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/uio.h> 26 #include <linux/sched/task.h> 27 #include <asm/pgtable.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 77 /* 78 * There is no guarantee that the page is in swap cache - the software 79 * suspend code (at least) uses end_swap_bio_read() against a non- 80 * swapcache page. So we must check PG_swapcache before proceeding with 81 * this optimization. 82 */ 83 if (unlikely(!PageSwapCache(page))) 84 return; 85 86 sis = page_swap_info(page); 87 if (!(sis->flags & SWP_BLKDEV)) 88 return; 89 90 /* 91 * The swap subsystem performs lazy swap slot freeing, 92 * expecting that the page will be swapped out again. 93 * So we can avoid an unnecessary write if the page 94 * isn't redirtied. 95 * This is good for real swap storage because we can 96 * reduce unnecessary I/O and enhance wear-leveling 97 * if an SSD is used as the as swap device. 98 * But if in-memory swap device (eg zram) is used, 99 * this causes a duplicated copy between uncompressed 100 * data in VM-owned memory and compressed data in 101 * zram-owned memory. So let's free zram-owned memory 102 * and make the VM-owned decompressed page *dirty*, 103 * so the page should be swapped out somewhere again if 104 * we again wish to reclaim it. 105 */ 106 disk = sis->bdev->bd_disk; 107 if (disk->fops->swap_slot_free_notify) { 108 swp_entry_t entry; 109 unsigned long offset; 110 111 entry.val = page_private(page); 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 = bmap(inode, probe_block); 180 if (first_block == 0) 181 goto bad_bmap; 182 183 /* 184 * It must be PAGE_SIZE aligned on-disk 185 */ 186 if (first_block & (blocks_per_page - 1)) { 187 probe_block++; 188 goto reprobe; 189 } 190 191 for (block_in_page = 1; block_in_page < blocks_per_page; 192 block_in_page++) { 193 sector_t block; 194 195 block = bmap(inode, probe_block + block_in_page); 196 if (block == 0) 197 goto bad_bmap; 198 if (block != first_block + block_in_page) { 199 /* Discontiguity */ 200 probe_block++; 201 goto reprobe; 202 } 203 } 204 205 first_block >>= (PAGE_SHIFT - blkbits); 206 if (page_no) { /* exclude the header page */ 207 if (first_block < lowest_block) 208 lowest_block = first_block; 209 if (first_block > highest_block) 210 highest_block = first_block; 211 } 212 213 /* 214 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 215 */ 216 ret = add_swap_extent(sis, page_no, 1, first_block); 217 if (ret < 0) 218 goto out; 219 nr_extents += ret; 220 page_no++; 221 probe_block += blocks_per_page; 222 reprobe: 223 continue; 224 } 225 ret = nr_extents; 226 *span = 1 + highest_block - lowest_block; 227 if (page_no == 0) 228 page_no = 1; /* force Empty message */ 229 sis->max = page_no; 230 sis->pages = page_no - 1; 231 sis->highest_bit = page_no - 1; 232 out: 233 return ret; 234 bad_bmap: 235 pr_err("swapon: swapfile has holes\n"); 236 ret = -EINVAL; 237 goto out; 238 } 239 240 /* 241 * We may have stale swap cache pages in memory: notice 242 * them here and get rid of the unnecessary final write. 243 */ 244 int swap_writepage(struct page *page, struct writeback_control *wbc) 245 { 246 int ret = 0; 247 248 if (try_to_free_swap(page)) { 249 unlock_page(page); 250 goto out; 251 } 252 if (frontswap_store(page) == 0) { 253 set_page_writeback(page); 254 unlock_page(page); 255 end_page_writeback(page); 256 goto out; 257 } 258 ret = __swap_writepage(page, wbc, end_swap_bio_write); 259 out: 260 return ret; 261 } 262 263 static sector_t swap_page_sector(struct page *page) 264 { 265 return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9); 266 } 267 268 static inline void count_swpout_vm_event(struct page *page) 269 { 270 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 271 if (unlikely(PageTransHuge(page))) 272 count_vm_event(THP_SWPOUT); 273 #endif 274 count_vm_events(PSWPOUT, hpage_nr_pages(page)); 275 } 276 277 int __swap_writepage(struct page *page, struct writeback_control *wbc, 278 bio_end_io_t end_write_func) 279 { 280 struct bio *bio; 281 int ret; 282 struct swap_info_struct *sis = page_swap_info(page); 283 284 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 285 if (sis->flags & SWP_FS) { 286 struct kiocb kiocb; 287 struct file *swap_file = sis->swap_file; 288 struct address_space *mapping = swap_file->f_mapping; 289 struct bio_vec bv = { 290 .bv_page = page, 291 .bv_len = PAGE_SIZE, 292 .bv_offset = 0 293 }; 294 struct iov_iter from; 295 296 iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE); 297 init_sync_kiocb(&kiocb, swap_file); 298 kiocb.ki_pos = page_file_offset(page); 299 300 set_page_writeback(page); 301 unlock_page(page); 302 ret = mapping->a_ops->direct_IO(&kiocb, &from); 303 if (ret == PAGE_SIZE) { 304 count_vm_event(PSWPOUT); 305 ret = 0; 306 } else { 307 /* 308 * In the case of swap-over-nfs, this can be a 309 * temporary failure if the system has limited 310 * memory for allocating transmit buffers. 311 * Mark the page dirty and avoid 312 * rotate_reclaimable_page but rate-limit the 313 * messages but do not flag PageError like 314 * the normal direct-to-bio case as it could 315 * be temporary. 316 */ 317 set_page_dirty(page); 318 ClearPageReclaim(page); 319 pr_err_ratelimited("Write error on dio swapfile (%llu)\n", 320 page_file_offset(page)); 321 } 322 end_page_writeback(page); 323 return ret; 324 } 325 326 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); 327 if (!ret) { 328 count_swpout_vm_event(page); 329 return 0; 330 } 331 332 ret = 0; 333 bio = get_swap_bio(GFP_NOIO, page, end_write_func); 334 if (bio == NULL) { 335 set_page_dirty(page); 336 unlock_page(page); 337 ret = -ENOMEM; 338 goto out; 339 } 340 bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc); 341 bio_associate_blkg_from_page(bio, page); 342 count_swpout_vm_event(page); 343 set_page_writeback(page); 344 unlock_page(page); 345 submit_bio(bio); 346 out: 347 return ret; 348 } 349 350 int swap_readpage(struct page *page, bool synchronous) 351 { 352 struct bio *bio; 353 int ret = 0; 354 struct swap_info_struct *sis = page_swap_info(page); 355 blk_qc_t qc; 356 struct gendisk *disk; 357 358 VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page); 359 VM_BUG_ON_PAGE(!PageLocked(page), page); 360 VM_BUG_ON_PAGE(PageUptodate(page), page); 361 if (frontswap_load(page) == 0) { 362 SetPageUptodate(page); 363 unlock_page(page); 364 goto out; 365 } 366 367 if (sis->flags & SWP_FS) { 368 struct file *swap_file = sis->swap_file; 369 struct address_space *mapping = swap_file->f_mapping; 370 371 ret = mapping->a_ops->readpage(swap_file, page); 372 if (!ret) 373 count_vm_event(PSWPIN); 374 return ret; 375 } 376 377 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); 378 if (!ret) { 379 if (trylock_page(page)) { 380 swap_slot_free_notify(page); 381 unlock_page(page); 382 } 383 384 count_vm_event(PSWPIN); 385 return 0; 386 } 387 388 ret = 0; 389 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); 390 if (bio == NULL) { 391 unlock_page(page); 392 ret = -ENOMEM; 393 goto out; 394 } 395 disk = bio->bi_disk; 396 /* 397 * Keep this task valid during swap readpage because the oom killer may 398 * attempt to access it in the page fault retry time check. 399 */ 400 bio_set_op_attrs(bio, REQ_OP_READ, 0); 401 if (synchronous) { 402 bio->bi_opf |= REQ_HIPRI; 403 get_task_struct(current); 404 bio->bi_private = current; 405 } 406 count_vm_event(PSWPIN); 407 bio_get(bio); 408 qc = submit_bio(bio); 409 while (synchronous) { 410 set_current_state(TASK_UNINTERRUPTIBLE); 411 if (!READ_ONCE(bio->bi_private)) 412 break; 413 414 if (!blk_poll(disk->queue, qc, true)) 415 io_schedule(); 416 } 417 __set_current_state(TASK_RUNNING); 418 bio_put(bio); 419 420 out: 421 return ret; 422 } 423 424 int swap_set_page_dirty(struct page *page) 425 { 426 struct swap_info_struct *sis = page_swap_info(page); 427 428 if (sis->flags & SWP_FS) { 429 struct address_space *mapping = sis->swap_file->f_mapping; 430 431 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 432 return mapping->a_ops->set_page_dirty(page); 433 } else { 434 return __set_page_dirty_no_writeback(page); 435 } 436 } 437