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