fs/befs/datastream.c

   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, "---> %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  */
  89 int
  90 befs_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  */
 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, "---> %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
 165 befs_blocknr_t
 166 befs_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 */
 245 static int
 246 befs_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 */
 305 static int
 306 befs_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 */
 413 static int
 414 befs_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 }