fat_ent_read
nr = fat_ent_read(inode, &fatent, *dclus);
extern int fat_ent_read(struct inode *inode, struct fat_entry *fatent,
cluster = fat_ent_read(inode, &fatent, cluster);
ret = fat_ent_read(inode, &fatent, dclus);
ret = fat_ent_read(inode, &fatent, last);