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 <asm/pgtable.h> 24 25 static struct bio *get_swap_bio(gfp_t gfp_flags, 26 struct page *page, bio_end_io_t end_io) 27 { 28 struct bio *bio; 29 30 bio = bio_alloc(gfp_flags, 1); 31 if (bio) { 32 bio->bi_sector = map_swap_page(page, &bio->bi_bdev); 33 bio->bi_sector <<= PAGE_SHIFT - 9; 34 bio->bi_io_vec[0].bv_page = page; 35 bio->bi_io_vec[0].bv_len = PAGE_SIZE; 36 bio->bi_io_vec[0].bv_offset = 0; 37 bio->bi_vcnt = 1; 38 bio->bi_idx = 0; 39 bio->bi_size = PAGE_SIZE; 40 bio->bi_end_io = end_io; 41 } 42 return bio; 43 } 44 45 static void end_swap_bio_write(struct bio *bio, int err) 46 { 47 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 48 struct page *page = bio->bi_io_vec[0].bv_page; 49 50 if (!uptodate) { 51 SetPageError(page); 52 /* 53 * We failed to write the page out to swap-space. 54 * Re-dirty the page in order to avoid it being reclaimed. 55 * Also print a dire warning that things will go BAD (tm) 56 * very quickly. 57 * 58 * Also clear PG_reclaim to avoid rotate_reclaimable_page() 59 */ 60 set_page_dirty(page); 61 printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n", 62 imajor(bio->bi_bdev->bd_inode), 63 iminor(bio->bi_bdev->bd_inode), 64 (unsigned long long)bio->bi_sector); 65 ClearPageReclaim(page); 66 } 67 end_page_writeback(page); 68 bio_put(bio); 69 } 70 71 void end_swap_bio_read(struct bio *bio, int err) 72 { 73 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 74 struct page *page = bio->bi_io_vec[0].bv_page; 75 76 if (!uptodate) { 77 SetPageError(page); 78 ClearPageUptodate(page); 79 printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n", 80 imajor(bio->bi_bdev->bd_inode), 81 iminor(bio->bi_bdev->bd_inode), 82 (unsigned long long)bio->bi_sector); 83 } else { 84 SetPageUptodate(page); 85 } 86 unlock_page(page); 87 bio_put(bio); 88 } 89 90 int generic_swapfile_activate(struct swap_info_struct *sis, 91 struct file *swap_file, 92 sector_t *span) 93 { 94 struct address_space *mapping = swap_file->f_mapping; 95 struct inode *inode = mapping->host; 96 unsigned blocks_per_page; 97 unsigned long page_no; 98 unsigned blkbits; 99 sector_t probe_block; 100 sector_t last_block; 101 sector_t lowest_block = -1; 102 sector_t highest_block = 0; 103 int nr_extents = 0; 104 int ret; 105 106 blkbits = inode->i_blkbits; 107 blocks_per_page = PAGE_SIZE >> blkbits; 108 109 /* 110 * Map all the blocks into the extent list. This code doesn't try 111 * to be very smart. 112 */ 113 probe_block = 0; 114 page_no = 0; 115 last_block = i_size_read(inode) >> blkbits; 116 while ((probe_block + blocks_per_page) <= last_block && 117 page_no < sis->max) { 118 unsigned block_in_page; 119 sector_t first_block; 120 121 first_block = bmap(inode, probe_block); 122 if (first_block == 0) 123 goto bad_bmap; 124 125 /* 126 * It must be PAGE_SIZE aligned on-disk 127 */ 128 if (first_block & (blocks_per_page - 1)) { 129 probe_block++; 130 goto reprobe; 131 } 132 133 for (block_in_page = 1; block_in_page < blocks_per_page; 134 block_in_page++) { 135 sector_t block; 136 137 block = bmap(inode, probe_block + block_in_page); 138 if (block == 0) 139 goto bad_bmap; 140 if (block != first_block + block_in_page) { 141 /* Discontiguity */ 142 probe_block++; 143 goto reprobe; 144 } 145 } 146 147 first_block >>= (PAGE_SHIFT - blkbits); 148 if (page_no) { /* exclude the header page */ 149 if (first_block < lowest_block) 150 lowest_block = first_block; 151 if (first_block > highest_block) 152 highest_block = first_block; 153 } 154 155 /* 156 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 157 */ 158 ret = add_swap_extent(sis, page_no, 1, first_block); 159 if (ret < 0) 160 goto out; 161 nr_extents += ret; 162 page_no++; 163 probe_block += blocks_per_page; 164 reprobe: 165 continue; 166 } 167 ret = nr_extents; 168 *span = 1 + highest_block - lowest_block; 169 if (page_no == 0) 170 page_no = 1; /* force Empty message */ 171 sis->max = page_no; 172 sis->pages = page_no - 1; 173 sis->highest_bit = page_no - 1; 174 out: 175 return ret; 176 bad_bmap: 177 printk(KERN_ERR "swapon: swapfile has holes\n"); 178 ret = -EINVAL; 179 goto out; 180 } 181 182 /* 183 * We may have stale swap cache pages in memory: notice 184 * them here and get rid of the unnecessary final write. 185 */ 186 int swap_writepage(struct page *page, struct writeback_control *wbc) 187 { 188 struct bio *bio; 189 int ret = 0, rw = WRITE; 190 struct swap_info_struct *sis = page_swap_info(page); 191 192 if (try_to_free_swap(page)) { 193 unlock_page(page); 194 goto out; 195 } 196 if (frontswap_store(page) == 0) { 197 set_page_writeback(page); 198 unlock_page(page); 199 end_page_writeback(page); 200 goto out; 201 } 202 203 if (sis->flags & SWP_FILE) { 204 struct kiocb kiocb; 205 struct file *swap_file = sis->swap_file; 206 struct address_space *mapping = swap_file->f_mapping; 207 struct iovec iov = { 208 .iov_base = kmap(page), 209 .iov_len = PAGE_SIZE, 210 }; 211 212 init_sync_kiocb(&kiocb, swap_file); 213 kiocb.ki_pos = page_file_offset(page); 214 kiocb.ki_left = PAGE_SIZE; 215 kiocb.ki_nbytes = PAGE_SIZE; 216 217 unlock_page(page); 218 ret = mapping->a_ops->direct_IO(KERNEL_WRITE, 219 &kiocb, &iov, 220 kiocb.ki_pos, 1); 221 kunmap(page); 222 if (ret == PAGE_SIZE) { 223 count_vm_event(PSWPOUT); 224 ret = 0; 225 } 226 return ret; 227 } 228 229 bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write); 230 if (bio == NULL) { 231 set_page_dirty(page); 232 unlock_page(page); 233 ret = -ENOMEM; 234 goto out; 235 } 236 if (wbc->sync_mode == WB_SYNC_ALL) 237 rw |= REQ_SYNC; 238 count_vm_event(PSWPOUT); 239 set_page_writeback(page); 240 unlock_page(page); 241 submit_bio(rw, bio); 242 out: 243 return ret; 244 } 245 246 int swap_readpage(struct page *page) 247 { 248 struct bio *bio; 249 int ret = 0; 250 struct swap_info_struct *sis = page_swap_info(page); 251 252 VM_BUG_ON(!PageLocked(page)); 253 VM_BUG_ON(PageUptodate(page)); 254 if (frontswap_load(page) == 0) { 255 SetPageUptodate(page); 256 unlock_page(page); 257 goto out; 258 } 259 260 if (sis->flags & SWP_FILE) { 261 struct file *swap_file = sis->swap_file; 262 struct address_space *mapping = swap_file->f_mapping; 263 264 ret = mapping->a_ops->readpage(swap_file, page); 265 if (!ret) 266 count_vm_event(PSWPIN); 267 return ret; 268 } 269 270 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); 271 if (bio == NULL) { 272 unlock_page(page); 273 ret = -ENOMEM; 274 goto out; 275 } 276 count_vm_event(PSWPIN); 277 submit_bio(READ, bio); 278 out: 279 return ret; 280 } 281 282 int swap_set_page_dirty(struct page *page) 283 { 284 struct swap_info_struct *sis = page_swap_info(page); 285 286 if (sis->flags & SWP_FILE) { 287 struct address_space *mapping = sis->swap_file->f_mapping; 288 return mapping->a_ops->set_page_dirty(page); 289 } else { 290 return __set_page_dirty_no_writeback(page); 291 } 292 } 293