1 /* 2 * linux/fs/befs/datastream.c 3 * 4 * Copyright (C) 2001 Will Dyson <will_dyson@pobox.com> 5 * 6 * Based on portions of file.c by Makoto Kato <m_kato@ga2.so-net.ne.jp> 7 * 8 * Many thanks to Dominic Giampaolo, author of "Practical File System 9 * Design with the Be File System", for such a helpful book. 10 * 11 */ 12 13 #include <linux/kernel.h> 14 #include <linux/buffer_head.h> 15 #include <linux/string.h> 16 17 #include "befs.h" 18 #include "datastream.h" 19 #include "io.h" 20 21 const befs_inode_addr BAD_IADDR = { 0, 0, 0 }; 22 23 static int befs_find_brun_direct(struct super_block *sb, 24 befs_data_stream * data, 25 befs_blocknr_t blockno, befs_block_run * run); 26 27 static int befs_find_brun_indirect(struct super_block *sb, 28 befs_data_stream * data, 29 befs_blocknr_t blockno, 30 befs_block_run * run); 31 32 static int befs_find_brun_dblindirect(struct super_block *sb, 33 befs_data_stream * data, 34 befs_blocknr_t blockno, 35 befs_block_run * run); 36 37 /** 38 * befs_read_datastream - get buffer_head containing data, starting from pos. 39 * @sb: Filesystem superblock 40 * @ds: datastrem to find data with 41 * @pos: start of data 42 * @off: offset of data in buffer_head->b_data 43 * 44 * Returns pointer to buffer_head containing data starting with offset @off, 45 * if you don't need to know offset just set @off = NULL. 46 */ 47 struct buffer_head * 48 befs_read_datastream(struct super_block *sb, befs_data_stream * ds, 49 befs_off_t pos, uint * off) 50 { 51 struct buffer_head *bh = NULL; 52 befs_block_run run; 53 befs_blocknr_t block; /* block coresponding to pos */ 54 55 befs_debug(sb, "---> befs_read_datastream() %Lu", pos); 56 block = pos >> BEFS_SB(sb)->block_shift; 57 if (off) 58 *off = pos - (block << BEFS_SB(sb)->block_shift); 59 60 if (befs_fblock2brun(sb, ds, block, &run) != BEFS_OK) { 61 befs_error(sb, "BeFS: Error finding disk addr of block %lu", 62 block); 63 befs_debug(sb, "<--- befs_read_datastream() ERROR"); 64 return NULL; 65 } 66 bh = befs_bread_iaddr(sb, run); 67 if (!bh) { 68 befs_error(sb, "BeFS: Error reading block %lu from datastream", 69 block); 70 return NULL; 71 } 72 73 befs_debug(sb, "<--- befs_read_datastream() read data, starting at %Lu", 74 pos); 75 76 return bh; 77 } 78 79 /* 80 * Takes a file position and gives back a brun who's starting block 81 * is block number fblock of the file. 82 * 83 * Returns BEFS_OK or BEFS_ERR. 84 * 85 * Calls specialized functions for each of the three possible 86 * datastream regions. 87 * 88 * 2001-11-15 Will Dyson 89 */ 90 int 91 befs_fblock2brun(struct super_block *sb, befs_data_stream * data, 92 befs_blocknr_t fblock, befs_block_run * run) 93 { 94 int err; 95 befs_off_t pos = fblock << BEFS_SB(sb)->block_shift; 96 97 if (pos < data->max_direct_range) { 98 err = befs_find_brun_direct(sb, data, fblock, run); 99 100 } else if (pos < data->max_indirect_range) { 101 err = befs_find_brun_indirect(sb, data, fblock, run); 102 103 } else if (pos < data->max_double_indirect_range) { 104 err = befs_find_brun_dblindirect(sb, data, fblock, run); 105 106 } else { 107 befs_error(sb, 108 "befs_fblock2brun() was asked to find block %lu, " 109 "which is not mapped by the datastream\n", fblock); 110 err = BEFS_ERR; 111 } 112 return err; 113 } 114 115 /** 116 * befs_read_lsmylink - read long symlink from datastream. 117 * @sb: Filesystem superblock 118 * @ds: Datastrem to read from 119 * @buf: Buffer in which to place long symlink data 120 * @len: Length of the long symlink in bytes 121 * 122 * Returns the number of bytes read 123 */ 124 size_t 125 befs_read_lsymlink(struct super_block * sb, befs_data_stream * ds, void *buff, 126 befs_off_t len) 127 { 128 befs_off_t bytes_read = 0; /* bytes readed */ 129 u16 plen; 130 struct buffer_head *bh = NULL; 131 befs_debug(sb, "---> befs_read_lsymlink() length: %Lu", len); 132 133 while (bytes_read < len) { 134 bh = befs_read_datastream(sb, ds, bytes_read, NULL); 135 if (!bh) { 136 befs_error(sb, "BeFS: Error reading datastream block " 137 "starting from %Lu", bytes_read); 138 befs_debug(sb, "<--- befs_read_lsymlink() ERROR"); 139 return bytes_read; 140 141 } 142 plen = ((bytes_read + BEFS_SB(sb)->block_size) < len) ? 143 BEFS_SB(sb)->block_size : len - bytes_read; 144 memcpy(buff + bytes_read, bh->b_data, plen); 145 brelse(bh); 146 bytes_read += plen; 147 } 148 149 befs_debug(sb, "<--- befs_read_lsymlink() read %u bytes", bytes_read); 150 return bytes_read; 151 } 152 153 /** 154 * befs_count_blocks - blocks used by a file 155 * @sb: Filesystem superblock 156 * @ds: Datastream of the file 157 * 158 * Counts the number of fs blocks that the file represented by 159 * inode occupies on the filesystem, counting both regular file 160 * data and filesystem metadata (and eventually attribute data 161 * when we support attributes) 162 */ 163 164 befs_blocknr_t 165 befs_count_blocks(struct super_block * sb, befs_data_stream * ds) 166 { 167 befs_blocknr_t blocks; 168 befs_blocknr_t datablocks; /* File data blocks */ 169 befs_blocknr_t metablocks; /* FS metadata blocks */ 170 befs_sb_info *befs_sb = BEFS_SB(sb); 171 172 befs_debug(sb, "---> befs_count_blocks()"); 173 174 datablocks = ds->size >> befs_sb->block_shift; 175 if (ds->size & (befs_sb->block_size - 1)) 176 datablocks += 1; 177 178 metablocks = 1; /* Start with 1 block for inode */ 179 180 /* Size of indirect block */ 181 if (ds->size > ds->max_direct_range) 182 metablocks += ds->indirect.len; 183 184 /* 185 Double indir block, plus all the indirect blocks it mapps 186 In the double-indirect range, all block runs of data are 187 BEFS_DBLINDIR_BRUN_LEN blocks long. Therefore, we know 188 how many data block runs are in the double-indirect region, 189 and from that we know how many indirect blocks it takes to 190 map them. We assume that the indirect blocks are also 191 BEFS_DBLINDIR_BRUN_LEN blocks long. 192 */ 193 if (ds->size > ds->max_indirect_range && ds->max_indirect_range != 0) { 194 uint dbl_bytes; 195 uint dbl_bruns; 196 uint indirblocks; 197 198 dbl_bytes = 199 ds->max_double_indirect_range - ds->max_indirect_range; 200 dbl_bruns = 201 dbl_bytes / (befs_sb->block_size * BEFS_DBLINDIR_BRUN_LEN); 202 indirblocks = dbl_bruns / befs_iaddrs_per_block(sb); 203 204 metablocks += ds->double_indirect.len; 205 metablocks += indirblocks; 206 } 207 208 blocks = datablocks + metablocks; 209 befs_debug(sb, "<--- befs_count_blocks() %u blocks", blocks); 210 211 return blocks; 212 } 213 214 /* 215 Finds the block run that starts at file block number blockno 216 in the file represented by the datastream data, if that 217 blockno is in the direct region of the datastream. 218 219 sb: the superblock 220 data: the datastream 221 blockno: the blocknumber to find 222 run: The found run is passed back through this pointer 223 224 Return value is BEFS_OK if the blockrun is found, BEFS_ERR 225 otherwise. 226 227 Algorithm: 228 Linear search. Checks each element of array[] to see if it 229 contains the blockno-th filesystem block. This is necessary 230 because the block runs map variable amounts of data. Simply 231 keeps a count of the number of blocks searched so far (sum), 232 incrementing this by the length of each block run as we come 233 across it. Adds sum to *count before returning (this is so 234 you can search multiple arrays that are logicaly one array, 235 as in the indirect region code). 236 237 When/if blockno is found, if blockno is inside of a block 238 run as stored on disk, we offset the start and length members 239 of the block run, so that blockno is the start and len is 240 still valid (the run ends in the same place). 241 242 2001-11-15 Will Dyson 243 */ 244 static int 245 befs_find_brun_direct(struct super_block *sb, befs_data_stream * data, 246 befs_blocknr_t blockno, befs_block_run * run) 247 { 248 int i; 249 befs_block_run *array = data->direct; 250 befs_blocknr_t sum; 251 befs_blocknr_t max_block = 252 data->max_direct_range >> BEFS_SB(sb)->block_shift; 253 254 befs_debug(sb, "---> befs_find_brun_direct(), find %lu", blockno); 255 256 if (blockno > max_block) { 257 befs_error(sb, "befs_find_brun_direct() passed block outside of" 258 "direct region"); 259 return BEFS_ERR; 260 } 261 262 for (i = 0, sum = 0; i < BEFS_NUM_DIRECT_BLOCKS; 263 sum += array[i].len, i++) { 264 if (blockno >= sum && blockno < sum + (array[i].len)) { 265 int offset = blockno - sum; 266 run->allocation_group = array[i].allocation_group; 267 run->start = array[i].start + offset; 268 run->len = array[i].len - offset; 269 270 befs_debug(sb, "---> befs_find_brun_direct(), " 271 "found %lu at direct[%d]", blockno, i); 272 return BEFS_OK; 273 } 274 } 275 276 befs_debug(sb, "---> befs_find_brun_direct() ERROR"); 277 return BEFS_ERR; 278 } 279 280 /* 281 Finds the block run that starts at file block number blockno 282 in the file represented by the datastream data, if that 283 blockno is in the indirect region of the datastream. 284 285 sb: the superblock 286 data: the datastream 287 blockno: the blocknumber to find 288 run: The found run is passed back through this pointer 289 290 Return value is BEFS_OK if the blockrun is found, BEFS_ERR 291 otherwise. 292 293 Algorithm: 294 For each block in the indirect run of the datastream, read 295 it in and search through it for search_blk. 296 297 XXX: 298 Really should check to make sure blockno is inside indirect 299 region. 300 301 2001-11-15 Will Dyson 302 */ 303 static int 304 befs_find_brun_indirect(struct super_block *sb, 305 befs_data_stream * data, befs_blocknr_t blockno, 306 befs_block_run * run) 307 { 308 int i, j; 309 befs_blocknr_t sum = 0; 310 befs_blocknr_t indir_start_blk; 311 befs_blocknr_t search_blk; 312 struct buffer_head *indirblock; 313 befs_disk_block_run *array; 314 315 befs_block_run indirect = data->indirect; 316 befs_blocknr_t indirblockno = iaddr2blockno(sb, &indirect); 317 int arraylen = befs_iaddrs_per_block(sb); 318 319 befs_debug(sb, "---> befs_find_brun_indirect(), find %lu", blockno); 320 321 indir_start_blk = data->max_direct_range >> BEFS_SB(sb)->block_shift; 322 search_blk = blockno - indir_start_blk; 323 324 /* Examine blocks of the indirect run one at a time */ 325 for (i = 0; i < indirect.len; i++) { 326 indirblock = befs_bread(sb, indirblockno + i); 327 if (indirblock == NULL) { 328 befs_debug(sb, 329 "---> befs_find_brun_indirect() failed to " 330 "read disk block %lu from the indirect brun", 331 indirblockno + i); 332 return BEFS_ERR; 333 } 334 335 array = (befs_disk_block_run *) indirblock->b_data; 336 337 for (j = 0; j < arraylen; ++j) { 338 int len = fs16_to_cpu(sb, array[j].len); 339 340 if (search_blk >= sum && search_blk < sum + len) { 341 int offset = search_blk - sum; 342 run->allocation_group = 343 fs32_to_cpu(sb, array[j].allocation_group); 344 run->start = 345 fs16_to_cpu(sb, array[j].start) + offset; 346 run->len = 347 fs16_to_cpu(sb, array[j].len) - offset; 348 349 brelse(indirblock); 350 befs_debug(sb, 351 "<--- befs_find_brun_indirect() found " 352 "file block %lu at indirect[%d]", 353 blockno, j + (i * arraylen)); 354 return BEFS_OK; 355 } 356 sum += len; 357 } 358 359 brelse(indirblock); 360 } 361 362 /* Only fallthrough is an error */ 363 befs_error(sb, "BeFS: befs_find_brun_indirect() failed to find " 364 "file block %lu", blockno); 365 366 befs_debug(sb, "<--- befs_find_brun_indirect() ERROR"); 367 return BEFS_ERR; 368 } 369 370 /* 371 Finds the block run that starts at file block number blockno 372 in the file represented by the datastream data, if that 373 blockno is in the double-indirect region of the datastream. 374 375 sb: the superblock 376 data: the datastream 377 blockno: the blocknumber to find 378 run: The found run is passed back through this pointer 379 380 Return value is BEFS_OK if the blockrun is found, BEFS_ERR 381 otherwise. 382 383 Algorithm: 384 The block runs in the double-indirect region are different. 385 They are always allocated 4 fs blocks at a time, so each 386 block run maps a constant amount of file data. This means 387 that we can directly calculate how many block runs into the 388 double-indirect region we need to go to get to the one that 389 maps a particular filesystem block. 390 391 We do this in two stages. First we calculate which of the 392 inode addresses in the double-indirect block will point us 393 to the indirect block that contains the mapping for the data, 394 then we calculate which of the inode addresses in that 395 indirect block maps the data block we are after. 396 397 Oh, and once we've done that, we actually read in the blocks 398 that contain the inode addresses we calculated above. Even 399 though the double-indirect run may be several blocks long, 400 we can calculate which of those blocks will contain the index 401 we are after and only read that one. We then follow it to 402 the indirect block and perform a similar process to find 403 the actual block run that maps the data block we are interested 404 in. 405 406 Then we offset the run as in befs_find_brun_array() and we are 407 done. 408 409 2001-11-15 Will Dyson 410 */ 411 static int 412 befs_find_brun_dblindirect(struct super_block *sb, 413 befs_data_stream * data, befs_blocknr_t blockno, 414 befs_block_run * run) 415 { 416 int dblindir_indx; 417 int indir_indx; 418 int offset; 419 int dbl_which_block; 420 int which_block; 421 int dbl_block_indx; 422 int block_indx; 423 off_t dblindir_leftover; 424 befs_blocknr_t blockno_at_run_start; 425 struct buffer_head *dbl_indir_block; 426 struct buffer_head *indir_block; 427 befs_block_run indir_run; 428 befs_disk_inode_addr *iaddr_array = NULL; 429 befs_sb_info *befs_sb = BEFS_SB(sb); 430 431 befs_blocknr_t indir_start_blk = 432 data->max_indirect_range >> befs_sb->block_shift; 433 434 off_t dbl_indir_off = blockno - indir_start_blk; 435 436 /* number of data blocks mapped by each of the iaddrs in 437 * the indirect block pointed to by the double indirect block 438 */ 439 size_t iblklen = BEFS_DBLINDIR_BRUN_LEN; 440 441 /* number of data blocks mapped by each of the iaddrs in 442 * the double indirect block 443 */ 444 size_t diblklen = iblklen * befs_iaddrs_per_block(sb) 445 * BEFS_DBLINDIR_BRUN_LEN; 446 447 befs_debug(sb, "---> befs_find_brun_dblindirect() find %lu", blockno); 448 449 /* First, discover which of the double_indir->indir blocks 450 * contains pos. Then figure out how much of pos that 451 * accounted for. Then discover which of the iaddrs in 452 * the indirect block contains pos. 453 */ 454 455 dblindir_indx = dbl_indir_off / diblklen; 456 dblindir_leftover = dbl_indir_off % diblklen; 457 indir_indx = dblindir_leftover / diblklen; 458 459 /* Read double indirect block */ 460 dbl_which_block = dblindir_indx / befs_iaddrs_per_block(sb); 461 if (dbl_which_block > data->double_indirect.len) { 462 befs_error(sb, "The double-indirect index calculated by " 463 "befs_read_brun_dblindirect(), %d, is outside the range " 464 "of the double-indirect block", dblindir_indx); 465 return BEFS_ERR; 466 } 467 468 dbl_indir_block = 469 befs_bread(sb, iaddr2blockno(sb, &data->double_indirect) + 470 dbl_which_block); 471 if (dbl_indir_block == NULL) { 472 befs_error(sb, "befs_read_brun_dblindirect() couldn't read the " 473 "double-indirect block at blockno %lu", 474 iaddr2blockno(sb, 475 &data->double_indirect) + 476 dbl_which_block); 477 brelse(dbl_indir_block); 478 return BEFS_ERR; 479 } 480 481 dbl_block_indx = 482 dblindir_indx - (dbl_which_block * befs_iaddrs_per_block(sb)); 483 iaddr_array = (befs_disk_inode_addr *) dbl_indir_block->b_data; 484 indir_run = fsrun_to_cpu(sb, iaddr_array[dbl_block_indx]); 485 brelse(dbl_indir_block); 486 iaddr_array = NULL; 487 488 /* Read indirect block */ 489 which_block = indir_indx / befs_iaddrs_per_block(sb); 490 if (which_block > indir_run.len) { 491 befs_error(sb, "The indirect index calculated by " 492 "befs_read_brun_dblindirect(), %d, is outside the range " 493 "of the indirect block", indir_indx); 494 return BEFS_ERR; 495 } 496 497 indir_block = 498 befs_bread(sb, iaddr2blockno(sb, &indir_run) + which_block); 499 if (indir_block == NULL) { 500 befs_error(sb, "befs_read_brun_dblindirect() couldn't read the " 501 "indirect block at blockno %lu", 502 iaddr2blockno(sb, &indir_run) + which_block); 503 brelse(indir_block); 504 return BEFS_ERR; 505 } 506 507 block_indx = indir_indx - (which_block * befs_iaddrs_per_block(sb)); 508 iaddr_array = (befs_disk_inode_addr *) indir_block->b_data; 509 *run = fsrun_to_cpu(sb, iaddr_array[block_indx]); 510 brelse(indir_block); 511 iaddr_array = NULL; 512 513 blockno_at_run_start = indir_start_blk; 514 blockno_at_run_start += diblklen * dblindir_indx; 515 blockno_at_run_start += iblklen * indir_indx; 516 offset = blockno - blockno_at_run_start; 517 518 run->start += offset; 519 run->len -= offset; 520 521 befs_debug(sb, "Found file block %lu in double_indirect[%d][%d]," 522 " double_indirect_leftover = %lu", 523 blockno, dblindir_indx, indir_indx, dblindir_leftover); 524 525 return BEFS_OK; 526 } 527