qemu-mkcow.c

   1 /*
   2  * create a COW disk image
   3  *
   4  * Copyright (c) 2003 Fabrice Bellard
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24 #include <stdlib.h>
  25 #include <stdio.h>
  26 #include <stdarg.h>
  27 #include <string.h>
  28 #include <getopt.h>
  29 #include <inttypes.h>
  30 #include <unistd.h>
  31 #include <fcntl.h>
  32 #include <signal.h>
  33 #include <time.h>
  34 #include <sys/time.h>
  35 #include <errno.h>
  36 #include <sys/stat.h>
  37 #include <netinet/in.h>
  38
  39 #include "cow.h"
  40
  41 #include "bswap.h"
  42
  43 int cow_create(int cow_fd, const char *image_filename,
  44                int64_t image_sectors)
  45 {
  46     struct cow_header_v2 cow_header;
  47     int fd;
  48     struct stat st;
  49
  50     memset(&cow_header, 0, sizeof(cow_header));
  51     cow_header.magic = htonl(COW_MAGIC);
  52     cow_header.version = htonl(COW_VERSION);
  53     if (image_filename) {
  54         fd = open(image_filename, O_RDONLY);
  55         if (fd < 0) {
  56             perror(image_filename);
  57             exit(1);
  58         }
  59         image_sectors = lseek64(fd, 0, SEEK_END);
  60         if (fstat(fd, &st) != 0) {
  61             close(fd);
  62             return -1;
  63         }
  64         close(fd);
  65         image_sectors /= 512;
  66         cow_header.mtime = htonl(st.st_mtime);
  67         realpath(image_filename, cow_header.backing_file);
  68     }
  69     cow_header.sectorsize = htonl(512);
  70     cow_header.size = image_sectors * 512;
  71 #ifndef WORDS_BIGENDIAN
  72     cow_header.size = bswap64(cow_header.size);
  73 #endif
  74     write(cow_fd, &cow_header, sizeof(cow_header));
  75     /* resize to include at least all the bitmap */
  76     ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
  77     lseek(cow_fd, 0, SEEK_SET);
  78     return 0;
  79 }
  80
  81 void help(void)
  82 {
  83     printf("qemu-mkcow version " QEMU_VERSION ", Copyright (c) 2003 Fabrice Bellard\n"
  84            "usage: qemu-mkcow [-h] [-f disk_image] cow_image [cow_size]\n"
  85            "Create a Copy On Write disk image from an optional raw disk image\n"
  86            "\n"
  87            "-f disk_image   set the raw disk image name\n"
  88            "cow_image       the created cow_image\n"
  89            "cow_size        the create cow_image size in MB if no raw disk image is used\n"
  90            "\n"
  91            "Once the cow_image is created from a raw disk image, you must not modify the original raw disk image\n"
  92            );
  93     exit(1);
  94 }
  95
  96 int main(int argc, char **argv)
  97 {
  98     const char *image_filename, *cow_filename;
  99     int cow_fd, c, nb_args, simple_image;
 100     int64_t image_size;
 101
 102     image_filename = NULL;
 103     image_size = 0;
 104     simple_image = 0;
 105     for(;;) {
 106         c = getopt(argc, argv, "hf:s");
 107         if (c == -1)
 108             break;
 109         switch(c) {
 110         case 'h':
 111             help();
 112             break;
 113         case 'f':
 114             image_filename = optarg;
 115             break;
 116         case 's':
 117             simple_image = 1;
 118             break;
 119         }
 120     }
 121     if (!image_filename)
 122         nb_args = 2;
 123     else
 124         nb_args = 1;
 125     if (optind + nb_args != argc)
 126         help();
 127
 128     cow_filename = argv[optind];
 129     if (nb_args == 2) {
 130         image_size = (int64_t)atoi(argv[optind + 1]) * 2 * 1024;
 131     }
 132
 133     cow_fd = open(cow_filename, O_RDWR | O_CREAT | O_TRUNC | O_LARGEFILE, 0644);
 134     if (!cow_fd < 0)
 135         return -1;
 136     if (simple_image) {
 137         ftruncate64(cow_fd, image_size * 512);
 138     } else {
 139         if (cow_create(cow_fd, image_filename, image_size) < 0) {
 140             fprintf(stderr, "%s: error while formating\n", cow_filename);
 141             exit(1);
 142         }
 143     }
 144     close(cow_fd);
 145     return 0;
 146 }