mm/page_io.c

   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/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>
  28 #include "swap.h"
  29
  30 static void __end_swap_bio_write(struct bio *bio)
  31 {
  32         struct folio *folio = bio_first_folio_all(bio);
  33
  34         if (bio->bi_status) {
  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 folio_rotate_reclaimable()
  42                  */
  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);
  48         }
  49         folio_end_writeback(folio);
  50 }
  51
  52 static void end_swap_bio_write(struct bio *bio)
  53 {
  54         __end_swap_bio_write(bio);
  55         bio_put(bio);
  56 }
  57
  58 static void __end_swap_bio_read(struct bio *bio)
  59 {
  60         struct folio *folio = bio_first_folio_all(bio);
  61
  62         if (bio->bi_status) {
  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         } else {
  67                 folio_mark_uptodate(folio);
  68         }
  69         folio_unlock(folio);
  70 }
  71
  72 static void end_swap_bio_read(struct bio *bio)
  73 {
  74         __end_swap_bio_read(bio);
  75         bio_put(bio);
  76 }
  77
  78 int generic_swapfile_activate(struct swap_info_struct *sis,
  79                                 struct file *swap_file,
  80                                 sector_t *span)
  81 {
  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;
  86         unsigned blkbits;
  87         sector_t probe_block;
  88         sector_t last_block;
  89         sector_t lowest_block = -1;
  90         sector_t highest_block = 0;
  91         int nr_extents = 0;
  92         int ret;
  93
  94         blkbits = inode->i_blkbits;
  95         blocks_per_page = PAGE_SIZE >> blkbits;
  96
  97         /*
  98          * Map all the blocks into the extent tree.  This code doesn't try
  99          * to be very smart.
 100          */
 101         probe_block = 0;
 102         page_no = 0;
 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;
 108
 109                 cond_resched();
 110
 111                 first_block = probe_block;
 112                 ret = bmap(inode, &first_block);
 113                 if (ret || !first_block)
 114                         goto bad_bmap;
 115
 116                 /*
 117                  * It must be PAGE_SIZE aligned on-disk
 118                  */
 119                 if (first_block & (blocks_per_page - 1)) {
 120                         probe_block++;
 121                         goto reprobe;
 122                 }
 123
 124                 for (block_in_page = 1; block_in_page < blocks_per_page;
 125                                         block_in_page++) {
 126                         sector_t block;
 127
 128                         block = probe_block + block_in_page;
 129                         ret = bmap(inode, &block);
 130                         if (ret || !block)
 131                                 goto bad_bmap;
 132
 133                         if (block != first_block + block_in_page) {
 134                                 /* Discontiguity */
 135                                 probe_block++;
 136                                 goto reprobe;
 137                         }
 138                 }
 139
 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;
 146                 }
 147
 148                 /*
 149                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
 150                  */
 151                 ret = add_swap_extent(sis, page_no, 1, first_block);
 152                 if (ret < 0)
 153                         goto out;
 154                 nr_extents += ret;
 155                 page_no++;
 156                 probe_block += blocks_per_page;
 157 reprobe:
 158                 continue;
 159         }
 160         ret = nr_extents;
 161         *span = 1 + highest_block - lowest_block;
 162         if (page_no == 0)
 163                 page_no = 1;    /* force Empty message */
 164         sis->max = page_no;
 165         sis->pages = page_no - 1;
 166         sis->highest_bit = page_no - 1;
 167 out:
 168         return ret;
 169 bad_bmap:
 170         pr_err("swapon: swapfile has holes\n");
 171         ret = -EINVAL;
 172         goto out;
 173 }
 174
 175 /*
 176  * We may have stale swap cache pages in memory: notice
 177  * them here and get rid of the unnecessary final write.
 178  */
 179 int swap_writepage(struct page *page, struct writeback_control *wbc)
 180 {
 181         struct folio *folio = page_folio(page);
 182         int ret;
 183
 184         if (folio_free_swap(folio)) {
 185                 folio_unlock(folio);
 186                 return 0;
 187         }
 188         /*
 189          * Arch code may have to preserve more data than just the page
 190          * contents, e.g. memory tags.
 191          */
 192         ret = arch_prepare_to_swap(folio);
 193         if (ret) {
 194                 folio_mark_dirty(folio);
 195                 folio_unlock(folio);
 196                 return ret;
 197         }
 198         if (zswap_store(folio)) {
 199                 folio_unlock(folio);
 200                 return 0;
 201         }
 202         if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) {
 203                 folio_mark_dirty(folio);
 204                 return AOP_WRITEPAGE_ACTIVATE;
 205         }
 206
 207         __swap_writepage(folio, wbc);
 208         return 0;
 209 }
 210
 211 static inline void count_swpout_vm_event(struct folio *folio)
 212 {
 213 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 214         if (unlikely(folio_test_pmd_mappable(folio))) {
 215                 count_memcg_folio_events(folio, THP_SWPOUT, 1);
 216                 count_vm_event(THP_SWPOUT);
 217         }
 218         count_mthp_stat(folio_order(folio), MTHP_STAT_SWPOUT);
 219 #endif
 220         count_vm_events(PSWPOUT, folio_nr_pages(folio));
 221 }
 222
 223 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
 224 static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)
 225 {
 226         struct cgroup_subsys_state *css;
 227         struct mem_cgroup *memcg;
 228
 229         memcg = folio_memcg(folio);
 230         if (!memcg)
 231                 return;
 232
 233         rcu_read_lock();
 234         css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
 235         bio_associate_blkg_from_css(bio, css);
 236         rcu_read_unlock();
 237 }
 238 #else
 239 #define bio_associate_blkg_from_page(bio, folio)                do { } while (0)
 240 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
 241
 242 struct swap_iocb {
 243         struct kiocb            iocb;
 244         struct bio_vec          bvec[SWAP_CLUSTER_MAX];
 245         int                     pages;
 246         int                     len;
 247 };
 248 static mempool_t *sio_pool;
 249
 250 int sio_pool_init(void)
 251 {
 252         if (!sio_pool) {
 253                 mempool_t *pool = mempool_create_kmalloc_pool(
 254                         SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
 255                 if (cmpxchg(&sio_pool, NULL, pool))
 256                         mempool_destroy(pool);
 257         }
 258         if (!sio_pool)
 259                 return -ENOMEM;
 260         return 0;
 261 }
 262
 263 static void sio_write_complete(struct kiocb *iocb, long ret)
 264 {
 265         struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
 266         struct page *page = sio->bvec[0].bv_page;
 267         int p;
 268
 269         if (ret != sio->len) {
 270                 /*
 271                  * In the case of swap-over-nfs, this can be a
 272                  * temporary failure if the system has limited
 273                  * memory for allocating transmit buffers.
 274                  * Mark the page dirty and avoid
 275                  * folio_rotate_reclaimable but rate-limit the
 276                  * messages but do not flag PageError like
 277                  * the normal direct-to-bio case as it could
 278                  * be temporary.
 279                  */
 280                 pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
 281                                    ret, swap_dev_pos(page_swap_entry(page)));
 282                 for (p = 0; p < sio->pages; p++) {
 283                         page = sio->bvec[p].bv_page;
 284                         set_page_dirty(page);
 285                         ClearPageReclaim(page);
 286                 }
 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 folio *folio, struct writeback_control *wbc)
 296 {
 297         struct swap_iocb *sio = NULL;
 298         struct swap_info_struct *sis = swp_swap_info(folio->swap);
 299         struct file *swap_file = sis->swap_file;
 300         loff_t pos = swap_dev_pos(folio->swap);
 301
 302         count_swpout_vm_event(folio);
 303         folio_start_writeback(folio);
 304         folio_unlock(folio);
 305         if (wbc->swap_plug)
 306                 sio = *wbc->swap_plug;
 307         if (sio) {
 308                 if (sio->iocb.ki_filp != swap_file ||
 309                     sio->iocb.ki_pos + sio->len != pos) {
 310                         swap_write_unplug(sio);
 311                         sio = NULL;
 312                 }
 313         }
 314         if (!sio) {
 315                 sio = mempool_alloc(sio_pool, GFP_NOIO);
 316                 init_sync_kiocb(&sio->iocb, swap_file);
 317                 sio->iocb.ki_complete = sio_write_complete;
 318                 sio->iocb.ki_pos = pos;
 319                 sio->pages = 0;
 320                 sio->len = 0;
 321         }
 322         bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
 323         sio->len += folio_size(folio);
 324         sio->pages += 1;
 325         if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) {
 326                 swap_write_unplug(sio);
 327                 sio = NULL;
 328         }
 329         if (wbc->swap_plug)
 330                 *wbc->swap_plug = sio;
 331 }
 332
 333 static void swap_writepage_bdev_sync(struct folio *folio,
 334                 struct writeback_control *wbc, struct swap_info_struct *sis)
 335 {
 336         struct bio_vec bv;
 337         struct bio bio;
 338
 339         bio_init(&bio, sis->bdev, &bv, 1,
 340                  REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc));
 341         bio.bi_iter.bi_sector = swap_folio_sector(folio);
 342         bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
 343
 344         bio_associate_blkg_from_page(&bio, folio);
 345         count_swpout_vm_event(folio);
 346
 347         folio_start_writeback(folio);
 348         folio_unlock(folio);
 349
 350         submit_bio_wait(&bio);
 351         __end_swap_bio_write(&bio);
 352 }
 353
 354 static void swap_writepage_bdev_async(struct folio *folio,
 355                 struct writeback_control *wbc, struct swap_info_struct *sis)
 356 {
 357         struct bio *bio;
 358
 359         bio = bio_alloc(sis->bdev, 1,
 360                         REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
 361                         GFP_NOIO);
 362         bio->bi_iter.bi_sector = swap_folio_sector(folio);
 363         bio->bi_end_io = end_swap_bio_write;
 364         bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
 365
 366         bio_associate_blkg_from_page(bio, folio);
 367         count_swpout_vm_event(folio);
 368         folio_start_writeback(folio);
 369         folio_unlock(folio);
 370         submit_bio(bio);
 371 }
 372
 373 void __swap_writepage(struct folio *folio, struct writeback_control *wbc)
 374 {
 375         struct swap_info_struct *sis = swp_swap_info(folio->swap);
 376
 377         VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
 378         /*
 379          * ->flags can be updated non-atomicially (scan_swap_map_slots),
 380          * but that will never affect SWP_FS_OPS, so the data_race
 381          * is safe.
 382          */
 383         if (data_race(sis->flags & SWP_FS_OPS))
 384                 swap_writepage_fs(folio, wbc);
 385         /*
 386          * ->flags can be updated non-atomicially (scan_swap_map_slots),
 387          * but that will never affect SWP_SYNCHRONOUS_IO, so the data_race
 388          * is safe.
 389          */
 390         else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO))
 391                 swap_writepage_bdev_sync(folio, wbc, sis);
 392         else
 393                 swap_writepage_bdev_async(folio, wbc, sis);
 394 }
 395
 396 void swap_write_unplug(struct swap_iocb *sio)
 397 {
 398         struct iov_iter from;
 399         struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
 400         int ret;
 401
 402         iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len);
 403         ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
 404         if (ret != -EIOCBQUEUED)
 405                 sio_write_complete(&sio->iocb, ret);
 406 }
 407
 408 static void sio_read_complete(struct kiocb *iocb, long ret)
 409 {
 410         struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
 411         int p;
 412
 413         if (ret == sio->len) {
 414                 for (p = 0; p < sio->pages; p++) {
 415                         struct folio *folio = page_folio(sio->bvec[p].bv_page);
 416
 417                         folio_mark_uptodate(folio);
 418                         folio_unlock(folio);
 419                 }
 420                 count_vm_events(PSWPIN, sio->pages);
 421         } else {
 422                 for (p = 0; p < sio->pages; p++) {
 423                         struct folio *folio = page_folio(sio->bvec[p].bv_page);
 424
 425                         folio_unlock(folio);
 426                 }
 427                 pr_alert_ratelimited("Read-error on swap-device\n");
 428         }
 429         mempool_free(sio, sio_pool);
 430 }
 431
 432 static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug)
 433 {
 434         struct swap_info_struct *sis = swp_swap_info(folio->swap);
 435         struct swap_iocb *sio = NULL;
 436         loff_t pos = swap_dev_pos(folio->swap);
 437
 438         if (plug)
 439                 sio = *plug;
 440         if (sio) {
 441                 if (sio->iocb.ki_filp != sis->swap_file ||
 442                     sio->iocb.ki_pos + sio->len != pos) {
 443                         swap_read_unplug(sio);
 444                         sio = NULL;
 445                 }
 446         }
 447         if (!sio) {
 448                 sio = mempool_alloc(sio_pool, GFP_KERNEL);
 449                 init_sync_kiocb(&sio->iocb, sis->swap_file);
 450                 sio->iocb.ki_pos = pos;
 451                 sio->iocb.ki_complete = sio_read_complete;
 452                 sio->pages = 0;
 453                 sio->len = 0;
 454         }
 455         bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
 456         sio->len += folio_size(folio);
 457         sio->pages += 1;
 458         if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) {
 459                 swap_read_unplug(sio);
 460                 sio = NULL;
 461         }
 462         if (plug)
 463                 *plug = sio;
 464 }
 465
 466 static void swap_read_folio_bdev_sync(struct folio *folio,
 467                 struct swap_info_struct *sis)
 468 {
 469         struct bio_vec bv;
 470         struct bio bio;
 471
 472         bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ);
 473         bio.bi_iter.bi_sector = swap_folio_sector(folio);
 474         bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
 475         /*
 476          * Keep this task valid during swap readpage because the oom killer may
 477          * attempt to access it in the page fault retry time check.
 478          */
 479         get_task_struct(current);
 480         count_vm_event(PSWPIN);
 481         submit_bio_wait(&bio);
 482         __end_swap_bio_read(&bio);
 483         put_task_struct(current);
 484 }
 485
 486 static void swap_read_folio_bdev_async(struct folio *folio,
 487                 struct swap_info_struct *sis)
 488 {
 489         struct bio *bio;
 490
 491         bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL);
 492         bio->bi_iter.bi_sector = swap_folio_sector(folio);
 493         bio->bi_end_io = end_swap_bio_read;
 494         bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
 495         count_vm_event(PSWPIN);
 496         submit_bio(bio);
 497 }
 498
 499 void swap_read_folio(struct folio *folio, struct swap_iocb **plug)
 500 {
 501         struct swap_info_struct *sis = swp_swap_info(folio->swap);
 502         bool synchronous = sis->flags & SWP_SYNCHRONOUS_IO;
 503         bool workingset = folio_test_workingset(folio);
 504         unsigned long pflags;
 505         bool in_thrashing;
 506
 507         VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio);
 508         VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 509         VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);
 510
 511         /*
 512          * Count submission time as memory stall and delay. When the device
 513          * is congested, or the submitting cgroup IO-throttled, submission
 514          * can be a significant part of overall IO time.
 515          */
 516         if (workingset) {
 517                 delayacct_thrashing_start(&in_thrashing);
 518                 psi_memstall_enter(&pflags);
 519         }
 520         delayacct_swapin_start();
 521
 522         if (zswap_load(folio)) {
 523                 folio_unlock(folio);
 524         } else if (data_race(sis->flags & SWP_FS_OPS)) {
 525                 swap_read_folio_fs(folio, plug);
 526         } else if (synchronous) {
 527                 swap_read_folio_bdev_sync(folio, sis);
 528         } else {
 529                 swap_read_folio_bdev_async(folio, sis);
 530         }
 531
 532         if (workingset) {
 533                 delayacct_thrashing_end(&in_thrashing);
 534                 psi_memstall_leave(&pflags);
 535         }
 536         delayacct_swapin_end();
 537 }
 538
 539 void __swap_read_unplug(struct swap_iocb *sio)
 540 {
 541         struct iov_iter from;
 542         struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
 543         int ret;
 544
 545         iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len);
 546         ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
 547         if (ret != -EIOCBQUEUED)
 548                 sio_read_complete(&sio->iocb, ret);
 549 }