From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH 2/3] xen-scsiback: One function call less in
 scsiback_device_action() after error detection
Date: Wed, 20 Jul 2016 06:35:40 +0200
Message-ID: <83b0b1e2-900b-eefc-160b-7d837730571c@suse.com>
References: <5307CAA2.8060406@users.sourceforge.net>
 <530A086E.8010901@users.sourceforge.net>
 <alpine.DEB.2.02.1402231635510.1985@localhost6.localdomain6>
 <530A72AA.3000601@users.sourceforge.net>
 <alpine.DEB.2.02.1402240658210.2090@localhost6.localdomain6>
 <530B5FB6.6010207@users.sourceforge.net>
 <alpine.DEB.2.10.1402241710370.2074@hadrien>
 <530C5E18.1020800@users.sourceforge.net>
 <alpine.DEB.2.10.1402251014170.2080@hadrien>
 <530CD2C4.4050903@users.sourceforge.net>
 <alpine.DEB.2.10.1402251840450.7035@hadrien>
 <530CF8FF.8080600@users.sourceforge.net>
 <alpine.DEB.2.02.1402252117150.2047@localhost6.localdomain6>
 <530DD06F.4090703@users.sourceforge.net>
 <alpine.DEB.2.02.1402262129250.2221@localhost6.localdomain6>
 <5317A59D.4@users.sourceforge.net>
 <59e51c7d-f7bb-c55f-d2fe-06dccfef6a99@users.sourceforge.net>
 <87e55a72-71ad-d0a1-b936-12565bbc6508@users.sourceforge.net>
 <fb5824ad-fb09-e471-7dc4-3e32564cc334@suse.com>
 <8806e9cb-4200-8154-7914-6735805dfbe0@users.sourceforge.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Return-path: <kernel-janitors-owner@vger.kernel.org>
In-Reply-To: <8806e9cb-4200-8154-7914-6735805dfbe0@users.sourceforge.net>
Sender: kernel-janitors-owner@vger.kernel.org
To: SF Markus Elfring <elfring@users.sourceforge.net>
Cc: xen-devel@lists.xenproject.org, linux-scsi@vger.kernel.org, David Vrabel <david.vrabel@citrix.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, LKML <linux-kernel@vger.kernel.org>, kernel-janitors@vger.kernel.org, Julia Lawall <julia.lawall@lip6.fr>
List-Id: linux-scsi@vger.kernel.org

On 19/07/16 16:56, SF Markus Elfring wrote:
>>> @@ -606,7 +606,7 @@ static void scsiback_device_action(struct vscsibk_pend *pending_req,
>>>  	tmr = kzalloc(sizeof(struct scsiback_tmr), GFP_KERNEL);
>>>  	if (!tmr) {
>>>  		target_put_sess_cmd(se_cmd);
>>> -		goto err;
>>> +		goto do_resp;
>>>  	}
>>
>> Hmm, I'm not convinced this is an improvement.
>>
>> I'd rather rename the new error label to "put_cmd" and get rid of the
>> braces in above if statement:
>>
>> -	if (!tmr) {
>> -		target_put_sess_cmd(se_cmd);
>> -		goto err;
>> -	}
>> +	if (!tmr)
>> +		goto put_cmd;
>>
>> and then in the error path:
>>
>> -err:
>> +put_cmd:
>> +	target_put_sess_cmd(se_cmd);
> 
> I am unsure on the relevance of this function on such a source position.
> Would it make sense to move it further down at the end?

You only want to call it in the first error case (allocation failure).

>> +free_tmr:
>> 	kfree(tmr);
> 
> How do you think about to skip this function call after a memory
> allocation failure?

I think this just doesn't matter. If it were a hot path, yes. But trying
to do micro-optimizations in an error path is just not worth the effort.

I like a linear error path containing all the needed cleanups best.


Juergen