lib/ext2fs/qcow2.h

   1 /*
   2  * qcow2.h --- structures and function prototypes for qcow2.c to generate
   3  * qcow2 formatted disk images.  This format is used originally by QEMU
   4  * for virtual machines, and stores the filesystem data on disk in a
   5  * packed format to avoid creating sparse image files that need lots of
   6  * seeking to read and write.
   7  *
   8  * The qcow2 format supports zlib compression, but that is not yet
   9  * implemented.
  10  *
  11  * It is possible to directly mount a qcow2 image using qemu-nbd:
  12  *
  13  * [root]# modprobe nbd max_part=63
  14  * [root]# qemu-nbd -c /dev/nbd0 image.img
  15  * [root]# mount /dev/nbd0p1 /mnt/qemu
  16  *
  17  * Format details at http://people.gnome.org/~markmc/qcow-image-format.html
  18  *
  19  * Copyright (C) 2010 Red Hat, Inc., Lukas Czerner <lczerner@redhat.com>
  20  *
  21  * %Begin-Header%
  22  * This file may be redistributed under the terms of the GNU Public
  23  * License.
  24  * %End-Header%
  25  */
  26
  27 /* Number of l2 tables in memory before writeback */
  28 #define L2_CACHE_PREALLOC       512
  29
  30
  31 #define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)
  32 #define QCOW_VERSION            2
  33 #define QCOW_OFLAG_COPIED       (1LL << 63)
  34 #define QCOW_OFLAG_COMPRESSED   (1LL << 62)
  35
  36 #define QCOW_COMPRESSED         1
  37 #define QCOW_ENCRYPTED          2
  38 #define QCOW_CORRUPTED          3
  39
  40 struct ext2_qcow2_hdr {
  41         __u32   magic;
  42         __u32   version;
  43
  44         __u64   backing_file_offset;
  45         __u32   backing_file_size;
  46
  47         __u32   cluster_bits;
  48         __u64   size;
  49         __u32   crypt_method;
  50
  51         __u32   l1_size;
  52         __u64   l1_table_offset;
  53
  54         __u64   refcount_table_offset;
  55         __u32   refcount_table_clusters;
  56
  57         __u32   nb_snapshots;
  58         __u64   snapshots_offset;
  59 };
  60
  61 typedef struct ext2_qcow2_l2_table L2_CACHE_HEAD;
  62
  63 struct ext2_qcow2_l2_table {
  64         __u32           l1_index;
  65         __u64           offset;
  66         __u64           *data;
  67         L2_CACHE_HEAD   *next;
  68 };
  69
  70 struct ext2_qcow2_l2_cache {
  71         L2_CACHE_HEAD   *used_head;
  72         L2_CACHE_HEAD   *used_tail;
  73         L2_CACHE_HEAD   *free_head;
  74         __u32           free;
  75         __u32           count;
  76         __u64           next_offset;
  77 };
  78
  79 struct ext2_qcow2_refcount {
  80         __u64   *refcount_table;
  81         __u64   refcount_table_offset;
  82         __u64   refcount_block_offset;
  83
  84         __u32   refcount_table_clusters;
  85         __u32   refcount_table_index;
  86         __u32   refcount_block_index;
  87
  88         __u16   *refcount_block;
  89 };
  90
  91 struct ext2_qcow2_image {
  92         int     fd;
  93         struct  ext2_qcow2_hdr          *hdr;
  94         struct  ext2_qcow2_l2_cache     *l2_cache;
  95         struct  ext2_qcow2_refcount     refcount;
  96         __u32   cluster_size;
  97         __u32   cluster_bits;
  98         __u32   l1_size;
  99         __u32   l2_size;
 100
 101         __u64   *l1_table;
 102         __u64   l2_offset;
 103         __u64   l1_offset;
 104         __u64   image_size;
 105 };
 106
 107 /* Function prototypes */
 108
 109 /* qcow2.c */
 110
 111 /* Functions for converting qcow2 image into raw image */
 112 struct ext2_qcow2_hdr *qcow2_read_header(int);
 113 int qcow2_write_raw_image(int, int, struct ext2_qcow2_hdr *);
 114