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_start_writeback(folio);
 200                 folio_unlock(folio);
 201                 folio_end_writeback(folio);
 202                 return 0;
 203         }
 204         if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) {
 205                 folio_mark_dirty(folio);
 206                 return AOP_WRITEPAGE_ACTIVATE;
 207         }
 208
 209         __swap_writepage(folio, wbc);
 210         return 0;
 211 }
 212
 213 static inline void count_swpout_vm_event(struct folio *folio)
 214 {
 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);
 219         }
 220         count_mthp_stat(folio_order(folio), MTHP_STAT_SWPOUT);
 221 #endif
 222         count_vm_events(PSWPOUT, folio_nr_pages(folio));
 223 }
 224
 225 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
 226 static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)
 227 {
 228         struct cgroup_subsys_state *css;
 229         struct mem_cgroup *memcg;
 230
 231         memcg = folio_memcg(folio);
 232         if (!memcg)
 233                 return;
 234
 235         rcu_read_lock();
 236         css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
 237         bio_associate_blkg_from_css(bio, css);
 238         rcu_read_unlock();
 239 }
 240 #else
 241 #define bio_associate_blkg_from_page(bio, folio)                do { } while (0)
 242 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
 243
 244 struct swap_iocb {
 245         struct kiocb            iocb;
 246         struct bio_vec          bvec[SWAP_CLUSTER_MAX];
 247         int                     pages;
 248         int                     len;
 249 };
 250 static mempool_t *sio_pool;
 251
 252 int sio_pool_init(void)
 253 {
 254         if (!sio_pool) {
 255                 mempool_t *pool = mempool_create_kmalloc_pool(
 256                         SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
 257                 if (cmpxchg(&sio_pool, NULL, pool))
 258                         mempool_destroy(pool);
 259         }
 260         if (!sio_pool)
 261                 return -ENOMEM;
 262         return 0;
 263 }
 264
 265 static void sio_write_complete(struct kiocb *iocb, long ret)
 266 {
 267         struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
 268         struct page *page = sio->bvec[0].bv_page;
 269         int p;
 270
 271         if (ret != sio->len) {
 272                 /*
 273                  * In the case of swap-over-nfs, this can be a
 274                  * temporary failure if the system has limited
 275                  * memory for allocating transmit buffers.
 276                  * Mark the page dirty and avoid
 277                  * folio_rotate_reclaimable but rate-limit the
 278                  * messages but do not flag PageError like
 279                  * the normal direct-to-bio case as it could
 280                  * be temporary.
 281                  */
 282                 pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
 283                                    ret, page_file_offset(page));
 284                 for (p = 0; p < sio->pages; p++) {
 285                         page = sio->bvec[p].bv_page;
 286                         set_page_dirty(page);
 287                         ClearPageReclaim(page);
 288                 }
 289         }
 290
 291         for (p = 0; p < sio->pages; p++)
 292                 end_page_writeback(sio->bvec[p].bv_page);
 293
 294         mempool_free(sio, sio_pool);
 295 }
 296
 297 static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc)
 298 {
 299         struct swap_iocb *sio = NULL;
 300         struct swap_info_struct *sis = swp_swap_info(folio->swap);
 301         struct file *swap_file = sis->swap_file;
 302         loff_t pos = folio_file_pos(folio);
 303
 304         count_swpout_vm_event(folio);
 305         folio_start_writeback(folio);
 306         folio_unlock(folio);
 307         if (wbc->swap_plug)
 308                 sio = *wbc->swap_plug;
 309         if (sio) {
 310                 if (sio->iocb.ki_filp != swap_file ||
 311                     sio->iocb.ki_pos + sio->len != pos) {
 312                         swap_write_unplug(sio);
 313                         sio = NULL;
 314                 }
 315         }
 316         if (!sio) {
 317                 sio = mempool_alloc(sio_pool, GFP_NOIO);
 318                 init_sync_kiocb(&sio->iocb, swap_file);
 319                 sio->iocb.ki_complete = sio_write_complete;
 320                 sio->iocb.ki_pos = pos;
 321                 sio->pages = 0;
 322                 sio->len = 0;
 323         }
 324         bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
 325         sio->len += folio_size(folio);
 326         sio->pages += 1;
 327         if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) {
 328                 swap_write_unplug(sio);
 329                 sio = NULL;
 330         }
 331         if (wbc->swap_plug)
 332                 *wbc->swap_plug = sio;
 333 }
 334
 335 static void swap_writepage_bdev_sync(struct folio *folio,
 336                 struct writeback_control *wbc, struct swap_info_struct *sis)
 337 {
 338         struct bio_vec bv;
 339         struct bio bio;
 340
 341         bio_init(&bio, sis->bdev, &bv, 1,
 342                  REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc));
 343         bio.bi_iter.bi_sector = swap_folio_sector(folio);
 344         bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
 345
 346         bio_associate_blkg_from_page(&bio, folio);
 347         count_swpout_vm_event(folio);
 348
 349         folio_start_writeback(folio);
 350         folio_unlock(folio);
 351
 352         submit_bio_wait(&bio);
 353         __end_swap_bio_write(&bio);
 354 }
 355
 356 static void swap_writepage_bdev_async(struct folio *folio,
 357                 struct writeback_control *wbc, struct swap_info_struct *sis)
 358 {
 359         struct bio *bio;
 360
 361         bio = bio_alloc(sis->bdev, 1,
 362                         REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
 363                         GFP_NOIO);
 364         bio->bi_iter.bi_sector = swap_folio_sector(folio);
 365         bio->bi_end_io = end_swap_bio_write;
 366         bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
 367
 368         bio_associate_blkg_from_page(bio, folio);
 369         count_swpout_vm_event(folio);
 370         folio_start_writeback(folio);
 371         folio_unlock(folio);
 372         submit_bio(bio);
 373 }
 374
 375 void __swap_writepage(struct folio *folio, struct writeback_control *wbc)
 376 {
 377         struct swap_info_struct *sis = swp_swap_info(folio->swap);
 378
 379         VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
 380         /*
 381          * ->flags can be updated non-atomicially (scan_swap_map_slots),
 382          * but that will never affect SWP_FS_OPS, so the data_race
 383          * is safe.
 384          */
 385         if (data_race(sis->flags & SWP_FS_OPS))
 386                 swap_writepage_fs(folio, wbc);
 387         else if (sis->flags & SWP_SYNCHRONOUS_IO)
 388                 swap_writepage_bdev_sync(folio, wbc, sis);
 389         else
 390                 swap_writepage_bdev_async(folio, wbc, sis);
 391 }
 392
 393 void swap_write_unplug(struct swap_iocb *sio)
 394 {
 395         struct iov_iter from;
 396         struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
 397         int ret;
 398
 399         iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len);
 400         ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
 401         if (ret != -EIOCBQUEUED)
 402                 sio_write_complete(&sio->iocb, ret);
 403 }
 404
 405 static void sio_read_complete(struct kiocb *iocb, long ret)
 406 {
 407         struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
 408         int p;
 409
 410         if (ret == sio->len) {
 411                 for (p = 0; p < sio->pages; p++) {
 412                         struct folio *folio = page_folio(sio->bvec[p].bv_page);
 413
 414                         folio_mark_uptodate(folio);
 415                         folio_unlock(folio);
 416                 }
 417                 count_vm_events(PSWPIN, sio->pages);
 418         } else {
 419                 for (p = 0; p < sio->pages; p++) {
 420                         struct folio *folio = page_folio(sio->bvec[p].bv_page);
 421
 422                         folio_unlock(folio);
 423                 }
 424                 pr_alert_ratelimited("Read-error on swap-device\n");
 425         }
 426         mempool_free(sio, sio_pool);
 427 }
 428
 429 static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug)
 430 {
 431         struct swap_info_struct *sis = swp_swap_info(folio->swap);
 432         struct swap_iocb *sio = NULL;
 433         loff_t pos = folio_file_pos(folio);
 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_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
 453         sio->len += folio_size(folio);
 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_read_folio_bdev_sync(struct folio *folio,
 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_folio_sector(folio);
 471         bio_add_folio_nofail(&bio, folio, folio_size(folio), 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_read_folio_bdev_async(struct folio *folio,
 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_folio_sector(folio);
 490         bio->bi_end_io = end_swap_bio_read;
 491         bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
 492         count_vm_event(PSWPIN);
 493         submit_bio(bio);
 494 }
 495
 496 void swap_read_folio(struct folio *folio, bool synchronous,
 497                 struct swap_iocb **plug)
 498 {
 499         struct swap_info_struct *sis = swp_swap_info(folio->swap);
 500         bool workingset = folio_test_workingset(folio);
 501         unsigned long pflags;
 502         bool in_thrashing;
 503
 504         VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio);
 505         VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 506         VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);
 507
 508         /*
 509          * Count submission time as memory stall and delay. When the device
 510          * is congested, or the submitting cgroup IO-throttled, submission
 511          * can be a significant part of overall IO time.
 512          */
 513         if (workingset) {
 514                 delayacct_thrashing_start(&in_thrashing);
 515                 psi_memstall_enter(&pflags);
 516         }
 517         delayacct_swapin_start();
 518
 519         if (zswap_load(folio)) {
 520                 folio_mark_uptodate(folio);
 521                 folio_unlock(folio);
 522         } else if (data_race(sis->flags & SWP_FS_OPS)) {
 523                 swap_read_folio_fs(folio, plug);
 524         } else if (synchronous || (sis->flags & SWP_SYNCHRONOUS_IO)) {
 525                 swap_read_folio_bdev_sync(folio, sis);
 526         } else {
 527                 swap_read_folio_bdev_async(folio, sis);
 528         }
 529
 530         if (workingset) {
 531                 delayacct_thrashing_end(&in_thrashing);
 532                 psi_memstall_leave(&pflags);
 533         }
 534         delayacct_swapin_end();
 535 }
 536
 537 void __swap_read_unplug(struct swap_iocb *sio)
 538 {
 539         struct iov_iter from;
 540         struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
 541         int ret;
 542
 543         iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len);
 544         ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
 545         if (ret != -EIOCBQUEUED)
 546                 sio_read_complete(&sio->iocb, ret);
 547 }