1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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
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>
30 static void __end_swap_bio_write(struct bio *bio)
32 struct folio *folio = bio_first_folio_all(bio);
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)
41 * Also clear PG_reclaim to avoid folio_rotate_reclaimable()
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);
49 folio_end_writeback(folio);
52 static void end_swap_bio_write(struct bio *bio)
54 __end_swap_bio_write(bio);
58 static void __end_swap_bio_read(struct bio *bio)
60 struct folio *folio = bio_first_folio_all(bio);
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);
67 folio_mark_uptodate(folio);
72 static void end_swap_bio_read(struct bio *bio)
74 __end_swap_bio_read(bio);
78 int generic_swapfile_activate(struct swap_info_struct *sis,
79 struct file *swap_file,
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;
89 sector_t lowest_block = -1;
90 sector_t highest_block = 0;
94 blkbits = inode->i_blkbits;
95 blocks_per_page = PAGE_SIZE >> blkbits;
98 * Map all the blocks into the extent tree. This code doesn't try
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;
111 first_block = probe_block;
112 ret = bmap(inode, &first_block);
113 if (ret || !first_block)
117 * It must be PAGE_SIZE aligned on-disk
119 if (first_block & (blocks_per_page - 1)) {
124 for (block_in_page = 1; block_in_page < blocks_per_page;
128 block = probe_block + block_in_page;
129 ret = bmap(inode, &block);
133 if (block != first_block + block_in_page) {
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;
149 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
151 ret = add_swap_extent(sis, page_no, 1, first_block);
156 probe_block += blocks_per_page;
161 *span = 1 + highest_block - lowest_block;
163 page_no = 1; /* force Empty message */
165 sis->pages = page_no - 1;
166 sis->highest_bit = page_no - 1;
170 pr_err("swapon: swapfile has holes\n");
176 * We may have stale swap cache pages in memory: notice
177 * them here and get rid of the unnecessary final write.
179 int swap_writepage(struct page *page, struct writeback_control *wbc)
181 struct folio *folio = page_folio(page);
184 if (folio_free_swap(folio)) {
189 * Arch code may have to preserve more data than just the page
190 * contents, e.g. memory tags.
192 ret = arch_prepare_to_swap(&folio->page);
194 folio_mark_dirty(folio);
198 if (zswap_store(folio)) {
199 folio_start_writeback(folio);
201 folio_end_writeback(folio);
204 if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) {
205 folio_mark_dirty(folio);
206 return AOP_WRITEPAGE_ACTIVATE;
209 __swap_writepage(folio, wbc);
213 static inline void count_swpout_vm_event(struct folio *folio)
215 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
216 if (unlikely(folio_test_pmd_mappable(folio))) {
217 count_memcg_folio_events(folio, THP_SWPOUT, 1);
218 count_vm_event(THP_SWPOUT);
221 count_vm_events(PSWPOUT, folio_nr_pages(folio));
224 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
225 static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)
227 struct cgroup_subsys_state *css;
228 struct mem_cgroup *memcg;
230 memcg = folio_memcg(folio);
235 css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
236 bio_associate_blkg_from_css(bio, css);
240 #define bio_associate_blkg_from_page(bio, folio) do { } while (0)
241 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
245 struct bio_vec bvec[SWAP_CLUSTER_MAX];
249 static mempool_t *sio_pool;
251 int sio_pool_init(void)
254 mempool_t *pool = mempool_create_kmalloc_pool(
255 SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
256 if (cmpxchg(&sio_pool, NULL, pool))
257 mempool_destroy(pool);
264 static void sio_write_complete(struct kiocb *iocb, long ret)
266 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
267 struct page *page = sio->bvec[0].bv_page;
270 if (ret != sio->len) {
272 * In the case of swap-over-nfs, this can be a
273 * temporary failure if the system has limited
274 * memory for allocating transmit buffers.
275 * Mark the page dirty and avoid
276 * folio_rotate_reclaimable but rate-limit the
277 * messages but do not flag PageError like
278 * the normal direct-to-bio case as it could
281 pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
282 ret, page_file_offset(page));
283 for (p = 0; p < sio->pages; p++) {
284 page = sio->bvec[p].bv_page;
285 set_page_dirty(page);
286 ClearPageReclaim(page);
290 for (p = 0; p < sio->pages; p++)
291 end_page_writeback(sio->bvec[p].bv_page);
293 mempool_free(sio, sio_pool);
296 static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc)
298 struct swap_iocb *sio = NULL;
299 struct swap_info_struct *sis = swp_swap_info(folio->swap);
300 struct file *swap_file = sis->swap_file;
301 loff_t pos = folio_file_pos(folio);
303 count_swpout_vm_event(folio);
304 folio_start_writeback(folio);
307 sio = *wbc->swap_plug;
309 if (sio->iocb.ki_filp != swap_file ||
310 sio->iocb.ki_pos + sio->len != pos) {
311 swap_write_unplug(sio);
316 sio = mempool_alloc(sio_pool, GFP_NOIO);
317 init_sync_kiocb(&sio->iocb, swap_file);
318 sio->iocb.ki_complete = sio_write_complete;
319 sio->iocb.ki_pos = pos;
323 bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
324 sio->len += folio_size(folio);
326 if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) {
327 swap_write_unplug(sio);
331 *wbc->swap_plug = sio;
334 static void swap_writepage_bdev_sync(struct folio *folio,
335 struct writeback_control *wbc, struct swap_info_struct *sis)
340 bio_init(&bio, sis->bdev, &bv, 1,
341 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc));
342 bio.bi_iter.bi_sector = swap_folio_sector(folio);
343 bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
345 bio_associate_blkg_from_page(&bio, folio);
346 count_swpout_vm_event(folio);
348 folio_start_writeback(folio);
351 submit_bio_wait(&bio);
352 __end_swap_bio_write(&bio);
355 static void swap_writepage_bdev_async(struct folio *folio,
356 struct writeback_control *wbc, struct swap_info_struct *sis)
360 bio = bio_alloc(sis->bdev, 1,
361 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
363 bio->bi_iter.bi_sector = swap_folio_sector(folio);
364 bio->bi_end_io = end_swap_bio_write;
365 bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
367 bio_associate_blkg_from_page(bio, folio);
368 count_swpout_vm_event(folio);
369 folio_start_writeback(folio);
374 void __swap_writepage(struct folio *folio, struct writeback_control *wbc)
376 struct swap_info_struct *sis = swp_swap_info(folio->swap);
378 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
380 * ->flags can be updated non-atomicially (scan_swap_map_slots),
381 * but that will never affect SWP_FS_OPS, so the data_race
384 if (data_race(sis->flags & SWP_FS_OPS))
385 swap_writepage_fs(folio, wbc);
386 else if (sis->flags & SWP_SYNCHRONOUS_IO)
387 swap_writepage_bdev_sync(folio, wbc, sis);
389 swap_writepage_bdev_async(folio, wbc, sis);
392 void swap_write_unplug(struct swap_iocb *sio)
394 struct iov_iter from;
395 struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
398 iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len);
399 ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
400 if (ret != -EIOCBQUEUED)
401 sio_write_complete(&sio->iocb, ret);
404 static void sio_read_complete(struct kiocb *iocb, long ret)
406 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
409 if (ret == sio->len) {
410 for (p = 0; p < sio->pages; p++) {
411 struct folio *folio = page_folio(sio->bvec[p].bv_page);
413 folio_mark_uptodate(folio);
416 count_vm_events(PSWPIN, sio->pages);
418 for (p = 0; p < sio->pages; p++) {
419 struct folio *folio = page_folio(sio->bvec[p].bv_page);
423 pr_alert_ratelimited("Read-error on swap-device\n");
425 mempool_free(sio, sio_pool);
428 static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug)
430 struct swap_info_struct *sis = swp_swap_info(folio->swap);
431 struct swap_iocb *sio = NULL;
432 loff_t pos = folio_file_pos(folio);
437 if (sio->iocb.ki_filp != sis->swap_file ||
438 sio->iocb.ki_pos + sio->len != pos) {
439 swap_read_unplug(sio);
444 sio = mempool_alloc(sio_pool, GFP_KERNEL);
445 init_sync_kiocb(&sio->iocb, sis->swap_file);
446 sio->iocb.ki_pos = pos;
447 sio->iocb.ki_complete = sio_read_complete;
451 bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
452 sio->len += folio_size(folio);
454 if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) {
455 swap_read_unplug(sio);
462 static void swap_read_folio_bdev_sync(struct folio *folio,
463 struct swap_info_struct *sis)
468 bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ);
469 bio.bi_iter.bi_sector = swap_folio_sector(folio);
470 bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
472 * Keep this task valid during swap readpage because the oom killer may
473 * attempt to access it in the page fault retry time check.
475 get_task_struct(current);
476 count_vm_event(PSWPIN);
477 submit_bio_wait(&bio);
478 __end_swap_bio_read(&bio);
479 put_task_struct(current);
482 static void swap_read_folio_bdev_async(struct folio *folio,
483 struct swap_info_struct *sis)
487 bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL);
488 bio->bi_iter.bi_sector = swap_folio_sector(folio);
489 bio->bi_end_io = end_swap_bio_read;
490 bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
491 count_vm_event(PSWPIN);
495 void swap_read_folio(struct folio *folio, bool synchronous,
496 struct swap_iocb **plug)
498 struct swap_info_struct *sis = swp_swap_info(folio->swap);
499 bool workingset = folio_test_workingset(folio);
500 unsigned long pflags;
503 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio);
504 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
505 VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);
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.
513 delayacct_thrashing_start(&in_thrashing);
514 psi_memstall_enter(&pflags);
516 delayacct_swapin_start();
518 if (zswap_load(folio)) {
519 folio_mark_uptodate(folio);
521 } else if (data_race(sis->flags & SWP_FS_OPS)) {
522 swap_read_folio_fs(folio, plug);
523 } else if (synchronous || (sis->flags & SWP_SYNCHRONOUS_IO)) {
524 swap_read_folio_bdev_sync(folio, sis);
526 swap_read_folio_bdev_async(folio, sis);
530 delayacct_thrashing_end(&in_thrashing);
531 psi_memstall_leave(&pflags);
533 delayacct_swapin_end();
536 void __swap_read_unplug(struct swap_iocb *sio)
538 struct iov_iter from;
539 struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
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);