[dm-devel] [RFC v2 1/3] block: Introduce blk_bio_map_sg() to map one bio

[Jens Axboe]

On 05/27/2016 05:11 AM, Baolin Wang wrote:
> +/*
> + * Map a bio to scatterlist, return number of sg entries setup. Caller must
> + * make sure sg can hold bio segments entries.
> + */
> +int blk_bio_map_sg(struct request_queue *q, struct bio *bio,
> +		   struct scatterlist *sglist)
> +{
> +	struct scatterlist *sg = NULL;
> +	int nsegs = 0;
> +
> +	if (bio)
> +		nsegs = __blk_bios_map_sg(q, bio, sglist, &sg, true);
> +
> +	if (sg)
> +		sg_mark_end(sg);

Put that if (sg) inside the if (bio) section, 'sg' isn't going to be
non-NULL outside of that.

Additionally, who would call this with a NULL bio? That seems odd, I'd
get rid of that check completely.

-- 
Jens Axboe