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11#include <linux/fs.h>
12#include <linux/msdos_fs.h>
13#include <linux/buffer_head.h>
14
15
16#define FAT_MAX_CACHE 8
17
18struct fat_cache {
19 struct list_head cache_list;
20 int nr_contig;
21 int fcluster;
22 int dcluster;
23};
24
25struct fat_cache_id {
26 unsigned int id;
27 int nr_contig;
28 int fcluster;
29 int dcluster;
30};
31
32static inline int fat_max_cache(struct inode *inode)
33{
34 return FAT_MAX_CACHE;
35}
36
37static struct kmem_cache *fat_cache_cachep;
38
39static void init_once(struct kmem_cache *cachep, void *foo)
40{
41 struct fat_cache *cache = (struct fat_cache *)foo;
42
43 INIT_LIST_HEAD(&cache->cache_list);
44}
45
46int __init fat_cache_init(void)
47{
48 fat_cache_cachep = kmem_cache_create("fat_cache",
49 sizeof(struct fat_cache),
50 0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
51 init_once);
52 if (fat_cache_cachep == NULL)
53 return -ENOMEM;
54 return 0;
55}
56
57void fat_cache_destroy(void)
58{
59 kmem_cache_destroy(fat_cache_cachep);
60}
61
62static inline struct fat_cache *fat_cache_alloc(struct inode *inode)
63{
64 return kmem_cache_alloc(fat_cache_cachep, GFP_KERNEL);
65}
66
67static inline void fat_cache_free(struct fat_cache *cache)
68{
69 BUG_ON(!list_empty(&cache->cache_list));
70 kmem_cache_free(fat_cache_cachep, cache);
71}
72
73static inline void fat_cache_update_lru(struct inode *inode,
74 struct fat_cache *cache)
75{
76 if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list)
77 list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru);
78}
79
80static int fat_cache_lookup(struct inode *inode, int fclus,
81 struct fat_cache_id *cid,
82 int *cached_fclus, int *cached_dclus)
83{
84 static struct fat_cache nohit = { .fcluster = 0, };
85
86 struct fat_cache *hit = &nohit, *p;
87 int offset = -1;
88
89 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
90 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
91
92 if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
93 hit = p;
94 if ((hit->fcluster + hit->nr_contig) < fclus) {
95 offset = hit->nr_contig;
96 } else {
97 offset = fclus - hit->fcluster;
98 break;
99 }
100 }
101 }
102 if (hit != &nohit) {
103 fat_cache_update_lru(inode, hit);
104
105 cid->id = MSDOS_I(inode)->cache_valid_id;
106 cid->nr_contig = hit->nr_contig;
107 cid->fcluster = hit->fcluster;
108 cid->dcluster = hit->dcluster;
109 *cached_fclus = cid->fcluster + offset;
110 *cached_dclus = cid->dcluster + offset;
111 }
112 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
113
114 return offset;
115}
116
117static struct fat_cache *fat_cache_merge(struct inode *inode,
118 struct fat_cache_id *new)
119{
120 struct fat_cache *p;
121
122 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
123
124 if (p->fcluster == new->fcluster) {
125 BUG_ON(p->dcluster != new->dcluster);
126 if (new->nr_contig > p->nr_contig)
127 p->nr_contig = new->nr_contig;
128 return p;
129 }
130 }
131 return NULL;
132}
133
134static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
135{
136 struct fat_cache *cache, *tmp;
137
138 if (new->fcluster == -1)
139 return;
140
141 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
142 if (new->id != FAT_CACHE_VALID &&
143 new->id != MSDOS_I(inode)->cache_valid_id)
144 goto out;
145
146 cache = fat_cache_merge(inode, new);
147 if (cache == NULL) {
148 if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
149 MSDOS_I(inode)->nr_caches++;
150 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
151
152 tmp = fat_cache_alloc(inode);
153 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
154 cache = fat_cache_merge(inode, new);
155 if (cache != NULL) {
156 MSDOS_I(inode)->nr_caches--;
157 fat_cache_free(tmp);
158 goto out_update_lru;
159 }
160 cache = tmp;
161 } else {
162 struct list_head *p = MSDOS_I(inode)->cache_lru.prev;
163 cache = list_entry(p, struct fat_cache, cache_list);
164 }
165 cache->fcluster = new->fcluster;
166 cache->dcluster = new->dcluster;
167 cache->nr_contig = new->nr_contig;
168 }
169out_update_lru:
170 fat_cache_update_lru(inode, cache);
171out:
172 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
173}
174
175
176
177
178
179static void __fat_cache_inval_inode(struct inode *inode)
180{
181 struct msdos_inode_info *i = MSDOS_I(inode);
182 struct fat_cache *cache;
183
184 while (!list_empty(&i->cache_lru)) {
185 cache = list_entry(i->cache_lru.next, struct fat_cache, cache_list);
186 list_del_init(&cache->cache_list);
187 i->nr_caches--;
188 fat_cache_free(cache);
189 }
190
191 i->cache_valid_id++;
192 if (i->cache_valid_id == FAT_CACHE_VALID)
193 i->cache_valid_id++;
194}
195
196void fat_cache_inval_inode(struct inode *inode)
197{
198 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
199 __fat_cache_inval_inode(inode);
200 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
201}
202
203static inline int cache_contiguous(struct fat_cache_id *cid, int dclus)
204{
205 cid->nr_contig++;
206 return ((cid->dcluster + cid->nr_contig) == dclus);
207}
208
209static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
210{
211 cid->id = FAT_CACHE_VALID;
212 cid->fcluster = fclus;
213 cid->dcluster = dclus;
214 cid->nr_contig = 0;
215}
216
217int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
218{
219 struct super_block *sb = inode->i_sb;
220 const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits;
221 struct fat_entry fatent;
222 struct fat_cache_id cid;
223 int nr;
224
225 BUG_ON(MSDOS_I(inode)->i_start == 0);
226
227 *fclus = 0;
228 *dclus = MSDOS_I(inode)->i_start;
229 if (cluster == 0)
230 return 0;
231
232 if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
233
234
235
236
237 cache_init(&cid, -1, -1);
238 }
239
240 fatent_init(&fatent);
241 while (*fclus < cluster) {
242
243 if (*fclus > limit) {
244 fat_fs_panic(sb, "%s: detected the cluster chain loop"
245 " (i_pos %lld)", __FUNCTION__,
246 MSDOS_I(inode)->i_pos);
247 nr = -EIO;
248 goto out;
249 }
250
251 nr = fat_ent_read(inode, &fatent, *dclus);
252 if (nr < 0)
253 goto out;
254 else if (nr == FAT_ENT_FREE) {
255 fat_fs_panic(sb, "%s: invalid cluster chain"
256 " (i_pos %lld)", __FUNCTION__,
257 MSDOS_I(inode)->i_pos);
258 nr = -EIO;
259 goto out;
260 } else if (nr == FAT_ENT_EOF) {
261 fat_cache_add(inode, &cid);
262 goto out;
263 }
264 (*fclus)++;
265 *dclus = nr;
266 if (!cache_contiguous(&cid, *dclus))
267 cache_init(&cid, *fclus, *dclus);
268 }
269 nr = 0;
270 fat_cache_add(inode, &cid);
271out:
272 fatent_brelse(&fatent);
273 return nr;
274}
275
276static int fat_bmap_cluster(struct inode *inode, int cluster)
277{
278 struct super_block *sb = inode->i_sb;
279 int ret, fclus, dclus;
280
281 if (MSDOS_I(inode)->i_start == 0)
282 return 0;
283
284 ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
285 if (ret < 0)
286 return ret;
287 else if (ret == FAT_ENT_EOF) {
288 fat_fs_panic(sb, "%s: request beyond EOF (i_pos %lld)",
289 __FUNCTION__, MSDOS_I(inode)->i_pos);
290 return -EIO;
291 }
292 return dclus;
293}
294
295int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
296 unsigned long *mapped_blocks)
297{
298 struct super_block *sb = inode->i_sb;
299 struct msdos_sb_info *sbi = MSDOS_SB(sb);
300 sector_t last_block;
301 int cluster, offset;
302
303 *phys = 0;
304 *mapped_blocks = 0;
305 if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) {
306 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
307 *phys = sector + sbi->dir_start;
308 *mapped_blocks = 1;
309 }
310 return 0;
311 }
312 last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
313 >> sb->s_blocksize_bits;
314 if (sector >= last_block)
315 return 0;
316
317 cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
318 offset = sector & (sbi->sec_per_clus - 1);
319 cluster = fat_bmap_cluster(inode, cluster);
320 if (cluster < 0)
321 return cluster;
322 else if (cluster) {
323 *phys = fat_clus_to_blknr(sbi, cluster) + offset;
324 *mapped_blocks = sbi->sec_per_clus - offset;
325 if (*mapped_blocks > last_block - sector)
326 *mapped_blocks = last_block - sector;
327 }
328 return 0;
329}
330