Re: [PATCH 07/19] block: simplify bio_map_kern

On 5/1/25 06:21, Christoph Hellwig wrote:
> Rewrite bio_map_kern using the new bio_add_* helpers and drop the
> kerneldoc comment that is superfluous for an internal helper.
> 
> Signed-off-by: Christoph Hellwig <[email protected]>


Looks good to me.

Reviewed-by: Damien Le Moal <[email protected]>

One nit below.

> ---
>  block/blk-map.c | 56 ++++++++-----------------------------------------
>  1 file changed, 9 insertions(+), 47 deletions(-)
> 
> diff --git a/block/blk-map.c b/block/blk-map.c
> index ca6b55ac0da1..0bc823b168e4 100644
> --- a/block/blk-map.c
> +++ b/block/blk-map.c
> @@ -317,64 +317,26 @@ static void bio_map_kern_endio(struct bio *bio)
>  	kfree(bio);
>  }
>  
> -/**
> - *	bio_map_kern	-	map kernel address into bio
> - *	@data: pointer to buffer to map
> - *	@len: length in bytes
> - *	@op: bio/request operation
> - *	@gfp_mask: allocation flags for bio allocation
> - *
> - *	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(void *data, unsigned int len,
> -		enum req_op op, gfp_t gfp_mask)
> +static struct bio *bio_map_kern(void *data, unsigned int len, enum req_op op,
> +		gfp_t gfp_mask)
>  {
> -	unsigned long kaddr = (unsigned long)data;
> -	unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
> -	unsigned long start = kaddr >> PAGE_SHIFT;
> -	const int nr_pages = end - start;
> -	bool is_vmalloc = is_vmalloc_addr(data);
> -	struct page *page;
> -	int offset, i;
> +	unsigned int nr_vecs = bio_add_max_vecs(data, len);
>  	struct bio *bio;
>  
> -	bio = bio_kmalloc(nr_pages, gfp_mask);
> +	bio = bio_kmalloc(nr_vecs, gfp_mask);

This may also fail if nr_vecs is larger than UIO_MAXIOV, in which case, the
ENOMEM error may not really be appropriate. I guess we can sort this out
separately though.

>  	if (!bio)
>  		return ERR_PTR(-ENOMEM);
> -	bio_init(bio, NULL, bio->bi_inline_vecs, nr_pages, op);



-- 
Damien Le Moal
Western Digital Research