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/msdos_fs.h> 13 #include <linux/buffer_head.h> 14 15 /* this must be > 0. */ 16 #define FAT_MAX_CACHE 8 17 18 struct 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 25 struct fat_cache_id { 26 unsigned int id; 27 int nr_contig; 28 int fcluster; 29 int dcluster; 30 }; 31 32 static inline int fat_max_cache(struct inode *inode) 33 { 34 return FAT_MAX_CACHE; 35 } 36 37 static struct kmem_cache *fat_cache_cachep; 38 39 static 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 46 int __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 57 void fat_cache_destroy(void) 58 { 59 kmem_cache_destroy(fat_cache_cachep); 60 } 61 62 static inline struct fat_cache *fat_cache_alloc(struct inode *inode) 63 { 64 return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS); 65 } 66 67 static 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 73 static 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 80 static 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 /* Find the cache of "fclus" or nearest cache. */ 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 } 116 117 static 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 /* Find the same part as "new" in cluster-chain. */ 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 } 133 134 static 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) /* dummy cache */ 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; /* this cache was invalidated */ 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 } 169 out_update_lru: 170 fat_cache_update_lru(inode, cache); 171 out: 172 spin_unlock(&MSDOS_I(inode)->cache_lru_lock); 173 } 174 175 /* 176 * Cache invalidation occurs rarely, thus the LRU chain is not updated. It 177 * fixes itself after a while. 178 */ 179 static 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 /* Update. The copy of caches before this id is discarded. */ 191 i->cache_valid_id++; 192 if (i->cache_valid_id == FAT_CACHE_VALID) 193 i->cache_valid_id++; 194 } 195 196 void 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 } 202 203 static 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 } 208 209 static 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 } 216 217 int 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 * dummy, always not contiguous 235 * This is reinitialized by cache_init(), later. 236 */ 237 cache_init(&cid, -1, -1); 238 } 239 240 fatent_init(&fatent); 241 while (*fclus < cluster) { 242 /* prevent the infinite loop of cluster chain */ 243 if (*fclus > limit) { 244 fat_fs_panic(sb, "%s: detected the cluster chain loop" 245 " (i_pos %lld)", __func__, 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)", __func__, 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); 271 out: 272 fatent_brelse(&fatent); 273 return nr; 274 } 275 276 static 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 __func__, MSDOS_I(inode)->i_pos); 290 return -EIO; 291 } 292 return dclus; 293 } 294 295 int 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