blob: 81e0ec932657f7c5c24437cc567b5b04985a9a19 [file] [log] [blame]
* qcow2.h --- structures and function prototypes for qcow2.c to generate
* qcow2 formatted disk images. This format is used originally by QEMU
* for virtual machines, and stores the filesystem data on disk in a
* packed format to avoid creating sparse image files that need lots of
* seeking to read and write.
* The qcow2 format supports zlib compression, but that is not yet
* implemented.
* It is possible to directly mount a qcow2 image using qemu-nbd:
* [root]# modprobe nbd max_part=63
* [root]# qemu-nbd -c /dev/nbd0 image.img
* [root]# mount /dev/nbd0p1 /mnt/qemu
* Format details at
* Copyright (C) 2010 Red Hat, Inc., Lukas Czerner <>
* %Begin-Header%
* This file may be redistributed under the terms of the GNU Public
* License.
* %End-Header%
/* Number of l2 tables in memory before writeback */
#define L2_CACHE_PREALLOC 512
#define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)
#define QCOW_VERSION 2
#define QCOW_OFLAG_COPIED (1LL << 63)
struct ext2_qcow2_hdr {
__u32 magic;
__u32 version;
__u64 backing_file_offset;
__u32 backing_file_size;
__u32 cluster_bits;
__u64 size;
__u32 crypt_method;
__u32 l1_size;
__u64 l1_table_offset;
__u64 refcount_table_offset;
__u32 refcount_table_clusters;
__u32 nb_snapshots;
__u64 snapshots_offset;
typedef struct ext2_qcow2_l2_table L2_CACHE_HEAD;
struct ext2_qcow2_l2_table {
__u32 l1_index;
__u64 offset;
__u64 *data;
L2_CACHE_HEAD *next;
struct ext2_qcow2_l2_cache {
L2_CACHE_HEAD *used_head;
L2_CACHE_HEAD *used_tail;
L2_CACHE_HEAD *free_head;
__u32 free;
__u32 count;
__u64 next_offset;
struct ext2_qcow2_refcount {
__u64 *refcount_table;
__u64 refcount_table_offset;
__u64 refcount_block_offset;
__u32 refcount_table_clusters;
__u32 refcount_table_index;
__u32 refcount_block_index;
__u16 *refcount_block;
struct ext2_qcow2_image {
int fd;
struct ext2_qcow2_hdr *hdr;
struct ext2_qcow2_l2_cache *l2_cache;
struct ext2_qcow2_refcount refcount;
__u32 cluster_size;
__u32 cluster_bits;
__u32 l1_size;
__u32 l2_size;
__u64 *l1_table;
__u64 l2_offset;
__u64 l1_offset;
__u64 image_size;
/* Function prototypes */
/* qcow2.c */
/* Functions for converting qcow2 image into raw image */
struct ext2_qcow2_hdr *qcow2_read_header(int);
int qcow2_write_raw_image(int, int, struct ext2_qcow2_hdr *);