linux-kernel - Re: [PATCH] IBcore/CM: Issue DREQ when receiving REQ/REP for stale QP

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Date:   Wed, 14 Dec 2016 12:55:41 -0500
From:   Doug Ledford <dledford@...hat.com>
To:     Hans Westgaard Ry <hans.westgaard.ry@...cle.com>,
        Sean Hefty <sean.hefty@...el.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>,
        Matan Barak <matanb@...lanox.com>,
        Erez Shitrit <erezsh@...lanox.com>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        Hakon Bugge <haakon.bugge@...cle.com>,
        Yuval Shaia <yuval.shaia@...cle.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] IBcore/CM: Issue DREQ when receiving REQ/REP for stale QP

On 10/28/2016 7:14 AM, Hans Westgaard Ry wrote:
> from "InfiBand Architecture Specifications Volume 1":
> 
>   A QP is said to have a stale connection when only one side has
>   connection information. A stale connection may result if the remote CM
>   had dropped the connection and sent a DREQ but the DREQ was never
>   received by the local CM. Alternatively the remote CM may have lost
>   all record of past connections because its node crashed and rebooted,
>   while the local CM did not become aware of the remote node's reboot
>   and therefore did not clean up stale connections.
> 
> and:
> 
>    A local CM may receive a REQ/REP for a stale connection. It shall
>    abort the connection issuing REJ to the REQ/REP. It shall then issue
>    DREQ with "DREQ:remote QPN” set to the remote QPN from the REQ/REP.
> 
> This patch solves a problem with reuse of QPN. Current codebase, that
> is IPoIB, relies on a REAP-mechanism to do cleanup of the structures
> in CM. A problem with this is the timeconstants governing this
> mechanism; they are up to 768 seconds and the interface may look
> inresponsive in that period.  Issuing a DREQ (and receiving a DREP)
> does the necessary cleanup and the interface comes up.
> 
> Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@...cle.com>
> Reviewed-by: Håkon Bugge <haakon.bugge@...cle.com>

Thanks, applied.


-- 
Doug Ledford <dledford@...hat.com>
    GPG Key ID: 0E572FDD



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