xref: /openbmc/linux/mm/page_io.c (revision 8e7a49e0) 
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 static void __end_swap_bio_write(struct bio *bio)
31 {
32 	struct page *page = bio_first_page_all(bio);
33 
34 	if (bio->bi_status) {
35 		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 		set_page_dirty(page);
45 		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 	end_page_writeback(page);
51 }
52 
53 static void end_swap_bio_write(struct bio *bio)
54 {
55 	__end_swap_bio_write(bio);
56 	bio_put(bio);
57 }
58 
59 static void __end_swap_bio_read(struct bio *bio)
60 {
61 	struct page *page = bio_first_page_all(bio);
62 
63 	if (bio->bi_status) {
64 		SetPageError(page);
65 		ClearPageUptodate(page);
66 		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 	unlock_page(page);
73 }
74 
75 static void end_swap_bio_read(struct bio *bio)
76 {
77 	__end_swap_bio_read(bio);
78 	bio_put(bio);
79 }
80 
81 int generic_swapfile_activate(struct swap_info_struct *sis,
82 				struct file *swap_file,
83 				sector_t *span)
84 {
85 	struct address_space *mapping = swap_file->f_mapping;
86 	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 	sector_t lowest_block = -1;
93 	sector_t highest_block = 0;
94 	int nr_extents = 0;
95 	int ret;
96 
97 	blkbits = inode->i_blkbits;
98 	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 	probe_block = 0;
105 	page_no = 0;
106 	last_block = i_size_read(inode) >> blkbits;
107 	while ((probe_block + blocks_per_page) <= last_block &&
108 			page_no < sis->max) {
109 		unsigned block_in_page;
110 		sector_t first_block;
111 
112 		cond_resched();
113 
114 		first_block = probe_block;
115 		ret = bmap(inode, &first_block);
116 		if (ret || !first_block)
117 			goto bad_bmap;
118 
119 		/*
120 		 * It must be PAGE_SIZE aligned on-disk
121 		 */
122 		if (first_block & (blocks_per_page - 1)) {
123 			probe_block++;
124 			goto reprobe;
125 		}
126 
127 		for (block_in_page = 1; block_in_page < blocks_per_page;
128 					block_in_page++) {
129 			sector_t block;
130 
131 			block = probe_block + block_in_page;
132 			ret = bmap(inode, &block);
133 			if (ret || !block)
134 				goto bad_bmap;
135 
136 			if (block != first_block + block_in_page) {
137 				/* Discontiguity */
138 				probe_block++;
139 				goto reprobe;
140 			}
141 		}
142 
143 		first_block >>= (PAGE_SHIFT - blkbits);
144 		if (page_no) {	/* exclude the header page */
145 			if (first_block < lowest_block)
146 				lowest_block = first_block;
147 			if (first_block > highest_block)
148 				highest_block = first_block;
149 		}
150 
151 		/*
152 		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
153 		 */
154 		ret = add_swap_extent(sis, page_no, 1, first_block);
155 		if (ret < 0)
156 			goto out;
157 		nr_extents += ret;
158 		page_no++;
159 		probe_block += blocks_per_page;
160 reprobe:
161 		continue;
162 	}
163 	ret = nr_extents;
164 	*span = 1 + highest_block - lowest_block;
165 	if (page_no == 0)
166 		page_no = 1;	/* force Empty message */
167 	sis->max = page_no;
168 	sis->pages = page_no - 1;
169 	sis->highest_bit = page_no - 1;
170 out:
171 	return ret;
172 bad_bmap:
173 	pr_err("swapon: swapfile has holes\n");
174 	ret = -EINVAL;
175 	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 int swap_writepage(struct page *page, struct writeback_control *wbc)
183 {
184 	struct folio *folio = page_folio(page);
185 	int ret;
186 
187 	if (folio_free_swap(folio)) {
188 		folio_unlock(folio);
189 		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 	ret = arch_prepare_to_swap(&folio->page);
196 	if (ret) {
197 		folio_mark_dirty(folio);
198 		folio_unlock(folio);
199 		return ret;
200 	}
201 	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 	__swap_writepage(&folio->page, wbc);
208 	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 	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 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 
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 
295 static void 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 	bvec_set_page(&sio->bvec[sio->pages], page, thp_size(page), 0);
322 	sio->len += thp_size(page);
323 	sio->pages += 1;
324 	if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) {
325 		swap_write_unplug(sio);
326 		sio = NULL;
327 	}
328 	if (wbc->swap_plug)
329 		*wbc->swap_plug = sio;
330 }
331 
332 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 	bio_init(&bio, sis->bdev, &bv, 1,
339 		 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc));
340 	bio.bi_iter.bi_sector = swap_page_sector(page);
341 	bio_add_page(&bio, page, thp_size(page), 0);
342 
343 	bio_associate_blkg_from_page(&bio, page);
344 	count_swpout_vm_event(page);
345 
346 	set_page_writeback(page);
347 	unlock_page(page);
348 
349 	submit_bio_wait(&bio);
350 	__end_swap_bio_write(&bio);
351 }
352 
353 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 	bio = bio_alloc(sis->bdev, 1,
359 			REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
360 			GFP_NOIO);
361 	bio->bi_iter.bi_sector = swap_page_sector(page);
362 	bio->bi_end_io = end_swap_bio_write;
363 	bio_add_page(bio, page, thp_size(page), 0);
364 
365 	bio_associate_blkg_from_page(bio, page);
366 	count_swpout_vm_event(page);
367 	set_page_writeback(page);
368 	unlock_page(page);
369 	submit_bio(bio);
370 }
371 
372 void __swap_writepage(struct page *page, struct writeback_control *wbc)
373 {
374 	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 	if (data_race(sis->flags & SWP_FS_OPS))
383 		swap_writepage_fs(page, wbc);
384 	else if (sis->flags & SWP_SYNCHRONOUS_IO)
385 		swap_writepage_bdev_sync(page, wbc, sis);
386 	else
387 		swap_writepage_bdev_async(page, wbc, sis);
388 }
389 
390 void swap_write_unplug(struct swap_iocb *sio)
391 {
392 	struct iov_iter from;
393 	struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
394 	int ret;
395 
396 	iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len);
397 	ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
398 	if (ret != -EIOCBQUEUED)
399 		sio_write_complete(&sio->iocb, ret);
400 }
401 
402 static void sio_read_complete(struct kiocb *iocb, long ret)
403 {
404 	struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
405 	int p;
406 
407 	if (ret == sio->len) {
408 		for (p = 0; p < sio->pages; p++) {
409 			struct page *page = sio->bvec[p].bv_page;
410 
411 			SetPageUptodate(page);
412 			unlock_page(page);
413 		}
414 		count_vm_events(PSWPIN, sio->pages);
415 	} else {
416 		for (p = 0; p < sio->pages; p++) {
417 			struct page *page = sio->bvec[p].bv_page;
418 
419 			SetPageError(page);
420 			ClearPageUptodate(page);
421 			unlock_page(page);
422 		}
423 		pr_alert_ratelimited("Read-error on swap-device\n");
424 	}
425 	mempool_free(sio, sio_pool);
426 }
427 
428 static void swap_readpage_fs(struct page *page,
429 			     struct swap_iocb **plug)
430 {
431 	struct swap_info_struct *sis = page_swap_info(page);
432 	struct swap_iocb *sio = NULL;
433 	loff_t pos = page_file_offset(page);
434 
435 	if (plug)
436 		sio = *plug;
437 	if (sio) {
438 		if (sio->iocb.ki_filp != sis->swap_file ||
439 		    sio->iocb.ki_pos + sio->len != pos) {
440 			swap_read_unplug(sio);
441 			sio = NULL;
442 		}
443 	}
444 	if (!sio) {
445 		sio = mempool_alloc(sio_pool, GFP_KERNEL);
446 		init_sync_kiocb(&sio->iocb, sis->swap_file);
447 		sio->iocb.ki_pos = pos;
448 		sio->iocb.ki_complete = sio_read_complete;
449 		sio->pages = 0;
450 		sio->len = 0;
451 	}
452 	bvec_set_page(&sio->bvec[sio->pages], page, thp_size(page), 0);
453 	sio->len += thp_size(page);
454 	sio->pages += 1;
455 	if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) {
456 		swap_read_unplug(sio);
457 		sio = NULL;
458 	}
459 	if (plug)
460 		*plug = sio;
461 }
462 
463 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 	bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ);
470 	bio.bi_iter.bi_sector = swap_page_sector(page);
471 	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 	get_task_struct(current);
477 	count_vm_event(PSWPIN);
478 	submit_bio_wait(&bio);
479 	__end_swap_bio_read(&bio);
480 	put_task_struct(current);
481 }
482 
483 static void swap_readpage_bdev_async(struct page *page,
484 		struct swap_info_struct *sis)
485 {
486 	struct bio *bio;
487 
488 	bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL);
489 	bio->bi_iter.bi_sector = swap_page_sector(page);
490 	bio->bi_end_io = end_swap_bio_read;
491 	bio_add_page(bio, page, thp_size(page), 0);
492 	count_vm_event(PSWPIN);
493 	submit_bio(bio);
494 }
495 
496 void swap_readpage(struct page *page, bool synchronous, struct swap_iocb **plug)
497 {
498 	struct swap_info_struct *sis = page_swap_info(page);
499 	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 	if (frontswap_load(page) == 0) {
519 		SetPageUptodate(page);
520 		unlock_page(page);
521 	} else if (data_race(sis->flags & SWP_FS_OPS)) {
522 		swap_readpage_fs(page, plug);
523 	} else if (synchronous || (sis->flags & SWP_SYNCHRONOUS_IO)) {
524 		swap_readpage_bdev_sync(page, sis);
525 	} else {
526 		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 }
535 
536 void __swap_read_unplug(struct swap_iocb *sio)
537 {
538 	struct iov_iter from;
539 	struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
540 	int ret;
541 
542 	iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len);
543 	ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
544 	if (ret != -EIOCBQUEUED)
545 		sio_read_complete(&sio->iocb, ret);
546 }
547