Re: [Qemu-devel] [PATCH v4 1/3] qapi: add x-debug-query-block-graph

[Max Reitz <mreitz@redhat.com>]

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On 09.10.18 17:00, Vladimir Sementsov-Ogievskiy wrote:
> Add a new command, returning block nodes (and their users) graph.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  qapi/block-core.json           | 108 ++++++++++++++++++++++++
>  include/block/block.h          |   1 +
>  include/sysemu/block-backend.h |   2 +
>  block.c                        | 146 +++++++++++++++++++++++++++++++++
>  block/block-backend.c          |   5 ++
>  blockdev.c                     |   5 ++
>  6 files changed, 267 insertions(+)

[...]

> diff --git a/block.c b/block.c
> index 7710b399a3..90825f427f 100644
> --- a/block.c
> +++ b/block.c
> @@ -4047,6 +4047,152 @@ BlockDeviceInfoList *bdrv_named_nodes_list(Error **errp)

[...]

> +BlockGraph *bdrv_get_block_graph(Error **errp)
> +{
> +    BlockBackend *blk;
> +    BlockJob *job;
> +    BlockDriverState *bs;
> +    BdrvChild *child;
> +    BlockGraphConstructor *gr = dbg_graph_new();
> +
> +    for (blk = blk_all_next(NULL); blk; blk = blk_all_next(blk)) {
> +        char *allocated_name = NULL;
> +        const char *name = blk_name(blk);
> +
> +        if (!name) {

blk_name() never returns NULL, so you need to check for !*name here.

The rest looks OK, although I realized that maybe we want to use the
QAPI type name "BlockGraph" for a non-debug command in the future.  But
I think that as long as it's only this command providing that structure,
we should be free to rename it should the need arise.

(And introspection doesn't care about structure names, I think.)

Max

> +            name = allocated_name = blk_get_attached_dev_id(blk);
> +        }
> +        dbg_graph_add_node(gr, blk, BLOCK_GRAPH_NODE_TYPE_BLOCK_BACKEND, name);
> +        g_free(allocated_name);
> +        if (blk_root(blk)) {
> +            dbg_graph_add_edge(gr, blk, blk_root(blk));
> +        }
> +    }


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