Re: [PATCH v6 11/14] block/core: add generic infrastructure for x-blockdev-amend qmp command

[Max Reitz]

On 10.05.20 15:40, Maxim Levitsky wrote:
> blockdev-amend will be used similiar to blockdev-create
> to allow on the fly changes of the structure of the format based block 
> devices.
> 
> Current plan is to first support encryption keyslot management for luks
> based formats (raw and embedded in qcow2)
> 
> Signed-off-by: Maxim Levitsky <address@hidden>
> Reviewed-by: Daniel P. Berrangé <address@hidden>
> ---
>  block/Makefile.objs       |   2 +-
>  block/amend.c             | 108 ++++++++++++++++++++++++++++++++++++++
>  include/block/block_int.h |  21 +++++---
>  qapi/block-core.json      |  42 +++++++++++++++
>  qapi/job.json             |   4 +-
>  5 files changed, 169 insertions(+), 8 deletions(-)
>  create mode 100644 block/amend.c

[...]

> diff --git a/block/amend.c b/block/amend.c
> new file mode 100644
> index 0000000000..4840c0ffef
> --- /dev/null
> +++ b/block/amend.c

[...]

> +void qmp_x_blockdev_amend(const char *job_id,
> +                          const char *node_name,
> +                          BlockdevAmendOptions *options,
> +                          bool has_force,
> +                          bool force,
> +                          Error **errp)
> +{
> +    BlockdevAmendJob *s;
> +    const char *fmt = BlockdevDriver_str(options->driver);
> +    BlockDriver *drv = bdrv_find_format(fmt);
> +    BlockDriverState *bs = bdrv_find_node(node_name);
> +
> +    /*
> +     * If the driver is in the schema, we know that it exists.

I wonder why create.c then still checks whether drv == NULL.

I wouldn’t count on the schema.  For example, with modularized block
driver I could imagine that a driver appears in the schema, but loading
the module fails, so that drv still ends up NULL.

>         But it may not
> +     * be whitelisted.
> +     */
> +    assert(drv);
> +    if (bdrv_uses_whitelist() && !bdrv_is_whitelisted(drv, false)) {
> +        error_setg(errp, "Driver is not whitelisted");
> +        return;
> +    }

[...]

> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 0a71357b50..fdb0cdbcdd 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -133,12 +133,27 @@ struct BlockDriver {
>      int (*bdrv_file_open)(BlockDriverState *bs, QDict *options, int flags,
>                            Error **errp);
>      void (*bdrv_close)(BlockDriverState *bs);
> +
> +
>      int coroutine_fn (*bdrv_co_create)(BlockdevCreateOptions *opts,
>                                         Error **errp);
>      int coroutine_fn (*bdrv_co_create_opts)(BlockDriver *drv,
>                                              const char *filename,
>                                              QemuOpts *opts,
>                                              Error **errp);
> +
> +    int coroutine_fn (*bdrv_co_amend)(BlockDriverState *bs,
> +                                      BlockdevAmendOptions *opts,
> +                                      bool force,
> +                                      Error **errp);
> +
> +    int (*bdrv_amend_options)(BlockDriverState *bs,
> +                              QemuOpts *opts,
> +                              BlockDriverAmendStatusCB *status_cb,
> +                              void *cb_opaque,
> +                              bool force,
> +                              Error **errp);
> +
>      int (*bdrv_make_empty)(BlockDriverState *bs);
>  
>      /*
> @@ -433,12 +448,6 @@ struct BlockDriver {
>                                        BdrvCheckResult *result,
>                                        BdrvCheckMode fix);
>  
> -    int (*bdrv_amend_options)(BlockDriverState *bs, QemuOpts *opts,
> -                              BlockDriverAmendStatusCB *status_cb,
> -                              void *cb_opaque,
> -                              bool force,
> -                              Error **errp);
> -

No harm done, but why not just leave it where it was?

>      void (*bdrv_debug_event)(BlockDriverState *bs, BlkdebugEvent event);
>  
>      /* TODO Better pass a option string/QDict/QemuOpts to add any rule? */
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 943df1926a..74db515414 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -4649,6 +4649,48 @@
>    'data': { 'job-id': 'str',
>              'options': 'BlockdevCreateOptions' } }
>  
> +##
> +# @BlockdevAmendOptions:
> +#
> +# Options for amending an image format
> +#
> +# @driver           block driver that is suitable for the image

Missing colon after @driver.  Also, what does “suitable” mean?
Shouldn’t it be exactly the node’s driver?  (i.e. “Block driver of the
node to amend”)

Max

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