Re: [RFC PATCH 11/22] qemu-nbd: Use blk_exp_add() to create the export

From: Eric Blake <eblake@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org
Cc: qemu-devel@nongnu.org, mreitz@redhat.com
Subject: Re: [RFC PATCH 11/22] qemu-nbd: Use blk_exp_add() to create the export
Date: Wed, 19 Aug 2020 15:35:33 -0500	[thread overview]
Message-ID: <2e7221ad-1080-7eb7-d427-866c1aa82b7a@redhat.com> (raw)
In-Reply-To: <20200813162935.210070-12-kwolf@redhat.com>

On 8/13/20 11:29 AM, Kevin Wolf wrote:
> With this change, NBD exports are only created through the BlockExport
> interface any more. This allows us finally to move things from the NBD

s/are only/are now only/; s/any more //

> layer to the BlockExport layer if they make sense for other export
> types, too.
> 
> blk_exp_add() returns only a weak reference, so the explicit
> nbd_export_put() goes away.

Feel free to rename get/put to ref/unref in your series if that makes 
life any easier.

> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---

> @@ -1050,9 +1050,27 @@ int main(int argc, char **argv)
>   
>       bs->detect_zeroes = detect_zeroes;
>   
> -    export = nbd_export_new(bs, export_name,
> -                            export_description, bitmap, readonly, shared > 1,
> -                            writethrough, &error_fatal);
> +    nbd_server_is_qemu_nbd(true);

Feels a bit like a backdoor hack, but gets the job done (and as you 
said, we had quite an IRC conversation about what it would take to get 
socket activation working, so leaving that in qemu-nbd for now is 
reasonable for the first patch series).

> +
> +    export_opts = g_new(BlockExportOptions, 1);
> +    *export_opts = (BlockExportOptions) {
> +        .type               = BLOCK_EXPORT_TYPE_NBD,
> +        .has_writethrough   = true,
> +        .writethrough       = writethrough,
> +        .u.nbd = {
> +            .device             = g_strdup(bdrv_get_node_name(bs)),
> +            .has_name           = true,
> +            .name               = g_strdup(export_name),
> +            .has_description    = !!export_description,
> +            .description        = g_strdup(export_description),
> +            .has_writable       = true,
> +            .writable           = !readonly,
> +            .has_bitmap         = !!bitmap,
> +            .bitmap             = g_strdup(bitmap),
> +        },
> +    };
> +    blk_exp_add(export_opts, &error_fatal);
> +    qapi_free_BlockExportOptions(export_opts);

Looks sane.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org