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Groups > linux.kernel > #1438277 > unrolled thread

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

Started by"Jan Beulich" <JBeulich@suse.com>
First post2016-07-07 10:10 +0200
Last post2016-07-07 12:50 +0200
Articles 4 — 3 participants

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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

#1438277 — [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible

From"Jan Beulich" <JBeulich@suse.com>
Date2016-07-07 10:10 +0200
Subject[PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible
Message-ID<rScxH-4ic-21@gated-at.bofh.it>
... as being the simpler variant.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
 drivers/block/xen-blkback/xenbus.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- 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));
 	if (err)
 		dev_warn(&dev->dev,
 			 "writing %s/feature-max-indirect-segments (%d)",
@@ -850,7 +850,7 @@ again:
 
 	xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
 
-	err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
+	err = xenbus_write(xbt, dev->nodename, "feature-persistent", "1");
 	if (err) {
 		xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
 				 dev->nodename);

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#1438462 — Re: [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible

FromRoger Pau Monne <roger.pau@citrix.com>
Date2016-07-07 11:50 +0200
SubjectRe: [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible
Message-ID<rSe6t-59g-1@gated-at.bofh.it>
In reply to#1438277
On Thu, Jul 07, 2016 at 02:06:12AM -0600, Jan Beulich wrote:
> ... as being the simpler variant.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

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

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#1438502 — Re: [Xen-devel] [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible

FromDavid Vrabel <david.vrabel@citrix.com>
Date2016-07-07 12:30 +0200
SubjectRe: [Xen-devel] [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible
Message-ID<rSeJb-5D9-11@gated-at.bofh.it>
In reply to#1438277
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.

David

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#1438518 — Re: [Xen-devel] [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible

FromDavid Vrabel <david.vrabel@citrix.com>
Date2016-07-07 12:50 +0200
SubjectRe: [Xen-devel] [PATCH] xen-blkback: prefer xenbus_write() over xenbus_printf() where possible
Message-ID<rSf2y-5Kz-45@gated-at.bofh.it>
In reply to#1438502
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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