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