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 first_block = bmap(inode, probe_block); 170 if (first_block == 0) 171 goto bad_bmap; 172 173 /* 174 * It must be PAGE_SIZE aligned on-disk 175 */ 176 if (first_block & (blocks_per_page - 1)) { 177 probe_block++; 178 goto reprobe; 179 } 180 181 for (block_in_page = 1; block_in_page < blocks_per_page; 182 block_in_page++) { 183 sector_t block; 184 185 block = bmap(inode, probe_block + block_in_page); 186 if (block == 0) 187 goto bad_bmap; 188 if (block != first_block + block_in_page) { 189 /* Discontiguity */ 190 probe_block++; 191 goto reprobe; 192 } 193 } 194 195 first_block >>= (PAGE_SHIFT - blkbits); 196 if (page_no) { /* exclude the header page */ 197 if (first_block < lowest_block) 198 lowest_block = first_block; 199 if (first_block > highest_block) 200 highest_block = first_block; 201 } 202 203 /* 204 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 205 */ 206 ret = add_swap_extent(sis, page_no, 1, first_block); 207 if (ret < 0) 208 goto out; 209 nr_extents += ret; 210 page_no++; 211 probe_block += blocks_per_page; 212 reprobe: 213 continue; 214 } 215 ret = nr_extents; 216 *span = 1 + highest_block - lowest_block; 217 if (page_no == 0) 218 page_no = 1; /* force Empty message */ 219 sis->max = page_no; 220 sis->pages = page_no - 1; 221 sis->highest_bit = page_no - 1; 222 out: 223 return ret; 224 bad_bmap: 225 pr_err("swapon: swapfile has holes\n"); 226 ret = -EINVAL; 227 goto out; 228 } 229 230 /* 231 * We may have stale swap cache pages in memory: notice 232 * them here and get rid of the unnecessary final write. 233 */ 234 int swap_writepage(struct page *page, struct writeback_control *wbc) 235 { 236 int ret = 0; 237 238 if (try_to_free_swap(page)) { 239 unlock_page(page); 240 goto out; 241 } 242 if (frontswap_store(page) == 0) { 243 set_page_writeback(page); 244 unlock_page(page); 245 end_page_writeback(page); 246 goto out; 247 } 248 ret = __swap_writepage(page, wbc, end_swap_bio_write); 249 out: 250 return ret; 251 } 252 253 static sector_t swap_page_sector(struct page *page) 254 { 255 return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9); 256 } 257 258 int __swap_writepage(struct page *page, struct writeback_control *wbc, 259 bio_end_io_t end_write_func) 260 { 261 struct bio *bio; 262 int ret, rw = WRITE; 263 struct swap_info_struct *sis = page_swap_info(page); 264 265 if (sis->flags & SWP_FILE) { 266 struct kiocb kiocb; 267 struct file *swap_file = sis->swap_file; 268 struct address_space *mapping = swap_file->f_mapping; 269 struct bio_vec bv = { 270 .bv_page = page, 271 .bv_len = PAGE_SIZE, 272 .bv_offset = 0 273 }; 274 struct iov_iter from; 275 276 iov_iter_bvec(&from, ITER_BVEC | WRITE, &bv, 1, PAGE_SIZE); 277 init_sync_kiocb(&kiocb, swap_file); 278 kiocb.ki_pos = page_file_offset(page); 279 280 set_page_writeback(page); 281 unlock_page(page); 282 ret = mapping->a_ops->direct_IO(&kiocb, &from, kiocb.ki_pos); 283 if (ret == PAGE_SIZE) { 284 count_vm_event(PSWPOUT); 285 ret = 0; 286 } else { 287 /* 288 * In the case of swap-over-nfs, this can be a 289 * temporary failure if the system has limited 290 * memory for allocating transmit buffers. 291 * Mark the page dirty and avoid 292 * rotate_reclaimable_page but rate-limit the 293 * messages but do not flag PageError like 294 * the normal direct-to-bio case as it could 295 * be temporary. 296 */ 297 set_page_dirty(page); 298 ClearPageReclaim(page); 299 pr_err_ratelimited("Write error on dio swapfile (%llu)\n", 300 page_file_offset(page)); 301 } 302 end_page_writeback(page); 303 return ret; 304 } 305 306 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc); 307 if (!ret) { 308 count_vm_event(PSWPOUT); 309 return 0; 310 } 311 312 ret = 0; 313 bio = get_swap_bio(GFP_NOIO, page, end_write_func); 314 if (bio == NULL) { 315 set_page_dirty(page); 316 unlock_page(page); 317 ret = -ENOMEM; 318 goto out; 319 } 320 if (wbc->sync_mode == WB_SYNC_ALL) 321 rw |= REQ_SYNC; 322 count_vm_event(PSWPOUT); 323 set_page_writeback(page); 324 unlock_page(page); 325 submit_bio(rw, bio); 326 out: 327 return ret; 328 } 329 330 int swap_readpage(struct page *page) 331 { 332 struct bio *bio; 333 int ret = 0; 334 struct swap_info_struct *sis = page_swap_info(page); 335 336 VM_BUG_ON_PAGE(!PageLocked(page), page); 337 VM_BUG_ON_PAGE(PageUptodate(page), page); 338 if (frontswap_load(page) == 0) { 339 SetPageUptodate(page); 340 unlock_page(page); 341 goto out; 342 } 343 344 if (sis->flags & SWP_FILE) { 345 struct file *swap_file = sis->swap_file; 346 struct address_space *mapping = swap_file->f_mapping; 347 348 ret = mapping->a_ops->readpage(swap_file, page); 349 if (!ret) 350 count_vm_event(PSWPIN); 351 return ret; 352 } 353 354 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page); 355 if (!ret) { 356 swap_slot_free_notify(page); 357 count_vm_event(PSWPIN); 358 return 0; 359 } 360 361 ret = 0; 362 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); 363 if (bio == NULL) { 364 unlock_page(page); 365 ret = -ENOMEM; 366 goto out; 367 } 368 count_vm_event(PSWPIN); 369 submit_bio(READ, bio); 370 out: 371 return ret; 372 } 373 374 int swap_set_page_dirty(struct page *page) 375 { 376 struct swap_info_struct *sis = page_swap_info(page); 377 378 if (sis->flags & SWP_FILE) { 379 struct address_space *mapping = sis->swap_file->f_mapping; 380 return mapping->a_ops->set_page_dirty(page); 381 } else { 382 return __set_page_dirty_no_writeback(page); 383 } 384 } 385