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 struct bio *bio; 32 33 bio = bio_alloc(gfp_flags, 1); 34 if (bio) { 35 bio->bi_iter.bi_sector = map_swap_page(page, &bio->bi_bdev); 36 bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; 37 bio->bi_end_io = end_io; 38 39 bio_add_page(bio, page, PAGE_SIZE, 0); 40 BUG_ON(bio->bi_iter.bi_size != PAGE_SIZE); 41 } 42 return bio; 43 } 44 45 void end_swap_bio_write(struct bio *bio) 46 { 47 struct page *page = bio->bi_io_vec[0].bv_page; 48 49 if (bio->bi_status) { 50 SetPageError(page); 51 /* 52 * We failed to write the page out to swap-space. 53 * Re-dirty the page in order to avoid it being reclaimed. 54 * Also print a dire warning that things will go BAD (tm) 55 * very quickly. 56 * 57 * Also clear PG_reclaim to avoid rotate_reclaimable_page() 58 */ 59 set_page_dirty(page); 60 pr_alert("Write-error on swap-device (%u:%u:%llu)\n", 61 imajor(bio->bi_bdev->bd_inode), 62 iminor(bio->bi_bdev->bd_inode), 63 (unsigned long long)bio->bi_iter.bi_sector); 64 ClearPageReclaim(page); 65 } 66 end_page_writeback(page); 67 bio_put(bio); 68 } 69 70 static void swap_slot_free_notify(struct page *page) 71 { 72 struct swap_info_struct *sis; 73 struct gendisk *disk; 74 75 /* 76 * There is no guarantee that the page is in swap cache - the software 77 * suspend code (at least) uses end_swap_bio_read() against a non- 78 * swapcache page. So we must check PG_swapcache before proceeding with 79 * this optimization. 80 */ 81 if (unlikely(!PageSwapCache(page))) 82 return; 83 84 sis = page_swap_info(page); 85 if (!(sis->flags & SWP_BLKDEV)) 86 return; 87 88 /* 89 * The swap subsystem performs lazy swap slot freeing, 90 * expecting that the page will be swapped out again. 91 * So we can avoid an unnecessary write if the page 92 * isn't redirtied. 93 * This is good for real swap storage because we can 94 * reduce unnecessary I/O and enhance wear-leveling 95 * if an SSD is used as the as swap device. 96 * But if in-memory swap device (eg zram) is used, 97 * this causes a duplicated copy between uncompressed 98 * data in VM-owned memory and compressed data in 99 * zram-owned memory. So let's free zram-owned memory 100 * and make the VM-owned decompressed page *dirty*, 101 * so the page should be swapped out somewhere again if 102 * we again wish to reclaim it. 103 */ 104 disk = sis->bdev->bd_disk; 105 if (disk->fops->swap_slot_free_notify) { 106 swp_entry_t entry; 107 unsigned long offset; 108 109 entry.val = page_private(page); 110 offset = swp_offset(entry); 111 112 SetPageDirty(page); 113 disk->fops->swap_slot_free_notify(sis->bdev, 114 offset); 115 } 116 } 117 118 static void end_swap_bio_read(struct bio *bio) 119 { 120 struct page *page = bio->bi_io_vec[0].bv_page; 121 struct task_struct *waiter = bio->bi_private; 122 123 if (bio->bi_status) { 124 SetPageError(page); 125 ClearPageUptodate(page); 126 pr_alert("Read-error on swap-device (%u:%u:%llu)\n", 127 imajor(bio->bi_bdev->bd_inode), 128 iminor(bio->bi_bdev->bd_inode), 129 (unsigned long long)bio->bi_iter.bi_sector); 130 goto out; 131 } 132 133 SetPageUptodate(page); 134 swap_slot_free_notify(page); 135 out: 136 unlock_page(page); 137 WRITE_ONCE(bio->bi_private, NULL); 138 bio_put(bio); 139 wake_up_process(waiter); 140 put_task_struct(waiter); 141 } 142 143 int generic_swapfile_activate(struct swap_info_struct *sis, 144 struct file *swap_file, 145 sector_t *span) 146 { 147 struct address_space *mapping = swap_file->f_mapping; 148 struct inode *inode = mapping->host; 149 unsigned blocks_per_page; 150 unsigned long page_no; 151 unsigned blkbits; 152 sector_t probe_block; 153 sector_t last_block; 154 sector_t lowest_block = -1; 155 sector_t highest_block = 0; 156 int nr_extents = 0; 157 int ret; 158 159 blkbits = inode->i_blkbits; 160 blocks_per_page = PAGE_SIZE >> blkbits; 161 162 /* 163 * Map all the blocks into the extent list. This code doesn't try 164 * to be very smart. 165 */ 166 probe_block = 0; 167 page_no = 0; 168 last_block = i_size_read(inode) >> blkbits; 169 while ((probe_block + blocks_per_page) <= last_block && 170 page_no < sis->max) { 171 unsigned block_in_page; 172 sector_t first_block; 173 174 cond_resched(); 175 176 first_block = bmap(inode, probe_block); 177 if (first_block == 0) 178 goto bad_bmap; 179 180 /* 181 * It must be PAGE_SIZE aligned on-disk 182 */ 183 if (first_block & (blocks_per_page - 1)) { 184 probe_block++; 185 goto reprobe; 186 } 187 188 for (block_in_page = 1; block_in_page < blocks_per_page; 189 block_in_page++) { 190 sector_t block; 191 192 block = bmap(inode, probe_block + block_in_page); 193 if (block == 0) 194 goto bad_bmap; 195 if (block != first_block + block_in_page) { 196 /* Discontiguity */ 197 probe_block++; 198 goto reprobe; 199 } 200 } 201 202 first_block >>= (PAGE_SHIFT - blkbits); 203 if (page_no) { /* exclude the header page */ 204 if (first_block < lowest_block) 205 lowest_block = first_block; 206 if (first_block > highest_block) 207 highest_block = first_block; 208 } 209 210 /* 211 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 212 */ 213 ret = add_swap_extent(sis, page_no, 1, first_block); 214 if (ret < 0) 215 goto out; 216 nr_extents += ret; 217 page_no++; 218 probe_block += blocks_per_page; 219 reprobe: 220 continue; 221 } 222 ret = nr_extents; 223 *span = 1 + highest_block - lowest_block; 224 if (page_no == 0) 225 page_no = 1; /* force Empty message */ 226 sis->max = page_no; 227 sis->pages = page_no - 1; 228 sis->highest_bit = page_no - 1; 229 out: 230 return ret; 231 bad_bmap: 232 pr_err("swapon: swapfile has holes\n"); 233 ret = -EINVAL; 234 goto out; 235 } 236 237 /* 238 * We may have stale swap cache pages in memory: notice 239 * them here and get rid of the unnecessary final write. 240 */ 241 int swap_writepage(struct page *page, struct writeback_control *wbc) 242 { 243 int ret = 0; 244 245 if (try_to_free_swap(page)) { 246 unlock_page(page); 247 goto out; 248 } 249 if (frontswap_store(page) == 0) { 250 set_page_writeback(page); 251 unlock_page(page); 252 end_page_writeback(page); 253 goto out; 254 } 255 ret = __swap_writepage(page, wbc, end_swap_bio_write); 256 out: 257 return ret; 258 } 259 260 static sector_t swap_page_sector(struct page *page) 261 { 262 return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9); 263 } 264 265 int __swap_writepage(struct page *page, struct writeback_control *wbc, 266 bio_end_io_t end_write_func) 267 { 268 struct bio *bio; 269 int ret; 270 struct swap_info_struct *sis = page_swap_info(page); 271 272 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 273 if (sis->flags & SWP_FILE) { 274 struct kiocb kiocb; 275 struct file *swap_file = sis->swap_file; 276 struct address_space *mapping = swap_file->f_mapping; 277 struct bio_vec bv = { 278 .bv_page = page, 279 .bv_len = PAGE_SIZE, 280 .bv_offset = 0 281 }; 282 struct iov_iter from; 283 284 iov_iter_bvec(&from, ITER_BVEC | WRITE, &bv, 1, PAGE_SIZE); 285 init_sync_kiocb(&kiocb, swap_file); 286 kiocb.ki_pos = page_file_offset(page); 287 288 set_page_writeback(page); 289 unlock_page(page); 290 ret = mapping->a_ops->direct_IO(&kiocb, &from); 291 if (ret == PAGE_SIZE) { 292 count_vm_event(PSWPOUT); 293 ret = 0; 294 } else { 295 /* 296 * In the case of swap-over-nfs, this can be a 297 * temporary failure if the system has limited 298 * memory for allocating transmit buffers. 299 * Mark the page dirty and avoid 300 * rotate_reclaimable_page but rate-limit the 301 * messages but do not flag PageError like 302 * the normal direct-to-bio case as it could 303 * be temporary. 304 */ 305 set_page_dirty(page); 306 ClearPageReclaim(page); 307 pr_err_ratelimited("Write error on dio swapfile (%llu)\n", 308 page_file_offset(page)); 309 } 310 end_page_writeback(page); 311 return ret; 312 } 313 314 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); 315 if (!ret) { 316 count_vm_event(PSWPOUT); 317 return 0; 318 } 319 320 ret = 0; 321 bio = get_swap_bio(GFP_NOIO, page, end_write_func); 322 if (bio == NULL) { 323 set_page_dirty(page); 324 unlock_page(page); 325 ret = -ENOMEM; 326 goto out; 327 } 328 bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc); 329 count_vm_event(PSWPOUT); 330 set_page_writeback(page); 331 unlock_page(page); 332 submit_bio(bio); 333 out: 334 return ret; 335 } 336 337 int swap_readpage(struct page *page, bool do_poll) 338 { 339 struct bio *bio; 340 int ret = 0; 341 struct swap_info_struct *sis = page_swap_info(page); 342 blk_qc_t qc; 343 struct block_device *bdev; 344 345 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 346 VM_BUG_ON_PAGE(!PageLocked(page), page); 347 VM_BUG_ON_PAGE(PageUptodate(page), page); 348 if (frontswap_load(page) == 0) { 349 SetPageUptodate(page); 350 unlock_page(page); 351 goto out; 352 } 353 354 if (sis->flags & SWP_FILE) { 355 struct file *swap_file = sis->swap_file; 356 struct address_space *mapping = swap_file->f_mapping; 357 358 ret = mapping->a_ops->readpage(swap_file, page); 359 if (!ret) 360 count_vm_event(PSWPIN); 361 return ret; 362 } 363 364 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); 365 if (!ret) { 366 if (trylock_page(page)) { 367 swap_slot_free_notify(page); 368 unlock_page(page); 369 } 370 371 count_vm_event(PSWPIN); 372 return 0; 373 } 374 375 ret = 0; 376 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); 377 if (bio == NULL) { 378 unlock_page(page); 379 ret = -ENOMEM; 380 goto out; 381 } 382 bdev = bio->bi_bdev; 383 /* 384 * Keep this task valid during swap readpage because the oom killer may 385 * attempt to access it in the page fault retry time check. 386 */ 387 get_task_struct(current); 388 bio->bi_private = current; 389 bio_set_op_attrs(bio, REQ_OP_READ, 0); 390 count_vm_event(PSWPIN); 391 bio_get(bio); 392 qc = submit_bio(bio); 393 while (do_poll) { 394 set_current_state(TASK_UNINTERRUPTIBLE); 395 if (!READ_ONCE(bio->bi_private)) 396 break; 397 398 if (!blk_mq_poll(bdev_get_queue(bdev), qc)) 399 break; 400 } 401 __set_current_state(TASK_RUNNING); 402 bio_put(bio); 403 404 out: 405 return ret; 406 } 407 408 int swap_set_page_dirty(struct page *page) 409 { 410 struct swap_info_struct *sis = page_swap_info(page); 411 412 if (sis->flags & SWP_FILE) { 413 struct address_space *mapping = sis->swap_file->f_mapping; 414 415 VM_BUG_ON_PAGE(!PageSwapCache(page), page); 416 return mapping->a_ops->set_page_dirty(page); 417 } else { 418 return __set_page_dirty_no_writeback(page); 419 } 420 } 421