Merge branch 'akpm' (patches from Andrew)
[platform/kernel/linux-rpi.git] / fs / fat / fatent.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2004, OGAWA Hirofumi
4  */
5
6 #include <linux/blkdev.h>
7 #include <linux/sched/signal.h>
8 #include "fat.h"
9
10 struct fatent_operations {
11         void (*ent_blocknr)(struct super_block *, int, int *, sector_t *);
12         void (*ent_set_ptr)(struct fat_entry *, int);
13         int (*ent_bread)(struct super_block *, struct fat_entry *,
14                          int, sector_t);
15         int (*ent_get)(struct fat_entry *);
16         void (*ent_put)(struct fat_entry *, int);
17         int (*ent_next)(struct fat_entry *);
18 };
19
20 static DEFINE_SPINLOCK(fat12_entry_lock);
21
22 static void fat12_ent_blocknr(struct super_block *sb, int entry,
23                               int *offset, sector_t *blocknr)
24 {
25         struct msdos_sb_info *sbi = MSDOS_SB(sb);
26         int bytes = entry + (entry >> 1);
27         WARN_ON(!fat_valid_entry(sbi, entry));
28         *offset = bytes & (sb->s_blocksize - 1);
29         *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
30 }
31
32 static void fat_ent_blocknr(struct super_block *sb, int entry,
33                             int *offset, sector_t *blocknr)
34 {
35         struct msdos_sb_info *sbi = MSDOS_SB(sb);
36         int bytes = (entry << sbi->fatent_shift);
37         WARN_ON(!fat_valid_entry(sbi, entry));
38         *offset = bytes & (sb->s_blocksize - 1);
39         *blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
40 }
41
42 static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
43 {
44         struct buffer_head **bhs = fatent->bhs;
45         if (fatent->nr_bhs == 1) {
46                 WARN_ON(offset >= (bhs[0]->b_size - 1));
47                 fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
48                 fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
49         } else {
50                 WARN_ON(offset != (bhs[0]->b_size - 1));
51                 fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
52                 fatent->u.ent12_p[1] = bhs[1]->b_data;
53         }
54 }
55
56 static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
57 {
58         WARN_ON(offset & (2 - 1));
59         fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
60 }
61
62 static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
63 {
64         WARN_ON(offset & (4 - 1));
65         fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
66 }
67
68 static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
69                            int offset, sector_t blocknr)
70 {
71         struct buffer_head **bhs = fatent->bhs;
72
73         WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
74         fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
75
76         bhs[0] = sb_bread(sb, blocknr);
77         if (!bhs[0])
78                 goto err;
79
80         if ((offset + 1) < sb->s_blocksize)
81                 fatent->nr_bhs = 1;
82         else {
83                 /* This entry is block boundary, it needs the next block */
84                 blocknr++;
85                 bhs[1] = sb_bread(sb, blocknr);
86                 if (!bhs[1])
87                         goto err_brelse;
88                 fatent->nr_bhs = 2;
89         }
90         fat12_ent_set_ptr(fatent, offset);
91         return 0;
92
93 err_brelse:
94         brelse(bhs[0]);
95 err:
96         fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (llu)blocknr);
97         return -EIO;
98 }
99
100 static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
101                          int offset, sector_t blocknr)
102 {
103         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
104
105         WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
106         fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
107         fatent->bhs[0] = sb_bread(sb, blocknr);
108         if (!fatent->bhs[0]) {
109                 fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
110                        (llu)blocknr);
111                 return -EIO;
112         }
113         fatent->nr_bhs = 1;
114         ops->ent_set_ptr(fatent, offset);
115         return 0;
116 }
117
118 static int fat12_ent_get(struct fat_entry *fatent)
119 {
120         u8 **ent12_p = fatent->u.ent12_p;
121         int next;
122
123         spin_lock(&fat12_entry_lock);
124         if (fatent->entry & 1)
125                 next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
126         else
127                 next = (*ent12_p[1] << 8) | *ent12_p[0];
128         spin_unlock(&fat12_entry_lock);
129
130         next &= 0x0fff;
131         if (next >= BAD_FAT12)
132                 next = FAT_ENT_EOF;
133         return next;
134 }
135
136 static int fat16_ent_get(struct fat_entry *fatent)
137 {
138         int next = le16_to_cpu(*fatent->u.ent16_p);
139         WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
140         if (next >= BAD_FAT16)
141                 next = FAT_ENT_EOF;
142         return next;
143 }
144
145 static int fat32_ent_get(struct fat_entry *fatent)
146 {
147         int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
148         WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
149         if (next >= BAD_FAT32)
150                 next = FAT_ENT_EOF;
151         return next;
152 }
153
154 static void fat12_ent_put(struct fat_entry *fatent, int new)
155 {
156         u8 **ent12_p = fatent->u.ent12_p;
157
158         if (new == FAT_ENT_EOF)
159                 new = EOF_FAT12;
160
161         spin_lock(&fat12_entry_lock);
162         if (fatent->entry & 1) {
163                 *ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
164                 *ent12_p[1] = new >> 4;
165         } else {
166                 *ent12_p[0] = new & 0xff;
167                 *ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
168         }
169         spin_unlock(&fat12_entry_lock);
170
171         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
172         if (fatent->nr_bhs == 2)
173                 mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
174 }
175
176 static void fat16_ent_put(struct fat_entry *fatent, int new)
177 {
178         if (new == FAT_ENT_EOF)
179                 new = EOF_FAT16;
180
181         *fatent->u.ent16_p = cpu_to_le16(new);
182         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
183 }
184
185 static void fat32_ent_put(struct fat_entry *fatent, int new)
186 {
187         WARN_ON(new & 0xf0000000);
188         new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
189         *fatent->u.ent32_p = cpu_to_le32(new);
190         mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
191 }
192
193 static int fat12_ent_next(struct fat_entry *fatent)
194 {
195         u8 **ent12_p = fatent->u.ent12_p;
196         struct buffer_head **bhs = fatent->bhs;
197         u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
198
199         fatent->entry++;
200         if (fatent->nr_bhs == 1) {
201                 WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data +
202                                                         (bhs[0]->b_size - 2)));
203                 WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data +
204                                                         (bhs[0]->b_size - 1)));
205                 if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
206                         ent12_p[0] = nextp - 1;
207                         ent12_p[1] = nextp;
208                         return 1;
209                 }
210         } else {
211                 WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data +
212                                                         (bhs[0]->b_size - 1)));
213                 WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
214                 ent12_p[0] = nextp - 1;
215                 ent12_p[1] = nextp;
216                 brelse(bhs[0]);
217                 bhs[0] = bhs[1];
218                 fatent->nr_bhs = 1;
219                 return 1;
220         }
221         ent12_p[0] = NULL;
222         ent12_p[1] = NULL;
223         return 0;
224 }
225
226 static int fat16_ent_next(struct fat_entry *fatent)
227 {
228         const struct buffer_head *bh = fatent->bhs[0];
229         fatent->entry++;
230         if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
231                 fatent->u.ent16_p++;
232                 return 1;
233         }
234         fatent->u.ent16_p = NULL;
235         return 0;
236 }
237
238 static int fat32_ent_next(struct fat_entry *fatent)
239 {
240         const struct buffer_head *bh = fatent->bhs[0];
241         fatent->entry++;
242         if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
243                 fatent->u.ent32_p++;
244                 return 1;
245         }
246         fatent->u.ent32_p = NULL;
247         return 0;
248 }
249
250 static const struct fatent_operations fat12_ops = {
251         .ent_blocknr    = fat12_ent_blocknr,
252         .ent_set_ptr    = fat12_ent_set_ptr,
253         .ent_bread      = fat12_ent_bread,
254         .ent_get        = fat12_ent_get,
255         .ent_put        = fat12_ent_put,
256         .ent_next       = fat12_ent_next,
257 };
258
259 static const struct fatent_operations fat16_ops = {
260         .ent_blocknr    = fat_ent_blocknr,
261         .ent_set_ptr    = fat16_ent_set_ptr,
262         .ent_bread      = fat_ent_bread,
263         .ent_get        = fat16_ent_get,
264         .ent_put        = fat16_ent_put,
265         .ent_next       = fat16_ent_next,
266 };
267
268 static const struct fatent_operations fat32_ops = {
269         .ent_blocknr    = fat_ent_blocknr,
270         .ent_set_ptr    = fat32_ent_set_ptr,
271         .ent_bread      = fat_ent_bread,
272         .ent_get        = fat32_ent_get,
273         .ent_put        = fat32_ent_put,
274         .ent_next       = fat32_ent_next,
275 };
276
277 static inline void lock_fat(struct msdos_sb_info *sbi)
278 {
279         mutex_lock(&sbi->fat_lock);
280 }
281
282 static inline void unlock_fat(struct msdos_sb_info *sbi)
283 {
284         mutex_unlock(&sbi->fat_lock);
285 }
286
287 void fat_ent_access_init(struct super_block *sb)
288 {
289         struct msdos_sb_info *sbi = MSDOS_SB(sb);
290
291         mutex_init(&sbi->fat_lock);
292
293         if (is_fat32(sbi)) {
294                 sbi->fatent_shift = 2;
295                 sbi->fatent_ops = &fat32_ops;
296         } else if (is_fat16(sbi)) {
297                 sbi->fatent_shift = 1;
298                 sbi->fatent_ops = &fat16_ops;
299         } else if (is_fat12(sbi)) {
300                 sbi->fatent_shift = -1;
301                 sbi->fatent_ops = &fat12_ops;
302         } else {
303                 fat_fs_error(sb, "invalid FAT variant, %u bits", sbi->fat_bits);
304         }
305 }
306
307 static void mark_fsinfo_dirty(struct super_block *sb)
308 {
309         struct msdos_sb_info *sbi = MSDOS_SB(sb);
310
311         if (sb_rdonly(sb) || !is_fat32(sbi))
312                 return;
313
314         __mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
315 }
316
317 static inline int fat_ent_update_ptr(struct super_block *sb,
318                                      struct fat_entry *fatent,
319                                      int offset, sector_t blocknr)
320 {
321         struct msdos_sb_info *sbi = MSDOS_SB(sb);
322         const struct fatent_operations *ops = sbi->fatent_ops;
323         struct buffer_head **bhs = fatent->bhs;
324
325         /* Is this fatent's blocks including this entry? */
326         if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
327                 return 0;
328         if (is_fat12(sbi)) {
329                 if ((offset + 1) < sb->s_blocksize) {
330                         /* This entry is on bhs[0]. */
331                         if (fatent->nr_bhs == 2) {
332                                 brelse(bhs[1]);
333                                 fatent->nr_bhs = 1;
334                         }
335                 } else {
336                         /* This entry needs the next block. */
337                         if (fatent->nr_bhs != 2)
338                                 return 0;
339                         if (bhs[1]->b_blocknr != (blocknr + 1))
340                                 return 0;
341                 }
342         }
343         ops->ent_set_ptr(fatent, offset);
344         return 1;
345 }
346
347 int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
348 {
349         struct super_block *sb = inode->i_sb;
350         struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
351         const struct fatent_operations *ops = sbi->fatent_ops;
352         int err, offset;
353         sector_t blocknr;
354
355         if (!fat_valid_entry(sbi, entry)) {
356                 fatent_brelse(fatent);
357                 fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
358                 return -EIO;
359         }
360
361         fatent_set_entry(fatent, entry);
362         ops->ent_blocknr(sb, entry, &offset, &blocknr);
363
364         if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
365                 fatent_brelse(fatent);
366                 err = ops->ent_bread(sb, fatent, offset, blocknr);
367                 if (err)
368                         return err;
369         }
370         return ops->ent_get(fatent);
371 }
372
373 /* FIXME: We can write the blocks as more big chunk. */
374 static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
375                           int nr_bhs)
376 {
377         struct msdos_sb_info *sbi = MSDOS_SB(sb);
378         struct buffer_head *c_bh;
379         int err, n, copy;
380
381         err = 0;
382         for (copy = 1; copy < sbi->fats; copy++) {
383                 sector_t backup_fat = sbi->fat_length * copy;
384
385                 for (n = 0; n < nr_bhs; n++) {
386                         c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
387                         if (!c_bh) {
388                                 err = -ENOMEM;
389                                 goto error;
390                         }
391                         /* Avoid race with userspace read via bdev */
392                         lock_buffer(c_bh);
393                         memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
394                         set_buffer_uptodate(c_bh);
395                         unlock_buffer(c_bh);
396                         mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
397                         if (sb->s_flags & SB_SYNCHRONOUS)
398                                 err = sync_dirty_buffer(c_bh);
399                         brelse(c_bh);
400                         if (err)
401                                 goto error;
402                 }
403         }
404 error:
405         return err;
406 }
407
408 int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
409                   int new, int wait)
410 {
411         struct super_block *sb = inode->i_sb;
412         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
413         int err;
414
415         ops->ent_put(fatent, new);
416         if (wait) {
417                 err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
418                 if (err)
419                         return err;
420         }
421         return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
422 }
423
424 static inline int fat_ent_next(struct msdos_sb_info *sbi,
425                                struct fat_entry *fatent)
426 {
427         if (sbi->fatent_ops->ent_next(fatent)) {
428                 if (fatent->entry < sbi->max_cluster)
429                         return 1;
430         }
431         return 0;
432 }
433
434 static inline int fat_ent_read_block(struct super_block *sb,
435                                      struct fat_entry *fatent)
436 {
437         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
438         sector_t blocknr;
439         int offset;
440
441         fatent_brelse(fatent);
442         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
443         return ops->ent_bread(sb, fatent, offset, blocknr);
444 }
445
446 static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
447                             struct fat_entry *fatent)
448 {
449         int n, i;
450
451         for (n = 0; n < fatent->nr_bhs; n++) {
452                 for (i = 0; i < *nr_bhs; i++) {
453                         if (fatent->bhs[n] == bhs[i])
454                                 break;
455                 }
456                 if (i == *nr_bhs) {
457                         get_bh(fatent->bhs[n]);
458                         bhs[i] = fatent->bhs[n];
459                         (*nr_bhs)++;
460                 }
461         }
462 }
463
464 int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
465 {
466         struct super_block *sb = inode->i_sb;
467         struct msdos_sb_info *sbi = MSDOS_SB(sb);
468         const struct fatent_operations *ops = sbi->fatent_ops;
469         struct fat_entry fatent, prev_ent;
470         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
471         int i, count, err, nr_bhs, idx_clus;
472
473         BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));    /* fixed limit */
474
475         lock_fat(sbi);
476         if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
477             sbi->free_clusters < nr_cluster) {
478                 unlock_fat(sbi);
479                 return -ENOSPC;
480         }
481
482         err = nr_bhs = idx_clus = 0;
483         count = FAT_START_ENT;
484         fatent_init(&prev_ent);
485         fatent_init(&fatent);
486         fatent_set_entry(&fatent, sbi->prev_free + 1);
487         while (count < sbi->max_cluster) {
488                 if (fatent.entry >= sbi->max_cluster)
489                         fatent.entry = FAT_START_ENT;
490                 fatent_set_entry(&fatent, fatent.entry);
491                 err = fat_ent_read_block(sb, &fatent);
492                 if (err)
493                         goto out;
494
495                 /* Find the free entries in a block */
496                 do {
497                         if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
498                                 int entry = fatent.entry;
499
500                                 /* make the cluster chain */
501                                 ops->ent_put(&fatent, FAT_ENT_EOF);
502                                 if (prev_ent.nr_bhs)
503                                         ops->ent_put(&prev_ent, entry);
504
505                                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
506
507                                 sbi->prev_free = entry;
508                                 if (sbi->free_clusters != -1)
509                                         sbi->free_clusters--;
510
511                                 cluster[idx_clus] = entry;
512                                 idx_clus++;
513                                 if (idx_clus == nr_cluster)
514                                         goto out;
515
516                                 /*
517                                  * fat_collect_bhs() gets ref-count of bhs,
518                                  * so we can still use the prev_ent.
519                                  */
520                                 prev_ent = fatent;
521                         }
522                         count++;
523                         if (count == sbi->max_cluster)
524                                 break;
525                 } while (fat_ent_next(sbi, &fatent));
526         }
527
528         /* Couldn't allocate the free entries */
529         sbi->free_clusters = 0;
530         sbi->free_clus_valid = 1;
531         err = -ENOSPC;
532
533 out:
534         unlock_fat(sbi);
535         mark_fsinfo_dirty(sb);
536         fatent_brelse(&fatent);
537         if (!err) {
538                 if (inode_needs_sync(inode))
539                         err = fat_sync_bhs(bhs, nr_bhs);
540                 if (!err)
541                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
542         }
543         for (i = 0; i < nr_bhs; i++)
544                 brelse(bhs[i]);
545
546         if (err && idx_clus)
547                 fat_free_clusters(inode, cluster[0]);
548
549         return err;
550 }
551
552 int fat_free_clusters(struct inode *inode, int cluster)
553 {
554         struct super_block *sb = inode->i_sb;
555         struct msdos_sb_info *sbi = MSDOS_SB(sb);
556         const struct fatent_operations *ops = sbi->fatent_ops;
557         struct fat_entry fatent;
558         struct buffer_head *bhs[MAX_BUF_PER_PAGE];
559         int i, err, nr_bhs;
560         int first_cl = cluster, dirty_fsinfo = 0;
561
562         nr_bhs = 0;
563         fatent_init(&fatent);
564         lock_fat(sbi);
565         do {
566                 cluster = fat_ent_read(inode, &fatent, cluster);
567                 if (cluster < 0) {
568                         err = cluster;
569                         goto error;
570                 } else if (cluster == FAT_ENT_FREE) {
571                         fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
572                                      __func__);
573                         err = -EIO;
574                         goto error;
575                 }
576
577                 if (sbi->options.discard) {
578                         /*
579                          * Issue discard for the sectors we no longer
580                          * care about, batching contiguous clusters
581                          * into one request
582                          */
583                         if (cluster != fatent.entry + 1) {
584                                 int nr_clus = fatent.entry - first_cl + 1;
585
586                                 sb_issue_discard(sb,
587                                         fat_clus_to_blknr(sbi, first_cl),
588                                         nr_clus * sbi->sec_per_clus,
589                                         GFP_NOFS, 0);
590
591                                 first_cl = cluster;
592                         }
593                 }
594
595                 ops->ent_put(&fatent, FAT_ENT_FREE);
596                 if (sbi->free_clusters != -1) {
597                         sbi->free_clusters++;
598                         dirty_fsinfo = 1;
599                 }
600
601                 if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
602                         if (sb->s_flags & SB_SYNCHRONOUS) {
603                                 err = fat_sync_bhs(bhs, nr_bhs);
604                                 if (err)
605                                         goto error;
606                         }
607                         err = fat_mirror_bhs(sb, bhs, nr_bhs);
608                         if (err)
609                                 goto error;
610                         for (i = 0; i < nr_bhs; i++)
611                                 brelse(bhs[i]);
612                         nr_bhs = 0;
613                 }
614                 fat_collect_bhs(bhs, &nr_bhs, &fatent);
615         } while (cluster != FAT_ENT_EOF);
616
617         if (sb->s_flags & SB_SYNCHRONOUS) {
618                 err = fat_sync_bhs(bhs, nr_bhs);
619                 if (err)
620                         goto error;
621         }
622         err = fat_mirror_bhs(sb, bhs, nr_bhs);
623 error:
624         fatent_brelse(&fatent);
625         for (i = 0; i < nr_bhs; i++)
626                 brelse(bhs[i]);
627         unlock_fat(sbi);
628         if (dirty_fsinfo)
629                 mark_fsinfo_dirty(sb);
630
631         return err;
632 }
633 EXPORT_SYMBOL_GPL(fat_free_clusters);
634
635 /* 128kb is the whole sectors for FAT12 and FAT16 */
636 #define FAT_READA_SIZE          (128 * 1024)
637
638 static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
639                           unsigned long reada_blocks)
640 {
641         const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
642         sector_t blocknr;
643         int i, offset;
644
645         ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
646
647         for (i = 0; i < reada_blocks; i++)
648                 sb_breadahead(sb, blocknr + i);
649 }
650
651 int fat_count_free_clusters(struct super_block *sb)
652 {
653         struct msdos_sb_info *sbi = MSDOS_SB(sb);
654         const struct fatent_operations *ops = sbi->fatent_ops;
655         struct fat_entry fatent;
656         unsigned long reada_blocks, reada_mask, cur_block;
657         int err = 0, free;
658
659         lock_fat(sbi);
660         if (sbi->free_clusters != -1 && sbi->free_clus_valid)
661                 goto out;
662
663         reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
664         reada_mask = reada_blocks - 1;
665         cur_block = 0;
666
667         free = 0;
668         fatent_init(&fatent);
669         fatent_set_entry(&fatent, FAT_START_ENT);
670         while (fatent.entry < sbi->max_cluster) {
671                 /* readahead of fat blocks */
672                 if ((cur_block & reada_mask) == 0) {
673                         unsigned long rest = sbi->fat_length - cur_block;
674                         fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
675                 }
676                 cur_block++;
677
678                 err = fat_ent_read_block(sb, &fatent);
679                 if (err)
680                         goto out;
681
682                 do {
683                         if (ops->ent_get(&fatent) == FAT_ENT_FREE)
684                                 free++;
685                 } while (fat_ent_next(sbi, &fatent));
686                 cond_resched();
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 }
696
697 static int fat_trim_clusters(struct super_block *sb, u32 clus, u32 nr_clus)
698 {
699         struct msdos_sb_info *sbi = MSDOS_SB(sb);
700         return sb_issue_discard(sb, fat_clus_to_blknr(sbi, clus),
701                                 nr_clus * sbi->sec_per_clus, GFP_NOFS, 0);
702 }
703
704 int fat_trim_fs(struct inode *inode, struct fstrim_range *range)
705 {
706         struct super_block *sb = inode->i_sb;
707         struct msdos_sb_info *sbi = MSDOS_SB(sb);
708         const struct fatent_operations *ops = sbi->fatent_ops;
709         struct fat_entry fatent;
710         u64 ent_start, ent_end, minlen, trimmed = 0;
711         u32 free = 0;
712         unsigned long reada_blocks, reada_mask, cur_block = 0;
713         int err = 0;
714
715         /*
716          * FAT data is organized as clusters, trim at the granulary of cluster.
717          *
718          * fstrim_range is in byte, convert vaules to cluster index.
719          * Treat sectors before data region as all used, not to trim them.
720          */
721         ent_start = max_t(u64, range->start>>sbi->cluster_bits, FAT_START_ENT);
722         ent_end = ent_start + (range->len >> sbi->cluster_bits) - 1;
723         minlen = range->minlen >> sbi->cluster_bits;
724
725         if (ent_start >= sbi->max_cluster || range->len < sbi->cluster_size)
726                 return -EINVAL;
727         if (ent_end >= sbi->max_cluster)
728                 ent_end = sbi->max_cluster - 1;
729
730         reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
731         reada_mask = reada_blocks - 1;
732
733         fatent_init(&fatent);
734         lock_fat(sbi);
735         fatent_set_entry(&fatent, ent_start);
736         while (fatent.entry <= ent_end) {
737                 /* readahead of fat blocks */
738                 if ((cur_block & reada_mask) == 0) {
739                         unsigned long rest = sbi->fat_length - cur_block;
740                         fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
741                 }
742                 cur_block++;
743
744                 err = fat_ent_read_block(sb, &fatent);
745                 if (err)
746                         goto error;
747                 do {
748                         if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
749                                 free++;
750                         } else if (free) {
751                                 if (free >= minlen) {
752                                         u32 clus = fatent.entry - free;
753
754                                         err = fat_trim_clusters(sb, clus, free);
755                                         if (err && err != -EOPNOTSUPP)
756                                                 goto error;
757                                         if (!err)
758                                                 trimmed += free;
759                                         err = 0;
760                                 }
761                                 free = 0;
762                         }
763                 } while (fat_ent_next(sbi, &fatent) && fatent.entry <= ent_end);
764
765                 if (fatal_signal_pending(current)) {
766                         err = -ERESTARTSYS;
767                         goto error;
768                 }
769
770                 if (need_resched()) {
771                         fatent_brelse(&fatent);
772                         unlock_fat(sbi);
773                         cond_resched();
774                         lock_fat(sbi);
775                 }
776         }
777         /* handle scenario when tail entries are all free */
778         if (free && free >= minlen) {
779                 u32 clus = fatent.entry - free;
780
781                 err = fat_trim_clusters(sb, clus, free);
782                 if (err && err != -EOPNOTSUPP)
783                         goto error;
784                 if (!err)
785                         trimmed += free;
786                 err = 0;
787         }
788
789 error:
790         fatent_brelse(&fatent);
791         unlock_fat(sbi);
792
793         range->len = trimmed << sbi->cluster_bits;
794
795         return err;
796 }