Re: [PATCH V12 14/20] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages()

[Omar Sandoval]

On Mon, Nov 26, 2018 at 10:17:14AM +0800, Ming Lei wrote:
> bch_bio_alloc_pages() is always called on one new bio, so it is safe
> to access the bvec table directly. Given it is the only kind of this
> case, open code the bvec table access since bio_for_each_segment_all()
> will be changed to support for iterating over multipage bvec.
> 
> Acked-by: Coly Li <colyli@xxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>

Reviewed-by: Omar Sandoval <osandov@xxxxxx>

> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
>  drivers/md/bcache/util.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
> index 20eddeac1531..62fb917f7a4f 100644
> --- a/drivers/md/bcache/util.c
> +++ b/drivers/md/bcache/util.c
> @@ -270,7 +270,11 @@ int bch_bio_alloc_pages(struct bio *bio, gfp_t gfp_mask)
>  	int i;
>  	struct bio_vec *bv;
>  
> -	bio_for_each_segment_all(bv, bio, i) {
> +	/*
> +	 * This is called on freshly new bio, so it is safe to access the
> +	 * bvec table directly.
> +	 */
> +	for (i = 0, bv = bio->bi_io_vec; i < bio->bi_vcnt; bv++, i++) {
>  		bv->bv_page = alloc_page(gfp_mask);
>  		if (!bv->bv_page) {
>  			while (--bv >= bio->bi_io_vec)
> -- 
> 2.9.5
>