Line data Source code
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/frontswap.h>
23 : #include <linux/blkdev.h>
24 : #include <linux/psi.h>
25 : #include <linux/uio.h>
26 : #include <linux/sched/task.h>
27 : #include <linux/delayacct.h>
28 : #include "swap.h"
29 :
30 0 : static void __end_swap_bio_write(struct bio *bio)
31 : {
32 0 : struct page *page = bio_first_page_all(bio);
33 :
34 0 : if (bio->bi_status) {
35 0 : SetPageError(page);
36 : /*
37 : * We failed to write the page out to swap-space.
38 : * Re-dirty the page in order to avoid it being reclaimed.
39 : * Also print a dire warning that things will go BAD (tm)
40 : * very quickly.
41 : *
42 : * Also clear PG_reclaim to avoid folio_rotate_reclaimable()
43 : */
44 0 : set_page_dirty(page);
45 0 : pr_alert_ratelimited("Write-error on swap-device (%u:%u:%llu)\n",
46 : MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
47 : (unsigned long long)bio->bi_iter.bi_sector);
48 : ClearPageReclaim(page);
49 : }
50 0 : end_page_writeback(page);
51 0 : }
52 :
53 0 : static void end_swap_bio_write(struct bio *bio)
54 : {
55 0 : __end_swap_bio_write(bio);
56 0 : bio_put(bio);
57 0 : }
58 :
59 0 : static void __end_swap_bio_read(struct bio *bio)
60 : {
61 0 : struct page *page = bio_first_page_all(bio);
62 :
63 0 : if (bio->bi_status) {
64 0 : SetPageError(page);
65 0 : ClearPageUptodate(page);
66 0 : pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n",
67 : MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
68 : (unsigned long long)bio->bi_iter.bi_sector);
69 : } else {
70 : SetPageUptodate(page);
71 : }
72 0 : unlock_page(page);
73 0 : }
74 :
75 0 : static void end_swap_bio_read(struct bio *bio)
76 : {
77 0 : __end_swap_bio_read(bio);
78 0 : bio_put(bio);
79 0 : }
80 :
81 0 : int generic_swapfile_activate(struct swap_info_struct *sis,
82 : struct file *swap_file,
83 : sector_t *span)
84 : {
85 0 : struct address_space *mapping = swap_file->f_mapping;
86 0 : struct inode *inode = mapping->host;
87 : unsigned blocks_per_page;
88 : unsigned long page_no;
89 : unsigned blkbits;
90 : sector_t probe_block;
91 : sector_t last_block;
92 0 : sector_t lowest_block = -1;
93 0 : sector_t highest_block = 0;
94 0 : int nr_extents = 0;
95 : int ret;
96 :
97 0 : blkbits = inode->i_blkbits;
98 0 : blocks_per_page = PAGE_SIZE >> blkbits;
99 :
100 : /*
101 : * Map all the blocks into the extent tree. This code doesn't try
102 : * to be very smart.
103 : */
104 0 : probe_block = 0;
105 0 : page_no = 0;
106 0 : last_block = i_size_read(inode) >> blkbits;
107 0 : while ((probe_block + blocks_per_page) <= last_block &&
108 0 : page_no < sis->max) {
109 : unsigned block_in_page;
110 : sector_t first_block;
111 :
112 0 : cond_resched();
113 :
114 0 : first_block = probe_block;
115 0 : ret = bmap(inode, &first_block);
116 0 : if (ret || !first_block)
117 : goto bad_bmap;
118 :
119 : /*
120 : * It must be PAGE_SIZE aligned on-disk
121 : */
122 0 : if (first_block & (blocks_per_page - 1)) {
123 0 : probe_block++;
124 0 : goto reprobe;
125 : }
126 :
127 0 : for (block_in_page = 1; block_in_page < blocks_per_page;
128 0 : block_in_page++) {
129 : sector_t block;
130 :
131 0 : block = probe_block + block_in_page;
132 0 : ret = bmap(inode, &block);
133 0 : if (ret || !block)
134 : goto bad_bmap;
135 :
136 0 : if (block != first_block + block_in_page) {
137 : /* Discontiguity */
138 0 : probe_block++;
139 0 : goto reprobe;
140 : }
141 : }
142 :
143 0 : first_block >>= (PAGE_SHIFT - blkbits);
144 0 : if (page_no) { /* exclude the header page */
145 0 : if (first_block < lowest_block)
146 0 : lowest_block = first_block;
147 0 : if (first_block > highest_block)
148 0 : highest_block = first_block;
149 : }
150 :
151 : /*
152 : * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
153 : */
154 0 : ret = add_swap_extent(sis, page_no, 1, first_block);
155 0 : if (ret < 0)
156 : goto out;
157 0 : nr_extents += ret;
158 0 : page_no++;
159 0 : probe_block += blocks_per_page;
160 : reprobe:
161 0 : continue;
162 : }
163 0 : ret = nr_extents;
164 0 : *span = 1 + highest_block - lowest_block;
165 0 : if (page_no == 0)
166 0 : page_no = 1; /* force Empty message */
167 0 : sis->max = page_no;
168 0 : sis->pages = page_no - 1;
169 0 : sis->highest_bit = page_no - 1;
170 : out:
171 0 : return ret;
172 : bad_bmap:
173 0 : pr_err("swapon: swapfile has holes\n");
174 0 : ret = -EINVAL;
175 0 : goto out;
176 : }
177 :
178 : /*
179 : * We may have stale swap cache pages in memory: notice
180 : * them here and get rid of the unnecessary final write.
181 : */
182 0 : int swap_writepage(struct page *page, struct writeback_control *wbc)
183 : {
184 0 : struct folio *folio = page_folio(page);
185 : int ret;
186 :
187 0 : if (folio_free_swap(folio)) {
188 0 : folio_unlock(folio);
189 0 : return 0;
190 : }
191 : /*
192 : * Arch code may have to preserve more data than just the page
193 : * contents, e.g. memory tags.
194 : */
195 0 : ret = arch_prepare_to_swap(&folio->page);
196 : if (ret) {
197 : folio_mark_dirty(folio);
198 : folio_unlock(folio);
199 : return ret;
200 : }
201 0 : if (frontswap_store(&folio->page) == 0) {
202 : folio_start_writeback(folio);
203 : folio_unlock(folio);
204 : folio_end_writeback(folio);
205 : return 0;
206 : }
207 0 : __swap_writepage(&folio->page, wbc);
208 0 : return 0;
209 : }
210 :
211 : static inline void count_swpout_vm_event(struct page *page)
212 : {
213 : #ifdef CONFIG_TRANSPARENT_HUGEPAGE
214 : if (unlikely(PageTransHuge(page)))
215 : count_vm_event(THP_SWPOUT);
216 : #endif
217 0 : count_vm_events(PSWPOUT, thp_nr_pages(page));
218 : }
219 :
220 : #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
221 : static void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
222 : {
223 : struct cgroup_subsys_state *css;
224 : struct mem_cgroup *memcg;
225 :
226 : memcg = page_memcg(page);
227 : if (!memcg)
228 : return;
229 :
230 : rcu_read_lock();
231 : css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
232 : bio_associate_blkg_from_css(bio, css);
233 : rcu_read_unlock();
234 : }
235 : #else
236 : #define bio_associate_blkg_from_page(bio, page) do { } while (0)
237 : #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
238 :
239 : struct swap_iocb {
240 : struct kiocb iocb;
241 : struct bio_vec bvec[SWAP_CLUSTER_MAX];
242 : int pages;
243 : int len;
244 : };
245 : static mempool_t *sio_pool;
246 :
247 0 : int sio_pool_init(void)
248 : {
249 0 : if (!sio_pool) {
250 0 : mempool_t *pool = mempool_create_kmalloc_pool(
251 : SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
252 0 : if (cmpxchg(&sio_pool, NULL, pool))
253 0 : mempool_destroy(pool);
254 : }
255 0 : if (!sio_pool)
256 : return -ENOMEM;
257 0 : return 0;
258 : }
259 :
260 0 : static void sio_write_complete(struct kiocb *iocb, long ret)
261 : {
262 0 : struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
263 0 : struct page *page = sio->bvec[0].bv_page;
264 : int p;
265 :
266 0 : if (ret != sio->len) {
267 : /*
268 : * In the case of swap-over-nfs, this can be a
269 : * temporary failure if the system has limited
270 : * memory for allocating transmit buffers.
271 : * Mark the page dirty and avoid
272 : * folio_rotate_reclaimable but rate-limit the
273 : * messages but do not flag PageError like
274 : * the normal direct-to-bio case as it could
275 : * be temporary.
276 : */
277 0 : pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
278 : ret, page_file_offset(page));
279 0 : for (p = 0; p < sio->pages; p++) {
280 0 : page = sio->bvec[p].bv_page;
281 0 : set_page_dirty(page);
282 0 : ClearPageReclaim(page);
283 : }
284 : } else {
285 0 : for (p = 0; p < sio->pages; p++)
286 0 : count_swpout_vm_event(sio->bvec[p].bv_page);
287 : }
288 :
289 0 : for (p = 0; p < sio->pages; p++)
290 0 : end_page_writeback(sio->bvec[p].bv_page);
291 :
292 0 : mempool_free(sio, sio_pool);
293 0 : }
294 :
295 0 : static void swap_writepage_fs(struct page *page, struct writeback_control *wbc)
296 : {
297 0 : struct swap_iocb *sio = NULL;
298 0 : struct swap_info_struct *sis = page_swap_info(page);
299 0 : struct file *swap_file = sis->swap_file;
300 0 : loff_t pos = page_file_offset(page);
301 :
302 0 : set_page_writeback(page);
303 0 : unlock_page(page);
304 0 : if (wbc->swap_plug)
305 0 : sio = *wbc->swap_plug;
306 0 : if (sio) {
307 0 : if (sio->iocb.ki_filp != swap_file ||
308 0 : sio->iocb.ki_pos + sio->len != pos) {
309 0 : swap_write_unplug(sio);
310 0 : sio = NULL;
311 : }
312 : }
313 0 : if (!sio) {
314 0 : sio = mempool_alloc(sio_pool, GFP_NOIO);
315 0 : init_sync_kiocb(&sio->iocb, swap_file);
316 0 : sio->iocb.ki_complete = sio_write_complete;
317 0 : sio->iocb.ki_pos = pos;
318 0 : sio->pages = 0;
319 0 : sio->len = 0;
320 : }
321 0 : bvec_set_page(&sio->bvec[sio->pages], page, thp_size(page), 0);
322 0 : sio->len += thp_size(page);
323 0 : sio->pages += 1;
324 0 : if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) {
325 0 : swap_write_unplug(sio);
326 0 : sio = NULL;
327 : }
328 0 : if (wbc->swap_plug)
329 0 : *wbc->swap_plug = sio;
330 0 : }
331 :
332 0 : static void swap_writepage_bdev_sync(struct page *page,
333 : struct writeback_control *wbc, struct swap_info_struct *sis)
334 : {
335 : struct bio_vec bv;
336 : struct bio bio;
337 :
338 0 : bio_init(&bio, sis->bdev, &bv, 1,
339 0 : REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc));
340 0 : bio.bi_iter.bi_sector = swap_page_sector(page);
341 0 : bio_add_page(&bio, page, thp_size(page), 0);
342 :
343 : bio_associate_blkg_from_page(&bio, page);
344 0 : count_swpout_vm_event(page);
345 :
346 0 : set_page_writeback(page);
347 0 : unlock_page(page);
348 :
349 0 : submit_bio_wait(&bio);
350 0 : __end_swap_bio_write(&bio);
351 0 : }
352 :
353 0 : static void swap_writepage_bdev_async(struct page *page,
354 : struct writeback_control *wbc, struct swap_info_struct *sis)
355 : {
356 : struct bio *bio;
357 :
358 0 : bio = bio_alloc(sis->bdev, 1,
359 0 : REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
360 : GFP_NOIO);
361 0 : bio->bi_iter.bi_sector = swap_page_sector(page);
362 0 : bio->bi_end_io = end_swap_bio_write;
363 0 : bio_add_page(bio, page, thp_size(page), 0);
364 :
365 : bio_associate_blkg_from_page(bio, page);
366 0 : count_swpout_vm_event(page);
367 0 : set_page_writeback(page);
368 0 : unlock_page(page);
369 0 : submit_bio(bio);
370 0 : }
371 :
372 0 : void __swap_writepage(struct page *page, struct writeback_control *wbc)
373 : {
374 0 : struct swap_info_struct *sis = page_swap_info(page);
375 :
376 : VM_BUG_ON_PAGE(!PageSwapCache(page), page);
377 : /*
378 : * ->flags can be updated non-atomicially (scan_swap_map_slots),
379 : * but that will never affect SWP_FS_OPS, so the data_race
380 : * is safe.
381 : */
382 0 : if (data_race(sis->flags & SWP_FS_OPS))
383 0 : swap_writepage_fs(page, wbc);
384 0 : else if (sis->flags & SWP_SYNCHRONOUS_IO)
385 0 : swap_writepage_bdev_sync(page, wbc, sis);
386 : else
387 0 : swap_writepage_bdev_async(page, wbc, sis);
388 0 : }
389 :
390 0 : void swap_write_unplug(struct swap_iocb *sio)
391 : {
392 : struct iov_iter from;
393 0 : struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
394 : int ret;
395 :
396 0 : iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len);
397 0 : ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
398 0 : if (ret != -EIOCBQUEUED)
399 0 : sio_write_complete(&sio->iocb, ret);
400 0 : }
401 :
402 0 : static void sio_read_complete(struct kiocb *iocb, long ret)
403 : {
404 0 : struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
405 : int p;
406 :
407 0 : if (ret == sio->len) {
408 0 : for (p = 0; p < sio->pages; p++) {
409 0 : struct page *page = sio->bvec[p].bv_page;
410 :
411 0 : SetPageUptodate(page);
412 0 : unlock_page(page);
413 : }
414 0 : count_vm_events(PSWPIN, sio->pages);
415 : } else {
416 0 : for (p = 0; p < sio->pages; p++) {
417 0 : struct page *page = sio->bvec[p].bv_page;
418 :
419 0 : SetPageError(page);
420 0 : ClearPageUptodate(page);
421 0 : unlock_page(page);
422 : }
423 0 : pr_alert_ratelimited("Read-error on swap-device\n");
424 : }
425 0 : mempool_free(sio, sio_pool);
426 0 : }
427 :
428 0 : static void swap_readpage_fs(struct page *page,
429 : struct swap_iocb **plug)
430 : {
431 0 : struct swap_info_struct *sis = page_swap_info(page);
432 0 : struct swap_iocb *sio = NULL;
433 0 : loff_t pos = page_file_offset(page);
434 :
435 0 : if (plug)
436 0 : sio = *plug;
437 0 : if (sio) {
438 0 : if (sio->iocb.ki_filp != sis->swap_file ||
439 0 : sio->iocb.ki_pos + sio->len != pos) {
440 0 : swap_read_unplug(sio);
441 0 : sio = NULL;
442 : }
443 : }
444 0 : if (!sio) {
445 0 : sio = mempool_alloc(sio_pool, GFP_KERNEL);
446 0 : init_sync_kiocb(&sio->iocb, sis->swap_file);
447 0 : sio->iocb.ki_pos = pos;
448 0 : sio->iocb.ki_complete = sio_read_complete;
449 0 : sio->pages = 0;
450 0 : sio->len = 0;
451 : }
452 0 : bvec_set_page(&sio->bvec[sio->pages], page, thp_size(page), 0);
453 0 : sio->len += thp_size(page);
454 0 : sio->pages += 1;
455 0 : if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) {
456 : swap_read_unplug(sio);
457 : sio = NULL;
458 : }
459 0 : if (plug)
460 0 : *plug = sio;
461 0 : }
462 :
463 0 : static void swap_readpage_bdev_sync(struct page *page,
464 : struct swap_info_struct *sis)
465 : {
466 : struct bio_vec bv;
467 : struct bio bio;
468 :
469 0 : bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ);
470 0 : bio.bi_iter.bi_sector = swap_page_sector(page);
471 0 : bio_add_page(&bio, page, thp_size(page), 0);
472 : /*
473 : * Keep this task valid during swap readpage because the oom killer may
474 : * attempt to access it in the page fault retry time check.
475 : */
476 0 : get_task_struct(current);
477 0 : count_vm_event(PSWPIN);
478 0 : submit_bio_wait(&bio);
479 0 : __end_swap_bio_read(&bio);
480 0 : put_task_struct(current);
481 0 : }
482 :
483 0 : static void swap_readpage_bdev_async(struct page *page,
484 : struct swap_info_struct *sis)
485 : {
486 : struct bio *bio;
487 :
488 0 : bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL);
489 0 : bio->bi_iter.bi_sector = swap_page_sector(page);
490 0 : bio->bi_end_io = end_swap_bio_read;
491 0 : bio_add_page(bio, page, thp_size(page), 0);
492 0 : count_vm_event(PSWPIN);
493 0 : submit_bio(bio);
494 0 : }
495 :
496 0 : void swap_readpage(struct page *page, bool synchronous, struct swap_iocb **plug)
497 : {
498 0 : struct swap_info_struct *sis = page_swap_info(page);
499 0 : bool workingset = PageWorkingset(page);
500 : unsigned long pflags;
501 : bool in_thrashing;
502 :
503 : VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
504 : VM_BUG_ON_PAGE(!PageLocked(page), page);
505 : VM_BUG_ON_PAGE(PageUptodate(page), page);
506 :
507 : /*
508 : * Count submission time as memory stall and delay. When the device
509 : * is congested, or the submitting cgroup IO-throttled, submission
510 : * can be a significant part of overall IO time.
511 : */
512 : if (workingset) {
513 : delayacct_thrashing_start(&in_thrashing);
514 : psi_memstall_enter(&pflags);
515 : }
516 : delayacct_swapin_start();
517 :
518 0 : if (frontswap_load(page) == 0) {
519 : SetPageUptodate(page);
520 : unlock_page(page);
521 0 : } else if (data_race(sis->flags & SWP_FS_OPS)) {
522 0 : swap_readpage_fs(page, plug);
523 0 : } else if (synchronous || (sis->flags & SWP_SYNCHRONOUS_IO)) {
524 0 : swap_readpage_bdev_sync(page, sis);
525 : } else {
526 0 : swap_readpage_bdev_async(page, sis);
527 : }
528 :
529 : if (workingset) {
530 : delayacct_thrashing_end(&in_thrashing);
531 : psi_memstall_leave(&pflags);
532 : }
533 : delayacct_swapin_end();
534 0 : }
535 :
536 0 : void __swap_read_unplug(struct swap_iocb *sio)
537 : {
538 : struct iov_iter from;
539 0 : struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
540 : int ret;
541 :
542 0 : iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len);
543 0 : ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
544 0 : if (ret != -EIOCBQUEUED)
545 0 : sio_read_complete(&sio->iocb, ret);
546 0 : }
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