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
get_swap_bio(gfp_t gfp_flags,struct page * page,bio_end_io_t end_io)29 static 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, thp_size(page), 0);
44 }
45 return bio;
46 }
47
end_swap_bio_write(struct bio * bio)48 void 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_ratelimited("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
end_swap_bio_read(struct bio * bio)72 static void end_swap_bio_read(struct bio *bio)
73 {
74 struct page *page = bio_first_page_all(bio);
75 struct task_struct *waiter = bio->bi_private;
76
77 if (bio->bi_status) {
78 SetPageError(page);
79 ClearPageUptodate(page);
80 pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n",
81 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
82 (unsigned long long)bio->bi_iter.bi_sector);
83 goto out;
84 }
85
86 SetPageUptodate(page);
87 out:
88 unlock_page(page);
89 WRITE_ONCE(bio->bi_private, NULL);
90 bio_put(bio);
91 if (waiter) {
92 blk_wake_io_task(waiter);
93 put_task_struct(waiter);
94 }
95 }
96
generic_swapfile_activate(struct swap_info_struct * sis,struct file * swap_file,sector_t * span)97 int generic_swapfile_activate(struct swap_info_struct *sis,
98 struct file *swap_file,
99 sector_t *span)
100 {
101 struct address_space *mapping = swap_file->f_mapping;
102 struct inode *inode = mapping->host;
103 unsigned blocks_per_page;
104 unsigned long page_no;
105 unsigned blkbits;
106 sector_t probe_block;
107 sector_t last_block;
108 sector_t lowest_block = -1;
109 sector_t highest_block = 0;
110 int nr_extents = 0;
111 int ret;
112
113 blkbits = inode->i_blkbits;
114 blocks_per_page = PAGE_SIZE >> blkbits;
115
116 /*
117 * Map all the blocks into the extent tree. This code doesn't try
118 * to be very smart.
119 */
120 probe_block = 0;
121 page_no = 0;
122 last_block = i_size_read(inode) >> blkbits;
123 while ((probe_block + blocks_per_page) <= last_block &&
124 page_no < sis->max) {
125 unsigned block_in_page;
126 sector_t first_block;
127
128 cond_resched();
129
130 first_block = probe_block;
131 ret = bmap(inode, &first_block);
132 if (ret || !first_block)
133 goto bad_bmap;
134
135 /*
136 * It must be PAGE_SIZE aligned on-disk
137 */
138 if (first_block & (blocks_per_page - 1)) {
139 probe_block++;
140 goto reprobe;
141 }
142
143 for (block_in_page = 1; block_in_page < blocks_per_page;
144 block_in_page++) {
145 sector_t block;
146
147 block = probe_block + block_in_page;
148 ret = bmap(inode, &block);
149 if (ret || !block)
150 goto bad_bmap;
151
152 if (block != first_block + block_in_page) {
153 /* Discontiguity */
154 probe_block++;
155 goto reprobe;
156 }
157 }
158
159 first_block >>= (PAGE_SHIFT - blkbits);
160 if (page_no) { /* exclude the header page */
161 if (first_block < lowest_block)
162 lowest_block = first_block;
163 if (first_block > highest_block)
164 highest_block = first_block;
165 }
166
167 /*
168 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
169 */
170 ret = add_swap_extent(sis, page_no, 1, first_block);
171 if (ret < 0)
172 goto out;
173 nr_extents += ret;
174 page_no++;
175 probe_block += blocks_per_page;
176 reprobe:
177 continue;
178 }
179 ret = nr_extents;
180 *span = 1 + highest_block - lowest_block;
181 if (page_no == 0)
182 page_no = 1; /* force Empty message */
183 sis->max = page_no;
184 sis->pages = page_no - 1;
185 sis->highest_bit = page_no - 1;
186 out:
187 return ret;
188 bad_bmap:
189 pr_err("swapon: swapfile has holes\n");
190 ret = -EINVAL;
191 goto out;
192 }
193
194 /*
195 * We may have stale swap cache pages in memory: notice
196 * them here and get rid of the unnecessary final write.
197 */
swap_writepage(struct page * page,struct writeback_control * wbc)198 int swap_writepage(struct page *page, struct writeback_control *wbc)
199 {
200 int ret = 0;
201
202 if (try_to_free_swap(page)) {
203 unlock_page(page);
204 goto out;
205 }
206 /*
207 * Arch code may have to preserve more data than just the page
208 * contents, e.g. memory tags.
209 */
210 ret = arch_prepare_to_swap(page);
211 if (ret) {
212 set_page_dirty(page);
213 unlock_page(page);
214 goto out;
215 }
216 if (frontswap_store(page) == 0) {
217 set_page_writeback(page);
218 unlock_page(page);
219 end_page_writeback(page);
220 goto out;
221 }
222 ret = __swap_writepage(page, wbc, end_swap_bio_write);
223 out:
224 return ret;
225 }
226
count_swpout_vm_event(struct page * page)227 static inline void count_swpout_vm_event(struct page *page)
228 {
229 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
230 if (unlikely(PageTransHuge(page)))
231 count_vm_event(THP_SWPOUT);
232 #endif
233 count_vm_events(PSWPOUT, thp_nr_pages(page));
234 }
235
236 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
bio_associate_blkg_from_page(struct bio * bio,struct page * page)237 static void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
238 {
239 struct cgroup_subsys_state *css;
240
241 if (!page->mem_cgroup)
242 return;
243
244 rcu_read_lock();
245 css = cgroup_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys);
246 bio_associate_blkg_from_css(bio, css);
247 rcu_read_unlock();
248 }
249 #else
250 #define bio_associate_blkg_from_page(bio, page) do { } while (0)
251 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
252
__swap_writepage(struct page * page,struct writeback_control * wbc,bio_end_io_t end_write_func)253 int __swap_writepage(struct page *page, struct writeback_control *wbc,
254 bio_end_io_t end_write_func)
255 {
256 struct bio *bio;
257 int ret;
258 struct swap_info_struct *sis = page_swap_info(page);
259
260 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
261 if (data_race(sis->flags & SWP_FS_OPS)) {
262 struct kiocb kiocb;
263 struct file *swap_file = sis->swap_file;
264 struct address_space *mapping = swap_file->f_mapping;
265 struct bio_vec bv = {
266 .bv_page = page,
267 .bv_len = PAGE_SIZE,
268 .bv_offset = 0
269 };
270 struct iov_iter from;
271
272 iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
273 init_sync_kiocb(&kiocb, swap_file);
274 kiocb.ki_pos = page_file_offset(page);
275
276 set_page_writeback(page);
277 unlock_page(page);
278 ret = mapping->a_ops->direct_IO(&kiocb, &from);
279 if (ret == PAGE_SIZE) {
280 count_vm_event(PSWPOUT);
281 ret = 0;
282 } else {
283 /*
284 * In the case of swap-over-nfs, this can be a
285 * temporary failure if the system has limited
286 * memory for allocating transmit buffers.
287 * Mark the page dirty and avoid
288 * rotate_reclaimable_page but rate-limit the
289 * messages but do not flag PageError like
290 * the normal direct-to-bio case as it could
291 * be temporary.
292 */
293 set_page_dirty(page);
294 ClearPageReclaim(page);
295 pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
296 page_file_offset(page));
297 }
298 end_page_writeback(page);
299 return ret;
300 }
301
302 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
303 if (!ret) {
304 count_swpout_vm_event(page);
305 return 0;
306 }
307
308 bio = get_swap_bio(GFP_NOIO, page, end_write_func);
309 if (bio == NULL) {
310 set_page_dirty(page);
311 unlock_page(page);
312 return -ENOMEM;
313 }
314 bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc);
315 bio_associate_blkg_from_page(bio, page);
316 count_swpout_vm_event(page);
317 set_page_writeback(page);
318 unlock_page(page);
319 submit_bio(bio);
320
321 return 0;
322 }
323
swap_readpage(struct page * page,bool synchronous)324 int swap_readpage(struct page *page, bool synchronous)
325 {
326 struct bio *bio;
327 int ret = 0;
328 struct swap_info_struct *sis = page_swap_info(page);
329 blk_qc_t qc;
330 struct gendisk *disk;
331 unsigned long pflags;
332
333 VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
334 VM_BUG_ON_PAGE(!PageLocked(page), page);
335 VM_BUG_ON_PAGE(PageUptodate(page), page);
336
337 /*
338 * Count submission time as memory stall. When the device is congested,
339 * or the submitting cgroup IO-throttled, submission can be a
340 * significant part of overall IO time.
341 */
342 psi_memstall_enter(&pflags);
343
344 if (frontswap_load(page) == 0) {
345 SetPageUptodate(page);
346 unlock_page(page);
347 goto out;
348 }
349
350 if (data_race(sis->flags & SWP_FS_OPS)) {
351 struct file *swap_file = sis->swap_file;
352 struct address_space *mapping = swap_file->f_mapping;
353
354 ret = mapping->a_ops->readpage(swap_file, page);
355 if (!ret)
356 count_vm_event(PSWPIN);
357 goto out;
358 }
359
360 if (sis->flags & SWP_SYNCHRONOUS_IO) {
361 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
362 if (!ret) {
363 count_vm_event(PSWPIN);
364 goto out;
365 }
366 }
367
368 ret = 0;
369 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
370 if (bio == NULL) {
371 unlock_page(page);
372 ret = -ENOMEM;
373 goto out;
374 }
375 disk = bio->bi_disk;
376 /*
377 * Keep this task valid during swap readpage because the oom killer may
378 * attempt to access it in the page fault retry time check.
379 */
380 bio_set_op_attrs(bio, REQ_OP_READ, 0);
381 if (synchronous) {
382 bio->bi_opf |= REQ_HIPRI;
383 get_task_struct(current);
384 bio->bi_private = current;
385 }
386 count_vm_event(PSWPIN);
387 bio_get(bio);
388 qc = submit_bio(bio);
389 while (synchronous) {
390 set_current_state(TASK_UNINTERRUPTIBLE);
391 if (!READ_ONCE(bio->bi_private))
392 break;
393
394 if (!blk_poll(disk->queue, qc, true))
395 blk_io_schedule();
396 }
397 __set_current_state(TASK_RUNNING);
398 bio_put(bio);
399
400 out:
401 psi_memstall_leave(&pflags);
402 return ret;
403 }
404
swap_set_page_dirty(struct page * page)405 int swap_set_page_dirty(struct page *page)
406 {
407 struct swap_info_struct *sis = page_swap_info(page);
408
409 if (data_race(sis->flags & SWP_FS_OPS)) {
410 struct address_space *mapping = sis->swap_file->f_mapping;
411
412 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
413 return mapping->a_ops->set_page_dirty(page);
414 } else {
415 return __set_page_dirty_no_writeback(page);
416 }
417 }
418