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386 lines
9.4 KiB
386 lines
9.4 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* linux/fs/fat/cache.c |
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* |
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* Written 1992,1993 by Werner Almesberger |
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* |
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* Mar 1999. AV. Changed cache, so that it uses the starting cluster instead |
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* of inode number. |
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* May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers. |
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*/ |
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#include <linux/slab.h> |
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#include "fat.h" |
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/* this must be > 0. */ |
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#define FAT_MAX_CACHE 8 |
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struct fat_cache { |
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struct list_head cache_list; |
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int nr_contig; /* number of contiguous clusters */ |
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int fcluster; /* cluster number in the file. */ |
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int dcluster; /* cluster number on disk. */ |
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}; |
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struct fat_cache_id { |
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unsigned int id; |
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int nr_contig; |
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int fcluster; |
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int dcluster; |
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}; |
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static inline int fat_max_cache(struct inode *inode) |
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{ |
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return FAT_MAX_CACHE; |
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} |
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static struct kmem_cache *fat_cache_cachep; |
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static void init_once(void *foo) |
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{ |
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struct fat_cache *cache = (struct fat_cache *)foo; |
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INIT_LIST_HEAD(&cache->cache_list); |
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} |
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int __init fat_cache_init(void) |
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{ |
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fat_cache_cachep = kmem_cache_create("fat_cache", |
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sizeof(struct fat_cache), |
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0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, |
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init_once); |
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if (fat_cache_cachep == NULL) |
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return -ENOMEM; |
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return 0; |
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} |
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void fat_cache_destroy(void) |
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{ |
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kmem_cache_destroy(fat_cache_cachep); |
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} |
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static inline struct fat_cache *fat_cache_alloc(struct inode *inode) |
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{ |
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return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS); |
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} |
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static inline void fat_cache_free(struct fat_cache *cache) |
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{ |
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BUG_ON(!list_empty(&cache->cache_list)); |
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kmem_cache_free(fat_cache_cachep, cache); |
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} |
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static inline void fat_cache_update_lru(struct inode *inode, |
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struct fat_cache *cache) |
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{ |
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if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list) |
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list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru); |
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} |
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static int fat_cache_lookup(struct inode *inode, int fclus, |
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struct fat_cache_id *cid, |
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int *cached_fclus, int *cached_dclus) |
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{ |
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static struct fat_cache nohit = { .fcluster = 0, }; |
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struct fat_cache *hit = &nohit, *p; |
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int offset = -1; |
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spin_lock(&MSDOS_I(inode)->cache_lru_lock); |
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list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) { |
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/* Find the cache of "fclus" or nearest cache. */ |
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if (p->fcluster <= fclus && hit->fcluster < p->fcluster) { |
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hit = p; |
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if ((hit->fcluster + hit->nr_contig) < fclus) { |
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offset = hit->nr_contig; |
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} else { |
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offset = fclus - hit->fcluster; |
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break; |
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} |
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} |
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} |
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if (hit != &nohit) { |
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fat_cache_update_lru(inode, hit); |
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cid->id = MSDOS_I(inode)->cache_valid_id; |
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cid->nr_contig = hit->nr_contig; |
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cid->fcluster = hit->fcluster; |
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cid->dcluster = hit->dcluster; |
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*cached_fclus = cid->fcluster + offset; |
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*cached_dclus = cid->dcluster + offset; |
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} |
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spin_unlock(&MSDOS_I(inode)->cache_lru_lock); |
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return offset; |
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} |
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static struct fat_cache *fat_cache_merge(struct inode *inode, |
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struct fat_cache_id *new) |
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{ |
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struct fat_cache *p; |
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list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) { |
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/* Find the same part as "new" in cluster-chain. */ |
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if (p->fcluster == new->fcluster) { |
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BUG_ON(p->dcluster != new->dcluster); |
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if (new->nr_contig > p->nr_contig) |
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p->nr_contig = new->nr_contig; |
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return p; |
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} |
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} |
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return NULL; |
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} |
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static void fat_cache_add(struct inode *inode, struct fat_cache_id *new) |
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{ |
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struct fat_cache *cache, *tmp; |
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if (new->fcluster == -1) /* dummy cache */ |
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return; |
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spin_lock(&MSDOS_I(inode)->cache_lru_lock); |
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if (new->id != FAT_CACHE_VALID && |
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new->id != MSDOS_I(inode)->cache_valid_id) |
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goto out; /* this cache was invalidated */ |
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cache = fat_cache_merge(inode, new); |
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if (cache == NULL) { |
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if (MSDOS_I(inode)->nr_caches < fat_max_cache(inode)) { |
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MSDOS_I(inode)->nr_caches++; |
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spin_unlock(&MSDOS_I(inode)->cache_lru_lock); |
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tmp = fat_cache_alloc(inode); |
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if (!tmp) { |
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spin_lock(&MSDOS_I(inode)->cache_lru_lock); |
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MSDOS_I(inode)->nr_caches--; |
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spin_unlock(&MSDOS_I(inode)->cache_lru_lock); |
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return; |
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} |
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spin_lock(&MSDOS_I(inode)->cache_lru_lock); |
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cache = fat_cache_merge(inode, new); |
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if (cache != NULL) { |
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MSDOS_I(inode)->nr_caches--; |
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fat_cache_free(tmp); |
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goto out_update_lru; |
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} |
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cache = tmp; |
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} else { |
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struct list_head *p = MSDOS_I(inode)->cache_lru.prev; |
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cache = list_entry(p, struct fat_cache, cache_list); |
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} |
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cache->fcluster = new->fcluster; |
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cache->dcluster = new->dcluster; |
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cache->nr_contig = new->nr_contig; |
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} |
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out_update_lru: |
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fat_cache_update_lru(inode, cache); |
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out: |
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spin_unlock(&MSDOS_I(inode)->cache_lru_lock); |
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} |
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/* |
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* Cache invalidation occurs rarely, thus the LRU chain is not updated. It |
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* fixes itself after a while. |
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*/ |
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static void __fat_cache_inval_inode(struct inode *inode) |
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{ |
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struct msdos_inode_info *i = MSDOS_I(inode); |
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struct fat_cache *cache; |
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while (!list_empty(&i->cache_lru)) { |
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cache = list_entry(i->cache_lru.next, |
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struct fat_cache, cache_list); |
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list_del_init(&cache->cache_list); |
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i->nr_caches--; |
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fat_cache_free(cache); |
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} |
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/* Update. The copy of caches before this id is discarded. */ |
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i->cache_valid_id++; |
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if (i->cache_valid_id == FAT_CACHE_VALID) |
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i->cache_valid_id++; |
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} |
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void fat_cache_inval_inode(struct inode *inode) |
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{ |
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spin_lock(&MSDOS_I(inode)->cache_lru_lock); |
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__fat_cache_inval_inode(inode); |
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spin_unlock(&MSDOS_I(inode)->cache_lru_lock); |
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} |
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static inline int cache_contiguous(struct fat_cache_id *cid, int dclus) |
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{ |
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cid->nr_contig++; |
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return ((cid->dcluster + cid->nr_contig) == dclus); |
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} |
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static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus) |
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{ |
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cid->id = FAT_CACHE_VALID; |
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cid->fcluster = fclus; |
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cid->dcluster = dclus; |
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cid->nr_contig = 0; |
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} |
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int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus) |
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{ |
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struct super_block *sb = inode->i_sb; |
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struct msdos_sb_info *sbi = MSDOS_SB(sb); |
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const int limit = sb->s_maxbytes >> sbi->cluster_bits; |
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struct fat_entry fatent; |
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struct fat_cache_id cid; |
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int nr; |
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BUG_ON(MSDOS_I(inode)->i_start == 0); |
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*fclus = 0; |
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*dclus = MSDOS_I(inode)->i_start; |
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if (!fat_valid_entry(sbi, *dclus)) { |
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fat_fs_error_ratelimit(sb, |
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"%s: invalid start cluster (i_pos %lld, start %08x)", |
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__func__, MSDOS_I(inode)->i_pos, *dclus); |
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return -EIO; |
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} |
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if (cluster == 0) |
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return 0; |
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if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) { |
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/* |
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* dummy, always not contiguous |
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* This is reinitialized by cache_init(), later. |
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*/ |
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cache_init(&cid, -1, -1); |
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} |
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fatent_init(&fatent); |
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while (*fclus < cluster) { |
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/* prevent the infinite loop of cluster chain */ |
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if (*fclus > limit) { |
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fat_fs_error_ratelimit(sb, |
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"%s: detected the cluster chain loop (i_pos %lld)", |
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__func__, MSDOS_I(inode)->i_pos); |
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nr = -EIO; |
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goto out; |
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} |
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nr = fat_ent_read(inode, &fatent, *dclus); |
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if (nr < 0) |
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goto out; |
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else if (nr == FAT_ENT_FREE) { |
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fat_fs_error_ratelimit(sb, |
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"%s: invalid cluster chain (i_pos %lld)", |
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__func__, MSDOS_I(inode)->i_pos); |
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nr = -EIO; |
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goto out; |
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} else if (nr == FAT_ENT_EOF) { |
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fat_cache_add(inode, &cid); |
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goto out; |
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} |
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(*fclus)++; |
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*dclus = nr; |
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if (!cache_contiguous(&cid, *dclus)) |
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cache_init(&cid, *fclus, *dclus); |
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} |
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nr = 0; |
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fat_cache_add(inode, &cid); |
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out: |
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fatent_brelse(&fatent); |
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return nr; |
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} |
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static int fat_bmap_cluster(struct inode *inode, int cluster) |
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{ |
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struct super_block *sb = inode->i_sb; |
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int ret, fclus, dclus; |
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if (MSDOS_I(inode)->i_start == 0) |
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return 0; |
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ret = fat_get_cluster(inode, cluster, &fclus, &dclus); |
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if (ret < 0) |
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return ret; |
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else if (ret == FAT_ENT_EOF) { |
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fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)", |
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__func__, MSDOS_I(inode)->i_pos); |
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return -EIO; |
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} |
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return dclus; |
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} |
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int fat_get_mapped_cluster(struct inode *inode, sector_t sector, |
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sector_t last_block, |
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unsigned long *mapped_blocks, sector_t *bmap) |
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{ |
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struct super_block *sb = inode->i_sb; |
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struct msdos_sb_info *sbi = MSDOS_SB(sb); |
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int cluster, offset; |
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cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits); |
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offset = sector & (sbi->sec_per_clus - 1); |
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cluster = fat_bmap_cluster(inode, cluster); |
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if (cluster < 0) |
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return cluster; |
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else if (cluster) { |
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*bmap = fat_clus_to_blknr(sbi, cluster) + offset; |
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*mapped_blocks = sbi->sec_per_clus - offset; |
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if (*mapped_blocks > last_block - sector) |
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*mapped_blocks = last_block - sector; |
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} |
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return 0; |
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} |
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static int is_exceed_eof(struct inode *inode, sector_t sector, |
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sector_t *last_block, int create) |
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{ |
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struct super_block *sb = inode->i_sb; |
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const unsigned long blocksize = sb->s_blocksize; |
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const unsigned char blocksize_bits = sb->s_blocksize_bits; |
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*last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits; |
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if (sector >= *last_block) { |
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if (!create) |
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return 1; |
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/* |
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* ->mmu_private can access on only allocation path. |
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* (caller must hold ->i_mutex) |
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*/ |
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*last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1)) |
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>> blocksize_bits; |
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if (sector >= *last_block) |
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return 1; |
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} |
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return 0; |
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} |
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int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys, |
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unsigned long *mapped_blocks, int create, bool from_bmap) |
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{ |
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struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb); |
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sector_t last_block; |
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*phys = 0; |
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*mapped_blocks = 0; |
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if (!is_fat32(sbi) && (inode->i_ino == MSDOS_ROOT_INO)) { |
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if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) { |
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*phys = sector + sbi->dir_start; |
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*mapped_blocks = 1; |
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} |
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return 0; |
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} |
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if (!from_bmap) { |
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if (is_exceed_eof(inode, sector, &last_block, create)) |
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return 0; |
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} else { |
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last_block = inode->i_blocks >> |
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(inode->i_sb->s_blocksize_bits - 9); |
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if (sector >= last_block) |
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return 0; |
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} |
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return fat_get_mapped_cluster(inode, sector, last_block, mapped_blocks, |
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phys); |
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}
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