linux-kernel - Re: [PATCH v2 09/17] IB/Verbs: Use helper cap_read_multi_sge() and reform svc_rdma

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Message-ID: <5524EC14.9030304@profitbricks.com>
Date:	Wed, 08 Apr 2015 10:51:32 +0200
From:	Michael Wang <yun.wang@...fitbricks.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Tom Talpey <tom@...pey.com>
CC:	Roland Dreier <roland@...nel.org>,
	Sean Hefty <sean.hefty@...el.com>, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Tom Tucker <tom@...ngridcomputing.com>,
	Steve Wise <swise@...ngridcomputing.com>,
	Hoang-Nam Nguyen <hnguyen@...ibm.com>,
	Christoph Raisch <raisch@...ibm.com>,
	Mike Marciniszyn <infinipath@...el.com>,
	Eli Cohen <eli@...lanox.com>,
	Faisal Latif <faisal.latif@...el.com>,
	Upinder Malhi <umalhi@...co.com>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Ira Weiny <ira.weiny@...el.com>,
	PJ Waskiewicz <pj.waskiewicz@...idfire.com>,
	Tatyana Nikolova <Tatyana.E.Nikolova@...el.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Jack Morgenstein <jackm@....mellanox.co.il>,
	Haggai Eran <haggaie@...lanox.com>,
	Ilya Nelkenbaum <ilyan@...lanox.com>,
	Yann Droneaud <ydroneaud@...eya.com>,
	Bart Van Assche <bvanassche@....org>,
	Shachar Raindel <raindel@...lanox.com>,
	Sagi Grimberg <sagig@...lanox.com>,
	Devesh Sharma <devesh.sharma@...lex.com>,
	Matan Barak <matanb@...lanox.com>,
	Moni Shoua <monis@...lanox.com>, Jiri Kosina <jkosina@...e.cz>,
	Selvin Xavier <selvin.xavier@...lex.com>,
	Mitesh Ahuja <mitesh.ahuja@...lex.com>,
	Li RongQing <roy.qing.li@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Alex Estrin <alex.estrin@...el.com>,
	Doug Ledford <dledford@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Erez Shitrit <erezsh@...lanox.com>,
	Tom Gundersen <teg@...m.no>,
	Chuck Lever <chuck.lever@...cle.com>
Subject: Re: [PATCH v2 09/17] IB/Verbs: Use helper cap_read_multi_sge() and
 reform svc_rdma_accept()

On 04/07/2015 07:42 PM, Jason Gunthorpe wrote:
[snip]
>>> @@ -992,8 +992,8 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
>>>  			dma_mr_acc = IB_ACCESS_LOCAL_WRITE;
>>>  		} else
>>>  			need_dma_mr = 0;
>>> -		break;
>>> -	case RDMA_TRANSPORT_IB:
>>> +	} else if (rdma_ib_mgmt(newxprt->sc_cm_id->device,
>>> +				newxprt->sc_cm_id->port_num)) {
>>>  		if (!(newxprt->sc_dev_caps & SVCRDMA_DEVCAP_FAST_REG)) {
>>>  			need_dma_mr = 1;
>>>  			dma_mr_acc = IB_ACCESS_LOCAL_WRITE;
>>
>> Now I'm even more confused. How is the presence of IB management
>> related to needing a privileged lmr?
> 
> Agree, this needs to be someone else. 
> 
> I think the test is probably based on this comment:
> 
>         * NB:  iWARP requires remote write access for the data sink
>         *      of an RDMA_READ. IB does not.
> 
> So the if should be:
> 
>           if (cap_rdma_read_needs_write(..) && 
> 	  !(newxprt->sc_dev_caps & SVCRDMA_DEVCAP_FAST_REG)) {
>                        need_dma_mr = 1;
>                        dma_mr_acc =
>                                (IB_ACCESS_LOCAL_WRITE |
>                                 IB_ACCESS_REMOTE_WRITE);
> 
> And the identical if blocks merged.
> 
> Plus the
> 	if (rdma_transport_iwarp(newxprt->sc_cm_id->device,
> 				 newxprt->sc_cm_id->port_num))
>   		newxprt->sc_dev_caps |= SVCRDMA_DEVCAP_READ_W_INV

Sounds good :-) I'll give this part a reform in next version.

Regards,
Michael Wang

> 
> Jason
> 
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