linux-kernel - Re: [Xen-devel] [PATCH v2 05/20] block/xen-blkfront: Split blkif_queue

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Date:	Tue, 21 Jul 2015 12:12:12 +0100
From:	Julien Grall <julien.grall@...rix.com>
To:	Roger Pau Monné <roger.pau@...rix.com>,
	<xen-devel@...ts.xenproject.org>
CC:	<ian.campbell@...rix.com>, <stefano.stabellini@...citrix.com>,
	<linux-kernel@...r.kernel.org>,
	David Vrabel <david.vrabel@...rix.com>,
	"Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Xen-devel] [PATCH v2 05/20] block/xen-blkfront: Split blkif_queue_request
 in 2

Hi Roger,

On 21/07/15 10:54, Roger Pau Monné wrote:
> El 09/07/15 a les 22.42, Julien Grall ha escrit:
>> Currently, blkif_queue_request has 2 distinct execution path:
>>     - Send a discard request
>>     - Send a read/write request
>>
>> The function is also allocating grants to use for generating the
>> request. Although, this is only used for read/write request.
>>
>> Rather than having a function with 2 distinct execution path, separate
>> the function in 2. This will also remove one level of tabulation.
>>
>> Signed-off-by: Julien Grall <julien.grall@...rix.com>
>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
>> Cc: Roger Pau Monné <roger.pau@...rix.com>
>> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
>> Cc: David Vrabel <david.vrabel@...rix.com>
> 
> Patch looks fine, although with so much indentation changes it's kind of
> hard to review.

I wasn't sure how to make this patch more easy to review and it seems
like diff is getting confused.

It's mostly removing one indentation layer (the if (req->cmd_flags ...))
and move the discard code in a separate function.

> Acked-by: Roger Pau Monné <roger.pau@...rix.com>

Thank you.

> Just one minor change below.
> 
> [...]
> 
>> @@ -595,6 +603,24 @@ static int blkif_queue_request(struct request *req)
>>  	return 0;
>>  }
>>  
>> +/*
>> + * Generate a Xen blkfront IO request from a blk layer request.  Reads
>> + * and writes are handled as expected.
>> + *
>> + * @req: a request struct
>> + */
>> +static int blkif_queue_request(struct request *req)
>> +{
>> +	struct blkfront_info *info = req->rq_disk->private_data;
>> +
>> +	if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
>> +		return 1;
>> +
>> +	if (unlikely(req->cmd_flags & (REQ_DISCARD | REQ_SECURE)))
>> +		return blkif_queue_discard_req(req);
>> +	else
>> +		return blkif_queue_rw_req(req);
> 
> There's no need for the else clause.

I find it more readable and obvious to understand than:

if ( ... )
  return
return;

when there is only one line in the else. IIRC, the resulting assembly
will be the same.

Anyway, I can drop the else if you really want.

Regards,

-- 
Julien Grall
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