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qemu-img rebase: use empty string to rebase without backing file 

This patch allows an empty filename to be passed as the new base image name
for qemu-img rebase to mean base the image on no backing file (i.e.
independent of any backing file). According to Eric Blake, qemu-img rebase
already supports this when '-u' is used; this adds support when -u is not
used.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Alex Bligh 2012-10-16 13:46:18 +01:00 committed by Kevin Wolf
parent b3d0380ec2
commit a616673dd1
2 changed files with 22 additions and 11 deletions
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29
qemu-img.c
View File

@ -1562,13 +1562,15 @@ static int img_rebase(int argc, char **argv)
error_report("Could not open old backing file '%s'", backing_name);
goto out;
}
bs_new_backing = bdrv_new("new_backing");
ret = bdrv_open(bs_new_backing, out_baseimg, BDRV_O_FLAGS,
if (out_baseimg[0]) {
bs_new_backing = bdrv_new("new_backing");
ret = bdrv_open(bs_new_backing, out_baseimg, BDRV_O_FLAGS,
new_backing_drv);
if (ret) {
error_report("Could not open new backing file '%s'", out_baseimg);
goto out;
if (ret) {
error_report("Could not open new backing file '%s'",
out_baseimg);
goto out;
}
}
}
@ -1584,7 +1586,7 @@ static int img_rebase(int argc, char **argv)
if (!unsafe) {
uint64_t num_sectors;
uint64_t old_backing_num_sectors;
uint64_t new_backing_num_sectors;
uint64_t new_backing_num_sectors = 0;
uint64_t sector;
int n;
uint8_t * buf_old;
@ -1596,7 +1598,9 @@ static int img_rebase(int argc, char **argv)
bdrv_get_geometry(bs, &num_sectors);
bdrv_get_geometry(bs_old_backing, &old_backing_num_sectors);
bdrv_get_geometry(bs_new_backing, &new_backing_num_sectors);
if (bs_new_backing) {
bdrv_get_geometry(bs_new_backing, &new_backing_num_sectors);
}
if (num_sectors != 0) {
local_progress = (float)100 /
@ -1636,7 +1640,7 @@ static int img_rebase(int argc, char **argv)
}
}
if (sector >= new_backing_num_sectors) {
if (sector >= new_backing_num_sectors || !bs_new_backing) {
memset(buf_new, 0, n * BDRV_SECTOR_SIZE);
} else {
if (sector + n > new_backing_num_sectors) {
@ -1682,7 +1686,12 @@ static int img_rebase(int argc, char **argv)
* backing file are overwritten in the COW file now, so the visible content
* doesn't change when we switch the backing file.
*/
ret = bdrv_change_backing_file(bs, out_baseimg, out_basefmt);
if (out_baseimg && *out_baseimg) {
ret = bdrv_change_backing_file(bs, out_baseimg, out_basefmt);
} else {
ret = bdrv_change_backing_file(bs, NULL, NULL);
}
if (ret == -ENOSPC) {
error_report("Could not change the backing file to '%s': No "
"space left in the file header", out_baseimg);

4
qemu-img.texi
View File

@ -148,7 +148,9 @@ Changes the backing file of an image. Only the formats @code{qcow2} and
The backing file is changed to @var{backing_file} and (if the image format of
@var{filename} supports this) the backing file format is changed to
@var{backing_fmt}.
@var{backing_fmt}. If @var{backing_file} is specified as ``'' (the empty
string), then the image is rebased onto no backing file (i.e. it will exist
independently of any backing file).
There are two different modes in which @code{rebase} can operate:
@table @option