[PATCH] md: make md_flush_request() more readable

[PATCH] md: make md_flush_request() more readable

[linan666]

From: Li Nan <linan122@huawei.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.

Signed-off-by: Li Nan <linan122@huawei.com>
---
 drivers/md/md.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index aff9118ff697..509e5638cea1 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -654,15 +654,12 @@ 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. */
+		spin_unlock_irq(&mddev->lock);
 		if (bio->bi_iter.bi_size == 0)
 			/* an empty barrier - all done */
 			bio_endio(bio);
-- 
2.39.2

Re: [PATCH] md: make md_flush_request() more readable

[Christoph Hellwig]

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;
}

Re: [PATCH] md: make md_flush_request() more readable

[Li Nan]

在 2024/5/26 16:54, Christoph Hellwig 写道:
> 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;
> }

Yeah, it looks better. I will changed it in v2.

Thansk for your suggestion.

-- 
Thanks,
Nan