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 static struct bio *get_swap_bio(gfp_t gfp_flags, 30 struct page *page, bio_end_io_t end_io) 31 { 32 struct bio *bio; 33 34 bio = bio_alloc(gfp_flags, 1); 35 if (bio) { 36 struct block_device *bdev; 37 38 bio->bi_iter.bi_sector = map_swap_page(page, &bdev); 39 bio_set_dev(bio, bdev); 40 bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; 41 bio->bi_end_io = end_io; 42 43 bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0); 44 } 45 return bio; 46 } 47 48 void end_swap_bio_write(struct bio *bio) 49 { 50 struct page *page = bio_first_page_all(bio); 51 52 if (bio->bi_status) { 53 SetPageError(page); 54 /* 55 * We failed to write the page out to swap-space. 56 * Re-dirty the page in order to avoid it being reclaimed. 57 * Also print a dire warning that things will go BAD (tm) 58 * very quickly. 59 * 60 * Also clear PG_reclaim to avoid rotate_reclaimable_page() 61 */ 62 set_page_dirty(page); 63 pr_alert("Write-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 ClearPageReclaim(page); 67 } 68 end_page_writeback(page); 69 bio_put(bio); 70 } 71 72 static void swap_slot_free_notify(struct page *page) 73 { 74 struct swap_info_struct *sis; 75 struct gendisk *disk; 76 swp_entry_t entry; 77 78 /* 79 * There is no guarantee that the page is in swap cache - the software 80 * suspend code (at least) uses end_swap_bio_read() against a non- 81 * swapcache page. So we must check PG_swapcache before proceeding with 82 * this optimization. 83 */ 84 if (unlikely(!PageSwapCache(page))) 85 return; 86 87 sis = page_swap_info(page); 88 if (!(sis->flags & SWP_BLKDEV)) 89 return; 90 91 /* 92 * The swap subsystem performs lazy swap slot freeing, 93 * expecting that the page will be swapped out again. 94 * So we can avoid an unnecessary write if the page 95 * isn't redirtied. 96 * This is good for real swap storage because we can 97 * reduce unnecessary I/O and enhance wear-leveling 98 * if an SSD is used as the as swap device. 99 * But if in-memory swap device (eg zram) is used, 100 * this causes a duplicated copy between uncompressed 101 * data in VM-owned memory and compressed data in 102 * zram-owned memory. So let's free zram-owned memory 103 * and make the VM-owned decompressed page *dirty*, 104 * so the page should be swapped out somewhere again if 105 * we again wish to reclaim it. 106 */ 107 disk = sis->bdev->bd_disk; 108 entry.val = page_private(page); 109 if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) { 110 unsigned long offset; 111 112 offset = swp_offset(entry); 113 114 SetPageDirty(page); 115 disk->fops->swap_slot_free_notify(sis->bdev, 116 offset); 117 } 118 } 119 120 static void end_swap_bio_read(struct bio *bio) 121 { 122 struct page *page = bio_first_page_all(bio); 123 struct task_struct *waiter = bio->bi_private; 124 125 if (bio->bi_status) { 126 SetPageError(page); 127 ClearPageUptodate(page); 128 pr_alert("Read-error on swap-device (%u:%u:%llu)\n", 129 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)), 130 (unsigned long long)bio->bi_iter.bi_sector); 131 goto out; 132 } 133 134 SetPageUptodate(page); 135 swap_slot_free_notify(page); 136 out: 137 unlock_page(page); 138 WRITE_ONCE(bio->bi_private, NULL); 139 bio_put(bio); 140 if (waiter) { 141 blk_wake_io_task(waiter); 142 put_task_struct(waiter); 143 } 144 } 145 146 int generic_swapfile_activate(struct swap_info_struct *sis, 147 struct file *swap_file, 148 sector_t *span) 149 { 150 struct address_space *mapping = swap_file->f_mapping; 151 struct inode *inode = mapping->host; 152 unsigned blocks_per_page; 153 unsigned long page_no; 154 unsigned blkbits; 155 sector_t probe_block; 156 sector_t last_block; 157 sector_t lowest_block = -1; 158 sector_t highest_block = 0; 159 int nr_extents = 0; 160 int ret; 161 162 blkbits = inode->i_blkbits; 163 blocks_per_page = PAGE_SIZE >> blkbits; 164 165 /* 166 * Map all the blocks into the extent tree. This code doesn't try 167 * to be very smart. 168 */ 169 probe_block = 0; 170 page_no = 0; 171 last_block = i_size_read(inode) >> blkbits; 172 while ((probe_block + blocks_per_page) <= last_block && 173 page_no < sis->max) { 174 unsigned block_in_page; 175 sector_t first_block; 176 177 cond_resched(); 178 179 first_block = probe_block; 180 ret = bmap(inode, &first_block); 181 if (ret || !first_block) 182 goto bad_bmap; 183 184 /* 185 * It must be PAGE_SIZE aligned on-disk 186 */ 187 if (first_block & (blocks_per_page - 1)) { 188 probe_block++; 189 goto reprobe; 190 } 191 192 for (block_in_page = 1; block_in_page < blocks_per_page; 193 block_in_page++) { 194 sector_t block; 195 196 block = probe_block + block_in_page; 197 ret = bmap(inode, &block); 198 if (ret || !block) 199 goto bad_bmap; 200 201 if (block != first_block + block_in_page) { 202 /* Discontiguity */ 203 probe_block++; 204 goto reprobe; 205 } 206 } 207 208 first_block >>= (PAGE_SHIFT - blkbits); 209 if (page_no) { /* exclude the header page */ 210 if (first_block < lowest_block) 211 lowest_block = first_block; 212 if (first_block > highest_block) 213 highest_block = first_block; 214 } 215 216 /* 217 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 218 */ 219 ret = add_swap_extent(sis, page_no, 1, first_block); 220 if (ret < 0) 221 goto out; 222 nr_extents += ret; 223 page_no++; 224 probe_block += blocks_per_page; 225 reprobe: 226 continue; 227 } 228 ret = nr_extents; 229 *span = 1 + highest_block - lowest_block; 230 if (page_no == 0) 231 page_no = 1; /* force Empty message */ 232 sis->max = page_no; 233 sis->pages = page_no - 1; 234 sis->highest_bit = page_no - 1; 235 out: 236 return ret; 237 bad_bmap: 238 pr_err("swapon: swapfile has holes\n"); 239 ret = -EINVAL; 240 goto out; 241 } 242 243 /* 244 * We may have stale swap cache pages in memory: notice 245 * them here and get rid of the unnecessary final write. 246 */ 247 int swap_writepage(struct page *page, struct writeback_control *wbc) 248 { 249 int ret = 0; 250 251 if (try_to_free_swap(page)) { 252 unlock_page(page); 253 goto out; 254 } 255 if (frontswap_store(page) == 0) { 256 set_page_writeback(page); 257 unlock_page(page); 258 end_page_writeback(page); 259 goto out; 260 } 261 ret = __swap_writepage(page, wbc, end_swap_bio_write); 262 out: 263 return ret; 264 } 265 266 static sector_t swap_page_sector(struct page *page) 267 { 268 return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9); 269 } 270 271 static inline void count_swpout_vm_event(struct page *page) 272 { 273 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 274 if (unlikely(PageTransHuge(page))) 275 count_vm_event(THP_SWPOUT); 276 #endif 277 count_vm_events(PSWPOUT, hpage_nr_pages(page)); 278 } 279 280 int __swap_writepage(struct page *page, struct writeback_control *wbc, 281 bio_end_io_t end_write_func) 282 { 283 struct bio *bio; 284 int ret; 285 struct swap_info_struct *sis = page_swap_info(page); 286 287 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 288 if (sis->flags & SWP_FS) { 289 struct kiocb kiocb; 290 struct file *swap_file = sis->swap_file; 291 struct address_space *mapping = swap_file->f_mapping; 292 struct bio_vec bv = { 293 .bv_page = page, 294 .bv_len = PAGE_SIZE, 295 .bv_offset = 0 296 }; 297 struct iov_iter from; 298 299 iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE); 300 init_sync_kiocb(&kiocb, swap_file); 301 kiocb.ki_pos = page_file_offset(page); 302 303 set_page_writeback(page); 304 unlock_page(page); 305 ret = mapping->a_ops->direct_IO(&kiocb, &from); 306 if (ret == PAGE_SIZE) { 307 count_vm_event(PSWPOUT); 308 ret = 0; 309 } else { 310 /* 311 * In the case of swap-over-nfs, this can be a 312 * temporary failure if the system has limited 313 * memory for allocating transmit buffers. 314 * Mark the page dirty and avoid 315 * rotate_reclaimable_page but rate-limit the 316 * messages but do not flag PageError like 317 * the normal direct-to-bio case as it could 318 * be temporary. 319 */ 320 set_page_dirty(page); 321 ClearPageReclaim(page); 322 pr_err_ratelimited("Write error on dio swapfile (%llu)\n", 323 page_file_offset(page)); 324 } 325 end_page_writeback(page); 326 return ret; 327 } 328 329 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); 330 if (!ret) { 331 count_swpout_vm_event(page); 332 return 0; 333 } 334 335 ret = 0; 336 bio = get_swap_bio(GFP_NOIO, page, end_write_func); 337 if (bio == NULL) { 338 set_page_dirty(page); 339 unlock_page(page); 340 ret = -ENOMEM; 341 goto out; 342 } 343 bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc); 344 bio_associate_blkg_from_page(bio, page); 345 count_swpout_vm_event(page); 346 set_page_writeback(page); 347 unlock_page(page); 348 submit_bio(bio); 349 out: 350 return ret; 351 } 352 353 int swap_readpage(struct page *page, bool synchronous) 354 { 355 struct bio *bio; 356 int ret = 0; 357 struct swap_info_struct *sis = page_swap_info(page); 358 blk_qc_t qc; 359 struct gendisk *disk; 360 unsigned long pflags; 361 362 VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page); 363 VM_BUG_ON_PAGE(!PageLocked(page), page); 364 VM_BUG_ON_PAGE(PageUptodate(page), page); 365 366 /* 367 * Count submission time as memory stall. When the device is congested, 368 * or the submitting cgroup IO-throttled, submission can be a 369 * significant part of overall IO time. 370 */ 371 psi_memstall_enter(&pflags); 372 373 if (frontswap_load(page) == 0) { 374 SetPageUptodate(page); 375 unlock_page(page); 376 goto out; 377 } 378 379 if (sis->flags & SWP_FS) { 380 struct file *swap_file = sis->swap_file; 381 struct address_space *mapping = swap_file->f_mapping; 382 383 ret = mapping->a_ops->readpage(swap_file, page); 384 if (!ret) 385 count_vm_event(PSWPIN); 386 goto out; 387 } 388 389 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); 390 if (!ret) { 391 if (trylock_page(page)) { 392 swap_slot_free_notify(page); 393 unlock_page(page); 394 } 395 396 count_vm_event(PSWPIN); 397 goto out; 398 } 399 400 ret = 0; 401 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); 402 if (bio == NULL) { 403 unlock_page(page); 404 ret = -ENOMEM; 405 goto out; 406 } 407 disk = bio->bi_disk; 408 /* 409 * Keep this task valid during swap readpage because the oom killer may 410 * attempt to access it in the page fault retry time check. 411 */ 412 bio_set_op_attrs(bio, REQ_OP_READ, 0); 413 if (synchronous) { 414 bio->bi_opf |= REQ_HIPRI; 415 get_task_struct(current); 416 bio->bi_private = current; 417 } 418 count_vm_event(PSWPIN); 419 bio_get(bio); 420 qc = submit_bio(bio); 421 while (synchronous) { 422 set_current_state(TASK_UNINTERRUPTIBLE); 423 if (!READ_ONCE(bio->bi_private)) 424 break; 425 426 if (!blk_poll(disk->queue, qc, true)) 427 io_schedule(); 428 } 429 __set_current_state(TASK_RUNNING); 430 bio_put(bio); 431 432 out: 433 psi_memstall_leave(&pflags); 434 return ret; 435 } 436 437 int swap_set_page_dirty(struct page *page) 438 { 439 struct swap_info_struct *sis = page_swap_info(page); 440 441 if (sis->flags & SWP_FS) { 442 struct address_space *mapping = sis->swap_file->f_mapping; 443 444 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 445 return mapping->a_ops->set_page_dirty(page); 446 } else { 447 return __set_page_dirty_no_writeback(page); 448 } 449 } 450