btrfs_fiemap_entry
struct btrfs_fiemap_entry *entry;
struct btrfs_fiemap_entry *entries;
cache.entries_size = PAGE_SIZE / sizeof(struct btrfs_fiemap_entry);
cache.entries = kmalloc_objs(struct btrfs_fiemap_entry,
struct btrfs_fiemap_entry *entry = &cache->entries[i];