linux-kernel - Re: [PATCH 1/2] scatterlist: add sg

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Message-ID: <20120926163851.GP16296@google.com>
Date:	Wed, 26 Sep 2012 09:38:51 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Maxim Levitsky <maximlevitsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alex Dubov <oakad@...oo.com>, linux-kernel@...r.kernel.org,
	Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH 1/2] scatterlist: add sg_nents

(cc'ing Jens)

On Wed, Sep 26, 2012 at 11:49:00AM +0200, Maxim Levitsky wrote:
> Useful helper to know the number of entries in scatterlist.
> 
> Signed-off-by: Maxim Levitsky <maximlevitsky@...il.com>
> ---
>  include/linux/scatterlist.h |    1 +
>  lib/scatterlist.c           |   22 ++++++++++++++++++++++
>  2 files changed, 23 insertions(+)
> 
> diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
> index 7b600da..4bd6c06 100644
> --- a/include/linux/scatterlist.h
> +++ b/include/linux/scatterlist.h
> @@ -201,6 +201,7 @@ static inline void *sg_virt(struct scatterlist *sg)
>  	return page_address(sg_page(sg)) + sg->offset;
>  }
>  
> +int sg_nents(struct scatterlist *sg);
>  struct scatterlist *sg_next(struct scatterlist *);
>  struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
>  void sg_init_table(struct scatterlist *, unsigned int);
> diff --git a/lib/scatterlist.c b/lib/scatterlist.c
> index e76d85c..5cd9cdc 100644
> --- a/lib/scatterlist.c
> +++ b/lib/scatterlist.c
> @@ -39,6 +39,28 @@ struct scatterlist *sg_next(struct scatterlist *sg)
>  EXPORT_SYMBOL(sg_next);
>  
>  /**
> + * sg_nents - return total count of entries in scatterlist
> + * @sg:		The scatterlist
> + *
> + * Description:
> + * Allows to know how many entries are in sg, taking into acount
> + * chaining as well
> + *
> + **/
> +int sg_nents(struct scatterlist *sg)
> +{
> +	int nents = 0;
> +	while (sg) {
> +		nents++;
> +		sg = sg_next(sg);
> +	}
> +
> +	return nents;
> +}
> +EXPORT_SYMBOL(sg_nents);

How about the following instead?

	for (nents = 0; sg; sg = sg_next(sg))
		nents++;
	return nents;

Other than that,

 Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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