linux-kernel - Re: [PATCH v2] md: make md_flush

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Message-ID: <8dc33d99-4b50-fdb7-e81b-581939dadeaa@huaweicloud.com>
Date: Tue, 28 May 2024 21:32:40 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: linan666@...weicloud.com, song@...nel.org
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
 yi.zhang@...wei.com, houtao1@...wei.com, yangerkun@...wei.com,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v2] md: make md_flush_request() more readable

Hi,

在 2024/05/29 4:31, linan666@...weicloud.com 写道:
> From: Li Nan <linan122@...wei.com>
> 
> Setting bio to NULL and checking 'if(!bio)' is redundant and looks strange,
> just consolidate them into one condition. There are no functional changes.
> 
> Suggested-by: Christoph Hellwig <hch@...radead.org>
> Signed-off-by: Li Nan <linan122@...wei.com>
> ---
> v2: Rewrite the code according to Christoph's suggestion.
> 
>   drivers/md/md.c | 28 +++++++++++++---------------
>   1 file changed, 13 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index aff9118ff697..9598b4898ea9 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -654,24 +654,22 @@ bool md_flush_request(struct mddev *mddev, struct bio *bio)
>   		WARN_ON(percpu_ref_is_zero(&mddev->active_io));
>   		percpu_ref_get(&mddev->active_io);
>   		mddev->flush_bio = bio;
> -		bio = NULL;
> -	}
> -	spin_unlock_irq(&mddev->lock);
> -
> -	if (!bio) {
> +		spin_unlock_irq(&mddev->lock);
>   		INIT_WORK(&mddev->flush_work, submit_flushes);
>   		queue_work(md_wq, &mddev->flush_work);
> -	} else {
> -		/* flush was performed for some other bio while we waited. */
> -		if (bio->bi_iter.bi_size == 0)
> -			/* an empty barrier - all done */
> -			bio_endio(bio);
> -		else {
> -			bio->bi_opf &= ~REQ_PREFLUSH;
> -			return false;
> -		}
> +		return true;
>   	}
> -	return true;
> +
> +	/* flush was performed for some other bio while we waited. */
> +	spin_unlock_irq(&mddev->lock);
> +	if (bio->bi_iter.bi_size == 0) {

It's better to use bio_sectors() here.

Thanks,
Kuai

> +		/* pure flush without data - all done */
> +		bio_endio(bio);
> +		return true;
> +	}
> +
> +	bio->bi_opf &= ~REQ_PREFLUSH;
> +	return false;
>   }
>   EXPORT_SYMBOL(md_flush_request);
>   
>