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
  30 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         bio_put(bio);
  52 }
  53
  54 static void end_swap_bio_read(struct bio *bio)
  55 {
  56         struct page *page = bio_first_page_all(bio);
  57         struct task_struct *waiter = bio->bi_private;
  58
  59         if (bio->bi_status) {
  60                 SetPageError(page);
  61                 ClearPageUptodate(page);
  62                 pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n",
  63                                      MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
  64                                      (unsigned long long)bio->bi_iter.bi_sector);
  65                 goto out;
  66         }
  67
  68         SetPageUptodate(page);
  69 out:
  70         unlock_page(page);
  71         WRITE_ONCE(bio->bi_private, NULL);
  72         bio_put(bio);
  73         if (waiter) {
  74                 blk_wake_io_task(waiter);
  75                 put_task_struct(waiter);
  76         }
  77 }
  78
  79 int generic_swapfile_activate(struct swap_info_struct *sis,
  80                                 struct file *swap_file,
  81                                 sector_t *span)
  82 {
  83         struct address_space *mapping = swap_file->f_mapping;
  84         struct inode *inode = mapping->host;
  85         unsigned blocks_per_page;
  86         unsigned long page_no;
  87         unsigned blkbits;
  88         sector_t probe_block;
  89         sector_t last_block;
  90         sector_t lowest_block = -1;
  91         sector_t highest_block = 0;
  92         int nr_extents = 0;
  93         int ret;
  94
  95         blkbits = inode->i_blkbits;
  96         blocks_per_page = PAGE_SIZE >> blkbits;
  97
  98         /*
  99          * Map all the blocks into the extent tree.  This code doesn't try
 100          * to be very smart.
 101          */
 102         probe_block = 0;
 103         page_no = 0;
 104         last_block = i_size_read(inode) >> blkbits;
 105         while ((probe_block + blocks_per_page) <= last_block &&
 106                         page_no < sis->max) {
 107                 unsigned block_in_page;
 108                 sector_t first_block;
 109
 110                 cond_resched();
 111
 112                 first_block = probe_block;
 113                 ret = bmap(inode, &first_block);
 114                 if (ret || !first_block)
 115                         goto bad_bmap;
 116
 117                 /*
 118                  * It must be PAGE_SIZE aligned on-disk
 119                  */
 120                 if (first_block & (blocks_per_page - 1)) {
 121                         probe_block++;
 122                         goto reprobe;
 123                 }
 124
 125                 for (block_in_page = 1; block_in_page < blocks_per_page;
 126                                         block_in_page++) {
 127                         sector_t block;
 128
 129                         block = probe_block + block_in_page;
 130                         ret = bmap(inode, &block);
 131                         if (ret || !block)
 132                                 goto bad_bmap;
 133
 134                         if (block != first_block + block_in_page) {
 135                                 /* Discontiguity */
 136                                 probe_block++;
 137                                 goto reprobe;
 138                         }
 139                 }
 140
 141                 first_block >>= (PAGE_SHIFT - blkbits);
 142                 if (page_no) {  /* exclude the header page */
 143                         if (first_block < lowest_block)
 144                                 lowest_block = first_block;
 145                         if (first_block > highest_block)
 146                                 highest_block = first_block;
 147                 }
 148
 149                 /*
 150                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
 151                  */
 152                 ret = add_swap_extent(sis, page_no, 1, first_block);
 153                 if (ret < 0)
 154                         goto out;
 155                 nr_extents += ret;
 156                 page_no++;
 157                 probe_block += blocks_per_page;
 158 reprobe:
 159                 continue;
 160         }
 161         ret = nr_extents;
 162         *span = 1 + highest_block - lowest_block;
 163         if (page_no == 0)
 164                 page_no = 1;    /* force Empty message */
 165         sis->max = page_no;
 166         sis->pages = page_no - 1;
 167         sis->highest_bit = page_no - 1;
 168 out:
 169         return ret;
 170 bad_bmap:
 171         pr_err("swapon: swapfile has holes\n");
 172         ret = -EINVAL;
 173         goto out;
 174 }
 175
 176 /*
 177  * We may have stale swap cache pages in memory: notice
 178  * them here and get rid of the unnecessary final write.
 179  */
 180 int swap_writepage(struct page *page, struct writeback_control *wbc)
 181 {
 182         int ret = 0;
 183
 184         if (try_to_free_swap(page)) {
 185                 unlock_page(page);
 186                 goto out;
 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(page);
 193         if (ret) {
 194                 set_page_dirty(page);
 195                 unlock_page(page);
 196                 goto out;
 197         }
 198         if (frontswap_store(page) == 0) {
 199                 set_page_writeback(page);
 200                 unlock_page(page);
 201                 end_page_writeback(page);
 202                 goto out;
 203         }
 204         ret = __swap_writepage(page, wbc, end_swap_bio_write);
 205 out:
 206         return ret;
 207 }
 208
 209 static inline void count_swpout_vm_event(struct page *page)
 210 {
 211 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 212         if (unlikely(PageTransHuge(page)))
 213                 count_vm_event(THP_SWPOUT);
 214 #endif
 215         count_vm_events(PSWPOUT, thp_nr_pages(page));
 216 }
 217
 218 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
 219 static void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
 220 {
 221         struct cgroup_subsys_state *css;
 222         struct mem_cgroup *memcg;
 223
 224         memcg = page_memcg(page);
 225         if (!memcg)
 226                 return;
 227
 228         rcu_read_lock();
 229         css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
 230         bio_associate_blkg_from_css(bio, css);
 231         rcu_read_unlock();
 232 }
 233 #else
 234 #define bio_associate_blkg_from_page(bio, page)         do { } while (0)
 235 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
 236
 237 int __swap_writepage(struct page *page, struct writeback_control *wbc,
 238                 bio_end_io_t end_write_func)
 239 {
 240         struct bio *bio;
 241         int ret;
 242         struct swap_info_struct *sis = page_swap_info(page);
 243
 244         VM_BUG_ON_PAGE(!PageSwapCache(page), page);
 245         if (data_race(sis->flags & SWP_FS_OPS)) {
 246                 struct kiocb kiocb;
 247                 struct file *swap_file = sis->swap_file;
 248                 struct address_space *mapping = swap_file->f_mapping;
 249                 struct bio_vec bv = {
 250                         .bv_page = page,
 251                         .bv_len  = PAGE_SIZE,
 252                         .bv_offset = 0
 253                 };
 254                 struct iov_iter from;
 255
 256                 iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
 257                 init_sync_kiocb(&kiocb, swap_file);
 258                 kiocb.ki_pos = page_file_offset(page);
 259
 260                 set_page_writeback(page);
 261                 unlock_page(page);
 262                 ret = mapping->a_ops->direct_IO(&kiocb, &from);
 263                 if (ret == PAGE_SIZE) {
 264                         count_vm_event(PSWPOUT);
 265                         ret = 0;
 266                 } else {
 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                         set_page_dirty(page);
 278                         ClearPageReclaim(page);
 279                         pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
 280                                            page_file_offset(page));
 281                 }
 282                 end_page_writeback(page);
 283                 return ret;
 284         }
 285
 286         ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
 287         if (!ret) {
 288                 count_swpout_vm_event(page);
 289                 return 0;
 290         }
 291
 292         bio = bio_alloc(sis->bdev, 1,
 293                         REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
 294                         GFP_NOIO);
 295         bio->bi_iter.bi_sector = swap_page_sector(page);
 296         bio->bi_end_io = end_write_func;
 297         bio_add_page(bio, page, thp_size(page), 0);
 298
 299         bio_associate_blkg_from_page(bio, page);
 300         count_swpout_vm_event(page);
 301         set_page_writeback(page);
 302         unlock_page(page);
 303         submit_bio(bio);
 304
 305         return 0;
 306 }
 307
 308 int swap_readpage(struct page *page, bool synchronous)
 309 {
 310         struct bio *bio;
 311         int ret = 0;
 312         struct swap_info_struct *sis = page_swap_info(page);
 313         bool workingset = PageWorkingset(page);
 314         unsigned long pflags;
 315
 316         VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
 317         VM_BUG_ON_PAGE(!PageLocked(page), page);
 318         VM_BUG_ON_PAGE(PageUptodate(page), page);
 319
 320         /*
 321          * Count submission time as memory stall. When the device is congested,
 322          * or the submitting cgroup IO-throttled, submission can be a
 323          * significant part of overall IO time.
 324          */
 325         if (workingset)
 326                 psi_memstall_enter(&pflags);
 327         delayacct_swapin_start();
 328
 329         if (frontswap_load(page) == 0) {
 330                 SetPageUptodate(page);
 331                 unlock_page(page);
 332                 goto out;
 333         }
 334
 335         if (data_race(sis->flags & SWP_FS_OPS)) {
 336                 struct file *swap_file = sis->swap_file;
 337                 struct address_space *mapping = swap_file->f_mapping;
 338
 339                 ret = mapping->a_ops->readpage(swap_file, page);
 340                 if (!ret)
 341                         count_vm_event(PSWPIN);
 342                 goto out;
 343         }
 344
 345         if (sis->flags & SWP_SYNCHRONOUS_IO) {
 346                 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
 347                 if (!ret) {
 348                         count_vm_event(PSWPIN);
 349                         goto out;
 350                 }
 351         }
 352
 353         ret = 0;
 354         bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL);
 355         bio->bi_iter.bi_sector = swap_page_sector(page);
 356         bio->bi_end_io = end_swap_bio_read;
 357         bio_add_page(bio, page, thp_size(page), 0);
 358         /*
 359          * Keep this task valid during swap readpage because the oom killer may
 360          * attempt to access it in the page fault retry time check.
 361          */
 362         if (synchronous) {
 363                 bio->bi_opf |= REQ_POLLED;
 364                 get_task_struct(current);
 365                 bio->bi_private = current;
 366         }
 367         count_vm_event(PSWPIN);
 368         bio_get(bio);
 369         submit_bio(bio);
 370         while (synchronous) {
 371                 set_current_state(TASK_UNINTERRUPTIBLE);
 372                 if (!READ_ONCE(bio->bi_private))
 373                         break;
 374
 375                 if (!bio_poll(bio, NULL, 0))
 376                         blk_io_schedule();
 377         }
 378         __set_current_state(TASK_RUNNING);
 379         bio_put(bio);
 380
 381 out:
 382         if (workingset)
 383                 psi_memstall_leave(&pflags);
 384         delayacct_swapin_end();
 385         return ret;
 386 }
 387
 388 bool swap_dirty_folio(struct address_space *mapping, struct folio *folio)
 389 {
 390         struct swap_info_struct *sis = swp_swap_info(folio_swap_entry(folio));
 391
 392         if (data_race(sis->flags & SWP_FS_OPS)) {
 393                 const struct address_space_operations *aops;
 394
 395                 mapping = sis->swap_file->f_mapping;
 396                 aops = mapping->a_ops;
 397
 398                 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
 399                 return aops->dirty_folio(mapping, folio);
 400         } else {
 401                 return noop_dirty_folio(mapping, folio);
 402         }
 403 }