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1/*
2 * linux/fs/fat/cache.c
3 *
4 * Written 1992,1993 by Werner Almesberger
5 *
6 * Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
7 * of inode number.
8 * May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
9 */
10
11#include <linux/slab.h>
12#include "fat.h"
13
14/* this must be > 0. */
15#define FAT_MAX_CACHE 8
16
17struct fat_cache {
18 struct list_head cache_list;
19 int nr_contig; /* number of contiguous clusters */
20 int fcluster; /* cluster number in the file. */
21 int dcluster; /* cluster number on disk. */
22};
23
24struct fat_cache_id {
25 unsigned int id;
26 int nr_contig;
27 int fcluster;
28 int dcluster;
29};
30
31static inline int fat_max_cache(struct inode *inode)
32{
33 return FAT_MAX_CACHE;
34}
35
36static struct kmem_cache *fat_cache_cachep;
37
38static void init_once(void *foo)
39{
40 struct fat_cache *cache = (struct fat_cache *)foo;
41
42 INIT_LIST_HEAD(&cache->cache_list);
43}
44
45int __init fat_cache_init(void)
46{
47 fat_cache_cachep = kmem_cache_create("fat_cache",
48 sizeof(struct fat_cache),
49 0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
50 init_once);
51 if (fat_cache_cachep == NULL)
52 return -ENOMEM;
53 return 0;
54}
55
56void fat_cache_destroy(void)
57{
58 kmem_cache_destroy(fat_cache_cachep);
59}
60
61static inline struct fat_cache *fat_cache_alloc(struct inode *inode)
62{
63 return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS);
64}
65
66static inline void fat_cache_free(struct fat_cache *cache)
67{
68 BUG_ON(!list_empty(&cache->cache_list));
69 kmem_cache_free(fat_cache_cachep, cache);
70}
71
72static inline void fat_cache_update_lru(struct inode *inode,
73 struct fat_cache *cache)
74{
75 if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list)
76 list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru);
77}
78
79static int fat_cache_lookup(struct inode *inode, int fclus,
80 struct fat_cache_id *cid,
81 int *cached_fclus, int *cached_dclus)
82{
83 static struct fat_cache nohit = { .fcluster = 0, };
84
85 struct fat_cache *hit = &nohit, *p;
86 int offset = -1;
87
88 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
89 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
90 /* Find the cache of "fclus" or nearest cache. */
91 if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
92 hit = p;
93 if ((hit->fcluster + hit->nr_contig) < fclus) {
94 offset = hit->nr_contig;
95 } else {
96 offset = fclus - hit->fcluster;
97 break;
98 }
99 }
100 }
101 if (hit != &nohit) {
102 fat_cache_update_lru(inode, hit);
103
104 cid->id = MSDOS_I(inode)->cache_valid_id;
105 cid->nr_contig = hit->nr_contig;
106 cid->fcluster = hit->fcluster;
107 cid->dcluster = hit->dcluster;
108 *cached_fclus = cid->fcluster + offset;
109 *cached_dclus = cid->dcluster + offset;
110 }
111 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
112
113 return offset;
114}
115
116static struct fat_cache *fat_cache_merge(struct inode *inode,
117 struct fat_cache_id *new)
118{
119 struct fat_cache *p;
120
121 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
122 /* Find the same part as "new" in cluster-chain. */
123 if (p->fcluster == new->fcluster) {
124 BUG_ON(p->dcluster != new->dcluster);
125 if (new->nr_contig > p->nr_contig)
126 p->nr_contig = new->nr_contig;
127 return p;
128 }
129 }
130 return NULL;
131}
132
133static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
134{
135 struct fat_cache *cache, *tmp;
136
137 if (new->fcluster == -1) /* dummy cache */
138 return;
139
140 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
141 if (new->id != FAT_CACHE_VALID &&
142 new->id != MSDOS_I(inode)->cache_valid_id)
143 goto out; /* this cache was invalidated */
144
145 cache = fat_cache_merge(inode, new);
146 if (cache == NULL) {
147 if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
148 MSDOS_I(inode)->nr_caches++;
149 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
150
151 tmp = fat_cache_alloc(inode);
152 if (!tmp) {
153 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
154 MSDOS_I(inode)->nr_caches--;
155 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
156 return;
157 }
158
159 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
160 cache = fat_cache_merge(inode, new);
161 if (cache != NULL) {
162 MSDOS_I(inode)->nr_caches--;
163 fat_cache_free(tmp);
164 goto out_update_lru;
165 }
166 cache = tmp;
167 } else {
168 struct list_head *p = MSDOS_I(inode)->cache_lru.prev;
169 cache = list_entry(p, struct fat_cache, cache_list);
170 }
171 cache->fcluster = new->fcluster;
172 cache->dcluster = new->dcluster;
173 cache->nr_contig = new->nr_contig;
174 }
175out_update_lru:
176 fat_cache_update_lru(inode, cache);
177out:
178 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
179}
180
181/*
182 * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
183 * fixes itself after a while.
184 */
185static void __fat_cache_inval_inode(struct inode *inode)
186{
187 struct msdos_inode_info *i = MSDOS_I(inode);
188 struct fat_cache *cache;
189
190 while (!list_empty(&i->cache_lru)) {
191 cache = list_entry(i->cache_lru.next,
192 struct fat_cache, cache_list);
193 list_del_init(&cache->cache_list);
194 i->nr_caches--;
195 fat_cache_free(cache);
196 }
197 /* Update. The copy of caches before this id is discarded. */
198 i->cache_valid_id++;
199 if (i->cache_valid_id == FAT_CACHE_VALID)
200 i->cache_valid_id++;
201}
202
203void fat_cache_inval_inode(struct inode *inode)
204{
205 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
206 __fat_cache_inval_inode(inode);
207 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
208}
209
210static inline int cache_contiguous(struct fat_cache_id *cid, int dclus)
211{
212 cid->nr_contig++;
213 return ((cid->dcluster + cid->nr_contig) == dclus);
214}
215
216static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
217{
218 cid->id = FAT_CACHE_VALID;
219 cid->fcluster = fclus;
220 cid->dcluster = dclus;
221 cid->nr_contig = 0;
222}
223
224int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
225{
226 struct super_block *sb = inode->i_sb;
227 const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits;
228 struct fat_entry fatent;
229 struct fat_cache_id cid;
230 int nr;
231
232 BUG_ON(MSDOS_I(inode)->i_start == 0);
233
234 *fclus = 0;
235 *dclus = MSDOS_I(inode)->i_start;
236 if (cluster == 0)
237 return 0;
238
239 if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
240 /*
241 * dummy, always not contiguous
242 * This is reinitialized by cache_init(), later.
243 */
244 cache_init(&cid, -1, -1);
245 }
246
247 fatent_init(&fatent);
248 while (*fclus < cluster) {
249 /* prevent the infinite loop of cluster chain */
250 if (*fclus > limit) {
251 fat_fs_error_ratelimit(sb,
252 "%s: detected the cluster chain loop"
253 " (i_pos %lld)", __func__,
254 MSDOS_I(inode)->i_pos);
255 nr = -EIO;
256 goto out;
257 }
258
259 nr = fat_ent_read(inode, &fatent, *dclus);
260 if (nr < 0)
261 goto out;
262 else if (nr == FAT_ENT_FREE) {
263 fat_fs_error_ratelimit(sb,
264 "%s: invalid cluster chain (i_pos %lld)",
265 __func__,
266 MSDOS_I(inode)->i_pos);
267 nr = -EIO;
268 goto out;
269 } else if (nr == FAT_ENT_EOF) {
270 fat_cache_add(inode, &cid);
271 goto out;
272 }
273 (*fclus)++;
274 *dclus = nr;
275 if (!cache_contiguous(&cid, *dclus))
276 cache_init(&cid, *fclus, *dclus);
277 }
278 nr = 0;
279 fat_cache_add(inode, &cid);
280out:
281 fatent_brelse(&fatent);
282 return nr;
283}
284
285static int fat_bmap_cluster(struct inode *inode, int cluster)
286{
287 struct super_block *sb = inode->i_sb;
288 int ret, fclus, dclus;
289
290 if (MSDOS_I(inode)->i_start == 0)
291 return 0;
292
293 ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
294 if (ret < 0)
295 return ret;
296 else if (ret == FAT_ENT_EOF) {
297 fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)",
298 __func__, MSDOS_I(inode)->i_pos);
299 return -EIO;
300 }
301 return dclus;
302}
303
304int fat_get_mapped_cluster(struct inode *inode, sector_t sector,
305 sector_t last_block,
306 unsigned long *mapped_blocks, sector_t *bmap)
307{
308 struct super_block *sb = inode->i_sb;
309 struct msdos_sb_info *sbi = MSDOS_SB(sb);
310 int cluster, offset;
311
312 cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
313 offset = sector & (sbi->sec_per_clus - 1);
314 cluster = fat_bmap_cluster(inode, cluster);
315 if (cluster < 0)
316 return cluster;
317 else if (cluster) {
318 *bmap = fat_clus_to_blknr(sbi, cluster) + offset;
319 *mapped_blocks = sbi->sec_per_clus - offset;
320 if (*mapped_blocks > last_block - sector)
321 *mapped_blocks = last_block - sector;
322 }
323
324 return 0;
325}
326
327static int is_exceed_eof(struct inode *inode, sector_t sector,
328 sector_t *last_block, int create)
329{
330 struct super_block *sb = inode->i_sb;
331 const unsigned long blocksize = sb->s_blocksize;
332 const unsigned char blocksize_bits = sb->s_blocksize_bits;
333
334 *last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
335 if (sector >= *last_block) {
336 if (!create)
337 return 1;
338
339 /*
340 * ->mmu_private can access on only allocation path.
341 * (caller must hold ->i_mutex)
342 */
343 *last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
344 >> blocksize_bits;
345 if (sector >= *last_block)
346 return 1;
347 }
348
349 return 0;
350}
351
352int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
353 unsigned long *mapped_blocks, int create, bool from_bmap)
354{
355 struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
356 sector_t last_block;
357
358 *phys = 0;
359 *mapped_blocks = 0;
360 if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) {
361 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
362 *phys = sector + sbi->dir_start;
363 *mapped_blocks = 1;
364 }
365 return 0;
366 }
367
368 if (!from_bmap) {
369 if (is_exceed_eof(inode, sector, &last_block, create))
370 return 0;
371 } else {
372 last_block = inode->i_blocks >>
373 (inode->i_sb->s_blocksize_bits - 9);
374 if (sector >= last_block)
375 return 0;
376 }
377
378 return fat_get_mapped_cluster(inode, sector, last_block, mapped_blocks,
379 phys);
380}
1/*
2 * linux/fs/fat/cache.c
3 *
4 * Written 1992,1993 by Werner Almesberger
5 *
6 * Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
7 * of inode number.
8 * May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
9 */
10
11#include <linux/fs.h>
12#include <linux/slab.h>
13#include <linux/buffer_head.h>
14#include "fat.h"
15
16/* this must be > 0. */
17#define FAT_MAX_CACHE 8
18
19struct fat_cache {
20 struct list_head cache_list;
21 int nr_contig; /* number of contiguous clusters */
22 int fcluster; /* cluster number in the file. */
23 int dcluster; /* cluster number on disk. */
24};
25
26struct fat_cache_id {
27 unsigned int id;
28 int nr_contig;
29 int fcluster;
30 int dcluster;
31};
32
33static inline int fat_max_cache(struct inode *inode)
34{
35 return FAT_MAX_CACHE;
36}
37
38static struct kmem_cache *fat_cache_cachep;
39
40static void init_once(void *foo)
41{
42 struct fat_cache *cache = (struct fat_cache *)foo;
43
44 INIT_LIST_HEAD(&cache->cache_list);
45}
46
47int __init fat_cache_init(void)
48{
49 fat_cache_cachep = kmem_cache_create("fat_cache",
50 sizeof(struct fat_cache),
51 0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
52 init_once);
53 if (fat_cache_cachep == NULL)
54 return -ENOMEM;
55 return 0;
56}
57
58void fat_cache_destroy(void)
59{
60 kmem_cache_destroy(fat_cache_cachep);
61}
62
63static inline struct fat_cache *fat_cache_alloc(struct inode *inode)
64{
65 return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS);
66}
67
68static inline void fat_cache_free(struct fat_cache *cache)
69{
70 BUG_ON(!list_empty(&cache->cache_list));
71 kmem_cache_free(fat_cache_cachep, cache);
72}
73
74static inline void fat_cache_update_lru(struct inode *inode,
75 struct fat_cache *cache)
76{
77 if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list)
78 list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru);
79}
80
81static int fat_cache_lookup(struct inode *inode, int fclus,
82 struct fat_cache_id *cid,
83 int *cached_fclus, int *cached_dclus)
84{
85 static struct fat_cache nohit = { .fcluster = 0, };
86
87 struct fat_cache *hit = &nohit, *p;
88 int offset = -1;
89
90 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
91 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
92 /* Find the cache of "fclus" or nearest cache. */
93 if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
94 hit = p;
95 if ((hit->fcluster + hit->nr_contig) < fclus) {
96 offset = hit->nr_contig;
97 } else {
98 offset = fclus - hit->fcluster;
99 break;
100 }
101 }
102 }
103 if (hit != &nohit) {
104 fat_cache_update_lru(inode, hit);
105
106 cid->id = MSDOS_I(inode)->cache_valid_id;
107 cid->nr_contig = hit->nr_contig;
108 cid->fcluster = hit->fcluster;
109 cid->dcluster = hit->dcluster;
110 *cached_fclus = cid->fcluster + offset;
111 *cached_dclus = cid->dcluster + offset;
112 }
113 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
114
115 return offset;
116}
117
118static struct fat_cache *fat_cache_merge(struct inode *inode,
119 struct fat_cache_id *new)
120{
121 struct fat_cache *p;
122
123 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
124 /* Find the same part as "new" in cluster-chain. */
125 if (p->fcluster == new->fcluster) {
126 BUG_ON(p->dcluster != new->dcluster);
127 if (new->nr_contig > p->nr_contig)
128 p->nr_contig = new->nr_contig;
129 return p;
130 }
131 }
132 return NULL;
133}
134
135static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
136{
137 struct fat_cache *cache, *tmp;
138
139 if (new->fcluster == -1) /* dummy cache */
140 return;
141
142 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
143 if (new->id != FAT_CACHE_VALID &&
144 new->id != MSDOS_I(inode)->cache_valid_id)
145 goto out; /* this cache was invalidated */
146
147 cache = fat_cache_merge(inode, new);
148 if (cache == NULL) {
149 if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
150 MSDOS_I(inode)->nr_caches++;
151 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
152
153 tmp = fat_cache_alloc(inode);
154 if (!tmp) {
155 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
156 MSDOS_I(inode)->nr_caches--;
157 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
158 return;
159 }
160
161 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
162 cache = fat_cache_merge(inode, new);
163 if (cache != NULL) {
164 MSDOS_I(inode)->nr_caches--;
165 fat_cache_free(tmp);
166 goto out_update_lru;
167 }
168 cache = tmp;
169 } else {
170 struct list_head *p = MSDOS_I(inode)->cache_lru.prev;
171 cache = list_entry(p, struct fat_cache, cache_list);
172 }
173 cache->fcluster = new->fcluster;
174 cache->dcluster = new->dcluster;
175 cache->nr_contig = new->nr_contig;
176 }
177out_update_lru:
178 fat_cache_update_lru(inode, cache);
179out:
180 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
181}
182
183/*
184 * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
185 * fixes itself after a while.
186 */
187static void __fat_cache_inval_inode(struct inode *inode)
188{
189 struct msdos_inode_info *i = MSDOS_I(inode);
190 struct fat_cache *cache;
191
192 while (!list_empty(&i->cache_lru)) {
193 cache = list_entry(i->cache_lru.next,
194 struct fat_cache, cache_list);
195 list_del_init(&cache->cache_list);
196 i->nr_caches--;
197 fat_cache_free(cache);
198 }
199 /* Update. The copy of caches before this id is discarded. */
200 i->cache_valid_id++;
201 if (i->cache_valid_id == FAT_CACHE_VALID)
202 i->cache_valid_id++;
203}
204
205void fat_cache_inval_inode(struct inode *inode)
206{
207 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
208 __fat_cache_inval_inode(inode);
209 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
210}
211
212static inline int cache_contiguous(struct fat_cache_id *cid, int dclus)
213{
214 cid->nr_contig++;
215 return ((cid->dcluster + cid->nr_contig) == dclus);
216}
217
218static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
219{
220 cid->id = FAT_CACHE_VALID;
221 cid->fcluster = fclus;
222 cid->dcluster = dclus;
223 cid->nr_contig = 0;
224}
225
226int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
227{
228 struct super_block *sb = inode->i_sb;
229 const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits;
230 struct fat_entry fatent;
231 struct fat_cache_id cid;
232 int nr;
233
234 BUG_ON(MSDOS_I(inode)->i_start == 0);
235
236 *fclus = 0;
237 *dclus = MSDOS_I(inode)->i_start;
238 if (cluster == 0)
239 return 0;
240
241 if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
242 /*
243 * dummy, always not contiguous
244 * This is reinitialized by cache_init(), later.
245 */
246 cache_init(&cid, -1, -1);
247 }
248
249 fatent_init(&fatent);
250 while (*fclus < cluster) {
251 /* prevent the infinite loop of cluster chain */
252 if (*fclus > limit) {
253 fat_fs_error_ratelimit(sb,
254 "%s: detected the cluster chain loop"
255 " (i_pos %lld)", __func__,
256 MSDOS_I(inode)->i_pos);
257 nr = -EIO;
258 goto out;
259 }
260
261 nr = fat_ent_read(inode, &fatent, *dclus);
262 if (nr < 0)
263 goto out;
264 else if (nr == FAT_ENT_FREE) {
265 fat_fs_error_ratelimit(sb,
266 "%s: invalid cluster chain (i_pos %lld)",
267 __func__,
268 MSDOS_I(inode)->i_pos);
269 nr = -EIO;
270 goto out;
271 } else if (nr == FAT_ENT_EOF) {
272 fat_cache_add(inode, &cid);
273 goto out;
274 }
275 (*fclus)++;
276 *dclus = nr;
277 if (!cache_contiguous(&cid, *dclus))
278 cache_init(&cid, *fclus, *dclus);
279 }
280 nr = 0;
281 fat_cache_add(inode, &cid);
282out:
283 fatent_brelse(&fatent);
284 return nr;
285}
286
287static int fat_bmap_cluster(struct inode *inode, int cluster)
288{
289 struct super_block *sb = inode->i_sb;
290 int ret, fclus, dclus;
291
292 if (MSDOS_I(inode)->i_start == 0)
293 return 0;
294
295 ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
296 if (ret < 0)
297 return ret;
298 else if (ret == FAT_ENT_EOF) {
299 fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)",
300 __func__, MSDOS_I(inode)->i_pos);
301 return -EIO;
302 }
303 return dclus;
304}
305
306int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
307 unsigned long *mapped_blocks, int create)
308{
309 struct super_block *sb = inode->i_sb;
310 struct msdos_sb_info *sbi = MSDOS_SB(sb);
311 const unsigned long blocksize = sb->s_blocksize;
312 const unsigned char blocksize_bits = sb->s_blocksize_bits;
313 sector_t last_block;
314 int cluster, offset;
315
316 *phys = 0;
317 *mapped_blocks = 0;
318 if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) {
319 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
320 *phys = sector + sbi->dir_start;
321 *mapped_blocks = 1;
322 }
323 return 0;
324 }
325
326 last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
327 if (sector >= last_block) {
328 if (!create)
329 return 0;
330
331 /*
332 * ->mmu_private can access on only allocation path.
333 * (caller must hold ->i_mutex)
334 */
335 last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
336 >> blocksize_bits;
337 if (sector >= last_block)
338 return 0;
339 }
340
341 cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
342 offset = sector & (sbi->sec_per_clus - 1);
343 cluster = fat_bmap_cluster(inode, cluster);
344 if (cluster < 0)
345 return cluster;
346 else if (cluster) {
347 *phys = fat_clus_to_blknr(sbi, cluster) + offset;
348 *mapped_blocks = sbi->sec_per_clus - offset;
349 if (*mapped_blocks > last_block - sector)
350 *mapped_blocks = last_block - sector;
351 }
352 return 0;
353}