From mboxrd@z Thu Jan  1 00:00:00 1970
From: Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Netlink messages without NLM_F_REQUEST flag
Date: Wed, 7 Jun 2017 19:19:01 +0300
Message-ID: <20170607161901.GD1127@mtr-leonro.local>
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Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: Kaike Wan <kaike.wan-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, John Fleck <john.fleck-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Ira Weiny <ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Thomas Graf <tgraf-G/eBtMaohhA@public.gmane.org>, Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Jiri Pirko <jiri-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>, RDMA mailing list <linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, linux-netdev <netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
List-Id: linux-rdma@vger.kernel.org


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Hi Kaike,

In the commit bc10ed7d3d19 ("IB/core: Add rdma netlink helper functions"),
part of larger series [1], you introduced ibnl_rcv_reply_skb(), which is very
similar to netlink_rcv_skb() with one major change.

The netlink messages without NLM_F_REQUEST flag are handled by ibnl_rcv_reply_skb(),
while netlink_rcv_skb() doesn't. The comment introduced in commit d35b685640ae
"[NETLINK]: Ignore !NLM_F_REQUEST messages directly in netlink_run_queue()")
says that "Only requests are handled by the kernel".

It makes me wonder if it is expected behavior for ibnl_rcv_reply_skb()
to handle !NLM_F_REQUEST messages and do we really need it? What are the scenarios?
In my use case, which is for sure different from yours, I'm always setting NLM_F_REQUEST
while communicating with kernel.

Thanks

[1] http://www.spinics.net/lists/linux-rdma/msg28153.html

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