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b2441318 1// SPDX-License-Identifier: GPL-2.0
1da177e4
LT
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 */
1da177e4 10#include <linux/mm.h>
5a0e3ad6 11#include <linux/gfp.h>
1da177e4
LT
12#include <linux/kernel_stat.h>
13#include <linux/swap.h>
46017e95 14#include <linux/swapops.h>
1da177e4
LT
15#include <linux/init.h>
16#include <linux/pagemap.h>
1da177e4 17#include <linux/backing-dev.h>
3fb5c298 18#include <linux/blkdev.h>
c484d410 19#include <linux/pagevec.h>
b20a3503 20#include <linux/migrate.h>
4b3ef9da 21#include <linux/vmalloc.h>
67afa38e 22#include <linux/swap_slots.h>
38d8b4e6 23#include <linux/huge_mm.h>
1da177e4
LT
24
25#include <asm/pgtable.h>
26
27/*
28 * swapper_space is a fiction, retained to simplify the path through
7eaceacc 29 * vmscan's shrink_page_list.
1da177e4 30 */
f5e54d6e 31static const struct address_space_operations swap_aops = {
1da177e4 32 .writepage = swap_writepage,
62c230bc 33 .set_page_dirty = swap_set_page_dirty,
1c93923c 34#ifdef CONFIG_MIGRATION
e965f963 35 .migratepage = migrate_page,
1c93923c 36#endif
1da177e4
LT
37};
38
783cb68e
CD
39struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
40static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
f5c754d6 41static bool enable_vma_readahead __read_mostly = true;
ec560175 42
ec560175
HY
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)
1da177e4
LT
60
61#define INC_CACHE_INFO(x) do { swap_cache_info.x++; } while (0)
38d8b4e6 62#define ADD_CACHE_INFO(x, nr) do { swap_cache_info.x += (nr); } while (0)
1da177e4
LT
63
64static struct {
65 unsigned long add_total;
66 unsigned long del_total;
67 unsigned long find_success;
68 unsigned long find_total;
1da177e4
LT
69} swap_cache_info;
70
33806f06
SL
71unsigned long total_swapcache_pages(void)
72{
4b3ef9da 73 unsigned int i, j, nr;
33806f06 74 unsigned long ret = 0;
4b3ef9da 75 struct address_space *spaces;
054f1d1f 76 struct swap_info_struct *si;
33806f06 77
4b3ef9da 78 for (i = 0; i < MAX_SWAPFILES; i++) {
054f1d1f
HY
79 swp_entry_t entry = swp_entry(i, 1);
80
81 /* Avoid get_swap_device() to warn for bad swap entry */
82 if (!swp_swap_info(entry))
83 continue;
84 /* Prevent swapoff to free swapper_spaces */
85 si = get_swap_device(entry);
86 if (!si)
4b3ef9da 87 continue;
054f1d1f
HY
88 nr = nr_swapper_spaces[i];
89 spaces = swapper_spaces[i];
4b3ef9da
HY
90 for (j = 0; j < nr; j++)
91 ret += spaces[j].nrpages;
054f1d1f 92 put_swap_device(si);
4b3ef9da 93 }
33806f06
SL
94 return ret;
95}
96
579f8290
SL
97static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
98
1da177e4
LT
99void show_swap_cache_info(void)
100{
33806f06 101 printk("%lu pages in swap cache\n", total_swapcache_pages());
2c97b7fc 102 printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
1da177e4 103 swap_cache_info.add_total, swap_cache_info.del_total,
bb63be0a 104 swap_cache_info.find_success, swap_cache_info.find_total);
ec8acf20
SL
105 printk("Free swap = %ldkB\n",
106 get_nr_swap_pages() << (PAGE_SHIFT - 10));
1da177e4
LT
107 printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
108}
109
110/*
8d93b41c 111 * add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
1da177e4
LT
112 * but sets SwapCache flag and private instead of mapping and index.
113 */
8d93b41c 114int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp)
1da177e4 115{
8d93b41c 116 struct address_space *address_space = swap_address_space(entry);
38d8b4e6 117 pgoff_t idx = swp_offset(entry);
8d93b41c 118 XA_STATE_ORDER(xas, &address_space->i_pages, idx, compound_order(page));
d8c6546b 119 unsigned long i, nr = compound_nr(page);
1da177e4 120
309381fe
SL
121 VM_BUG_ON_PAGE(!PageLocked(page), page);
122 VM_BUG_ON_PAGE(PageSwapCache(page), page);
123 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
51726b12 124
38d8b4e6 125 page_ref_add(page, nr);
31a56396 126 SetPageSwapCache(page);
31a56396 127
8d93b41c
MW
128 do {
129 xas_lock_irq(&xas);
130 xas_create_range(&xas);
131 if (xas_error(&xas))
132 goto unlock;
133 for (i = 0; i < nr; i++) {
134 VM_BUG_ON_PAGE(xas.xa_index != idx + i, page);
135 set_page_private(page + i, entry.val + i);
69bf4b6b 136 xas_store(&xas, page + i);
8d93b41c
MW
137 xas_next(&xas);
138 }
38d8b4e6
HY
139 address_space->nrpages += nr;
140 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
141 ADD_CACHE_INFO(add_total, nr);
8d93b41c
MW
142unlock:
143 xas_unlock_irq(&xas);
144 } while (xas_nomem(&xas, gfp));
31a56396 145
8d93b41c
MW
146 if (!xas_error(&xas))
147 return 0;
31a56396 148
8d93b41c
MW
149 ClearPageSwapCache(page);
150 page_ref_sub(page, nr);
151 return xas_error(&xas);
1da177e4
LT
152}
153
1da177e4
LT
154/*
155 * This must be called only on pages that have
156 * been verified to be in the swap cache.
157 */
4e17ec25 158void __delete_from_swap_cache(struct page *page, swp_entry_t entry)
1da177e4 159{
4e17ec25 160 struct address_space *address_space = swap_address_space(entry);
38d8b4e6 161 int i, nr = hpage_nr_pages(page);
4e17ec25
MW
162 pgoff_t idx = swp_offset(entry);
163 XA_STATE(xas, &address_space->i_pages, idx);
33806f06 164
309381fe
SL
165 VM_BUG_ON_PAGE(!PageLocked(page), page);
166 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
167 VM_BUG_ON_PAGE(PageWriteback(page), page);
1da177e4 168
38d8b4e6 169 for (i = 0; i < nr; i++) {
4e17ec25 170 void *entry = xas_store(&xas, NULL);
69bf4b6b 171 VM_BUG_ON_PAGE(entry != page + i, entry);
38d8b4e6 172 set_page_private(page + i, 0);
4e17ec25 173 xas_next(&xas);
38d8b4e6 174 }
1da177e4 175 ClearPageSwapCache(page);
38d8b4e6
HY
176 address_space->nrpages -= nr;
177 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
178 ADD_CACHE_INFO(del_total, nr);
1da177e4
LT
179}
180
181/**
182 * add_to_swap - allocate swap space for a page
183 * @page: page we want to move to swap
184 *
185 * Allocate swap space for the page and add the page to the
186 * swap cache. Caller needs to hold the page lock.
187 */
0f074658 188int add_to_swap(struct page *page)
1da177e4
LT
189{
190 swp_entry_t entry;
1da177e4
LT
191 int err;
192
309381fe
SL
193 VM_BUG_ON_PAGE(!PageLocked(page), page);
194 VM_BUG_ON_PAGE(!PageUptodate(page), page);
1da177e4 195
38d8b4e6 196 entry = get_swap_page(page);
2ca4532a 197 if (!entry.val)
0f074658
MK
198 return 0;
199
2ca4532a 200 /*
8d93b41c 201 * XArray node allocations from PF_MEMALLOC contexts could
2ca4532a
DN
202 * completely exhaust the page allocator. __GFP_NOMEMALLOC
203 * stops emergency reserves from being allocated.
204 *
205 * TODO: this could cause a theoretical memory reclaim
206 * deadlock in the swap out path.
207 */
208 /*
854e9ed0 209 * Add it to the swap cache.
2ca4532a
DN
210 */
211 err = add_to_swap_cache(page, entry,
212 __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
38d8b4e6 213 if (err)
bd53b714 214 /*
2ca4532a
DN
215 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
216 * clear SWAP_HAS_CACHE flag.
1da177e4 217 */
0f074658 218 goto fail;
9625456c
SL
219 /*
220 * Normally the page will be dirtied in unmap because its pte should be
221 * dirty. A special case is MADV_FREE page. The page'e pte could have
222 * dirty bit cleared but the page's SwapBacked bit is still set because
223 * clearing the dirty bit and SwapBacked bit has no lock protected. For
224 * such page, unmap will not set dirty bit for it, so page reclaim will
225 * not write the page out. This can cause data corruption when the page
226 * is swap in later. Always setting the dirty bit for the page solves
227 * the problem.
228 */
229 set_page_dirty(page);
38d8b4e6
HY
230
231 return 1;
232
38d8b4e6 233fail:
0f074658 234 put_swap_page(page, entry);
38d8b4e6 235 return 0;
1da177e4
LT
236}
237
238/*
239 * This must be called only on pages that have
240 * been verified to be in the swap cache and locked.
241 * It will never put the page into the free list,
242 * the caller has a reference on the page.
243 */
244void delete_from_swap_cache(struct page *page)
245{
4e17ec25
MW
246 swp_entry_t entry = { .val = page_private(page) };
247 struct address_space *address_space = swap_address_space(entry);
1da177e4 248
b93b0163 249 xa_lock_irq(&address_space->i_pages);
4e17ec25 250 __delete_from_swap_cache(page, entry);
b93b0163 251 xa_unlock_irq(&address_space->i_pages);
1da177e4 252
75f6d6d2 253 put_swap_page(page, entry);
38d8b4e6 254 page_ref_sub(page, hpage_nr_pages(page));
1da177e4
LT
255}
256
1da177e4
LT
257/*
258 * If we are the only user, then try to free up the swap cache.
259 *
260 * Its ok to check for PageSwapCache without the page lock
a2c43eed
HD
261 * here because we are going to recheck again inside
262 * try_to_free_swap() _with_ the lock.
1da177e4
LT
263 * - Marcelo
264 */
265static inline void free_swap_cache(struct page *page)
266{
a2c43eed
HD
267 if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
268 try_to_free_swap(page);
1da177e4
LT
269 unlock_page(page);
270 }
271}
272
273/*
274 * Perform a free_page(), also freeing any swap cache associated with
b8072f09 275 * this page if it is the last user of the page.
1da177e4
LT
276 */
277void free_page_and_swap_cache(struct page *page)
278{
279 free_swap_cache(page);
6fcb52a5 280 if (!is_huge_zero_page(page))
770a5370 281 put_page(page);
1da177e4
LT
282}
283
284/*
285 * Passed an array of pages, drop them all from swapcache and then release
286 * them. They are removed from the LRU and freed if this is their last use.
287 */
288void free_pages_and_swap_cache(struct page **pages, int nr)
289{
1da177e4 290 struct page **pagep = pages;
aabfb572 291 int i;
1da177e4
LT
292
293 lru_add_drain();
aabfb572
MH
294 for (i = 0; i < nr; i++)
295 free_swap_cache(pagep[i]);
c6f92f9f 296 release_pages(pagep, nr);
1da177e4
LT
297}
298
e9e9b7ec
MK
299static inline bool swap_use_vma_readahead(void)
300{
301 return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap);
302}
303
1da177e4
LT
304/*
305 * Lookup a swap entry in the swap cache. A found page will be returned
306 * unlocked and with its refcount incremented - we rely on the kernel
307 * lock getting page table operations atomic even if we drop the page
308 * lock before returning.
309 */
ec560175
HY
310struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
311 unsigned long addr)
1da177e4
LT
312{
313 struct page *page;
eb085574 314 struct swap_info_struct *si;
1da177e4 315
eb085574
HY
316 si = get_swap_device(entry);
317 if (!si)
318 return NULL;
f6ab1f7f 319 page = find_get_page(swap_address_space(entry), swp_offset(entry));
eb085574 320 put_swap_device(si);
1da177e4 321
ec560175
HY
322 INC_CACHE_INFO(find_total);
323 if (page) {
eaf649eb
MK
324 bool vma_ra = swap_use_vma_readahead();
325 bool readahead;
326
1da177e4 327 INC_CACHE_INFO(find_success);
eaf649eb
MK
328 /*
329 * At the moment, we don't support PG_readahead for anon THP
330 * so let's bail out rather than confusing the readahead stat.
331 */
ec560175
HY
332 if (unlikely(PageTransCompound(page)))
333 return page;
eaf649eb 334
ec560175 335 readahead = TestClearPageReadahead(page);
eaf649eb
MK
336 if (vma && vma_ra) {
337 unsigned long ra_val;
338 int win, hits;
339
340 ra_val = GET_SWAP_RA_VAL(vma);
341 win = SWAP_RA_WIN(ra_val);
342 hits = SWAP_RA_HITS(ra_val);
ec560175
HY
343 if (readahead)
344 hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
345 atomic_long_set(&vma->swap_readahead_info,
346 SWAP_RA_VAL(addr, win, hits));
347 }
eaf649eb 348
ec560175 349 if (readahead) {
cbc65df2 350 count_vm_event(SWAP_RA_HIT);
eaf649eb 351 if (!vma || !vma_ra)
ec560175 352 atomic_inc(&swapin_readahead_hits);
cbc65df2 353 }
579f8290 354 }
eaf649eb 355
1da177e4
LT
356 return page;
357}
358
5b999aad
DS
359struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
360 struct vm_area_struct *vma, unsigned long addr,
361 bool *new_page_allocated)
1da177e4 362{
eb085574
HY
363 struct page *found_page = NULL, *new_page = NULL;
364 struct swap_info_struct *si;
1da177e4 365 int err;
5b999aad 366 *new_page_allocated = false;
1da177e4
LT
367
368 do {
369 /*
370 * First check the swap cache. Since this is normally
371 * called after lookup_swap_cache() failed, re-calling
372 * that would confuse statistics.
373 */
eb085574
HY
374 si = get_swap_device(entry);
375 if (!si)
376 break;
377 found_page = find_get_page(swap_address_space(entry),
378 swp_offset(entry));
379 put_swap_device(si);
1da177e4
LT
380 if (found_page)
381 break;
382
ba81f838
HY
383 /*
384 * Just skip read ahead for unused swap slot.
385 * During swap_off when swap_slot_cache is disabled,
386 * we have to handle the race between putting
387 * swap entry in swap cache and marking swap slot
388 * as SWAP_HAS_CACHE. That's done in later part of code or
389 * else swap_off will be aborted if we return NULL.
390 */
391 if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
392 break;
e8c26ab6 393
1da177e4
LT
394 /*
395 * Get a new page to read into from swap.
396 */
397 if (!new_page) {
02098fea 398 new_page = alloc_page_vma(gfp_mask, vma, addr);
1da177e4
LT
399 if (!new_page)
400 break; /* Out of memory */
401 }
402
f000944d
HD
403 /*
404 * Swap entry may have been freed since our caller observed it.
405 */
355cfa73 406 err = swapcache_prepare(entry);
cbab0e4e 407 if (err == -EEXIST) {
cbab0e4e
RA
408 /*
409 * We might race against get_swap_page() and stumble
410 * across a SWAP_HAS_CACHE swap_map entry whose page
9c1cc2e4 411 * has not been brought into the swapcache yet.
cbab0e4e
RA
412 */
413 cond_resched();
355cfa73 414 continue;
8d93b41c 415 } else if (err) /* swp entry is obsolete ? */
f000944d
HD
416 break;
417
8d93b41c 418 /* May fail (-ENOMEM) if XArray node allocation failed. */
48c935ad 419 __SetPageLocked(new_page);
fa9949da 420 __SetPageSwapBacked(new_page);
8d93b41c 421 err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
529ae9aa 422 if (likely(!err)) {
8d93b41c 423 /* Initiate read into locked page */
1899ad18 424 SetPageWorkingset(new_page);
c5fdae46 425 lru_cache_add_anon(new_page);
5b999aad 426 *new_page_allocated = true;
1da177e4
LT
427 return new_page;
428 }
48c935ad 429 __ClearPageLocked(new_page);
2ca4532a
DN
430 /*
431 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
432 * clear SWAP_HAS_CACHE flag.
433 */
75f6d6d2 434 put_swap_page(new_page, entry);
f000944d 435 } while (err != -ENOMEM);
1da177e4
LT
436
437 if (new_page)
09cbfeaf 438 put_page(new_page);
1da177e4
LT
439 return found_page;
440}
46017e95 441
5b999aad
DS
442/*
443 * Locate a page of swap in physical memory, reserving swap cache space
444 * and reading the disk if it is not already cached.
445 * A failure return means that either the page allocation failed or that
446 * the swap entry is no longer in use.
447 */
448struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
23955622 449 struct vm_area_struct *vma, unsigned long addr, bool do_poll)
5b999aad
DS
450{
451 bool page_was_allocated;
452 struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
453 vma, addr, &page_was_allocated);
454
455 if (page_was_allocated)
23955622 456 swap_readpage(retpage, do_poll);
5b999aad
DS
457
458 return retpage;
459}
460
ec560175
HY
461static unsigned int __swapin_nr_pages(unsigned long prev_offset,
462 unsigned long offset,
463 int hits,
464 int max_pages,
465 int prev_win)
579f8290 466{
ec560175 467 unsigned int pages, last_ra;
579f8290
SL
468
469 /*
470 * This heuristic has been found to work well on both sequential and
471 * random loads, swapping to hard disk or to SSD: please don't ask
472 * what the "+ 2" means, it just happens to work well, that's all.
473 */
ec560175 474 pages = hits + 2;
579f8290
SL
475 if (pages == 2) {
476 /*
477 * We can have no readahead hits to judge by: but must not get
478 * stuck here forever, so check for an adjacent offset instead
479 * (and don't even bother to check whether swap type is same).
480 */
481 if (offset != prev_offset + 1 && offset != prev_offset - 1)
482 pages = 1;
579f8290
SL
483 } else {
484 unsigned int roundup = 4;
485 while (roundup < pages)
486 roundup <<= 1;
487 pages = roundup;
488 }
489
490 if (pages > max_pages)
491 pages = max_pages;
492
493 /* Don't shrink readahead too fast */
ec560175 494 last_ra = prev_win / 2;
579f8290
SL
495 if (pages < last_ra)
496 pages = last_ra;
ec560175
HY
497
498 return pages;
499}
500
501static unsigned long swapin_nr_pages(unsigned long offset)
502{
503 static unsigned long prev_offset;
504 unsigned int hits, pages, max_pages;
505 static atomic_t last_readahead_pages;
506
507 max_pages = 1 << READ_ONCE(page_cluster);
508 if (max_pages <= 1)
509 return 1;
510
511 hits = atomic_xchg(&swapin_readahead_hits, 0);
512 pages = __swapin_nr_pages(prev_offset, offset, hits, max_pages,
513 atomic_read(&last_readahead_pages));
514 if (!hits)
515 prev_offset = offset;
579f8290
SL
516 atomic_set(&last_readahead_pages, pages);
517
518 return pages;
519}
520
46017e95 521/**
e9e9b7ec 522 * swap_cluster_readahead - swap in pages in hope we need them soon
46017e95 523 * @entry: swap entry of this memory
7682486b 524 * @gfp_mask: memory allocation flags
e9e9b7ec 525 * @vmf: fault information
46017e95
HD
526 *
527 * Returns the struct page for entry and addr, after queueing swapin.
528 *
529 * Primitive swap readahead code. We simply read an aligned block of
530 * (1 << page_cluster) entries in the swap area. This method is chosen
531 * because it doesn't cost us any seek time. We also make sure to queue
532 * the 'original' request together with the readahead ones...
533 *
534 * This has been extended to use the NUMA policies from the mm triggering
535 * the readahead.
536 *
e9f59873 537 * Caller must hold read mmap_sem if vmf->vma is not NULL.
46017e95 538 */
e9e9b7ec
MK
539struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
540 struct vm_fault *vmf)
46017e95 541{
46017e95 542 struct page *page;
579f8290
SL
543 unsigned long entry_offset = swp_offset(entry);
544 unsigned long offset = entry_offset;
67f96aa2 545 unsigned long start_offset, end_offset;
579f8290 546 unsigned long mask;
e9a6effa 547 struct swap_info_struct *si = swp_swap_info(entry);
3fb5c298 548 struct blk_plug plug;
c4fa6309 549 bool do_poll = true, page_allocated;
e9e9b7ec
MK
550 struct vm_area_struct *vma = vmf->vma;
551 unsigned long addr = vmf->address;
46017e95 552
579f8290
SL
553 mask = swapin_nr_pages(offset) - 1;
554 if (!mask)
555 goto skip;
556
8fd2e0b5
YS
557 /* Test swap type to make sure the dereference is safe */
558 if (likely(si->flags & (SWP_BLKDEV | SWP_FS))) {
559 struct inode *inode = si->swap_file->f_mapping->host;
560 if (inode_read_congested(inode))
561 goto skip;
562 }
563
23955622 564 do_poll = false;
67f96aa2
RR
565 /* Read a page_cluster sized and aligned cluster around offset. */
566 start_offset = offset & ~mask;
567 end_offset = offset | mask;
568 if (!start_offset) /* First page is swap header. */
569 start_offset++;
e9a6effa
HY
570 if (end_offset >= si->max)
571 end_offset = si->max - 1;
67f96aa2 572
3fb5c298 573 blk_start_plug(&plug);
67f96aa2 574 for (offset = start_offset; offset <= end_offset ; offset++) {
46017e95 575 /* Ok, do the async read-ahead now */
c4fa6309
HY
576 page = __read_swap_cache_async(
577 swp_entry(swp_type(entry), offset),
578 gfp_mask, vma, addr, &page_allocated);
46017e95 579 if (!page)
67f96aa2 580 continue;
c4fa6309
HY
581 if (page_allocated) {
582 swap_readpage(page, false);
eaf649eb 583 if (offset != entry_offset) {
c4fa6309
HY
584 SetPageReadahead(page);
585 count_vm_event(SWAP_RA);
586 }
cbc65df2 587 }
09cbfeaf 588 put_page(page);
46017e95 589 }
3fb5c298
CE
590 blk_finish_plug(&plug);
591
46017e95 592 lru_add_drain(); /* Push any new pages onto the LRU now */
579f8290 593skip:
23955622 594 return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll);
46017e95 595}
4b3ef9da
HY
596
597int init_swap_address_space(unsigned int type, unsigned long nr_pages)
598{
599 struct address_space *spaces, *space;
600 unsigned int i, nr;
601
602 nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
778e1cdd 603 spaces = kvcalloc(nr, sizeof(struct address_space), GFP_KERNEL);
4b3ef9da
HY
604 if (!spaces)
605 return -ENOMEM;
606 for (i = 0; i < nr; i++) {
607 space = spaces + i;
a2833486 608 xa_init_flags(&space->i_pages, XA_FLAGS_LOCK_IRQ);
4b3ef9da
HY
609 atomic_set(&space->i_mmap_writable, 0);
610 space->a_ops = &swap_aops;
611 /* swap cache doesn't use writeback related tags */
612 mapping_set_no_writeback_tags(space);
4b3ef9da
HY
613 }
614 nr_swapper_spaces[type] = nr;
054f1d1f 615 swapper_spaces[type] = spaces;
4b3ef9da
HY
616
617 return 0;
618}
619
620void exit_swap_address_space(unsigned int type)
621{
054f1d1f 622 kvfree(swapper_spaces[type]);
4b3ef9da 623 nr_swapper_spaces[type] = 0;
054f1d1f 624 swapper_spaces[type] = NULL;
4b3ef9da 625}
ec560175
HY
626
627static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,
628 unsigned long faddr,
629 unsigned long lpfn,
630 unsigned long rpfn,
631 unsigned long *start,
632 unsigned long *end)
633{
634 *start = max3(lpfn, PFN_DOWN(vma->vm_start),
635 PFN_DOWN(faddr & PMD_MASK));
636 *end = min3(rpfn, PFN_DOWN(vma->vm_end),
637 PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
638}
639
eaf649eb
MK
640static void swap_ra_info(struct vm_fault *vmf,
641 struct vma_swap_readahead *ra_info)
ec560175
HY
642{
643 struct vm_area_struct *vma = vmf->vma;
eaf649eb 644 unsigned long ra_val;
ec560175
HY
645 swp_entry_t entry;
646 unsigned long faddr, pfn, fpfn;
647 unsigned long start, end;
eaf649eb 648 pte_t *pte, *orig_pte;
ec560175
HY
649 unsigned int max_win, hits, prev_win, win, left;
650#ifndef CONFIG_64BIT
651 pte_t *tpte;
652#endif
653
61b63972
HY
654 max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
655 SWAP_RA_ORDER_CEILING);
656 if (max_win == 1) {
eaf649eb
MK
657 ra_info->win = 1;
658 return;
61b63972
HY
659 }
660
ec560175 661 faddr = vmf->address;
eaf649eb
MK
662 orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
663 entry = pte_to_swp_entry(*pte);
664 if ((unlikely(non_swap_entry(entry)))) {
665 pte_unmap(orig_pte);
666 return;
667 }
ec560175 668
ec560175 669 fpfn = PFN_DOWN(faddr);
eaf649eb
MK
670 ra_val = GET_SWAP_RA_VAL(vma);
671 pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
672 prev_win = SWAP_RA_WIN(ra_val);
673 hits = SWAP_RA_HITS(ra_val);
674 ra_info->win = win = __swapin_nr_pages(pfn, fpfn, hits,
ec560175
HY
675 max_win, prev_win);
676 atomic_long_set(&vma->swap_readahead_info,
677 SWAP_RA_VAL(faddr, win, 0));
678
eaf649eb
MK
679 if (win == 1) {
680 pte_unmap(orig_pte);
681 return;
682 }
ec560175
HY
683
684 /* Copy the PTEs because the page table may be unmapped */
685 if (fpfn == pfn + 1)
686 swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
687 else if (pfn == fpfn + 1)
688 swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1,
689 &start, &end);
690 else {
691 left = (win - 1) / 2;
692 swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left,
693 &start, &end);
694 }
eaf649eb
MK
695 ra_info->nr_pte = end - start;
696 ra_info->offset = fpfn - start;
697 pte -= ra_info->offset;
ec560175 698#ifdef CONFIG_64BIT
eaf649eb 699 ra_info->ptes = pte;
ec560175 700#else
eaf649eb 701 tpte = ra_info->ptes;
ec560175
HY
702 for (pfn = start; pfn != end; pfn++)
703 *tpte++ = *pte++;
704#endif
eaf649eb 705 pte_unmap(orig_pte);
ec560175
HY
706}
707
e9f59873
YS
708/**
709 * swap_vma_readahead - swap in pages in hope we need them soon
710 * @entry: swap entry of this memory
711 * @gfp_mask: memory allocation flags
712 * @vmf: fault information
713 *
714 * Returns the struct page for entry and addr, after queueing swapin.
715 *
716 * Primitive swap readahead code. We simply read in a few pages whoes
717 * virtual addresses are around the fault address in the same vma.
718 *
719 * Caller must hold read mmap_sem if vmf->vma is not NULL.
720 *
721 */
f5c754d6
CIK
722static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
723 struct vm_fault *vmf)
ec560175
HY
724{
725 struct blk_plug plug;
726 struct vm_area_struct *vma = vmf->vma;
727 struct page *page;
728 pte_t *pte, pentry;
729 swp_entry_t entry;
730 unsigned int i;
731 bool page_allocated;
eaf649eb 732 struct vma_swap_readahead ra_info = {0,};
ec560175 733
eaf649eb
MK
734 swap_ra_info(vmf, &ra_info);
735 if (ra_info.win == 1)
ec560175
HY
736 goto skip;
737
738 blk_start_plug(&plug);
eaf649eb 739 for (i = 0, pte = ra_info.ptes; i < ra_info.nr_pte;
ec560175
HY
740 i++, pte++) {
741 pentry = *pte;
742 if (pte_none(pentry))
743 continue;
744 if (pte_present(pentry))
745 continue;
746 entry = pte_to_swp_entry(pentry);
747 if (unlikely(non_swap_entry(entry)))
748 continue;
749 page = __read_swap_cache_async(entry, gfp_mask, vma,
750 vmf->address, &page_allocated);
751 if (!page)
752 continue;
753 if (page_allocated) {
754 swap_readpage(page, false);
eaf649eb 755 if (i != ra_info.offset) {
ec560175
HY
756 SetPageReadahead(page);
757 count_vm_event(SWAP_RA);
758 }
759 }
760 put_page(page);
761 }
762 blk_finish_plug(&plug);
763 lru_add_drain();
764skip:
765 return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
eaf649eb 766 ra_info.win == 1);
ec560175 767}
d9bfcfdc 768
e9e9b7ec
MK
769/**
770 * swapin_readahead - swap in pages in hope we need them soon
771 * @entry: swap entry of this memory
772 * @gfp_mask: memory allocation flags
773 * @vmf: fault information
774 *
775 * Returns the struct page for entry and addr, after queueing swapin.
776 *
777 * It's a main entry function for swap readahead. By the configuration,
778 * it will read ahead blocks by cluster-based(ie, physical disk based)
779 * or vma-based(ie, virtual address based on faulty address) readahead.
780 */
781struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
782 struct vm_fault *vmf)
783{
784 return swap_use_vma_readahead() ?
785 swap_vma_readahead(entry, gfp_mask, vmf) :
786 swap_cluster_readahead(entry, gfp_mask, vmf);
787}
788
d9bfcfdc
HY
789#ifdef CONFIG_SYSFS
790static ssize_t vma_ra_enabled_show(struct kobject *kobj,
791 struct kobj_attribute *attr, char *buf)
792{
e9e9b7ec 793 return sprintf(buf, "%s\n", enable_vma_readahead ? "true" : "false");
d9bfcfdc
HY
794}
795static ssize_t vma_ra_enabled_store(struct kobject *kobj,
796 struct kobj_attribute *attr,
797 const char *buf, size_t count)
798{
799 if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
e9e9b7ec 800 enable_vma_readahead = true;
d9bfcfdc 801 else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
e9e9b7ec 802 enable_vma_readahead = false;
d9bfcfdc
HY
803 else
804 return -EINVAL;
805
806 return count;
807}
808static struct kobj_attribute vma_ra_enabled_attr =
809 __ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
810 vma_ra_enabled_store);
811
d9bfcfdc
HY
812static struct attribute *swap_attrs[] = {
813 &vma_ra_enabled_attr.attr,
d9bfcfdc
HY
814 NULL,
815};
816
817static struct attribute_group swap_attr_group = {
818 .attrs = swap_attrs,
819};
820
821static int __init swap_init_sysfs(void)
822{
823 int err;
824 struct kobject *swap_kobj;
825
826 swap_kobj = kobject_create_and_add("swap", mm_kobj);
827 if (!swap_kobj) {
828 pr_err("failed to create swap kobject\n");
829 return -ENOMEM;
830 }
831 err = sysfs_create_group(swap_kobj, &swap_attr_group);
832 if (err) {
833 pr_err("failed to register swap group\n");
834 goto delete_obj;
835 }
836 return 0;
837
838delete_obj:
839 kobject_put(swap_kobj);
840 return err;
841}
842subsys_initcall(swap_init_sysfs);
843#endif