2 * qcow2.c --- Functions to generate qcow2 formatted disk images. This
3 * format is used originally by QEMU for virtual machines, and stores the
4 * filesystem data on disk in a packed format to avoid creating sparse
5 * image files that need lots of seeking to read and write.
7 * The qcow2 format supports zlib compression, but that is not yet
10 * It is possible to directly mount a qcow2 image using qemu-nbd:
12 * [root]# modprobe nbd max_part=63
13 * [root]# qemu-nbd -c /dev/nbd0 image.img
14 * [root]# mount /dev/nbd0p1 /mnt/qemu
16 * Format details at http://people.gnome.org/~markmc/qcow-image-format.html
18 * Copyright (C) 2010 Red Hat, Inc., Lukas Czerner <lczerner@redhat.com>
21 * This file may be redistributed under the terms of the GNU Public
26 #define _LARGEFILE_SOURCE
27 #define _LARGEFILE64_SOURCE
42 #include <sys/types.h>
45 #include "ext2fs/ext2fs.h"
48 /* Functions for converting qcow2 image into raw image */
50 struct ext2_qcow2_hdr *qcow2_read_header(int fd)
53 struct ext2_qcow2_hdr *hdr = NULL;
57 ret = ext2fs_get_mem(sizeof(struct ext2_qcow2_hdr), &buffer);
60 memset(buffer, 0, sizeof(struct ext2_qcow2_hdr));
62 if (ext2fs_llseek(fd, 0, SEEK_SET < 0))
65 size = read(fd, buffer, sizeof(struct ext2_qcow2_hdr));
66 if (size != sizeof(struct ext2_qcow2_hdr)) {
67 ext2fs_free_mem(&buffer);
71 hdr = (struct ext2_qcow2_hdr *)(buffer);
73 if ((ext2fs_be32_to_cpu(hdr->magic) != QCOW_MAGIC) ||
74 (ext2fs_be32_to_cpu(hdr->version) != 2)) {
75 ext2fs_free_mem(&hdr);
82 static int qcow2_read_l1_table(struct ext2_qcow2_image *img)
85 size_t size, l1_size = img->l1_size * sizeof(blk64_t);
89 ret = ext2fs_get_memzero(l1_size, &table);
93 if (ext2fs_llseek(fd, img->l1_offset, SEEK_SET) < 0)
96 size = read(fd, table, l1_size);
97 if (size != l1_size) {
98 ext2fs_free_mem(&table);
102 img->l1_table = table;
107 static int qcow2_read_l2_table(struct ext2_qcow2_image *img,
108 ext2_off64_t offset, blk64_t **l2_table)
115 if (ext2fs_llseek(fd, offset, SEEK_SET) < 0)
118 size = read(fd, *l2_table, img->cluster_size);
119 if (size != img->cluster_size)
125 static int qcow2_copy_data(int fdin, int fdout, ext2_off64_t off_in,
126 ext2_off64_t off_out, void *buf, size_t count)
132 if (ext2fs_llseek(fdout, off_out, SEEK_SET) < 0)
135 if (ext2fs_llseek(fdin, off_in, SEEK_SET) < 0)
138 size = read(fdin, buf, count);
142 size = write(fdout, buf, count);
150 int qcow2_write_raw_image(int qcow2_fd, int raw_fd,
151 struct ext2_qcow2_hdr *hdr)
153 struct ext2_qcow2_image img;
155 unsigned int l1_index, l2_index;
157 blk64_t *l1_table, *l2_table;
158 void *copy_buf = NULL;
161 if (hdr->crypt_method)
162 return -QCOW_ENCRYPTED;
168 img.cluster_bits = ext2fs_be32_to_cpu(hdr->cluster_bits);
169 img.cluster_size = 1 << img.cluster_bits;
170 img.l1_size = ext2fs_be32_to_cpu(hdr->l1_size);
171 img.l1_offset = ext2fs_be64_to_cpu(hdr->l1_table_offset);
172 img.l2_size = 1 << (img.cluster_bits - 3);
173 img.image_size = ext2fs_be64_to_cpu(hdr->size);
176 ret = ext2fs_get_memzero(img.cluster_size, &l2_table);
180 ret = ext2fs_get_memzero(1 << img.cluster_bits, ©_buf);
184 if (ext2fs_llseek(raw_fd, 0, SEEK_SET) < 0) {
189 ret = qcow2_read_l1_table(&img);
193 l1_table = img.l1_table;
194 /* Walk through l1 table */
195 for (l1_index = 0; l1_index < img.l1_size; l1_index++) {
196 ext2_off64_t off_out;
198 offset = ext2fs_be64_to_cpu(l1_table[l1_index]) &
201 if ((offset > img.image_size) ||
205 if (offset & QCOW_OFLAG_COMPRESSED) {
206 ret = -QCOW_COMPRESSED;
210 ret = qcow2_read_l2_table(&img, offset, &l2_table);
214 /* Walk through l2 table and copy data blocks into raw image */
215 for (l2_index = 0; l2_index < img.l2_size; l2_index++) {
216 offset = ext2fs_be64_to_cpu(l2_table[l2_index]) &
222 off_out = (l1_index * img.l2_size) +
224 off_out <<= img.cluster_bits;
225 ret = qcow2_copy_data(qcow2_fd, raw_fd, offset,
226 off_out, copy_buf, img.cluster_size);
232 /* Resize the output image to the filesystem size */
233 if (ext2fs_llseek(raw_fd, img.image_size - 1, SEEK_SET) < 0)
236 ((char *)copy_buf)[0] = 0;
237 size = write(raw_fd, copy_buf, 1);
243 ext2fs_free_mem(©_buf);
245 ext2fs_free_mem(&img.l1_table);
247 ext2fs_free_mem(&l2_table);