linux-kernel - Re: [RFC PATCH v4 1/3] block: export bio_map

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Date:   Mon, 4 Jan 2021 12:15:38 +0000
From:   Damien Le Moal <Damien.LeMoal@....com>
To:     SelvaKumar S <selvakuma.s1@...sung.com>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>
CC:     "kbusch@...nel.org" <kbusch@...nel.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        Johannes Thumshirn <Johannes.Thumshirn@....com>,
        "hch@....de" <hch@....de>, "sagi@...mberg.me" <sagi@...mberg.me>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "mpatocka@...hat.com" <mpatocka@...hat.com>,
        "hare@...e.de" <hare@...e.de>,
        "dm-devel@...hat.com" <dm-devel@...hat.com>,
        "snitzer@...hat.com" <snitzer@...hat.com>,
        "selvajove@...il.com" <selvajove@...il.com>,
        "nj.shetty@...sung.com" <nj.shetty@...sung.com>,
        "joshi.k@...sung.com" <joshi.k@...sung.com>,
        "javier.gonz@...sung.com" <javier.gonz@...sung.com>
Subject: Re: [RFC PATCH v4 1/3] block: export bio_map_kern()

On 2021/01/04 19:48, SelvaKumar S wrote:
> Export bio_map_kern() so that copy offload emulation can use
> it to add vmalloced memory to bio.
> 
> Signed-off-by: SelvaKumar S <selvakuma.s1@...sung.com>
> ---
>  block/blk-map.c        | 3 ++-
>  include/linux/blkdev.h | 2 ++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blk-map.c b/block/blk-map.c
> index 21630dccac62..50d61475bb68 100644
> --- a/block/blk-map.c
> +++ b/block/blk-map.c
> @@ -378,7 +378,7 @@ static void bio_map_kern_endio(struct bio *bio)
>   *	Map the kernel address into a bio suitable for io to a block
>   *	device. Returns an error pointer in case of error.
>   */
> -static struct bio *bio_map_kern(struct request_queue *q, void *data,
> +struct bio *bio_map_kern(struct request_queue *q, void *data,
>  		unsigned int len, gfp_t gfp_mask)
>  {
>  	unsigned long kaddr = (unsigned long)data;
> @@ -428,6 +428,7 @@ static struct bio *bio_map_kern(struct request_queue *q, void *data,
>  	bio->bi_end_io = bio_map_kern_endio;
>  	return bio;
>  }
> +EXPORT_SYMBOL(bio_map_kern);

Simple copy support is a block layer code, so you I do not think you need this.
You only need to remove the static declaration of the function.

>  
>  static void bio_copy_kern_endio(struct bio *bio)
>  {
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 070de09425ad..81f9e7bec16c 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -936,6 +936,8 @@ extern int blk_rq_map_user(struct request_queue *, struct request *,
>  			   struct rq_map_data *, void __user *, unsigned long,
>  			   gfp_t);
>  extern int blk_rq_unmap_user(struct bio *);
> +extern struct bio *bio_map_kern(struct request_queue *q, void *data,
> +				unsigned int len, gfp_t gfp_mask);
>  extern int blk_rq_map_kern(struct request_queue *, struct request *, void *, unsigned int, gfp_t);
>  extern int blk_rq_map_user_iov(struct request_queue *, struct request *,
>  			       struct rq_map_data *, const struct iov_iter *,
> 


-- 
Damien Le Moal
Western Digital Research