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bigbiff bigbiff9c754052013-01-09 09:09:08 -05001/*
2 cluster.c (03.09.09)
3 exFAT file system implementation library.
4
bigbiff bigbiffca829c42013-01-28 08:14:25 -05005 Copyright (C) 2010-2013 Andrew Nayenko
bigbiff bigbiff9c754052013-01-09 09:09:08 -05006
7 This program is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
19*/
20
21#include "exfat.h"
22#include <errno.h>
23#include <string.h>
24
25/*
26 * Sector to absolute offset.
27 */
28static off64_t s2o(const struct exfat* ef, off64_t sector)
29{
30 return sector << ef->sb->sector_bits;
31}
32
33/*
34 * Cluster to sector.
35 */
36static off64_t c2s(const struct exfat* ef, cluster_t cluster)
37{
38 if (cluster < EXFAT_FIRST_DATA_CLUSTER)
39 exfat_bug("invalid cluster number %u", cluster);
40 return le32_to_cpu(ef->sb->cluster_sector_start) +
41 ((off64_t) (cluster - EXFAT_FIRST_DATA_CLUSTER) << ef->sb->spc_bits);
42}
43
44/*
45 * Cluster to absolute offset.
46 */
47off64_t exfat_c2o(const struct exfat* ef, cluster_t cluster)
48{
49 return s2o(ef, c2s(ef, cluster));
50}
51
52/*
53 * Sector to cluster.
54 */
55static cluster_t s2c(const struct exfat* ef, off64_t sector)
56{
57 return ((sector - le32_to_cpu(ef->sb->cluster_sector_start)) >>
58 ef->sb->spc_bits) + EXFAT_FIRST_DATA_CLUSTER;
59}
60
61/*
62 * Size in bytes to size in clusters (rounded upwards).
63 */
64static uint32_t bytes2clusters(const struct exfat* ef, uint64_t bytes)
65{
66 uint64_t cluster_size = CLUSTER_SIZE(*ef->sb);
67 return (bytes + cluster_size - 1) / cluster_size;
68}
69
70cluster_t exfat_next_cluster(const struct exfat* ef,
71 const struct exfat_node* node, cluster_t cluster)
72{
73 le32_t next;
74 off64_t fat_offset;
75
76 if (cluster < EXFAT_FIRST_DATA_CLUSTER)
77 exfat_bug("bad cluster 0x%x", cluster);
78
79 if (IS_CONTIGUOUS(*node))
80 return cluster + 1;
81 fat_offset = s2o(ef, le32_to_cpu(ef->sb->fat_sector_start))
82 + cluster * sizeof(cluster_t);
83 exfat_pread(ef->dev, &next, sizeof(next), fat_offset);
84 return le32_to_cpu(next);
85}
86
87cluster_t exfat_advance_cluster(const struct exfat* ef,
88 struct exfat_node* node, uint32_t count)
89{
90 uint32_t i;
91
92 if (node->fptr_index > count)
93 {
94 node->fptr_index = 0;
95 node->fptr_cluster = node->start_cluster;
96 }
97
98 for (i = node->fptr_index; i < count; i++)
99 {
100 node->fptr_cluster = exfat_next_cluster(ef, node, node->fptr_cluster);
101 if (CLUSTER_INVALID(node->fptr_cluster))
102 break; /* the caller should handle this and print appropriate
103 error message */
104 }
105 node->fptr_index = count;
106 return node->fptr_cluster;
107}
108
109static cluster_t find_bit_and_set(uint8_t* bitmap, cluster_t start,
110 cluster_t end)
111{
112 const cluster_t mid_start = (start + 7) / 8 * 8;
113 const cluster_t mid_end = end / 8 * 8;
114 cluster_t c;
115 cluster_t byte;
116
117 for (c = start; c < mid_start; c++)
118 if (BMAP_GET(bitmap, c) == 0)
119 {
120 BMAP_SET(bitmap, c);
121 return c + EXFAT_FIRST_DATA_CLUSTER;
122 }
123
124 for (byte = mid_start / 8; byte < mid_end / 8; byte++)
125 if (bitmap[byte] != 0xff)
126 {
127 cluster_t bit;
128
129 for (bit = 0; bit < 8; bit++)
130 if (!(bitmap[byte] & (1u << bit)))
131 {
132 bitmap[byte] |= (1u << bit);
133 return byte * 8 + bit + EXFAT_FIRST_DATA_CLUSTER;
134 }
135 }
136
137 for (c = mid_end; c < end; c++)
138 if (BMAP_GET(bitmap, c) == 0)
139 {
140 BMAP_SET(bitmap, c);
141 return c + EXFAT_FIRST_DATA_CLUSTER;
142 }
143
144 return EXFAT_CLUSTER_END;
145}
146
147void exfat_flush_cmap(struct exfat* ef)
148{
149 exfat_pwrite(ef->dev, ef->cmap.chunk, (ef->cmap.chunk_size + 7) / 8,
150 exfat_c2o(ef, ef->cmap.start_cluster));
151 ef->cmap.dirty = false;
152}
153
154static void set_next_cluster(const struct exfat* ef, int contiguous,
155 cluster_t current, cluster_t next)
156{
157 off64_t fat_offset;
158 le32_t next_le32;
159
160 if (contiguous)
161 return;
162 fat_offset = s2o(ef, le32_to_cpu(ef->sb->fat_sector_start))
163 + current * sizeof(cluster_t);
164 next_le32 = cpu_to_le32(next);
165 exfat_pwrite(ef->dev, &next_le32, sizeof(next_le32), fat_offset);
166}
167
168static cluster_t allocate_cluster(struct exfat* ef, cluster_t hint)
169{
170 cluster_t cluster;
171
172 hint -= EXFAT_FIRST_DATA_CLUSTER;
173 if (hint >= ef->cmap.chunk_size)
174 hint = 0;
175
176 cluster = find_bit_and_set(ef->cmap.chunk, hint, ef->cmap.chunk_size);
177 if (cluster == EXFAT_CLUSTER_END)
178 cluster = find_bit_and_set(ef->cmap.chunk, 0, hint);
179 if (cluster == EXFAT_CLUSTER_END)
180 {
181 exfat_error("no free space left");
182 return EXFAT_CLUSTER_END;
183 }
184
185 ef->cmap.dirty = true;
186 return cluster;
187}
188
189static void free_cluster(struct exfat* ef, cluster_t cluster)
190{
191 if (CLUSTER_INVALID(cluster))
192 exfat_bug("freeing invalid cluster 0x%x", cluster);
193 if (cluster - EXFAT_FIRST_DATA_CLUSTER >= ef->cmap.size)
194 exfat_bug("freeing non-existing cluster 0x%x (0x%x)", cluster,
195 ef->cmap.size);
196
197 BMAP_CLR(ef->cmap.chunk, cluster - EXFAT_FIRST_DATA_CLUSTER);
198 ef->cmap.dirty = true;
199}
200
201static void make_noncontiguous(const struct exfat* ef, cluster_t first,
202 cluster_t last)
203{
204 cluster_t c;
205
206 for (c = first; c < last; c++)
207 set_next_cluster(ef, 0, c, c + 1);
208}
209
210static int shrink_file(struct exfat* ef, struct exfat_node* node,
211 uint32_t current, uint32_t difference);
212
213static int grow_file(struct exfat* ef, struct exfat_node* node,
214 uint32_t current, uint32_t difference)
215{
216 cluster_t previous;
217 cluster_t next;
218 uint32_t allocated = 0;
219
220 if (difference == 0)
221 exfat_bug("zero clusters count passed");
222
223 if (node->start_cluster != EXFAT_CLUSTER_FREE)
224 {
225 /* get the last cluster of the file */
226 previous = exfat_advance_cluster(ef, node, current - 1);
227 if (CLUSTER_INVALID(previous))
228 {
229 exfat_error("invalid cluster 0x%x while growing", previous);
230 return -EIO;
231 }
232 }
233 else
234 {
235 if (node->fptr_index != 0)
236 exfat_bug("non-zero pointer index (%u)", node->fptr_index);
237 /* file does not have clusters (i.e. is empty), allocate
238 the first one for it */
239 previous = allocate_cluster(ef, 0);
240 if (CLUSTER_INVALID(previous))
241 return -ENOSPC;
242 node->fptr_cluster = node->start_cluster = previous;
243 allocated = 1;
244 /* file consists of only one cluster, so it's contiguous */
245 node->flags |= EXFAT_ATTRIB_CONTIGUOUS;
246 }
247
248 while (allocated < difference)
249 {
250 next = allocate_cluster(ef, previous + 1);
251 if (CLUSTER_INVALID(next))
252 {
253 if (allocated != 0)
254 shrink_file(ef, node, current + allocated, allocated);
255 return -ENOSPC;
256 }
257 if (next != previous - 1 && IS_CONTIGUOUS(*node))
258 {
259 /* it's a pity, but we are not able to keep the file contiguous
260 anymore */
261 make_noncontiguous(ef, node->start_cluster, previous);
262 node->flags &= ~EXFAT_ATTRIB_CONTIGUOUS;
263 node->flags |= EXFAT_ATTRIB_DIRTY;
264 }
265 set_next_cluster(ef, IS_CONTIGUOUS(*node), previous, next);
266 previous = next;
267 allocated++;
268 }
269
270 set_next_cluster(ef, IS_CONTIGUOUS(*node), previous, EXFAT_CLUSTER_END);
271 return 0;
272}
273
274static int shrink_file(struct exfat* ef, struct exfat_node* node,
275 uint32_t current, uint32_t difference)
276{
277 cluster_t previous;
278 cluster_t next;
279
280 if (difference == 0)
281 exfat_bug("zero difference passed");
282 if (node->start_cluster == EXFAT_CLUSTER_FREE)
283 exfat_bug("unable to shrink empty file (%u clusters)", current);
284 if (current < difference)
285 exfat_bug("file underflow (%u < %u)", current, difference);
286
287 /* crop the file */
288 if (current > difference)
289 {
290 cluster_t last = exfat_advance_cluster(ef, node,
291 current - difference - 1);
292 if (CLUSTER_INVALID(last))
293 {
294 exfat_error("invalid cluster 0x%x while shrinking", last);
295 return -EIO;
296 }
297 previous = exfat_next_cluster(ef, node, last);
298 set_next_cluster(ef, IS_CONTIGUOUS(*node), last, EXFAT_CLUSTER_END);
299 }
300 else
301 {
302 previous = node->start_cluster;
303 node->start_cluster = EXFAT_CLUSTER_FREE;
304 }
305 node->fptr_index = 0;
306 node->fptr_cluster = node->start_cluster;
307
308 /* free remaining clusters */
309 while (difference--)
310 {
311 if (CLUSTER_INVALID(previous))
312 {
313 exfat_error("invalid cluster 0x%x while freeing after shrink",
314 previous);
315 return -EIO;
316 }
317 next = exfat_next_cluster(ef, node, previous);
318 set_next_cluster(ef, IS_CONTIGUOUS(*node), previous,
319 EXFAT_CLUSTER_FREE);
320 free_cluster(ef, previous);
321 previous = next;
322 }
323 return 0;
324}
325
326static void erase_raw(struct exfat* ef, size_t size, off64_t offset)
327{
328 exfat_pwrite(ef->dev, ef->zero_cluster, size, offset);
329}
330
331static int erase_range(struct exfat* ef, struct exfat_node* node,
332 uint64_t begin, uint64_t end)
333{
334 uint64_t cluster_boundary;
335 cluster_t cluster;
336
337 if (begin >= end)
338 return 0;
339
340 cluster_boundary = (begin | (CLUSTER_SIZE(*ef->sb) - 1)) + 1;
341 cluster = exfat_advance_cluster(ef, node,
342 begin / CLUSTER_SIZE(*ef->sb));
343 if (CLUSTER_INVALID(cluster))
344 {
345 exfat_error("invalid cluster 0x%x while erasing", cluster);
346 return -EIO;
347 }
348 /* erase from the beginning to the closest cluster boundary */
349 erase_raw(ef, MIN(cluster_boundary, end) - begin,
350 exfat_c2o(ef, cluster) + begin % CLUSTER_SIZE(*ef->sb));
351 /* erase whole clusters */
352 while (cluster_boundary < end)
353 {
354 cluster = exfat_next_cluster(ef, node, cluster);
355 /* the cluster cannot be invalid because we have just allocated it */
356 if (CLUSTER_INVALID(cluster))
357 exfat_bug("invalid cluster 0x%x after allocation", cluster);
358 erase_raw(ef, CLUSTER_SIZE(*ef->sb), exfat_c2o(ef, cluster));
359 cluster_boundary += CLUSTER_SIZE(*ef->sb);
360 }
361 return 0;
362}
363
364int exfat_truncate(struct exfat* ef, struct exfat_node* node, uint64_t size)
365{
366 uint32_t c1 = bytes2clusters(ef, node->size);
367 uint32_t c2 = bytes2clusters(ef, size);
368 int rc = 0;
369
370 if (node->references == 0 && node->parent)
371 exfat_bug("no references, node changes can be lost");
372
373 if (node->size == size)
374 return 0;
375
376 if (c1 < c2)
377 rc = grow_file(ef, node, c1, c2 - c1);
378 else if (c1 > c2)
379 rc = shrink_file(ef, node, c1, c1 - c2);
380
381 if (rc != 0)
382 return rc;
383
384 rc = erase_range(ef, node, node->size, size);
385 if (rc != 0)
386 return rc;
387
388 exfat_update_mtime(node);
389 node->size = size;
390 node->flags |= EXFAT_ATTRIB_DIRTY;
391 return 0;
392}
393
394uint32_t exfat_count_free_clusters(const struct exfat* ef)
395{
396 uint32_t free_clusters = 0;
397 uint32_t i;
398
399 for (i = 0; i < ef->cmap.size; i++)
400 if (BMAP_GET(ef->cmap.chunk, i) == 0)
401 free_clusters++;
402 return free_clusters;
403}
404
405static int find_used_clusters(const struct exfat* ef,
406 cluster_t* a, cluster_t* b)
407{
408 const cluster_t end = le32_to_cpu(ef->sb->cluster_count);
409
410 /* find first used cluster */
411 for (*a = *b + 1; *a < end; (*a)++)
412 if (BMAP_GET(ef->cmap.chunk, *a - EXFAT_FIRST_DATA_CLUSTER))
413 break;
414 if (*a >= end)
415 return 1;
416
417 /* find last contiguous used cluster */
418 for (*b = *a; *b < end; (*b)++)
419 if (BMAP_GET(ef->cmap.chunk, *b - EXFAT_FIRST_DATA_CLUSTER) == 0)
420 {
421 (*b)--;
422 break;
423 }
424
425 return 0;
426}
427
428int exfat_find_used_sectors(const struct exfat* ef, off64_t* a, off64_t* b)
429{
430 cluster_t ca, cb;
431
432 if (*a == 0 && *b == 0)
433 ca = cb = EXFAT_FIRST_DATA_CLUSTER - 1;
434 else
435 {
436 ca = s2c(ef, *a);
437 cb = s2c(ef, *b);
438 }
439 if (find_used_clusters(ef, &ca, &cb) != 0)
440 return 1;
441 if (*a != 0 || *b != 0)
442 *a = c2s(ef, ca);
443 *b = c2s(ef, cb) + (CLUSTER_SIZE(*ef->sb) - 1) / SECTOR_SIZE(*ef->sb);
444 return 0;
445}