Re: [PATCH] bcache: remove the redundant judgment on bi_size

From: Xifengfei
Date: Mon Aug 30 2021 - 02:24:26 EST


Thanks a lot. I understand the purpose.
So is the original judgment process too complicated? Can we judge bi_size directly? This will be more concise

@@ -423,7 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
add_sequential(task);
i->sequential = 0;
found:
- if (i->sequential + bio->bi_iter.bi_size > i->sequential)
+ if (!bio->bi_iter.bi_size)
i->sequential += bio->bi_iter.bi_size;

i->last = bio_end_sector(bio);

Thanks
Fengfei

-----邮件原件-----
发件人: Coly Li [mailto:colyli@xxxxxxx]
发送时间: 2021年8月29日 15:50
收件人: xifengfei (RD) <xi.fengfei@xxxxxxx>
抄送: linux-bcache@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; kent.overstreet@xxxxxxxxx
主题: Re: [PATCH] bcache: remove the redundant judgment on bi_size

On 8/29/21 12:49 PM, Fengfei Xi wrote:
> The bi_size is unsigned int type data not less than 0, so we can
> directly add bi_size without extra judgment
>
> Signed-off-by: Fengfei Xi <xi.fengfei@xxxxxxx>

NACK. The check is necessary to avoid redundant and unnecessary memory write.

Coly Li

> ---
> drivers/md/bcache/request.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
> index 6d1de889b..2788eec3a 100644
> --- a/drivers/md/bcache/request.c
> +++ b/drivers/md/bcache/request.c
> @@ -423,9 +423,7 @@ static bool check_should_bypass(struct cached_dev *dc, struct bio *bio)
> add_sequential(task);
> i->sequential = 0;
> found:
> - if (i->sequential + bio->bi_iter.bi_size > i->sequential)
> - i->sequential += bio->bi_iter.bi_size;
> -
> + i->sequential += bio->bi_iter.bi_size;
> i->last = bio_end_sector(bio);
> i->jiffies = jiffies + msecs_to_jiffies(5000);
> task->sequential_io = i->sequential;