From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Wed, 5 Aug 2015 17:04:01 -0300 Subject: Initial import --- fs/fat/cache.c | 351 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 351 insertions(+) create mode 100644 fs/fat/cache.c (limited to 'fs/fat/cache.c') diff --git a/fs/fat/cache.c b/fs/fat/cache.c new file mode 100644 index 000000000..93fc62232 --- /dev/null +++ b/fs/fat/cache.c @@ -0,0 +1,351 @@ +/* + * 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 +#include "fat.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 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_NOFS); +} + +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); + if (!tmp) { + spin_lock(&MSDOS_I(inode)->cache_lru_lock); + MSDOS_I(inode)->nr_caches--; + spin_unlock(&MSDOS_I(inode)->cache_lru_lock); + return; + } + + 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_error_ratelimit(sb, + "%s: detected the cluster chain loop" + " (i_pos %lld)", __func__, + 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_error_ratelimit(sb, + "%s: invalid cluster chain (i_pos %lld)", + __func__, + 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_error(sb, "%s: request beyond EOF (i_pos %lld)", + __func__, 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, int create) +{ + struct super_block *sb = inode->i_sb; + struct msdos_sb_info *sbi = MSDOS_SB(sb); + const unsigned long blocksize = sb->s_blocksize; + const unsigned char blocksize_bits = sb->s_blocksize_bits; + 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 = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits; + if (sector >= last_block) { + if (!create) + return 0; + + /* + * ->mmu_private can access on only allocation path. + * (caller must hold ->i_mutex) + */ + last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1)) + >> 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; +} -- cgit v1.2.3-54-g00ecf