330 lines
8.0 KiB
C
330 lines
8.0 KiB
C
/*
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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/fs.h>
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#include <linux/msdos_fs.h>
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#include <linux/buffer_head.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(struct kmem_cache *cachep, 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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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, 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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const int limit = sb->s_maxbytes >> MSDOS_SB(sb)->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 (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_panic(sb, "%s: detected the cluster chain loop"
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" (i_pos %lld)", __func__,
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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_panic(sb, "%s: invalid cluster chain"
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" (i_pos %lld)", __func__,
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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_panic(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_bmap(struct inode *inode, sector_t sector, sector_t *phys,
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unsigned long *mapped_blocks)
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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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sector_t last_block;
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int cluster, offset;
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*phys = 0;
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*mapped_blocks = 0;
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if ((sbi->fat_bits != 32) && (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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last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
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>> sb->s_blocksize_bits;
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if (sector >= last_block)
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return 0;
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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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*phys = 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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