Re: [PATCH 2/3] block: make __blkdev_issue_zero_pages() less confusing

[Hannes Reinecke <hare@suse.de>]

On 12/6/20 6:53 AM, Tom Yan wrote:
> Instead of using the same check for the two layers of loops, count
> bio pages in the inner loop instead.
> 
> Signed-off-by: Tom Yan <tom.ty89@gmail.com>
> ---
>   block/blk-lib.c | 11 +++++------
>   1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/block/blk-lib.c b/block/blk-lib.c
> index c1e9388a8fb8..354dcab760c7 100644
> --- a/block/blk-lib.c
> +++ b/block/blk-lib.c
> @@ -318,7 +318,7 @@ static int __blkdev_issue_zero_pages(struct block_device *bdev,
>   	struct request_queue *q = bdev_get_queue(bdev);
>   	struct bio *bio = *biop;
>   	int bi_size = 0;
> -	unsigned int sz;
> +	unsigned int sz, bio_nr_pages;
>   
>   	if (!q)
>   		return -ENXIO;
> @@ -327,19 +327,18 @@ static int __blkdev_issue_zero_pages(struct block_device *bdev,
>   		return -EPERM;
>   
>   	while (nr_sects != 0) {
> -		bio = blk_next_bio(bio, __blkdev_sectors_to_bio_pages(nr_sects),
> -				   gfp_mask);
> +		bio_nr_pages = __blkdev_sectors_to_bio_pages(nr_sects);
> +		bio = blk_next_bio(bio, bio_nr_pages, gfp_mask);
>   		bio->bi_iter.bi_sector = sector;
>   		bio_set_dev(bio, bdev);
>   		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
>   
> -		while (nr_sects != 0) {
> +		while (bio_nr_pages != 0) {
>   			sz = min((sector_t) PAGE_SIZE, nr_sects << 9);

nr_sects will need to be modified, too, if we iterate over bio_nr_pages 
instead of nr_sects.

>   			bi_size = bio_add_page(bio, ZERO_PAGE(0), sz, 0);
>   			nr_sects -= bi_size >> 9;
>   			sector += bi_size >> 9;
> -			if (bi_size < sz)
> -				break;
> +			bio_nr_pages--;
>   		}
>   		cond_resched();
>   	}
> 

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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