Re: [PATCHv4 7/9] block/bounce: count bytes instead of sectors

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 2022/05/26 10:06, 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>
> ---
> v3->v4:
> 
>   Use sector shift
> 
>   Add comment explaing the ALIGN_DOWN
> 
>   Use unsigned int type for counting bytes
> 
>  block/bounce.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/block/bounce.c b/block/bounce.c
> index 8f7b6fe3b4db..f6ae21ec2a70 100644
> --- a/block/bounce.c
> +++ b/block/bounce.c
> @@ -205,19 +205,25 @@ 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;
>  
> +	/*
> +	 * If the original has more than BIO_MAX_VECS biovecs, the total bytes
> +	 * may not be block size aligned. Align down to ensure both sides of
> +	 * the split bio are appropriately sized.
> +	 */
> +	sectors = ALIGN_DOWN(bytes, queue_logical_block_size(q)) >> SECTOR_SHIFT;
>  	if (sectors < bio_sectors(*bio_orig)) {
>  		bio = bio_split(*bio_orig, sectors, GFP_NOIO, &bounce_bio_split);
>  		bio_chain(bio, *bio_orig);

Looks good.

Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

-- 
Damien Le Moal
Western Digital Research