2 * linux/fs/befs/datastream.c
4 * Copyright (C) 2001 Will Dyson <will_dyson@pobox.com>
6 * Based on portions of file.c by Makoto Kato <m_kato@ga2.so-net.ne.jp>
8 * Many thanks to Dominic Giampaolo, author of "Practical File System
9 * Design with the Be File System", for such a helpful book.
13 #include <linux/kernel.h>
14 #include <linux/buffer_head.h>
15 #include <linux/string.h>
18 #include "datastream.h"
21 const befs_inode_addr BAD_IADDR = { 0, 0, 0 };
23 static int befs_find_brun_direct(struct super_block *sb,
24 const befs_data_stream *data,
25 befs_blocknr_t blockno, befs_block_run *run);
27 static int befs_find_brun_indirect(struct super_block *sb,
28 const befs_data_stream *data,
29 befs_blocknr_t blockno,
32 static int befs_find_brun_dblindirect(struct super_block *sb,
33 const befs_data_stream *data,
34 befs_blocknr_t blockno,
38 * befs_read_datastream - get buffer_head containing data, starting from pos.
39 * @sb: Filesystem superblock
40 * @ds: datastream to find data with
42 * @off: offset of data in buffer_head->b_data
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.
48 befs_read_datastream(struct super_block *sb, const befs_data_stream *ds,
49 befs_off_t pos, uint *off)
51 struct buffer_head *bh;
53 befs_blocknr_t block; /* block coresponding to pos */
55 befs_debug(sb, "---> %s %llu", __func__, pos);
56 block = pos >> BEFS_SB(sb)->block_shift;
58 *off = pos - (block << BEFS_SB(sb)->block_shift);
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__);
66 bh = befs_bread_iaddr(sb, run);
68 befs_error(sb, "BeFS: Error reading block %lu from datastream",
69 (unsigned long)block);
73 befs_debug(sb, "<--- %s read data, starting at %llu", __func__, pos);
79 * befs_fblock2brun - give back block run for fblock
81 * @data: datastream to read from
82 * @fblock: the blocknumber with the file position to find
83 * @run: The found run is passed back through this pointer
85 * Takes a file position and gives back a brun who's starting block
86 * is block number fblock of the file.
88 * Returns BEFS_OK or BEFS_ERR.
90 * Calls specialized functions for each of the three possible
94 befs_fblock2brun(struct super_block *sb, const befs_data_stream *data,
95 befs_blocknr_t fblock, befs_block_run *run)
98 befs_off_t pos = fblock << BEFS_SB(sb)->block_shift;
100 if (pos < data->max_direct_range) {
101 err = befs_find_brun_direct(sb, data, fblock, run);
103 } else if (pos < data->max_indirect_range) {
104 err = befs_find_brun_indirect(sb, data, fblock, run);
106 } else if (pos < data->max_double_indirect_range) {
107 err = befs_find_brun_dblindirect(sb, data, fblock, run);
111 "befs_fblock2brun() was asked to find block %lu, "
112 "which is not mapped by the datastream\n",
113 (unsigned long)fblock);
120 * befs_read_lsmylink - read long symlink from datastream.
121 * @sb: Filesystem superblock
122 * @ds: Datastream to read from
123 * @buff: Buffer in which to place long symlink data
124 * @len: Length of the long symlink in bytes
126 * Returns the number of bytes read
129 befs_read_lsymlink(struct super_block *sb, const befs_data_stream *ds,
130 void *buff, befs_off_t len)
132 befs_off_t bytes_read = 0; /* bytes readed */
134 struct buffer_head *bh;
136 befs_debug(sb, "---> %s length: %llu", __func__, len);
138 while (bytes_read < len) {
139 bh = befs_read_datastream(sb, ds, bytes_read, NULL);
141 befs_error(sb, "BeFS: Error reading datastream block "
142 "starting from %llu", bytes_read);
143 befs_debug(sb, "<--- %s ERROR", __func__);
147 plen = ((bytes_read + BEFS_SB(sb)->block_size) < len) ?
148 BEFS_SB(sb)->block_size : len - bytes_read;
149 memcpy(buff + bytes_read, bh->b_data, plen);
154 befs_debug(sb, "<--- %s read %u bytes", __func__, (unsigned int)
160 * befs_count_blocks - blocks used by a file
161 * @sb: Filesystem superblock
162 * @ds: Datastream of the file
164 * Counts the number of fs blocks that the file represented by
165 * inode occupies on the filesystem, counting both regular file
166 * data and filesystem metadata (and eventually attribute data
167 * when we support attributes)
171 befs_count_blocks(struct super_block *sb, const befs_data_stream *ds)
173 befs_blocknr_t blocks;
174 befs_blocknr_t datablocks; /* File data blocks */
175 befs_blocknr_t metablocks; /* FS metadata blocks */
176 struct befs_sb_info *befs_sb = BEFS_SB(sb);
178 befs_debug(sb, "---> %s", __func__);
180 datablocks = ds->size >> befs_sb->block_shift;
181 if (ds->size & (befs_sb->block_size - 1))
184 metablocks = 1; /* Start with 1 block for inode */
186 /* Size of indirect block */
187 if (ds->size > ds->max_direct_range)
188 metablocks += ds->indirect.len;
191 * Double indir block, plus all the indirect blocks it maps.
192 * In the double-indirect range, all block runs of data are
193 * BEFS_DBLINDIR_BRUN_LEN blocks long. Therefore, we know
194 * how many data block runs are in the double-indirect region,
195 * and from that we know how many indirect blocks it takes to
196 * map them. We assume that the indirect blocks are also
197 * BEFS_DBLINDIR_BRUN_LEN blocks long.
199 if (ds->size > ds->max_indirect_range && ds->max_indirect_range != 0) {
205 ds->max_double_indirect_range - ds->max_indirect_range;
207 dbl_bytes / (befs_sb->block_size * BEFS_DBLINDIR_BRUN_LEN);
208 indirblocks = dbl_bruns / befs_iaddrs_per_block(sb);
210 metablocks += ds->double_indirect.len;
211 metablocks += indirblocks;
214 blocks = datablocks + metablocks;
215 befs_debug(sb, "<--- %s %u blocks", __func__, (unsigned int)blocks);
221 * befs_find_brun_direct - find a direct block run in the datastream
222 * @sb: the superblock
223 * @data: the datastream
224 * @blockno: the blocknumber to find
225 * @run: The found run is passed back through this pointer
227 * Finds the block run that starts at file block number blockno
228 * in the file represented by the datastream data, if that
229 * blockno is in the direct region of the datastream.
231 * Return value is BEFS_OK if the blockrun is found, BEFS_ERR
235 * Linear search. Checks each element of array[] to see if it
236 * contains the blockno-th filesystem block. This is necessary
237 * because the block runs map variable amounts of data. Simply
238 * keeps a count of the number of blocks searched so far (sum),
239 * incrementing this by the length of each block run as we come
240 * across it. Adds sum to *count before returning (this is so
241 * you can search multiple arrays that are logicaly one array,
242 * as in the indirect region code).
244 * When/if blockno is found, if blockno is inside of a block
245 * run as stored on disk, we offset the start and length members
246 * of the block run, so that blockno is the start and len is
247 * still valid (the run ends in the same place).
250 befs_find_brun_direct(struct super_block *sb, const befs_data_stream *data,
251 befs_blocknr_t blockno, befs_block_run *run)
254 const befs_block_run *array = data->direct;
257 befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno);
259 for (i = 0, sum = 0; i < BEFS_NUM_DIRECT_BLOCKS;
260 sum += array[i].len, i++) {
261 if (blockno >= sum && blockno < sum + (array[i].len)) {
262 int offset = blockno - sum;
264 run->allocation_group = array[i].allocation_group;
265 run->start = array[i].start + offset;
266 run->len = array[i].len - offset;
268 befs_debug(sb, "---> %s, "
269 "found %lu at direct[%d]", __func__,
270 (unsigned long)blockno, i);
275 befs_error(sb, "%s failed to find file block %lu", __func__,
276 (unsigned long)blockno);
277 befs_debug(sb, "---> %s ERROR", __func__);
282 * befs_find_brun_indirect - find a block run in the datastream
283 * @sb: the superblock
284 * @data: the datastream
285 * @blockno: the blocknumber to find
286 * @run: The found run is passed back through this pointer
288 * Finds the block run that starts at file block number blockno
289 * in the file represented by the datastream data, if that
290 * blockno is in the indirect region of the datastream.
292 * Return value is BEFS_OK if the blockrun is found, BEFS_ERR
296 * For each block in the indirect run of the datastream, read
297 * it in and search through it for search_blk.
300 * Really should check to make sure blockno is inside indirect
304 befs_find_brun_indirect(struct super_block *sb,
305 const befs_data_stream *data,
306 befs_blocknr_t blockno,
310 befs_blocknr_t sum = 0;
311 befs_blocknr_t indir_start_blk;
312 befs_blocknr_t search_blk;
313 struct buffer_head *indirblock;
314 befs_disk_block_run *array;
316 befs_block_run indirect = data->indirect;
317 befs_blocknr_t indirblockno = iaddr2blockno(sb, &indirect);
318 int arraylen = befs_iaddrs_per_block(sb);
320 befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno);
322 indir_start_blk = data->max_direct_range >> BEFS_SB(sb)->block_shift;
323 search_blk = blockno - indir_start_blk;
325 /* Examine blocks of the indirect run one at a time */
326 for (i = 0; i < indirect.len; i++) {
327 indirblock = sb_bread(sb, indirblockno + i);
328 if (indirblock == NULL) {
329 befs_error(sb, "---> %s failed to read "
330 "disk block %lu from the indirect brun",
331 __func__, (unsigned long)indirblockno + i);
332 befs_debug(sb, "<--- %s ERROR", __func__);
336 array = (befs_disk_block_run *) indirblock->b_data;
338 for (j = 0; j < arraylen; ++j) {
339 int len = fs16_to_cpu(sb, array[j].len);
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);
346 fs16_to_cpu(sb, array[j].start) + offset;
348 fs16_to_cpu(sb, array[j].len) - offset;
352 "<--- %s found file block "
353 "%lu at indirect[%d]", __func__,
354 (unsigned long)blockno,
364 /* Only fallthrough is an error */
365 befs_error(sb, "BeFS: %s failed to find "
366 "file block %lu", __func__, (unsigned long)blockno);
368 befs_debug(sb, "<--- %s ERROR", __func__);
373 * befs_find_brun_dblindirect - find a block run in the datastream
374 * @sb: the superblock
375 * @data: the datastream
376 * @blockno: the blocknumber to find
377 * @run: The found run is passed back through this pointer
379 * Finds the block run that starts at file block number blockno
380 * in the file represented by the datastream data, if that
381 * blockno is in the double-indirect region of the datastream.
383 * Return value is BEFS_OK if the blockrun is found, BEFS_ERR
387 * The block runs in the double-indirect region are different.
388 * They are always allocated 4 fs blocks at a time, so each
389 * block run maps a constant amount of file data. This means
390 * that we can directly calculate how many block runs into the
391 * double-indirect region we need to go to get to the one that
392 * maps a particular filesystem block.
394 * We do this in two stages. First we calculate which of the
395 * inode addresses in the double-indirect block will point us
396 * to the indirect block that contains the mapping for the data,
397 * then we calculate which of the inode addresses in that
398 * indirect block maps the data block we are after.
400 * Oh, and once we've done that, we actually read in the blocks
401 * that contain the inode addresses we calculated above. Even
402 * though the double-indirect run may be several blocks long,
403 * we can calculate which of those blocks will contain the index
404 * we are after and only read that one. We then follow it to
405 * the indirect block and perform a similar process to find
406 * the actual block run that maps the data block we are interested
409 * Then we offset the run as in befs_find_brun_array() and we are
413 befs_find_brun_dblindirect(struct super_block *sb,
414 const befs_data_stream *data,
415 befs_blocknr_t blockno,
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;
432 befs_blocknr_t indir_start_blk =
433 data->max_indirect_range >> BEFS_SB(sb)->block_shift;
435 off_t dbl_indir_off = blockno - indir_start_blk;
437 /* number of data blocks mapped by each of the iaddrs in
438 * the indirect block pointed to by the double indirect block
440 size_t iblklen = BEFS_DBLINDIR_BRUN_LEN;
442 /* number of data blocks mapped by each of the iaddrs in
443 * the double indirect block
445 size_t diblklen = iblklen * befs_iaddrs_per_block(sb)
446 * BEFS_DBLINDIR_BRUN_LEN;
448 befs_debug(sb, "---> %s find %lu", __func__, (unsigned long)blockno);
450 /* First, discover which of the double_indir->indir blocks
451 * contains pos. Then figure out how much of pos that
452 * accounted for. Then discover which of the iaddrs in
453 * the indirect block contains pos.
456 dblindir_indx = dbl_indir_off / diblklen;
457 dblindir_leftover = dbl_indir_off % diblklen;
458 indir_indx = dblindir_leftover / diblklen;
460 /* Read double indirect block */
461 dbl_which_block = dblindir_indx / befs_iaddrs_per_block(sb);
462 if (dbl_which_block > data->double_indirect.len) {
463 befs_error(sb, "The double-indirect index calculated by "
464 "%s, %d, is outside the range "
465 "of the double-indirect block", __func__,
471 sb_bread(sb, iaddr2blockno(sb, &data->double_indirect) +
473 if (dbl_indir_block == NULL) {
474 befs_error(sb, "%s couldn't read the "
475 "double-indirect block at blockno %lu", __func__,
477 iaddr2blockno(sb, &data->double_indirect) +
483 dblindir_indx - (dbl_which_block * befs_iaddrs_per_block(sb));
484 iaddr_array = (befs_disk_inode_addr *) dbl_indir_block->b_data;
485 indir_run = fsrun_to_cpu(sb, iaddr_array[dbl_block_indx]);
486 brelse(dbl_indir_block);
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 "%s, %d, is outside the range "
493 "of the indirect block", __func__, indir_indx);
498 sb_bread(sb, iaddr2blockno(sb, &indir_run) + which_block);
499 if (indir_block == NULL) {
500 befs_error(sb, "%s couldn't read the indirect block "
501 "at blockno %lu", __func__, (unsigned long)
502 iaddr2blockno(sb, &indir_run) + which_block);
506 block_indx = indir_indx - (which_block * befs_iaddrs_per_block(sb));
507 iaddr_array = (befs_disk_inode_addr *) indir_block->b_data;
508 *run = fsrun_to_cpu(sb, iaddr_array[block_indx]);
511 blockno_at_run_start = indir_start_blk;
512 blockno_at_run_start += diblklen * dblindir_indx;
513 blockno_at_run_start += iblklen * indir_indx;
514 offset = blockno - blockno_at_run_start;
516 run->start += offset;
519 befs_debug(sb, "Found file block %lu in double_indirect[%d][%d],"
520 " double_indirect_leftover = %lu", (unsigned long)
521 blockno, dblindir_indx, indir_indx, dblindir_leftover);