linux-kernel - RE: [PATCH V3 3/7] Drivers: hv: vmbus: add APIs to send/recv hvsock packet and get the r/w-ability

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Message-ID: <75f1792c788e418eaddc0d6b7e3381de@SIXPR30MB031.064d.mgd.msft.net>
Date:	Thu, 23 Jul 2015 03:05:16 +0000
From:	Dexuan Cui <decui@...rosoft.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	Vitaly Kuznetsov <vkuznets@...hat.com>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"pebolle@...cali.nl" <pebolle@...cali.nl>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>,
	"stefanha@...hat.com" <stefanha@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"apw@...onical.com" <apw@...onical.com>,
	"davem@...emloft.net" <davem@...emloft.net>
Subject: RE: [PATCH V3 3/7] Drivers: hv: vmbus: add APIs to send/recv hvsock
 packet and get the r/w-ability

> From: Dan Carpenter
> Sent: Wednesday, July 22, 2015 18:36
> To: Dexuan Cui
> On Wed, Jul 22, 2015 at 10:09:10AM +0000, Dexuan Cui wrote:
> > > I'd suggest you do something like
> > >
> > >     if (ret == -EAGIAIN)
> > >         return 0;
> > >     else if (ret)
> > >         return ret;
> > >
> > > to make it future-proof (e.g. when a new error is returned by
> > > hv_ringbuffer_peek). And a comment would also be useful as it is unclear
> > > why we silence errors here.
> > Hi Vitaly,
> > Thanks!
> > I think I made a mistake here:
> > the "if (ret != 0) return 0;" should be changed
> > to   "if (ret != 0) return ret;"
Usually 0 means success to me, so 
to me, "ret != 0" reads like "ret is not successful" and seems natural. 

The kind of usage is not rare in the kernel code:

decui@lin:~/linux-next$ grep 'if (ret != 0)' kernel/ include/ ipc/  -r  | wc -l
28
decui@lin:~/linux-next$ grep 'if (ret != 0)' drivers/   -r  | wc -l
1031
 
> The double negative really doesn't not make the code more complicated.
> I like using a quadruple negative instead.
> 
> 	if (ret != 0 != 0)
> 		return ret;
> dan carpenter
Hi Dan, I read this as a humor.  :-)

I'll take the suggestion and remember to use this in V4 and in future:
 
if (ret)
	return ret;

Thanks!

-- Dexuan

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