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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/befs/datastream.c
4 *
5 * Copyright (C) 2001 Will Dyson <[email protected]>
6 *
7 * Based on portions of file.c by Makoto Kato <[email protected]>
8 *
9 * Many thanks to Dominic Giampaolo, author of "Practical File System
10 * Design with the Be File System", for such a helpful book.
11 *
12 */
13
14#include <linux/kernel.h>
15#include <linux/buffer_head.h>
16#include <linux/string.h>
17
18#include "befs.h"
19#include "datastream.h"
20#include "io.h"
21
22const befs_inode_addr BAD_IADDR = { 0, 0, 0 };
23
24static int befs_find_brun_direct(struct super_block *sb,
25 const befs_data_stream *data,
26 befs_blocknr_t blockno, befs_block_run *run);
27
28static int befs_find_brun_indirect(struct super_block *sb,
29 const befs_data_stream *data,
30 befs_blocknr_t blockno,
31 befs_block_run *run);
32
33static int befs_find_brun_dblindirect(struct super_block *sb,
34 const befs_data_stream *data,
35 befs_blocknr_t blockno,
36 befs_block_run *run);
37
38/**
39 * befs_read_datastream - get buffer_head containing data, starting from pos.
40 * @sb: Filesystem superblock
41 * @ds: datastream to find data with
42 * @pos: start of data
43 * @off: offset of data in buffer_head->b_data
44 *
45 * Returns pointer to buffer_head containing data starting with offset @off,
46 * if you don't need to know offset just set @off = NULL.
47 */
48struct buffer_head *
49befs_read_datastream(struct super_block *sb, const befs_data_stream *ds,
50 befs_off_t pos, uint *off)
51{
52 struct buffer_head *bh;
53 befs_block_run run;
54 befs_blocknr_t block; /* block coresponding to pos */
55
56 befs_debug(sb, "---> %s %llu", __func__, pos);
57 block = pos >> BEFS_SB(sb)->block_shift;
58 if (off)
59 *off = pos - (block << BEFS_SB(sb)->block_shift);
60
61 if (befs_fblock2brun(sb, ds, block, &run) != BEFS_OK) {
62 befs_error(sb, "BeFS: Error finding disk addr of block %lu",
63 (unsigned long)block);
64 befs_debug(sb, "<--- %s ERROR", __func__);
65 return NULL;
66 }
67 bh = befs_bread_iaddr(sb, run);
68 if (!bh) {
69 befs_error(sb, "BeFS: Error reading block %lu from datastream",
70 (unsigned long)block);
71 return NULL;
72 }
73
74 befs_debug(sb, "<--- %s read data, starting at %llu", __func__, pos);
75
76 return bh;
77}
78
79/**
80 * befs_fblock2brun - give back block run for fblock
81 * @sb: the superblock
82 * @data: datastream to read from
83 * @fblock: the blocknumber with the file position to find
84 * @run: The found run is passed back through this pointer
85 *
86 * Takes a file position and gives back a brun who's starting block
87 * is block number fblock of the file.
88 *
89 * Returns BEFS_OK or BEFS_ERR.
90 *
91 * Calls specialized functions for each of the three possible
92 * datastream regions.
93 */
94int
95befs_fblock2brun(struct super_block *sb, const befs_data_stream *data,
96 befs_blocknr_t fblock, befs_block_run *run)
97{
98 int err;
99 befs_off_t pos = fblock << BEFS_SB(sb)->block_shift;
100
101 if (pos < data->max_direct_range) {
102 err = befs_find_brun_direct(sb, data, fblock, run);
103
104 } else if (pos < data->max_indirect_range) {
105 err = befs_find_brun_indirect(sb, data, fblock, run);
106
107 } else if (pos < data->max_double_indirect_range) {
108 err = befs_find_brun_dblindirect(sb, data, fblock, run);
109
110 } else {
111 befs_error(sb,
112 "befs_fblock2brun() was asked to find block %lu, "
113 "which is not mapped by the datastream\n",
114 (unsigned long)fblock);
115 err = BEFS_ERR;
116 }
117 return err;
118}
119
120/**
121 * befs_read_lsmylink - read long symlink from datastream.
122 * @sb: Filesystem superblock
123 * @ds: Datastream to read from
124 * @buff: Buffer in which to place long symlink data
125 * @len: Length of the long symlink in bytes
126 *
127 * Returns the number of bytes read
128 */
129size_t
130befs_read_lsymlink(struct super_block *sb, const befs_data_stream *ds,
131 void *buff, befs_off_t len)
132{
133 befs_off_t bytes_read = 0; /* bytes readed */
134 u16 plen;
135 struct buffer_head *bh;
136
137 befs_debug(sb, "---> %s length: %llu", __func__, len);
138
139 while (bytes_read < len) {
140 bh = befs_read_datastream(sb, ds, bytes_read, NULL);
141 if (!bh) {
142 befs_error(sb, "BeFS: Error reading datastream block "
143 "starting from %llu", bytes_read);
144 befs_debug(sb, "<--- %s ERROR", __func__);
145 return bytes_read;
146
147 }
148 plen = ((bytes_read + BEFS_SB(sb)->block_size) < len) ?
149 BEFS_SB(sb)->block_size : len - bytes_read;
150 memcpy(buff + bytes_read, bh->b_data, plen);
151 brelse(bh);
152 bytes_read += plen;
153 }
154
155 befs_debug(sb, "<--- %s read %u bytes", __func__, (unsigned int)
156 bytes_read);
157 return bytes_read;
158}
159
160/**
161 * befs_count_blocks - blocks used by a file
162 * @sb: Filesystem superblock
163 * @ds: Datastream of the file
164 *
165 * Counts the number of fs blocks that the file represented by
166 * inode occupies on the filesystem, counting both regular file
167 * data and filesystem metadata (and eventually attribute data
168 * when we support attributes)
169*/
170
171befs_blocknr_t
172befs_count_blocks(struct super_block *sb, const befs_data_stream *ds)
173{
174 befs_blocknr_t blocks;
175 befs_blocknr_t datablocks; /* File data blocks */
176 befs_blocknr_t metablocks; /* FS metadata blocks */
177 struct befs_sb_info *befs_sb = BEFS_SB(sb);
178
179 befs_debug(sb, "---> %s", __func__);
180
181 datablocks = ds->size >> befs_sb->block_shift;
182 if (ds->size & (befs_sb->block_size - 1))
183 datablocks += 1;
184
185 metablocks = 1; /* Start with 1 block for inode */
186
187 /* Size of indirect block */
188 if (ds->size > ds->max_direct_range)
189 metablocks += ds->indirect.len;
190
191 /*
192 * Double indir block, plus all the indirect blocks it maps.
193 * In the double-indirect range, all block runs of data are
194 * BEFS_DBLINDIR_BRUN_LEN blocks long. Therefore, we know
195 * how many data block runs are in the double-indirect region,
196 * and from that we know how many indirect blocks it takes to
197 * map them. We assume that the indirect blocks are also
198 * BEFS_DBLINDIR_BRUN_LEN blocks long.
199 */
200 if (ds->size > ds->max_indirect_range && ds->max_indirect_range != 0) {
201 uint dbl_bytes;
202 uint dbl_bruns;
203 uint indirblocks;
204
205 dbl_bytes =
206 ds->max_double_indirect_range - ds->max_indirect_range;
207 dbl_bruns =
208 dbl_bytes / (befs_sb->block_size * BEFS_DBLINDIR_BRUN_LEN);
209 indirblocks = dbl_bruns / befs_iaddrs_per_block(sb);
210
211 metablocks += ds->double_indirect.len;
212 metablocks += indirblocks;
213 }
214
215 blocks = datablocks + metablocks;
216 befs_debug(sb, "<--- %s %u blocks", __func__, (unsigned int)blocks);
217
218 return blocks;
219}
220
221/**
222 * befs_find_brun_direct - find a direct block run in the datastream
223 * @sb: the superblock
224 * @data: the datastream
225 * @blockno: the blocknumber to find
226 * @run: The found run is passed back through this pointer
227 *
228 * Finds the block run that starts at file block number blockno
229 * in the file represented by the datastream data, if that
230 * blockno is in the direct region of the datastream.
231 *
232 * Return value is BEFS_OK if the blockrun is found, BEFS_ERR
233 * otherwise.
234 *
235 * Algorithm:
236 * Linear search. Checks each element of array[] to see if it
237 * contains the blockno-th filesystem block. This is necessary
238 * because the block runs map variable amounts of data. Simply
239 * keeps a count of the number of blocks searched so far (sum),
240 * incrementing this by the length of each block run as we come
241 * across it. Adds sum to *count before returning (this is so
242 * you can search multiple arrays that are logicaly one array,
243 * as in the indirect region code).
244 *
245 * When/if blockno is found, if blockno is inside of a block
246 * run as stored on disk, we offset the start and length members
247 * of the block run, so that blockno is the start and len is
248 * still valid (the run ends in the same place).
249 */
250static int
251befs_find_brun_direct(struct super_block *sb, const befs_data_stream *data,
252 befs_blocknr_t blockno, befs_block_run *run)
253{
254 int i;
255 const befs_block_run *array = data->direct;
256 befs_blocknr_t sum;
257
258 befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno);
259
260 for (i = 0, sum = 0; i < BEFS_NUM_DIRECT_BLOCKS;
261 sum += array[i].len, i++) {
262 if (blockno >= sum && blockno < sum + (array[i].len)) {
263 int offset = blockno - sum;
264
265 run->allocation_group = array[i].allocation_group;
266 run->start = array[i].start + offset;
267 run->len = array[i].len - offset;
268
269 befs_debug(sb, "---> %s, "
270 "found %lu at direct[%d]", __func__,
271 (unsigned long)blockno, i);
272 return BEFS_OK;
273 }
274 }
275
276 befs_error(sb, "%s failed to find file block %lu", __func__,
277 (unsigned long)blockno);
278 befs_debug(sb, "---> %s ERROR", __func__);
279 return BEFS_ERR;
280}
281
282/**
283 * befs_find_brun_indirect - find a block run in the datastream
284 * @sb: the superblock
285 * @data: the datastream
286 * @blockno: the blocknumber to find
287 * @run: The found run is passed back through this pointer
288 *
289 * Finds the block run that starts at file block number blockno
290 * in the file represented by the datastream data, if that
291 * blockno is in the indirect region of the datastream.
292 *
293 * Return value is BEFS_OK if the blockrun is found, BEFS_ERR
294 * otherwise.
295 *
296 * Algorithm:
297 * For each block in the indirect run of the datastream, read
298 * it in and search through it for search_blk.
299 *
300 * XXX:
301 * Really should check to make sure blockno is inside indirect
302 * region.
303 */
304static int
305befs_find_brun_indirect(struct super_block *sb,
306 const befs_data_stream *data,
307 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 = sb_bread(sb, indirblockno + i);
329 if (indirblock == NULL) {
330 befs_error(sb, "---> %s failed to read "
331 "disk block %lu from the indirect brun",
332 __func__, (unsigned long)indirblockno + i);
333 befs_debug(sb, "<--- %s ERROR", __func__);
334 return BEFS_ERR;
335 }
336
337 array = (befs_disk_block_run *) indirblock->b_data;
338
339 for (j = 0; j < arraylen; ++j) {
340 int len = fs16_to_cpu(sb, array[j].len);
341
342 if (search_blk >= sum && search_blk < sum + len) {
343 int offset = search_blk - sum;
344 run->allocation_group =
345 fs32_to_cpu(sb, array[j].allocation_group);
346 run->start =
347 fs16_to_cpu(sb, array[j].start) + offset;
348 run->len =
349 fs16_to_cpu(sb, array[j].len) - offset;
350
351 brelse(indirblock);
352 befs_debug(sb,
353 "<--- %s found file block "
354 "%lu at indirect[%d]", __func__,
355 (unsigned long)blockno,
356 j + (i * arraylen));
357 return BEFS_OK;
358 }
359 sum += len;
360 }
361
362 brelse(indirblock);
363 }
364
365 /* Only fallthrough is an error */
366 befs_error(sb, "BeFS: %s failed to find "
367 "file block %lu", __func__, (unsigned long)blockno);
368
369 befs_debug(sb, "<--- %s ERROR", __func__);
370 return BEFS_ERR;
371}
372
373/**
374 * befs_find_brun_dblindirect - find a block run in the datastream
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 * Finds the block run that starts at file block number blockno
381 * in the file represented by the datastream data, if that
382 * blockno is in the double-indirect region of the datastream.
383 *
384 * Return value is BEFS_OK if the blockrun is found, BEFS_ERR
385 * otherwise.
386 *
387 * Algorithm:
388 * The block runs in the double-indirect region are different.
389 * They are always allocated 4 fs blocks at a time, so each
390 * block run maps a constant amount of file data. This means
391 * that we can directly calculate how many block runs into the
392 * double-indirect region we need to go to get to the one that
393 * maps a particular filesystem block.
394 *
395 * We do this in two stages. First we calculate which of the
396 * inode addresses in the double-indirect block will point us
397 * to the indirect block that contains the mapping for the data,
398 * then we calculate which of the inode addresses in that
399 * indirect block maps the data block we are after.
400 *
401 * Oh, and once we've done that, we actually read in the blocks
402 * that contain the inode addresses we calculated above. Even
403 * though the double-indirect run may be several blocks long,
404 * we can calculate which of those blocks will contain the index
405 * we are after and only read that one. We then follow it to
406 * the indirect block and perform a similar process to find
407 * the actual block run that maps the data block we are interested
408 * in.
409 *
410 * Then we offset the run as in befs_find_brun_array() and we are
411 * done.
412 */
413static int
414befs_find_brun_dblindirect(struct super_block *sb,
415 const befs_data_stream *data,
416 befs_blocknr_t blockno,
417 befs_block_run *run)
418{
419 int dblindir_indx;
420 int indir_indx;
421 int offset;
422 int dbl_which_block;
423 int which_block;
424 int dbl_block_indx;
425 int block_indx;
426 off_t dblindir_leftover;
427 befs_blocknr_t blockno_at_run_start;
428 struct buffer_head *dbl_indir_block;
429 struct buffer_head *indir_block;
430 befs_block_run indir_run;
431 befs_disk_inode_addr *iaddr_array;
432
433 befs_blocknr_t indir_start_blk =
434 data->max_indirect_range >> BEFS_SB(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 sb_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 return BEFS_ERR;
481 }
482
483 dbl_block_indx =
484 dblindir_indx - (dbl_which_block * befs_iaddrs_per_block(sb));
485 iaddr_array = (befs_disk_inode_addr *) dbl_indir_block->b_data;
486 indir_run = fsrun_to_cpu(sb, iaddr_array[dbl_block_indx]);
487 brelse(dbl_indir_block);
488
489 /* Read indirect block */
490 which_block = indir_indx / befs_iaddrs_per_block(sb);
491 if (which_block > indir_run.len) {
492 befs_error(sb, "The indirect index calculated by "
493 "%s, %d, is outside the range "
494 "of the indirect block", __func__, indir_indx);
495 return BEFS_ERR;
496 }
497
498 indir_block =
499 sb_bread(sb, iaddr2blockno(sb, &indir_run) + which_block);
500 if (indir_block == NULL) {
501 befs_error(sb, "%s couldn't read the indirect block "
502 "at blockno %lu", __func__, (unsigned long)
503 iaddr2blockno(sb, &indir_run) + which_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
512 blockno_at_run_start = indir_start_blk;
513 blockno_at_run_start += diblklen * dblindir_indx;
514 blockno_at_run_start += iblklen * indir_indx;
515 offset = blockno - blockno_at_run_start;
516
517 run->start += offset;
518 run->len -= offset;
519
520 befs_debug(sb, "Found file block %lu in double_indirect[%d][%d],"
521 " double_indirect_leftover = %lu", (unsigned long)
522 blockno, dblindir_indx, indir_indx, dblindir_leftover);
523
524 return BEFS_OK;
525}