linux-kernel - Re: [RFC] [PATCH v2 1/3] scatterlist: Add support to clone scatterlist

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Date:	Wed, 6 Jul 2016 15:45:33 +0530
From:	Sekhar Nori <nsekhar@...com>
To:	Franklin S Cooper Jr <fcooper@...com>, <david.s.gordon@...el.com>,
	<axboe@...com>, <akpm@...ux-foundation.org>,
	<ming.l@....samsung.com>, <linux-kernel@...r.kernel.org>,
	<broonie@...nel.org>, <linux-spi@...r.kernel.org>,
	<peter.ujfalusi@...com>
Subject: Re: [RFC] [PATCH v2 1/3] scatterlist: Add support to clone
 scatterlist

On Monday 27 June 2016 08:24 PM, Franklin S Cooper Jr wrote:

> +/*
> + * sg_table_clone - Duplicate an existing sg_table including chained sgl

This function should probably be called sg_clone_table() to be
consistent with sg_alloc_table(), sg_free_table() etc.

> + * @orig_table:     Original sg_table to be duplicated
> + * @len:            Total length of sg while taking chaining into account
> + * @gfp_mask:       GFP allocation mask
> + *
> + * Description:
> + *   Clone a sg_table along with chained sgl. This cloned copy may be
> + *   modified in some ways while keeping the original table and sgl in tact.
> + *   Also allow the cloned sgl copy to have a smaller length than the original
> + *   which may reduce the sgl total sg entries.
> + *
> + * Returns:
> + *   Pointer to new kmalloced sg_table, ERR_PTR() on error
> + *
> + */
> +struct sg_table *sg_table_clone(struct sg_table *orig_table, u64 len,
> +				gfp_t gfp_mask)
> +{
> +	struct sg_table	*table;
> +
> +	table = kmalloc(sizeof(struct sg_table), gfp_mask);

Can you use sg_alloc_table() to allocate the new table? The way you have
it now, it looks like users will need to use kfree() to free a cloned
table and use sg_free_table() otherwise. It will be nice if
sg_free_table() can be used consistently.

Regards,
Sekhar