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
  29 void end_swap_bio_write(struct bio *bio)
  30 {
  31         struct page *page = bio_first_page_all(bio);
  32
  33         if (bio->bi_status) {
  34                 SetPageError(page);
  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 rotate_reclaimable_page()
  42                  */
  43                 set_page_dirty(page);
  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                 ClearPageReclaim(page);
  48         }
  49         end_page_writeback(page);
  50         bio_put(bio);
  51 }
  52
  53 static void end_swap_bio_read(struct bio *bio)
  54 {
  55         struct page *page = bio_first_page_all(bio);
  56         struct task_struct *waiter = bio->bi_private;
  57
  58         if (bio->bi_status) {
  59                 SetPageError(page);
  60                 ClearPageUptodate(page);
  61                 pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n",
  62                                      MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
  63                                      (unsigned long long)bio->bi_iter.bi_sector);
  64                 goto out;
  65         }
  66
  67         SetPageUptodate(page);
  68 out:
  69         unlock_page(page);
  70         WRITE_ONCE(bio->bi_private, NULL);
  71         bio_put(bio);
  72         if (waiter) {
  73                 blk_wake_io_task(waiter);
  74                 put_task_struct(waiter);
  75         }
  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         int ret = 0;
 182
 183         if (try_to_free_swap(page)) {
 184                 unlock_page(page);
 185                 goto out;
 186         }
 187         /*
 188          * Arch code may have to preserve more data than just the page
 189          * contents, e.g. memory tags.
 190          */
 191         ret = arch_prepare_to_swap(page);
 192         if (ret) {
 193                 set_page_dirty(page);
 194                 unlock_page(page);
 195                 goto out;
 196         }
 197         if (frontswap_store(page) == 0) {
 198                 set_page_writeback(page);
 199                 unlock_page(page);
 200                 end_page_writeback(page);
 201                 goto out;
 202         }
 203         ret = __swap_writepage(page, wbc, end_swap_bio_write);
 204 out:
 205         return ret;
 206 }
 207
 208 static inline void count_swpout_vm_event(struct page *page)
 209 {
 210 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 211         if (unlikely(PageTransHuge(page)))
 212                 count_vm_event(THP_SWPOUT);
 213 #endif
 214         count_vm_events(PSWPOUT, thp_nr_pages(page));
 215 }
 216
 217 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
 218 static void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
 219 {
 220         struct cgroup_subsys_state *css;
 221         struct mem_cgroup *memcg;
 222
 223         memcg = page_memcg(page);
 224         if (!memcg)
 225                 return;
 226
 227         rcu_read_lock();
 228         css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
 229         bio_associate_blkg_from_css(bio, css);
 230         rcu_read_unlock();
 231 }
 232 #else
 233 #define bio_associate_blkg_from_page(bio, page)         do { } while (0)
 234 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */
 235
 236 int __swap_writepage(struct page *page, struct writeback_control *wbc,
 237                 bio_end_io_t end_write_func)
 238 {
 239         struct bio *bio;
 240         int ret;
 241         struct swap_info_struct *sis = page_swap_info(page);
 242
 243         VM_BUG_ON_PAGE(!PageSwapCache(page), page);
 244         if (data_race(sis->flags & SWP_FS_OPS)) {
 245                 struct kiocb kiocb;
 246                 struct file *swap_file = sis->swap_file;
 247                 struct address_space *mapping = swap_file->f_mapping;
 248                 struct bio_vec bv = {
 249                         .bv_page = page,
 250                         .bv_len  = PAGE_SIZE,
 251                         .bv_offset = 0
 252                 };
 253                 struct iov_iter from;
 254
 255                 iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
 256                 init_sync_kiocb(&kiocb, swap_file);
 257                 kiocb.ki_pos = page_file_offset(page);
 258
 259                 set_page_writeback(page);
 260                 unlock_page(page);
 261                 ret = mapping->a_ops->direct_IO(&kiocb, &from);
 262                 if (ret == PAGE_SIZE) {
 263                         count_vm_event(PSWPOUT);
 264                         ret = 0;
 265                 } else {
 266                         /*
 267                          * In the case of swap-over-nfs, this can be a
 268                          * temporary failure if the system has limited
 269                          * memory for allocating transmit buffers.
 270                          * Mark the page dirty and avoid
 271                          * rotate_reclaimable_page but rate-limit the
 272                          * messages but do not flag PageError like
 273                          * the normal direct-to-bio case as it could
 274                          * be temporary.
 275                          */
 276                         set_page_dirty(page);
 277                         ClearPageReclaim(page);
 278                         pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
 279                                            page_file_offset(page));
 280                 }
 281                 end_page_writeback(page);
 282                 return ret;
 283         }
 284
 285         ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
 286         if (!ret) {
 287                 count_swpout_vm_event(page);
 288                 return 0;
 289         }
 290
 291         bio = bio_alloc(GFP_NOIO, 1);
 292         bio_set_dev(bio, sis->bdev);
 293         bio->bi_iter.bi_sector = swap_page_sector(page);
 294         bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc);
 295         bio->bi_end_io = end_write_func;
 296         bio_add_page(bio, page, thp_size(page), 0);
 297
 298         bio_associate_blkg_from_page(bio, page);
 299         count_swpout_vm_event(page);
 300         set_page_writeback(page);
 301         unlock_page(page);
 302         submit_bio(bio);
 303
 304         return 0;
 305 }
 306
 307 int swap_readpage(struct page *page, bool synchronous)
 308 {
 309         struct bio *bio;
 310         int ret = 0;
 311         struct swap_info_struct *sis = page_swap_info(page);
 312         blk_qc_t qc;
 313         struct gendisk *disk;
 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         psi_memstall_enter(&pflags);
 326
 327         if (frontswap_load(page) == 0) {
 328                 SetPageUptodate(page);
 329                 unlock_page(page);
 330                 goto out;
 331         }
 332
 333         if (data_race(sis->flags & SWP_FS_OPS)) {
 334                 struct file *swap_file = sis->swap_file;
 335                 struct address_space *mapping = swap_file->f_mapping;
 336
 337                 ret = mapping->a_ops->readpage(swap_file, page);
 338                 if (!ret)
 339                         count_vm_event(PSWPIN);
 340                 goto out;
 341         }
 342
 343         if (sis->flags & SWP_SYNCHRONOUS_IO) {
 344                 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
 345                 if (!ret) {
 346                         count_vm_event(PSWPIN);
 347                         goto out;
 348                 }
 349         }
 350
 351         ret = 0;
 352         bio = bio_alloc(GFP_KERNEL, 1);
 353         bio_set_dev(bio, sis->bdev);
 354         bio->bi_opf = REQ_OP_READ;
 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         disk = bio->bi_bdev->bd_disk;
 360         /*
 361          * Keep this task valid during swap readpage because the oom killer may
 362          * attempt to access it in the page fault retry time check.
 363          */
 364         if (synchronous) {
 365                 bio->bi_opf |= REQ_HIPRI;
 366                 get_task_struct(current);
 367                 bio->bi_private = current;
 368         }
 369         count_vm_event(PSWPIN);
 370         bio_get(bio);
 371         qc = submit_bio(bio);
 372         while (synchronous) {
 373                 set_current_state(TASK_UNINTERRUPTIBLE);
 374                 if (!READ_ONCE(bio->bi_private))
 375                         break;
 376
 377                 if (!blk_poll(disk->queue, qc, true))
 378                         blk_io_schedule();
 379         }
 380         __set_current_state(TASK_RUNNING);
 381         bio_put(bio);
 382
 383 out:
 384         psi_memstall_leave(&pflags);
 385         return ret;
 386 }
 387
 388 int swap_set_page_dirty(struct page *page)
 389 {
 390         struct swap_info_struct *sis = page_swap_info(page);
 391
 392         if (data_race(sis->flags & SWP_FS_OPS)) {
 393                 struct address_space *mapping = sis->swap_file->f_mapping;
 394
 395                 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
 396                 return mapping->a_ops->set_page_dirty(page);
 397         } else {
 398                 return __set_page_dirty_no_writeback(page);
 399         }
 400 }