lib/ext2fs/qcow2.c

   1 /*
   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.
   6  *
   7  * The qcow2 format supports zlib compression, but that is not yet
   8  * implemented.
   9  *
  10  * It is possible to directly mount a qcow2 image using qemu-nbd:
  11  *
  12  * [root]# modprobe nbd max_part=63
  13  * [root]# qemu-nbd -c /dev/nbd0 image.img
  14  * [root]# mount /dev/nbd0p1 /mnt/qemu
  15  *
  16  * Format details at http://people.gnome.org/~markmc/qcow-image-format.html
  17  *
  18  * Copyright (C) 2010 Red Hat, Inc., Lukas Czerner <lczerner@redhat.com>
  19  *
  20  * %Begin-Header%
  21  * This file may be redistributed under the terms of the GNU Public
  22  * License.
  23  * %End-Header%
  24  */
  25
  26 #ifndef _LARGEFILE_SOURCE
  27 #define _LARGEFILE_SOURCE
  28 #endif
  29 #ifndef _LARGEFILE64_SOURCE
  30 #define _LARGEFILE64_SOURCE
  31 #endif
  32
  33 #include "config.h"
  34 #include <fcntl.h>
  35 #include <grp.h>
  36 #include <pwd.h>
  37 #include <stdio.h>
  38 #ifdef HAVE_STDLIB_H
  39 #include <stdlib.h>
  40 #endif
  41 #include <string.h>
  42 #include <time.h>
  43 #include <unistd.h>
  44 #include <fcntl.h>
  45 #include <errno.h>
  46 #include <sys/stat.h>
  47 #include <sys/types.h>
  48 #include <assert.h>
  49
  50 #include "ext2fs/ext2fs.h"
  51 #include "qcow2.h"
  52
  53 /* Functions for converting qcow2 image into raw image */
  54
  55 struct ext2_qcow2_hdr *qcow2_read_header(int fd)
  56 {
  57         void *buffer = NULL;
  58         struct ext2_qcow2_hdr *hdr = NULL;
  59         size_t size;
  60         errcode_t ret;
  61
  62         ret = ext2fs_get_mem(sizeof(struct ext2_qcow2_hdr), &buffer);
  63         if (ret)
  64                 return NULL;
  65         memset(buffer, 0, sizeof(struct ext2_qcow2_hdr));
  66
  67         if (ext2fs_llseek(fd, 0, SEEK_SET < 0)) {
  68                 ext2fs_free_mem(&buffer);
  69                 return NULL;
  70         }
  71
  72         size = read(fd, buffer, sizeof(struct ext2_qcow2_hdr));
  73         if (size != sizeof(struct ext2_qcow2_hdr)) {
  74                 ext2fs_free_mem(&buffer);
  75                 return NULL;
  76         }
  77
  78         hdr = (struct ext2_qcow2_hdr *)(buffer);
  79
  80         if ((ext2fs_be32_to_cpu(hdr->magic) != QCOW_MAGIC) ||
  81             (ext2fs_be32_to_cpu(hdr->version) != 2)) {
  82                 ext2fs_free_mem(&hdr);
  83                 return NULL;
  84         }
  85
  86         return hdr;
  87 }
  88
  89 static int qcow2_read_l1_table(struct ext2_qcow2_image *img)
  90 {
  91         int fd = img->fd;
  92         size_t size, l1_size = img->l1_size * sizeof(blk64_t);
  93         blk64_t *table;
  94         errcode_t ret;
  95
  96         ret = ext2fs_get_memzero(l1_size, &table);
  97         if (ret)
  98                 return ret;
  99
 100         if (ext2fs_llseek(fd, img->l1_offset, SEEK_SET) < 0) {
 101                 ext2fs_free_mem(&table);
 102                 return errno;
 103         }
 104
 105         size = read(fd, table, l1_size);
 106         if (size != l1_size) {
 107                 ext2fs_free_mem(&table);
 108                 return errno;
 109         }
 110
 111         img->l1_table = table;
 112
 113         return 0;
 114 }
 115
 116 static int qcow2_read_l2_table(struct ext2_qcow2_image *img,
 117                                ext2_off64_t offset, blk64_t **l2_table)
 118 {
 119         int fd = img->fd;
 120         size_t size;
 121
 122         assert(*l2_table);
 123
 124         if (ext2fs_llseek(fd, offset, SEEK_SET) < 0)
 125                 return errno;
 126
 127         size = read(fd, *l2_table, img->cluster_size);
 128         if (size != img->cluster_size)
 129                 return errno;
 130
 131         return 0;
 132 }
 133
 134 static int qcow2_copy_data(int fdin, int fdout, ext2_off64_t off_in,
 135                            ext2_off64_t off_out, void *buf, size_t count)
 136 {
 137         size_t size;
 138
 139         assert(buf);
 140
 141         if (ext2fs_llseek(fdout, off_out, SEEK_SET) < 0)
 142                 return errno;
 143
 144         if (ext2fs_llseek(fdin, off_in, SEEK_SET) < 0)
 145                 return errno;
 146
 147         size = read(fdin, buf, count);
 148         if (size != count)
 149                 return errno;
 150
 151         size = write(fdout, buf, count);
 152         if (size != count)
 153                 return errno;
 154
 155         return 0;
 156 }
 157
 158
 159 int qcow2_write_raw_image(int qcow2_fd, int raw_fd,
 160                               struct ext2_qcow2_hdr *hdr)
 161 {
 162         struct ext2_qcow2_image img;
 163         errcode_t ret = 0;
 164         unsigned int l1_index, l2_index;
 165         ext2_off64_t offset;
 166         blk64_t *l1_table, *l2_table = NULL;
 167         void *copy_buf = NULL;
 168         size_t size;
 169
 170         if (hdr->crypt_method)
 171                 return -QCOW_ENCRYPTED;
 172
 173         img.fd = qcow2_fd;
 174         img.hdr = hdr;
 175         img.l2_cache = NULL;
 176         img.l1_table = NULL;
 177         img.cluster_bits = ext2fs_be32_to_cpu(hdr->cluster_bits);
 178         img.cluster_size = 1 << img.cluster_bits;
 179         img.l1_size = ext2fs_be32_to_cpu(hdr->l1_size);
 180         img.l1_offset = ext2fs_be64_to_cpu(hdr->l1_table_offset);
 181         img.l2_size = 1 << (img.cluster_bits - 3);
 182         img.image_size = ext2fs_be64_to_cpu(hdr->size);
 183
 184
 185         ret = ext2fs_get_memzero(img.cluster_size, &l2_table);
 186         if (ret)
 187                 goto out;
 188
 189         ret = ext2fs_get_memzero(1 << img.cluster_bits, &copy_buf);
 190         if (ret)
 191                 goto out;
 192
 193         if (ext2fs_llseek(raw_fd, 0, SEEK_SET) < 0) {
 194                 ret = errno;
 195                 goto out;
 196         }
 197
 198         ret = qcow2_read_l1_table(&img);
 199         if (ret)
 200                 goto out;
 201
 202         l1_table = img.l1_table;
 203         /* Walk through l1 table */
 204         for (l1_index = 0; l1_index < img.l1_size; l1_index++) {
 205                 ext2_off64_t off_out;
 206
 207                 offset = ext2fs_be64_to_cpu(l1_table[l1_index]) &
 208                          ~QCOW_OFLAG_COPIED;
 209
 210                 if ((offset > img.image_size) ||
 211                     (offset <= 0))
 212                         continue;
 213
 214                 if (offset & QCOW_OFLAG_COMPRESSED) {
 215                         ret = -QCOW_COMPRESSED;
 216                         goto out;
 217                 }
 218
 219                 ret = qcow2_read_l2_table(&img, offset, &l2_table);
 220                 if (ret)
 221                         break;
 222
 223                 /* Walk through l2 table and copy data blocks into raw image */
 224                 for (l2_index = 0; l2_index < img.l2_size; l2_index++) {
 225                         offset = ext2fs_be64_to_cpu(l2_table[l2_index]) &
 226                                  ~QCOW_OFLAG_COPIED;
 227
 228                         if (offset == 0)
 229                                 continue;
 230
 231                         off_out = (l1_index * img.l2_size) +
 232                                   l2_index;
 233                         off_out <<= img.cluster_bits;
 234                         ret = qcow2_copy_data(qcow2_fd, raw_fd, offset,
 235                                         off_out, copy_buf, img.cluster_size);
 236                         if (ret)
 237                                 goto out;
 238                 }
 239         }
 240
 241         /* Resize the output image to the filesystem size */
 242         if (ext2fs_llseek(raw_fd, img.image_size - 1, SEEK_SET) < 0) {
 243                 ret = errno;
 244                 goto out;
 245         }
 246
 247         ((char *)copy_buf)[0] = 0;
 248         size = write(raw_fd, copy_buf, 1);
 249         if (size != 1) {
 250                 ret = errno;
 251                 goto out;
 252         }
 253
 254 out:
 255         if (copy_buf)
 256                 ext2fs_free_mem(&copy_buf);
 257         if (img.l1_table)
 258                 ext2fs_free_mem(&img.l1_table);
 259         if (l2_table)
 260                 ext2fs_free_mem(&l2_table);
 261         return ret;
 262 }