1 /* 2 * linux/mm/page_io.c 3 * 4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 5 * 6 * Swap reorganised 29.12.95, 7 * Asynchronous swapping added 30.12.95. Stephen Tweedie 8 * Removed race in async swapping. 14.4.1996. Bruno Haible 9 * Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie 10 * Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman 11 */ 12 13 #include <linux/mm.h> 14 #include <linux/kernel_stat.h> 15 #include <linux/gfp.h> 16 #include <linux/pagemap.h> 17 #include <linux/swap.h> 18 #include <linux/bio.h> 19 #include <linux/swapops.h> 20 #include <linux/buffer_head.h> 21 #include <linux/writeback.h> 22 #include <linux/frontswap.h> 23 #include <linux/blkdev.h> 24 #include <linux/uio.h> 25 #include <linux/sched/task.h> 26 #include <asm/pgtable.h> 27 28 static struct bio *get_swap_bio(gfp_t gfp_flags, 29 struct page *page, bio_end_io_t end_io) 30 { 31 int i, nr = hpage_nr_pages(page); 32 struct bio *bio; 33 34 bio = bio_alloc(gfp_flags, nr); 35 if (bio) { 36 bio->bi_iter.bi_sector = map_swap_page(page, &bio->bi_bdev); 37 bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; 38 bio->bi_end_io = end_io; 39 40 for (i = 0; i < nr; i++) 41 bio_add_page(bio, page + i, PAGE_SIZE, 0); 42 VM_BUG_ON(bio->bi_iter.bi_size != PAGE_SIZE * nr); 43 } 44 return bio; 45 } 46 47 void end_swap_bio_write(struct bio *bio) 48 { 49 struct page *page = bio->bi_io_vec[0].bv_page; 50 51 if (bio->bi_status) { 52 SetPageError(page); 53 /* 54 * We failed to write the page out to swap-space. 55 * Re-dirty the page in order to avoid it being reclaimed. 56 * Also print a dire warning that things will go BAD (tm) 57 * very quickly. 58 * 59 * Also clear PG_reclaim to avoid rotate_reclaimable_page() 60 */ 61 set_page_dirty(page); 62 pr_alert("Write-error on swap-device (%u:%u:%llu)\n", 63 imajor(bio->bi_bdev->bd_inode), 64 iminor(bio->bi_bdev->bd_inode), 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->bi_io_vec[0].bv_page; 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 imajor(bio->bi_bdev->bd_inode), 130 iminor(bio->bi_bdev->bd_inode), 131 (unsigned long long)bio->bi_iter.bi_sector); 132 goto out; 133 } 134 135 SetPageUptodate(page); 136 swap_slot_free_notify(page); 137 out: 138 unlock_page(page); 139 WRITE_ONCE(bio->bi_private, NULL); 140 bio_put(bio); 141 wake_up_process(waiter); 142 put_task_struct(waiter); 143 } 144 145 int generic_swapfile_activate(struct swap_info_struct *sis, 146 struct file *swap_file, 147 sector_t *span) 148 { 149 struct address_space *mapping = swap_file->f_mapping; 150 struct inode *inode = mapping->host; 151 unsigned blocks_per_page; 152 unsigned long page_no; 153 unsigned blkbits; 154 sector_t probe_block; 155 sector_t last_block; 156 sector_t lowest_block = -1; 157 sector_t highest_block = 0; 158 int nr_extents = 0; 159 int ret; 160 161 blkbits = inode->i_blkbits; 162 blocks_per_page = PAGE_SIZE >> blkbits; 163 164 /* 165 * Map all the blocks into the extent list. This code doesn't try 166 * to be very smart. 167 */ 168 probe_block = 0; 169 page_no = 0; 170 last_block = i_size_read(inode) >> blkbits; 171 while ((probe_block + blocks_per_page) <= last_block && 172 page_no < sis->max) { 173 unsigned block_in_page; 174 sector_t first_block; 175 176 cond_resched(); 177 178 first_block = bmap(inode, probe_block); 179 if (first_block == 0) 180 goto bad_bmap; 181 182 /* 183 * It must be PAGE_SIZE aligned on-disk 184 */ 185 if (first_block & (blocks_per_page - 1)) { 186 probe_block++; 187 goto reprobe; 188 } 189 190 for (block_in_page = 1; block_in_page < blocks_per_page; 191 block_in_page++) { 192 sector_t block; 193 194 block = bmap(inode, probe_block + block_in_page); 195 if (block == 0) 196 goto bad_bmap; 197 if (block != first_block + block_in_page) { 198 /* Discontiguity */ 199 probe_block++; 200 goto reprobe; 201 } 202 } 203 204 first_block >>= (PAGE_SHIFT - blkbits); 205 if (page_no) { /* exclude the header page */ 206 if (first_block < lowest_block) 207 lowest_block = first_block; 208 if (first_block > highest_block) 209 highest_block = first_block; 210 } 211 212 /* 213 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 214 */ 215 ret = add_swap_extent(sis, page_no, 1, first_block); 216 if (ret < 0) 217 goto out; 218 nr_extents += ret; 219 page_no++; 220 probe_block += blocks_per_page; 221 reprobe: 222 continue; 223 } 224 ret = nr_extents; 225 *span = 1 + highest_block - lowest_block; 226 if (page_no == 0) 227 page_no = 1; /* force Empty message */ 228 sis->max = page_no; 229 sis->pages = page_no - 1; 230 sis->highest_bit = page_no - 1; 231 out: 232 return ret; 233 bad_bmap: 234 pr_err("swapon: swapfile has holes\n"); 235 ret = -EINVAL; 236 goto out; 237 } 238 239 /* 240 * We may have stale swap cache pages in memory: notice 241 * them here and get rid of the unnecessary final write. 242 */ 243 int swap_writepage(struct page *page, struct writeback_control *wbc) 244 { 245 int ret = 0; 246 247 if (try_to_free_swap(page)) { 248 unlock_page(page); 249 goto out; 250 } 251 if (frontswap_store(page) == 0) { 252 set_page_writeback(page); 253 unlock_page(page); 254 end_page_writeback(page); 255 goto out; 256 } 257 ret = __swap_writepage(page, wbc, end_swap_bio_write); 258 out: 259 return ret; 260 } 261 262 static sector_t swap_page_sector(struct page *page) 263 { 264 return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9); 265 } 266 267 static inline void count_swpout_vm_event(struct page *page) 268 { 269 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 270 if (unlikely(PageTransHuge(page))) 271 count_vm_event(THP_SWPOUT); 272 #endif 273 count_vm_events(PSWPOUT, hpage_nr_pages(page)); 274 } 275 276 int __swap_writepage(struct page *page, struct writeback_control *wbc, 277 bio_end_io_t end_write_func) 278 { 279 struct bio *bio; 280 int ret; 281 struct swap_info_struct *sis = page_swap_info(page); 282 283 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 284 if (sis->flags & SWP_FILE) { 285 struct kiocb kiocb; 286 struct file *swap_file = sis->swap_file; 287 struct address_space *mapping = swap_file->f_mapping; 288 struct bio_vec bv = { 289 .bv_page = page, 290 .bv_len = PAGE_SIZE, 291 .bv_offset = 0 292 }; 293 struct iov_iter from; 294 295 iov_iter_bvec(&from, ITER_BVEC | WRITE, &bv, 1, PAGE_SIZE); 296 init_sync_kiocb(&kiocb, swap_file); 297 kiocb.ki_pos = page_file_offset(page); 298 299 set_page_writeback(page); 300 unlock_page(page); 301 ret = mapping->a_ops->direct_IO(&kiocb, &from); 302 if (ret == PAGE_SIZE) { 303 count_vm_event(PSWPOUT); 304 ret = 0; 305 } else { 306 /* 307 * In the case of swap-over-nfs, this can be a 308 * temporary failure if the system has limited 309 * memory for allocating transmit buffers. 310 * Mark the page dirty and avoid 311 * rotate_reclaimable_page but rate-limit the 312 * messages but do not flag PageError like 313 * the normal direct-to-bio case as it could 314 * be temporary. 315 */ 316 set_page_dirty(page); 317 ClearPageReclaim(page); 318 pr_err_ratelimited("Write error on dio swapfile (%llu)\n", 319 page_file_offset(page)); 320 } 321 end_page_writeback(page); 322 return ret; 323 } 324 325 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); 326 if (!ret) { 327 count_swpout_vm_event(page); 328 return 0; 329 } 330 331 ret = 0; 332 bio = get_swap_bio(GFP_NOIO, page, end_write_func); 333 if (bio == NULL) { 334 set_page_dirty(page); 335 unlock_page(page); 336 ret = -ENOMEM; 337 goto out; 338 } 339 bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc); 340 count_swpout_vm_event(page); 341 set_page_writeback(page); 342 unlock_page(page); 343 submit_bio(bio); 344 out: 345 return ret; 346 } 347 348 int swap_readpage(struct page *page, bool do_poll) 349 { 350 struct bio *bio; 351 int ret = 0; 352 struct swap_info_struct *sis = page_swap_info(page); 353 blk_qc_t qc; 354 struct block_device *bdev; 355 356 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 357 VM_BUG_ON_PAGE(!PageLocked(page), page); 358 VM_BUG_ON_PAGE(PageUptodate(page), page); 359 if (frontswap_load(page) == 0) { 360 SetPageUptodate(page); 361 unlock_page(page); 362 goto out; 363 } 364 365 if (sis->flags & SWP_FILE) { 366 struct file *swap_file = sis->swap_file; 367 struct address_space *mapping = swap_file->f_mapping; 368 369 ret = mapping->a_ops->readpage(swap_file, page); 370 if (!ret) 371 count_vm_event(PSWPIN); 372 return ret; 373 } 374 375 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); 376 if (!ret) { 377 if (trylock_page(page)) { 378 swap_slot_free_notify(page); 379 unlock_page(page); 380 } 381 382 count_vm_event(PSWPIN); 383 return 0; 384 } 385 386 ret = 0; 387 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); 388 if (bio == NULL) { 389 unlock_page(page); 390 ret = -ENOMEM; 391 goto out; 392 } 393 bdev = bio->bi_bdev; 394 /* 395 * Keep this task valid during swap readpage because the oom killer may 396 * attempt to access it in the page fault retry time check. 397 */ 398 get_task_struct(current); 399 bio->bi_private = current; 400 bio_set_op_attrs(bio, REQ_OP_READ, 0); 401 count_vm_event(PSWPIN); 402 bio_get(bio); 403 qc = submit_bio(bio); 404 while (do_poll) { 405 set_current_state(TASK_UNINTERRUPTIBLE); 406 if (!READ_ONCE(bio->bi_private)) 407 break; 408 409 if (!blk_mq_poll(bdev_get_queue(bdev), qc)) 410 break; 411 } 412 __set_current_state(TASK_RUNNING); 413 bio_put(bio); 414 415 out: 416 return ret; 417 } 418 419 int swap_set_page_dirty(struct page *page) 420 { 421 struct swap_info_struct *sis = page_swap_info(page); 422 423 if (sis->flags & SWP_FILE) { 424 struct address_space *mapping = sis->swap_file->f_mapping; 425 426 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 427 return mapping->a_ops->set_page_dirty(page); 428 } else { 429 return __set_page_dirty_no_writeback(page); 430 } 431 } 432