netdev - Re: [PATCH net] net/smc: fix unexpected SMC_CLC_DECL_ERR

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Date:   Wed, 2 Mar 2022 15:28:32 +0800
From:   Wen Gu <guwen@...ux.alibaba.com>
To:     "D. Wythe" <alibuda@...ux.alibaba.com>, kgraul@...ux.ibm.com
Cc:     kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net] net/smc: fix unexpected SMC_CLC_DECL_ERR_REGRMB error



在 2022/3/1 下午9:17, D. Wythe 写道:
> From: "D. Wythe" <alibuda@...ux.alibaba.com>
> 
> Remove connections from link group is not synchronous with handling
> SMC_LLC_DELETE_RKEY, which means that even the number of connections is
> less that SMC_RMBS_PER_LGR_MAX, it does not mean that the connection can
> register rtoken successfully later, in other words, the rtoken entry may
> have not been released. This will cause an unexpected
> SMC_CLC_DECL_ERR_REGRMB to be reported, and then ths smc connection have
> to fallback to TCP.
> 


IMHO, if there are SMC_RMBS_PER_LGR_MAX connections in the link group now,
one of them is being removed and here comes a new connection at this moment,
then:

(1) without this patch, the new connection will be added into the old link group
     but fallback if the removing connection has not finished unregistering its rmb.

(2) with this patch, a new link group will be created and the new connection
     will be added into the new link group.

I am wondering if (1) should be considered as a issue, or just a bydesign?
If it is a issue, I think this patch works, Thanks!

Reviewed-by: Wen Gu <guwen@...ux.alibaba.com>

Best Regards,
Wen Gu