linux-kernel - Re: [PATCH v2] Staging: lustre: Use of fls to find last set bit

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Date:	Sat, 11 Jan 2014 12:02:48 -0800
From:	Joe Perches <joe@...ches.com>
To:	Monam Agarwal <monamagarwal123@...il.com>
Cc:	gregkh@...uxfoundation.org, andreas.dilger@...el.com,
	peter.p.waskiewicz.jr@...el.com, tao.peng@....com,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Staging: lustre: Use of fls to find last set bit

On Sun, 2014-01-12 at 01:02 +0530, Monam Agarwal wrote:
> This introduces fls in lustre/ldlm/ldlm_extent.c 
> to find the last set bit. 
[]
> Signed-off-by: Monam Agarwal <monamagarwal123@...il.com>
> ---
> Changes since v1:
> *Incorrect commit message
> *Use of fls function
[]
> diff --git a/drivers/staging/lustre/lustre/ldlm/ldlm_extent.c b/drivers/staging/lustre/lustre/ldlm/ldlm_extent.c
[]
> @@ -150,10 +150,12 @@ struct ldlm_interval *ldlm_interval_detach(struct ldlm_lock *l)
>  static inline int lock_mode_to_index(ldlm_mode_t mode)
>  {
>  	int index;
> +	int len;
>  
>  	LASSERT(mode != 0);
>  	LASSERT(IS_PO2(mode));
> -	for (index = -1; mode; index++, mode >>= 1) ;
> +	len = fls(mode);
> +	index = len-1;

There's no need for len at all.

	index = fls(mode) - 1;

would be fine.


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