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>
diff --git a/qemu-img.c b/qemu-img.c
index 849eb41..c092ccf 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1562,13 +1562,15 @@
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 @@
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 @@
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 @@
}
}
- 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 @@
* 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);