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_unlock(folio); 200 return 0; 201 } 202 if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) { 203 folio_mark_dirty(folio); 204 return AOP_WRITEPAGE_ACTIVATE; 205 } 206 207 __swap_writepage(folio, wbc); 208 return 0; 209 } 210 211 static inline void count_swpout_vm_event(struct folio *folio) 212 { 213 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 214 if (unlikely(folio_test_pmd_mappable(folio))) { 215 count_memcg_folio_events(folio, THP_SWPOUT, 1); 216 count_vm_event(THP_SWPOUT); 217 } 218 count_mthp_stat(folio_order(folio), MTHP_STAT_SWPOUT); 219 #endif 220 count_vm_events(PSWPOUT, folio_nr_pages(folio)); 221 } 222 223 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) 224 static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio) 225 { 226 struct cgroup_subsys_state *css; 227 struct mem_cgroup *memcg; 228 229 memcg = folio_memcg(folio); 230 if (!memcg) 231 return; 232 233 rcu_read_lock(); 234 css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys); 235 bio_associate_blkg_from_css(bio, css); 236 rcu_read_unlock(); 237 } 238 #else 239 #define bio_associate_blkg_from_page(bio, folio) do { } while (0) 240 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */ 241 242 struct swap_iocb { 243 struct kiocb iocb; 244 struct bio_vec bvec[SWAP_CLUSTER_MAX]; 245 int pages; 246 int len; 247 }; 248 static mempool_t *sio_pool; 249 250 int sio_pool_init(void) 251 { 252 if (!sio_pool) { 253 mempool_t *pool = mempool_create_kmalloc_pool( 254 SWAP_CLUSTER_MAX, sizeof(struct swap_iocb)); 255 if (cmpxchg(&sio_pool, NULL, pool)) 256 mempool_destroy(pool); 257 } 258 if (!sio_pool) 259 return -ENOMEM; 260 return 0; 261 } 262 263 static void sio_write_complete(struct kiocb *iocb, long ret) 264 { 265 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb); 266 struct page *page = sio->bvec[0].bv_page; 267 int p; 268 269 if (ret != sio->len) { 270 /* 271 * In the case of swap-over-nfs, this can be a 272 * temporary failure if the system has limited 273 * memory for allocating transmit buffers. 274 * Mark the page dirty and avoid 275 * folio_rotate_reclaimable but rate-limit the 276 * messages but do not flag PageError like 277 * the normal direct-to-bio case as it could 278 * be temporary. 279 */ 280 pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n", 281 ret, swap_dev_pos(page_swap_entry(page))); 282 for (p = 0; p < sio->pages; p++) { 283 page = sio->bvec[p].bv_page; 284 set_page_dirty(page); 285 ClearPageReclaim(page); 286 } 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 void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc) 296 { 297 struct swap_iocb *sio = NULL; 298 struct swap_info_struct *sis = swp_swap_info(folio->swap); 299 struct file *swap_file = sis->swap_file; 300 loff_t pos = swap_dev_pos(folio->swap); 301 302 count_swpout_vm_event(folio); 303 folio_start_writeback(folio); 304 folio_unlock(folio); 305 if (wbc->swap_plug) 306 sio = *wbc->swap_plug; 307 if (sio) { 308 if (sio->iocb.ki_filp != swap_file || 309 sio->iocb.ki_pos + sio->len != pos) { 310 swap_write_unplug(sio); 311 sio = NULL; 312 } 313 } 314 if (!sio) { 315 sio = mempool_alloc(sio_pool, GFP_NOIO); 316 init_sync_kiocb(&sio->iocb, swap_file); 317 sio->iocb.ki_complete = sio_write_complete; 318 sio->iocb.ki_pos = pos; 319 sio->pages = 0; 320 sio->len = 0; 321 } 322 bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0); 323 sio->len += folio_size(folio); 324 sio->pages += 1; 325 if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) { 326 swap_write_unplug(sio); 327 sio = NULL; 328 } 329 if (wbc->swap_plug) 330 *wbc->swap_plug = sio; 331 } 332 333 static void swap_writepage_bdev_sync(struct folio *folio, 334 struct writeback_control *wbc, struct swap_info_struct *sis) 335 { 336 struct bio_vec bv; 337 struct bio bio; 338 339 bio_init(&bio, sis->bdev, &bv, 1, 340 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc)); 341 bio.bi_iter.bi_sector = swap_folio_sector(folio); 342 bio_add_folio_nofail(&bio, folio, folio_size(folio), 0); 343 344 bio_associate_blkg_from_page(&bio, folio); 345 count_swpout_vm_event(folio); 346 347 folio_start_writeback(folio); 348 folio_unlock(folio); 349 350 submit_bio_wait(&bio); 351 __end_swap_bio_write(&bio); 352 } 353 354 static void swap_writepage_bdev_async(struct folio *folio, 355 struct writeback_control *wbc, struct swap_info_struct *sis) 356 { 357 struct bio *bio; 358 359 bio = bio_alloc(sis->bdev, 1, 360 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc), 361 GFP_NOIO); 362 bio->bi_iter.bi_sector = swap_folio_sector(folio); 363 bio->bi_end_io = end_swap_bio_write; 364 bio_add_folio_nofail(bio, folio, folio_size(folio), 0); 365 366 bio_associate_blkg_from_page(bio, folio); 367 count_swpout_vm_event(folio); 368 folio_start_writeback(folio); 369 folio_unlock(folio); 370 submit_bio(bio); 371 } 372 373 void __swap_writepage(struct folio *folio, struct writeback_control *wbc) 374 { 375 struct swap_info_struct *sis = swp_swap_info(folio->swap); 376 377 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio); 378 /* 379 * ->flags can be updated non-atomicially (scan_swap_map_slots), 380 * but that will never affect SWP_FS_OPS, so the data_race 381 * is safe. 382 */ 383 if (data_race(sis->flags & SWP_FS_OPS)) 384 swap_writepage_fs(folio, wbc); 385 /* 386 * ->flags can be updated non-atomicially (scan_swap_map_slots), 387 * but that will never affect SWP_SYNCHRONOUS_IO, so the data_race 388 * is safe. 389 */ 390 else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO)) 391 swap_writepage_bdev_sync(folio, wbc, sis); 392 else 393 swap_writepage_bdev_async(folio, wbc, sis); 394 } 395 396 void swap_write_unplug(struct swap_iocb *sio) 397 { 398 struct iov_iter from; 399 struct address_space *mapping = sio->iocb.ki_filp->f_mapping; 400 int ret; 401 402 iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len); 403 ret = mapping->a_ops->swap_rw(&sio->iocb, &from); 404 if (ret != -EIOCBQUEUED) 405 sio_write_complete(&sio->iocb, ret); 406 } 407 408 static void sio_read_complete(struct kiocb *iocb, long ret) 409 { 410 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb); 411 int p; 412 413 if (ret == sio->len) { 414 for (p = 0; p < sio->pages; p++) { 415 struct folio *folio = page_folio(sio->bvec[p].bv_page); 416 417 folio_mark_uptodate(folio); 418 folio_unlock(folio); 419 } 420 count_vm_events(PSWPIN, sio->pages); 421 } else { 422 for (p = 0; p < sio->pages; p++) { 423 struct folio *folio = page_folio(sio->bvec[p].bv_page); 424 425 folio_unlock(folio); 426 } 427 pr_alert_ratelimited("Read-error on swap-device\n"); 428 } 429 mempool_free(sio, sio_pool); 430 } 431 432 static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug) 433 { 434 struct swap_info_struct *sis = swp_swap_info(folio->swap); 435 struct swap_iocb *sio = NULL; 436 loff_t pos = swap_dev_pos(folio->swap); 437 438 if (plug) 439 sio = *plug; 440 if (sio) { 441 if (sio->iocb.ki_filp != sis->swap_file || 442 sio->iocb.ki_pos + sio->len != pos) { 443 swap_read_unplug(sio); 444 sio = NULL; 445 } 446 } 447 if (!sio) { 448 sio = mempool_alloc(sio_pool, GFP_KERNEL); 449 init_sync_kiocb(&sio->iocb, sis->swap_file); 450 sio->iocb.ki_pos = pos; 451 sio->iocb.ki_complete = sio_read_complete; 452 sio->pages = 0; 453 sio->len = 0; 454 } 455 bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0); 456 sio->len += folio_size(folio); 457 sio->pages += 1; 458 if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) { 459 swap_read_unplug(sio); 460 sio = NULL; 461 } 462 if (plug) 463 *plug = sio; 464 } 465 466 static void swap_read_folio_bdev_sync(struct folio *folio, 467 struct swap_info_struct *sis) 468 { 469 struct bio_vec bv; 470 struct bio bio; 471 472 bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ); 473 bio.bi_iter.bi_sector = swap_folio_sector(folio); 474 bio_add_folio_nofail(&bio, folio, folio_size(folio), 0); 475 /* 476 * Keep this task valid during swap readpage because the oom killer may 477 * attempt to access it in the page fault retry time check. 478 */ 479 get_task_struct(current); 480 count_vm_event(PSWPIN); 481 submit_bio_wait(&bio); 482 __end_swap_bio_read(&bio); 483 put_task_struct(current); 484 } 485 486 static void swap_read_folio_bdev_async(struct folio *folio, 487 struct swap_info_struct *sis) 488 { 489 struct bio *bio; 490 491 bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL); 492 bio->bi_iter.bi_sector = swap_folio_sector(folio); 493 bio->bi_end_io = end_swap_bio_read; 494 bio_add_folio_nofail(bio, folio, folio_size(folio), 0); 495 count_vm_event(PSWPIN); 496 submit_bio(bio); 497 } 498 499 void swap_read_folio(struct folio *folio, struct swap_iocb **plug) 500 { 501 struct swap_info_struct *sis = swp_swap_info(folio->swap); 502 bool synchronous = sis->flags & SWP_SYNCHRONOUS_IO; 503 bool workingset = folio_test_workingset(folio); 504 unsigned long pflags; 505 bool in_thrashing; 506 507 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio); 508 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); 509 VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio); 510 511 /* 512 * Count submission time as memory stall and delay. When the device 513 * is congested, or the submitting cgroup IO-throttled, submission 514 * can be a significant part of overall IO time. 515 */ 516 if (workingset) { 517 delayacct_thrashing_start(&in_thrashing); 518 psi_memstall_enter(&pflags); 519 } 520 delayacct_swapin_start(); 521 522 if (zswap_load(folio)) { 523 folio_unlock(folio); 524 } else if (data_race(sis->flags & SWP_FS_OPS)) { 525 swap_read_folio_fs(folio, plug); 526 } else if (synchronous) { 527 swap_read_folio_bdev_sync(folio, sis); 528 } else { 529 swap_read_folio_bdev_async(folio, sis); 530 } 531 532 if (workingset) { 533 delayacct_thrashing_end(&in_thrashing); 534 psi_memstall_leave(&pflags); 535 } 536 delayacct_swapin_end(); 537 } 538 539 void __swap_read_unplug(struct swap_iocb *sio) 540 { 541 struct iov_iter from; 542 struct address_space *mapping = sio->iocb.ki_filp->f_mapping; 543 int ret; 544 545 iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len); 546 ret = mapping->a_ops->swap_rw(&sio->iocb, &from); 547 if (ret != -EIOCBQUEUED) 548 sio_read_complete(&sio->iocb, ret); 549 } 550