1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * linux/mm/swap_state.c |
4 | * |
5 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
6 | * Swap reorganised 29.12.95, Stephen Tweedie |
7 | * |
8 | * Rewritten to use page cache, (C) 1998 Stephen Tweedie |
9 | */ |
10 | #include <linux/mm.h> |
11 | #include <linux/gfp.h> |
12 | #include <linux/kernel_stat.h> |
13 | #include <linux/swap.h> |
14 | #include <linux/swapops.h> |
15 | #include <linux/init.h> |
16 | #include <linux/pagemap.h> |
17 | #include <linux/backing-dev.h> |
18 | #include <linux/blkdev.h> |
19 | #include <linux/pagevec.h> |
20 | #include <linux/migrate.h> |
21 | #include <linux/vmalloc.h> |
22 | #include <linux/swap_slots.h> |
23 | #include <linux/huge_mm.h> |
24 | |
25 | #include <asm/pgtable.h> |
26 | |
27 | /* |
28 | * swapper_space is a fiction, retained to simplify the path through |
29 | * vmscan's shrink_page_list. |
30 | */ |
31 | static const struct address_space_operations swap_aops = { |
32 | .writepage = swap_writepage, |
33 | .set_page_dirty = swap_set_page_dirty, |
34 | #ifdef CONFIG_MIGRATION |
35 | .migratepage = migrate_page, |
36 | #endif |
37 | }; |
38 | |
39 | struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly; |
40 | static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly; |
41 | static bool enable_vma_readahead __read_mostly = true; |
42 | |
43 | #define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2) |
44 | #define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1) |
45 | #define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK |
46 | #define SWAP_RA_WIN_MASK (~PAGE_MASK & ~SWAP_RA_HITS_MASK) |
47 | |
48 | #define SWAP_RA_HITS(v) ((v) & SWAP_RA_HITS_MASK) |
49 | #define SWAP_RA_WIN(v) (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT) |
50 | #define SWAP_RA_ADDR(v) ((v) & PAGE_MASK) |
51 | |
52 | #define SWAP_RA_VAL(addr, win, hits) \ |
53 | (((addr) & PAGE_MASK) | \ |
54 | (((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) | \ |
55 | ((hits) & SWAP_RA_HITS_MASK)) |
56 | |
57 | /* Initial readahead hits is 4 to start up with a small window */ |
58 | #define GET_SWAP_RA_VAL(vma) \ |
59 | (atomic_long_read(&(vma)->swap_readahead_info) ? : 4) |
60 | |
61 | #define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0) |
62 | #define ADD_CACHE_INFO(x, nr) do { swap_cache_info.x += (nr); } while (0) |
63 | |
64 | static struct { |
65 | unsigned long add_total; |
66 | unsigned long del_total; |
67 | unsigned long find_success; |
68 | unsigned long find_total; |
69 | } swap_cache_info; |
70 | |
71 | unsigned long total_swapcache_pages(void) |
72 | { |
73 | unsigned int i, j, nr; |
74 | unsigned long ret = 0; |
75 | struct address_space *spaces; |
76 | |
77 | rcu_read_lock(); |
78 | for (i = 0; i < MAX_SWAPFILES; i++) { |
79 | /* |
80 | * The corresponding entries in nr_swapper_spaces and |
81 | * swapper_spaces will be reused only after at least |
82 | * one grace period. So it is impossible for them |
83 | * belongs to different usage. |
84 | */ |
85 | nr = nr_swapper_spaces[i]; |
86 | spaces = rcu_dereference(swapper_spaces[i]); |
87 | if (!nr || !spaces) |
88 | continue; |
89 | for (j = 0; j < nr; j++) |
90 | ret += spaces[j].nrpages; |
91 | } |
92 | rcu_read_unlock(); |
93 | return ret; |
94 | } |
95 | |
96 | static atomic_t swapin_readahead_hits = ATOMIC_INIT(4); |
97 | |
98 | void show_swap_cache_info(void) |
99 | { |
100 | printk("%lu pages in swap cache\n" , total_swapcache_pages()); |
101 | printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n" , |
102 | swap_cache_info.add_total, swap_cache_info.del_total, |
103 | swap_cache_info.find_success, swap_cache_info.find_total); |
104 | printk("Free swap = %ldkB\n" , |
105 | get_nr_swap_pages() << (PAGE_SHIFT - 10)); |
106 | printk("Total swap = %lukB\n" , total_swap_pages << (PAGE_SHIFT - 10)); |
107 | } |
108 | |
109 | /* |
110 | * add_to_swap_cache resembles add_to_page_cache_locked on swapper_space, |
111 | * but sets SwapCache flag and private instead of mapping and index. |
112 | */ |
113 | int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp) |
114 | { |
115 | struct address_space *address_space = swap_address_space(entry); |
116 | pgoff_t idx = swp_offset(entry); |
117 | XA_STATE_ORDER(xas, &address_space->i_pages, idx, compound_order(page)); |
118 | unsigned long i, nr = 1UL << compound_order(page); |
119 | |
120 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
121 | VM_BUG_ON_PAGE(PageSwapCache(page), page); |
122 | VM_BUG_ON_PAGE(!PageSwapBacked(page), page); |
123 | |
124 | page_ref_add(page, nr); |
125 | SetPageSwapCache(page); |
126 | |
127 | do { |
128 | xas_lock_irq(&xas); |
129 | xas_create_range(&xas); |
130 | if (xas_error(&xas)) |
131 | goto unlock; |
132 | for (i = 0; i < nr; i++) { |
133 | VM_BUG_ON_PAGE(xas.xa_index != idx + i, page); |
134 | set_page_private(page + i, entry.val + i); |
135 | xas_store(&xas, page + i); |
136 | xas_next(&xas); |
137 | } |
138 | address_space->nrpages += nr; |
139 | __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr); |
140 | ADD_CACHE_INFO(add_total, nr); |
141 | unlock: |
142 | xas_unlock_irq(&xas); |
143 | } while (xas_nomem(&xas, gfp)); |
144 | |
145 | if (!xas_error(&xas)) |
146 | return 0; |
147 | |
148 | ClearPageSwapCache(page); |
149 | page_ref_sub(page, nr); |
150 | return xas_error(&xas); |
151 | } |
152 | |
153 | /* |
154 | * This must be called only on pages that have |
155 | * been verified to be in the swap cache. |
156 | */ |
157 | void __delete_from_swap_cache(struct page *page, swp_entry_t entry) |
158 | { |
159 | struct address_space *address_space = swap_address_space(entry); |
160 | int i, nr = hpage_nr_pages(page); |
161 | pgoff_t idx = swp_offset(entry); |
162 | XA_STATE(xas, &address_space->i_pages, idx); |
163 | |
164 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
165 | VM_BUG_ON_PAGE(!PageSwapCache(page), page); |
166 | VM_BUG_ON_PAGE(PageWriteback(page), page); |
167 | |
168 | for (i = 0; i < nr; i++) { |
169 | void *entry = xas_store(&xas, NULL); |
170 | VM_BUG_ON_PAGE(entry != page + i, entry); |
171 | set_page_private(page + i, 0); |
172 | xas_next(&xas); |
173 | } |
174 | ClearPageSwapCache(page); |
175 | address_space->nrpages -= nr; |
176 | __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr); |
177 | ADD_CACHE_INFO(del_total, nr); |
178 | } |
179 | |
180 | /** |
181 | * add_to_swap - allocate swap space for a page |
182 | * @page: page we want to move to swap |
183 | * |
184 | * Allocate swap space for the page and add the page to the |
185 | * swap cache. Caller needs to hold the page lock. |
186 | */ |
187 | int add_to_swap(struct page *page) |
188 | { |
189 | swp_entry_t entry; |
190 | int err; |
191 | |
192 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
193 | VM_BUG_ON_PAGE(!PageUptodate(page), page); |
194 | |
195 | entry = get_swap_page(page); |
196 | if (!entry.val) |
197 | return 0; |
198 | |
199 | /* |
200 | * XArray node allocations from PF_MEMALLOC contexts could |
201 | * completely exhaust the page allocator. __GFP_NOMEMALLOC |
202 | * stops emergency reserves from being allocated. |
203 | * |
204 | * TODO: this could cause a theoretical memory reclaim |
205 | * deadlock in the swap out path. |
206 | */ |
207 | /* |
208 | * Add it to the swap cache. |
209 | */ |
210 | err = add_to_swap_cache(page, entry, |
211 | __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN); |
212 | if (err) |
213 | /* |
214 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
215 | * clear SWAP_HAS_CACHE flag. |
216 | */ |
217 | goto fail; |
218 | /* |
219 | * Normally the page will be dirtied in unmap because its pte should be |
220 | * dirty. A special case is MADV_FREE page. The page'e pte could have |
221 | * dirty bit cleared but the page's SwapBacked bit is still set because |
222 | * clearing the dirty bit and SwapBacked bit has no lock protected. For |
223 | * such page, unmap will not set dirty bit for it, so page reclaim will |
224 | * not write the page out. This can cause data corruption when the page |
225 | * is swap in later. Always setting the dirty bit for the page solves |
226 | * the problem. |
227 | */ |
228 | set_page_dirty(page); |
229 | |
230 | return 1; |
231 | |
232 | fail: |
233 | put_swap_page(page, entry); |
234 | return 0; |
235 | } |
236 | |
237 | /* |
238 | * This must be called only on pages that have |
239 | * been verified to be in the swap cache and locked. |
240 | * It will never put the page into the free list, |
241 | * the caller has a reference on the page. |
242 | */ |
243 | void delete_from_swap_cache(struct page *page) |
244 | { |
245 | swp_entry_t entry = { .val = page_private(page) }; |
246 | struct address_space *address_space = swap_address_space(entry); |
247 | |
248 | xa_lock_irq(&address_space->i_pages); |
249 | __delete_from_swap_cache(page, entry); |
250 | xa_unlock_irq(&address_space->i_pages); |
251 | |
252 | put_swap_page(page, entry); |
253 | page_ref_sub(page, hpage_nr_pages(page)); |
254 | } |
255 | |
256 | /* |
257 | * If we are the only user, then try to free up the swap cache. |
258 | * |
259 | * Its ok to check for PageSwapCache without the page lock |
260 | * here because we are going to recheck again inside |
261 | * try_to_free_swap() _with_ the lock. |
262 | * - Marcelo |
263 | */ |
264 | static inline void free_swap_cache(struct page *page) |
265 | { |
266 | if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) { |
267 | try_to_free_swap(page); |
268 | unlock_page(page); |
269 | } |
270 | } |
271 | |
272 | /* |
273 | * Perform a free_page(), also freeing any swap cache associated with |
274 | * this page if it is the last user of the page. |
275 | */ |
276 | void free_page_and_swap_cache(struct page *page) |
277 | { |
278 | free_swap_cache(page); |
279 | if (!is_huge_zero_page(page)) |
280 | put_page(page); |
281 | } |
282 | |
283 | /* |
284 | * Passed an array of pages, drop them all from swapcache and then release |
285 | * them. They are removed from the LRU and freed if this is their last use. |
286 | */ |
287 | void free_pages_and_swap_cache(struct page **pages, int nr) |
288 | { |
289 | struct page **pagep = pages; |
290 | int i; |
291 | |
292 | lru_add_drain(); |
293 | for (i = 0; i < nr; i++) |
294 | free_swap_cache(pagep[i]); |
295 | release_pages(pagep, nr); |
296 | } |
297 | |
298 | static inline bool swap_use_vma_readahead(void) |
299 | { |
300 | return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap); |
301 | } |
302 | |
303 | /* |
304 | * Lookup a swap entry in the swap cache. A found page will be returned |
305 | * unlocked and with its refcount incremented - we rely on the kernel |
306 | * lock getting page table operations atomic even if we drop the page |
307 | * lock before returning. |
308 | */ |
309 | struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma, |
310 | unsigned long addr) |
311 | { |
312 | struct page *page; |
313 | |
314 | page = find_get_page(swap_address_space(entry), swp_offset(entry)); |
315 | |
316 | INC_CACHE_INFO(find_total); |
317 | if (page) { |
318 | bool vma_ra = swap_use_vma_readahead(); |
319 | bool readahead; |
320 | |
321 | INC_CACHE_INFO(find_success); |
322 | /* |
323 | * At the moment, we don't support PG_readahead for anon THP |
324 | * so let's bail out rather than confusing the readahead stat. |
325 | */ |
326 | if (unlikely(PageTransCompound(page))) |
327 | return page; |
328 | |
329 | readahead = TestClearPageReadahead(page); |
330 | if (vma && vma_ra) { |
331 | unsigned long ra_val; |
332 | int win, hits; |
333 | |
334 | ra_val = GET_SWAP_RA_VAL(vma); |
335 | win = SWAP_RA_WIN(ra_val); |
336 | hits = SWAP_RA_HITS(ra_val); |
337 | if (readahead) |
338 | hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX); |
339 | atomic_long_set(&vma->swap_readahead_info, |
340 | SWAP_RA_VAL(addr, win, hits)); |
341 | } |
342 | |
343 | if (readahead) { |
344 | count_vm_event(SWAP_RA_HIT); |
345 | if (!vma || !vma_ra) |
346 | atomic_inc(&swapin_readahead_hits); |
347 | } |
348 | } |
349 | |
350 | return page; |
351 | } |
352 | |
353 | struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
354 | struct vm_area_struct *vma, unsigned long addr, |
355 | bool *new_page_allocated) |
356 | { |
357 | struct page *found_page, *new_page = NULL; |
358 | struct address_space *swapper_space = swap_address_space(entry); |
359 | int err; |
360 | *new_page_allocated = false; |
361 | |
362 | do { |
363 | /* |
364 | * First check the swap cache. Since this is normally |
365 | * called after lookup_swap_cache() failed, re-calling |
366 | * that would confuse statistics. |
367 | */ |
368 | found_page = find_get_page(swapper_space, swp_offset(entry)); |
369 | if (found_page) |
370 | break; |
371 | |
372 | /* |
373 | * Just skip read ahead for unused swap slot. |
374 | * During swap_off when swap_slot_cache is disabled, |
375 | * we have to handle the race between putting |
376 | * swap entry in swap cache and marking swap slot |
377 | * as SWAP_HAS_CACHE. That's done in later part of code or |
378 | * else swap_off will be aborted if we return NULL. |
379 | */ |
380 | if (!__swp_swapcount(entry) && swap_slot_cache_enabled) |
381 | break; |
382 | |
383 | /* |
384 | * Get a new page to read into from swap. |
385 | */ |
386 | if (!new_page) { |
387 | new_page = alloc_page_vma(gfp_mask, vma, addr); |
388 | if (!new_page) |
389 | break; /* Out of memory */ |
390 | } |
391 | |
392 | /* |
393 | * Swap entry may have been freed since our caller observed it. |
394 | */ |
395 | err = swapcache_prepare(entry); |
396 | if (err == -EEXIST) { |
397 | /* |
398 | * We might race against get_swap_page() and stumble |
399 | * across a SWAP_HAS_CACHE swap_map entry whose page |
400 | * has not been brought into the swapcache yet. |
401 | */ |
402 | cond_resched(); |
403 | continue; |
404 | } else if (err) /* swp entry is obsolete ? */ |
405 | break; |
406 | |
407 | /* May fail (-ENOMEM) if XArray node allocation failed. */ |
408 | __SetPageLocked(new_page); |
409 | __SetPageSwapBacked(new_page); |
410 | err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL); |
411 | if (likely(!err)) { |
412 | /* Initiate read into locked page */ |
413 | SetPageWorkingset(new_page); |
414 | lru_cache_add_anon(new_page); |
415 | *new_page_allocated = true; |
416 | return new_page; |
417 | } |
418 | __ClearPageLocked(new_page); |
419 | /* |
420 | * add_to_swap_cache() doesn't return -EEXIST, so we can safely |
421 | * clear SWAP_HAS_CACHE flag. |
422 | */ |
423 | put_swap_page(new_page, entry); |
424 | } while (err != -ENOMEM); |
425 | |
426 | if (new_page) |
427 | put_page(new_page); |
428 | return found_page; |
429 | } |
430 | |
431 | /* |
432 | * Locate a page of swap in physical memory, reserving swap cache space |
433 | * and reading the disk if it is not already cached. |
434 | * A failure return means that either the page allocation failed or that |
435 | * the swap entry is no longer in use. |
436 | */ |
437 | struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, |
438 | struct vm_area_struct *vma, unsigned long addr, bool do_poll) |
439 | { |
440 | bool page_was_allocated; |
441 | struct page *retpage = __read_swap_cache_async(entry, gfp_mask, |
442 | vma, addr, &page_was_allocated); |
443 | |
444 | if (page_was_allocated) |
445 | swap_readpage(retpage, do_poll); |
446 | |
447 | return retpage; |
448 | } |
449 | |
450 | static unsigned int __swapin_nr_pages(unsigned long prev_offset, |
451 | unsigned long offset, |
452 | int hits, |
453 | int max_pages, |
454 | int prev_win) |
455 | { |
456 | unsigned int pages, last_ra; |
457 | |
458 | /* |
459 | * This heuristic has been found to work well on both sequential and |
460 | * random loads, swapping to hard disk or to SSD: please don't ask |
461 | * what the "+ 2" means, it just happens to work well, that's all. |
462 | */ |
463 | pages = hits + 2; |
464 | if (pages == 2) { |
465 | /* |
466 | * We can have no readahead hits to judge by: but must not get |
467 | * stuck here forever, so check for an adjacent offset instead |
468 | * (and don't even bother to check whether swap type is same). |
469 | */ |
470 | if (offset != prev_offset + 1 && offset != prev_offset - 1) |
471 | pages = 1; |
472 | } else { |
473 | unsigned int roundup = 4; |
474 | while (roundup < pages) |
475 | roundup <<= 1; |
476 | pages = roundup; |
477 | } |
478 | |
479 | if (pages > max_pages) |
480 | pages = max_pages; |
481 | |
482 | /* Don't shrink readahead too fast */ |
483 | last_ra = prev_win / 2; |
484 | if (pages < last_ra) |
485 | pages = last_ra; |
486 | |
487 | return pages; |
488 | } |
489 | |
490 | static unsigned long swapin_nr_pages(unsigned long offset) |
491 | { |
492 | static unsigned long prev_offset; |
493 | unsigned int hits, pages, max_pages; |
494 | static atomic_t last_readahead_pages; |
495 | |
496 | max_pages = 1 << READ_ONCE(page_cluster); |
497 | if (max_pages <= 1) |
498 | return 1; |
499 | |
500 | hits = atomic_xchg(&swapin_readahead_hits, 0); |
501 | pages = __swapin_nr_pages(prev_offset, offset, hits, max_pages, |
502 | atomic_read(&last_readahead_pages)); |
503 | if (!hits) |
504 | prev_offset = offset; |
505 | atomic_set(&last_readahead_pages, pages); |
506 | |
507 | return pages; |
508 | } |
509 | |
510 | /** |
511 | * swap_cluster_readahead - swap in pages in hope we need them soon |
512 | * @entry: swap entry of this memory |
513 | * @gfp_mask: memory allocation flags |
514 | * @vmf: fault information |
515 | * |
516 | * Returns the struct page for entry and addr, after queueing swapin. |
517 | * |
518 | * Primitive swap readahead code. We simply read an aligned block of |
519 | * (1 << page_cluster) entries in the swap area. This method is chosen |
520 | * because it doesn't cost us any seek time. We also make sure to queue |
521 | * the 'original' request together with the readahead ones... |
522 | * |
523 | * This has been extended to use the NUMA policies from the mm triggering |
524 | * the readahead. |
525 | * |
526 | * Caller must hold read mmap_sem if vmf->vma is not NULL. |
527 | */ |
528 | struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, |
529 | struct vm_fault *vmf) |
530 | { |
531 | struct page *page; |
532 | unsigned long entry_offset = swp_offset(entry); |
533 | unsigned long offset = entry_offset; |
534 | unsigned long start_offset, end_offset; |
535 | unsigned long mask; |
536 | struct swap_info_struct *si = swp_swap_info(entry); |
537 | struct blk_plug plug; |
538 | bool do_poll = true, page_allocated; |
539 | struct vm_area_struct *vma = vmf->vma; |
540 | unsigned long addr = vmf->address; |
541 | |
542 | mask = swapin_nr_pages(offset) - 1; |
543 | if (!mask) |
544 | goto skip; |
545 | |
546 | /* Test swap type to make sure the dereference is safe */ |
547 | if (likely(si->flags & (SWP_BLKDEV | SWP_FS))) { |
548 | struct inode *inode = si->swap_file->f_mapping->host; |
549 | if (inode_read_congested(inode)) |
550 | goto skip; |
551 | } |
552 | |
553 | do_poll = false; |
554 | /* Read a page_cluster sized and aligned cluster around offset. */ |
555 | start_offset = offset & ~mask; |
556 | end_offset = offset | mask; |
557 | if (!start_offset) /* First page is swap header. */ |
558 | start_offset++; |
559 | if (end_offset >= si->max) |
560 | end_offset = si->max - 1; |
561 | |
562 | blk_start_plug(&plug); |
563 | for (offset = start_offset; offset <= end_offset ; offset++) { |
564 | /* Ok, do the async read-ahead now */ |
565 | page = __read_swap_cache_async( |
566 | swp_entry(swp_type(entry), offset), |
567 | gfp_mask, vma, addr, &page_allocated); |
568 | if (!page) |
569 | continue; |
570 | if (page_allocated) { |
571 | swap_readpage(page, false); |
572 | if (offset != entry_offset) { |
573 | SetPageReadahead(page); |
574 | count_vm_event(SWAP_RA); |
575 | } |
576 | } |
577 | put_page(page); |
578 | } |
579 | blk_finish_plug(&plug); |
580 | |
581 | lru_add_drain(); /* Push any new pages onto the LRU now */ |
582 | skip: |
583 | return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll); |
584 | } |
585 | |
586 | int init_swap_address_space(unsigned int type, unsigned long nr_pages) |
587 | { |
588 | struct address_space *spaces, *space; |
589 | unsigned int i, nr; |
590 | |
591 | nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES); |
592 | spaces = kvcalloc(nr, sizeof(struct address_space), GFP_KERNEL); |
593 | if (!spaces) |
594 | return -ENOMEM; |
595 | for (i = 0; i < nr; i++) { |
596 | space = spaces + i; |
597 | xa_init_flags(&space->i_pages, XA_FLAGS_LOCK_IRQ); |
598 | atomic_set(&space->i_mmap_writable, 0); |
599 | space->a_ops = &swap_aops; |
600 | /* swap cache doesn't use writeback related tags */ |
601 | mapping_set_no_writeback_tags(space); |
602 | } |
603 | nr_swapper_spaces[type] = nr; |
604 | rcu_assign_pointer(swapper_spaces[type], spaces); |
605 | |
606 | return 0; |
607 | } |
608 | |
609 | void exit_swap_address_space(unsigned int type) |
610 | { |
611 | struct address_space *spaces; |
612 | |
613 | spaces = swapper_spaces[type]; |
614 | nr_swapper_spaces[type] = 0; |
615 | rcu_assign_pointer(swapper_spaces[type], NULL); |
616 | synchronize_rcu(); |
617 | kvfree(spaces); |
618 | } |
619 | |
620 | static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma, |
621 | unsigned long faddr, |
622 | unsigned long lpfn, |
623 | unsigned long rpfn, |
624 | unsigned long *start, |
625 | unsigned long *end) |
626 | { |
627 | *start = max3(lpfn, PFN_DOWN(vma->vm_start), |
628 | PFN_DOWN(faddr & PMD_MASK)); |
629 | *end = min3(rpfn, PFN_DOWN(vma->vm_end), |
630 | PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE)); |
631 | } |
632 | |
633 | static void swap_ra_info(struct vm_fault *vmf, |
634 | struct vma_swap_readahead *ra_info) |
635 | { |
636 | struct vm_area_struct *vma = vmf->vma; |
637 | unsigned long ra_val; |
638 | swp_entry_t entry; |
639 | unsigned long faddr, pfn, fpfn; |
640 | unsigned long start, end; |
641 | pte_t *pte, *orig_pte; |
642 | unsigned int max_win, hits, prev_win, win, left; |
643 | #ifndef CONFIG_64BIT |
644 | pte_t *tpte; |
645 | #endif |
646 | |
647 | max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster), |
648 | SWAP_RA_ORDER_CEILING); |
649 | if (max_win == 1) { |
650 | ra_info->win = 1; |
651 | return; |
652 | } |
653 | |
654 | faddr = vmf->address; |
655 | orig_pte = pte = pte_offset_map(vmf->pmd, faddr); |
656 | entry = pte_to_swp_entry(*pte); |
657 | if ((unlikely(non_swap_entry(entry)))) { |
658 | pte_unmap(orig_pte); |
659 | return; |
660 | } |
661 | |
662 | fpfn = PFN_DOWN(faddr); |
663 | ra_val = GET_SWAP_RA_VAL(vma); |
664 | pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val)); |
665 | prev_win = SWAP_RA_WIN(ra_val); |
666 | hits = SWAP_RA_HITS(ra_val); |
667 | ra_info->win = win = __swapin_nr_pages(pfn, fpfn, hits, |
668 | max_win, prev_win); |
669 | atomic_long_set(&vma->swap_readahead_info, |
670 | SWAP_RA_VAL(faddr, win, 0)); |
671 | |
672 | if (win == 1) { |
673 | pte_unmap(orig_pte); |
674 | return; |
675 | } |
676 | |
677 | /* Copy the PTEs because the page table may be unmapped */ |
678 | if (fpfn == pfn + 1) |
679 | swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end); |
680 | else if (pfn == fpfn + 1) |
681 | swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1, |
682 | &start, &end); |
683 | else { |
684 | left = (win - 1) / 2; |
685 | swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left, |
686 | &start, &end); |
687 | } |
688 | ra_info->nr_pte = end - start; |
689 | ra_info->offset = fpfn - start; |
690 | pte -= ra_info->offset; |
691 | #ifdef CONFIG_64BIT |
692 | ra_info->ptes = pte; |
693 | #else |
694 | tpte = ra_info->ptes; |
695 | for (pfn = start; pfn != end; pfn++) |
696 | *tpte++ = *pte++; |
697 | #endif |
698 | pte_unmap(orig_pte); |
699 | } |
700 | |
701 | /** |
702 | * swap_vma_readahead - swap in pages in hope we need them soon |
703 | * @entry: swap entry of this memory |
704 | * @gfp_mask: memory allocation flags |
705 | * @vmf: fault information |
706 | * |
707 | * Returns the struct page for entry and addr, after queueing swapin. |
708 | * |
709 | * Primitive swap readahead code. We simply read in a few pages whoes |
710 | * virtual addresses are around the fault address in the same vma. |
711 | * |
712 | * Caller must hold read mmap_sem if vmf->vma is not NULL. |
713 | * |
714 | */ |
715 | static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask, |
716 | struct vm_fault *vmf) |
717 | { |
718 | struct blk_plug plug; |
719 | struct vm_area_struct *vma = vmf->vma; |
720 | struct page *page; |
721 | pte_t *pte, pentry; |
722 | swp_entry_t entry; |
723 | unsigned int i; |
724 | bool page_allocated; |
725 | struct vma_swap_readahead ra_info = {0,}; |
726 | |
727 | swap_ra_info(vmf, &ra_info); |
728 | if (ra_info.win == 1) |
729 | goto skip; |
730 | |
731 | blk_start_plug(&plug); |
732 | for (i = 0, pte = ra_info.ptes; i < ra_info.nr_pte; |
733 | i++, pte++) { |
734 | pentry = *pte; |
735 | if (pte_none(pentry)) |
736 | continue; |
737 | if (pte_present(pentry)) |
738 | continue; |
739 | entry = pte_to_swp_entry(pentry); |
740 | if (unlikely(non_swap_entry(entry))) |
741 | continue; |
742 | page = __read_swap_cache_async(entry, gfp_mask, vma, |
743 | vmf->address, &page_allocated); |
744 | if (!page) |
745 | continue; |
746 | if (page_allocated) { |
747 | swap_readpage(page, false); |
748 | if (i != ra_info.offset) { |
749 | SetPageReadahead(page); |
750 | count_vm_event(SWAP_RA); |
751 | } |
752 | } |
753 | put_page(page); |
754 | } |
755 | blk_finish_plug(&plug); |
756 | lru_add_drain(); |
757 | skip: |
758 | return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address, |
759 | ra_info.win == 1); |
760 | } |
761 | |
762 | /** |
763 | * swapin_readahead - swap in pages in hope we need them soon |
764 | * @entry: swap entry of this memory |
765 | * @gfp_mask: memory allocation flags |
766 | * @vmf: fault information |
767 | * |
768 | * Returns the struct page for entry and addr, after queueing swapin. |
769 | * |
770 | * It's a main entry function for swap readahead. By the configuration, |
771 | * it will read ahead blocks by cluster-based(ie, physical disk based) |
772 | * or vma-based(ie, virtual address based on faulty address) readahead. |
773 | */ |
774 | struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask, |
775 | struct vm_fault *vmf) |
776 | { |
777 | return swap_use_vma_readahead() ? |
778 | swap_vma_readahead(entry, gfp_mask, vmf) : |
779 | swap_cluster_readahead(entry, gfp_mask, vmf); |
780 | } |
781 | |
782 | #ifdef CONFIG_SYSFS |
783 | static ssize_t vma_ra_enabled_show(struct kobject *kobj, |
784 | struct kobj_attribute *attr, char *buf) |
785 | { |
786 | return sprintf(buf, "%s\n" , enable_vma_readahead ? "true" : "false" ); |
787 | } |
788 | static ssize_t vma_ra_enabled_store(struct kobject *kobj, |
789 | struct kobj_attribute *attr, |
790 | const char *buf, size_t count) |
791 | { |
792 | if (!strncmp(buf, "true" , 4) || !strncmp(buf, "1" , 1)) |
793 | enable_vma_readahead = true; |
794 | else if (!strncmp(buf, "false" , 5) || !strncmp(buf, "0" , 1)) |
795 | enable_vma_readahead = false; |
796 | else |
797 | return -EINVAL; |
798 | |
799 | return count; |
800 | } |
801 | static struct kobj_attribute vma_ra_enabled_attr = |
802 | __ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show, |
803 | vma_ra_enabled_store); |
804 | |
805 | static struct attribute *swap_attrs[] = { |
806 | &vma_ra_enabled_attr.attr, |
807 | NULL, |
808 | }; |
809 | |
810 | static struct attribute_group swap_attr_group = { |
811 | .attrs = swap_attrs, |
812 | }; |
813 | |
814 | static int __init swap_init_sysfs(void) |
815 | { |
816 | int err; |
817 | struct kobject *swap_kobj; |
818 | |
819 | swap_kobj = kobject_create_and_add("swap" , mm_kobj); |
820 | if (!swap_kobj) { |
821 | pr_err("failed to create swap kobject\n" ); |
822 | return -ENOMEM; |
823 | } |
824 | err = sysfs_create_group(swap_kobj, &swap_attr_group); |
825 | if (err) { |
826 | pr_err("failed to register swap group\n" ); |
827 | goto delete_obj; |
828 | } |
829 | return 0; |
830 | |
831 | delete_obj: |
832 | kobject_put(swap_kobj); |
833 | return err; |
834 | } |
835 | subsys_initcall(swap_init_sysfs); |
836 | #endif |
837 | |