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