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> |
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, |
62c230bc | 29 | .set_page_dirty = swap_set_page_dirty, |
1c93923c | 30 | #ifdef CONFIG_MIGRATION |
e965f963 | 31 | .migratepage = migrate_page, |
1c93923c | 32 | #endif |
1da177e4 LT |
33 | }; |
34 | ||
33806f06 SL |
35 | struct address_space swapper_spaces[MAX_SWAPFILES] = { |
36 | [0 ... MAX_SWAPFILES - 1] = { | |
37 | .page_tree = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN), | |
4bb5f5d9 | 38 | .i_mmap_writable = ATOMIC_INIT(0), |
33806f06 | 39 | .a_ops = &swap_aops, |
33806f06 | 40 | } |
1da177e4 | 41 | }; |
1da177e4 LT |
42 | |
43 | #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) | |
44 | ||
45 | static struct { | |
46 | unsigned long add_total; | |
47 | unsigned long del_total; | |
48 | unsigned long find_success; | |
49 | unsigned long find_total; | |
1da177e4 LT |
50 | } swap_cache_info; |
51 | ||
33806f06 SL |
52 | unsigned long total_swapcache_pages(void) |
53 | { | |
54 | int i; | |
55 | unsigned long ret = 0; | |
56 | ||
57 | for (i = 0; i < MAX_SWAPFILES; i++) | |
58 | ret += swapper_spaces[i].nrpages; | |
59 | return ret; | |
60 | } | |
61 | ||
579f8290 SL |
62 | static atomic_t swapin_readahead_hits = ATOMIC_INIT(4); |
63 | ||
1da177e4 LT |
64 | void show_swap_cache_info(void) |
65 | { | |
33806f06 | 66 | printk("%lu pages in swap cache\n", total_swapcache_pages()); |
2c97b7fc | 67 | printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n", |
1da177e4 | 68 | swap_cache_info.add_total, swap_cache_info.del_total, |
bb63be0a | 69 | swap_cache_info.find_success, swap_cache_info.find_total); |
ec8acf20 SL |
70 | printk("Free swap = %ldkB\n", |
71 | get_nr_swap_pages() << (PAGE_SHIFT - 10)); | |
1da177e4 LT |
72 | printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10)); |
73 | } | |
74 | ||
75 | /* | |
31a56396 | 76 | * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space, |
1da177e4 LT |
77 | * but sets SwapCache flag and private instead of mapping and index. |
78 | */ | |
2f772e6c | 79 | int __add_to_swap_cache(struct page *page, swp_entry_t entry) |
1da177e4 LT |
80 | { |
81 | int error; | |
33806f06 | 82 | struct address_space *address_space; |
1da177e4 | 83 | |
309381fe SL |
84 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
85 | VM_BUG_ON_PAGE(PageSwapCache(page), page); | |
86 | VM_BUG_ON_PAGE(!PageSwapBacked(page), page); | |
51726b12 | 87 | |
31a56396 DN |
88 | page_cache_get(page); |
89 | SetPageSwapCache(page); | |
90 | set_page_private(page, entry.val); | |
91 | ||
33806f06 SL |
92 | address_space = swap_address_space(entry); |
93 | spin_lock_irq(&address_space->tree_lock); | |
94 | error = radix_tree_insert(&address_space->page_tree, | |
95 | entry.val, page); | |
31a56396 | 96 | if (likely(!error)) { |
33806f06 | 97 | address_space->nrpages++; |
31a56396 DN |
98 | __inc_zone_page_state(page, NR_FILE_PAGES); |
99 | INC_CACHE_INFO(add_total); | |
100 | } | |
33806f06 | 101 | spin_unlock_irq(&address_space->tree_lock); |
31a56396 DN |
102 | |
103 | if (unlikely(error)) { | |
2ca4532a DN |
104 | /* |
105 | * Only the context which have set SWAP_HAS_CACHE flag | |
106 | * would call add_to_swap_cache(). | |
107 | * So add_to_swap_cache() doesn't returns -EEXIST. | |
108 | */ | |
109 | VM_BUG_ON(error == -EEXIST); | |
31a56396 DN |
110 | set_page_private(page, 0UL); |
111 | ClearPageSwapCache(page); | |
112 | page_cache_release(page); | |
113 | } | |
114 | ||
115 | return error; | |
116 | } | |
117 | ||
118 | ||
119 | int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask) | |
120 | { | |
121 | int error; | |
122 | ||
5e4c0d97 | 123 | error = radix_tree_maybe_preload(gfp_mask); |
35c754d7 | 124 | if (!error) { |
31a56396 | 125 | error = __add_to_swap_cache(page, entry); |
1da177e4 | 126 | radix_tree_preload_end(); |
fa1de900 | 127 | } |
1da177e4 LT |
128 | return error; |
129 | } | |
130 | ||
1da177e4 LT |
131 | /* |
132 | * This must be called only on pages that have | |
133 | * been verified to be in the swap cache. | |
134 | */ | |
135 | void __delete_from_swap_cache(struct page *page) | |
136 | { | |
33806f06 SL |
137 | swp_entry_t entry; |
138 | struct address_space *address_space; | |
139 | ||
309381fe SL |
140 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
141 | VM_BUG_ON_PAGE(!PageSwapCache(page), page); | |
142 | VM_BUG_ON_PAGE(PageWriteback(page), page); | |
1da177e4 | 143 | |
33806f06 SL |
144 | entry.val = page_private(page); |
145 | address_space = swap_address_space(entry); | |
146 | radix_tree_delete(&address_space->page_tree, page_private(page)); | |
4c21e2f2 | 147 | set_page_private(page, 0); |
1da177e4 | 148 | ClearPageSwapCache(page); |
33806f06 | 149 | address_space->nrpages--; |
347ce434 | 150 | __dec_zone_page_state(page, NR_FILE_PAGES); |
1da177e4 LT |
151 | INC_CACHE_INFO(del_total); |
152 | } | |
153 | ||
154 | /** | |
155 | * add_to_swap - allocate swap space for a page | |
156 | * @page: page we want to move to swap | |
157 | * | |
158 | * Allocate swap space for the page and add the page to the | |
159 | * swap cache. Caller needs to hold the page lock. | |
160 | */ | |
5bc7b8ac | 161 | int add_to_swap(struct page *page, struct list_head *list) |
1da177e4 LT |
162 | { |
163 | swp_entry_t entry; | |
1da177e4 LT |
164 | int err; |
165 | ||
309381fe SL |
166 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
167 | VM_BUG_ON_PAGE(!PageUptodate(page), page); | |
1da177e4 | 168 | |
2ca4532a DN |
169 | entry = get_swap_page(); |
170 | if (!entry.val) | |
171 | return 0; | |
172 | ||
3f04f62f | 173 | if (unlikely(PageTransHuge(page))) |
5bc7b8ac | 174 | if (unlikely(split_huge_page_to_list(page, list))) { |
0a31bc97 | 175 | swapcache_free(entry); |
3f04f62f AA |
176 | return 0; |
177 | } | |
178 | ||
2ca4532a DN |
179 | /* |
180 | * Radix-tree node allocations from PF_MEMALLOC contexts could | |
181 | * completely exhaust the page allocator. __GFP_NOMEMALLOC | |
182 | * stops emergency reserves from being allocated. | |
183 | * | |
184 | * TODO: this could cause a theoretical memory reclaim | |
185 | * deadlock in the swap out path. | |
186 | */ | |
187 | /* | |
854e9ed0 | 188 | * Add it to the swap cache. |
2ca4532a DN |
189 | */ |
190 | err = add_to_swap_cache(page, entry, | |
191 | __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); | |
192 | ||
854e9ed0 | 193 | if (!err) { |
2ca4532a DN |
194 | return 1; |
195 | } else { /* -ENOMEM radix-tree allocation failure */ | |
bd53b714 | 196 | /* |
2ca4532a DN |
197 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
198 | * clear SWAP_HAS_CACHE flag. | |
1da177e4 | 199 | */ |
0a31bc97 | 200 | swapcache_free(entry); |
2ca4532a | 201 | return 0; |
1da177e4 LT |
202 | } |
203 | } | |
204 | ||
205 | /* | |
206 | * This must be called only on pages that have | |
207 | * been verified to be in the swap cache and locked. | |
208 | * It will never put the page into the free list, | |
209 | * the caller has a reference on the page. | |
210 | */ | |
211 | void delete_from_swap_cache(struct page *page) | |
212 | { | |
213 | swp_entry_t entry; | |
33806f06 | 214 | struct address_space *address_space; |
1da177e4 | 215 | |
4c21e2f2 | 216 | entry.val = page_private(page); |
1da177e4 | 217 | |
33806f06 SL |
218 | address_space = swap_address_space(entry); |
219 | spin_lock_irq(&address_space->tree_lock); | |
1da177e4 | 220 | __delete_from_swap_cache(page); |
33806f06 | 221 | spin_unlock_irq(&address_space->tree_lock); |
1da177e4 | 222 | |
0a31bc97 | 223 | swapcache_free(entry); |
1da177e4 LT |
224 | page_cache_release(page); |
225 | } | |
226 | ||
1da177e4 LT |
227 | /* |
228 | * If we are the only user, then try to free up the swap cache. | |
229 | * | |
230 | * Its ok to check for PageSwapCache without the page lock | |
a2c43eed HD |
231 | * here because we are going to recheck again inside |
232 | * try_to_free_swap() _with_ the lock. | |
1da177e4 LT |
233 | * - Marcelo |
234 | */ | |
235 | static inline void free_swap_cache(struct page *page) | |
236 | { | |
a2c43eed HD |
237 | if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { |
238 | try_to_free_swap(page); | |
1da177e4 LT |
239 | unlock_page(page); |
240 | } | |
241 | } | |
242 | ||
243 | /* | |
244 | * Perform a free_page(), also freeing any swap cache associated with | |
b8072f09 | 245 | * this page if it is the last user of the page. |
1da177e4 LT |
246 | */ |
247 | void free_page_and_swap_cache(struct page *page) | |
248 | { | |
249 | free_swap_cache(page); | |
250 | page_cache_release(page); | |
251 | } | |
252 | ||
253 | /* | |
254 | * Passed an array of pages, drop them all from swapcache and then release | |
255 | * them. They are removed from the LRU and freed if this is their last use. | |
256 | */ | |
257 | void free_pages_and_swap_cache(struct page **pages, int nr) | |
258 | { | |
1da177e4 | 259 | struct page **pagep = pages; |
aabfb572 | 260 | int i; |
1da177e4 LT |
261 | |
262 | lru_add_drain(); | |
aabfb572 MH |
263 | for (i = 0; i < nr; i++) |
264 | free_swap_cache(pagep[i]); | |
265 | release_pages(pagep, nr, false); | |
1da177e4 LT |
266 | } |
267 | ||
268 | /* | |
269 | * Lookup a swap entry in the swap cache. A found page will be returned | |
270 | * unlocked and with its refcount incremented - we rely on the kernel | |
271 | * lock getting page table operations atomic even if we drop the page | |
272 | * lock before returning. | |
273 | */ | |
274 | struct page * lookup_swap_cache(swp_entry_t entry) | |
275 | { | |
276 | struct page *page; | |
277 | ||
33806f06 | 278 | page = find_get_page(swap_address_space(entry), entry.val); |
1da177e4 | 279 | |
579f8290 | 280 | if (page) { |
1da177e4 | 281 | INC_CACHE_INFO(find_success); |
579f8290 SL |
282 | if (TestClearPageReadahead(page)) |
283 | atomic_inc(&swapin_readahead_hits); | |
284 | } | |
1da177e4 LT |
285 | |
286 | INC_CACHE_INFO(find_total); | |
287 | return page; | |
288 | } | |
289 | ||
5b999aad DS |
290 | struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
291 | struct vm_area_struct *vma, unsigned long addr, | |
292 | bool *new_page_allocated) | |
1da177e4 LT |
293 | { |
294 | struct page *found_page, *new_page = NULL; | |
5b999aad | 295 | struct address_space *swapper_space = swap_address_space(entry); |
1da177e4 | 296 | int err; |
5b999aad | 297 | *new_page_allocated = false; |
1da177e4 LT |
298 | |
299 | do { | |
300 | /* | |
301 | * First check the swap cache. Since this is normally | |
302 | * called after lookup_swap_cache() failed, re-calling | |
303 | * that would confuse statistics. | |
304 | */ | |
5b999aad | 305 | found_page = find_get_page(swapper_space, entry.val); |
1da177e4 LT |
306 | if (found_page) |
307 | break; | |
308 | ||
309 | /* | |
310 | * Get a new page to read into from swap. | |
311 | */ | |
312 | if (!new_page) { | |
02098fea | 313 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
1da177e4 LT |
314 | if (!new_page) |
315 | break; /* Out of memory */ | |
316 | } | |
317 | ||
31a56396 DN |
318 | /* |
319 | * call radix_tree_preload() while we can wait. | |
320 | */ | |
5e4c0d97 | 321 | err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL); |
31a56396 DN |
322 | if (err) |
323 | break; | |
324 | ||
f000944d HD |
325 | /* |
326 | * Swap entry may have been freed since our caller observed it. | |
327 | */ | |
355cfa73 | 328 | err = swapcache_prepare(entry); |
cbab0e4e | 329 | if (err == -EEXIST) { |
31a56396 | 330 | radix_tree_preload_end(); |
cbab0e4e RA |
331 | /* |
332 | * We might race against get_swap_page() and stumble | |
333 | * across a SWAP_HAS_CACHE swap_map entry whose page | |
334 | * has not been brought into the swapcache yet, while | |
335 | * the other end is scheduled away waiting on discard | |
336 | * I/O completion at scan_swap_map(). | |
337 | * | |
338 | * In order to avoid turning this transitory state | |
339 | * into a permanent loop around this -EEXIST case | |
340 | * if !CONFIG_PREEMPT and the I/O completion happens | |
341 | * to be waiting on the CPU waitqueue where we are now | |
342 | * busy looping, we just conditionally invoke the | |
343 | * scheduler here, if there are some more important | |
344 | * tasks to run. | |
345 | */ | |
346 | cond_resched(); | |
355cfa73 | 347 | continue; |
31a56396 DN |
348 | } |
349 | if (err) { /* swp entry is obsolete ? */ | |
350 | radix_tree_preload_end(); | |
f000944d | 351 | break; |
31a56396 | 352 | } |
f000944d | 353 | |
2ca4532a | 354 | /* May fail (-ENOMEM) if radix-tree node allocation failed. */ |
48c935ad | 355 | __SetPageLocked(new_page); |
b2e18538 | 356 | SetPageSwapBacked(new_page); |
31a56396 | 357 | err = __add_to_swap_cache(new_page, entry); |
529ae9aa | 358 | if (likely(!err)) { |
31a56396 | 359 | radix_tree_preload_end(); |
1da177e4 LT |
360 | /* |
361 | * Initiate read into locked page and return. | |
362 | */ | |
c5fdae46 | 363 | lru_cache_add_anon(new_page); |
5b999aad | 364 | *new_page_allocated = true; |
1da177e4 LT |
365 | return new_page; |
366 | } | |
31a56396 | 367 | radix_tree_preload_end(); |
b2e18538 | 368 | ClearPageSwapBacked(new_page); |
48c935ad | 369 | __ClearPageLocked(new_page); |
2ca4532a DN |
370 | /* |
371 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely | |
372 | * clear SWAP_HAS_CACHE flag. | |
373 | */ | |
0a31bc97 | 374 | swapcache_free(entry); |
f000944d | 375 | } while (err != -ENOMEM); |
1da177e4 LT |
376 | |
377 | if (new_page) | |
378 | page_cache_release(new_page); | |
379 | return found_page; | |
380 | } | |
46017e95 | 381 | |
5b999aad DS |
382 | /* |
383 | * Locate a page of swap in physical memory, reserving swap cache space | |
384 | * and reading the disk if it is not already cached. | |
385 | * A failure return means that either the page allocation failed or that | |
386 | * the swap entry is no longer in use. | |
387 | */ | |
388 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, | |
389 | struct vm_area_struct *vma, unsigned long addr) | |
390 | { | |
391 | bool page_was_allocated; | |
392 | struct page *retpage = __read_swap_cache_async(entry, gfp_mask, | |
393 | vma, addr, &page_was_allocated); | |
394 | ||
395 | if (page_was_allocated) | |
396 | swap_readpage(retpage); | |
397 | ||
398 | return retpage; | |
399 | } | |
400 | ||
579f8290 SL |
401 | static unsigned long swapin_nr_pages(unsigned long offset) |
402 | { | |
403 | static unsigned long prev_offset; | |
404 | unsigned int pages, max_pages, last_ra; | |
405 | static atomic_t last_readahead_pages; | |
406 | ||
4db0c3c2 | 407 | max_pages = 1 << READ_ONCE(page_cluster); |
579f8290 SL |
408 | if (max_pages <= 1) |
409 | return 1; | |
410 | ||
411 | /* | |
412 | * This heuristic has been found to work well on both sequential and | |
413 | * random loads, swapping to hard disk or to SSD: please don't ask | |
414 | * what the "+ 2" means, it just happens to work well, that's all. | |
415 | */ | |
416 | pages = atomic_xchg(&swapin_readahead_hits, 0) + 2; | |
417 | if (pages == 2) { | |
418 | /* | |
419 | * We can have no readahead hits to judge by: but must not get | |
420 | * stuck here forever, so check for an adjacent offset instead | |
421 | * (and don't even bother to check whether swap type is same). | |
422 | */ | |
423 | if (offset != prev_offset + 1 && offset != prev_offset - 1) | |
424 | pages = 1; | |
425 | prev_offset = offset; | |
426 | } else { | |
427 | unsigned int roundup = 4; | |
428 | while (roundup < pages) | |
429 | roundup <<= 1; | |
430 | pages = roundup; | |
431 | } | |
432 | ||
433 | if (pages > max_pages) | |
434 | pages = max_pages; | |
435 | ||
436 | /* Don't shrink readahead too fast */ | |
437 | last_ra = atomic_read(&last_readahead_pages) / 2; | |
438 | if (pages < last_ra) | |
439 | pages = last_ra; | |
440 | atomic_set(&last_readahead_pages, pages); | |
441 | ||
442 | return pages; | |
443 | } | |
444 | ||
46017e95 HD |
445 | /** |
446 | * swapin_readahead - swap in pages in hope we need them soon | |
447 | * @entry: swap entry of this memory | |
7682486b | 448 | * @gfp_mask: memory allocation flags |
46017e95 HD |
449 | * @vma: user vma this address belongs to |
450 | * @addr: target address for mempolicy | |
451 | * | |
452 | * Returns the struct page for entry and addr, after queueing swapin. | |
453 | * | |
454 | * Primitive swap readahead code. We simply read an aligned block of | |
455 | * (1 << page_cluster) entries in the swap area. This method is chosen | |
456 | * because it doesn't cost us any seek time. We also make sure to queue | |
457 | * the 'original' request together with the readahead ones... | |
458 | * | |
459 | * This has been extended to use the NUMA policies from the mm triggering | |
460 | * the readahead. | |
461 | * | |
462 | * Caller must hold down_read on the vma->vm_mm if vma is not NULL. | |
463 | */ | |
02098fea | 464 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
46017e95 HD |
465 | struct vm_area_struct *vma, unsigned long addr) |
466 | { | |
46017e95 | 467 | struct page *page; |
579f8290 SL |
468 | unsigned long entry_offset = swp_offset(entry); |
469 | unsigned long offset = entry_offset; | |
67f96aa2 | 470 | unsigned long start_offset, end_offset; |
579f8290 | 471 | unsigned long mask; |
3fb5c298 | 472 | struct blk_plug plug; |
46017e95 | 473 | |
579f8290 SL |
474 | mask = swapin_nr_pages(offset) - 1; |
475 | if (!mask) | |
476 | goto skip; | |
477 | ||
67f96aa2 RR |
478 | /* Read a page_cluster sized and aligned cluster around offset. */ |
479 | start_offset = offset & ~mask; | |
480 | end_offset = offset | mask; | |
481 | if (!start_offset) /* First page is swap header. */ | |
482 | start_offset++; | |
483 | ||
3fb5c298 | 484 | blk_start_plug(&plug); |
67f96aa2 | 485 | for (offset = start_offset; offset <= end_offset ; offset++) { |
46017e95 HD |
486 | /* Ok, do the async read-ahead now */ |
487 | page = read_swap_cache_async(swp_entry(swp_type(entry), offset), | |
02098fea | 488 | gfp_mask, vma, addr); |
46017e95 | 489 | if (!page) |
67f96aa2 | 490 | continue; |
579f8290 SL |
491 | if (offset != entry_offset) |
492 | SetPageReadahead(page); | |
46017e95 HD |
493 | page_cache_release(page); |
494 | } | |
3fb5c298 CE |
495 | blk_finish_plug(&plug); |
496 | ||
46017e95 | 497 | lru_add_drain(); /* Push any new pages onto the LRU now */ |
579f8290 | 498 | skip: |
02098fea | 499 | return read_swap_cache_async(entry, gfp_mask, vma, addr); |
46017e95 | 500 | } |