Re: [Qemu-devel] [PATCH v2 11/11] block: Remove BB interface from blockdev-add/del

[Eric Blake]

On 09/20/2016 08:03 AM, Kevin Wolf wrote:
> With this patch, blockdev-add always works on a node level, i.e. it
> creates a BDS, but no BB. Consequently, x-blockdev-del doesn't need the
> 'device' option any more, but 'node-name' becomes mandatory.

How close are we to promoting x-blockdev-del out of the x- namespace? Do
we "just" need the remaining blockdev devices exposed in QMP?

> 
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>  blockdev.c            | 127 
> ++++++++++++++------------------------------------
>  docs/qmp-commands.txt |  24 +++-------
>  qapi/block-core.json  |  30 +++---------
>  3 files changed, 49 insertions(+), 132 deletions(-)
> 

>  void qmp_blockdev_add(BlockdevOptions *options, Error **errp)
>  {
>      BlockDriverState *bs;
> -    BlockBackend *blk = NULL;
>      QObject *obj;
>      Visitor *v = qmp_output_visitor_new(&obj);
>      QDict *qdict;
> @@ -3861,37 +3860,22 @@ void qmp_blockdev_add(BlockdevOptions *options, Error 
> **errp)
>  
>      qdict_flatten(qdict);
>  
> -    if (options->has_id) {
> -        blk = blockdev_init(NULL, qdict, &local_err);
> -        if (local_err) {
> -            error_propagate(errp, local_err);
> -            goto fail;
> -        }
> -
> -        bs = blk_bs(blk);
> -    } else {
> -        if (!qdict_get_try_str(qdict, "node-name")) {
> -            error_setg(errp, "'id' and/or 'node-name' need to be specified 
> for "
> -                       "the root node");
> -            goto fail;
> -        }
> -
> -        bs = bds_tree_init(qdict, errp);
> -        if (!bs) {
> -            goto fail;
> -        }
> +    if (!qdict_get_try_str(qdict, "node-name")) {
> +        error_setg(errp, "'id' and/or 'node-name' need to be specified for "
> +                   "the root node");

Umm, 'id' can't be specified, after this change :)

> -void qmp_x_blockdev_del(bool has_id, const char *id,
> -                        bool has_node_name, const char *node_name, Error 
> **errp)
> +void qmp_x_blockdev_del(const char *node_name, Error **errp)
>  {
>      AioContext *aio_context;
> -    BlockBackend *blk;
>      BlockDriverState *bs;
>  
> -    if (has_id && has_node_name) {
> -        error_setg(errp, "Only one of id and node-name must be specified");
> -        return;
> -    } else if (!has_id && !has_node_name) {
> -        error_setg(errp, "No block device specified");
> +    bs = bdrv_find_node(node_name);
> +    if (!bs) {
> +        error_setg(errp, "Cannot find node %s", node_name);
>          return;
>      }
> -
> -    if (has_id) {
> -        /* blk_by_name() never returns a BB that is not owned by the monitor 
> */
> -        blk = blk_by_name(id);
> -        if (!blk) {
> -            error_setg(errp, "Cannot find block backend %s", id);
> -            return;
> -        }
> -        if (blk_legacy_dinfo(blk)) {
> -            error_setg(errp, "Deleting block backend added with drive-add"
> -                       " is not supported");
> -            return;
> -        }
> -        if (blk_get_refcnt(blk) > 1) {
> -            error_setg(errp, "Block backend %s is in use", id);
> -            return;
> -        }
> -        bs = blk_bs(blk);
> -        aio_context = blk_get_aio_context(blk);
> -    } else {
> -        blk = NULL;
> -        bs = bdrv_find_node(node_name);
> -        if (!bs) {
> -            error_setg(errp, "Cannot find node %s", node_name);
> -            return;
> -        }
> -        if (bdrv_has_blk(bs)) {
> -            error_setg(errp, "Node %s is in use by %s",
> -                       node_name, bdrv_get_parent_name(bs));
> -            return;
> -        }
> -        aio_context = bdrv_get_aio_context(bs);
> +    if (bdrv_has_blk(bs)) {
> +        error_setg(errp, "Node %s is in use by %s",
> +                   node_name, bdrv_get_parent_name(bs));

Is this the source of the "(null)" I was asking about in 10/11?

> +++ b/docs/qmp-commands.txt
> @@ -3141,7 +3141,7 @@ Example (2):
>       "arguments": {
>           "options": {
>             "driver": "qcow2",
> -           "id": "my_disk",
> +           "node-name": "my_disk",
>             "discard": "unmap",
>             "cache": {
>                 "direct": true,
> @@ -3168,18 +3168,9 @@ x-blockdev-del
>  ------------
>  Since 2.5
>  
> -Deletes a block device thas has been added using blockdev-add.
> -The selected device can be either a block backend or a graph node.
> -
> -In the former case the backend will be destroyed, along with its
> -inserted medium if there's any. The command will fail if the backend
> -or its medium are in use.
> -
> -In the latter case the node will be destroyed. The command will fail
> -if the node is attached to a block backend or is otherwise being
> -used.
> -
> -One of "id" or "node-name" must be specified, but not both.
> +Deletes a block device that has been added using blockdev-add.
> +The command will fail # if the node is attached to a device or is

Spurious #.

> +++ b/qapi/block-core.json
> @@ -2217,13 +2217,8 @@
>  # block devices, independent of the block driver:
>  #
>  # @driver:        block driver name
> -# @id:            #optional id by which the new block device can be referred 
> to.
> -#                 This option is only allowed on the top level of 
> blockdev-add.
> -#                 A BlockBackend will be created by blockdev-add if and only 
> if
> -#                 this option is given.

Removing an option. Not backward-compatible, but we've been warning
users that blockdev-add is not ready for primetime yet, so I'm okay with
it (and at least introspection shows it).

> -# @node-name:     #optional the name of a block driver state node (Since 
> 2.0).
> -#                 This option is required on the top level of blockdev-add if
> -#                 the @id option is not given there.
> +# @node-name:     #optional the node name of the new node (Since 2.0).
> +#                 This option is required on the top level of blockdev-add.
>  # @discard:       #optional discard-related options (default: ignore)
>  # @cache:         #optional cache-related options
>  # @aio:           #optional AIO backend (default: threads)
> @@ -2238,8 +2233,6 @@
>  ##
>  { 'union': 'BlockdevOptions',
>    'base': { 'driver': 'BlockdevDriver',
> -# TODO 'id' is a BB-level option, remove it
> -            '*id': 'str',
>              '*node-name': 'str',
>              '*discard': 'BlockdevDiscardOptions',
>              '*cache': 'BlockdevCacheOptions',
> @@ -2323,29 +2316,18 @@
>  # @x-blockdev-del:
>  #
>  # Deletes a block device that has been added using blockdev-add.
> -# The selected device can be either a block backend or a graph node.
> -#
> -# In the former case the backend will be destroyed, along with its
> -# inserted medium if there's any. The command will fail if the backend
> -# or its medium are in use.
> -#
> -# In the latter case the node will be destroyed. The command will fail
> -# if the node is attached to a block backend or is otherwise being
> -# used.
> -#
> -# One of @id or @node-name must be specified, but not both.
> +# The command will fail # if the node is attached to a device or is
> +# otherwise being used.

Spurious # (copy-and-paste strikes again)

Overall, I like the result, but I think it needs just a bit of polish
before I give R-b.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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