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 swap_slot_free_notify(struct page *page) 55 { 56 struct swap_info_struct *sis; 57 struct gendisk *disk; 58 swp_entry_t entry; 59 60 /* 61 * There is no guarantee that the page is in swap cache - the software 62 * suspend code (at least) uses end_swap_bio_read() against a non- 63 * swapcache page. So we must check PG_swapcache before proceeding with 64 * this optimization. 65 */ 66 if (unlikely(!PageSwapCache(page))) 67 return; 68 69 sis = page_swap_info(page); 70 if (data_race(!(sis->flags & SWP_BLKDEV))) 71 return; 72 73 /* 74 * The swap subsystem performs lazy swap slot freeing, 75 * expecting that the page will be swapped out again. 76 * So we can avoid an unnecessary write if the page 77 * isn't redirtied. 78 * This is good for real swap storage because we can 79 * reduce unnecessary I/O and enhance wear-leveling 80 * if an SSD is used as the as swap device. 81 * But if in-memory swap device (eg zram) is used, 82 * this causes a duplicated copy between uncompressed 83 * data in VM-owned memory and compressed data in 84 * zram-owned memory. So let's free zram-owned memory 85 * and make the VM-owned decompressed page *dirty*, 86 * so the page should be swapped out somewhere again if 87 * we again wish to reclaim it. 88 */ 89 disk = sis->bdev->bd_disk; 90 entry.val = page_private(page); 91 if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) { 92 unsigned long offset; 93 94 offset = swp_offset(entry); 95 96 SetPageDirty(page); 97 disk->fops->swap_slot_free_notify(sis->bdev, 98 offset); 99 } 100 } 101 102 static void end_swap_bio_read(struct bio *bio) 103 { 104 struct page *page = bio_first_page_all(bio); 105 struct task_struct *waiter = bio->bi_private; 106 107 if (bio->bi_status) { 108 SetPageError(page); 109 ClearPageUptodate(page); 110 pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n", 111 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)), 112 (unsigned long long)bio->bi_iter.bi_sector); 113 goto out; 114 } 115 116 SetPageUptodate(page); 117 swap_slot_free_notify(page); 118 out: 119 unlock_page(page); 120 WRITE_ONCE(bio->bi_private, NULL); 121 bio_put(bio); 122 if (waiter) { 123 blk_wake_io_task(waiter); 124 put_task_struct(waiter); 125 } 126 } 127 128 int generic_swapfile_activate(struct swap_info_struct *sis, 129 struct file *swap_file, 130 sector_t *span) 131 { 132 struct address_space *mapping = swap_file->f_mapping; 133 struct inode *inode = mapping->host; 134 unsigned blocks_per_page; 135 unsigned long page_no; 136 unsigned blkbits; 137 sector_t probe_block; 138 sector_t last_block; 139 sector_t lowest_block = -1; 140 sector_t highest_block = 0; 141 int nr_extents = 0; 142 int ret; 143 144 blkbits = inode->i_blkbits; 145 blocks_per_page = PAGE_SIZE >> blkbits; 146 147 /* 148 * Map all the blocks into the extent tree. This code doesn't try 149 * to be very smart. 150 */ 151 probe_block = 0; 152 page_no = 0; 153 last_block = i_size_read(inode) >> blkbits; 154 while ((probe_block + blocks_per_page) <= last_block && 155 page_no < sis->max) { 156 unsigned block_in_page; 157 sector_t first_block; 158 159 cond_resched(); 160 161 first_block = probe_block; 162 ret = bmap(inode, &first_block); 163 if (ret || !first_block) 164 goto bad_bmap; 165 166 /* 167 * It must be PAGE_SIZE aligned on-disk 168 */ 169 if (first_block & (blocks_per_page - 1)) { 170 probe_block++; 171 goto reprobe; 172 } 173 174 for (block_in_page = 1; block_in_page < blocks_per_page; 175 block_in_page++) { 176 sector_t block; 177 178 block = probe_block + block_in_page; 179 ret = bmap(inode, &block); 180 if (ret || !block) 181 goto bad_bmap; 182 183 if (block != first_block + block_in_page) { 184 /* Discontiguity */ 185 probe_block++; 186 goto reprobe; 187 } 188 } 189 190 first_block >>= (PAGE_SHIFT - blkbits); 191 if (page_no) { /* exclude the header page */ 192 if (first_block < lowest_block) 193 lowest_block = first_block; 194 if (first_block > highest_block) 195 highest_block = first_block; 196 } 197 198 /* 199 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 200 */ 201 ret = add_swap_extent(sis, page_no, 1, first_block); 202 if (ret < 0) 203 goto out; 204 nr_extents += ret; 205 page_no++; 206 probe_block += blocks_per_page; 207 reprobe: 208 continue; 209 } 210 ret = nr_extents; 211 *span = 1 + highest_block - lowest_block; 212 if (page_no == 0) 213 page_no = 1; /* force Empty message */ 214 sis->max = page_no; 215 sis->pages = page_no - 1; 216 sis->highest_bit = page_no - 1; 217 out: 218 return ret; 219 bad_bmap: 220 pr_err("swapon: swapfile has holes\n"); 221 ret = -EINVAL; 222 goto out; 223 } 224 225 /* 226 * We may have stale swap cache pages in memory: notice 227 * them here and get rid of the unnecessary final write. 228 */ 229 int swap_writepage(struct page *page, struct writeback_control *wbc) 230 { 231 int ret = 0; 232 233 if (try_to_free_swap(page)) { 234 unlock_page(page); 235 goto out; 236 } 237 /* 238 * Arch code may have to preserve more data than just the page 239 * contents, e.g. memory tags. 240 */ 241 ret = arch_prepare_to_swap(page); 242 if (ret) { 243 set_page_dirty(page); 244 unlock_page(page); 245 goto out; 246 } 247 if (frontswap_store(page) == 0) { 248 set_page_writeback(page); 249 unlock_page(page); 250 end_page_writeback(page); 251 goto out; 252 } 253 ret = __swap_writepage(page, wbc, end_swap_bio_write); 254 out: 255 return ret; 256 } 257 258 static inline void count_swpout_vm_event(struct page *page) 259 { 260 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 261 if (unlikely(PageTransHuge(page))) 262 count_vm_event(THP_SWPOUT); 263 #endif 264 count_vm_events(PSWPOUT, thp_nr_pages(page)); 265 } 266 267 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) 268 static void bio_associate_blkg_from_page(struct bio *bio, struct page *page) 269 { 270 struct cgroup_subsys_state *css; 271 struct mem_cgroup *memcg; 272 273 memcg = page_memcg(page); 274 if (!memcg) 275 return; 276 277 rcu_read_lock(); 278 css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys); 279 bio_associate_blkg_from_css(bio, css); 280 rcu_read_unlock(); 281 } 282 #else 283 #define bio_associate_blkg_from_page(bio, page) do { } while (0) 284 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */ 285 286 int __swap_writepage(struct page *page, struct writeback_control *wbc, 287 bio_end_io_t end_write_func) 288 { 289 struct bio *bio; 290 int ret; 291 struct swap_info_struct *sis = page_swap_info(page); 292 293 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 294 if (data_race(sis->flags & SWP_FS_OPS)) { 295 struct kiocb kiocb; 296 struct file *swap_file = sis->swap_file; 297 struct address_space *mapping = swap_file->f_mapping; 298 struct bio_vec bv = { 299 .bv_page = page, 300 .bv_len = PAGE_SIZE, 301 .bv_offset = 0 302 }; 303 struct iov_iter from; 304 305 iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE); 306 init_sync_kiocb(&kiocb, swap_file); 307 kiocb.ki_pos = page_file_offset(page); 308 309 set_page_writeback(page); 310 unlock_page(page); 311 ret = mapping->a_ops->direct_IO(&kiocb, &from); 312 if (ret == PAGE_SIZE) { 313 count_vm_event(PSWPOUT); 314 ret = 0; 315 } else { 316 /* 317 * In the case of swap-over-nfs, this can be a 318 * temporary failure if the system has limited 319 * memory for allocating transmit buffers. 320 * Mark the page dirty and avoid 321 * folio_rotate_reclaimable but rate-limit the 322 * messages but do not flag PageError like 323 * the normal direct-to-bio case as it could 324 * be temporary. 325 */ 326 set_page_dirty(page); 327 ClearPageReclaim(page); 328 pr_err_ratelimited("Write error on dio swapfile (%llu)\n", 329 page_file_offset(page)); 330 } 331 end_page_writeback(page); 332 return ret; 333 } 334 335 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); 336 if (!ret) { 337 count_swpout_vm_event(page); 338 return 0; 339 } 340 341 bio = bio_alloc(sis->bdev, 1, 342 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc), 343 GFP_NOIO); 344 bio->bi_iter.bi_sector = swap_page_sector(page); 345 bio->bi_end_io = end_write_func; 346 bio_add_page(bio, page, thp_size(page), 0); 347 348 bio_associate_blkg_from_page(bio, page); 349 count_swpout_vm_event(page); 350 set_page_writeback(page); 351 unlock_page(page); 352 submit_bio(bio); 353 354 return 0; 355 } 356 357 int swap_readpage(struct page *page, bool synchronous) 358 { 359 struct bio *bio; 360 int ret = 0; 361 struct swap_info_struct *sis = page_swap_info(page); 362 bool workingset = PageWorkingset(page); 363 unsigned long pflags; 364 365 VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page); 366 VM_BUG_ON_PAGE(!PageLocked(page), page); 367 VM_BUG_ON_PAGE(PageUptodate(page), page); 368 369 /* 370 * Count submission time as memory stall. When the device is congested, 371 * or the submitting cgroup IO-throttled, submission can be a 372 * significant part of overall IO time. 373 */ 374 if (workingset) 375 psi_memstall_enter(&pflags); 376 delayacct_swapin_start(); 377 378 if (frontswap_load(page) == 0) { 379 SetPageUptodate(page); 380 unlock_page(page); 381 goto out; 382 } 383 384 if (data_race(sis->flags & SWP_FS_OPS)) { 385 struct file *swap_file = sis->swap_file; 386 struct address_space *mapping = swap_file->f_mapping; 387 388 ret = mapping->a_ops->readpage(swap_file, page); 389 if (!ret) 390 count_vm_event(PSWPIN); 391 goto out; 392 } 393 394 if (sis->flags & SWP_SYNCHRONOUS_IO) { 395 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); 396 if (!ret) { 397 if (trylock_page(page)) { 398 swap_slot_free_notify(page); 399 unlock_page(page); 400 } 401 402 count_vm_event(PSWPIN); 403 goto out; 404 } 405 } 406 407 ret = 0; 408 bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL); 409 bio->bi_iter.bi_sector = swap_page_sector(page); 410 bio->bi_end_io = end_swap_bio_read; 411 bio_add_page(bio, page, thp_size(page), 0); 412 /* 413 * Keep this task valid during swap readpage because the oom killer may 414 * attempt to access it in the page fault retry time check. 415 */ 416 if (synchronous) { 417 bio->bi_opf |= REQ_POLLED; 418 get_task_struct(current); 419 bio->bi_private = current; 420 } 421 count_vm_event(PSWPIN); 422 bio_get(bio); 423 submit_bio(bio); 424 while (synchronous) { 425 set_current_state(TASK_UNINTERRUPTIBLE); 426 if (!READ_ONCE(bio->bi_private)) 427 break; 428 429 if (!bio_poll(bio, NULL, 0)) 430 blk_io_schedule(); 431 } 432 __set_current_state(TASK_RUNNING); 433 bio_put(bio); 434 435 out: 436 if (workingset) 437 psi_memstall_leave(&pflags); 438 delayacct_swapin_end(); 439 return ret; 440 } 441 442 bool swap_dirty_folio(struct address_space *mapping, struct folio *folio) 443 { 444 struct swap_info_struct *sis = swp_swap_info(folio_swap_entry(folio)); 445 446 if (data_race(sis->flags & SWP_FS_OPS)) { 447 const struct address_space_operations *aops; 448 449 mapping = sis->swap_file->f_mapping; 450 aops = mapping->a_ops; 451 452 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio); 453 return aops->dirty_folio(mapping, folio); 454 } else { 455 return noop_dirty_folio(mapping, folio); 456 } 457 } 458