linux-kernel - Re: [PATCH v3 04/28] IB/Verbs: Reform IB-core cm

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Message-ID: <552CC6DF.8070704@profitbricks.com>
Date:	Tue, 14 Apr 2015 09:50:55 +0200
From:	Michael Wang <yun.wang@...fitbricks.com>
To:	"ira.weiny" <ira.weiny@...el.com>
CC:	Roland Dreier <roland@...nel.org>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	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>,
	Jack Morgenstein <jackm@....mellanox.co.il>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Haggai Eran <haggaie@...lanox.com>,
	Tom Talpey <tom@...pey.com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Doug Ledford <dledford@...hat.com>
Subject: Re: [PATCH v3 04/28] IB/Verbs: Reform IB-core cm



On 04/13/2015 08:12 PM, ira.weiny wrote:
[snip]
>> -
>> -	if (rdma_node_get_transport(ib_device->node_type) != RDMA_TRANSPORT_IB)
>> -		return;
>> +	int count = 0;
> 
> I'm ok with this as an intermediate patch but going forward if we are going to
> have calls like 
> 
> static inline int cap_ib_cm_dev(struct ib_device *device)

Actually I really don't want to introduce this kind of helper, it's slow, ugly
and break the consistency, but I can't find a good way to avoid that...

For example the check inside cma_listen_on_dev(), how could we do per-port check
while don't even know which port will be used later...

> 
> Then I think we should have similar calls like
> 
> cap_ib_mad_dev(device)
> 
> Which eliminates the clean up below...

I'd like to avoid using such helper as long as possible :-P

> 
>>  
>>  	cm_dev = kzalloc(sizeof(*cm_dev) + sizeof(*port) *
>>  			 ib_device->phys_port_cnt, GFP_KERNEL);
>> @@ -3783,6 +3781,9 @@ static void cm_add_one(struct ib_device *ib_device)
>>  
>>  	set_bit(IB_MGMT_METHOD_SEND, reg_req.method_mask);
>>  	for (i = 1; i <= ib_device->phys_port_cnt; i++) {
>> +		if (!rdma_ib_or_iboe(ib_device, i))
>> +			continue;
>> +
>>  		port = kzalloc(sizeof *port, GFP_KERNEL);
>>  		if (!port)
>>  			goto error1;
>> @@ -3809,7 +3810,16 @@ static void cm_add_one(struct ib_device *ib_device)
>>  		ret = ib_modify_port(ib_device, i, 0, &port_modify);
>>  		if (ret)
>>  			goto error3;
>> +
>> +		count++;
>>  	}
>> +
>> +	if (!count) {
>> +		device_unregister(cm_dev->device);
>> +		kfree(cm_dev);
>> +		return;
> 
> Here.
> 
> I worry about mistakes being made when we loop through only to find that none
> of the ports support the feature and then we have to clean up.  As this is
> initialization code I don't see any issue with looping through the ports 2
> times and making the code cleaner.

This style of logical could be found in other core module too, may be keep
consistent is not a bad idea?

After all, it's just initialization code which relatively rarely used :-)

Regards,
Michael Wang

> 
> This applies to the SA and CM modules as well.
> 
> However, in the ib_cm module you already have cap_ib_cm_dev(device) so you
> should use it at the start of cm_add_one.
> 
> Ira
> 
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