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/*
* linux/fs/fat/cache.c
*
* Written 1992,1993 by Werner Almesberger
*
* Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
* of inode number.
* May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
*/
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
#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) {
|