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OMAPDSS: VENC: fix NULL pointer dereference in DSS2 VENC sysfs debug attr on OMAP4
[zen-stable.git] / fs / fat / fatent.c
blob2e81ac0df7e2eae4b30ad9b2e1db360798f92b2c
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 if (new == FAT_ENT_EOF)
190 new = EOF_FAT32;
191
192 WARN_ON(new & 0xf0000000);
193 new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
194 *fatent->u.ent32_p = cpu_to_le32(new);
195 mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
196 }
197
198 static int fat12_ent_next(struct fat_entry *fatent)
199 {
200 u8 **ent12_p = fatent->u.ent12_p;
201 struct buffer_head **bhs = fatent->bhs;
202 u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
203
204 fatent->entry++;
205 if (fatent->nr_bhs == 1) {
206 WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 2)));
207 WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1)));
208 if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
209 ent12_p[0] = nextp - 1;
210 ent12_p[1] = nextp;
211 return 1;
212 }
213 } else {
214 WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data + (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 inline int fat_ent_update_ptr(struct super_block *sb,
312 struct fat_entry *fatent,
313 int offset, sector_t blocknr)
314 {
315 struct msdos_sb_info *sbi = MSDOS_SB(sb);
316 struct fatent_operations *ops = sbi->fatent_ops;
317 struct buffer_head **bhs = fatent->bhs;
318
319 /* Is this fatent's blocks including this entry? */
320 if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
321 return 0;
322 if (sbi->fat_bits == 12) {
323 if ((offset + 1) < sb->s_blocksize) {
324 /* This entry is on bhs[0]. */
325 if (fatent->nr_bhs == 2) {
326 brelse(bhs[1]);
327 fatent->nr_bhs = 1;
328 }
329 } else {
330 /* This entry needs the next block. */
331 if (fatent->nr_bhs != 2)
332 return 0;
333 if (bhs[1]->b_blocknr != (blocknr + 1))
334 return 0;
335 }
336 }
337 ops->ent_set_ptr(fatent, offset);
338 return 1;
339 }
340
341 int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
342 {
343 struct super_block *sb = inode->i_sb;
344 struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
345 struct fatent_operations *ops = sbi->fatent_ops;
346 int err, offset;
347 sector_t blocknr;
348
349 if (entry < FAT_START_ENT || sbi->max_cluster <= entry) {
350 fatent_brelse(fatent);
351 fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
352 return -EIO;
353 }
354
355 fatent_set_entry(fatent, entry);
356 ops->ent_blocknr(sb, entry, &offset, &blocknr);
357
358 if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
359 fatent_brelse(fatent);
360 err = ops->ent_bread(sb, fatent, offset, blocknr);
361 if (err)
362 return err;
363 }
364 return ops->ent_get(fatent);
365 }
366
367 /* FIXME: We can write the blocks as more big chunk. */
368 static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
369 int nr_bhs)
370 {
371 struct msdos_sb_info *sbi = MSDOS_SB(sb);
372 struct buffer_head *c_bh;
373 int err, n, copy;
374
375 err = 0;
376 for (copy = 1; copy < sbi->fats; copy++) {
377 sector_t backup_fat = sbi->fat_length * copy;
378
379 for (n = 0; n < nr_bhs; n++) {
380 c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
381 if (!c_bh) {
382 err = -ENOMEM;
383 goto error;
384 }
385 memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
386 set_buffer_uptodate(c_bh);
387 mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
388 if (sb->s_flags & MS_SYNCHRONOUS)
389 err = sync_dirty_buffer(c_bh);
390 brelse(c_bh);
391 if (err)
392 goto error;
393 }
394 }
395 error:
396 return err;
397 }
398
399 int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
400 int new, int wait)
401 {
402 struct super_block *sb = inode->i_sb;
403 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
404 int err;
405
406 ops->ent_put(fatent, new);
407 if (wait) {
408 err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
409 if (err)
410 return err;
411 }
412 return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
413 }
414
415 static inline int fat_ent_next(struct msdos_sb_info *sbi,
416 struct fat_entry *fatent)
417 {
418 if (sbi->fatent_ops->ent_next(fatent)) {
419 if (fatent->entry < sbi->max_cluster)
420 return 1;
421 }
422 return 0;
423 }
424
425 static inline int fat_ent_read_block(struct super_block *sb,
426 struct fat_entry *fatent)
427 {
428 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
429 sector_t blocknr;
430 int offset;
431
432 fatent_brelse(fatent);
433 ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
434 return ops->ent_bread(sb, fatent, offset, blocknr);
435 }
436
437 static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
438 struct fat_entry *fatent)
439 {
440 int n, i;
441
442 for (n = 0; n < fatent->nr_bhs; n++) {
443 for (i = 0; i < *nr_bhs; i++) {
444 if (fatent->bhs[n] == bhs[i])
445 break;
446 }
447 if (i == *nr_bhs) {
448 get_bh(fatent->bhs[n]);
449 bhs[i] = fatent->bhs[n];
450 (*nr_bhs)++;
451 }
452 }
453 }
454
455 int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
456 {
457 struct super_block *sb = inode->i_sb;
458 struct msdos_sb_info *sbi = MSDOS_SB(sb);
459 struct fatent_operations *ops = sbi->fatent_ops;
460 struct fat_entry fatent, prev_ent;
461 struct buffer_head *bhs[MAX_BUF_PER_PAGE];
462 int i, count, err, nr_bhs, idx_clus;
463
464 BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2)); /* fixed limit */
465
466 lock_fat(sbi);
467 if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
468 sbi->free_clusters < nr_cluster) {
469 unlock_fat(sbi);
470 return -ENOSPC;
471 }
472
473 err = nr_bhs = idx_clus = 0;
474 count = FAT_START_ENT;
475 fatent_init(&prev_ent);
476 fatent_init(&fatent);
477 fatent_set_entry(&fatent, sbi->prev_free + 1);
478 while (count < sbi->max_cluster) {
479 if (fatent.entry >= sbi->max_cluster)
480 fatent.entry = FAT_START_ENT;
481 fatent_set_entry(&fatent, fatent.entry);
482 err = fat_ent_read_block(sb, &fatent);
483 if (err)
484 goto out;
485
486 /* Find the free entries in a block */
487 do {
488 if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
489 int entry = fatent.entry;
490
491 /* make the cluster chain */
492 ops->ent_put(&fatent, FAT_ENT_EOF);
493 if (prev_ent.nr_bhs)
494 ops->ent_put(&prev_ent, entry);
495
496 fat_collect_bhs(bhs, &nr_bhs, &fatent);
497
498 sbi->prev_free = entry;
499 if (sbi->free_clusters != -1)
500 sbi->free_clusters--;
501 sb->s_dirt = 1;
502
503 cluster[idx_clus] = entry;
504 idx_clus++;
505 if (idx_clus == nr_cluster)
506 goto out;
507
508 /*
509 * fat_collect_bhs() gets ref-count of bhs,
510 * so we can still use the prev_ent.
511 */
512 prev_ent = fatent;
513 }
514 count++;
515 if (count == sbi->max_cluster)
516 break;
517 } while (fat_ent_next(sbi, &fatent));
518 }
519
520 /* Couldn't allocate the free entries */
521 sbi->free_clusters = 0;
522 sbi->free_clus_valid = 1;
523 sb->s_dirt = 1;
524 err = -ENOSPC;
525
526 out:
527 unlock_fat(sbi);
528 fatent_brelse(&fatent);
529 if (!err) {
530 if (inode_needs_sync(inode))
531 err = fat_sync_bhs(bhs, nr_bhs);
532 if (!err)
533 err = fat_mirror_bhs(sb, bhs, nr_bhs);
534 }
535 for (i = 0; i < nr_bhs; i++)
536 brelse(bhs[i]);
537
538 if (err && idx_clus)
539 fat_free_clusters(inode, cluster[0]);
540
541 return err;
542 }
543
544 int fat_free_clusters(struct inode *inode, int cluster)
545 {
546 struct super_block *sb = inode->i_sb;
547 struct msdos_sb_info *sbi = MSDOS_SB(sb);
548 struct fatent_operations *ops = sbi->fatent_ops;
549 struct fat_entry fatent;
550 struct buffer_head *bhs[MAX_BUF_PER_PAGE];
551 int i, err, nr_bhs;
552 int first_cl = cluster;
553
554 nr_bhs = 0;
555 fatent_init(&fatent);
556 lock_fat(sbi);
557 do {
558 cluster = fat_ent_read(inode, &fatent, cluster);
559 if (cluster < 0) {
560 err = cluster;
561 goto error;
562 } else if (cluster == FAT_ENT_FREE) {
563 fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
564 __func__);
565 err = -EIO;
566 goto error;
567 }
568
569 if (sbi->options.discard) {
570 /*
571 * Issue discard for the sectors we no longer
572 * care about, batching contiguous clusters
573 * into one request
574 */
575 if (cluster != fatent.entry + 1) {
576 int nr_clus = fatent.entry - first_cl + 1;
577
578 sb_issue_discard(sb,
579 fat_clus_to_blknr(sbi, first_cl),
580 nr_clus * sbi->sec_per_clus,
581 GFP_NOFS, 0);
582
583 first_cl = cluster;
584 }
585 }
586
587 ops->ent_put(&fatent, FAT_ENT_FREE);
588 if (sbi->free_clusters != -1) {
589 sbi->free_clusters++;
590 sb->s_dirt = 1;
591 }
592
593 if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
594 if (sb->s_flags & MS_SYNCHRONOUS) {
595 err = fat_sync_bhs(bhs, nr_bhs);
596 if (err)
597 goto error;
598 }
599 err = fat_mirror_bhs(sb, bhs, nr_bhs);
600 if (err)
601 goto error;
602 for (i = 0; i < nr_bhs; i++)
603 brelse(bhs[i]);
604 nr_bhs = 0;
605 }
606 fat_collect_bhs(bhs, &nr_bhs, &fatent);
607 } while (cluster != FAT_ENT_EOF);
608
609 if (sb->s_flags & MS_SYNCHRONOUS) {
610 err = fat_sync_bhs(bhs, nr_bhs);
611 if (err)
612 goto error;
613 }
614 err = fat_mirror_bhs(sb, bhs, nr_bhs);
615 error:
616 fatent_brelse(&fatent);
617 for (i = 0; i < nr_bhs; i++)
618 brelse(bhs[i]);
619 unlock_fat(sbi);
620
621 return err;
622 }
623
624 EXPORT_SYMBOL_GPL(fat_free_clusters);
625
626 /* 128kb is the whole sectors for FAT12 and FAT16 */
627 #define FAT_READA_SIZE (128 * 1024)
628
629 static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
630 unsigned long reada_blocks)
631 {
632 struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
633 sector_t blocknr;
634 int i, offset;
635
636 ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
637
638 for (i = 0; i < reada_blocks; i++)
639 sb_breadahead(sb, blocknr + i);
640 }
641
642 int fat_count_free_clusters(struct super_block *sb)
643 {
644 struct msdos_sb_info *sbi = MSDOS_SB(sb);
645 struct fatent_operations *ops = sbi->fatent_ops;
646 struct fat_entry fatent;
647 unsigned long reada_blocks, reada_mask, cur_block;
648 int err = 0, free;
649
650 lock_fat(sbi);
651 if (sbi->free_clusters != -1 && sbi->free_clus_valid)
652 goto out;
653
654 reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
655 reada_mask = reada_blocks - 1;
656 cur_block = 0;
657
658 free = 0;
659 fatent_init(&fatent);
660 fatent_set_entry(&fatent, FAT_START_ENT);
661 while (fatent.entry < sbi->max_cluster) {
662 /* readahead of fat blocks */
663 if ((cur_block & reada_mask) == 0) {
664 unsigned long rest = sbi->fat_length - cur_block;
665 fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
666 }
667 cur_block++;
668
669 err = fat_ent_read_block(sb, &fatent);
670 if (err)
671 goto out;
672
673 do {
674 if (ops->ent_get(&fatent) == FAT_ENT_FREE)
675 free++;
676 } while (fat_ent_next(sbi, &fatent));
677 }
678 sbi->free_clusters = free;
679 sbi->free_clus_valid = 1;
680 sb->s_dirt = 1;
681 fatent_brelse(&fatent);
682 out:
683 unlock_fat(sbi);
684 return err;
685 }