Re: [Qemu-devel] [RFC PATCH 05/10] block: Add 'keep_old_opts' parameter to bdrv_reopen_queue()

[Kevin Wolf <kwolf@redhat.com>]

Am 14.06.2018 um 17:49 hat Alberto Garcia geschrieben:
> The bdrv_reopen_queue() function is used to create a queue with the
> BDSs that are going to be reopened and their new options. Once the
> queue is ready bdrv_reopen_multiple() is called to perform the
> operation.
> 
> The original options from each one of the BDSs are kept, with the new
> options passed to bdrv_reopen_queue() applied on top of them.
> 
> For "x-blockdev-reopen" we want a function that behaves much like
> "blockdev-add". We want to ignore the previous set of options so that
> only the ones actually specified by the user are applied, with the
> rest having their default values.
> 
> We can achieve this by adding a new parameter to bdrv_reopen_queue()
> that specifies whether the old set of options is kept or discarded
> when building the reopen queue. All current callers will set that
> parameter to true, but x-blockdev-reopen will set it to false.
> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
>  block.c               | 34 +++++++++++++++++++---------------
>  block/replication.c   |  4 ++--
>  include/block/block.h |  3 ++-
>  qemu-io-cmds.c        |  2 +-
>  4 files changed, 24 insertions(+), 19 deletions(-)
> 
> diff --git a/block.c b/block.c
> index a741300fae..0b9268a48d 100644
> --- a/block.c
> +++ b/block.c
> @@ -2850,7 +2850,8 @@ static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
>                                                   int flags,
>                                                   const BdrvChildRole *role,
>                                                   QDict *parent_options,
> -                                                 int parent_flags)
> +                                                 int parent_flags,
> +                                                 bool keep_old_opts)

Can we change the semantics of keep_old_opts so that flags is completely
ignored for keep_old_opts=false?

Flags are one of the reasons why the behaviour of bdrv_reopen() is
rather complex and I'd prefer not having that complexity in a public
interface. To be honest, I wouldn't be sure that I could write a correct
documentation with it.

Kevin