qemu-mkcow.c
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/*
* create a COW disk image
*
* Copyright (c) 2003 Fabrice Bellard
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <getopt.h>
#include <inttypes.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>
#include <errno.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include "cow.h"
#include "bswap.h"
int cow_create(int cow_fd, const char *image_filename,
int64_t image_sectors)
{
struct cow_header_v2 cow_header;
int fd;
struct stat st;
memset(&cow_header, 0, sizeof(cow_header));
cow_header.magic = htonl(COW_MAGIC);
cow_header.version = htonl(COW_VERSION);
if (image_filename) {
fd = open(image_filename, O_RDONLY);
if (fd < 0) {
perror(image_filename);
exit(1);
}
image_sectors = lseek64(fd, 0, SEEK_END);
if (fstat(fd, &st) != 0) {
close(fd);
return -1;
}
close(fd);
image_sectors /= 512;
cow_header.mtime = htonl(st.st_mtime);
realpath(image_filename, cow_header.backing_file);
}
cow_header.sectorsize = htonl(512);
cow_header.size = image_sectors * 512;
#ifndef WORDS_BIGENDIAN
cow_header.size = bswap64(cow_header.size);
#endif
write(cow_fd, &cow_header, sizeof(cow_header));
/* resize to include at least all the bitmap */
ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
lseek(cow_fd, 0, SEEK_SET);
return 0;
}
void help(void)
{
printf("qemu-mkcow version " QEMU_VERSION ", Copyright (c) 2003 Fabrice Bellard\n"
"usage: qemu-mkcow [-h] [-f disk_image] cow_image [cow_size]\n"
"Create a Copy On Write disk image from an optional raw disk image\n"
"\n"
"-f disk_image set the raw disk image name\n"
"cow_image the created cow_image\n"
"cow_size the create cow_image size in MB if no raw disk image is used\n"
"\n"
"Once the cow_image is created from a raw disk image, you must not modify the original raw disk image\n"
);
exit(1);
}
int main(int argc, char **argv)
{
const char *image_filename, *cow_filename;
int cow_fd, c, nb_args, simple_image;
int64_t image_size;
image_filename = NULL;
image_size = 0;
simple_image = 0;
for(;;) {
c = getopt(argc, argv, "hf:s");
if (c == -1)
break;
switch(c) {
case 'h':
help();
break;
case 'f':
image_filename = optarg;
break;
case 's':
simple_image = 1;
break;
}
}
if (!image_filename)
nb_args = 2;
else
nb_args = 1;
if (optind + nb_args != argc)
help();
cow_filename = argv[optind];
if (nb_args == 2) {
image_size = (int64_t)atoi(argv[optind + 1]) * 2 * 1024;
}
cow_fd = open(cow_filename, O_RDWR | O_CREAT | O_TRUNC | O_LARGEFILE, 0644);
if (!cow_fd < 0)
return -1;
if (simple_image) {
ftruncate64(cow_fd, image_size * 512);
} else {
if (cow_create(cow_fd, image_filename, image_size) < 0) {
fprintf(stderr, "%s: error while formating\n", cow_filename);
exit(1);
}
}
close(cow_fd);
return 0;
}