linux-kernel - Re: [PATCH for-next v3 0/2] Introduce rdma_set_min_rnr

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Message-ID: <YHWCgmq4gOmAczq6@unreal>
Date:   Tue, 13 Apr 2021 14:37:38 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Haakon Bugge <haakon.bugge@...cle.com>
Cc:     Jason Gunthorpe <jgg@...dia.com>,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Doug Ledford <dledford@...hat.com>,
        OFED mailing list <linux-rdma@...r.kernel.org>,
        Parav Pandit <parav@...dia.com>,
        Linux-Net <netdev@...r.kernel.org>,
        "rds-devel@....oracle.com" <rds-devel@....oracle.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH for-next v3 0/2] Introduce rdma_set_min_rnr_timer() and
 use it in RDS

On Tue, Apr 13, 2021 at 11:13:38AM +0000, Haakon Bugge wrote:
> 
> 
> > On 13 Apr 2021, at 08:29, Leon Romanovsky <leon@...nel.org> wrote:
> > 
> > On Mon, Apr 12, 2021 at 07:58:47PM -0300, Jason Gunthorpe wrote:
> >> On Wed, Mar 31, 2021 at 08:43:12PM +0200, Håkon Bugge wrote:
> >>> ib_modify_qp() is an expensive operation on some HCAs running
> >>> virtualized. This series removes two ib_modify_qp() calls from RDS.
> >>> 
> >>> I am sending this as a v3, even though it is the first sent to
> >>> net. This because the IB Core commit has reach v3.
> >>> 
> >>> Håkon Bugge (2):
> >>>  IB/cma: Introduce rdma_set_min_rnr_timer()
> >>>  rds: ib: Remove two ib_modify_qp() calls
> >> 
> >> Applied to rdma for-next, thanks
> > 
> > Jason,
> > 
> > It should be 
> > +	WARN_ON(id->qp_type != IB_QPT_RC && id->qp_type != IB_QPT_XRC_TGT);
> 
> With no return you will arm the setting of the timer and subsequently get an error from the modify_qp later.

The addition of WARN_ON() means that this is programmer error to get
such input. Historically, in-kernel API doesn't need to have protection
from other kernel developers.

Thanks

> 
> 
> Håkon
> 
> > 
> > and not
> > +	if (WARN_ON(id->qp_type != IB_QPT_RC && id->qp_type != IB_QPT_XRC_TGT))
> > +		return -EINVAL;
> > 
> > Thanks
> > 
> >> 
> >> Jason
>