/* * linux/fs/fat/cache.c * * Written 1992,1993 by Werner Almesberger * * Mar 1999. AV. Changed cache, so that it uses the starting cluster instead * of inode number. * May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers. */ #include <linux/fs.h> #include <linux/msdos_fs.h> #include <linux/buffer_head.h> /* this must be > 0. */ #define FAT_MAX_CACHE 8 struct fat_cache { struct list_head cache_list; int nr_contig; /* number of contiguous clusters */ int fcluster; /* cluster number in the file. */ int dcluster; /* cluster number on disk. */ }; struct fat_cache_id { unsigned int id; int nr_contig; int fcluster; int dcluster; }; static inline int fat_max_cache(struct inode *inode) { return FAT_MAX_CACHE; } static struct kmem_cache *fat_cache_cachep; static void init_once(void *foo, struct kmem_cache *cachep, unsigned long flags) { struct fat_cache *cache = (struct fat_cache *)foo; INIT_LIST_HEAD(&cache->cache_list); } int __init fat_cache_init(void) { fat_cache_cachep = kmem_cache_create("fat_cache", sizeof(struct fat_cache), 0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, init_once); if (fat_cache_cachep == NULL) return -ENOMEM; return 0; } void fat_cache_destroy(void) { kmem_cache_destroy(fat_cache_cachep); } static inline struct fat_cache *fat_cache_alloc(struct inode *inode) { return kmem_cache_alloc(fat_cache_cachep, GFP_KERNEL); } static inline void fat_cache_free(struct fat_cache *cache) { BUG_ON(!list_empty(&cache->cache_list)); kmem_cache_free(fat_cache_cachep, cache); } static inline void fat_cache_update_lru(struct inode *inode, struct fat_cache *cache) { if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list) list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru); } static int fat_cache_lookup(struct inode *inode, int fclus, struct fat_cache_id *cid, int *cached_fclus, int *cached_dclus) { static struct fat_cache nohit = { .fcluster = 0, }; struct fat_cache *hit = &nohit, *p; int offset = -1; spin_lock(&MSDOS_I(inode)->cache_lru_lock); list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) { /* Find the cache of "fclus" or nearest cache. */ if (p->fcluster <= fclus && hit->fcluster < p->fcluster) { hit = p; if ((hit->fcluster + hit->nr_contig) < fclus) { offset = hit->nr_contig; } else { offset = fclus - hit->fcluster; break; } } } if (hit != &nohit) { fat_cache_update_lru(inode, hit); cid->id = MSDOS_I(inode)->cache_valid_id; cid->nr_contig = hit->nr_contig; cid->fcluster = hit->fcluster; cid->dcluster = hit->dcluster; *cached_fclus = cid->fcluster + offset; *cached_dclus = cid->dcluster + offset; } spin_unlock(&MSDOS_I(inode)->cache_lru_lock); return offset; } static struct fat_cache *fat_cache_merge(struct inode *inode, struct fat_cache_id *new) { struct fat_cache *p; list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) { /* Find the same part as "new" in cluster-chain. */ if (p->fcluster == new->fcluster) { BUG_ON(p->dcluster != new->dcluster); if (new->nr_contig > p->nr_contig) p->nr_contig = new->nr_contig; return p; } } return NULL; } static void fat_cache_add(struct inode *inode, struct fat_cache_id *new) { struct fat_cache *cache, *tmp; if (new->fcluster == -1) /* dummy cache */ return; spin_lock(&MSDOS_I(inode)->cache_lru_lock); if (new->id != FAT_CACHE_VALID && new->id != MSDOS_I(inode)->cache_valid_id) goto out; /* this cache was invalidated */ cache = fat_cache_merge(inode, new); if (cache == NULL) { if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) { MSDOS_I(inode)->nr_caches++; spin_unlock(&MSDOS_I(inode)->cache_lru_lock); tmp = fat_cache_alloc(inode); spin_lock(&MSDOS_I(inode)->cache_lru_lock); cache = fat_cache_merge(inode, new); if (cache != NULL) { MSDOS_I(inode)->nr_caches--; fat_cache_free(tmp); goto out_update_lru; } cache = tmp; } else { struct list_head *p = MSDOS_I(inode)->cache_lru.prev; cache = list_entry(p, struct fat_cache, cache_list); } cache->fcluster = new->fcluster; cache->dcluster = new->dcluster; cache->nr_contig = new->nr_contig; } out_update_lru: fat_cache_update_lru(inode, cache); out: spin_unlock(&MSDOS_I(inode)->cache_lru_lock); } /* * Cache invalidation occurs rarely, thus the LRU chain is not updated. It * fixes itself after a while. */ static void __fat_cache_inval_inode(struct inode *inode) { struct msdos_inode_info *i = MSDOS_I(inode); struct fat_cache *cache; while (!list_empty(&i->cache_lru)) { cache = list_entry(i->cache_lru.next, struct fat_cache, cache_list); list_del_init(&cache->cache_list); i->nr_caches--; fat_cache_free(cache); } /* Update. The copy of caches before this id is discarded. */ i->cache_valid_id++; if (i->cache_valid_id == FAT_CACHE_VALID) i->cache_valid_id++; } void fat_cache_inval_inode(struct inode *inode) { spin_lock(&MSDOS_I(inode)->cache_lru_lock); __fat_cache_inval_inode(inode); spin_unlock(&MSDOS_I(inode)->cache_lru_lock); } static inline int cache_contiguous(struct fat_cache_id *cid, int dclus) { cid->nr_contig++; return ((cid->dcluster + cid->nr_contig) == dclus); } static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus) { cid->id = FAT_CACHE_VALID; cid->fcluster = fclus; cid->dcluster = dclus; cid->nr_contig = 0; } int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus) { struct super_block *sb = inode->i_sb; const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->cluster_bits; struct fat_entry fatent; struct fat_cache_id cid; int nr; BUG_ON(MSDOS_I(inode)->i_start == 0); *fclus = 0; *dclus = MSDOS_I(inode)->i_start; if (cluster == 0) return 0; if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) { /* * dummy, always not contiguous * This is reinitialized by cache_init(), later. */ cache_init(&cid, -1, -1); } fatent_init(&fatent); while (*fclus < cluster) { /* prevent the infinite loop of cluster chain */ if (*fclus > limit) { fat_fs_panic(sb, "%s: detected the cluster chain loop" " (i_pos %lld)", __FUNCTION__, MSDOS_I(inode)->i_pos); nr = -EIO; goto out; } nr = fat_ent_read(inode, &fatent, *dclus); if (nr < 0) goto out; else if (nr == FAT_ENT_FREE) { fat_fs_panic(sb, "%s: invalid cluster chain" " (i_pos %lld)", __FUNCTION__, MSDOS_I(inode)->i_pos); nr = -EIO; goto out; } else if (nr == FAT_ENT_EOF) { fat_cache_add(inode, &cid); goto out; } (*fclus)++; *dclus = nr; if (!cache_contiguous(&cid, *dclus)) cache_init(&cid, *fclus, *dclus); } nr = 0; fat_cache_add(inode, &cid); out: fatent_brelse(&fatent); return nr; } static int fat_bmap_cluster(struct inode *inode, int cluster) { struct super_block *sb = inode->i_sb; int ret, fclus, dclus; if (MSDOS_I(inode)->i_start == 0) return 0; ret = fat_get_cluster(inode, cluster, &fclus, &dclus); if (ret < 0) return ret; else if (ret == FAT_ENT_EOF) { fat_fs_panic(sb, "%s: request beyond EOF (i_pos %lld)", __FUNCTION__, MSDOS_I(inode)->i_pos); return -EIO; } return dclus; } int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys, unsigned long *mapped_blocks) { struct super_block *sb = inode->i_sb; struct msdos_sb_info *sbi = MSDOS_SB(sb); sector_t last_block; int cluster, offset; *phys = 0; *mapped_blocks = 0; if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) { if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) { *phys = sector + sbi->dir_start; *mapped_blocks = 1; } return 0; } last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1)) >> sb->s_blocksize_bits; if (sector >= last_block) return 0; cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits); offset = sector & (sbi->sec_per_clus - 1); cluster = fat_bmap_cluster(inode, cluster); if (cluster < 0) return cluster; else if (cluster) { *phys = fat_clus_to_blknr(sbi, cluster) + offset; *mapped_blocks = sbi->sec_per_clus - offset; if (*mapped_blocks > last_block - sector) *mapped_blocks = last_block - sector; } return 0; }