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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/buffer_head.h>
22#include <linux/writeback.h>
23#include <linux/frontswap.h>
24#include <linux/blkdev.h>
25#include <linux/uio.h>
26#include <linux/sched/task.h>
27#include <asm/pgtable.h>
28
29static struct bio *get_swap_bio(gfp_t gfp_flags,
30 struct page *page, bio_end_io_t end_io)
31{
32 struct bio *bio;
33
34 bio = bio_alloc(gfp_flags, 1);
35 if (bio) {
36 struct block_device *bdev;
37
38 bio->bi_iter.bi_sector = map_swap_page(page, &bdev);
39 bio_set_dev(bio, bdev);
40 bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
41 bio->bi_end_io = end_io;
42
43 bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0);
44 }
45 return bio;
46}
47
48void end_swap_bio_write(struct bio *bio)
49{
50 struct page *page = bio_first_page_all(bio);
51
52 if (bio->bi_status) {
53 SetPageError(page);
54 /*
55 * We failed to write the page out to swap-space.
56 * Re-dirty the page in order to avoid it being reclaimed.
57 * Also print a dire warning that things will go BAD (tm)
58 * very quickly.
59 *
60 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
61 */
62 set_page_dirty(page);
63 pr_alert("Write-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 ClearPageReclaim(page);
67 }
68 end_page_writeback(page);
69 bio_put(bio);
70}
71
72static void swap_slot_free_notify(struct page *page)
73{
74 struct swap_info_struct *sis;
75 struct gendisk *disk;
76 swp_entry_t entry;
77
78 /*
79 * There is no guarantee that the page is in swap cache - the software
80 * suspend code (at least) uses end_swap_bio_read() against a non-
81 * swapcache page. So we must check PG_swapcache before proceeding with
82 * this optimization.
83 */
84 if (unlikely(!PageSwapCache(page)))
85 return;
86
87 sis = page_swap_info(page);
88 if (!(sis->flags & SWP_BLKDEV))
89 return;
90
91 /*
92 * The swap subsystem performs lazy swap slot freeing,
93 * expecting that the page will be swapped out again.
94 * So we can avoid an unnecessary write if the page
95 * isn't redirtied.
96 * This is good for real swap storage because we can
97 * reduce unnecessary I/O and enhance wear-leveling
98 * if an SSD is used as the as swap device.
99 * But if in-memory swap device (eg zram) is used,
100 * this causes a duplicated copy between uncompressed
101 * data in VM-owned memory and compressed data in
102 * zram-owned memory. So let's free zram-owned memory
103 * and make the VM-owned decompressed page *dirty*,
104 * so the page should be swapped out somewhere again if
105 * we again wish to reclaim it.
106 */
107 disk = sis->bdev->bd_disk;
108 entry.val = page_private(page);
109 if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) {
110 unsigned long offset;
111
112 offset = swp_offset(entry);
113
114 SetPageDirty(page);
115 disk->fops->swap_slot_free_notify(sis->bdev,
116 offset);
117 }
118}
119
120static void end_swap_bio_read(struct bio *bio)
121{
122 struct page *page = bio_first_page_all(bio);
123 struct task_struct *waiter = bio->bi_private;
124
125 if (bio->bi_status) {
126 SetPageError(page);
127 ClearPageUptodate(page);
128 pr_alert("Read-error on swap-device (%u:%u:%llu)\n",
129 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
130 (unsigned long long)bio->bi_iter.bi_sector);
131 goto out;
132 }
133
134 SetPageUptodate(page);
135 swap_slot_free_notify(page);
136out:
137 unlock_page(page);
138 WRITE_ONCE(bio->bi_private, NULL);
139 bio_put(bio);
140 if (waiter) {
141 blk_wake_io_task(waiter);
142 put_task_struct(waiter);
143 }
144}
145
146int generic_swapfile_activate(struct swap_info_struct *sis,
147 struct file *swap_file,
148 sector_t *span)
149{
150 struct address_space *mapping = swap_file->f_mapping;
151 struct inode *inode = mapping->host;
152 unsigned blocks_per_page;
153 unsigned long page_no;
154 unsigned blkbits;
155 sector_t probe_block;
156 sector_t last_block;
157 sector_t lowest_block = -1;
158 sector_t highest_block = 0;
159 int nr_extents = 0;
160 int ret;
161
162 blkbits = inode->i_blkbits;
163 blocks_per_page = PAGE_SIZE >> blkbits;
164
165 /*
166 * Map all the blocks into the extent tree. This code doesn't try
167 * to be very smart.
168 */
169 probe_block = 0;
170 page_no = 0;
171 last_block = i_size_read(inode) >> blkbits;
172 while ((probe_block + blocks_per_page) <= last_block &&
173 page_no < sis->max) {
174 unsigned block_in_page;
175 sector_t first_block;
176
177 cond_resched();
178
179 first_block = bmap(inode, probe_block);
180 if (first_block == 0)
181 goto bad_bmap;
182
183 /*
184 * It must be PAGE_SIZE aligned on-disk
185 */
186 if (first_block & (blocks_per_page - 1)) {
187 probe_block++;
188 goto reprobe;
189 }
190
191 for (block_in_page = 1; block_in_page < blocks_per_page;
192 block_in_page++) {
193 sector_t block;
194
195 block = bmap(inode, probe_block + block_in_page);
196 if (block == 0)
197 goto bad_bmap;
198 if (block != first_block + block_in_page) {
199 /* Discontiguity */
200 probe_block++;
201 goto reprobe;
202 }
203 }
204
205 first_block >>= (PAGE_SHIFT - blkbits);
206 if (page_no) { /* exclude the header page */
207 if (first_block < lowest_block)
208 lowest_block = first_block;
209 if (first_block > highest_block)
210 highest_block = first_block;
211 }
212
213 /*
214 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
215 */
216 ret = add_swap_extent(sis, page_no, 1, first_block);
217 if (ret < 0)
218 goto out;
219 nr_extents += ret;
220 page_no++;
221 probe_block += blocks_per_page;
222reprobe:
223 continue;
224 }
225 ret = nr_extents;
226 *span = 1 + highest_block - lowest_block;
227 if (page_no == 0)
228 page_no = 1; /* force Empty message */
229 sis->max = page_no;
230 sis->pages = page_no - 1;
231 sis->highest_bit = page_no - 1;
232out:
233 return ret;
234bad_bmap:
235 pr_err("swapon: swapfile has holes\n");
236 ret = -EINVAL;
237 goto out;
238}
239
240/*
241 * We may have stale swap cache pages in memory: notice
242 * them here and get rid of the unnecessary final write.
243 */
244int swap_writepage(struct page *page, struct writeback_control *wbc)
245{
246 int ret = 0;
247
248 if (try_to_free_swap(page)) {
249 unlock_page(page);
250 goto out;
251 }
252 if (frontswap_store(page) == 0) {
253 set_page_writeback(page);
254 unlock_page(page);
255 end_page_writeback(page);
256 goto out;
257 }
258 ret = __swap_writepage(page, wbc, end_swap_bio_write);
259out:
260 return ret;
261}
262
263static sector_t swap_page_sector(struct page *page)
264{
265 return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
266}
267
268static inline void count_swpout_vm_event(struct page *page)
269{
270#ifdef CONFIG_TRANSPARENT_HUGEPAGE
271 if (unlikely(PageTransHuge(page)))
272 count_vm_event(THP_SWPOUT);
273#endif
274 count_vm_events(PSWPOUT, hpage_nr_pages(page));
275}
276
277int __swap_writepage(struct page *page, struct writeback_control *wbc,
278 bio_end_io_t end_write_func)
279{
280 struct bio *bio;
281 int ret;
282 struct swap_info_struct *sis = page_swap_info(page);
283
284 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
285 if (sis->flags & SWP_FS) {
286 struct kiocb kiocb;
287 struct file *swap_file = sis->swap_file;
288 struct address_space *mapping = swap_file->f_mapping;
289 struct bio_vec bv = {
290 .bv_page = page,
291 .bv_len = PAGE_SIZE,
292 .bv_offset = 0
293 };
294 struct iov_iter from;
295
296 iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
297 init_sync_kiocb(&kiocb, swap_file);
298 kiocb.ki_pos = page_file_offset(page);
299
300 set_page_writeback(page);
301 unlock_page(page);
302 ret = mapping->a_ops->direct_IO(&kiocb, &from);
303 if (ret == PAGE_SIZE) {
304 count_vm_event(PSWPOUT);
305 ret = 0;
306 } else {
307 /*
308 * In the case of swap-over-nfs, this can be a
309 * temporary failure if the system has limited
310 * memory for allocating transmit buffers.
311 * Mark the page dirty and avoid
312 * rotate_reclaimable_page but rate-limit the
313 * messages but do not flag PageError like
314 * the normal direct-to-bio case as it could
315 * be temporary.
316 */
317 set_page_dirty(page);
318 ClearPageReclaim(page);
319 pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
320 page_file_offset(page));
321 }
322 end_page_writeback(page);
323 return ret;
324 }
325
326 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
327 if (!ret) {
328 count_swpout_vm_event(page);
329 return 0;
330 }
331
332 ret = 0;
333 bio = get_swap_bio(GFP_NOIO, page, end_write_func);
334 if (bio == NULL) {
335 set_page_dirty(page);
336 unlock_page(page);
337 ret = -ENOMEM;
338 goto out;
339 }
340 bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc);
341 bio_associate_blkg_from_page(bio, page);
342 count_swpout_vm_event(page);
343 set_page_writeback(page);
344 unlock_page(page);
345 submit_bio(bio);
346out:
347 return ret;
348}
349
350int swap_readpage(struct page *page, bool synchronous)
351{
352 struct bio *bio;
353 int ret = 0;
354 struct swap_info_struct *sis = page_swap_info(page);
355 blk_qc_t qc;
356 struct gendisk *disk;
357
358 VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
359 VM_BUG_ON_PAGE(!PageLocked(page), page);
360 VM_BUG_ON_PAGE(PageUptodate(page), page);
361 if (frontswap_load(page) == 0) {
362 SetPageUptodate(page);
363 unlock_page(page);
364 goto out;
365 }
366
367 if (sis->flags & SWP_FS) {
368 struct file *swap_file = sis->swap_file;
369 struct address_space *mapping = swap_file->f_mapping;
370
371 ret = mapping->a_ops->readpage(swap_file, page);
372 if (!ret)
373 count_vm_event(PSWPIN);
374 return ret;
375 }
376
377 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
378 if (!ret) {
379 if (trylock_page(page)) {
380 swap_slot_free_notify(page);
381 unlock_page(page);
382 }
383
384 count_vm_event(PSWPIN);
385 return 0;
386 }
387
388 ret = 0;
389 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
390 if (bio == NULL) {
391 unlock_page(page);
392 ret = -ENOMEM;
393 goto out;
394 }
395 disk = bio->bi_disk;
396 /*
397 * Keep this task valid during swap readpage because the oom killer may
398 * attempt to access it in the page fault retry time check.
399 */
400 bio_set_op_attrs(bio, REQ_OP_READ, 0);
401 if (synchronous) {
402 bio->bi_opf |= REQ_HIPRI;
403 get_task_struct(current);
404 bio->bi_private = current;
405 }
406 count_vm_event(PSWPIN);
407 bio_get(bio);
408 qc = submit_bio(bio);
409 while (synchronous) {
410 set_current_state(TASK_UNINTERRUPTIBLE);
411 if (!READ_ONCE(bio->bi_private))
412 break;
413
414 if (!blk_poll(disk->queue, qc, true))
415 io_schedule();
416 }
417 __set_current_state(TASK_RUNNING);
418 bio_put(bio);
419
420out:
421 return ret;
422}
423
424int swap_set_page_dirty(struct page *page)
425{
426 struct swap_info_struct *sis = page_swap_info(page);
427
428 if (sis->flags & SWP_FS) {
429 struct address_space *mapping = sis->swap_file->f_mapping;
430
431 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
432 return mapping->a_ops->set_page_dirty(page);
433 } else {
434 return __set_page_dirty_no_writeback(page);
435 }
436}
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, &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);
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, page_no, 1, 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;
166 sis->highest_bit = page_no - 1;
167out:
168 return ret;
169bad_bmap:
170 pr_err("swapon: swapfile has holes\n");
171 ret = -EINVAL;
172 goto out;
173}
174
175static bool is_folio_zero_filled(struct folio *folio)
176{
177 unsigned int pos, last_pos;
178 unsigned long *data;
179 unsigned int i;
180
181 last_pos = PAGE_SIZE / sizeof(*data) - 1;
182 for (i = 0; i < folio_nr_pages(folio); i++) {
183 data = kmap_local_folio(folio, i * PAGE_SIZE);
184 /*
185 * Check last word first, incase the page is zero-filled at
186 * the start and has non-zero data at the end, which is common
187 * in real-world workloads.
188 */
189 if (data[last_pos]) {
190 kunmap_local(data);
191 return false;
192 }
193 for (pos = 0; pos < last_pos; pos++) {
194 if (data[pos]) {
195 kunmap_local(data);
196 return false;
197 }
198 }
199 kunmap_local(data);
200 }
201
202 return true;
203}
204
205static void swap_zeromap_folio_set(struct folio *folio)
206{
207 struct obj_cgroup *objcg = get_obj_cgroup_from_folio(folio);
208 struct swap_info_struct *sis = swp_swap_info(folio->swap);
209 int nr_pages = folio_nr_pages(folio);
210 swp_entry_t entry;
211 unsigned int i;
212
213 for (i = 0; i < folio_nr_pages(folio); i++) {
214 entry = page_swap_entry(folio_page(folio, i));
215 set_bit(swp_offset(entry), sis->zeromap);
216 }
217
218 count_vm_events(SWPOUT_ZERO, nr_pages);
219 if (objcg) {
220 count_objcg_events(objcg, SWPOUT_ZERO, nr_pages);
221 obj_cgroup_put(objcg);
222 }
223}
224
225static void swap_zeromap_folio_clear(struct folio *folio)
226{
227 struct swap_info_struct *sis = swp_swap_info(folio->swap);
228 swp_entry_t entry;
229 unsigned int i;
230
231 for (i = 0; i < folio_nr_pages(folio); i++) {
232 entry = page_swap_entry(folio_page(folio, i));
233 clear_bit(swp_offset(entry), sis->zeromap);
234 }
235}
236
237/*
238 * We may have stale swap cache pages in memory: notice
239 * them here and get rid of the unnecessary final write.
240 */
241int swap_writepage(struct page *page, struct writeback_control *wbc)
242{
243 struct folio *folio = page_folio(page);
244 int ret;
245
246 if (folio_free_swap(folio)) {
247 folio_unlock(folio);
248 return 0;
249 }
250 /*
251 * Arch code may have to preserve more data than just the page
252 * contents, e.g. memory tags.
253 */
254 ret = arch_prepare_to_swap(folio);
255 if (ret) {
256 folio_mark_dirty(folio);
257 folio_unlock(folio);
258 return ret;
259 }
260
261 /*
262 * Use a bitmap (zeromap) to avoid doing IO for zero-filled pages.
263 * The bits in zeromap are protected by the locked swapcache folio
264 * and atomic updates are used to protect against read-modify-write
265 * corruption due to other zero swap entries seeing concurrent updates.
266 */
267 if (is_folio_zero_filled(folio)) {
268 swap_zeromap_folio_set(folio);
269 folio_unlock(folio);
270 return 0;
271 } else {
272 /*
273 * Clear bits this folio occupies in the zeromap to prevent
274 * zero data being read in from any previous zero writes that
275 * occupied the same swap entries.
276 */
277 swap_zeromap_folio_clear(folio);
278 }
279 if (zswap_store(folio)) {
280 count_mthp_stat(folio_order(folio), MTHP_STAT_ZSWPOUT);
281 folio_unlock(folio);
282 return 0;
283 }
284 if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) {
285 folio_mark_dirty(folio);
286 return AOP_WRITEPAGE_ACTIVATE;
287 }
288
289 __swap_writepage(folio, wbc);
290 return 0;
291}
292
293static inline void count_swpout_vm_event(struct folio *folio)
294{
295#ifdef CONFIG_TRANSPARENT_HUGEPAGE
296 if (unlikely(folio_test_pmd_mappable(folio))) {
297 count_memcg_folio_events(folio, THP_SWPOUT, 1);
298 count_vm_event(THP_SWPOUT);
299 }
300#endif
301 count_mthp_stat(folio_order(folio), MTHP_STAT_SWPOUT);
302 count_memcg_folio_events(folio, PSWPOUT, folio_nr_pages(folio));
303 count_vm_events(PSWPOUT, folio_nr_pages(folio));
304}
305
306#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
307static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)
308{
309 struct cgroup_subsys_state *css;
310 struct mem_cgroup *memcg;
311
312 memcg = folio_memcg(folio);
313 if (!memcg)
314 return;
315
316 rcu_read_lock();
317 css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
318 bio_associate_blkg_from_css(bio, css);
319 rcu_read_unlock();
320}
321#else
322#define bio_associate_blkg_from_page(bio, folio) do { } while (0)
323#endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
324
325struct swap_iocb {
326 struct kiocb iocb;
327 struct bio_vec bvec[SWAP_CLUSTER_MAX];
328 int pages;
329 int len;
330};
331static mempool_t *sio_pool;
332
333int sio_pool_init(void)
334{
335 if (!sio_pool) {
336 mempool_t *pool = mempool_create_kmalloc_pool(
337 SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
338 if (cmpxchg(&sio_pool, NULL, pool))
339 mempool_destroy(pool);
340 }
341 if (!sio_pool)
342 return -ENOMEM;
343 return 0;
344}
345
346static void sio_write_complete(struct kiocb *iocb, long ret)
347{
348 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
349 struct page *page = sio->bvec[0].bv_page;
350 int p;
351
352 if (ret != sio->len) {
353 /*
354 * In the case of swap-over-nfs, this can be a
355 * temporary failure if the system has limited
356 * memory for allocating transmit buffers.
357 * Mark the page dirty and avoid
358 * folio_rotate_reclaimable but rate-limit the
359 * messages.
360 */
361 pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
362 ret, swap_dev_pos(page_swap_entry(page)));
363 for (p = 0; p < sio->pages; p++) {
364 page = sio->bvec[p].bv_page;
365 set_page_dirty(page);
366 ClearPageReclaim(page);
367 }
368 }
369
370 for (p = 0; p < sio->pages; p++)
371 end_page_writeback(sio->bvec[p].bv_page);
372
373 mempool_free(sio, sio_pool);
374}
375
376static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc)
377{
378 struct swap_iocb *sio = NULL;
379 struct swap_info_struct *sis = swp_swap_info(folio->swap);
380 struct file *swap_file = sis->swap_file;
381 loff_t pos = swap_dev_pos(folio->swap);
382
383 count_swpout_vm_event(folio);
384 folio_start_writeback(folio);
385 folio_unlock(folio);
386 if (wbc->swap_plug)
387 sio = *wbc->swap_plug;
388 if (sio) {
389 if (sio->iocb.ki_filp != swap_file ||
390 sio->iocb.ki_pos + sio->len != pos) {
391 swap_write_unplug(sio);
392 sio = NULL;
393 }
394 }
395 if (!sio) {
396 sio = mempool_alloc(sio_pool, GFP_NOIO);
397 init_sync_kiocb(&sio->iocb, swap_file);
398 sio->iocb.ki_complete = sio_write_complete;
399 sio->iocb.ki_pos = pos;
400 sio->pages = 0;
401 sio->len = 0;
402 }
403 bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
404 sio->len += folio_size(folio);
405 sio->pages += 1;
406 if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) {
407 swap_write_unplug(sio);
408 sio = NULL;
409 }
410 if (wbc->swap_plug)
411 *wbc->swap_plug = sio;
412}
413
414static void swap_writepage_bdev_sync(struct folio *folio,
415 struct writeback_control *wbc, struct swap_info_struct *sis)
416{
417 struct bio_vec bv;
418 struct bio bio;
419
420 bio_init(&bio, sis->bdev, &bv, 1,
421 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc));
422 bio.bi_iter.bi_sector = swap_folio_sector(folio);
423 bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
424
425 bio_associate_blkg_from_page(&bio, folio);
426 count_swpout_vm_event(folio);
427
428 folio_start_writeback(folio);
429 folio_unlock(folio);
430
431 submit_bio_wait(&bio);
432 __end_swap_bio_write(&bio);
433}
434
435static void swap_writepage_bdev_async(struct folio *folio,
436 struct writeback_control *wbc, struct swap_info_struct *sis)
437{
438 struct bio *bio;
439
440 bio = bio_alloc(sis->bdev, 1,
441 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
442 GFP_NOIO);
443 bio->bi_iter.bi_sector = swap_folio_sector(folio);
444 bio->bi_end_io = end_swap_bio_write;
445 bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
446
447 bio_associate_blkg_from_page(bio, folio);
448 count_swpout_vm_event(folio);
449 folio_start_writeback(folio);
450 folio_unlock(folio);
451 submit_bio(bio);
452}
453
454void __swap_writepage(struct folio *folio, struct writeback_control *wbc)
455{
456 struct swap_info_struct *sis = swp_swap_info(folio->swap);
457
458 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
459 /*
460 * ->flags can be updated non-atomicially (scan_swap_map_slots),
461 * but that will never affect SWP_FS_OPS, so the data_race
462 * is safe.
463 */
464 if (data_race(sis->flags & SWP_FS_OPS))
465 swap_writepage_fs(folio, wbc);
466 /*
467 * ->flags can be updated non-atomicially (scan_swap_map_slots),
468 * but that will never affect SWP_SYNCHRONOUS_IO, so the data_race
469 * is safe.
470 */
471 else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO))
472 swap_writepage_bdev_sync(folio, wbc, sis);
473 else
474 swap_writepage_bdev_async(folio, wbc, sis);
475}
476
477void swap_write_unplug(struct swap_iocb *sio)
478{
479 struct iov_iter from;
480 struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
481 int ret;
482
483 iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len);
484 ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
485 if (ret != -EIOCBQUEUED)
486 sio_write_complete(&sio->iocb, ret);
487}
488
489static void sio_read_complete(struct kiocb *iocb, long ret)
490{
491 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
492 int p;
493
494 if (ret == sio->len) {
495 for (p = 0; p < sio->pages; p++) {
496 struct folio *folio = page_folio(sio->bvec[p].bv_page);
497
498 count_mthp_stat(folio_order(folio), MTHP_STAT_SWPIN);
499 count_memcg_folio_events(folio, PSWPIN, folio_nr_pages(folio));
500 folio_mark_uptodate(folio);
501 folio_unlock(folio);
502 }
503 count_vm_events(PSWPIN, sio->pages);
504 } else {
505 for (p = 0; p < sio->pages; p++) {
506 struct folio *folio = page_folio(sio->bvec[p].bv_page);
507
508 folio_unlock(folio);
509 }
510 pr_alert_ratelimited("Read-error on swap-device\n");
511 }
512 mempool_free(sio, sio_pool);
513}
514
515static bool swap_read_folio_zeromap(struct folio *folio)
516{
517 int nr_pages = folio_nr_pages(folio);
518 struct obj_cgroup *objcg;
519 bool is_zeromap;
520
521 /*
522 * Swapping in a large folio that is partially in the zeromap is not
523 * currently handled. Return true without marking the folio uptodate so
524 * that an IO error is emitted (e.g. do_swap_page() will sigbus).
525 */
526 if (WARN_ON_ONCE(swap_zeromap_batch(folio->swap, nr_pages,
527 &is_zeromap) != nr_pages))
528 return true;
529
530 if (!is_zeromap)
531 return false;
532
533 objcg = get_obj_cgroup_from_folio(folio);
534 count_vm_events(SWPIN_ZERO, nr_pages);
535 if (objcg) {
536 count_objcg_events(objcg, SWPIN_ZERO, nr_pages);
537 obj_cgroup_put(objcg);
538 }
539
540 folio_zero_range(folio, 0, folio_size(folio));
541 folio_mark_uptodate(folio);
542 return true;
543}
544
545static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug)
546{
547 struct swap_info_struct *sis = swp_swap_info(folio->swap);
548 struct swap_iocb *sio = NULL;
549 loff_t pos = swap_dev_pos(folio->swap);
550
551 if (plug)
552 sio = *plug;
553 if (sio) {
554 if (sio->iocb.ki_filp != sis->swap_file ||
555 sio->iocb.ki_pos + sio->len != pos) {
556 swap_read_unplug(sio);
557 sio = NULL;
558 }
559 }
560 if (!sio) {
561 sio = mempool_alloc(sio_pool, GFP_KERNEL);
562 init_sync_kiocb(&sio->iocb, sis->swap_file);
563 sio->iocb.ki_pos = pos;
564 sio->iocb.ki_complete = sio_read_complete;
565 sio->pages = 0;
566 sio->len = 0;
567 }
568 bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
569 sio->len += folio_size(folio);
570 sio->pages += 1;
571 if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) {
572 swap_read_unplug(sio);
573 sio = NULL;
574 }
575 if (plug)
576 *plug = sio;
577}
578
579static void swap_read_folio_bdev_sync(struct folio *folio,
580 struct swap_info_struct *sis)
581{
582 struct bio_vec bv;
583 struct bio bio;
584
585 bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ);
586 bio.bi_iter.bi_sector = swap_folio_sector(folio);
587 bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
588 /*
589 * Keep this task valid during swap readpage because the oom killer may
590 * attempt to access it in the page fault retry time check.
591 */
592 get_task_struct(current);
593 count_mthp_stat(folio_order(folio), MTHP_STAT_SWPIN);
594 count_memcg_folio_events(folio, PSWPIN, folio_nr_pages(folio));
595 count_vm_events(PSWPIN, folio_nr_pages(folio));
596 submit_bio_wait(&bio);
597 __end_swap_bio_read(&bio);
598 put_task_struct(current);
599}
600
601static void swap_read_folio_bdev_async(struct folio *folio,
602 struct swap_info_struct *sis)
603{
604 struct bio *bio;
605
606 bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL);
607 bio->bi_iter.bi_sector = swap_folio_sector(folio);
608 bio->bi_end_io = end_swap_bio_read;
609 bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
610 count_mthp_stat(folio_order(folio), MTHP_STAT_SWPIN);
611 count_memcg_folio_events(folio, PSWPIN, folio_nr_pages(folio));
612 count_vm_events(PSWPIN, folio_nr_pages(folio));
613 submit_bio(bio);
614}
615
616void swap_read_folio(struct folio *folio, struct swap_iocb **plug)
617{
618 struct swap_info_struct *sis = swp_swap_info(folio->swap);
619 bool synchronous = sis->flags & SWP_SYNCHRONOUS_IO;
620 bool workingset = folio_test_workingset(folio);
621 unsigned long pflags;
622 bool in_thrashing;
623
624 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio);
625 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
626 VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);
627
628 /*
629 * Count submission time as memory stall and delay. When the device
630 * is congested, or the submitting cgroup IO-throttled, submission
631 * can be a significant part of overall IO time.
632 */
633 if (workingset) {
634 delayacct_thrashing_start(&in_thrashing);
635 psi_memstall_enter(&pflags);
636 }
637 delayacct_swapin_start();
638
639 if (swap_read_folio_zeromap(folio)) {
640 folio_unlock(folio);
641 goto finish;
642 } else if (zswap_load(folio)) {
643 folio_unlock(folio);
644 goto finish;
645 }
646
647 /* We have to read from slower devices. Increase zswap protection. */
648 zswap_folio_swapin(folio);
649
650 if (data_race(sis->flags & SWP_FS_OPS)) {
651 swap_read_folio_fs(folio, plug);
652 } else if (synchronous) {
653 swap_read_folio_bdev_sync(folio, sis);
654 } else {
655 swap_read_folio_bdev_async(folio, sis);
656 }
657
658finish:
659 if (workingset) {
660 delayacct_thrashing_end(&in_thrashing);
661 psi_memstall_leave(&pflags);
662 }
663 delayacct_swapin_end();
664}
665
666void __swap_read_unplug(struct swap_iocb *sio)
667{
668 struct iov_iter from;
669 struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
670 int ret;
671
672 iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len);
673 ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
674 if (ret != -EIOCBQUEUED)
675 sio_read_complete(&sio->iocb, ret);
676}