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, |
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 | ||
579f8290 SL |
66 | static atomic_t swapin_readahead_hits = ATOMIC_INIT(4); |
67 | ||
1da177e4 LT |
68 | void show_swap_cache_info(void) |
69 | { | |
33806f06 | 70 | printk("%lu pages in swap cache\n", total_swapcache_pages()); |
2c97b7fc | 71 | printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n", |
1da177e4 | 72 | swap_cache_info.add_total, swap_cache_info.del_total, |
bb63be0a | 73 | swap_cache_info.find_success, swap_cache_info.find_total); |
ec8acf20 SL |
74 | printk("Free swap = %ldkB\n", |
75 | get_nr_swap_pages() << (PAGE_SHIFT - 10)); | |
1da177e4 LT |
76 | printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); |
77 | } | |
78 | ||
79 | /* | |
31a56396 | 80 | * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space, |
1da177e4 LT |
81 | * but sets SwapCache flag and private instead of mapping and index. |
82 | */ | |
2f772e6c | 83 | int __add_to_swap_cache(struct page *page, swp_entry_t entry) |
1da177e4 LT |
84 | { |
85 | int error; | |
33806f06 | 86 | struct address_space *address_space; |
1da177e4 | 87 | |
309381fe SL |
88 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
89 | VM_BUG_ON_PAGE(PageSwapCache(page), page); | |
90 | VM_BUG_ON_PAGE(!PageSwapBacked(page), page); | |
51726b12 | 91 | |
31a56396 DN |
92 | page_cache_get(page); |
93 | SetPageSwapCache(page); | |
94 | set_page_private(page, entry.val); | |
95 | ||
33806f06 SL |
96 | address_space = swap_address_space(entry); |
97 | spin_lock_irq(&address_space->tree_lock); | |
98 | error = radix_tree_insert(&address_space->page_tree, | |
99 | entry.val, page); | |
31a56396 | 100 | if (likely(!error)) { |
33806f06 | 101 | address_space->nrpages++; |
31a56396 DN |
102 | __inc_zone_page_state(page, NR_FILE_PAGES); |
103 | INC_CACHE_INFO(add_total); | |
104 | } | |
33806f06 | 105 | spin_unlock_irq(&address_space->tree_lock); |
31a56396 DN |
106 | |
107 | if (unlikely(error)) { | |
2ca4532a DN |
108 | /* |
109 | * Only the context which have set SWAP_HAS_CACHE flag | |
110 | * would call add_to_swap_cache(). | |
111 | * So add_to_swap_cache() doesn't returns -EEXIST. | |
112 | */ | |
113 | VM_BUG_ON(error == -EEXIST); | |
31a56396 DN |
114 | set_page_private(page, 0UL); |
115 | ClearPageSwapCache(page); | |
116 | page_cache_release(page); | |
117 | } | |
118 | ||
119 | return error; | |
120 | } | |
121 | ||
122 | ||
123 | int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) | |
124 | { | |
125 | int error; | |
126 | ||
5e4c0d97 | 127 | error = radix_tree_maybe_preload(gfp_mask); |
35c754d7 | 128 | if (!error) { |
31a56396 | 129 | error = __add_to_swap_cache(page, entry); |
1da177e4 | 130 | radix_tree_preload_end(); |
fa1de900 | 131 | } |
1da177e4 LT |
132 | return error; |
133 | } | |
134 | ||
1da177e4 LT |
135 | /* |
136 | * This must be called only on pages that have | |
137 | * been verified to be in the swap cache. | |
138 | */ | |
139 | void __delete_from_swap_cache(struct page *page) | |
140 | { | |
33806f06 SL |
141 | swp_entry_t entry; |
142 | struct address_space *address_space; | |
143 | ||
309381fe SL |
144 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
145 | VM_BUG_ON_PAGE(!PageSwapCache(page), page); | |
146 | VM_BUG_ON_PAGE(PageWriteback(page), page); | |
1da177e4 | 147 | |
33806f06 SL |
148 | entry.val = page_private(page); |
149 | address_space = swap_address_space(entry); | |
150 | radix_tree_delete(&address_space->page_tree, page_private(page)); | |
4c21e2f2 | 151 | set_page_private(page, 0); |
1da177e4 | 152 | ClearPageSwapCache(page); |
33806f06 | 153 | address_space->nrpages--; |
347ce434 | 154 | __dec_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
155 | INC_CACHE_INFO(del_total); |
156 | } | |
157 | ||
158 | /** | |
159 | * add_to_swap - allocate swap space for a page | |
160 | * @page: page we want to move to swap | |
161 | * | |
162 | * Allocate swap space for the page and add the page to the | |
163 | * swap cache. Caller needs to hold the page lock. | |
164 | */ | |
5bc7b8ac | 165 | int add_to_swap(struct page *page, struct list_head *list) |
1da177e4 LT |
166 | { |
167 | swp_entry_t entry; | |
1da177e4 LT |
168 | int err; |
169 | ||
309381fe SL |
170 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
171 | VM_BUG_ON_PAGE(!PageUptodate(page), page); | |
1da177e4 | 172 | |
2ca4532a DN |
173 | entry = get_swap_page(); |
174 | if (!entry.val) | |
175 | return 0; | |
176 | ||
3f04f62f | 177 | if (unlikely(PageTransHuge(page))) |
5bc7b8ac | 178 | if (unlikely(split_huge_page_to_list(page, list))) { |
3f04f62f AA |
179 | swapcache_free(entry, NULL); |
180 | return 0; | |
181 | } | |
182 | ||
2ca4532a DN |
183 | /* |
184 | * Radix-tree node allocations from PF_MEMALLOC contexts could | |
185 | * completely exhaust the page allocator. __GFP_NOMEMALLOC | |
186 | * stops emergency reserves from being allocated. | |
187 | * | |
188 | * TODO: this could cause a theoretical memory reclaim | |
189 | * deadlock in the swap out path. | |
190 | */ | |
191 | /* | |
192 | * Add it to the swap cache and mark it dirty | |
193 | */ | |
194 | err = add_to_swap_cache(page, entry, | |
195 | __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); | |
196 | ||
197 | if (!err) { /* Success */ | |
198 | SetPageDirty(page); | |
199 | return 1; | |
200 | } else { /* -ENOMEM radix-tree allocation failure */ | |
bd53b714 | 201 | /* |
2ca4532a DN |
202 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
203 | * clear SWAP_HAS_CACHE flag. | |
1da177e4 | 204 | */ |
2ca4532a DN |
205 | swapcache_free(entry, NULL); |
206 | return 0; | |
1da177e4 LT |
207 | } |
208 | } | |
209 | ||
210 | /* | |
211 | * This must be called only on pages that have | |
212 | * been verified to be in the swap cache and locked. | |
213 | * It will never put the page into the free list, | |
214 | * the caller has a reference on the page. | |
215 | */ | |
216 | void delete_from_swap_cache(struct page *page) | |
217 | { | |
218 | swp_entry_t entry; | |
33806f06 | 219 | struct address_space *address_space; |
1da177e4 | 220 | |
4c21e2f2 | 221 | entry.val = page_private(page); |
1da177e4 | 222 | |
33806f06 SL |
223 | address_space = swap_address_space(entry); |
224 | spin_lock_irq(&address_space->tree_lock); | |
1da177e4 | 225 | __delete_from_swap_cache(page); |
33806f06 | 226 | spin_unlock_irq(&address_space->tree_lock); |
1da177e4 | 227 | |
cb4b86ba | 228 | swapcache_free(entry, page); |
1da177e4 LT |
229 | page_cache_release(page); |
230 | } | |
231 | ||
1da177e4 LT |
232 | /* |
233 | * If we are the only user, then try to free up the swap cache. | |
234 | * | |
235 | * Its ok to check for PageSwapCache without the page lock | |
a2c43eed HD |
236 | * here because we are going to recheck again inside |
237 | * try_to_free_swap() _with_ the lock. | |
1da177e4 LT |
238 | * - Marcelo |
239 | */ | |
240 | static inline void free_swap_cache(struct page *page) | |
241 | { | |
a2c43eed HD |
242 | if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { |
243 | try_to_free_swap(page); | |
1da177e4 LT |
244 | unlock_page(page); |
245 | } | |
246 | } | |
247 | ||
248 | /* | |
249 | * Perform a free_page(), also freeing any swap cache associated with | |
b8072f09 | 250 | * this page if it is the last user of the page. |
1da177e4 LT |
251 | */ |
252 | void free_page_and_swap_cache(struct page *page) | |
253 | { | |
254 | free_swap_cache(page); | |
255 | page_cache_release(page); | |
256 | } | |
257 | ||
258 | /* | |
259 | * Passed an array of pages, drop them all from swapcache and then release | |
260 | * them. They are removed from the LRU and freed if this is their last use. | |
261 | */ | |
262 | void free_pages_and_swap_cache(struct page **pages, int nr) | |
263 | { | |
1da177e4 LT |
264 | struct page **pagep = pages; |
265 | ||
266 | lru_add_drain(); | |
267 | while (nr) { | |
c484d410 | 268 | int todo = min(nr, PAGEVEC_SIZE); |
1da177e4 LT |
269 | int i; |
270 | ||
271 | for (i = 0; i < todo; i++) | |
272 | free_swap_cache(pagep[i]); | |
b745bc85 | 273 | release_pages(pagep, todo, false); |
1da177e4 LT |
274 | pagep += todo; |
275 | nr -= todo; | |
276 | } | |
277 | } | |
278 | ||
279 | /* | |
280 | * Lookup a swap entry in the swap cache. A found page will be returned | |
281 | * unlocked and with its refcount incremented - we rely on the kernel | |
282 | * lock getting page table operations atomic even if we drop the page | |
283 | * lock before returning. | |
284 | */ | |
285 | struct page * lookup_swap_cache(swp_entry_t entry) | |
286 | { | |
287 | struct page *page; | |
288 | ||
33806f06 | 289 | page = find_get_page(swap_address_space(entry), entry.val); |
1da177e4 | 290 | |
579f8290 | 291 | if (page) { |
1da177e4 | 292 | INC_CACHE_INFO(find_success); |
579f8290 SL |
293 | if (TestClearPageReadahead(page)) |
294 | atomic_inc(&swapin_readahead_hits); | |
295 | } | |
1da177e4 LT |
296 | |
297 | INC_CACHE_INFO(find_total); | |
298 | return page; | |
299 | } | |
300 | ||
301 | /* | |
302 | * Locate a page of swap in physical memory, reserving swap cache space | |
303 | * and reading the disk if it is not already cached. | |
304 | * A failure return means that either the page allocation failed or that | |
305 | * the swap entry is no longer in use. | |
306 | */ | |
02098fea | 307 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
1da177e4 LT |
308 | struct vm_area_struct *vma, unsigned long addr) |
309 | { | |
310 | struct page *found_page, *new_page = NULL; | |
311 | int err; | |
312 | ||
313 | do { | |
314 | /* | |
315 | * First check the swap cache. Since this is normally | |
316 | * called after lookup_swap_cache() failed, re-calling | |
317 | * that would confuse statistics. | |
318 | */ | |
33806f06 SL |
319 | found_page = find_get_page(swap_address_space(entry), |
320 | entry.val); | |
1da177e4 LT |
321 | if (found_page) |
322 | break; | |
323 | ||
324 | /* | |
325 | * Get a new page to read into from swap. | |
326 | */ | |
327 | if (!new_page) { | |
02098fea | 328 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
1da177e4 LT |
329 | if (!new_page) |
330 | break; /* Out of memory */ | |
331 | } | |
332 | ||
31a56396 DN |
333 | /* |
334 | * call radix_tree_preload() while we can wait. | |
335 | */ | |
5e4c0d97 | 336 | err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL); |
31a56396 DN |
337 | if (err) |
338 | break; | |
339 | ||
f000944d HD |
340 | /* |
341 | * Swap entry may have been freed since our caller observed it. | |
342 | */ | |
355cfa73 | 343 | err = swapcache_prepare(entry); |
cbab0e4e | 344 | if (err == -EEXIST) { |
31a56396 | 345 | radix_tree_preload_end(); |
cbab0e4e RA |
346 | /* |
347 | * We might race against get_swap_page() and stumble | |
348 | * across a SWAP_HAS_CACHE swap_map entry whose page | |
349 | * has not been brought into the swapcache yet, while | |
350 | * the other end is scheduled away waiting on discard | |
351 | * I/O completion at scan_swap_map(). | |
352 | * | |
353 | * In order to avoid turning this transitory state | |
354 | * into a permanent loop around this -EEXIST case | |
355 | * if !CONFIG_PREEMPT and the I/O completion happens | |
356 | * to be waiting on the CPU waitqueue where we are now | |
357 | * busy looping, we just conditionally invoke the | |
358 | * scheduler here, if there are some more important | |
359 | * tasks to run. | |
360 | */ | |
361 | cond_resched(); | |
355cfa73 | 362 | continue; |
31a56396 DN |
363 | } |
364 | if (err) { /* swp entry is obsolete ? */ | |
365 | radix_tree_preload_end(); | |
f000944d | 366 | break; |
31a56396 | 367 | } |
f000944d | 368 | |
2ca4532a | 369 | /* May fail (-ENOMEM) if radix-tree node allocation failed. */ |
f45840b5 | 370 | __set_page_locked(new_page); |
b2e18538 | 371 | SetPageSwapBacked(new_page); |
31a56396 | 372 | err = __add_to_swap_cache(new_page, entry); |
529ae9aa | 373 | if (likely(!err)) { |
31a56396 | 374 | radix_tree_preload_end(); |
1da177e4 LT |
375 | /* |
376 | * Initiate read into locked page and return. | |
377 | */ | |
c5fdae46 | 378 | lru_cache_add_anon(new_page); |
aca8bf32 | 379 | swap_readpage(new_page); |
1da177e4 LT |
380 | return new_page; |
381 | } | |
31a56396 | 382 | radix_tree_preload_end(); |
b2e18538 | 383 | ClearPageSwapBacked(new_page); |
f45840b5 | 384 | __clear_page_locked(new_page); |
2ca4532a DN |
385 | /* |
386 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely | |
387 | * clear SWAP_HAS_CACHE flag. | |
388 | */ | |
cb4b86ba | 389 | swapcache_free(entry, NULL); |
f000944d | 390 | } while (err != -ENOMEM); |
1da177e4 LT |
391 | |
392 | if (new_page) | |
393 | page_cache_release(new_page); | |
394 | return found_page; | |
395 | } | |
46017e95 | 396 | |
579f8290 SL |
397 | static unsigned long swapin_nr_pages(unsigned long offset) |
398 | { | |
399 | static unsigned long prev_offset; | |
400 | unsigned int pages, max_pages, last_ra; | |
401 | static atomic_t last_readahead_pages; | |
402 | ||
403 | max_pages = 1 << ACCESS_ONCE(page_cluster); | |
404 | if (max_pages <= 1) | |
405 | return 1; | |
406 | ||
407 | /* | |
408 | * This heuristic has been found to work well on both sequential and | |
409 | * random loads, swapping to hard disk or to SSD: please don't ask | |
410 | * what the "+ 2" means, it just happens to work well, that's all. | |
411 | */ | |
412 | pages = atomic_xchg(&swapin_readahead_hits, 0) + 2; | |
413 | if (pages == 2) { | |
414 | /* | |
415 | * We can have no readahead hits to judge by: but must not get | |
416 | * stuck here forever, so check for an adjacent offset instead | |
417 | * (and don't even bother to check whether swap type is same). | |
418 | */ | |
419 | if (offset != prev_offset + 1 && offset != prev_offset - 1) | |
420 | pages = 1; | |
421 | prev_offset = offset; | |
422 | } else { | |
423 | unsigned int roundup = 4; | |
424 | while (roundup < pages) | |
425 | roundup <<= 1; | |
426 | pages = roundup; | |
427 | } | |
428 | ||
429 | if (pages > max_pages) | |
430 | pages = max_pages; | |
431 | ||
432 | /* Don't shrink readahead too fast */ | |
433 | last_ra = atomic_read(&last_readahead_pages) / 2; | |
434 | if (pages < last_ra) | |
435 | pages = last_ra; | |
436 | atomic_set(&last_readahead_pages, pages); | |
437 | ||
438 | return pages; | |
439 | } | |
440 | ||
46017e95 HD |
441 | /** |
442 | * swapin_readahead - swap in pages in hope we need them soon | |
443 | * @entry: swap entry of this memory | |
7682486b | 444 | * @gfp_mask: memory allocation flags |
46017e95 HD |
445 | * @vma: user vma this address belongs to |
446 | * @addr: target address for mempolicy | |
447 | * | |
448 | * Returns the struct page for entry and addr, after queueing swapin. | |
449 | * | |
450 | * Primitive swap readahead code. We simply read an aligned block of | |
451 | * (1 << page_cluster) entries in the swap area. This method is chosen | |
452 | * because it doesn't cost us any seek time. We also make sure to queue | |
453 | * the 'original' request together with the readahead ones... | |
454 | * | |
455 | * This has been extended to use the NUMA policies from the mm triggering | |
456 | * the readahead. | |
457 | * | |
458 | * Caller must hold down_read on the vma->vm_mm if vma is not NULL. | |
459 | */ | |
02098fea | 460 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
46017e95 HD |
461 | struct vm_area_struct *vma, unsigned long addr) |
462 | { | |
46017e95 | 463 | struct page *page; |
579f8290 SL |
464 | unsigned long entry_offset = swp_offset(entry); |
465 | unsigned long offset = entry_offset; | |
67f96aa2 | 466 | unsigned long start_offset, end_offset; |
579f8290 | 467 | unsigned long mask; |
3fb5c298 | 468 | struct blk_plug plug; |
46017e95 | 469 | |
579f8290 SL |
470 | mask = swapin_nr_pages(offset) - 1; |
471 | if (!mask) | |
472 | goto skip; | |
473 | ||
67f96aa2 RR |
474 | /* Read a page_cluster sized and aligned cluster around offset. */ |
475 | start_offset = offset & ~mask; | |
476 | end_offset = offset | mask; | |
477 | if (!start_offset) /* First page is swap header. */ | |
478 | start_offset++; | |
479 | ||
3fb5c298 | 480 | blk_start_plug(&plug); |
67f96aa2 | 481 | for (offset = start_offset; offset <= end_offset ; offset++) { |
46017e95 HD |
482 | /* Ok, do the async read-ahead now */ |
483 | page = read_swap_cache_async(swp_entry(swp_type(entry), offset), | |
02098fea | 484 | gfp_mask, vma, addr); |
46017e95 | 485 | if (!page) |
67f96aa2 | 486 | continue; |
579f8290 SL |
487 | if (offset != entry_offset) |
488 | SetPageReadahead(page); | |
46017e95 HD |
489 | page_cache_release(page); |
490 | } | |
3fb5c298 CE |
491 | blk_finish_plug(&plug); |
492 | ||
46017e95 | 493 | lru_add_drain(); /* Push any new pages onto the LRU now */ |
579f8290 | 494 | skip: |
02098fea | 495 | return read_swap_cache_async(entry, gfp_mask, vma, addr); |
46017e95 | 496 | } |