blob: 82cc4f59e3bae3302abd291b392eccb90f4e1be4 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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/msdos_fs.h>
13#include <linux/buffer_head.h>
14
15/* this must be > 0. */
16#define FAT_MAX_CACHE 8
17
18struct fat_cache {
19 struct list_head cache_list;
20 int nr_contig; /* number of contiguous clusters */
21 int fcluster; /* cluster number in the file. */
22 int dcluster; /* cluster number on disk. */
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 kmem_cache_t *fat_cache_cachep;
38
39static void init_once(void *foo, kmem_cache_t *cachep, unsigned long flags)
40{
41 struct fat_cache *cache = (struct fat_cache *)foo;
42
43 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
44 SLAB_CTOR_CONSTRUCTOR)
45 INIT_LIST_HEAD(&cache->cache_list);
46}
47
48int __init fat_cache_init(void)
49{
50 fat_cache_cachep = kmem_cache_create("fat_cache",
51 sizeof(struct fat_cache),
Paul Jackson4b6a9312006-03-24 03:16:05 -080052 0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 init_once, NULL);
54 if (fat_cache_cachep == NULL)
55 return -ENOMEM;
56 return 0;
57}
58
Andrew Mortonef6689e2005-06-30 22:13:14 -070059void fat_cache_destroy(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -070060{
Alexey Dobriyan1a1d92c2006-09-27 01:49:40 -070061 kmem_cache_destroy(fat_cache_cachep);
Linus Torvalds1da177e2005-04-16 15:20:36 -070062}
63
64static inline struct fat_cache *fat_cache_alloc(struct inode *inode)
65{
66 return kmem_cache_alloc(fat_cache_cachep, SLAB_KERNEL);
67}
68
69static inline void fat_cache_free(struct fat_cache *cache)
70{
71 BUG_ON(!list_empty(&cache->cache_list));
72 kmem_cache_free(fat_cache_cachep, cache);
73}
74
75static inline void fat_cache_update_lru(struct inode *inode,
76 struct fat_cache *cache)
77{
78 if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list)
79 list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru);
80}
81
82static int fat_cache_lookup(struct inode *inode, int fclus,
83 struct fat_cache_id *cid,
84 int *cached_fclus, int *cached_dclus)
85{
86 static struct fat_cache nohit = { .fcluster = 0, };
87
88 struct fat_cache *hit = &nohit, *p;
89 int offset = -1;
90
91 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
92 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
93 /* Find the cache of "fclus" or nearest cache. */
94 if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
95 hit = p;
96 if ((hit->fcluster + hit->nr_contig) < fclus) {
97 offset = hit->nr_contig;
98 } else {
99 offset = fclus - hit->fcluster;
100 break;
101 }
102 }
103 }
104 if (hit != &nohit) {
105 fat_cache_update_lru(inode, hit);
106
107 cid->id = MSDOS_I(inode)->cache_valid_id;
108 cid->nr_contig = hit->nr_contig;
109 cid->fcluster = hit->fcluster;
110 cid->dcluster = hit->dcluster;
111 *cached_fclus = cid->fcluster + offset;
112 *cached_dclus = cid->dcluster + offset;
113 }
114 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
115
116 return offset;
117}
118
119static struct fat_cache *fat_cache_merge(struct inode *inode,
120 struct fat_cache_id *new)
121{
122 struct fat_cache *p;
123
124 list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
125 /* Find the same part as "new" in cluster-chain. */
126 if (p->fcluster == new->fcluster) {
127 BUG_ON(p->dcluster != new->dcluster);
128 if (new->nr_contig > p->nr_contig)
129 p->nr_contig = new->nr_contig;
130 return p;
131 }
132 }
133 return NULL;
134}
135
136static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
137{
138 struct fat_cache *cache, *tmp;
139
140 if (new->fcluster == -1) /* dummy cache */
141 return;
142
143 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
144 if (new->id != FAT_CACHE_VALID &&
145 new->id != MSDOS_I(inode)->cache_valid_id)
146 goto out; /* this cache was invalidated */
147
148 cache = fat_cache_merge(inode, new);
149 if (cache == NULL) {
150 if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) {
151 MSDOS_I(inode)->nr_caches++;
152 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
153
154 tmp = fat_cache_alloc(inode);
155 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
156 cache = fat_cache_merge(inode, new);
157 if (cache != NULL) {
158 MSDOS_I(inode)->nr_caches--;
159 fat_cache_free(tmp);
160 goto out_update_lru;
161 }
162 cache = tmp;
163 } else {
164 struct list_head *p = MSDOS_I(inode)->cache_lru.prev;
165 cache = list_entry(p, struct fat_cache, cache_list);
166 }
167 cache->fcluster = new->fcluster;
168 cache->dcluster = new->dcluster;
169 cache->nr_contig = new->nr_contig;
170 }
171out_update_lru:
172 fat_cache_update_lru(inode, cache);
173out:
174 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
175}
176
177/*
178 * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
179 * fixes itself after a while.
180 */
181static void __fat_cache_inval_inode(struct inode *inode)
182{
183 struct msdos_inode_info *i = MSDOS_I(inode);
184 struct fat_cache *cache;
185
186 while (!list_empty(&i->cache_lru)) {
187 cache = list_entry(i->cache_lru.next, struct fat_cache, cache_list);
188 list_del_init(&cache->cache_list);
189 i->nr_caches--;
190 fat_cache_free(cache);
191 }
192 /* Update. The copy of caches before this id is discarded. */
193 i->cache_valid_id++;
194 if (i->cache_valid_id == FAT_CACHE_VALID)
195 i->cache_valid_id++;
196}
197
198void fat_cache_inval_inode(struct inode *inode)
199{
200 spin_lock(&MSDOS_I(inode)->cache_lru_lock);
201 __fat_cache_inval_inode(inode);
202 spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
203}
204
205static inline int cache_contiguous(struct fat_cache_id *cid, int dclus)
206{
207 cid->nr_contig++;
208 return ((cid->dcluster + cid->nr_contig) == dclus);
209}
210
211static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
212{
213 cid->id = FAT_CACHE_VALID;
214 cid->fcluster = fclus;
215 cid->dcluster = dclus;
216 cid->nr_contig = 0;
217}
218
219int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
220{
221 struct super_block *sb = inode->i_sb;
222 const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits;
223 struct fat_entry fatent;
224 struct fat_cache_id cid;
225 int nr;
226
227 BUG_ON(MSDOS_I(inode)->i_start == 0);
228
229 *fclus = 0;
230 *dclus = MSDOS_I(inode)->i_start;
231 if (cluster == 0)
232 return 0;
233
234 if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
235 /*
236 * dummy, always not contiguous
237 * This is reinitialized by cache_init(), later.
238 */
239 cache_init(&cid, -1, -1);
240 }
241
242 fatent_init(&fatent);
243 while (*fclus < cluster) {
244 /* prevent the infinite loop of cluster chain */
245 if (*fclus > limit) {
246 fat_fs_panic(sb, "%s: detected the cluster chain loop"
247 " (i_pos %lld)", __FUNCTION__,
248 MSDOS_I(inode)->i_pos);
249 nr = -EIO;
250 goto out;
251 }
252
253 nr = fat_ent_read(inode, &fatent, *dclus);
254 if (nr < 0)
255 goto out;
256 else if (nr == FAT_ENT_FREE) {
257 fat_fs_panic(sb, "%s: invalid cluster chain"
258 " (i_pos %lld)", __FUNCTION__,
259 MSDOS_I(inode)->i_pos);
260 nr = -EIO;
261 goto out;
262 } else if (nr == FAT_ENT_EOF) {
263 fat_cache_add(inode, &cid);
264 goto out;
265 }
266 (*fclus)++;
267 *dclus = nr;
268 if (!cache_contiguous(&cid, *dclus))
269 cache_init(&cid, *fclus, *dclus);
270 }
271 nr = 0;
272 fat_cache_add(inode, &cid);
273out:
274 fatent_brelse(&fatent);
275 return nr;
276}
277
278static int fat_bmap_cluster(struct inode *inode, int cluster)
279{
280 struct super_block *sb = inode->i_sb;
281 int ret, fclus, dclus;
282
283 if (MSDOS_I(inode)->i_start == 0)
284 return 0;
285
286 ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
287 if (ret < 0)
288 return ret;
289 else if (ret == FAT_ENT_EOF) {
290 fat_fs_panic(sb, "%s: request beyond EOF (i_pos %lld)",
291 __FUNCTION__, MSDOS_I(inode)->i_pos);
292 return -EIO;
293 }
294 return dclus;
295}
296
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800297int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
298 unsigned long *mapped_blocks)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299{
300 struct super_block *sb = inode->i_sb;
301 struct msdos_sb_info *sbi = MSDOS_SB(sb);
302 sector_t last_block;
303 int cluster, offset;
304
305 *phys = 0;
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800306 *mapped_blocks = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307 if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) {
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800308 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309 *phys = sector + sbi->dir_start;
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800310 *mapped_blocks = 1;
311 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312 return 0;
313 }
314 last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
315 >> sb->s_blocksize_bits;
316 if (sector >= last_block)
317 return 0;
318
319 cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
320 offset = sector & (sbi->sec_per_clus - 1);
321 cluster = fat_bmap_cluster(inode, cluster);
322 if (cluster < 0)
323 return cluster;
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800324 else if (cluster) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700325 *phys = fat_clus_to_blknr(sbi, cluster) + offset;
OGAWA Hirofumie5174ba2006-01-08 01:02:11 -0800326 *mapped_blocks = sbi->sec_per_clus - offset;
327 if (*mapped_blocks > last_block - sector)
328 *mapped_blocks = last_block - sector;
329 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330 return 0;
331}