Re: [Qemu-devel] [PATCH v3 3/5] nbd/server: implement dirty bitmap export

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

23.05.2018 13:24, Vladimir Sementsov-Ogievskiy wrote:
> Handle new NBD meta namespace: "qemu", and corresponding queries:
> "qemu:dirty-bitmap:<export bitmap name>".
>
> With new metadata context negotiated, BLOCK_STATUS query will reply
> with dirty-bitmap data, converted to extents. New public function
> nbd_export_bitmap selects bitmap to export. For now, only one bitmap
> may be exported.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---

[...]

>   
> +/* nbd_meta_bitmap_query
> + *
> + * Handle query to 'qemu:' namespace.
> + * @len is the amount of text remaining to be read from the current name, after
> + * the 'qemu:' portion has been stripped.
> + *
> + * Return -errno on I/O error, 0 if option was completely handled by
> + * sending a reply about inconsistent lengths, or 1 on success. */
> +static int nbd_meta_qemu_query(NBDClient *client, NBDExportMetaContexts *meta,
> +                               uint32_t len, Error **errp)
> +{
> +    bool dirty_bitmap = false;
> +    int dirty_bitmap_len = strlen("dirty-bitmap:");
> +    int ret;
> +
> +    if (!client->exp->export_bitmap) {

client->exp is not yet set here. meta->exp should be used instead (and 
patch should be added, to move from meta->export_name to meta->exp, I'll 
add it in v4)

> +        return nbd_opt_skip(client, len, errp);
> +    }
> +
> +    if (len == 0) {
> +        if (client->opt == NBD_OPT_LIST_META_CONTEXT) {
> +            meta->dirty_bitmap = true;
> +        }
> +        trace_nbd_negotiate_meta_query_parse("empty");
> +        return 1;
> +    }
> +
> +    if (len < dirty_bitmap_len) {
> +        trace_nbd_negotiate_meta_query_skip("not dirty-bitmap:");
> +        return nbd_opt_skip(client, len, errp);
> +    }
> +
> +    len -= dirty_bitmap_len;
> +    ret = nbd_meta_pattern(client, "dirty-bitmap:", &dirty_bitmap, errp);
> +    if (ret <= 0) {
> +        return ret;
> +    }
> +    if (!dirty_bitmap) {
> +        trace_nbd_negotiate_meta_query_skip("not dirty-bitmap:");
> +        return nbd_opt_skip(client, len, errp);
> +    }
> +
> +    trace_nbd_negotiate_meta_query_parse("dirty-bitmap:");
> +
> +    return nbd_meta_empty_or_pattern(
> +            client, client->exp->export_bitmap_context +

meta->exp

> +            strlen("qemu:dirty_bitmap:"), len, &meta->dirty_bitmap, errp);
> +}
> +
>   

-- 
Best regards,
Vladimir