linux-kernel - Re: [PATCH] IB/cm: Remove unused and erroneous msg sequence encoding

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Date:   Mon, 9 Jul 2018 11:42:17 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Håkon Bugge <haakon.bugge@...cle.com>
Cc:     Doug Ledford <dledford@...hat.com>,
        Don Hiatt <don.hiatt@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Sean Hefty <sean.hefty@...el.com>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] IB/cm: Remove unused and erroneous msg sequence encoding

On Wed, Jul 04, 2018 at 12:48:01PM +0200, Håkon Bugge wrote:
> In cm_form_tid(), a two bit message sequence number is OR'ed into bit
> 31-30 of the lower TID value.
> 
> After commit f06d26537559 ("IB/cm: Randomize starting comm ID"), the
> local_id is XOR'ed with a 32-bit random value. Hence, bit 31-30 in the
> lower TID now has an arbitrarily value and it makes no sense to OR in
> the message sequence number.
> 
> Adding to that, the evolution in use of IDR routines in cm_alloc_id()
> has always had the possibility of returning a value with bit 30 set.
> 
> In addition, said bits are never checked.
> 
> Hence, remove the encoding and the corresponding enum.
> 
> Signed-off-by: Håkon Bugge <haakon.bugge@...cle.com>
> ---
>  drivers/infiniband/core/cm.c      | 14 ++++++--------
>  drivers/infiniband/core/cm_msgs.h |  7 -------
>  2 files changed, 6 insertions(+), 15 deletions(-)

Applied to for-next, thanks

I suspect the bits were probably added long ago for debugging..

Jason