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 21const befs_inode_addr BAD_IADDR = { 0, 0, 0 }; 22 23static int befs_find_brun_direct(struct super_block *sb, 24 befs_data_stream * data, 25 befs_blocknr_t blockno, befs_block_run * run); 26 27static 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 32static 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 */ 47struct buffer_head * 48befs_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, "---> %s %llu", __func__, 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 (unsigned long)block); 63 befs_debug(sb, "<--- %s ERROR", __func__); 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 (unsigned long)block); 70 return NULL; 71 } 72 73 befs_debug(sb, "<--- %s read data, starting at %llu", __func__, pos); 74 75 return bh; 76} 77 78/* 79 * Takes a file position and gives back a brun who's starting block 80 * is block number fblock of the file. 81 * 82 * Returns BEFS_OK or BEFS_ERR. 83 * 84 * Calls specialized functions for each of the three possible 85 * datastream regions. 86 * 87 * 2001-11-15 Will Dyson 88 */ 89int 90befs_fblock2brun(struct super_block *sb, befs_data_stream * data, 91 befs_blocknr_t fblock, befs_block_run * run) 92{ 93 int err; 94 befs_off_t pos = fblock << BEFS_SB(sb)->block_shift; 95 96 if (pos < data->max_direct_range) { 97 err = befs_find_brun_direct(sb, data, fblock, run); 98 99 } else if (pos < data->max_indirect_range) { 100 err = befs_find_brun_indirect(sb, data, fblock, run); 101 102 } else if (pos < data->max_double_indirect_range) { 103 err = befs_find_brun_dblindirect(sb, data, fblock, run); 104 105 } else { 106 befs_error(sb, 107 "befs_fblock2brun() was asked to find block %lu, " 108 "which is not mapped by the datastream\n", 109 (unsigned long)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 * @buff: 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 */ 124size_t 125befs_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, "---> %s length: %llu", __func__, 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 %llu", bytes_read); 138 befs_debug(sb, "<--- %s ERROR", __func__); 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, "<--- %s read %u bytes", __func__, (unsigned int) 150 bytes_read); 151 return bytes_read; 152} 153 154/** 155 * befs_count_blocks - blocks used by a file 156 * @sb: Filesystem superblock 157 * @ds: Datastream of the file 158 * 159 * Counts the number of fs blocks that the file represented by 160 * inode occupies on the filesystem, counting both regular file 161 * data and filesystem metadata (and eventually attribute data 162 * when we support attributes) 163*/ 164 165befs_blocknr_t 166befs_count_blocks(struct super_block * sb, befs_data_stream * ds) 167{ 168 befs_blocknr_t blocks; 169 befs_blocknr_t datablocks; /* File data blocks */ 170 befs_blocknr_t metablocks; /* FS metadata blocks */ 171 struct befs_sb_info *befs_sb = BEFS_SB(sb); 172 173 befs_debug(sb, "---> %s", __func__); 174 175 datablocks = ds->size >> befs_sb->block_shift; 176 if (ds->size & (befs_sb->block_size - 1)) 177 datablocks += 1; 178 179 metablocks = 1; /* Start with 1 block for inode */ 180 181 /* Size of indirect block */ 182 if (ds->size > ds->max_direct_range) 183 metablocks += ds->indirect.len; 184 185 /* 186 Double indir block, plus all the indirect blocks it mapps 187 In the double-indirect range, all block runs of data are 188 BEFS_DBLINDIR_BRUN_LEN blocks long. Therefore, we know 189 how many data block runs are in the double-indirect region, 190 and from that we know how many indirect blocks it takes to 191 map them. We assume that the indirect blocks are also 192 BEFS_DBLINDIR_BRUN_LEN blocks long. 193 */ 194 if (ds->size > ds->max_indirect_range && ds->max_indirect_range != 0) { 195 uint dbl_bytes; 196 uint dbl_bruns; 197 uint indirblocks; 198 199 dbl_bytes = 200 ds->max_double_indirect_range - ds->max_indirect_range; 201 dbl_bruns = 202 dbl_bytes / (befs_sb->block_size * BEFS_DBLINDIR_BRUN_LEN); 203 indirblocks = dbl_bruns / befs_iaddrs_per_block(sb); 204 205 metablocks += ds->double_indirect.len; 206 metablocks += indirblocks; 207 } 208 209 blocks = datablocks + metablocks; 210 befs_debug(sb, "<--- %s %u blocks", __func__, (unsigned int)blocks); 211 212 return blocks; 213} 214 215/* 216 Finds the block run that starts at file block number blockno 217 in the file represented by the datastream data, if that 218 blockno is in the direct region of the datastream. 219 220 sb: the superblock 221 data: the datastream 222 blockno: the blocknumber to find 223 run: The found run is passed back through this pointer 224 225 Return value is BEFS_OK if the blockrun is found, BEFS_ERR 226 otherwise. 227 228 Algorithm: 229 Linear search. Checks each element of array[] to see if it 230 contains the blockno-th filesystem block. This is necessary 231 because the block runs map variable amounts of data. Simply 232 keeps a count of the number of blocks searched so far (sum), 233 incrementing this by the length of each block run as we come 234 across it. Adds sum to *count before returning (this is so 235 you can search multiple arrays that are logicaly one array, 236 as in the indirect region code). 237 238 When/if blockno is found, if blockno is inside of a block 239 run as stored on disk, we offset the start and length members 240 of the block run, so that blockno is the start and len is 241 still valid (the run ends in the same place). 242 243 2001-11-15 Will Dyson 244*/ 245static int 246befs_find_brun_direct(struct super_block *sb, befs_data_stream * data, 247 befs_blocknr_t blockno, befs_block_run * run) 248{ 249 int i; 250 befs_block_run *array = data->direct; 251 befs_blocknr_t sum; 252 befs_blocknr_t max_block = 253 data->max_direct_range >> BEFS_SB(sb)->block_shift; 254 255 befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno); 256 257 if (blockno > max_block) { 258 befs_error(sb, "%s passed block outside of direct region", 259 __func__); 260 return BEFS_ERR; 261 } 262 263 for (i = 0, sum = 0; i < BEFS_NUM_DIRECT_BLOCKS; 264 sum += array[i].len, i++) { 265 if (blockno >= sum && blockno < sum + (array[i].len)) { 266 int offset = blockno - sum; 267 run->allocation_group = array[i].allocation_group; 268 run->start = array[i].start + offset; 269 run->len = array[i].len - offset; 270 271 befs_debug(sb, "---> %s, " 272 "found %lu at direct[%d]", __func__, 273 (unsigned long)blockno, i); 274 return BEFS_OK; 275 } 276 } 277 278 befs_debug(sb, "---> %s ERROR", __func__); 279 return BEFS_ERR; 280} 281 282/* 283 Finds the block run that starts at file block number blockno 284 in the file represented by the datastream data, if that 285 blockno is in the indirect region of the datastream. 286 287 sb: the superblock 288 data: the datastream 289 blockno: the blocknumber to find 290 run: The found run is passed back through this pointer 291 292 Return value is BEFS_OK if the blockrun is found, BEFS_ERR 293 otherwise. 294 295 Algorithm: 296 For each block in the indirect run of the datastream, read 297 it in and search through it for search_blk. 298 299 XXX: 300 Really should check to make sure blockno is inside indirect 301 region. 302 303 2001-11-15 Will Dyson 304*/ 305static int 306befs_find_brun_indirect(struct super_block *sb, 307 befs_data_stream * data, befs_blocknr_t blockno, 308 befs_block_run * run) 309{ 310 int i, j; 311 befs_blocknr_t sum = 0; 312 befs_blocknr_t indir_start_blk; 313 befs_blocknr_t search_blk; 314 struct buffer_head *indirblock; 315 befs_disk_block_run *array; 316 317 befs_block_run indirect = data->indirect; 318 befs_blocknr_t indirblockno = iaddr2blockno(sb, &indirect); 319 int arraylen = befs_iaddrs_per_block(sb); 320 321 befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno); 322 323 indir_start_blk = data->max_direct_range >> BEFS_SB(sb)->block_shift; 324 search_blk = blockno - indir_start_blk; 325 326 /* Examine blocks of the indirect run one at a time */ 327 for (i = 0; i < indirect.len; i++) { 328 indirblock = befs_bread(sb, indirblockno + i); 329 if (indirblock == NULL) { 330 befs_debug(sb, "---> %s failed to read " 331 "disk block %lu from the indirect brun", 332 __func__, (unsigned long)indirblockno + i); 333 return BEFS_ERR; 334 } 335 336 array = (befs_disk_block_run *) indirblock->b_data; 337 338 for (j = 0; j < arraylen; ++j) { 339 int len = fs16_to_cpu(sb, array[j].len); 340 341 if (search_blk >= sum && search_blk < sum + len) { 342 int offset = search_blk - sum; 343 run->allocation_group = 344 fs32_to_cpu(sb, array[j].allocation_group); 345 run->start = 346 fs16_to_cpu(sb, array[j].start) + offset; 347 run->len = 348 fs16_to_cpu(sb, array[j].len) - offset; 349 350 brelse(indirblock); 351 befs_debug(sb, 352 "<--- %s found file block " 353 "%lu at indirect[%d]", __func__, 354 (unsigned long)blockno, 355 j + (i * arraylen)); 356 return BEFS_OK; 357 } 358 sum += len; 359 } 360 361 brelse(indirblock); 362 } 363 364 /* Only fallthrough is an error */ 365 befs_error(sb, "BeFS: %s failed to find " 366 "file block %lu", __func__, (unsigned long)blockno); 367 368 befs_debug(sb, "<--- %s ERROR", __func__); 369 return BEFS_ERR; 370} 371 372/* 373 Finds the block run that starts at file block number blockno 374 in the file represented by the datastream data, if that 375 blockno is in the double-indirect region of the datastream. 376 377 sb: the superblock 378 data: the datastream 379 blockno: the blocknumber to find 380 run: The found run is passed back through this pointer 381 382 Return value is BEFS_OK if the blockrun is found, BEFS_ERR 383 otherwise. 384 385 Algorithm: 386 The block runs in the double-indirect region are different. 387 They are always allocated 4 fs blocks at a time, so each 388 block run maps a constant amount of file data. This means 389 that we can directly calculate how many block runs into the 390 double-indirect region we need to go to get to the one that 391 maps a particular filesystem block. 392 393 We do this in two stages. First we calculate which of the 394 inode addresses in the double-indirect block will point us 395 to the indirect block that contains the mapping for the data, 396 then we calculate which of the inode addresses in that 397 indirect block maps the data block we are after. 398 399 Oh, and once we've done that, we actually read in the blocks 400 that contain the inode addresses we calculated above. Even 401 though the double-indirect run may be several blocks long, 402 we can calculate which of those blocks will contain the index 403 we are after and only read that one. We then follow it to 404 the indirect block and perform a similar process to find 405 the actual block run that maps the data block we are interested 406 in. 407 408 Then we offset the run as in befs_find_brun_array() and we are 409 done. 410 411 2001-11-15 Will Dyson 412*/ 413static int 414befs_find_brun_dblindirect(struct super_block *sb, 415 befs_data_stream * data, befs_blocknr_t blockno, 416 befs_block_run * run) 417{ 418 int dblindir_indx; 419 int indir_indx; 420 int offset; 421 int dbl_which_block; 422 int which_block; 423 int dbl_block_indx; 424 int block_indx; 425 off_t dblindir_leftover; 426 befs_blocknr_t blockno_at_run_start; 427 struct buffer_head *dbl_indir_block; 428 struct buffer_head *indir_block; 429 befs_block_run indir_run; 430 befs_disk_inode_addr *iaddr_array = NULL; 431 struct befs_sb_info *befs_sb = BEFS_SB(sb); 432 433 befs_blocknr_t indir_start_blk = 434 data->max_indirect_range >> befs_sb->block_shift; 435 436 off_t dbl_indir_off = blockno - indir_start_blk; 437 438 /* number of data blocks mapped by each of the iaddrs in 439 * the indirect block pointed to by the double indirect block 440 */ 441 size_t iblklen = BEFS_DBLINDIR_BRUN_LEN; 442 443 /* number of data blocks mapped by each of the iaddrs in 444 * the double indirect block 445 */ 446 size_t diblklen = iblklen * befs_iaddrs_per_block(sb) 447 * BEFS_DBLINDIR_BRUN_LEN; 448 449 befs_debug(sb, "---> %s find %lu", __func__, (unsigned long)blockno); 450 451 /* First, discover which of the double_indir->indir blocks 452 * contains pos. Then figure out how much of pos that 453 * accounted for. Then discover which of the iaddrs in 454 * the indirect block contains pos. 455 */ 456 457 dblindir_indx = dbl_indir_off / diblklen; 458 dblindir_leftover = dbl_indir_off % diblklen; 459 indir_indx = dblindir_leftover / diblklen; 460 461 /* Read double indirect block */ 462 dbl_which_block = dblindir_indx / befs_iaddrs_per_block(sb); 463 if (dbl_which_block > data->double_indirect.len) { 464 befs_error(sb, "The double-indirect index calculated by " 465 "%s, %d, is outside the range " 466 "of the double-indirect block", __func__, 467 dblindir_indx); 468 return BEFS_ERR; 469 } 470 471 dbl_indir_block = 472 befs_bread(sb, iaddr2blockno(sb, &data->double_indirect) + 473 dbl_which_block); 474 if (dbl_indir_block == NULL) { 475 befs_error(sb, "%s couldn't read the " 476 "double-indirect block at blockno %lu", __func__, 477 (unsigned long) 478 iaddr2blockno(sb, &data->double_indirect) + 479 dbl_which_block); 480 brelse(dbl_indir_block); 481 return BEFS_ERR; 482 } 483 484 dbl_block_indx = 485 dblindir_indx - (dbl_which_block * befs_iaddrs_per_block(sb)); 486 iaddr_array = (befs_disk_inode_addr *) dbl_indir_block->b_data; 487 indir_run = fsrun_to_cpu(sb, iaddr_array[dbl_block_indx]); 488 brelse(dbl_indir_block); 489 iaddr_array = NULL; 490 491 /* Read indirect block */ 492 which_block = indir_indx / befs_iaddrs_per_block(sb); 493 if (which_block > indir_run.len) { 494 befs_error(sb, "The indirect index calculated by " 495 "%s, %d, is outside the range " 496 "of the indirect block", __func__, indir_indx); 497 return BEFS_ERR; 498 } 499 500 indir_block = 501 befs_bread(sb, iaddr2blockno(sb, &indir_run) + which_block); 502 if (indir_block == NULL) { 503 befs_error(sb, "%s couldn't read the indirect block " 504 "at blockno %lu", __func__, (unsigned long) 505 iaddr2blockno(sb, &indir_run) + which_block); 506 brelse(indir_block); 507 return BEFS_ERR; 508 } 509 510 block_indx = indir_indx - (which_block * befs_iaddrs_per_block(sb)); 511 iaddr_array = (befs_disk_inode_addr *) indir_block->b_data; 512 *run = fsrun_to_cpu(sb, iaddr_array[block_indx]); 513 brelse(indir_block); 514 iaddr_array = NULL; 515 516 blockno_at_run_start = indir_start_blk; 517 blockno_at_run_start += diblklen * dblindir_indx; 518 blockno_at_run_start += iblklen * indir_indx; 519 offset = blockno - blockno_at_run_start; 520 521 run->start += offset; 522 run->len -= offset; 523 524 befs_debug(sb, "Found file block %lu in double_indirect[%d][%d]," 525 " double_indirect_leftover = %lu", (unsigned long) 526 blockno, dblindir_indx, indir_indx, dblindir_leftover); 527 528 return BEFS_OK; 529} 530