Re: [PATCH v2 1/8] block/nbd: move initial connect to coroutine

[Eric Blake <eblake@redhat.com>]

On 11/30/20 7:40 AM, Vladimir Sementsov-Ogievskiy wrote:
> We are going to implement reconnect-on-open. Let's reuse existing
> reconnect loop. For this, do initial connect in connection coroutine.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/nbd.c | 94 ++++++++++++++++++++++++++++++-----------------------
>  1 file changed, 53 insertions(+), 41 deletions(-)
> 

> @@ -2279,6 +2268,29 @@ static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
>      bdrv_inc_in_flight(bs);
>      aio_co_schedule(bdrv_get_aio_context(bs), s->connection_co);
>  
> +    if (qemu_in_coroutine()) {
> +        s->open_co = qemu_coroutine_self();
> +        qemu_coroutine_yield();
> +    } else {
> +        BDRV_POLL_WHILE(bs, s->state == NBD_CLIENT_OPENING);
> +    }
> +
> +    if (s->state != NBD_CLIENT_CONNECTED && s->connect_status < 0) {
> +        /*
> +         * It's possible that state != NBD_CLIENT_CONNECTED, but connect_status
> +         * is 0. This means that initial connecting succeed, but failed later
> +         * (during BDRV_POLL_WHILE). It's a rare case, but it happen in iotest

This means that starting the initial connection succeeded, but we failed
later (during BDRV_POLL_WHILE).

happens

> +         * 83. Let's don't care and just report success in this case: it not
> +         * much differs from the case when connection failed immediately after
> +         * succeeded open.

We don't care, and just report success in this case, as it does not
change our behavior from the case when the connection fails right after
open succeeds.


> +         */
> +        assert(s->connect_err);
> +        error_propagate(errp, s->connect_err);
> +        s->connect_err = NULL;
> +        nbd_clear_bdrvstate(s);
> +        return s->connect_status;
> +    }
> +
>      return 0;
>  }
>  
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

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