--- /dev/null
+/*
+ * 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/slab.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) {
+ fat_fs_error_ratelimit(sb,
+ "%s: detected the cluster chain loop"
+ " (i_pos %lld)", __func__,
+ MSDOS_I(inode)->i_pos);
+ nr = -EIO;
+ goto out;
+ }
+
+ nr = fat_ent_read(inode, &fatent, *dclus);
+ if (nr < 0)
+ goto out;
+ else if (nr == FAT_ENT_FREE) {
+ fat_fs_error_ratelimit(sb,
+ "%s: invalid cluster chain (i_pos %lld)",
+ __func__,
+ MSDOS_I(inode)->i_pos);
+ nr = -EIO;
+ goto out;
+ } else if (nr == FAT_ENT_EOF) {
+ fat_cache_add(inode, &cid);
+ goto out;
+ }
+ (*fclus)++;
+ *dclus = nr;
+ if (!cache_contiguous(&cid, *dclus))
+ cache_init(&cid, *fclus, *dclus);
+ }
+ nr = 0;
+ fat_cache_add(inode, &cid);
+out:
+ fatent_brelse(&fatent);
+ return nr;
+}
+
+static int fat_bmap_cluster(struct inode *inode, int cluster)
+{
+ struct super_block *sb = inode->i_sb;
+ int ret, fclus, dclus;
+
+ if (MSDOS_I(inode)->i_start == 0)
+ return 0;
+
+ ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
+ if (ret < 0)
+ return ret;
+ else if (ret == FAT_ENT_EOF) {
+ fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)",
+ __func__, MSDOS_I(inode)->i_pos);
+ return -EIO;
+ }
+ return dclus;
+}
+
+int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
+ unsigned long *mapped_blocks, int create)
+{
+ struct super_block *sb = inode->i_sb;
+ struct msdos_sb_info *sbi = MSDOS_SB(sb);
+ const unsigned long blocksize = sb->s_blocksize;
+ const unsigned char blocksize_bits = sb->s_blocksize_bits;
+ sector_t last_block;
+ int cluster, offset;
+
+ *phys = 0;
+ *mapped_blocks = 0;
+ if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) {
+ if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
+ *phys = sector + sbi->dir_start;
+ *mapped_blocks = 1;
+ }
+ return 0;
+ }
+
+ last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
+ if (sector >= last_block) {
+ if (!create)
+ return 0;
+
+ /*
+ * ->mmu_private can access on only allocation path.
+ * (caller must hold ->i_mutex)
+ */
+ last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
+ >> blocksize_bits;
+ if (sector >= last_block)
+ return 0;
+ }
+
+ cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
+ offset = sector & (sbi->sec_per_clus - 1);
+ cluster = fat_bmap_cluster(inode, cluster);
+ if (cluster < 0)
+ return cluster;
+ else if (cluster) {
+ *phys = fat_clus_to_blknr(sbi, cluster) + offset;
+ *mapped_blocks = sbi->sec_per_clus - offset;
+ if (*mapped_blocks > last_block - sector)
+ *mapped_blocks = last_block - sector;
+ }
+ return 0;
+}
Code Review / kvmfornfv.git / blobdiff