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 folio_rotate_reclaimable() 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 swap_slot_free_notify(struct page *page) 54 { 55 struct swap_info_struct *sis; 56 struct gendisk *disk; 57 swp_entry_t entry; 58 59 /* 60 * There is no guarantee that the page is in swap cache - the software 61 * suspend code (at least) uses end_swap_bio_read() against a non- 62 * swapcache page. So we must check PG_swapcache before proceeding with 63 * this optimization. 64 */ 65 if (unlikely(!PageSwapCache(page))) 66 return; 67 68 sis = page_swap_info(page); 69 if (data_race(!(sis->flags & SWP_BLKDEV))) 70 return; 71 72 /* 73 * The swap subsystem performs lazy swap slot freeing, 74 * expecting that the page will be swapped out again. 75 * So we can avoid an unnecessary write if the page 76 * isn't redirtied. 77 * This is good for real swap storage because we can 78 * reduce unnecessary I/O and enhance wear-leveling 79 * if an SSD is used as the as swap device. 80 * But if in-memory swap device (eg zram) is used, 81 * this causes a duplicated copy between uncompressed 82 * data in VM-owned memory and compressed data in 83 * zram-owned memory. So let's free zram-owned memory 84 * and make the VM-owned decompressed page *dirty*, 85 * so the page should be swapped out somewhere again if 86 * we again wish to reclaim it. 87 */ 88 disk = sis->bdev->bd_disk; 89 entry.val = page_private(page); 90 if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) { 91 unsigned long offset; 92 93 offset = swp_offset(entry); 94 95 SetPageDirty(page); 96 disk->fops->swap_slot_free_notify(sis->bdev, 97 offset); 98 } 99 } 100 101 static void end_swap_bio_read(struct bio *bio) 102 { 103 struct page *page = bio_first_page_all(bio); 104 struct task_struct *waiter = bio->bi_private; 105 106 if (bio->bi_status) { 107 SetPageError(page); 108 ClearPageUptodate(page); 109 pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n", 110 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)), 111 (unsigned long long)bio->bi_iter.bi_sector); 112 goto out; 113 } 114 115 SetPageUptodate(page); 116 swap_slot_free_notify(page); 117 out: 118 unlock_page(page); 119 WRITE_ONCE(bio->bi_private, NULL); 120 bio_put(bio); 121 if (waiter) { 122 blk_wake_io_task(waiter); 123 put_task_struct(waiter); 124 } 125 } 126 127 int generic_swapfile_activate(struct swap_info_struct *sis, 128 struct file *swap_file, 129 sector_t *span) 130 { 131 struct address_space *mapping = swap_file->f_mapping; 132 struct inode *inode = mapping->host; 133 unsigned blocks_per_page; 134 unsigned long page_no; 135 unsigned blkbits; 136 sector_t probe_block; 137 sector_t last_block; 138 sector_t lowest_block = -1; 139 sector_t highest_block = 0; 140 int nr_extents = 0; 141 int ret; 142 143 blkbits = inode->i_blkbits; 144 blocks_per_page = PAGE_SIZE >> blkbits; 145 146 /* 147 * Map all the blocks into the extent tree. This code doesn't try 148 * to be very smart. 149 */ 150 probe_block = 0; 151 page_no = 0; 152 last_block = i_size_read(inode) >> blkbits; 153 while ((probe_block + blocks_per_page) <= last_block && 154 page_no < sis->max) { 155 unsigned block_in_page; 156 sector_t first_block; 157 158 cond_resched(); 159 160 first_block = probe_block; 161 ret = bmap(inode, &first_block); 162 if (ret || !first_block) 163 goto bad_bmap; 164 165 /* 166 * It must be PAGE_SIZE aligned on-disk 167 */ 168 if (first_block & (blocks_per_page - 1)) { 169 probe_block++; 170 goto reprobe; 171 } 172 173 for (block_in_page = 1; block_in_page < blocks_per_page; 174 block_in_page++) { 175 sector_t block; 176 177 block = probe_block + block_in_page; 178 ret = bmap(inode, &block); 179 if (ret || !block) 180 goto bad_bmap; 181 182 if (block != first_block + block_in_page) { 183 /* Discontiguity */ 184 probe_block++; 185 goto reprobe; 186 } 187 } 188 189 first_block >>= (PAGE_SHIFT - blkbits); 190 if (page_no) { /* exclude the header page */ 191 if (first_block < lowest_block) 192 lowest_block = first_block; 193 if (first_block > highest_block) 194 highest_block = first_block; 195 } 196 197 /* 198 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 199 */ 200 ret = add_swap_extent(sis, page_no, 1, first_block); 201 if (ret < 0) 202 goto out; 203 nr_extents += ret; 204 page_no++; 205 probe_block += blocks_per_page; 206 reprobe: 207 continue; 208 } 209 ret = nr_extents; 210 *span = 1 + highest_block - lowest_block; 211 if (page_no == 0) 212 page_no = 1; /* force Empty message */ 213 sis->max = page_no; 214 sis->pages = page_no - 1; 215 sis->highest_bit = page_no - 1; 216 out: 217 return ret; 218 bad_bmap: 219 pr_err("swapon: swapfile has holes\n"); 220 ret = -EINVAL; 221 goto out; 222 } 223 224 /* 225 * We may have stale swap cache pages in memory: notice 226 * them here and get rid of the unnecessary final write. 227 */ 228 int swap_writepage(struct page *page, struct writeback_control *wbc) 229 { 230 int ret = 0; 231 232 if (try_to_free_swap(page)) { 233 unlock_page(page); 234 goto out; 235 } 236 /* 237 * Arch code may have to preserve more data than just the page 238 * contents, e.g. memory tags. 239 */ 240 ret = arch_prepare_to_swap(page); 241 if (ret) { 242 set_page_dirty(page); 243 unlock_page(page); 244 goto out; 245 } 246 if (frontswap_store(page) == 0) { 247 set_page_writeback(page); 248 unlock_page(page); 249 end_page_writeback(page); 250 goto out; 251 } 252 ret = __swap_writepage(page, wbc, end_swap_bio_write); 253 out: 254 return ret; 255 } 256 257 static inline void count_swpout_vm_event(struct page *page) 258 { 259 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 260 if (unlikely(PageTransHuge(page))) 261 count_vm_event(THP_SWPOUT); 262 #endif 263 count_vm_events(PSWPOUT, thp_nr_pages(page)); 264 } 265 266 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) 267 static void bio_associate_blkg_from_page(struct bio *bio, struct page *page) 268 { 269 struct cgroup_subsys_state *css; 270 struct mem_cgroup *memcg; 271 272 memcg = page_memcg(page); 273 if (!memcg) 274 return; 275 276 rcu_read_lock(); 277 css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys); 278 bio_associate_blkg_from_css(bio, css); 279 rcu_read_unlock(); 280 } 281 #else 282 #define bio_associate_blkg_from_page(bio, page) do { } while (0) 283 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */ 284 285 int __swap_writepage(struct page *page, struct writeback_control *wbc, 286 bio_end_io_t end_write_func) 287 { 288 struct bio *bio; 289 int ret; 290 struct swap_info_struct *sis = page_swap_info(page); 291 292 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 293 if (data_race(sis->flags & SWP_FS_OPS)) { 294 struct kiocb kiocb; 295 struct file *swap_file = sis->swap_file; 296 struct address_space *mapping = swap_file->f_mapping; 297 struct bio_vec bv = { 298 .bv_page = page, 299 .bv_len = PAGE_SIZE, 300 .bv_offset = 0 301 }; 302 struct iov_iter from; 303 304 iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE); 305 init_sync_kiocb(&kiocb, swap_file); 306 kiocb.ki_pos = page_file_offset(page); 307 308 set_page_writeback(page); 309 unlock_page(page); 310 ret = mapping->a_ops->direct_IO(&kiocb, &from); 311 if (ret == PAGE_SIZE) { 312 count_vm_event(PSWPOUT); 313 ret = 0; 314 } else { 315 /* 316 * In the case of swap-over-nfs, this can be a 317 * temporary failure if the system has limited 318 * memory for allocating transmit buffers. 319 * Mark the page dirty and avoid 320 * folio_rotate_reclaimable but rate-limit the 321 * messages but do not flag PageError like 322 * the normal direct-to-bio case as it could 323 * be temporary. 324 */ 325 set_page_dirty(page); 326 ClearPageReclaim(page); 327 pr_err_ratelimited("Write error on dio swapfile (%llu)\n", 328 page_file_offset(page)); 329 } 330 end_page_writeback(page); 331 return ret; 332 } 333 334 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); 335 if (!ret) { 336 count_swpout_vm_event(page); 337 return 0; 338 } 339 340 bio = bio_alloc(GFP_NOIO, 1); 341 bio_set_dev(bio, sis->bdev); 342 bio->bi_iter.bi_sector = swap_page_sector(page); 343 bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc); 344 bio->bi_end_io = end_write_func; 345 bio_add_page(bio, page, thp_size(page), 0); 346 347 bio_associate_blkg_from_page(bio, page); 348 count_swpout_vm_event(page); 349 set_page_writeback(page); 350 unlock_page(page); 351 submit_bio(bio); 352 353 return 0; 354 } 355 356 int swap_readpage(struct page *page, bool synchronous) 357 { 358 struct bio *bio; 359 int ret = 0; 360 struct swap_info_struct *sis = page_swap_info(page); 361 unsigned long pflags; 362 363 VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page); 364 VM_BUG_ON_PAGE(!PageLocked(page), page); 365 VM_BUG_ON_PAGE(PageUptodate(page), page); 366 367 /* 368 * Count submission time as memory stall. When the device is congested, 369 * or the submitting cgroup IO-throttled, submission can be a 370 * significant part of overall IO time. 371 */ 372 psi_memstall_enter(&pflags); 373 374 if (frontswap_load(page) == 0) { 375 SetPageUptodate(page); 376 unlock_page(page); 377 goto out; 378 } 379 380 if (data_race(sis->flags & SWP_FS_OPS)) { 381 struct file *swap_file = sis->swap_file; 382 struct address_space *mapping = swap_file->f_mapping; 383 384 ret = mapping->a_ops->readpage(swap_file, page); 385 if (!ret) 386 count_vm_event(PSWPIN); 387 goto out; 388 } 389 390 if (sis->flags & SWP_SYNCHRONOUS_IO) { 391 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); 392 if (!ret) { 393 if (trylock_page(page)) { 394 swap_slot_free_notify(page); 395 unlock_page(page); 396 } 397 398 count_vm_event(PSWPIN); 399 goto out; 400 } 401 } 402 403 ret = 0; 404 bio = bio_alloc(GFP_KERNEL, 1); 405 bio_set_dev(bio, sis->bdev); 406 bio->bi_opf = REQ_OP_READ; 407 bio->bi_iter.bi_sector = swap_page_sector(page); 408 bio->bi_end_io = end_swap_bio_read; 409 bio_add_page(bio, page, thp_size(page), 0); 410 /* 411 * Keep this task valid during swap readpage because the oom killer may 412 * attempt to access it in the page fault retry time check. 413 */ 414 if (synchronous) { 415 bio->bi_opf |= REQ_POLLED; 416 get_task_struct(current); 417 bio->bi_private = current; 418 } 419 count_vm_event(PSWPIN); 420 bio_get(bio); 421 submit_bio(bio); 422 while (synchronous) { 423 set_current_state(TASK_UNINTERRUPTIBLE); 424 if (!READ_ONCE(bio->bi_private)) 425 break; 426 427 if (!bio_poll(bio, NULL, 0)) 428 blk_io_schedule(); 429 } 430 __set_current_state(TASK_RUNNING); 431 bio_put(bio); 432 433 out: 434 psi_memstall_leave(&pflags); 435 return ret; 436 } 437 438 int swap_set_page_dirty(struct page *page) 439 { 440 struct swap_info_struct *sis = page_swap_info(page); 441 442 if (data_race(sis->flags & SWP_FS_OPS)) { 443 struct address_space *mapping = sis->swap_file->f_mapping; 444 445 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 446 return mapping->a_ops->set_page_dirty(page); 447 } else { 448 return __set_page_dirty_no_writeback(page); 449 } 450 } 451