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qemu-img: Allow rebase with no input base 

Currently, without -u, you cannot add a backing file to an image when it
currently has none:

$ qemu-img rebase -b base.qcow2 foo.qcow2
qemu-img: Could not open old backing file '': The 'file' block driver
requires a file name

It is really simple to allow this, though (effectively by setting
old_backing_size to 0), so this patch does just that.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Max Reitz 2019-05-09 19:52:35 +02:00 committed by Kevin Wolf
parent 433e8e3b22
commit 35ddd9300b
1 changed files with 34 additions and 27 deletions
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61
qemu-img.c
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@ -3312,26 +3312,30 @@ static int img_rebase(int argc, char **argv)
char backing_name[PATH_MAX]; char backing_name[PATH_MAX];
QDict *options = NULL; QDict *options = NULL;
if (bs->backing_format[0] != '\0') { if (bs->backing) {
options = qdict_new(); if (bs->backing_format[0] != '\0') {
qdict_put_str(options, "driver", bs->backing_format);
}
if (force_share) {
if (!options) {
options = qdict_new(); options = qdict_new();
qdict_put_str(options, "driver", bs->backing_format);
} }
qdict_put_bool(options, BDRV_OPT_FORCE_SHARE, true);
} if (force_share) {
bdrv_get_backing_filename(bs, backing_name, sizeof(backing_name)); if (!options) {
blk_old_backing = blk_new_open(backing_name, NULL, options = qdict_new();
options, src_flags, &local_err); }
if (!blk_old_backing) { qdict_put_bool(options, BDRV_OPT_FORCE_SHARE, true);
error_reportf_err(local_err, }
"Could not open old backing file '%s': ", bdrv_get_backing_filename(bs, backing_name, sizeof(backing_name));
backing_name); blk_old_backing = blk_new_open(backing_name, NULL,
ret = -1; options, src_flags, &local_err);
goto out; if (!blk_old_backing) {
error_reportf_err(local_err,
"Could not open old backing file '%s': ",
backing_name);
ret = -1;
goto out;
}
} else {
blk_old_backing = NULL;
} }
if (out_baseimg[0]) { if (out_baseimg[0]) {
@ -3384,7 +3388,7 @@ static int img_rebase(int argc, char **argv)
*/ */
if (!unsafe) { if (!unsafe) {
int64_t size; int64_t size;
int64_t old_backing_size; int64_t old_backing_size = 0;
int64_t new_backing_size = 0; int64_t new_backing_size = 0;
uint64_t offset; uint64_t offset;
int64_t n; int64_t n;
@ -3400,15 +3404,18 @@ static int img_rebase(int argc, char **argv)
ret = -1; ret = -1;
goto out; goto out;
} }
old_backing_size = blk_getlength(blk_old_backing); if (blk_old_backing) {
if (old_backing_size < 0) { old_backing_size = blk_getlength(blk_old_backing);
char backing_name[PATH_MAX]; if (old_backing_size < 0) {
char backing_name[PATH_MAX];
bdrv_get_backing_filename(bs, backing_name, sizeof(backing_name)); bdrv_get_backing_filename(bs, backing_name,
error_report("Could not get size of '%s': %s", sizeof(backing_name));
backing_name, strerror(-old_backing_size)); error_report("Could not get size of '%s': %s",
ret = -1; backing_name, strerror(-old_backing_size));
goto out; ret = -1;
goto out;
}
} }
if (blk_new_backing) { if (blk_new_backing) {
new_backing_size = blk_getlength(blk_new_backing); new_backing_size = blk_getlength(blk_new_backing);