[PATCH] adds fat_get_cluster (7/11)

This adds fat_get_cluster() for generic reads of FAT cluster-chains, and
old fat_get_cluster() is renamed to fat_bmap_cluster().

diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index 96e6651cffa2c93cd459e3efad06db40d9203193..102738f6af82b2adf87cdda03bf87bfa4a81a428 100644 (file)
--- a/fs/fat/cache.c
+++ b/fs/fat/cache.c
@@ -287,7 +287,49 @@ out:
        spin_unlock(&sbi->cache_lock);
 }
 
-static int fat_get_cluster(struct inode *inode, int cluster)
+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;
+       int nr;
+
+       BUG_ON(MSDOS_I(inode)->i_start == 0);
+       
+       *fclus = 0;
+       *dclus = MSDOS_I(inode)->i_start;
+       if (cluster == 0)
+               return 0;
+
+       fat_cache_lookup(inode, cluster, fclus, dclus);
+       while (*fclus < cluster) {
+               /* prevent the infinite loop of cluster chain */
+               if (*fclus > limit) {
+                       fat_fs_panic(sb, "%s: detected the cluster chain loop"
+                                    " (i_pos %llu)", __FUNCTION__,
+                                    MSDOS_I(inode)->i_pos);
+                       return -EIO;
+               }
+
+               nr = fat_access(sb, *dclus, -1);
+               if (nr < 0)
+                       return nr;
+               else if (nr == FAT_ENT_FREE) {
+                       fat_fs_panic(sb, "%s: invalid cluster chain"
+                                    " (i_pos %llu)", __FUNCTION__,
+                                    MSDOS_I(inode)->i_pos);
+                       return -EIO;
+               } else if (nr == FAT_ENT_EOF) {
+                       fat_cache_add(inode, *fclus, *dclus);
+                       return FAT_ENT_EOF;
+               }
+               (*fclus)++;
+               *dclus = nr;
+       }
+       fat_cache_add(inode, *fclus, *dclus);
+       return 0;
+}
+
+static int fat_bmap_cluster(struct inode *inode, int cluster)
 {
        struct super_block *sb = inode->i_sb;
        int nr,count;
@@ -336,7 +378,7 @@ int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys)
 
        cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
        offset  = sector & (sbi->cluster_size - 1);
-       cluster = fat_get_cluster(inode, cluster);
+       cluster = fat_bmap_cluster(inode, cluster);
        if (cluster < 0)
                return cluster;
        else if (cluster) {

diff --git a/include/linux/msdos_fs.h b/include/linux/msdos_fs.h
index 1ce9ba2f57b04439236827408dc1fdebf6cce369..c9e534912cb9ec0f4fcafde631249f2b4068b8d3 100644 (file)
--- a/include/linux/msdos_fs.h
+++ b/include/linux/msdos_fs.h
@@ -237,6 +237,8 @@ extern void fat_cache_lookup(struct inode *inode, int cluster, int *f_clu,
                             int *d_clu);
 extern void fat_cache_add(struct inode *inode, int f_clu, int d_clu);
 extern void fat_cache_inval_inode(struct inode *inode);
+extern int fat_get_cluster(struct inode *inode, int cluster,
+                          int *fclus, int *dclus);
 extern int fat_free(struct inode *inode, int skip);
 
 /* fat/dir.c */