE swap_map entry whose page | |
346 | * has not been brought into the swapcache yet, while | |
347 | * the other end is scheduled away waiting on discard | |
348 | * I/O completion at scan_swap_map(). | |
349 | * | |
350 | * In order to avoid turning this transitory state | |
351 | * into a permanent loop around this -EEXIST case | |
352 | * if !CONFIG_PREEMPT and the I/O completion happens | |
353 | * to be waiting on the CPU waitqueue where we are now | |
354 | * busy looping, we just conditionally invoke the | |
355 | * scheduler here, if there are some more important | |
356 | * tasks to run. | |
357 | */ | |
358 | cond_resched(); | |
355cfa73 | 359 | continue; |
31a56396 DN |
360 | } |
361 | if (err) { /* swp entry is obsolete ? */ | |
362 | radix_tree_preload_end(); | |
f000944d | 363 | break; |
31a56396 | 364 | } |
f000944d | 365 | |
2ca4532a | 366 | /* May fail (-ENOMEM) if radix-tree node allocation failed. */ |
f45840b5 | 367 | __set_page_locked(new_page); |
b2e18538 | 368 | SetPageSwapBacked(new_page); |
31a56396 | 369 | err = __add_to_swap_cache(new_page, entry); |
529ae9aa | 370 | if (likely(!err)) { |
31a56396 | 371 | radix_tree_preload_end(); |
1da177e4 LT |
372 | /* |
373 | * Initiate read into locked page and return. | |
374 | */ | |
c5fdae46 | 375 | lru_cache_add_anon(new_page); |
aca8bf32 | 376 | swap_readpage(new_page); |
1da177e4 LT |
377 | return new_page; |
378 | } | |
31a56396 | 379 | radix_tree_preload_end(); |
b2e18538 | 380 | ClearPageSwapBacked(new_page); |
f45840b5 | 381 | __clear_page_locked(new_page); |
2ca4532a DN |
382 | /* |
383 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely | |
384 | * clear SWAP_HAS_CACHE flag. | |
385 | */ | |
0a31bc97 | 386 | swapcache_free(entry); |
f000944d | 387 | } while (err != -ENOMEM); |
1da177e4 LT |
388 | |
389 | if (new_page) | |
390 | page_cache_release(new_page); | |
391 | return found_page; | |
392 | } | |
46017e95 | 393 | |
579f8290 SL |
394 | static unsigned long swapin_nr_pages(unsigned long offset) |
395 | { | |
396 | static unsigned long prev_offset; | |
397 | unsigned int pages, max_pages, last_ra; | |
398 | static atomic_t last_readahead_pages; | |
399 | ||
400 | max_pages = 1 << ACCESS_ONCE(page_cluster); | |
401 | if (max_pages <= 1) | |
402 | return 1; | |
403 | ||
404 | /* | |
405 | * This heuristic has been found to work well on both sequential and | |
406 | * random loads, swapping to hard disk or to SSD: please don't ask | |
407 | * what the "+ 2" means, it just happens to work well, that's all. | |
408 | */ | |
409 | pages = atomic_xchg(&swapin_readahead_hits, 0) + 2; | |
410 | if (pages == 2) { | |
411 | /* | |
412 | * We can have no readahead hits to judge by: but must not get | |
413 | * stuck here forever, so check for an adjacent offset instead | |
414 | * (and don't even bother to check whether swap type is same). | |
415 | */ | |
416 | if (offset != prev_offset + 1 && offset != prev_offset - 1) | |
417 | pages = 1; | |
418 | prev_offset = offset; | |
419 | } else { | |
420 | unsigned int roundup = 4; | |
421 | while (roundup < pages) | |
422 | roundup <<= 1; | |
423 | pages = roundup; | |
424 | } | |
425 | ||
426 | if (pages > max_pages) | |
427 | pages = max_pages; | |
428 | ||
429 | /* Don't shrink readahead too fast */ | |
430 | last_ra = atomic_read(&last_readahead_pages) / 2; | |
431 | if (pages < last_ra) | |
432 | pages = last_ra; | |
433 | atomic_set(&last_readahead_pages, pages); | |
434 | ||
435 | return pages; | |
436 | } | |
437 | ||
46017e95 HD |
438 | /** |
439 | * swapin_readahead - swap in pages in hope we need them soon | |
440 | * @entry: swap entry of this memory | |
7682486b | 441 | * @gfp_mask: memory allocation flags |
46017e95 HD |
442 | * @vma: user vma this address belongs to |
443 | * @addr: target address for mempolicy | |
444 | * | |
445 | * Returns the struct page for entry and addr, after queueing swapin. | |
446 | * | |
447 | * Primitive swap readahead code. We simply read an aligned block of | |
448 | * (1 << page_cluster) entries in the swap area. This method is chosen | |
449 | * because it doesn't cost us any seek time. We also make sure to queue | |
450 | * the 'original' request together with the readahead ones... | |
451 | * | |
452 | * This has been extended to use the NUMA policies from the mm triggering | |
453 | * the readahead. | |
454 | * | |
455 | * Caller must hold down_read on the vma->vm_mm if vma is not NULL. | |
456 | */ | |
02098fea | 457 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
46017e95 HD |
458 | struct vm_area_struct *vma, unsigned long addr) |
459 | { | |
46017e95 | 460 | struct page *page; |
579f8290 SL |
461 | unsigned long entry_offset = swp_offset(entry); |
462 | unsigned long offset = entry_offset; | |
67f96aa2 | 463 | unsigned long start_offset, end_offset; |
579f8290 | 464 | unsigned long mask; |
3fb5c298 | 465 | struct blk_plug plug; |
46017e95 | 466 | |
579f8290 SL |
467 | mask = swapin_nr_pages(offset) - 1; |
468 | if (!mask) | |
469 | goto skip; | |
470 | ||
67f96aa2 RR |
471 | /* Read a page_cluster sized and aligned cluster around offset. */ |
472 | start_offset = offset & ~mask; | |
473 | end_offset = offset | mask; | |
474 | if (!start_offset) /* First page is swap header. */ | |
475 | start_offset++; | |
476 | ||
3fb5c298 | 477 | blk_start_plug(&plug); |
67f96aa2 | 478 | for (offset = start_offset; offset <= end_offset ; offset++) { |
46017e95 HD |
479 | /* Ok, do the async read-ahead now */ |
480 | page = read_swap_cache_async(swp_entry(swp_type(entry), offset), | |
02098fea | 481 | gfp_mask, vma, addr); |
46017e95 | 482 | if (!page) |
67f96aa2 | 483 | continue; |
579f8290 SL |
484 | if (offset != entry_offset) |
485 | SetPageReadahead(page); | |
46017e95 HD |
486 | page_cache_release(page); |
487 | } | |
3fb5c298 CE |
488 | blk_finish_plug(&plug); |
489 | ||
46017e95 | 490 | lru_add_drain(); /* Push any new pages onto the LRU now */ |
579f8290 | 491 | skip: |
02098fea | 492 | return read_swap_cache_async(entry, gfp_mask, vma, addr); |
46017e95 | 493 | } |