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/psi.h>
26 #include <linux/uio.h>
27 #include <linux/sched/task.h>
28
end_swap_bio_write(struct bio * bio)29 void end_swap_bio_write(struct bio *bio)
30 {
31 struct page *page = bio_first_page_all(bio);
32
33 if (bio->bi_status) {
34 SetPageError(page);
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 rotate_reclaimable_page()
42 */
43 set_page_dirty(page);
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 ClearPageReclaim(page);
48 }
49 end_page_writeback(page);
50 bio_put(bio);
51 }
52
swap_slot_free_notify(struct page * page)53 static void swap_slot_free_notify(struct page *page)
54 {
55 struct swap_info_struct *sis;
56 struct gendisk *disk;
57 swp_entry_t entry;
58
59 /*
60 * There is no guarantee that the page is in swap cache - the software
61 * suspend code (at least) uses end_swap_bio_read() against a non-
62 * swapcache page. So we must check PG_swapcache before proceeding with
63 * this optimization.
64 */
65 if (unlikely(!PageSwapCache(page)))
66 return;
67
68 sis = page_swap_info(page);
69 if (data_race(!(sis->flags & SWP_BLKDEV)))
70 return;
71
72 /*
73 * The swap subsystem performs lazy swap slot freeing,
74 * expecting that the page will be swapped out again.
75 * So we can avoid an unnecessary write if the page
76 * isn't redirtied.
77 * This is good for real swap storage because we can
78 * reduce unnecessary I/O and enhance wear-leveling
79 * if an SSD is used as the as swap device.
80 * But if in-memory swap device (eg zram) is used,
81 * this causes a duplicated copy between uncompressed
82 * data in VM-owned memory and compressed data in
83 * zram-owned memory. So let's free zram-owned memory
84 * and make the VM-owned decompressed page *dirty*,
85 * so the page should be swapped out somewhere again if
86 * we again wish to reclaim it.
87 */
88 disk = sis->bdev->bd_disk;
89 entry.val = page_private(page);
90 if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) {
91 unsigned long offset;
92
93 offset = swp_offset(entry);
94
95 SetPageDirty(page);
96 disk->fops->swap_slot_free_notify(sis->bdev,
97 offset);
98 }
99 }
100
end_swap_bio_read(struct bio * bio)101 static void end_swap_bio_read(struct bio *bio)
102 {
103 struct page *page = bio_first_page_all(bio);
104 struct task_struct *waiter = bio->bi_private;
105
106 if (bio->bi_status) {
107 SetPageError(page);
108 ClearPageUptodate(page);
109 pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n",
110 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
111 (unsigned long long)bio->bi_iter.bi_sector);
112 goto out;
113 }
114
115 SetPageUptodate(page);
116 swap_slot_free_notify(page);
117 out:
118 unlock_page(page);
119 WRITE_ONCE(bio->bi_private, NULL);
120 bio_put(bio);
121 if (waiter) {
122 blk_wake_io_task(waiter);
123 put_task_struct(waiter);
124 }
125 }
126
generic_swapfile_activate(struct swap_info_struct * sis,struct file * swap_file,sector_t * span)127 int generic_swapfile_activate(struct swap_info_struct *sis,
128 struct file *swap_file,
129 sector_t *span)
130 {
131 struct address_space *mapping = swap_file->f_mapping;
132 struct inode *inode = mapping->host;
133 unsigned blocks_per_page;
134 unsigned long page_no;
135 unsigned blkbits;
136 sector_t probe_block;
137 sector_t last_block;
138 sector_t lowest_block = -1;
139 sector_t highest_block = 0;
140 int nr_extents = 0;
141 int ret;
142
143 blkbits = inode->i_blkbits;
144 blocks_per_page = PAGE_SIZE >> blkbits;
145
146 /*
147 * Map all the blocks into the extent tree. This code doesn't try
148 * to be very smart.
149 */
150 probe_block = 0;
151 page_no = 0;
152 last_block = i_size_read(inode) >> blkbits;
153 while ((probe_block + blocks_per_page) <= last_block &&
154 page_no < sis->max) {
155 unsigned block_in_page;
156 sector_t first_block;
157
158 cond_resched();
159
160 first_block = probe_block;
161 ret = bmap(inode, &first_block);
162 if (ret || !first_block)
163 goto bad_bmap;
164
165 /*
166 * It must be PAGE_SIZE aligned on-disk
167 */
168 if (first_block & (blocks_per_page - 1)) {
169 probe_block++;
170 goto reprobe;
171 }
172
173 for (block_in_page = 1; block_in_page < blocks_per_page;
174 block_in_page++) {
175 sector_t block;
176
177 block = probe_block + block_in_page;
178 ret = bmap(inode, &block);
179 if (ret || !block)
180 goto bad_bmap;
181
182 if (block != first_block + block_in_page) {
183 /* Discontiguity */
184 probe_block++;
185 goto reprobe;
186 }
187 }
188
189 first_block >>= (PAGE_SHIFT - blkbits);
190 if (page_no) { /* exclude the header page */
191 if (first_block < lowest_block)
192 lowest_block = first_block;
193 if (first_block > highest_block)
194 highest_block = first_block;
195 }
196
197 /*
198 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
199 */
200 ret = add_swap_extent(sis, page_no, 1, first_block);
201 if (ret < 0)
202 goto out;
203 nr_extents += ret;
204 page_no++;
205 probe_block += blocks_per_page;
206 reprobe:
207 continue;
208 }
209 ret = nr_extents;
210 *span = 1 + highest_block - lowest_block;
211 if (page_no == 0)
212 page_no = 1; /* force Empty message */
213 sis->max = page_no;
214 sis->pages = page_no - 1;
215 sis->highest_bit = page_no - 1;
216 out:
217 return ret;
218 bad_bmap:
219 pr_err("swapon: swapfile has holes\n");
220 ret = -EINVAL;
221 goto out;
222 }
223
224 /*
225 * We may have stale swap cache pages in memory: notice
226 * them here and get rid of the unnecessary final write.
227 */
swap_writepage(struct page * page,struct writeback_control * wbc)228 int swap_writepage(struct page *page, struct writeback_control *wbc)
229 {
230 int ret = 0;
231
232 if (try_to_free_swap(page)) {
233 unlock_page(page);
234 goto out;
235 }
236 /*
237 * Arch code may have to preserve more data than just the page
238 * contents, e.g. memory tags.
239 */
240 ret = arch_prepare_to_swap(page);
241 if (ret) {
242 set_page_dirty(page);
243 unlock_page(page);
244 goto out;
245 }
246 if (frontswap_store(page) == 0) {
247 set_page_writeback(page);
248 unlock_page(page);
249 end_page_writeback(page);
250 goto out;
251 }
252 ret = __swap_writepage(page, wbc, end_swap_bio_write);
253 out:
254 return ret;
255 }
256
count_swpout_vm_event(struct page * page)257 static inline void count_swpout_vm_event(struct page *page)
258 {
259 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
260 if (unlikely(PageTransHuge(page)))
261 count_vm_event(THP_SWPOUT);
262 #endif
263 count_vm_events(PSWPOUT, thp_nr_pages(page));
264 }
265
266 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
bio_associate_blkg_from_page(struct bio * bio,struct page * page)267 static void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
268 {
269 struct cgroup_subsys_state *css;
270 struct mem_cgroup *memcg;
271
272 memcg = page_memcg(page);
273 if (!memcg)
274 return;
275
276 rcu_read_lock();
277 css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
278 bio_associate_blkg_from_css(bio, css);
279 rcu_read_unlock();
280 }
281 #else
282 #define bio_associate_blkg_from_page(bio, page) do { } while (0)
283 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
284
__swap_writepage(struct page * page,struct writeback_control * wbc,bio_end_io_t end_write_func)285 int __swap_writepage(struct page *page, struct writeback_control *wbc,
286 bio_end_io_t end_write_func)
287 {
288 struct bio *bio;
289 int ret;
290 struct swap_info_struct *sis = page_swap_info(page);
291
292 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
293 if (data_race(sis->flags & SWP_FS_OPS)) {
294 struct kiocb kiocb;
295 struct file *swap_file = sis->swap_file;
296 struct address_space *mapping = swap_file->f_mapping;
297 struct bio_vec bv = {
298 .bv_page = page,
299 .bv_len = PAGE_SIZE,
300 .bv_offset = 0
301 };
302 struct iov_iter from;
303
304 iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
305 init_sync_kiocb(&kiocb, swap_file);
306 kiocb.ki_pos = page_file_offset(page);
307
308 set_page_writeback(page);
309 unlock_page(page);
310 ret = mapping->a_ops->direct_IO(&kiocb, &from);
311 if (ret == PAGE_SIZE) {
312 count_vm_event(PSWPOUT);
313 ret = 0;
314 } else {
315 /*
316 * In the case of swap-over-nfs, this can be a
317 * temporary failure if the system has limited
318 * memory for allocating transmit buffers.
319 * Mark the page dirty and avoid
320 * rotate_reclaimable_page but rate-limit the
321 * messages but do not flag PageError like
322 * the normal direct-to-bio case as it could
323 * be temporary.
324 */
325 set_page_dirty(page);
326 ClearPageReclaim(page);
327 pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
328 page_file_offset(page));
329 }
330 end_page_writeback(page);
331 return ret;
332 }
333
334 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
335 if (!ret) {
336 count_swpout_vm_event(page);
337 return 0;
338 }
339
340 bio = bio_alloc(GFP_NOIO, 1);
341 bio_set_dev(bio, sis->bdev);
342 bio->bi_iter.bi_sector = swap_page_sector(page);
343 bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc);
344 bio->bi_end_io = end_write_func;
345 bio_add_page(bio, page, thp_size(page), 0);
346
347 bio_associate_blkg_from_page(bio, page);
348 count_swpout_vm_event(page);
349 set_page_writeback(page);
350 unlock_page(page);
351 submit_bio(bio);
352
353 return 0;
354 }
355
swap_readpage(struct page * page,bool synchronous)356 int swap_readpage(struct page *page, bool synchronous)
357 {
358 struct bio *bio;
359 int ret = 0;
360 struct swap_info_struct *sis = page_swap_info(page);
361 blk_qc_t qc;
362 struct gendisk *disk;
363 unsigned long pflags;
364
365 VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
366 VM_BUG_ON_PAGE(!PageLocked(page), page);
367 VM_BUG_ON_PAGE(PageUptodate(page), page);
368
369 /*
370 * Count submission time as memory stall. When the device is congested,
371 * or the submitting cgroup IO-throttled, submission can be a
372 * significant part of overall IO time.
373 */
374 psi_memstall_enter(&pflags);
375
376 if (frontswap_load(page) == 0) {
377 SetPageUptodate(page);
378 unlock_page(page);
379 goto out;
380 }
381
382 if (data_race(sis->flags & SWP_FS_OPS)) {
383 struct file *swap_file = sis->swap_file;
384 struct address_space *mapping = swap_file->f_mapping;
385
386 ret = mapping->a_ops->readpage(swap_file, page);
387 if (!ret)
388 count_vm_event(PSWPIN);
389 goto out;
390 }
391
392 if (sis->flags & SWP_SYNCHRONOUS_IO) {
393 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
394 if (!ret) {
395 if (trylock_page(page)) {
396 swap_slot_free_notify(page);
397 unlock_page(page);
398 }
399
400 count_vm_event(PSWPIN);
401 goto out;
402 }
403 }
404
405 ret = 0;
406 bio = bio_alloc(GFP_KERNEL, 1);
407 bio_set_dev(bio, sis->bdev);
408 bio->bi_opf = REQ_OP_READ;
409 bio->bi_iter.bi_sector = swap_page_sector(page);
410 bio->bi_end_io = end_swap_bio_read;
411 bio_add_page(bio, page, thp_size(page), 0);
412
413 disk = bio->bi_bdev->bd_disk;
414 /*
415 * Keep this task valid during swap readpage because the oom killer may
416 * attempt to access it in the page fault retry time check.
417 */
418 if (synchronous) {
419 bio->bi_opf |= REQ_HIPRI;
420 get_task_struct(current);
421 bio->bi_private = current;
422 }
423 count_vm_event(PSWPIN);
424 bio_get(bio);
425 qc = submit_bio(bio);
426 while (synchronous) {
427 set_current_state(TASK_UNINTERRUPTIBLE);
428 if (!READ_ONCE(bio->bi_private))
429 break;
430
431 if (!blk_poll(disk->queue, qc, true))
432 blk_io_schedule();
433 }
434 __set_current_state(TASK_RUNNING);
435 bio_put(bio);
436
437 out:
438 psi_memstall_leave(&pflags);
439 return ret;
440 }
441
swap_set_page_dirty(struct page * page)442 int swap_set_page_dirty(struct page *page)
443 {
444 struct swap_info_struct *sis = page_swap_info(page);
445
446 if (data_race(sis->flags & SWP_FS_OPS)) {
447 struct address_space *mapping = sis->swap_file->f_mapping;
448
449 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
450 return mapping->a_ops->set_page_dirty(page);
451 } else {
452 return __set_page_dirty_no_writeback(page);
453 }
454 }
455
