On 09/25/2015 12:17 AM, Wen Congyang wrote: > For block replication, we have such backing chain: > secondary disk <-- hidden disk <-- active disk > secondary disk is top BDS(use bacing reference), so it can be opened in
s/BDS(use bacing/BDS (use backing/
> read-write mode. But hidden disk is read only, and we need to write to
> hidden disk(backup job will write data to it).
s/disk(/disk (/
>
> TODO: support opening backing file in read-write mode if the BDS is
> created by QMP command blockdev-add.
>
> Signed-off-by: Wen Congyang <we...@cn.fujitsu.com>
> Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
> Signed-off-by: Gonglei <arei.gong...@huawei.com>
> ---
> block.c | 41 ++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 40 insertions(+), 1 deletion(-)
>
I really don't like this patch. We are able to automatically (re-)open
backing files for write during block-commit, without having to expose a
knob to the user then, so exposing a knob to the user here feels wrong.
> +#define ALLOW_WRITE_BACKING_FILE "allow-write-backing-file"
> +static QemuOptsList backing_file_opts = {
> + .name = "backing_file",
> + .head = QTAILQ_HEAD_INITIALIZER(backing_file_opts.head),
> + .desc = {
> + {
> + .name = ALLOW_WRITE_BACKING_FILE,
> + .type = QEMU_OPT_BOOL,
> + .help = "allow writes to backing file",
> + },
And even if we DO need this knob (which I doubt), you need corresponding
documentation of the knob in qapi/block-core.json, since we are trying
to keep the command line and QMP in sync when it comes to adding new
options.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
signature.asc
Description: OpenPGP digital signature
