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