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Linux 3.12.5
[linux/fpc-iii.git] / fs / fat / fatent.c
blob260705c58062cc425b8c656434883de98e1b9e2a
1 /*
2 * Copyright (C) 2004, OGAWA Hirofumi
3 * Released under GPL v2.
4 */
5
6 #include <linux/module.h>
7 #include <linux/fs.h>
8 #include <linux/msdos_fs.h>
9 #include <linux/blkdev.h>
10 #include "fat.h"
11
12 struct fatent_operations {
13 void (*ent_blocknr)(struct super_block *, int, int *, sector_t *);
14 void (*ent_set_ptr)(struct fat_entry *, int);
15 int (*ent_bread)(struct super_block *, struct fat_entry *,
16 int, sector_t);
17 int (*ent_get)(struct fat_entry *);
18 void (*ent_put)(struct fat_entry *, int);
19 int (*ent_next)(struct fat_entry *);
20 };
21
22 static DEFINE_SPINLOCK(fat12_entry_lock);
23
24 static void fat12_ent_blocknr(struct super_block *sb, int entry,
25 int *offset, sector_t *blocknr)
26 {
27 struct msdos_sb_info *sbi = MSDOS_SB(sb);
28 int bytes = entry + (entry >> 1);
29 WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
30 *offset = bytes & (sb->s_blocksize - 1);
31 *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
32 }
33
34 static void fat_ent_blocknr(struct super_block *sb, int entry,
35 int *offset, sector_t *blocknr)
36 {
37 struct msdos_sb_info *sbi = MSDOS_SB(sb);
38 int bytes = (entry << sbi->fatent_shift);
39 WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
40 *offset = bytes & (sb->s_blocksize - 1);
41 *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
42 }
43
44 static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
45 {
46 struct buffer_head **bhs = fatent->bhs;
47 if (fatent->nr_bhs == 1) {
48 WARN_ON(offset >= (bhs[0]->b_size - 1));
49 fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
50 fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
51 } else {
52 WARN_ON(offset != (bhs[0]->b_size - 1));
53 fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
54 fatent->u.ent12_p[1] = bhs[1]->b_data;
55 }
56 }
57
58 static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
59 {
60 WARN_ON(offset & (2 - 1));
61 fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
62 }
63
64 static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
65 {
66 WARN_ON(offset & (4 - 1));
67 fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
68 }
69
70 static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
71 int offset, sector_t blocknr)
72 {
73 struct buffer_head **bhs = fatent->bhs;
74
75 WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
76 fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
77
78 bhs[0] = sb_bread(sb, blocknr);
79 if (!bhs[0])
80 goto err;
81
82 if ((offset + 1) < sb->s_blocksize)
83 fatent->nr_bhs = 1;
84 else {
85 /* This entry is block boundary, it needs the next block */
86 blocknr++;
87 bhs[1] = sb_bread(sb, blocknr);
88 if (!bhs[1])
89 goto err_brelse;
90 fatent->nr_bhs = 2;
91 }
92 fat12_ent_set_ptr(fatent, offset);
93 return 0;
94
95 err_brelse:
96 brelse(bhs[0]);
97 err:
98 fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (llu)blocknr);
99 return -EIO;
100 }
101
102 static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
103 int offset, sector_t blocknr)
104 {
105 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
106
107 WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
108 fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
109 fatent->bhs[0] = sb_bread(sb, blocknr);
110 if (!fatent->bhs[0]) {
111 fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
112 (llu)blocknr);
113 return -EIO;
114 }
115 fatent->nr_bhs = 1;
116 ops->ent_set_ptr(fatent, offset);
117 return 0;
118 }
119
120 static int fat12_ent_get(struct fat_entry *fatent)
121 {
122 u8 **ent12_p = fatent->u.ent12_p;
123 int next;
124
125 spin_lock(&fat12_entry_lock);
126 if (fatent->entry & 1)
127 next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
128 else
129 next = (*ent12_p[1] << 8) | *ent12_p[0];
130 spin_unlock(&fat12_entry_lock);
131
132 next &= 0x0fff;
133 if (next >= BAD_FAT12)
134 next = FAT_ENT_EOF;
135 return next;
136 }
137
138 static int fat16_ent_get(struct fat_entry *fatent)
139 {
140 int next = le16_to_cpu(*fatent->u.ent16_p);
141 WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
142 if (next >= BAD_FAT16)
143 next = FAT_ENT_EOF;
144 return next;
145 }
146
147 static int fat32_ent_get(struct fat_entry *fatent)
148 {
149 int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
150 WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
151 if (next >= BAD_FAT32)
152 next = FAT_ENT_EOF;
153 return next;
154 }
155
156 static void fat12_ent_put(struct fat_entry *fatent, int new)
157 {
158 u8 **ent12_p = fatent->u.ent12_p;
159
160 if (new == FAT_ENT_EOF)
161 new = EOF_FAT12;
162
163 spin_lock(&fat12_entry_lock);
164 if (fatent->entry & 1) {
165 *ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
166 *ent12_p[1] = new >> 4;
167 } else {
168 *ent12_p[0] = new & 0xff;
169 *ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
170 }
171 spin_unlock(&fat12_entry_lock);
172
173 mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
174 if (fatent->nr_bhs == 2)
175 mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
176 }
177
178 static void fat16_ent_put(struct fat_entry *fatent, int new)
179 {
180 if (new == FAT_ENT_EOF)
181 new = EOF_FAT16;
182
183 *fatent->u.ent16_p = cpu_to_le16(new);
184 mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
185 }
186
187 static void fat32_ent_put(struct fat_entry *fatent, int new)
188 {
189 WARN_ON(new & 0xf0000000);
190 new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
191 *fatent->u.ent32_p = cpu_to_le32(new);
192 mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
193 }
194
195 static int fat12_ent_next(struct fat_entry *fatent)
196 {
197 u8 **ent12_p = fatent->u.ent12_p;
198 struct buffer_head **bhs = fatent->bhs;
199 u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
200
201 fatent->entry++;
202 if (fatent->nr_bhs == 1) {
203 WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data +
204 (bhs[0]->b_size - 2)));
205 WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data +
206 (bhs[0]->b_size - 1)));
207 if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
208 ent12_p[0] = nextp - 1;
209 ent12_p[1] = nextp;
210 return 1;
211 }
212 } else {
213 WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data +
214 (bhs[0]->b_size - 1)));
215 WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
216 ent12_p[0] = nextp - 1;
217 ent12_p[1] = nextp;
218 brelse(bhs[0]);
219 bhs[0] = bhs[1];
220 fatent->nr_bhs = 1;
221 return 1;
222 }
223 ent12_p[0] = NULL;
224 ent12_p[1] = NULL;
225 return 0;
226 }
227
228 static int fat16_ent_next(struct fat_entry *fatent)
229 {
230 const struct buffer_head *bh = fatent->bhs[0];
231 fatent->entry++;
232 if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
233 fatent->u.ent16_p++;
234 return 1;
235 }
236 fatent->u.ent16_p = NULL;
237 return 0;
238 }
239
240 static int fat32_ent_next(struct fat_entry *fatent)
241 {
242 const struct buffer_head *bh = fatent->bhs[0];
243 fatent->entry++;
244 if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
245 fatent->u.ent32_p++;
246 return 1;
247 }
248 fatent->u.ent32_p = NULL;
249 return 0;
250 }
251
252 static struct fatent_operations fat12_ops = {
253 .ent_blocknr = fat12_ent_blocknr,
254 .ent_set_ptr = fat12_ent_set_ptr,
255 .ent_bread = fat12_ent_bread,
256 .ent_get = fat12_ent_get,
257 .ent_put = fat12_ent_put,
258 .ent_next = fat12_ent_next,
259 };
260
261 static struct fatent_operations fat16_ops = {
262 .ent_blocknr = fat_ent_blocknr,
263 .ent_set_ptr = fat16_ent_set_ptr,
264 .ent_bread = fat_ent_bread,
265 .ent_get = fat16_ent_get,
266 .ent_put = fat16_ent_put,
267 .ent_next = fat16_ent_next,
268 };
269
270 static struct fatent_operations fat32_ops = {
271 .ent_blocknr = fat_ent_blocknr,
272 .ent_set_ptr = fat32_ent_set_ptr,
273 .ent_bread = fat_ent_bread,
274 .ent_get = fat32_ent_get,
275 .ent_put = fat32_ent_put,
276 .ent_next = fat32_ent_next,
277 };
278
279 static inline void lock_fat(struct msdos_sb_info *sbi)
280 {
281 mutex_lock(&sbi->fat_lock);
282 }
283
284 static inline void unlock_fat(struct msdos_sb_info *sbi)
285 {
286 mutex_unlock(&sbi->fat_lock);
287 }
288
289 void fat_ent_access_init(struct super_block *sb)
290 {
291 struct msdos_sb_info *sbi = MSDOS_SB(sb);
292
293 mutex_init(&sbi->fat_lock);
294
295 switch (sbi->fat_bits) {
296 case 32:
297 sbi->fatent_shift = 2;
298 sbi->fatent_ops = &fat32_ops;
299 break;
300 case 16:
301 sbi->fatent_shift = 1;
302 sbi->fatent_ops = &fat16_ops;
303 break;
304 case 12:
305 sbi->fatent_shift = -1;
306 sbi->fatent_ops = &fat12_ops;
307 break;
308 }
309 }
310
311 static void mark_fsinfo_dirty(struct super_block *sb)
312 {
313 struct msdos_sb_info *sbi = MSDOS_SB(sb);
314
315 if (sb->s_flags & MS_RDONLY || sbi->fat_bits != 32)
316 return;
317
318 __mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
319 }
320
321 static inline int fat_ent_update_ptr(struct super_block *sb,
322 struct fat_entry *fatent,
323 int offset, sector_t blocknr)
324 {
325 struct msdos_sb_info *sbi = MSDOS_SB(sb);
326 struct fatent_operations *ops = sbi->fatent_ops;
327 struct buffer_head **bhs = fatent->bhs;
328
329 /* Is this fatent's blocks including this entry? */
330 if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
331 return 0;
332 if (sbi->fat_bits == 12) {
333 if ((offset + 1) < sb->s_blocksize) {
334 /* This entry is on bhs[0]. */
335 if (fatent->nr_bhs == 2) {
336 brelse(bhs[1]);
337 fatent->nr_bhs = 1;
338 }
339 } else {
340 /* This entry needs the next block. */
341 if (fatent->nr_bhs != 2)
342 return 0;
343 if (bhs[1]->b_blocknr != (blocknr + 1))
344 return 0;
345 }
346 }
347 ops->ent_set_ptr(fatent, offset);
348 return 1;
349 }
350
351 int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
352 {
353 struct super_block *sb = inode->i_sb;
354 struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
355 struct fatent_operations *ops = sbi->fatent_ops;
356 int err, offset;
357 sector_t blocknr;
358
359 if (entry < FAT_START_ENT || sbi->max_cluster <= entry) {
360 fatent_brelse(fatent);
361 fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
362 return -EIO;
363 }
364
365 fatent_set_entry(fatent, entry);
366 ops->ent_blocknr(sb, entry, &offset, &blocknr);
367
368 if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
369 fatent_brelse(fatent);
370 err = ops->ent_bread(sb, fatent, offset, blocknr);
371 if (err)
372 return err;
373 }
374 return ops->ent_get(fatent);
375 }
376
377 /* FIXME: We can write the blocks as more big chunk. */
378 static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
379 int nr_bhs)
380 {
381 struct msdos_sb_info *sbi = MSDOS_SB(sb);
382 struct buffer_head *c_bh;
383 int err, n, copy;
384
385 err = 0;
386 for (copy = 1; copy < sbi->fats; copy++) {
387 sector_t backup_fat = sbi->fat_length * copy;
388
389 for (n = 0; n < nr_bhs; n++) {
390 c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
391 if (!c_bh) {
392 err = -ENOMEM;
393 goto error;
394 }
395 memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
396 set_buffer_uptodate(c_bh);
397 mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
398 if (sb->s_flags & MS_SYNCHRONOUS)
399 err = sync_dirty_buffer(c_bh);
400 brelse(c_bh);
401 if (err)
402 goto error;
403 }
404 }
405 error:
406 return err;
407 }
408
409 int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
410 int new, int wait)
411 {
412 struct super_block *sb = inode->i_sb;
413 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
414 int err;
415
416 ops->ent_put(fatent, new);
417 if (wait) {
418 err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
419 if (err)
420 return err;
421 }
422 return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
423 }
424
425 static inline int fat_ent_next(struct msdos_sb_info *sbi,
426 struct fat_entry *fatent)
427 {
428 if (sbi->fatent_ops->ent_next(fatent)) {
429 if (fatent->entry < sbi->max_cluster)
430 return 1;
431 }
432 return 0;
433 }
434
435 static inline int fat_ent_read_block(struct super_block *sb,
436 struct fat_entry *fatent)
437 {
438 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
439 sector_t blocknr;
440 int offset;
441
442 fatent_brelse(fatent);
443 ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
444 return ops->ent_bread(sb, fatent, offset, blocknr);
445 }
446
447 static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
448 struct fat_entry *fatent)
449 {
450 int n, i;
451
452 for (n = 0; n < fatent->nr_bhs; n++) {
453 for (i = 0; i < *nr_bhs; i++) {
454 if (fatent->bhs[n] == bhs[i])
455 break;
456 }
457 if (i == *nr_bhs) {
458 get_bh(fatent->bhs[n]);
459 bhs[i] = fatent->bhs[n];
460 (*nr_bhs)++;
461 }
462 }
463 }
464
465 int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
466 {
467 struct super_block *sb = inode->i_sb;
468 struct msdos_sb_info *sbi = MSDOS_SB(sb);
469 struct fatent_operations *ops = sbi->fatent_ops;
470 struct fat_entry fatent, prev_ent;
471 struct buffer_head *bhs[MAX_BUF_PER_PAGE];
472 int i, count, err, nr_bhs, idx_clus;
473
474 BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2)); /* fixed limit */
475
476 lock_fat(sbi);
477 if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
478 sbi->free_clusters < nr_cluster) {
479 unlock_fat(sbi);
480 return -ENOSPC;
481 }
482
483 err = nr_bhs = idx_clus = 0;
484 count = FAT_START_ENT;
485 fatent_init(&prev_ent);
486 fatent_init(&fatent);
487 fatent_set_entry(&fatent, sbi->prev_free + 1);
488 while (count < sbi->max_cluster) {
489 if (fatent.entry >= sbi->max_cluster)
490 fatent.entry = FAT_START_ENT;
491 fatent_set_entry(&fatent, fatent.entry);
492 err = fat_ent_read_block(sb, &fatent);
493 if (err)
494 goto out;
495
496 /* Find the free entries in a block */
497 do {
498 if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
499 int entry = fatent.entry;
500
501 /* make the cluster chain */
502 ops->ent_put(&fatent, FAT_ENT_EOF);
503 if (prev_ent.nr_bhs)
504 ops->ent_put(&prev_ent, entry);
505
506 fat_collect_bhs(bhs, &nr_bhs, &fatent);
507
508 sbi->prev_free = entry;
509 if (sbi->free_clusters != -1)
510 sbi->free_clusters--;
511
512 cluster[idx_clus] = entry;
513 idx_clus++;
514 if (idx_clus == nr_cluster)
515 goto out;
516
517 /*
518 * fat_collect_bhs() gets ref-count of bhs,
519 * so we can still use the prev_ent.
520 */
521 prev_ent = fatent;
522 }
523 count++;
524 if (count == sbi->max_cluster)
525 break;
526 } while (fat_ent_next(sbi, &fatent));
527 }
528
529 /* Couldn't allocate the free entries */
530 sbi->free_clusters = 0;
531 sbi->free_clus_valid = 1;
532 err = -ENOSPC;
533
534 out:
535 unlock_fat(sbi);
536 mark_fsinfo_dirty(sb);
537 fatent_brelse(&fatent);
538 if (!err) {
539 if (inode_needs_sync(inode))
540 err = fat_sync_bhs(bhs, nr_bhs);
541 if (!err)
542 err = fat_mirror_bhs(sb, bhs, nr_bhs);
543 }
544 for (i = 0; i < nr_bhs; i++)
545 brelse(bhs[i]);
546
547 if (err && idx_clus)
548 fat_free_clusters(inode, cluster[0]);
549
550 return err;
551 }
552
553 int fat_free_clusters(struct inode *inode, int cluster)
554 {
555 struct super_block *sb = inode->i_sb;
556 struct msdos_sb_info *sbi = MSDOS_SB(sb);
557 struct fatent_operations *ops = sbi->fatent_ops;
558 struct fat_entry fatent;
559 struct buffer_head *bhs[MAX_BUF_PER_PAGE];
560 int i, err, nr_bhs;
561 int first_cl = cluster, dirty_fsinfo = 0;
562
563 nr_bhs = 0;
564 fatent_init(&fatent);
565 lock_fat(sbi);
566 do {
567 cluster = fat_ent_read(inode, &fatent, cluster);
568 if (cluster < 0) {
569 err = cluster;
570 goto error;
571 } else if (cluster == FAT_ENT_FREE) {
572 fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
573 __func__);
574 err = -EIO;
575 goto error;
576 }
577
578 if (sbi->options.discard) {
579 /*
580 * Issue discard for the sectors we no longer
581 * care about, batching contiguous clusters
582 * into one request
583 */
584 if (cluster != fatent.entry + 1) {
585 int nr_clus = fatent.entry - first_cl + 1;
586
587 sb_issue_discard(sb,
588 fat_clus_to_blknr(sbi, first_cl),
589 nr_clus * sbi->sec_per_clus,
590 GFP_NOFS, 0);
591
592 first_cl = cluster;
593 }
594 }
595
596 ops->ent_put(&fatent, FAT_ENT_FREE);
597 if (sbi->free_clusters != -1) {
598 sbi->free_clusters++;
599 dirty_fsinfo = 1;
600 }
601
602 if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
603 if (sb->s_flags & MS_SYNCHRONOUS) {
604 err = fat_sync_bhs(bhs, nr_bhs);
605 if (err)
606 goto error;
607 }
608 err = fat_mirror_bhs(sb, bhs, nr_bhs);
609 if (err)
610 goto error;
611 for (i = 0; i < nr_bhs; i++)
612 brelse(bhs[i]);
613 nr_bhs = 0;
614 }
615 fat_collect_bhs(bhs, &nr_bhs, &fatent);
616 } while (cluster != FAT_ENT_EOF);
617
618 if (sb->s_flags & MS_SYNCHRONOUS) {
619 err = fat_sync_bhs(bhs, nr_bhs);
620 if (err)
621 goto error;
622 }
623 err = fat_mirror_bhs(sb, bhs, nr_bhs);
624 error:
625 fatent_brelse(&fatent);
626 for (i = 0; i < nr_bhs; i++)
627 brelse(bhs[i]);
628 unlock_fat(sbi);
629 if (dirty_fsinfo)
630 mark_fsinfo_dirty(sb);
631
632 return err;
633 }
634 EXPORT_SYMBOL_GPL(fat_free_clusters);
635
636 /* 128kb is the whole sectors for FAT12 and FAT16 */
637 #define FAT_READA_SIZE (128 * 1024)
638
639 static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
640 unsigned long reada_blocks)
641 {
642 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
643 sector_t blocknr;
644 int i, offset;
645
646 ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
647
648 for (i = 0; i < reada_blocks; i++)
649 sb_breadahead(sb, blocknr + i);
650 }
651
652 int fat_count_free_clusters(struct super_block *sb)
653 {
654 struct msdos_sb_info *sbi = MSDOS_SB(sb);
655 struct fatent_operations *ops = sbi->fatent_ops;
656 struct fat_entry fatent;
657 unsigned long reada_blocks, reada_mask, cur_block;
658 int err = 0, free;
659
660 lock_fat(sbi);
661 if (sbi->free_clusters != -1 && sbi->free_clus_valid)
662 goto out;
663
664 reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
665 reada_mask = reada_blocks - 1;
666 cur_block = 0;
667
668 free = 0;
669 fatent_init(&fatent);
670 fatent_set_entry(&fatent, FAT_START_ENT);
671 while (fatent.entry < sbi->max_cluster) {
672 /* readahead of fat blocks */
673 if ((cur_block & reada_mask) == 0) {
674 unsigned long rest = sbi->fat_length - cur_block;
675 fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
676 }
677 cur_block++;
678
679 err = fat_ent_read_block(sb, &fatent);
680 if (err)
681 goto out;
682
683 do {
684 if (ops->ent_get(&fatent) == FAT_ENT_FREE)
685 free++;
686 } while (fat_ent_next(sbi, &fatent));
687 }
688 sbi->free_clusters = free;
689 sbi->free_clus_valid = 1;
690 mark_fsinfo_dirty(sb);
691 fatent_brelse(&fatent);
692 out:
693 unlock_fat(sbi);
694 return err;
695 }
Linux with added FPC-III support