#include <linux/msdos_fs.h>
#include <linux/buffer_head.h>
+#if 0
+#define debug_pr(fmt, args...) printk(fmt, ##args)
+#else
+#define debug_pr(fmt, args...)
+#endif
+
+/* 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. */
+};
+
+static inline int fat_max_cache(struct inode *inode)
+{
+ return FAT_MAX_CACHE;
+}
+
+static kmem_cache_t *fat_cache_cachep;
+
+static void init_once(void *foo, kmem_cache_t *cachep, unsigned long flags)
+{
+ struct fat_cache *cache = (struct fat_cache *)foo;
+
+ if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
+ SLAB_CTOR_CONSTRUCTOR)
+ 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,
+ init_once, NULL);
+ if (fat_cache_cachep == NULL)
+ return -ENOMEM;
+ return 0;
+}
+
+void __exit fat_cache_destroy(void)
+{
+ if (kmem_cache_destroy(fat_cache_cachep))
+ printk(KERN_INFO "fat_cache: not all structures were freed\n");
+}
+
+static inline struct fat_cache *fat_cache_alloc(struct inode *inode)
+{
+ return kmem_cache_alloc(fat_cache_cachep, SLAB_KERNEL);
+}
+
+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 *cache,
+ int *cached_fclus, int *cached_dclus)
+{
+ static struct fat_cache nohit = { .fcluster = 0, };
+
+ struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+ struct fat_cache *hit = &nohit, *p;
+ int offset = -1;
+
+ spin_lock(&sbi->cache_lock);
+ debug_pr("FAT: %s, fclus %d", __FUNCTION__, fclus);
+ list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
+ if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
+ hit = p;
+ debug_pr(", fclus %d, dclus %d, cont %d",
+ p->fcluster, p->dcluster, p->nr_contig);
+ if ((hit->fcluster + hit->nr_contig) < fclus) {
+ offset = hit->nr_contig;
+ debug_pr(" (off %d, hit)", offset);
+ } else {
+ offset = fclus - hit->fcluster;
+ debug_pr(" (off %d, full hit)", offset);
+ break;
+ }
+ }
+ }
+ if (hit != &nohit) {
+ fat_cache_update_lru(inode, hit);
+ *cache = *hit;
+ *cached_fclus = cache->fcluster + offset;
+ *cached_dclus = cache->dcluster + offset;
+ }
+ debug_pr("\n");
+ spin_unlock(&sbi->cache_lock);
+
+ return offset;
+}
+
+static struct fat_cache *fat_cache_merge(struct inode *inode,
+ struct fat_cache *new)
+{
+ struct fat_cache *p, *hit = NULL;
+
+ list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
+ if (p->fcluster == new->fcluster) {
+ BUG_ON(p->dcluster != new->dcluster);
+ debug_pr("FAT: %s: merged fclus %d, dclus %d, "
+ "cur cont %d => new cont %d\n", __FUNCTION__,
+ p->fcluster, p->dcluster, p->nr_contig,
+ new->nr_contig);
+ if (new->nr_contig > p->nr_contig)
+ p->nr_contig = new->nr_contig;
+ hit = p;
+ break;
+ }
+ }
+ return hit;
+}
+
+static void fat_cache_add(struct inode *inode, struct fat_cache *new)
+{
+ struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+ struct fat_cache *cache, *tmp;
+
+ debug_pr("FAT: %s: fclus %d, dclus %d, cont %d\n", __FUNCTION__,
+ new->fcluster, new->dcluster, new->nr_contig);
+
+ if (new->fcluster == -1) /* dummy cache */
+ return;
+
+ spin_lock(&sbi->cache_lock);
+ 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(&sbi->cache_lock);
+
+ tmp = fat_cache_alloc(inode);
+ spin_lock(&sbi->cache_lock);
+ cache = fat_cache_merge(inode, new);
+ if (cache != NULL) {
+ MSDOS_I(inode)->nr_caches--;
+ fat_cache_free(tmp);
+ goto out;
+ }
+ 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:
+ fat_cache_update_lru(inode, cache);
+
+ debug_pr("FAT: ");
+ list_for_each_entry(cache, &MSDOS_I(inode)->cache_lru, cache_list) {
+ debug_pr("(fclus %d, dclus %d, cont %d), ",
+ cache->fcluster, cache->dcluster, cache->nr_contig);
+ }
+ debug_pr("\n");
+ spin_unlock(&sbi->cache_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);
+ MSDOS_I(inode)->nr_caches--;
+ fat_cache_free(cache);
+ }
+ debug_pr("FAT: %s\n", __FUNCTION__);
+}
+
+void fat_cache_inval_inode(struct inode *inode)
+{
+ spin_lock(&MSDOS_SB(inode->i_sb)->cache_lock);
+ __fat_cache_inval_inode(inode);
+ spin_unlock(&MSDOS_SB(inode->i_sb)->cache_lock);
+}
+
int __fat_access(struct super_block *sb, int nr, int new_value)
{
struct msdos_sb_info *sbi = MSDOS_SB(sb);
return next;
}
-void fat_cache_init(struct super_block *sb)
+static inline int cache_contiguous(struct fat_cache *cache, int dclus)
{
- struct msdos_sb_info *sbi = MSDOS_SB(sb);
- int count;
-
- spin_lock_init(&sbi->cache_lock);
-
- for (count = 0; count < FAT_CACHE_NR - 1; count++) {
- sbi->cache_array[count].start_cluster = 0;
- sbi->cache_array[count].next = &sbi->cache_array[count + 1];
- }
- sbi->cache_array[count].start_cluster = 0;
- sbi->cache_array[count].next = NULL;
- sbi->cache = sbi->cache_array;
+ cache->nr_contig++;
+ return ((cache->dcluster + cache->nr_contig) == dclus);
}
-static void
-fat_cache_lookup(struct inode *inode, int cluster, int *f_clu, int *d_clu)
+static inline void cache_init(struct fat_cache *cache, int fclus, int dclus)
{
- struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
- struct fat_cache *walk;
- int first;
-
- BUG_ON(cluster == 0);
-
- first = MSDOS_I(inode)->i_start;
- if (!first)
- return;
-
- spin_lock(&sbi->cache_lock);
-
- if (MSDOS_I(inode)->disk_cluster &&
- MSDOS_I(inode)->file_cluster <= cluster) {
- *d_clu = MSDOS_I(inode)->disk_cluster;
- *f_clu = MSDOS_I(inode)->file_cluster;
- }
-
- for (walk = sbi->cache; walk; walk = walk->next) {
- if (walk->start_cluster == first
- && walk->file_cluster <= cluster
- && walk->file_cluster > *f_clu) {
- *d_clu = walk->disk_cluster;
- *f_clu = walk->file_cluster;
-#ifdef DEBUG
- printk("cache hit: %d (%d)\n", *f_clu, *d_clu);
-#endif
- if (*f_clu == cluster)
- goto out;
- }
- }
-#ifdef DEBUG
- printk("cache miss\n");
-#endif
-out:
- spin_unlock(&sbi->cache_lock);
-}
-
-#ifdef DEBUG
-static void list_cache(struct super_block *sb)
-{
- struct msdos_sb_info *sbi = MSDOS_SB(sb);
- struct fat_cache *walk;
-
- for (walk = sbi->cache; walk; walk = walk->next) {
- if (walk->start_cluster)
- printk("<%s,%d>(%d,%d) ", sb->s_id,
- walk->start_cluster, walk->file_cluster,
- walk->disk_cluster);
- else
- printk("-- ");
- }
- printk("\n");
-}
-#endif
-
-/*
- * 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 fat_cache *walk;
- int first = MSDOS_I(inode)->i_start;
- MSDOS_I(inode)->file_cluster = MSDOS_I(inode)->disk_cluster = 0;
- for (walk = MSDOS_SB(inode->i_sb)->cache; walk; walk = walk->next)
- if (walk->start_cluster == first)
- walk->start_cluster = 0;
-}
-
-void fat_cache_inval_inode(struct inode *inode)
-{
- struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
- spin_lock(&sbi->cache_lock);
- __fat_cache_inval_inode(inode);
- spin_unlock(&sbi->cache_lock);
-}
-
-void fat_cache_add(struct inode *inode, int f_clu, int d_clu)
-{
- struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
- struct fat_cache *walk, *last;
- int first, prev_f_clu, prev_d_clu;
-
- if (f_clu == 0)
- return;
- first = MSDOS_I(inode)->i_start;
- if (!first)
- return;
-
- last = NULL;
- spin_lock(&sbi->cache_lock);
-
- if (MSDOS_I(inode)->file_cluster == f_clu)
- goto out;
- else {
- prev_f_clu = MSDOS_I(inode)->file_cluster;
- prev_d_clu = MSDOS_I(inode)->disk_cluster;
- MSDOS_I(inode)->file_cluster = f_clu;
- MSDOS_I(inode)->disk_cluster = d_clu;
- if (prev_f_clu == 0)
- goto out;
- f_clu = prev_f_clu;
- d_clu = prev_d_clu;
- }
-
- for (walk = sbi->cache; walk->next; walk = (last = walk)->next) {
- if (walk->start_cluster == first &&
- walk->file_cluster == f_clu) {
- if (walk->disk_cluster != d_clu) {
- printk(KERN_ERR "FAT: cache corruption "
- "(i_pos %lld)\n", MSDOS_I(inode)->i_pos);
- __fat_cache_inval_inode(inode);
- goto out;
- }
- if (last == NULL)
- goto out;
-
- /* update LRU */
- last->next = walk->next;
- walk->next = sbi->cache;
- sbi->cache = walk;
-#ifdef DEBUG
- list_cache();
-#endif
- goto out;
- }
- }
- walk->start_cluster = first;
- walk->file_cluster = f_clu;
- walk->disk_cluster = d_clu;
- last->next = NULL;
- walk->next = sbi->cache;
- sbi->cache = walk;
-#ifdef DEBUG
- list_cache();
-#endif
-out:
- spin_unlock(&sbi->cache_lock);
+ cache->fcluster = fclus;
+ cache->dcluster = dclus;
+ cache->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_cache cache;
int nr;
BUG_ON(MSDOS_I(inode)->i_start == 0);
if (cluster == 0)
return 0;
- fat_cache_lookup(inode, cluster, fclus, dclus);
+ if (fat_cache_lookup(inode, cluster, &cache, fclus, dclus) < 0)
+ cache_init(&cache, -1, -1); /* dummy, always not contiguous */
+
while (*fclus < cluster) {
/* prevent the infinite loop of cluster chain */
if (*fclus > limit) {
MSDOS_I(inode)->i_pos);
return -EIO;
} else if (nr == FAT_ENT_EOF) {
- fat_cache_add(inode, *fclus, *dclus);
+ fat_cache_add(inode, &cache);
return FAT_ENT_EOF;
}
(*fclus)++;
*dclus = nr;
+ if (!cache_contiguous(&cache, *dclus))
+ cache_init(&cache, *fclus, *dclus);
}
- fat_cache_add(inode, *fclus, *dclus);
+ fat_cache_add(inode, &cache);
return 0;
}
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