502 lines
12 KiB
C
502 lines
12 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 kmem_cache_t *fat_cache_cachep;
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static void init_once(void *foo, kmem_cache_t *cachep, unsigned long flags)
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{
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struct fat_cache *cache = (struct fat_cache *)foo;
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if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
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SLAB_CTOR_CONSTRUCTOR)
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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,
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init_once, NULL);
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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 __exit fat_cache_destroy(void)
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{
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if (kmem_cache_destroy(fat_cache_cachep))
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printk(KERN_INFO "fat_cache: not all structures were freed\n");
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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, SLAB_KERNEL);
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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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int __fat_access(struct super_block *sb, int nr, int new_value)
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{
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struct msdos_sb_info *sbi = MSDOS_SB(sb);
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struct buffer_head *bh, *bh2, *c_bh, *c_bh2;
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unsigned char *p_first, *p_last;
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int copy, first, last, next, b;
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if (sbi->fat_bits == 32) {
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first = last = nr*4;
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} else if (sbi->fat_bits == 16) {
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first = last = nr*2;
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} else {
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first = nr*3/2;
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last = first+1;
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}
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b = sbi->fat_start + (first >> sb->s_blocksize_bits);
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if (!(bh = sb_bread(sb, b))) {
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printk(KERN_ERR "FAT: bread(block %d) in"
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" fat_access failed\n", b);
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return -EIO;
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}
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if ((first >> sb->s_blocksize_bits) == (last >> sb->s_blocksize_bits)) {
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bh2 = bh;
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} else {
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if (!(bh2 = sb_bread(sb, b + 1))) {
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brelse(bh);
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printk(KERN_ERR "FAT: bread(block %d) in"
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" fat_access failed\n", b + 1);
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return -EIO;
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}
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}
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if (sbi->fat_bits == 32) {
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p_first = p_last = NULL; /* GCC needs that stuff */
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next = le32_to_cpu(((__le32 *) bh->b_data)[(first &
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(sb->s_blocksize - 1)) >> 2]);
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/* Fscking Microsoft marketing department. Their "32" is 28. */
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next &= 0x0fffffff;
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} else if (sbi->fat_bits == 16) {
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p_first = p_last = NULL; /* GCC needs that stuff */
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next = le16_to_cpu(((__le16 *) bh->b_data)[(first &
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(sb->s_blocksize - 1)) >> 1]);
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} else {
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p_first = &((__u8 *)bh->b_data)[first & (sb->s_blocksize - 1)];
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p_last = &((__u8 *)bh2->b_data)[(first + 1) & (sb->s_blocksize - 1)];
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if (nr & 1)
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next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
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else
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next = (*p_first+(*p_last << 8)) & 0xfff;
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}
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if (new_value != -1) {
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if (sbi->fat_bits == 32) {
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((__le32 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 2]
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= cpu_to_le32(new_value);
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} else if (sbi->fat_bits == 16) {
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((__le16 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 1]
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= cpu_to_le16(new_value);
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} else {
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if (nr & 1) {
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*p_first = (*p_first & 0xf) | (new_value << 4);
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*p_last = new_value >> 4;
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}
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else {
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*p_first = new_value & 0xff;
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*p_last = (*p_last & 0xf0) | (new_value >> 8);
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}
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mark_buffer_dirty(bh2);
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}
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mark_buffer_dirty(bh);
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for (copy = 1; copy < sbi->fats; copy++) {
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b = sbi->fat_start + (first >> sb->s_blocksize_bits)
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+ sbi->fat_length * copy;
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if (!(c_bh = sb_bread(sb, b)))
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break;
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if (bh != bh2) {
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if (!(c_bh2 = sb_bread(sb, b+1))) {
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brelse(c_bh);
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break;
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}
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memcpy(c_bh2->b_data, bh2->b_data, sb->s_blocksize);
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mark_buffer_dirty(c_bh2);
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brelse(c_bh2);
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}
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memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
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mark_buffer_dirty(c_bh);
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brelse(c_bh);
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}
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}
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brelse(bh);
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if (bh != bh2)
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brelse(bh2);
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return next;
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}
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/*
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* Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
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* new_value is != -1, that FAT entry is replaced by it.
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*/
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int fat_access(struct super_block *sb, int nr, int new_value)
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{
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int next;
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next = -EIO;
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if (nr < 2 || MSDOS_SB(sb)->clusters + 2 <= nr) {
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fat_fs_panic(sb, "invalid access to FAT (entry 0x%08x)", nr);
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goto out;
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}
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if (new_value == FAT_ENT_EOF)
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new_value = EOF_FAT(sb);
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next = __fat_access(sb, nr, new_value);
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if (next < 0)
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goto out;
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if (next >= BAD_FAT(sb))
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next = FAT_ENT_EOF;
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out:
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return next;
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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_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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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)", __FUNCTION__,
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MSDOS_I(inode)->i_pos);
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return -EIO;
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}
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nr = fat_access(sb, *dclus, -1);
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if (nr < 0)
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return nr;
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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)", __FUNCTION__,
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MSDOS_I(inode)->i_pos);
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return -EIO;
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} else if (nr == FAT_ENT_EOF) {
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fat_cache_add(inode, &cid);
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return FAT_ENT_EOF;
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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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fat_cache_add(inode, &cid);
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return 0;
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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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__FUNCTION__, 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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{
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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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if ((sbi->fat_bits != 32) &&
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(inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
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!MSDOS_I(inode)->i_start))) {
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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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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 = ((sector_t)cluster - 2) * sbi->sec_per_clus
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+ sbi->data_start + offset;
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}
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return 0;
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}
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/* Free all clusters after the skip'th cluster. */
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int fat_free(struct inode *inode, int skip)
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{
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struct super_block *sb = inode->i_sb;
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int nr, ret, fclus, dclus;
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if (MSDOS_I(inode)->i_start == 0)
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return 0;
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if (skip) {
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ret = fat_get_cluster(inode, skip - 1, &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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return 0;
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nr = fat_access(sb, dclus, -1);
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if (nr == FAT_ENT_EOF)
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return 0;
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else if (nr > 0) {
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/*
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* write a new EOF, and get the remaining cluster
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* chain for freeing.
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*/
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nr = fat_access(sb, dclus, FAT_ENT_EOF);
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}
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if (nr < 0)
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return nr;
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fat_cache_inval_inode(inode);
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} else {
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fat_cache_inval_inode(inode);
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nr = MSDOS_I(inode)->i_start;
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MSDOS_I(inode)->i_start = 0;
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MSDOS_I(inode)->i_logstart = 0;
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mark_inode_dirty(inode);
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}
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lock_fat(sb);
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do {
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nr = fat_access(sb, nr, FAT_ENT_FREE);
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if (nr < 0)
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goto error;
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else if (nr == FAT_ENT_FREE) {
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fat_fs_panic(sb, "%s: deleting beyond EOF (i_pos %lld)",
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__FUNCTION__, MSDOS_I(inode)->i_pos);
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nr = -EIO;
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goto error;
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}
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if (MSDOS_SB(sb)->free_clusters != -1)
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MSDOS_SB(sb)->free_clusters++;
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inode->i_blocks -= MSDOS_SB(sb)->cluster_size >> 9;
|
|
} while (nr != FAT_ENT_EOF);
|
|
fat_clusters_flush(sb);
|
|
nr = 0;
|
|
error:
|
|
unlock_fat(sb);
|
|
|
|
return nr;
|
|
}
|