Re: [Xen-devel] [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible

From	David Vrabel <david.vrabel@citrix.com>
Newsgroups	linux.kernel
Subject	Re: [Xen-devel] [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible
Date	2016-07-07 12:50 +0200
Message-ID	<rSf2y-5Kz-45@gated-at.bofh.it> (permalink)
References	<rScxH-4ic-21@gated-at.bofh.it> <rSeJb-5D9-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 07/07/16 11:26, David Vrabel wrote:
> On 07/07/16 09:06, Jan Beulich wrote:
>> ... as being the simpler variant.
> [...]
>> --- 4.7-rc6-prefer-xenbus_write.orig/drivers/block/xen-blkback/xenbus.c
>> +++ 4.7-rc6-prefer-xenbus_write/drivers/block/xen-blkback/xenbus.c
>> @@ -617,9 +617,9 @@ static int xen_blkbk_probe(struct xenbus
>>  		goto fail;
>>  	}
>>  
>> -	err = xenbus_printf(XBT_NIL, dev->nodename,
>> -			    "feature-max-indirect-segments", "%u",
>> -			    MAX_INDIRECT_SEGMENTS);
>> +	err = xenbus_write(XBT_NIL, dev->nodename,
>> +			   "feature-max-indirect-segments",
>> +			   __stringify(MAX_INDIRECT_SEGMENTS));
> 
> Yuk :(
> 
> Now someone has to check both __stringify() and MAX_INDIRECT_SEGMENTS to
> work out what this actually looks like.

In particular, if we ended up with

#define MAX_INDIRECT_SEGMENTS 512u

or similar then the code is now wrong.

David

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[PATCH] xen-blkback: prefer xenbus_write() over  xenbus_printf() where possible "Jan Beulich" <JBeulich@suse.com> - 2016-07-07 10:10 +0200
  Re: [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf()  where possible Roger Pau Monne <roger.pau@citrix.com> - 2016-07-07 11:50 +0200
  Re: [Xen-devel] [PATCH] xen-blkback: prefer xenbus_write() over  xenbus_printf() where possible David Vrabel <david.vrabel@citrix.com> - 2016-07-07 12:30 +0200
    Re: [Xen-devel] [PATCH] xen-blkback: prefer xenbus_write() over  xenbus_printf() where possible David Vrabel <david.vrabel@citrix.com> - 2016-07-07 12:50 +0200

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