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/aio.h> 24 #include <asm/pgtable.h> 25 26 static struct bio *get_swap_bio(gfp_t gfp_flags, 27 struct page *page, bio_end_io_t end_io) 28 { 29 struct bio *bio; 30 31 bio = bio_alloc(gfp_flags, 1); 32 if (bio) { 33 bio->bi_sector = map_swap_page(page, &bio->bi_bdev); 34 bio->bi_sector <<= PAGE_SHIFT - 9; 35 bio->bi_io_vec[0].bv_page = page; 36 bio->bi_io_vec[0].bv_len = PAGE_SIZE; 37 bio->bi_io_vec[0].bv_offset = 0; 38 bio->bi_vcnt = 1; 39 bio->bi_idx = 0; 40 bio->bi_size = PAGE_SIZE; 41 bio->bi_end_io = end_io; 42 } 43 return bio; 44 } 45 46 void end_swap_bio_write(struct bio *bio, int err) 47 { 48 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 49 struct page *page = bio->bi_io_vec[0].bv_page; 50 51 if (!uptodate) { 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 printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n", 63 imajor(bio->bi_bdev->bd_inode), 64 iminor(bio->bi_bdev->bd_inode), 65 (unsigned long long)bio->bi_sector); 66 ClearPageReclaim(page); 67 } 68 end_page_writeback(page); 69 bio_put(bio); 70 } 71 72 void end_swap_bio_read(struct bio *bio, int err) 73 { 74 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 75 struct page *page = bio->bi_io_vec[0].bv_page; 76 77 if (!uptodate) { 78 SetPageError(page); 79 ClearPageUptodate(page); 80 printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n", 81 imajor(bio->bi_bdev->bd_inode), 82 iminor(bio->bi_bdev->bd_inode), 83 (unsigned long long)bio->bi_sector); 84 } else { 85 SetPageUptodate(page); 86 } 87 unlock_page(page); 88 bio_put(bio); 89 } 90 91 int generic_swapfile_activate(struct swap_info_struct *sis, 92 struct file *swap_file, 93 sector_t *span) 94 { 95 struct address_space *mapping = swap_file->f_mapping; 96 struct inode *inode = mapping->host; 97 unsigned blocks_per_page; 98 unsigned long page_no; 99 unsigned blkbits; 100 sector_t probe_block; 101 sector_t last_block; 102 sector_t lowest_block = -1; 103 sector_t highest_block = 0; 104 int nr_extents = 0; 105 int ret; 106 107 blkbits = inode->i_blkbits; 108 blocks_per_page = PAGE_SIZE >> blkbits; 109 110 /* 111 * Map all the blocks into the extent list. This code doesn't try 112 * to be very smart. 113 */ 114 probe_block = 0; 115 page_no = 0; 116 last_block = i_size_read(inode) >> blkbits; 117 while ((probe_block + blocks_per_page) <= last_block && 118 page_no < sis->max) { 119 unsigned block_in_page; 120 sector_t first_block; 121 122 first_block = bmap(inode, probe_block); 123 if (first_block == 0) 124 goto bad_bmap; 125 126 /* 127 * It must be PAGE_SIZE aligned on-disk 128 */ 129 if (first_block & (blocks_per_page - 1)) { 130 probe_block++; 131 goto reprobe; 132 } 133 134 for (block_in_page = 1; block_in_page < blocks_per_page; 135 block_in_page++) { 136 sector_t block; 137 138 block = bmap(inode, probe_block + block_in_page); 139 if (block == 0) 140 goto bad_bmap; 141 if (block != first_block + block_in_page) { 142 /* Discontiguity */ 143 probe_block++; 144 goto reprobe; 145 } 146 } 147 148 first_block >>= (PAGE_SHIFT - blkbits); 149 if (page_no) { /* exclude the header page */ 150 if (first_block < lowest_block) 151 lowest_block = first_block; 152 if (first_block > highest_block) 153 highest_block = first_block; 154 } 155 156 /* 157 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 158 */ 159 ret = add_swap_extent(sis, page_no, 1, first_block); 160 if (ret < 0) 161 goto out; 162 nr_extents += ret; 163 page_no++; 164 probe_block += blocks_per_page; 165 reprobe: 166 continue; 167 } 168 ret = nr_extents; 169 *span = 1 + highest_block - lowest_block; 170 if (page_no == 0) 171 page_no = 1; /* force Empty message */ 172 sis->max = page_no; 173 sis->pages = page_no - 1; 174 sis->highest_bit = page_no - 1; 175 out: 176 return ret; 177 bad_bmap: 178 printk(KERN_ERR "swapon: swapfile has holes\n"); 179 ret = -EINVAL; 180 goto out; 181 } 182 183 /* 184 * We may have stale swap cache pages in memory: notice 185 * them here and get rid of the unnecessary final write. 186 */ 187 int swap_writepage(struct page *page, struct writeback_control *wbc) 188 { 189 int ret = 0; 190 191 if (try_to_free_swap(page)) { 192 unlock_page(page); 193 goto out; 194 } 195 if (frontswap_store(page) == 0) { 196 set_page_writeback(page); 197 unlock_page(page); 198 end_page_writeback(page); 199 goto out; 200 } 201 ret = __swap_writepage(page, wbc, end_swap_bio_write); 202 out: 203 return ret; 204 } 205 206 int __swap_writepage(struct page *page, struct writeback_control *wbc, 207 void (*end_write_func)(struct bio *, int)) 208 { 209 struct bio *bio; 210 int ret = 0, rw = WRITE; 211 struct swap_info_struct *sis = page_swap_info(page); 212 213 if (sis->flags & SWP_FILE) { 214 struct kiocb kiocb; 215 struct file *swap_file = sis->swap_file; 216 struct address_space *mapping = swap_file->f_mapping; 217 struct iovec iov = { 218 .iov_base = kmap(page), 219 .iov_len = PAGE_SIZE, 220 }; 221 222 init_sync_kiocb(&kiocb, swap_file); 223 kiocb.ki_pos = page_file_offset(page); 224 kiocb.ki_left = PAGE_SIZE; 225 kiocb.ki_nbytes = PAGE_SIZE; 226 227 set_page_writeback(page); 228 unlock_page(page); 229 ret = mapping->a_ops->direct_IO(KERNEL_WRITE, 230 &kiocb, &iov, 231 kiocb.ki_pos, 1); 232 kunmap(page); 233 if (ret == PAGE_SIZE) { 234 count_vm_event(PSWPOUT); 235 ret = 0; 236 } else { 237 /* 238 * In the case of swap-over-nfs, this can be a 239 * temporary failure if the system has limited 240 * memory for allocating transmit buffers. 241 * Mark the page dirty and avoid 242 * rotate_reclaimable_page but rate-limit the 243 * messages but do not flag PageError like 244 * the normal direct-to-bio case as it could 245 * be temporary. 246 */ 247 set_page_dirty(page); 248 ClearPageReclaim(page); 249 pr_err_ratelimited("Write error on dio swapfile (%Lu)\n", 250 page_file_offset(page)); 251 } 252 end_page_writeback(page); 253 return ret; 254 } 255 256 bio = get_swap_bio(GFP_NOIO, page, end_write_func); 257 if (bio == NULL) { 258 set_page_dirty(page); 259 unlock_page(page); 260 ret = -ENOMEM; 261 goto out; 262 } 263 if (wbc->sync_mode == WB_SYNC_ALL) 264 rw |= REQ_SYNC; 265 count_vm_event(PSWPOUT); 266 set_page_writeback(page); 267 unlock_page(page); 268 submit_bio(rw, bio); 269 out: 270 return ret; 271 } 272 273 int swap_readpage(struct page *page) 274 { 275 struct bio *bio; 276 int ret = 0; 277 struct swap_info_struct *sis = page_swap_info(page); 278 279 VM_BUG_ON(!PageLocked(page)); 280 VM_BUG_ON(PageUptodate(page)); 281 if (frontswap_load(page) == 0) { 282 SetPageUptodate(page); 283 unlock_page(page); 284 goto out; 285 } 286 287 if (sis->flags & SWP_FILE) { 288 struct file *swap_file = sis->swap_file; 289 struct address_space *mapping = swap_file->f_mapping; 290 291 ret = mapping->a_ops->readpage(swap_file, page); 292 if (!ret) 293 count_vm_event(PSWPIN); 294 return ret; 295 } 296 297 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); 298 if (bio == NULL) { 299 unlock_page(page); 300 ret = -ENOMEM; 301 goto out; 302 } 303 count_vm_event(PSWPIN); 304 submit_bio(READ, bio); 305 out: 306 return ret; 307 } 308 309 int swap_set_page_dirty(struct page *page) 310 { 311 struct swap_info_struct *sis = page_swap_info(page); 312 313 if (sis->flags & SWP_FILE) { 314 struct address_space *mapping = sis->swap_file->f_mapping; 315 return mapping->a_ops->set_page_dirty(page); 316 } else { 317 return __set_page_dirty_no_writeback(page); 318 } 319 } 320