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 <asm/pgtable.h> 26 27 static struct bio *get_swap_bio(gfp_t gfp_flags, 28 struct page *page, bio_end_io_t end_io) 29 { 30 struct bio *bio; 31 32 bio = bio_alloc(gfp_flags, 1); 33 if (bio) { 34 bio->bi_iter.bi_sector = map_swap_page(page, &bio->bi_bdev); 35 bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; 36 bio->bi_end_io = end_io; 37 38 bio_add_page(bio, page, PAGE_SIZE, 0); 39 BUG_ON(bio->bi_iter.bi_size != PAGE_SIZE); 40 } 41 return bio; 42 } 43 44 void end_swap_bio_write(struct bio *bio) 45 { 46 struct page *page = bio->bi_io_vec[0].bv_page; 47 48 if (bio->bi_error) { 49 SetPageError(page); 50 /* 51 * We failed to write the page out to swap-space. 52 * Re-dirty the page in order to avoid it being reclaimed. 53 * Also print a dire warning that things will go BAD (tm) 54 * very quickly. 55 * 56 * Also clear PG_reclaim to avoid rotate_reclaimable_page() 57 */ 58 set_page_dirty(page); 59 pr_alert("Write-error on swap-device (%u:%u:%llu)\n", 60 imajor(bio->bi_bdev->bd_inode), 61 iminor(bio->bi_bdev->bd_inode), 62 (unsigned long long)bio->bi_iter.bi_sector); 63 ClearPageReclaim(page); 64 } 65 end_page_writeback(page); 66 bio_put(bio); 67 } 68 69 static void swap_slot_free_notify(struct page *page) 70 { 71 struct swap_info_struct *sis; 72 struct gendisk *disk; 73 74 /* 75 * There is no guarantee that the page is in swap cache - the software 76 * suspend code (at least) uses end_swap_bio_read() against a non- 77 * swapcache page. So we must check PG_swapcache before proceeding with 78 * this optimization. 79 */ 80 if (unlikely(!PageSwapCache(page))) 81 return; 82 83 sis = page_swap_info(page); 84 if (!(sis->flags & SWP_BLKDEV)) 85 return; 86 87 /* 88 * The swap subsystem performs lazy swap slot freeing, 89 * expecting that the page will be swapped out again. 90 * So we can avoid an unnecessary write if the page 91 * isn't redirtied. 92 * This is good for real swap storage because we can 93 * reduce unnecessary I/O and enhance wear-leveling 94 * if an SSD is used as the as swap device. 95 * But if in-memory swap device (eg zram) is used, 96 * this causes a duplicated copy between uncompressed 97 * data in VM-owned memory and compressed data in 98 * zram-owned memory. So let's free zram-owned memory 99 * and make the VM-owned decompressed page *dirty*, 100 * so the page should be swapped out somewhere again if 101 * we again wish to reclaim it. 102 */ 103 disk = sis->bdev->bd_disk; 104 if (disk->fops->swap_slot_free_notify) { 105 swp_entry_t entry; 106 unsigned long offset; 107 108 entry.val = page_private(page); 109 offset = swp_offset(entry); 110 111 SetPageDirty(page); 112 disk->fops->swap_slot_free_notify(sis->bdev, 113 offset); 114 } 115 } 116 117 static void end_swap_bio_read(struct bio *bio) 118 { 119 struct page *page = bio->bi_io_vec[0].bv_page; 120 121 if (bio->bi_error) { 122 SetPageError(page); 123 ClearPageUptodate(page); 124 pr_alert("Read-error on swap-device (%u:%u:%llu)\n", 125 imajor(bio->bi_bdev->bd_inode), 126 iminor(bio->bi_bdev->bd_inode), 127 (unsigned long long)bio->bi_iter.bi_sector); 128 goto out; 129 } 130 131 SetPageUptodate(page); 132 swap_slot_free_notify(page); 133 out: 134 unlock_page(page); 135 bio_put(bio); 136 } 137 138 int generic_swapfile_activate(struct swap_info_struct *sis, 139 struct file *swap_file, 140 sector_t *span) 141 { 142 struct address_space *mapping = swap_file->f_mapping; 143 struct inode *inode = mapping->host; 144 unsigned blocks_per_page; 145 unsigned long page_no; 146 unsigned blkbits; 147 sector_t probe_block; 148 sector_t last_block; 149 sector_t lowest_block = -1; 150 sector_t highest_block = 0; 151 int nr_extents = 0; 152 int ret; 153 154 blkbits = inode->i_blkbits; 155 blocks_per_page = PAGE_SIZE >> blkbits; 156 157 /* 158 * Map all the blocks into the extent list. This code doesn't try 159 * to be very smart. 160 */ 161 probe_block = 0; 162 page_no = 0; 163 last_block = i_size_read(inode) >> blkbits; 164 while ((probe_block + blocks_per_page) <= last_block && 165 page_no < sis->max) { 166 unsigned block_in_page; 167 sector_t first_block; 168 169 cond_resched(); 170 171 first_block = bmap(inode, probe_block); 172 if (first_block == 0) 173 goto bad_bmap; 174 175 /* 176 * It must be PAGE_SIZE aligned on-disk 177 */ 178 if (first_block & (blocks_per_page - 1)) { 179 probe_block++; 180 goto reprobe; 181 } 182 183 for (block_in_page = 1; block_in_page < blocks_per_page; 184 block_in_page++) { 185 sector_t block; 186 187 block = bmap(inode, probe_block + block_in_page); 188 if (block == 0) 189 goto bad_bmap; 190 if (block != first_block + block_in_page) { 191 /* Discontiguity */ 192 probe_block++; 193 goto reprobe; 194 } 195 } 196 197 first_block >>= (PAGE_SHIFT - blkbits); 198 if (page_no) { /* exclude the header page */ 199 if (first_block < lowest_block) 200 lowest_block = first_block; 201 if (first_block > highest_block) 202 highest_block = first_block; 203 } 204 205 /* 206 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 207 */ 208 ret = add_swap_extent(sis, page_no, 1, first_block); 209 if (ret < 0) 210 goto out; 211 nr_extents += ret; 212 page_no++; 213 probe_block += blocks_per_page; 214 reprobe: 215 continue; 216 } 217 ret = nr_extents; 218 *span = 1 + highest_block - lowest_block; 219 if (page_no == 0) 220 page_no = 1; /* force Empty message */ 221 sis->max = page_no; 222 sis->pages = page_no - 1; 223 sis->highest_bit = page_no - 1; 224 out: 225 return ret; 226 bad_bmap: 227 pr_err("swapon: swapfile has holes\n"); 228 ret = -EINVAL; 229 goto out; 230 } 231 232 /* 233 * We may have stale swap cache pages in memory: notice 234 * them here and get rid of the unnecessary final write. 235 */ 236 int swap_writepage(struct page *page, struct writeback_control *wbc) 237 { 238 int ret = 0; 239 240 if (try_to_free_swap(page)) { 241 unlock_page(page); 242 goto out; 243 } 244 if (frontswap_store(page) == 0) { 245 set_page_writeback(page); 246 unlock_page(page); 247 end_page_writeback(page); 248 goto out; 249 } 250 ret = __swap_writepage(page, wbc, end_swap_bio_write); 251 out: 252 return ret; 253 } 254 255 static sector_t swap_page_sector(struct page *page) 256 { 257 return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9); 258 } 259 260 int __swap_writepage(struct page *page, struct writeback_control *wbc, 261 bio_end_io_t end_write_func) 262 { 263 struct bio *bio; 264 int ret; 265 struct swap_info_struct *sis = page_swap_info(page); 266 267 if (sis->flags & SWP_FILE) { 268 struct kiocb kiocb; 269 struct file *swap_file = sis->swap_file; 270 struct address_space *mapping = swap_file->f_mapping; 271 struct bio_vec bv = { 272 .bv_page = page, 273 .bv_len = PAGE_SIZE, 274 .bv_offset = 0 275 }; 276 struct iov_iter from; 277 278 iov_iter_bvec(&from, ITER_BVEC | WRITE, &bv, 1, PAGE_SIZE); 279 init_sync_kiocb(&kiocb, swap_file); 280 kiocb.ki_pos = page_file_offset(page); 281 282 set_page_writeback(page); 283 unlock_page(page); 284 ret = mapping->a_ops->direct_IO(&kiocb, &from); 285 if (ret == PAGE_SIZE) { 286 count_vm_event(PSWPOUT); 287 ret = 0; 288 } else { 289 /* 290 * In the case of swap-over-nfs, this can be a 291 * temporary failure if the system has limited 292 * memory for allocating transmit buffers. 293 * Mark the page dirty and avoid 294 * rotate_reclaimable_page but rate-limit the 295 * messages but do not flag PageError like 296 * the normal direct-to-bio case as it could 297 * be temporary. 298 */ 299 set_page_dirty(page); 300 ClearPageReclaim(page); 301 pr_err_ratelimited("Write error on dio swapfile (%llu)\n", 302 page_file_offset(page)); 303 } 304 end_page_writeback(page); 305 return ret; 306 } 307 308 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); 309 if (!ret) { 310 count_vm_event(PSWPOUT); 311 return 0; 312 } 313 314 ret = 0; 315 bio = get_swap_bio(GFP_NOIO, page, end_write_func); 316 if (bio == NULL) { 317 set_page_dirty(page); 318 unlock_page(page); 319 ret = -ENOMEM; 320 goto out; 321 } 322 if (wbc->sync_mode == WB_SYNC_ALL) 323 bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC); 324 else 325 bio_set_op_attrs(bio, REQ_OP_WRITE, 0); 326 count_vm_event(PSWPOUT); 327 set_page_writeback(page); 328 unlock_page(page); 329 submit_bio(bio); 330 out: 331 return ret; 332 } 333 334 int swap_readpage(struct page *page) 335 { 336 struct bio *bio; 337 int ret = 0; 338 struct swap_info_struct *sis = page_swap_info(page); 339 340 VM_BUG_ON_PAGE(!PageLocked(page), page); 341 VM_BUG_ON_PAGE(PageUptodate(page), page); 342 if (frontswap_load(page) == 0) { 343 SetPageUptodate(page); 344 unlock_page(page); 345 goto out; 346 } 347 348 if (sis->flags & SWP_FILE) { 349 struct file *swap_file = sis->swap_file; 350 struct address_space *mapping = swap_file->f_mapping; 351 352 ret = mapping->a_ops->readpage(swap_file, page); 353 if (!ret) 354 count_vm_event(PSWPIN); 355 return ret; 356 } 357 358 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); 359 if (!ret) { 360 if (trylock_page(page)) { 361 swap_slot_free_notify(page); 362 unlock_page(page); 363 } 364 365 count_vm_event(PSWPIN); 366 return 0; 367 } 368 369 ret = 0; 370 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); 371 if (bio == NULL) { 372 unlock_page(page); 373 ret = -ENOMEM; 374 goto out; 375 } 376 bio_set_op_attrs(bio, REQ_OP_READ, 0); 377 count_vm_event(PSWPIN); 378 submit_bio(bio); 379 out: 380 return ret; 381 } 382 383 int swap_set_page_dirty(struct page *page) 384 { 385 struct swap_info_struct *sis = page_swap_info(page); 386 387 if (sis->flags & SWP_FILE) { 388 struct address_space *mapping = sis->swap_file->f_mapping; 389 return mapping->a_ops->set_page_dirty(page); 390 } else { 391 return __set_page_dirty_no_writeback(page); 392 } 393 } 394