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/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
  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
  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
  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  */
 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
 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 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
 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
 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, ITER_SOURCE, 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
 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
 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
 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
 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, ITER_DEST, 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 }