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->page); 193 if (ret) { 194 folio_mark_dirty(folio); 195 folio_unlock(folio); 196 return ret; 197 } 198 if (zswap_store(folio)) { 199 folio_start_writeback(folio); 200 folio_unlock(folio); 201 folio_end_writeback(folio); 202 return 0; 203 } 204 __swap_writepage(&folio->page, wbc); 205 return 0; 206 } 207 208 static inline void count_swpout_vm_event(struct folio *folio) 209 { 210 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 211 if (unlikely(folio_test_pmd_mappable(folio))) 212 count_vm_event(THP_SWPOUT); 213 #endif 214 count_vm_events(PSWPOUT, folio_nr_pages(folio)); 215 } 216 217 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) 218 static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio) 219 { 220 struct cgroup_subsys_state *css; 221 struct mem_cgroup *memcg; 222 223 memcg = folio_memcg(folio); 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, folio) do { } while (0) 234 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */ 235 236 struct swap_iocb { 237 struct kiocb iocb; 238 struct bio_vec bvec[SWAP_CLUSTER_MAX]; 239 int pages; 240 int len; 241 }; 242 static mempool_t *sio_pool; 243 244 int sio_pool_init(void) 245 { 246 if (!sio_pool) { 247 mempool_t *pool = mempool_create_kmalloc_pool( 248 SWAP_CLUSTER_MAX, sizeof(struct swap_iocb)); 249 if (cmpxchg(&sio_pool, NULL, pool)) 250 mempool_destroy(pool); 251 } 252 if (!sio_pool) 253 return -ENOMEM; 254 return 0; 255 } 256 257 static void sio_write_complete(struct kiocb *iocb, long ret) 258 { 259 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb); 260 struct page *page = sio->bvec[0].bv_page; 261 int p; 262 263 if (ret != sio->len) { 264 /* 265 * In the case of swap-over-nfs, this can be a 266 * temporary failure if the system has limited 267 * memory for allocating transmit buffers. 268 * Mark the page dirty and avoid 269 * folio_rotate_reclaimable but rate-limit the 270 * messages but do not flag PageError like 271 * the normal direct-to-bio case as it could 272 * be temporary. 273 */ 274 pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n", 275 ret, page_file_offset(page)); 276 for (p = 0; p < sio->pages; p++) { 277 page = sio->bvec[p].bv_page; 278 set_page_dirty(page); 279 ClearPageReclaim(page); 280 } 281 } else { 282 for (p = 0; p < sio->pages; p++) 283 count_swpout_vm_event(page_folio(sio->bvec[p].bv_page)); 284 } 285 286 for (p = 0; p < sio->pages; p++) 287 end_page_writeback(sio->bvec[p].bv_page); 288 289 mempool_free(sio, sio_pool); 290 } 291 292 static void swap_writepage_fs(struct page *page, struct writeback_control *wbc) 293 { 294 struct swap_iocb *sio = NULL; 295 struct swap_info_struct *sis = page_swap_info(page); 296 struct file *swap_file = sis->swap_file; 297 loff_t pos = page_file_offset(page); 298 299 set_page_writeback(page); 300 unlock_page(page); 301 if (wbc->swap_plug) 302 sio = *wbc->swap_plug; 303 if (sio) { 304 if (sio->iocb.ki_filp != swap_file || 305 sio->iocb.ki_pos + sio->len != pos) { 306 swap_write_unplug(sio); 307 sio = NULL; 308 } 309 } 310 if (!sio) { 311 sio = mempool_alloc(sio_pool, GFP_NOIO); 312 init_sync_kiocb(&sio->iocb, swap_file); 313 sio->iocb.ki_complete = sio_write_complete; 314 sio->iocb.ki_pos = pos; 315 sio->pages = 0; 316 sio->len = 0; 317 } 318 bvec_set_page(&sio->bvec[sio->pages], page, thp_size(page), 0); 319 sio->len += thp_size(page); 320 sio->pages += 1; 321 if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) { 322 swap_write_unplug(sio); 323 sio = NULL; 324 } 325 if (wbc->swap_plug) 326 *wbc->swap_plug = sio; 327 } 328 329 static void swap_writepage_bdev_sync(struct page *page, 330 struct writeback_control *wbc, struct swap_info_struct *sis) 331 { 332 struct bio_vec bv; 333 struct bio bio; 334 struct folio *folio = page_folio(page); 335 336 bio_init(&bio, sis->bdev, &bv, 1, 337 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc)); 338 bio.bi_iter.bi_sector = swap_page_sector(page); 339 __bio_add_page(&bio, page, thp_size(page), 0); 340 341 bio_associate_blkg_from_page(&bio, folio); 342 count_swpout_vm_event(folio); 343 344 folio_start_writeback(folio); 345 folio_unlock(folio); 346 347 submit_bio_wait(&bio); 348 __end_swap_bio_write(&bio); 349 } 350 351 static void swap_writepage_bdev_async(struct page *page, 352 struct writeback_control *wbc, struct swap_info_struct *sis) 353 { 354 struct bio *bio; 355 struct folio *folio = page_folio(page); 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, folio); 365 count_swpout_vm_event(folio); 366 folio_start_writeback(folio); 367 folio_unlock(folio); 368 submit_bio(bio); 369 } 370 371 void __swap_writepage(struct page *page, struct writeback_control *wbc) 372 { 373 struct swap_info_struct *sis = page_swap_info(page); 374 375 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 376 /* 377 * ->flags can be updated non-atomicially (scan_swap_map_slots), 378 * but that will never affect SWP_FS_OPS, so the data_race 379 * is safe. 380 */ 381 if (data_race(sis->flags & SWP_FS_OPS)) 382 swap_writepage_fs(page, wbc); 383 else if (sis->flags & SWP_SYNCHRONOUS_IO) 384 swap_writepage_bdev_sync(page, wbc, sis); 385 else 386 swap_writepage_bdev_async(page, wbc, sis); 387 } 388 389 void swap_write_unplug(struct swap_iocb *sio) 390 { 391 struct iov_iter from; 392 struct address_space *mapping = sio->iocb.ki_filp->f_mapping; 393 int ret; 394 395 iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len); 396 ret = mapping->a_ops->swap_rw(&sio->iocb, &from); 397 if (ret != -EIOCBQUEUED) 398 sio_write_complete(&sio->iocb, ret); 399 } 400 401 static void sio_read_complete(struct kiocb *iocb, long ret) 402 { 403 struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb); 404 int p; 405 406 if (ret == sio->len) { 407 for (p = 0; p < sio->pages; p++) { 408 struct folio *folio = page_folio(sio->bvec[p].bv_page); 409 410 folio_mark_uptodate(folio); 411 folio_unlock(folio); 412 } 413 count_vm_events(PSWPIN, sio->pages); 414 } else { 415 for (p = 0; p < sio->pages; p++) { 416 struct folio *folio = page_folio(sio->bvec[p].bv_page); 417 418 folio_unlock(folio); 419 } 420 pr_alert_ratelimited("Read-error on swap-device\n"); 421 } 422 mempool_free(sio, sio_pool); 423 } 424 425 static void swap_readpage_fs(struct page *page, 426 struct swap_iocb **plug) 427 { 428 struct swap_info_struct *sis = page_swap_info(page); 429 struct swap_iocb *sio = NULL; 430 loff_t pos = page_file_offset(page); 431 432 if (plug) 433 sio = *plug; 434 if (sio) { 435 if (sio->iocb.ki_filp != sis->swap_file || 436 sio->iocb.ki_pos + sio->len != pos) { 437 swap_read_unplug(sio); 438 sio = NULL; 439 } 440 } 441 if (!sio) { 442 sio = mempool_alloc(sio_pool, GFP_KERNEL); 443 init_sync_kiocb(&sio->iocb, sis->swap_file); 444 sio->iocb.ki_pos = pos; 445 sio->iocb.ki_complete = sio_read_complete; 446 sio->pages = 0; 447 sio->len = 0; 448 } 449 bvec_set_page(&sio->bvec[sio->pages], page, thp_size(page), 0); 450 sio->len += thp_size(page); 451 sio->pages += 1; 452 if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) { 453 swap_read_unplug(sio); 454 sio = NULL; 455 } 456 if (plug) 457 *plug = sio; 458 } 459 460 static void swap_readpage_bdev_sync(struct page *page, 461 struct swap_info_struct *sis) 462 { 463 struct bio_vec bv; 464 struct bio bio; 465 466 bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ); 467 bio.bi_iter.bi_sector = swap_page_sector(page); 468 __bio_add_page(&bio, page, thp_size(page), 0); 469 /* 470 * Keep this task valid during swap readpage because the oom killer may 471 * attempt to access it in the page fault retry time check. 472 */ 473 get_task_struct(current); 474 count_vm_event(PSWPIN); 475 submit_bio_wait(&bio); 476 __end_swap_bio_read(&bio); 477 put_task_struct(current); 478 } 479 480 static void swap_readpage_bdev_async(struct page *page, 481 struct swap_info_struct *sis) 482 { 483 struct bio *bio; 484 485 bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL); 486 bio->bi_iter.bi_sector = swap_page_sector(page); 487 bio->bi_end_io = end_swap_bio_read; 488 __bio_add_page(bio, page, thp_size(page), 0); 489 count_vm_event(PSWPIN); 490 submit_bio(bio); 491 } 492 493 void swap_readpage(struct page *page, bool synchronous, struct swap_iocb **plug) 494 { 495 struct folio *folio = page_folio(page); 496 struct swap_info_struct *sis = page_swap_info(page); 497 bool workingset = folio_test_workingset(folio); 498 unsigned long pflags; 499 bool in_thrashing; 500 501 VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio); 502 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); 503 VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio); 504 505 /* 506 * Count submission time as memory stall and delay. When the device 507 * is congested, or the submitting cgroup IO-throttled, submission 508 * can be a significant part of overall IO time. 509 */ 510 if (workingset) { 511 delayacct_thrashing_start(&in_thrashing); 512 psi_memstall_enter(&pflags); 513 } 514 delayacct_swapin_start(); 515 516 if (zswap_load(folio)) { 517 folio_mark_uptodate(folio); 518 folio_unlock(folio); 519 } else if (data_race(sis->flags & SWP_FS_OPS)) { 520 swap_readpage_fs(page, plug); 521 } else if (synchronous || (sis->flags & SWP_SYNCHRONOUS_IO)) { 522 swap_readpage_bdev_sync(page, sis); 523 } else { 524 swap_readpage_bdev_async(page, sis); 525 } 526 527 if (workingset) { 528 delayacct_thrashing_end(&in_thrashing); 529 psi_memstall_leave(&pflags); 530 } 531 delayacct_swapin_end(); 532 } 533 534 void __swap_read_unplug(struct swap_iocb *sio) 535 { 536 struct iov_iter from; 537 struct address_space *mapping = sio->iocb.ki_filp->f_mapping; 538 int ret; 539 540 iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len); 541 ret = mapping->a_ops->swap_rw(&sio->iocb, &from); 542 if (ret != -EIOCBQUEUED) 543 sio_read_complete(&sio->iocb, ret); 544 } 545