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qemu-img: Add compare subcommand
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This patch adds new qemu-img subcommand that compares content of two disk
images.

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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@LaneWolf @kevmw
LaneWolf authored and kevmw committed Feb 22, 2013
1 parent f382d43 commit d14ed18
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Showing 3 changed files with 348 additions and 1 deletion.
6 changes: 6 additions & 0 deletions qemu-img-cmds.hx
View file
Expand Up @@ -27,6 +27,12 @@ STEXI
@item commit [-q] [-f @var{fmt}] [-t @var{cache}] @var{filename}
ETEXI

DEF("compare", img_compare,
"compare [-f fmt] [-F fmt] [-p] [-q] [-s] filename1 filename2")
STEXI
@item compare [-f @var{fmt}] [-F @var{fmt}] [-p] [-q] [-s] @var{filename1} @var{filename2}
ETEXI

DEF("convert", img_convert,
"convert [-c] [-p] [-q] [-f fmt] [-t cache] [-O output_fmt] [-o options] [-s snapshot_name] [-S sparse_size] filename [filename2 [...]] output_filename")
STEXI
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290 changes: 289 additions & 1 deletion qemu-img.c
View file
Expand Up @@ -113,7 +113,12 @@ static void help(void)
" '-a' applies a snapshot (revert disk to saved state)\n"
" '-c' creates a snapshot\n"
" '-d' deletes a snapshot\n"
" '-l' lists all snapshots in the given image\n";
" '-l' lists all snapshots in the given image\n"
"\n"
"Parameters to compare subcommand:\n"
" '-f' first image format\n"
" '-F' second image format\n"
" '-s' run in Strict mode - fail on different image size or sector allocation\n";

printf("%s\nSupported formats:", help_msg);
bdrv_iterate_format(format_print, NULL);
Expand Down Expand Up @@ -820,6 +825,289 @@ static int compare_sectors(const uint8_t *buf1, const uint8_t *buf2, int n,

#define IO_BUF_SIZE (2 * 1024 * 1024)

static int64_t sectors_to_bytes(int64_t sectors)
{
return sectors << BDRV_SECTOR_BITS;
}

static int64_t sectors_to_process(int64_t total, int64_t from)
{
return MIN(total - from, IO_BUF_SIZE >> BDRV_SECTOR_BITS);
}

/*
* Check if passed sectors are empty (not allocated or contain only 0 bytes)
*
* Returns 0 in case sectors are filled with 0, 1 if sectors contain non-zero
* data and negative value on error.
*
* @param bs: Driver used for accessing file
* @param sect_num: Number of first sector to check
* @param sect_count: Number of sectors to check
* @param filename: Name of disk file we are checking (logging purpose)
* @param buffer: Allocated buffer for storing read data
* @param quiet: Flag for quiet mode
*/
static int check_empty_sectors(BlockDriverState *bs, int64_t sect_num,
int sect_count, const char *filename,
uint8_t *buffer, bool quiet)
{
int pnum, ret = 0;
ret = bdrv_read(bs, sect_num, buffer, sect_count);
if (ret < 0) {
error_report("Error while reading offset %" PRId64 " of %s: %s",
sectors_to_bytes(sect_num), filename, strerror(-ret));
return ret;
}
ret = is_allocated_sectors(buffer, sect_count, &pnum);
if (ret || pnum != sect_count) {
qprintf(quiet, "Content mismatch at offset %" PRId64 "!\n",
sectors_to_bytes(ret ? sect_num : sect_num + pnum));
return 1;
}

return 0;
}

/*
* Compares two images. Exit codes:
*
* 0 - Images are identical
* 1 - Images differ
* >1 - Error occurred
*/
static int img_compare(int argc, char **argv)
{
const char *fmt1 = NULL, *fmt2 = NULL, *filename1, *filename2;
BlockDriverState *bs1, *bs2;
int64_t total_sectors1, total_sectors2;
uint8_t *buf1 = NULL, *buf2 = NULL;
int pnum1, pnum2;
int allocated1, allocated2;
int ret = 0; /* return value - 0 Ident, 1 Different, >1 Error */
bool progress = false, quiet = false, strict = false;
int64_t total_sectors;
int64_t sector_num = 0;
int64_t nb_sectors;
int c, pnum;
uint64_t bs_sectors;
uint64_t progress_base;

for (;;) {
c = getopt(argc, argv, "hpf:F:sq");
if (c == -1) {
break;
}
switch (c) {
case '?':
case 'h':
help();
break;
case 'f':
fmt1 = optarg;
break;
case 'F':
fmt2 = optarg;
break;
case 'p':
progress = true;
break;
case 'q':
quiet = true;
break;
case 's':
strict = true;
break;
}
}

/* Progress is not shown in Quiet mode */
if (quiet) {
progress = false;
}


if (optind > argc - 2) {
help();
}
filename1 = argv[optind++];
filename2 = argv[optind++];

/* Initialize before goto out */
qemu_progress_init(progress, 2.0);

bs1 = bdrv_new_open(filename1, fmt1, BDRV_O_FLAGS, true, quiet);
if (!bs1) {
error_report("Can't open file %s", filename1);
ret = 2;
goto out3;
}

bs2 = bdrv_new_open(filename2, fmt2, BDRV_O_FLAGS, true, quiet);
if (!bs2) {
error_report("Can't open file %s", filename2);
ret = 2;
goto out2;
}

buf1 = qemu_blockalign(bs1, IO_BUF_SIZE);
buf2 = qemu_blockalign(bs2, IO_BUF_SIZE);
bdrv_get_geometry(bs1, &bs_sectors);
total_sectors1 = bs_sectors;
bdrv_get_geometry(bs2, &bs_sectors);
total_sectors2 = bs_sectors;
total_sectors = MIN(total_sectors1, total_sectors2);
progress_base = MAX(total_sectors1, total_sectors2);

qemu_progress_print(0, 100);

if (strict && total_sectors1 != total_sectors2) {
ret = 1;
qprintf(quiet, "Strict mode: Image size mismatch!\n");
goto out;
}

for (;;) {
nb_sectors = sectors_to_process(total_sectors, sector_num);
if (nb_sectors <= 0) {
break;
}
allocated1 = bdrv_is_allocated_above(bs1, NULL, sector_num, nb_sectors,
&pnum1);
if (allocated1 < 0) {
ret = 3;
error_report("Sector allocation test failed for %s", filename1);
goto out;
}

allocated2 = bdrv_is_allocated_above(bs2, NULL, sector_num, nb_sectors,
&pnum2);
if (allocated2 < 0) {
ret = 3;
error_report("Sector allocation test failed for %s", filename2);
goto out;
}
nb_sectors = MIN(pnum1, pnum2);

if (allocated1 == allocated2) {
if (allocated1) {
ret = bdrv_read(bs1, sector_num, buf1, nb_sectors);
if (ret < 0) {
error_report("Error while reading offset %" PRId64 " of %s:"
" %s", sectors_to_bytes(sector_num), filename1,
strerror(-ret));
ret = 4;
goto out;
}
ret = bdrv_read(bs2, sector_num, buf2, nb_sectors);
if (ret < 0) {
error_report("Error while reading offset %" PRId64
" of %s: %s", sectors_to_bytes(sector_num),
filename2, strerror(-ret));
ret = 4;
goto out;
}
ret = compare_sectors(buf1, buf2, nb_sectors, &pnum);
if (ret || pnum != nb_sectors) {
ret = 1;
qprintf(quiet, "Content mismatch at offset %" PRId64 "!\n",
sectors_to_bytes(
ret ? sector_num : sector_num + pnum));
goto out;
}
}
} else {
if (strict) {
ret = 1;
qprintf(quiet, "Strict mode: Offset %" PRId64
" allocation mismatch!\n",
sectors_to_bytes(sector_num));
goto out;
}

if (allocated1) {
ret = check_empty_sectors(bs1, sector_num, nb_sectors,
filename1, buf1, quiet);
} else {
ret = check_empty_sectors(bs2, sector_num, nb_sectors,
filename2, buf1, quiet);
}
if (ret) {
if (ret < 0) {
ret = 4;
error_report("Error while reading offset %" PRId64 ": %s",
sectors_to_bytes(sector_num), strerror(-ret));
}
goto out;
}
}
sector_num += nb_sectors;
qemu_progress_print(((float) nb_sectors / progress_base)*100, 100);
}

if (total_sectors1 != total_sectors2) {
BlockDriverState *bs_over;
int64_t total_sectors_over;
const char *filename_over;

qprintf(quiet, "Warning: Image size mismatch!\n");
if (total_sectors1 > total_sectors2) {
total_sectors_over = total_sectors1;
bs_over = bs1;
filename_over = filename1;
} else {
total_sectors_over = total_sectors2;
bs_over = bs2;
filename_over = filename2;
}

for (;;) {
nb_sectors = sectors_to_process(total_sectors_over, sector_num);
if (nb_sectors <= 0) {
break;
}
ret = bdrv_is_allocated_above(bs_over, NULL, sector_num,
nb_sectors, &pnum);
if (ret < 0) {
ret = 3;
error_report("Sector allocation test failed for %s",
filename_over);
goto out;

}
nb_sectors = pnum;
if (ret) {
ret = check_empty_sectors(bs_over, sector_num, nb_sectors,
filename_over, buf1, quiet);
if (ret) {
if (ret < 0) {
ret = 4;
error_report("Error while reading offset %" PRId64
" of %s: %s", sectors_to_bytes(sector_num),
filename_over, strerror(-ret));
}
goto out;
}
}
sector_num += nb_sectors;
qemu_progress_print(((float) nb_sectors / progress_base)*100, 100);
}
}

qprintf(quiet, "Images are identical.\n");
ret = 0;

out:
bdrv_delete(bs2);
qemu_vfree(buf1);
qemu_vfree(buf2);
out2:
bdrv_delete(bs1);
out3:
qemu_progress_end();
return ret;
}

static int img_convert(int argc, char **argv)
{
int c, ret = 0, n, n1, bs_n, bs_i, compress, cluster_size, cluster_sectors;
Expand Down
53 changes: 53 additions & 0 deletions qemu-img.texi
View file
Expand Up @@ -84,6 +84,18 @@ deletes a snapshot
lists all snapshots in the given image
@end table

Parameters to compare subcommand:

@table @option

@item -f
First image format
@item -F
Second image format
@item -s
Strict mode - fail on on different image size or sector allocation
@end table

Command description:

@table @option
Expand Down Expand Up @@ -118,6 +130,47 @@ it doesn't need to be specified separately in this case.

Commit the changes recorded in @var{filename} in its base image.

@item compare [-f @var{fmt}] [-F @var{fmt}] [-p] [-s] [-q] @var{filename1} @var{filename2}

Check if two images have the same content. You can compare images with
different format or settings.

The format is probed unless you specify it by @var{-f} (used for
@var{filename1}) and/or @var{-F} (used for @var{filename2}) option.

By default, images with different size are considered identical if the larger
image contains only unallocated and/or zeroed sectors in the area after the end
of the other image. In addition, if any sector is not allocated in one image
and contains only zero bytes in the second one, it is evaluated as equal. You
can use Strict mode by specifying the @var{-s} option. When compare runs in
Strict mode, it fails in case image size differs or a sector is allocated in
one image and is not allocated in the second one.

By default, compare prints out a result message. This message displays
information that both images are same or the position of the first different
byte. In addition, result message can report different image size in case
Strict mode is used.

Compare exits with @code{0} in case the images are equal and with @code{1}
in case the images differ. Other exit codes mean an error occurred during
execution and standard error output should contain an error message.
The following table sumarizes all exit codes of the compare subcommand:

@table @option

@item 0
Images are identical
@item 1
Images differ
@item 2
Error on opening an image
@item 3
Error on checking a sector allocation
@item 4
Error on reading data

@end table

@item convert [-c] [-p] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}

Convert the disk image @var{filename} or a snapshot @var{snapshot_name} to disk image @var{output_filename}
Expand Down

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