Re: [PATCHv5 07/11] block/bounce: count bytes instead of sectors

[Eric Biggers <ebiggers@kernel.org>]

On Tue, May 31, 2022 at 12:11:33PM -0700, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> Individual bv_len's may not be a sector size.
> 
> Signed-off-by: Keith Busch <kbusch@kernel.org>
> Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
> Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
> v4->v5:
> 
>   Updated comment (Christoph)
> 
>  block/bounce.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/block/bounce.c b/block/bounce.c
> index 8f7b6fe3b4db..fbadf179601f 100644
> --- a/block/bounce.c
> +++ b/block/bounce.c
> @@ -205,19 +205,26 @@ void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig)
>  	int rw = bio_data_dir(*bio_orig);
>  	struct bio_vec *to, from;
>  	struct bvec_iter iter;
> -	unsigned i = 0;
> +	unsigned i = 0, bytes = 0;
>  	bool bounce = false;
> -	int sectors = 0;
> +	int sectors;
>  
>  	bio_for_each_segment(from, *bio_orig, iter) {
>  		if (i++ < BIO_MAX_VECS)
> -			sectors += from.bv_len >> 9;
> +			bytes += from.bv_len;
>  		if (PageHighMem(from.bv_page))
>  			bounce = true;
>  	}
>  	if (!bounce)
>  		return;
>  
> +	/*
> +	 * Individual bvecs may not be logical block aligned. Round down
> +	 * the split size so that each bio is properly sector size aligned,
> +	 * even if we do not use the full hardware limits.
> +	 */

Please write "might not" instead of "may not", since "may not" is ambiguous; it
sometimes means "are not allowed to".  Likewise in other patches.

"Sector size" is ambiguous as well.  I think you mean "logical block size"?

- Eric