Received-SPF: pass (google.com: domain of linux-kernel+bounces-189613-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Date: Sun, 26 May 2024 01:54:07 -0700
From: Christoph Hellwig <hch@infradead.org>
To: linan666@huaweicloud.com
Cc: song@kernel.org, linux-raid@vger.kernel.org,
	linux-kernel@vger.kernel.org, yukuai3@huawei.com,
	yi.zhang@huawei.com, houtao1@huawei.com, yangerkun@huawei.com
Subject: Re: [PATCH] md: make md_flush_request() more readable
Message-ID: <ZlL4rxKqcV5ePLXu@infradead.org>
References: <20240525185622.3896616-1-linan666@huaweicloud.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240525185622.3896616-1-linan666@huaweicloud.com>

On Sun, May 26, 2024 at 02:56:22AM +0800, linan666@huaweicloud.com wrote:
> -		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. */
> +		spin_unlock_irq(&mddev->lock);
>  		if (bio->bi_iter.bi_size == 0)
>  			/* an empty barrier - all done */

This stil looks like a somwwhat odd flow  Why not go all the way
and turn it into:


	...
		queue_work(md_wq, &mddev->flush_work);
		return true;
	}

	/* flush was performed for some other bio while we waited. */
	spin_unlock_irq(&mddev->lock);
	if (bio->bi_iter.bi_size == 0) {
		/* pure flush without data - all done */
		bio_endio(bio);
		return true;
	}
	bio->bi_opf &= ~REQ_PREFLUSH;
	return false;
}