On 2018-08-26 16:09, Alberto Garcia wrote: > Block drivers allow opening their children using a reference to an > existing BlockDriverState. These references remain stored in the > 'options' and 'explicit_options' QDicts, but we don't need to keep > them once everything is open. > > What is more important, these values can become wrong if the children > change: > > $ qemu-img create -f qcow2 hd0.qcow2 10M > $ qemu-img create -f qcow2 hd1.qcow2 10M > $ qemu-img create -f qcow2 hd2.qcow2 10M > $ $QEMU -drive if=none,file=hd0.qcow2,node-name=hd0 \ > -drive if=none,file=hd1.qcow2,node-name=hd1,backing=hd0 \ > -drive file=hd2.qcow2,node-name=hd2,backing=hd1 > > After this hd2 has hd1 as its backing file. Now let's remove it using > block_stream: > > (qemu) block_stream hd2 0 hd0.qcow2 > > Now hd0 is the backing file of hd2, but hd2's options QDicts still > contain backing=hd1. > > Signed-off-by: Alberto Garcia <be...@igalia.com> > --- > block.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-)
Also, the question is, why would we discard the child options, but keep
the references (which we do not add, so we only have the ones specified
by the user).
> diff --git a/block.c b/block.c
> index 0dbb1fcc7b..2f2484965d 100644
> --- a/block.c
> +++ b/block.c
> @@ -2763,12 +2763,15 @@ static BlockDriverState *bdrv_open_inherit(const char
> *filename,
> }
> }
>
> - /* Remove all children options from bs->options and bs->explicit_options
> */
> + /* Remove all children options and references
> + * from bs->options and bs->explicit_options */
> QLIST_FOREACH(child, &bs->children, next) {
> char *child_key_dot;
> child_key_dot = g_strdup_printf("%s.", child->name);
> qdict_extract_subqdict(bs->explicit_options, NULL, child_key_dot);
> qdict_extract_subqdict(bs->options, NULL, child_key_dot);
> + qdict_del(bs->explicit_options, child->name);
> + qdict_del(bs->options, child->name);
> g_free(child_key_dot);
> }
>
> @@ -3289,6 +3292,7 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
> {
> BlockDriver *drv;
> BlockDriverState *bs;
> + BdrvChild *child;
> bool old_can_write, new_can_write;
>
> assert(reopen_state != NULL);
> @@ -3313,6 +3317,12 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state)
> bs->open_flags = reopen_state->flags;
> bs->read_only = !(reopen_state->flags & BDRV_O_RDWR);
>
> + /* Remove child references from bs->options and bs->explicit_options */
> + QLIST_FOREACH(child, &bs->children, next) {
> + qdict_del(bs->explicit_options, child->name);
> + qdict_del(bs->options, child->name);
> + }
> +
Why don't you remove the child options as well?
Max
> bdrv_refresh_limits(bs, NULL);
>
> bdrv_set_perm(reopen_state->bs, reopen_state->perm,
>
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