netdev - Re: [PATCH RFC iproute2-next 1/2] rdma: add 'link add/delete' commands

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Message-ID: <20181128200844.GQ4559@mtr-leonro.mtl.com>
Date:   Wed, 28 Nov 2018 22:08:44 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Steve Wise <swise@...ngridcomputing.com>
Cc:     dsahern@...il.com, stephen@...workplumber.org,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        BMT@...ich.ibm.com
Subject: Re: [PATCH RFC iproute2-next 1/2] rdma: add 'link add/delete'
 commands

On Wed, Nov 28, 2018 at 10:02:04PM +0200, Leon Romanovsky wrote:
> On Wed, Nov 28, 2018 at 01:34:14PM -0600, Steve Wise wrote:
> > ...
> >
> > >>> +	rd_prepare_msg(rd, RDMA_NLDEV_CMD_NEWLINK, &seq,
> > >>> +		       (NLM_F_REQUEST | NLM_F_ACK));
> > >>> +	mnl_attr_put_strz(rd->nlh, RDMA_NLDEV_ATTR_DEV_NAME, name);
> > >>> +	mnl_attr_put_strz(rd->nlh, RDMA_NLDEV_ATTR_LINK_TYPE, type);
> > >>> +	mnl_attr_put_strz(rd->nlh, RDMA_NLDEV_ATTR_NDEV_NAME, dev);
> > >>> +	ret = rd_send_msg(rd);
> > >>> +	if (ret)
> > >>> +		return ret;
> > >>> +
> > >>> +	ret = rd_recv_msg(rd, link_add_parse_cb, rd, seq);
> > >>> +	if (ret)
> > >>> +		perror(NULL);
> > >> Why do you need rd_recv_msg()? I think that it is not needed, at least
> > >> for rename, I didn't need it.
> > >> https://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git/tree/rdma/dev.c#n244
> > > To get the response of if it was successfully added.  It provides the
> > > errno value.
> > If I don't do the rd_recv_msg, then adding the same name twice fails
> > without any error notification.  Ditto for deleting a non-existent
> > link.  So the rd_recv_msg() allows getting the failure reason (and
> > detecting the failure). 
> >
>
> Shouldn't extack provide such information as part of NLM_F_ACK flag?
>
> just shooting into the air, will take more close look tomorrow.

OK, it was easier than I thought.

You are right, need both send and receive to get the reason.

Can you prepare general function and update rename part too?
Something like send_receive(...) with dummy callback for receive path.

Thanks

>
> Thanks
>
> >



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