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TOMOYO Linux Cross Reference
Linux/fs/fat/fatent.c

Version: ~ [ linux-5.4-rc7 ] ~ [ linux-5.3.11 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.84 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.154 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.201 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.201 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.77 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * Copyright (C) 2004, OGAWA Hirofumi
  3  * Released under GPL v2.
  4  */
  5 
  6 #include <linux/blkdev.h>
  7 #include "fat.h"
  8 
  9 struct 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 
 19 static DEFINE_SPINLOCK(fat12_entry_lock);
 20 
 21 static 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 
 31 static 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 
 41 static 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 
 55 static 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 
 61 static 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 
 67 static 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 
 92 err_brelse:
 93         brelse(bhs[0]);
 94 err:
 95         fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (llu)blocknr);
 96         return -EIO;
 97 }
 98 
 99 static 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 
117 static 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 
135 static 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 
144 static 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 
153 static 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 
175 static 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 
184 static 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 
192 static 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 
225 static 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 
237 static 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 
249 static 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 
258 static 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 
267 static 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 
276 static inline void lock_fat(struct msdos_sb_info *sbi)
277 {
278         mutex_lock(&sbi->fat_lock);
279 }
280 
281 static inline void unlock_fat(struct msdos_sb_info *sbi)
282 {
283         mutex_unlock(&sbi->fat_lock);
284 }
285 
286 void 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 
308 static 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 
318 static 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 
348 int 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. */
375 static 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         }
402 error:
403         return err;
404 }
405 
406 int 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 
422 static 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 
432 static 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 
444 static 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 
462 int 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 
531 out:
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 
550 int 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);
621 error:
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 }
631 EXPORT_SYMBOL_GPL(fat_free_clusters);
632 
633 /* 128kb is the whole sectors for FAT12 and FAT16 */
634 #define FAT_READA_SIZE          (128 * 1024)
635 
636 static 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 
649 int 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);
689 out:
690         unlock_fat(sbi);
691         return err;
692 }
693 

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