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 19 struct 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 26 struct fat_cache_id { 27 unsigned int id; 28 int nr_contig; 29 int fcluster; 30 int dcluster; 31 }; 32 33 static inline int fat_max_cache(struct inode *inode) 34 { 35 return FAT_MAX_CACHE; 36 } 37 38 static struct kmem_cache *fat_cache_cachep; 39 40 static 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 47 int __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 58 void fat_cache_destroy(void) 59 { 60 kmem_cache_destroy(fat_cache_cachep); 61 } 62 63 static inline struct fat_cache *fat_cache_alloc(struct inode *inode) 64 { 65 return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS); 66 } 67 68 static 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 74 static 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 81 static 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 } 117 118 static 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 } 134 135 static 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 spin_lock(&MSDOS_I(inode)->cache_lru_lock); 155 cache = fat_cache_merge(inode, new); 156 if (cache != NULL) { 157 MSDOS_I(inode)->nr_caches--; 158 fat_cache_free(tmp); 159 goto out_update_lru; 160 } 161 cache = tmp; 162 } else { 163 struct list_head *p = MSDOS_I(inode)->cache_lru.prev; 164 cache = list_entry(p, struct fat_cache, cache_list); 165 } 166 cache->fcluster = new->fcluster; 167 cache->dcluster = new->dcluster; 168 cache->nr_contig = new->nr_contig; 169 } 170 out_update_lru: 171 fat_cache_update_lru(inode, cache); 172 out: 173 spin_unlock(&MSDOS_I(inode)->cache_lru_lock); 174 } 175 176 /* 177 * Cache invalidation occurs rarely, thus the LRU chain is not updated. It 178 * fixes itself after a while. 179 */ 180 static void __fat_cache_inval_inode(struct inode *inode) 181 { 182 struct msdos_inode_info *i = MSDOS_I(inode); 183 struct fat_cache *cache; 184 185 while (!list_empty(&i->cache_lru)) { 186 cache = list_entry(i->cache_lru.next, struct fat_cache, cache_list); 187 list_del_init(&cache->cache_list); 188 i->nr_caches--; 189 fat_cache_free(cache); 190 } 191 /* Update. The copy of caches before this id is discarded. */ 192 i->cache_valid_id++; 193 if (i->cache_valid_id == FAT_CACHE_VALID) 194 i->cache_valid_id++; 195 } 196 197 void fat_cache_inval_inode(struct inode *inode) 198 { 199 spin_lock(&MSDOS_I(inode)->cache_lru_lock); 200 __fat_cache_inval_inode(inode); 201 spin_unlock(&MSDOS_I(inode)->cache_lru_lock); 202 } 203 204 static inline int cache_contiguous(struct fat_cache_id *cid, int dclus) 205 { 206 cid->nr_contig++; 207 return ((cid->dcluster + cid->nr_contig) == dclus); 208 } 209 210 static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus) 211 { 212 cid->id = FAT_CACHE_VALID; 213 cid->fcluster = fclus; 214 cid->dcluster = dclus; 215 cid->nr_contig = 0; 216 } 217 218 int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus) 219 { 220 struct super_block *sb = inode->i_sb; 221 const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits; 222 struct fat_entry fatent; 223 struct fat_cache_id cid; 224 int nr; 225 226 BUG_ON(MSDOS_I(inode)->i_start == 0); 227 228 *fclus = 0; 229 *dclus = MSDOS_I(inode)->i_start; 230 if (cluster == 0) 231 return 0; 232 233 if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) { 234 /* 235 * dummy, always not contiguous 236 * This is reinitialized by cache_init(), later. 237 */ 238 cache_init(&cid, -1, -1); 239 } 240 241 fatent_init(&fatent); 242 while (*fclus < cluster) { 243 /* prevent the infinite loop of cluster chain */ 244 if (*fclus > limit) { 245 fat_fs_error(sb, "%s: detected the cluster chain loop" 246 " (i_pos %lld)", __func__, 247 MSDOS_I(inode)->i_pos); 248 nr = -EIO; 249 goto out; 250 } 251 252 nr = fat_ent_read(inode, &fatent, *dclus); 253 if (nr < 0) 254 goto out; 255 else if (nr == FAT_ENT_FREE) { 256 fat_fs_error(sb, "%s: invalid cluster chain" 257 " (i_pos %lld)", __func__, 258 MSDOS_I(inode)->i_pos); 259 nr = -EIO; 260 goto out; 261 } else if (nr == FAT_ENT_EOF) { 262 fat_cache_add(inode, &cid); 263 goto out; 264 } 265 (*fclus)++; 266 *dclus = nr; 267 if (!cache_contiguous(&cid, *dclus)) 268 cache_init(&cid, *fclus, *dclus); 269 } 270 nr = 0; 271 fat_cache_add(inode, &cid); 272 out: 273 fatent_brelse(&fatent); 274 return nr; 275 } 276 277 static int fat_bmap_cluster(struct inode *inode, int cluster) 278 { 279 struct super_block *sb = inode->i_sb; 280 int ret, fclus, dclus; 281 282 if (MSDOS_I(inode)->i_start == 0) 283 return 0; 284 285 ret = fat_get_cluster(inode, cluster, &fclus, &dclus); 286 if (ret < 0) 287 return ret; 288 else if (ret == FAT_ENT_EOF) { 289 fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)", 290 __func__, MSDOS_I(inode)->i_pos); 291 return -EIO; 292 } 293 return dclus; 294 } 295 296 int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys, 297 unsigned long *mapped_blocks, int create) 298 { 299 struct super_block *sb = inode->i_sb; 300 struct msdos_sb_info *sbi = MSDOS_SB(sb); 301 const unsigned long blocksize = sb->s_blocksize; 302 const unsigned char blocksize_bits = sb->s_blocksize_bits; 303 sector_t last_block; 304 int cluster, offset; 305 306 *phys = 0; 307 *mapped_blocks = 0; 308 if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) { 309 if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) { 310 *phys = sector + sbi->dir_start; 311 *mapped_blocks = 1; 312 } 313 return 0; 314 } 315 316 last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits; 317 if (sector >= last_block) { 318 if (!create) 319 return 0; 320 321 /* 322 * ->mmu_private can access on only allocation path. 323 * (caller must hold ->i_mutex) 324 */ 325 last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1)) 326 >> blocksize_bits; 327 if (sector >= last_block) 328 return 0; 329 } 330 331 cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits); 332 offset = sector & (sbi->sec_per_clus - 1); 333 cluster = fat_bmap_cluster(inode, cluster); 334 if (cluster < 0) 335 return cluster; 336 else if (cluster) { 337 *phys = fat_clus_to_blknr(sbi, cluster) + offset; 338 *mapped_blocks = sbi->sec_per_clus - offset; 339 if (*mapped_blocks > last_block - sector) 340 *mapped_blocks = last_block - sector; 341 } 342 return 0; 343 } 344