[PATCH]is_power_of_2-ufs/super.c

[PATCH]is_power_of_2-ufs/super.c

[vignesh babu]

Replacing (n & (n-1)) in the context of power of 2 checks
with is_power_of_2

Signed-off-by: vignesh babu <vignesh.babu@wipro.com>
--- 
diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index 22ff6ed..2b30116 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -87,6 +87,7 @@
 #include <linux/smp_lock.h>
 #include <linux/buffer_head.h>
 #include <linux/vfs.h>
+#include <linux/log2.h>
 
 #include "swab.h"
 #include "util.h"
@@ -854,7 +855,7 @@ magic_found:
 	uspi->s_fmask = fs32_to_cpu(sb, usb1->fs_fmask);
 	uspi->s_fshift = fs32_to_cpu(sb, usb1->fs_fshift);
 
-	if (uspi->s_fsize & (uspi->s_fsize - 1)) {
+	if (!is_power_of_2(uspi->s_fsize)) {
 		printk(KERN_ERR "ufs_read_super: fragment size %u is not a power of 2\n",
 			uspi->s_fsize);
 			goto failed;
@@ -869,7 +870,7 @@ magic_found:
 			uspi->s_fsize);
 		goto failed;
 	}
-	if (uspi->s_bsize & (uspi->s_bsize - 1)) {
+	if (!is_power_of_2(uspi->s_bsize)) {
 		printk(KERN_ERR "ufs_read_super: block size %u is not a power of 2\n",
 			uspi->s_bsize);
 		goto failed;

-- 
Vignesh Babu BM 
_____________________________________________________________ 
"Why is it that every time I'm with you, makes me believe in magic?"

Re: [PATCH]is_power_of_2-ufs/super.c

[Evgeniy Dushistov]

On Thu, Jun 14, 2007 at 01:39:18PM +0530, vignesh babu wrote:
> 
> 
> Replacing (n & (n-1)) in the context of power of 2 checks
> with is_power_of_2
> 
> Signed-off-by: vignesh babu <vignesh.babu@wipro.com>

Acked-by: Evgeniy Dushistov <dushistov@mail.ru>

> --- 
> diff --git a/fs/ufs/super.c b/fs/ufs/super.c
> index 22ff6ed..2b30116 100644
> --- a/fs/ufs/super.c
> +++ b/fs/ufs/super.c
> @@ -87,6 +87,7 @@
>  #include <linux/smp_lock.h>
>  #include <linux/buffer_head.h>
>  #include <linux/vfs.h>
> +#include <linux/log2.h>
>  
>  #include "swab.h"
>  #include "util.h"
> @@ -854,7 +855,7 @@ magic_found:
>  	uspi->s_fmask = fs32_to_cpu(sb, usb1->fs_fmask);
>  	uspi->s_fshift = fs32_to_cpu(sb, usb1->fs_fshift);
>  
> -	if (uspi->s_fsize & (uspi->s_fsize - 1)) {
> +	if (!is_power_of_2(uspi->s_fsize)) {
>  		printk(KERN_ERR "ufs_read_super: fragment size %u is not a power of 2\n",
>  			uspi->s_fsize);
>  			goto failed;
> @@ -869,7 +870,7 @@ magic_found:
>  			uspi->s_fsize);
>  		goto failed;
>  	}
> -	if (uspi->s_bsize & (uspi->s_bsize - 1)) {
> +	if (!is_power_of_2(uspi->s_bsize)) {
>  		printk(KERN_ERR "ufs_read_super: block size %u is not a power of 2\n",
>  			uspi->s_bsize);
>  		goto failed;
> 
> -- 
> Vignesh Babu BM 
> _____________________________________________________________ 
> "Why is it that every time I'm with you, makes me believe in magic?"
> 
> 
> 
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>  
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-- 
/Evgeniy

Re: [PATCH]is_power_of_2-ufs/super.c

[Johannes Weiner]

Hi,

On Thu, Jun 14, 2007 at 01:39:18PM +0530, vignesh babu wrote:
> Replacing (n & (n-1)) in the context of power of 2 checks
> with is_power_of_2

You might want to run

	egrep -R '([a-zA-Z0-9_.>]+) *& *\(\1 *- *1\)' /usr/src/linux

This does not match if the check is broken into multiple lines, though.
Still, 66 matches so far. Perhaps a big patch that removes most of these
occurrences would be more appropriate.

	Hannes

Re: [PATCH]is_power_of_2-ufs/super.c

[vignesh babu]

Thanks Hannes, Im on it...

On Mon, 2007-06-25 at 14:13 +0200, Johannes Weiner wrote:
> egrep -R '([a-zA-Z0-9_.>]+) *& *\(\1 *- *1\)' /usr/src/linux
-- 
Vignesh Babu BM 
_____________________________________________________________ 
"Why is it that every time I'm with you, makes me believe in magic?"

Re: [PATCH]is_power_of_2-ufs/super.c

[Robert P. J. Day]

On Mon, 25 Jun 2007, Johannes Weiner wrote:

> Hi,
>
> On Thu, Jun 14, 2007 at 01:39:18PM +0530, vignesh babu wrote:
> > Replacing (n & (n-1)) in the context of power of 2 checks
> > with is_power_of_2
>
> You might want to run
>
> 	egrep -R '([a-zA-Z0-9_.>]+) *& *\(\1 *- *1\)' /usr/src/linux
>
> This does not match if the check is broken into multiple lines,
> though. Still, 66 matches so far. Perhaps a big patch that removes
> most of these occurrences would be more appropriate.

this cleanup project is already well documented here:

http://fsdev.net/wiki/index.php?title=Power_of_2_stuff

and it's unlikely that you'd get a big patch in that tries to do all
of that at once.  it's much easier to do it a subsystem at a time.

rday

p.s.  that wiki page could probably use some updating.

-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://fsdev.net/wiki/index.php?title=Main_Page
========================================================================