1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/mm/page_io.c
4 *
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
6 *
7 * Swap reorganised 29.12.95,
8 * Asynchronous swapping added 30.12.95. Stephen Tweedie
9 * Removed race in async swapping. 14.4.1996. Bruno Haible
10 * Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
11 * Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman
12 */
13
14#include <linux/mm.h>
15#include <linux/kernel_stat.h>
16#include <linux/gfp.h>
17#include <linux/pagemap.h>
18#include <linux/swap.h>
19#include <linux/bio.h>
20#include <linux/swapops.h>
21#include <linux/writeback.h>
22#include <linux/blkdev.h>
23#include <linux/psi.h>
24#include <linux/uio.h>
25#include <linux/sched/task.h>
26#include <linux/delayacct.h>
27#include <linux/zswap.h>
28#include "swap.h"
29
30static void __end_swap_bio_write(struct bio *bio)
31{
32 struct folio *folio = bio_first_folio_all(bio);
33
34 if (bio->bi_status) {
35 /*
36 * We failed to write the page out to swap-space.
37 * Re-dirty the page in order to avoid it being reclaimed.
38 * Also print a dire warning that things will go BAD (tm)
39 * very quickly.
40 *
41 * Also clear PG_reclaim to avoid folio_rotate_reclaimable()
42 */
43 folio_mark_dirty(folio);
44 pr_alert_ratelimited("Write-error on swap-device (%u:%u:%llu)\n",
45 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
46 (unsigned long long)bio->bi_iter.bi_sector);
47 folio_clear_reclaim(folio);
48 }
49 folio_end_writeback(folio);
50}
51
52static void end_swap_bio_write(struct bio *bio)
53{
54 __end_swap_bio_write(bio);
55 bio_put(bio);
56}
57
58static void __end_swap_bio_read(struct bio *bio)
59{
60 struct folio *folio = bio_first_folio_all(bio);
61
62 if (bio->bi_status) {
63 pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n",
64 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
65 (unsigned long long)bio->bi_iter.bi_sector);
66 } else {
67 folio_mark_uptodate(folio);
68 }
69 folio_unlock(folio);
70}
71
72static void end_swap_bio_read(struct bio *bio)
73{
74 __end_swap_bio_read(bio);
75 bio_put(bio);
76}
77
78int generic_swapfile_activate(struct swap_info_struct *sis,
79 struct file *swap_file,
80 sector_t *span)
81{
82 struct address_space *mapping = swap_file->f_mapping;
83 struct inode *inode = mapping->host;
84 unsigned blocks_per_page;
85 unsigned long page_no;
86 unsigned blkbits;
87 sector_t probe_block;
88 sector_t last_block;
89 sector_t lowest_block = -1;
90 sector_t highest_block = 0;
91 int nr_extents = 0;
92 int ret;
93
94 blkbits = inode->i_blkbits;
95 blocks_per_page = PAGE_SIZE >> blkbits;
96
97 /*
98 * Map all the blocks into the extent tree. This code doesn't try
99 * to be very smart.
100 */
101 probe_block = 0;
102 page_no = 0;
103 last_block = i_size_read(inode) >> blkbits;
104 while ((probe_block + blocks_per_page) <= last_block &&
105 page_no < sis->max) {
106 unsigned block_in_page;
107 sector_t first_block;
108
109 cond_resched();
110
111 first_block = probe_block;
112 ret = bmap(inode, block: &first_block);
113 if (ret || !first_block)
114 goto bad_bmap;
115
116 /*
117 * It must be PAGE_SIZE aligned on-disk
118 */
119 if (first_block & (blocks_per_page - 1)) {
120 probe_block++;
121 goto reprobe;
122 }
123
124 for (block_in_page = 1; block_in_page < blocks_per_page;
125 block_in_page++) {
126 sector_t block;
127
128 block = probe_block + block_in_page;
129 ret = bmap(inode, block: &block);
130 if (ret || !block)
131 goto bad_bmap;
132
133 if (block != first_block + block_in_page) {
134 /* Discontiguity */
135 probe_block++;
136 goto reprobe;
137 }
138 }
139
140 first_block >>= (PAGE_SHIFT - blkbits);
141 if (page_no) { /* exclude the header page */
142 if (first_block < lowest_block)
143 lowest_block = first_block;
144 if (first_block > highest_block)
145 highest_block = first_block;
146 }
147
148 /*
149 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
150 */
151 ret = add_swap_extent(sis, start_page: page_no, nr_pages: 1, start_block: first_block);
152 if (ret < 0)
153 goto out;
154 nr_extents += ret;
155 page_no++;
156 probe_block += blocks_per_page;
157reprobe:
158 continue;
159 }
160 ret = nr_extents;
161 *span = 1 + highest_block - lowest_block;
162 if (page_no == 0)
163 page_no = 1; /* force Empty message */
164 sis->max = page_no;
165 sis->pages = page_no - 1;
166out:
167 return ret;
168bad_bmap:
169 pr_err("swapon: swapfile has holes\n");
170 ret = -EINVAL;
171 goto out;
172}
173
174static bool is_folio_zero_filled(struct folio *folio)
175{
176 unsigned int pos, last_pos;
177 unsigned long *data;
178 unsigned int i;
179
180 last_pos = PAGE_SIZE / sizeof(*data) - 1;
181 for (i = 0; i < folio_nr_pages(folio); i++) {
182 data = kmap_local_folio(folio, offset: i * PAGE_SIZE);
183 /*
184 * Check last word first, incase the page is zero-filled at
185 * the start and has non-zero data at the end, which is common
186 * in real-world workloads.
187 */
188 if (data[last_pos]) {
189 kunmap_local(data);
190 return false;
191 }
192 for (pos = 0; pos < last_pos; pos++) {
193 if (data[pos]) {
194 kunmap_local(data);
195 return false;
196 }
197 }
198 kunmap_local(data);
199 }
200
201 return true;
202}
203
204static void swap_zeromap_folio_set(struct folio *folio)
205{
206 struct obj_cgroup *objcg = get_obj_cgroup_from_folio(folio);
207 struct swap_info_struct *sis = __swap_entry_to_info(entry: folio->swap);
208 int nr_pages = folio_nr_pages(folio);
209 swp_entry_t entry;
210 unsigned int i;
211
212 for (i = 0; i < folio_nr_pages(folio); i++) {
213 entry = page_swap_entry(folio_page(folio, i));
214 set_bit(nr: swp_offset(entry), addr: sis->zeromap);
215 }
216
217 count_vm_events(item: SWPOUT_ZERO, delta: nr_pages);
218 if (objcg) {
219 count_objcg_events(objcg, idx: SWPOUT_ZERO, count: nr_pages);
220 obj_cgroup_put(objcg);
221 }
222}
223
224static void swap_zeromap_folio_clear(struct folio *folio)
225{
226 struct swap_info_struct *sis = __swap_entry_to_info(entry: folio->swap);
227 swp_entry_t entry;
228 unsigned int i;
229
230 for (i = 0; i < folio_nr_pages(folio); i++) {
231 entry = page_swap_entry(folio_page(folio, i));
232 clear_bit(nr: swp_offset(entry), addr: sis->zeromap);
233 }
234}
235
236/*
237 * We may have stale swap cache pages in memory: notice
238 * them here and get rid of the unnecessary final write.
239 */
240int swap_writeout(struct folio *folio, struct swap_iocb **swap_plug)
241{
242 int ret = 0;
243
244 if (folio_free_swap(folio))
245 goto out_unlock;
246
247 /*
248 * Arch code may have to preserve more data than just the page
249 * contents, e.g. memory tags.
250 */
251 ret = arch_prepare_to_swap(folio);
252 if (ret) {
253 folio_mark_dirty(folio);
254 goto out_unlock;
255 }
256
257 /*
258 * Use a bitmap (zeromap) to avoid doing IO for zero-filled pages.
259 * The bits in zeromap are protected by the locked swapcache folio
260 * and atomic updates are used to protect against read-modify-write
261 * corruption due to other zero swap entries seeing concurrent updates.
262 */
263 if (is_folio_zero_filled(folio)) {
264 swap_zeromap_folio_set(folio);
265 goto out_unlock;
266 }
267
268 /*
269 * Clear bits this folio occupies in the zeromap to prevent zero data
270 * being read in from any previous zero writes that occupied the same
271 * swap entries.
272 */
273 swap_zeromap_folio_clear(folio);
274
275 if (zswap_store(folio)) {
276 count_mthp_stat(order: folio_order(folio), item: MTHP_STAT_ZSWPOUT);
277 goto out_unlock;
278 }
279 if (!mem_cgroup_zswap_writeback_enabled(memcg: folio_memcg(folio))) {
280 folio_mark_dirty(folio);
281 return AOP_WRITEPAGE_ACTIVATE;
282 }
283
284 __swap_writepage(folio, swap_plug);
285 return 0;
286out_unlock:
287 folio_unlock(folio);
288 return ret;
289}
290
291static inline void count_swpout_vm_event(struct folio *folio)
292{
293#ifdef CONFIG_TRANSPARENT_HUGEPAGE
294 if (unlikely(folio_test_pmd_mappable(folio))) {
295 count_memcg_folio_events(folio, THP_SWPOUT, 1);
296 count_vm_event(THP_SWPOUT);
297 }
298#endif
299 count_mthp_stat(order: folio_order(folio), item: MTHP_STAT_SWPOUT);
300 count_memcg_folio_events(folio, idx: PSWPOUT, nr: folio_nr_pages(folio));
301 count_vm_events(item: PSWPOUT, delta: folio_nr_pages(folio));
302}
303
304#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
305static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)
306{
307 struct cgroup_subsys_state *css;
308 struct mem_cgroup *memcg;
309
310 memcg = folio_memcg(folio);
311 if (!memcg)
312 return;
313
314 rcu_read_lock();
315 css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
316 bio_associate_blkg_from_css(bio, css);
317 rcu_read_unlock();
318}
319#else
320#define bio_associate_blkg_from_page(bio, folio) do { } while (0)
321#endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
322
323struct swap_iocb {
324 struct kiocb iocb;
325 struct bio_vec bvec[SWAP_CLUSTER_MAX];
326 int pages;
327 int len;
328};
329static mempool_t *sio_pool;
330
331int sio_pool_init(void)
332{
333 if (!sio_pool) {
334 mempool_t *pool = mempool_create_kmalloc_pool(
335 SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
336 if (cmpxchg(&sio_pool, NULL, pool))
337 mempool_destroy(pool);
338 }
339 if (!sio_pool)
340 return -ENOMEM;
341 return 0;
342}
343
344static void sio_write_complete(struct kiocb *iocb, long ret)
345{
346 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
347 struct page *page = sio->bvec[0].bv_page;
348 int p;
349
350 if (ret != sio->len) {
351 /*
352 * In the case of swap-over-nfs, this can be a
353 * temporary failure if the system has limited
354 * memory for allocating transmit buffers.
355 * Mark the page dirty and avoid
356 * folio_rotate_reclaimable but rate-limit the
357 * messages.
358 */
359 pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
360 ret, swap_dev_pos(page_swap_entry(page)));
361 for (p = 0; p < sio->pages; p++) {
362 page = sio->bvec[p].bv_page;
363 set_page_dirty(page);
364 ClearPageReclaim(page);
365 }
366 }
367
368 for (p = 0; p < sio->pages; p++)
369 end_page_writeback(page: sio->bvec[p].bv_page);
370
371 mempool_free(element: sio, pool: sio_pool);
372}
373
374static void swap_writepage_fs(struct folio *folio, struct swap_iocb **swap_plug)
375{
376 struct swap_iocb *sio = swap_plug ? *swap_plug : NULL;
377 struct swap_info_struct *sis = __swap_entry_to_info(entry: folio->swap);
378 struct file *swap_file = sis->swap_file;
379 loff_t pos = swap_dev_pos(entry: folio->swap);
380
381 count_swpout_vm_event(folio);
382 folio_start_writeback(folio);
383 folio_unlock(folio);
384 if (sio) {
385 if (sio->iocb.ki_filp != swap_file ||
386 sio->iocb.ki_pos + sio->len != pos) {
387 swap_write_unplug(sio);
388 sio = NULL;
389 }
390 }
391 if (!sio) {
392 sio = mempool_alloc(sio_pool, GFP_NOIO);
393 init_sync_kiocb(kiocb: &sio->iocb, filp: swap_file);
394 sio->iocb.ki_complete = sio_write_complete;
395 sio->iocb.ki_pos = pos;
396 sio->pages = 0;
397 sio->len = 0;
398 }
399 bvec_set_folio(bv: &sio->bvec[sio->pages], folio, len: folio_size(folio), offset: 0);
400 sio->len += folio_size(folio);
401 sio->pages += 1;
402 if (sio->pages == ARRAY_SIZE(sio->bvec) || !swap_plug) {
403 swap_write_unplug(sio);
404 sio = NULL;
405 }
406 if (swap_plug)
407 *swap_plug = sio;
408}
409
410static void swap_writepage_bdev_sync(struct folio *folio,
411 struct swap_info_struct *sis)
412{
413 struct bio_vec bv;
414 struct bio bio;
415
416 bio_init(bio: &bio, bdev: sis->bdev, table: &bv, max_vecs: 1, opf: REQ_OP_WRITE | REQ_SWAP);
417 bio.bi_iter.bi_sector = swap_folio_sector(folio);
418 bio_add_folio_nofail(bio: &bio, folio, len: folio_size(folio), off: 0);
419
420 bio_associate_blkg_from_page(&bio, folio);
421 count_swpout_vm_event(folio);
422
423 folio_start_writeback(folio);
424 folio_unlock(folio);
425
426 submit_bio_wait(bio: &bio);
427 __end_swap_bio_write(bio: &bio);
428}
429
430static void swap_writepage_bdev_async(struct folio *folio,
431 struct swap_info_struct *sis)
432{
433 struct bio *bio;
434
435 bio = bio_alloc(bdev: sis->bdev, nr_vecs: 1, opf: REQ_OP_WRITE | REQ_SWAP, GFP_NOIO);
436 bio->bi_iter.bi_sector = swap_folio_sector(folio);
437 bio->bi_end_io = end_swap_bio_write;
438 bio_add_folio_nofail(bio, folio, len: folio_size(folio), off: 0);
439
440 bio_associate_blkg_from_page(bio, folio);
441 count_swpout_vm_event(folio);
442 folio_start_writeback(folio);
443 folio_unlock(folio);
444 submit_bio(bio);
445}
446
447void __swap_writepage(struct folio *folio, struct swap_iocb **swap_plug)
448{
449 struct swap_info_struct *sis = __swap_entry_to_info(entry: folio->swap);
450
451 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
452 /*
453 * ->flags can be updated non-atomicially (scan_swap_map_slots),
454 * but that will never affect SWP_FS_OPS, so the data_race
455 * is safe.
456 */
457 if (data_race(sis->flags & SWP_FS_OPS))
458 swap_writepage_fs(folio, swap_plug);
459 /*
460 * ->flags can be updated non-atomicially (scan_swap_map_slots),
461 * but that will never affect SWP_SYNCHRONOUS_IO, so the data_race
462 * is safe.
463 */
464 else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO))
465 swap_writepage_bdev_sync(folio, sis);
466 else
467 swap_writepage_bdev_async(folio, sis);
468}
469
470void swap_write_unplug(struct swap_iocb *sio)
471{
472 struct iov_iter from;
473 struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
474 int ret;
475
476 iov_iter_bvec(i: &from, ITER_SOURCE, bvec: sio->bvec, nr_segs: sio->pages, count: sio->len);
477 ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
478 if (ret != -EIOCBQUEUED)
479 sio_write_complete(iocb: &sio->iocb, ret);
480}
481
482static void sio_read_complete(struct kiocb *iocb, long ret)
483{
484 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
485 int p;
486
487 if (ret == sio->len) {
488 for (p = 0; p < sio->pages; p++) {
489 struct folio *folio = page_folio(sio->bvec[p].bv_page);
490
491 count_mthp_stat(order: folio_order(folio), item: MTHP_STAT_SWPIN);
492 count_memcg_folio_events(folio, idx: PSWPIN, nr: folio_nr_pages(folio));
493 folio_mark_uptodate(folio);
494 folio_unlock(folio);
495 }
496 count_vm_events(item: PSWPIN, delta: sio->pages);
497 } else {
498 for (p = 0; p < sio->pages; p++) {
499 struct folio *folio = page_folio(sio->bvec[p].bv_page);
500
501 folio_unlock(folio);
502 }
503 pr_alert_ratelimited("Read-error on swap-device\n");
504 }
505 mempool_free(element: sio, pool: sio_pool);
506}
507
508static bool swap_read_folio_zeromap(struct folio *folio)
509{
510 int nr_pages = folio_nr_pages(folio);
511 struct obj_cgroup *objcg;
512 bool is_zeromap;
513
514 /*
515 * Swapping in a large folio that is partially in the zeromap is not
516 * currently handled. Return true without marking the folio uptodate so
517 * that an IO error is emitted (e.g. do_swap_page() will sigbus).
518 */
519 if (WARN_ON_ONCE(swap_zeromap_batch(folio->swap, nr_pages,
520 &is_zeromap) != nr_pages))
521 return true;
522
523 if (!is_zeromap)
524 return false;
525
526 objcg = get_obj_cgroup_from_folio(folio);
527 count_vm_events(item: SWPIN_ZERO, delta: nr_pages);
528 if (objcg) {
529 count_objcg_events(objcg, idx: SWPIN_ZERO, count: nr_pages);
530 obj_cgroup_put(objcg);
531 }
532
533 folio_zero_range(folio, start: 0, length: folio_size(folio));
534 folio_mark_uptodate(folio);
535 return true;
536}
537
538static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug)
539{
540 struct swap_info_struct *sis = __swap_entry_to_info(entry: folio->swap);
541 struct swap_iocb *sio = NULL;
542 loff_t pos = swap_dev_pos(entry: folio->swap);
543
544 if (plug)
545 sio = *plug;
546 if (sio) {
547 if (sio->iocb.ki_filp != sis->swap_file ||
548 sio->iocb.ki_pos + sio->len != pos) {
549 swap_read_unplug(plug: sio);
550 sio = NULL;
551 }
552 }
553 if (!sio) {
554 sio = mempool_alloc(sio_pool, GFP_KERNEL);
555 init_sync_kiocb(kiocb: &sio->iocb, filp: sis->swap_file);
556 sio->iocb.ki_pos = pos;
557 sio->iocb.ki_complete = sio_read_complete;
558 sio->pages = 0;
559 sio->len = 0;
560 }
561 bvec_set_folio(bv: &sio->bvec[sio->pages], folio, len: folio_size(folio), offset: 0);
562 sio->len += folio_size(folio);
563 sio->pages += 1;
564 if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) {
565 swap_read_unplug(plug: sio);
566 sio = NULL;
567 }
568 if (plug)
569 *plug = sio;
570}
571
572static void swap_read_folio_bdev_sync(struct folio *folio,
573 struct swap_info_struct *sis)
574{
575 struct bio_vec bv;
576 struct bio bio;
577
578 bio_init(bio: &bio, bdev: sis->bdev, table: &bv, max_vecs: 1, opf: REQ_OP_READ);
579 bio.bi_iter.bi_sector = swap_folio_sector(folio);
580 bio_add_folio_nofail(bio: &bio, folio, len: folio_size(folio), off: 0);
581 /*
582 * Keep this task valid during swap readpage because the oom killer may
583 * attempt to access it in the page fault retry time check.
584 */
585 get_task_struct(current);
586 count_mthp_stat(order: folio_order(folio), item: MTHP_STAT_SWPIN);
587 count_memcg_folio_events(folio, idx: PSWPIN, nr: folio_nr_pages(folio));
588 count_vm_events(item: PSWPIN, delta: folio_nr_pages(folio));
589 submit_bio_wait(bio: &bio);
590 __end_swap_bio_read(bio: &bio);
591 put_task_struct(current);
592}
593
594static void swap_read_folio_bdev_async(struct folio *folio,
595 struct swap_info_struct *sis)
596{
597 struct bio *bio;
598
599 bio = bio_alloc(bdev: sis->bdev, nr_vecs: 1, opf: REQ_OP_READ, GFP_KERNEL);
600 bio->bi_iter.bi_sector = swap_folio_sector(folio);
601 bio->bi_end_io = end_swap_bio_read;
602 bio_add_folio_nofail(bio, folio, len: folio_size(folio), off: 0);
603 count_mthp_stat(order: folio_order(folio), item: MTHP_STAT_SWPIN);
604 count_memcg_folio_events(folio, idx: PSWPIN, nr: folio_nr_pages(folio));
605 count_vm_events(item: PSWPIN, delta: folio_nr_pages(folio));
606 submit_bio(bio);
607}
608
609void swap_read_folio(struct folio *folio, struct swap_iocb **plug)
610{
611 struct swap_info_struct *sis = __swap_entry_to_info(entry: folio->swap);
612 bool synchronous = sis->flags & SWP_SYNCHRONOUS_IO;
613 bool workingset = folio_test_workingset(folio);
614 unsigned long pflags;
615 bool in_thrashing;
616
617 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio);
618 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
619 VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);
620
621 /*
622 * Count submission time as memory stall and delay. When the device
623 * is congested, or the submitting cgroup IO-throttled, submission
624 * can be a significant part of overall IO time.
625 */
626 if (workingset) {
627 delayacct_thrashing_start(in_thrashing: &in_thrashing);
628 psi_memstall_enter(flags: &pflags);
629 }
630 delayacct_swapin_start();
631
632 if (swap_read_folio_zeromap(folio)) {
633 folio_unlock(folio);
634 goto finish;
635 }
636
637 if (zswap_load(folio) != -ENOENT)
638 goto finish;
639
640 /* We have to read from slower devices. Increase zswap protection. */
641 zswap_folio_swapin(folio);
642
643 if (data_race(sis->flags & SWP_FS_OPS)) {
644 swap_read_folio_fs(folio, plug);
645 } else if (synchronous) {
646 swap_read_folio_bdev_sync(folio, sis);
647 } else {
648 swap_read_folio_bdev_async(folio, sis);
649 }
650
651finish:
652 if (workingset) {
653 delayacct_thrashing_end(in_thrashing: &in_thrashing);
654 psi_memstall_leave(flags: &pflags);
655 }
656 delayacct_swapin_end();
657}
658
659void __swap_read_unplug(struct swap_iocb *sio)
660{
661 struct iov_iter from;
662 struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
663 int ret;
664
665 iov_iter_bvec(i: &from, ITER_DEST, bvec: sio->bvec, nr_segs: sio->pages, count: sio->len);
666 ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
667 if (ret != -EIOCBQUEUED)
668 sio_read_complete(iocb: &sio->iocb, ret);
669}
670