Message-ID: <4D917D5A.5040502@fusionio.com>
Date: Tue, 29 Mar 2011 08:34:02 +0200
From: Jens Axboe <jaxboe@fusionio.com>
MIME-Version: 1.0
To: Linus Torvalds <torvalds@linux-foundation.org>
CC: "Stephen M. Cameron" <scameron@beardog.cce.hp.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [GIT PULL] block drivers for 2.6.39-rc
References: <4D8E36CC.7080707@fusionio.com> <AANLkTinpjfyrN0mCRZi8zPqd2=+=WGRRToFhc+MqBDSB@mail.gmail.com>
In-Reply-To: <AANLkTinpjfyrN0mCRZi8zPqd2=+=WGRRToFhc+MqBDSB@mail.gmail.com>
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On 2011-03-29 01:06, Linus Torvalds wrote:
> On Sat, Mar 26, 2011 at 11:56 AM, Jens Axboe <jaxboe@fusionio.com> wrote:
>> Hi Linus,
>>
>> This is the pull request for the block driver updates for 2.6.39. Two
>> things here:
>>
>> - Big drbd update, as per usual...
>> - cciss update.
> 
> Btw, that cciss thing causes a very annoying compiler warning:
> 
>   drivers/block/cciss.c: In function ?dev_show_unique_id?:
>   drivers/block/cciss.c:617:7: warning: ?sn[0]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[1]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[2]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[3]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[4]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[5]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[6]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[7]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[8]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[9]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[10]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[11]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[12]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[13]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[14]? may be used
> uninitialized in this function
>   drivers/block/cciss.c:617:7: warning: ?sn[15]? may be used
> uninitialized in this function
> 
> which is because the compiler doesn't really notice that those things
> are only used if the error return isn't being set.
> 
> So it's a compiler mis-feature, but the thing is, the warning could
> easily be avoided by just writing the code more prettily.
> 
> Just do the memcpy() unconditionally: we know that 'drv' is a valid
> pointer (we just loaded 'h' off it), and we're talking about a nice
> constant 16-byte copy.
> 
> IOW, a patch something like the attached.
> 
> Untested, but it looks really obvious. Hmm?

Looks good to me. I'm curious, you get a warning in dev_show_unique_id()
but not in dev_show_vendor() or any of the other following 4-5 functions
written in the same style?

My gcc here does not warn for any of them. But it is very convoluted for
what it does

-- 
Jens Axboe

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