linux-kernel - Re: [KJ][PATCH] is_power_of

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Date:	Tue, 20 Feb 2007 22:12:45 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Vignesh Babu BM <vignesh.babu@...ro.com>
Cc:	Kernel Janitors List <kernel-janitors@...ts.osdl.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [KJ][PATCH] is_power_of_2 in fat

Vignesh Babu BM <vignesh.babu@...ro.com> writes:

> Replacing (n & (n-1)) in the context of power of 2 checks
> with is_power_of_2
>
> Signed-off-by: vignesh babu <vignesh.babu@...ro.com>

Acked-by: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>

Thanks.

> --- 
> diff --git a/fs/fat/inode.c b/fs/fat/inode.c
> index a9e4688..8437190 100644
> --- a/fs/fat/inode.c
> +++ b/fs/fat/inode.c
> @@ -25,6 +25,7 @@
>  #include <linux/parser.h>
>  #include <linux/uio.h>
>  #include <linux/writeback.h>
> +#include <linux/log2.h>
>  #include <asm/unaligned.h>
>  
>  #ifndef CONFIG_FAT_DEFAULT_IOCHARSET
> @@ -1216,8 +1217,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent,
>  	}
>  	logical_sector_size =
>  		le16_to_cpu(get_unaligned((__le16 *)&b->sector_size));
> -	if (!logical_sector_size
> -	    || (logical_sector_size & (logical_sector_size - 1))
> +	if (!is_power_of_2(logical_sector_size)
>  	    || (logical_sector_size < 512)
>  	    || (PAGE_CACHE_SIZE < logical_sector_size)) {
>  		if (!silent)
> @@ -1227,8 +1227,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent,
>  		goto out_invalid;
>  	}
>  	sbi->sec_per_clus = b->sec_per_clus;
> -	if (!sbi->sec_per_clus
> -	    || (sbi->sec_per_clus & (sbi->sec_per_clus - 1))) {
> +	if (!is_power_of_2(sbi->sec_per_clus)) {
>  		if (!silent)
>  			printk(KERN_ERR "FAT: bogus sectors per cluster %u\n",
>  			       sbi->sec_per_clus);
>
> -- 
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
-
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