linux-kernel - Re: [PATCH v2 1/4] md/raid10: cleanup wait

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Date:   Wed, 14 Sep 2022 08:36:43 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     song@...nel.org, logang@...tatee.com, guoqing.jiang@...ux.dev,
        linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com
Subject: Re: [PATCH v2 1/4] md/raid10: cleanup wait_barrier()

Dear Yu,


Thank you for the improved patch. Three minor nits.

Am 14.09.22 um 03:49 schrieb Yu Kuai:
> From: Yu Kuai <yukuai3@...wei.com>

In the summary/title, I’d spell *Clean up* with a space. Maybe even use:

md/raid10: Factor out code from wait_barrier() to stop_waiting_barrier()

> Currently the nasty condition is wait_barrier() is hard to read. This
> patch factor out the condition into a function.

The first *is* above can be removed, and factor*s* needs an s.
> There are no functional changes.
> 
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>   drivers/md/raid10.c | 56 ++++++++++++++++++++++++++-------------------
>   1 file changed, 32 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 64d6e4cd8a3a..56458a53043d 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -957,44 +957,52 @@ static void lower_barrier(struct r10conf *conf)
>   	wake_up(&conf->wait_barrier);
>   }
>   
> +static bool stop_waiting_barrier(struct r10conf *conf)
> +{
> +	/* barrier is dropped */
> +	if (!conf->barrier)
> +		return true;
> +
> +	/*
> +	 * If there are already pending requests (preventing the barrier from
> +	 * rising completely), and the pre-process bio queue isn't empty, then
> +	 * don't wait, as we need to empty that queue to get the nr_pending
> +	 * count down.
> +	 */
> +	if (atomic_read(&conf->nr_pending)) {
> +		struct bio_list *bio_list = current->bio_list;
> +
> +		if (bio_list && (!bio_list_empty(&bio_list[0]) ||
> +				 !bio_list_empty(&bio_list[1])))
> +			return true;
> +	}
> +
> +	/* move on if recovery thread is blocked by us */
> +	if (conf->mddev->thread->tsk == current &&
> +	    test_bit(MD_RECOVERY_RUNNING, &conf->mddev->recovery) &&
> +	    conf->nr_queued > 0)
> +		return true;
> +
> +	return false;
> +}
> +
>   static bool wait_barrier(struct r10conf *conf, bool nowait)
>   {
>   	bool ret = true;
>   
>   	spin_lock_irq(&conf->resync_lock);
>   	if (conf->barrier) {
> -		struct bio_list *bio_list = current->bio_list;
> -		conf->nr_waiting++;
> -		/* Wait for the barrier to drop.
> -		 * However if there are already pending
> -		 * requests (preventing the barrier from
> -		 * rising completely), and the
> -		 * pre-process bio queue isn't empty,
> -		 * then don't wait, as we need to empty
> -		 * that queue to get the nr_pending
> -		 * count down.
> -		 */
>   		/* Return false when nowait flag is set */
>   		if (nowait) {
>   			ret = false;
>   		} else {
> +			conf->nr_waiting++;
>   			raid10_log(conf->mddev, "wait barrier");
>   			wait_event_lock_irq(conf->wait_barrier,
> -					    !conf->barrier ||
> -					    (atomic_read(&conf->nr_pending) &&
> -					     bio_list &&
> -					     (!bio_list_empty(&bio_list[0]) ||
> -					      !bio_list_empty(&bio_list[1]))) ||
> -					     /* move on if recovery thread is
> -					      * blocked by us
> -					      */
> -					     (conf->mddev->thread->tsk == current &&
> -					      test_bit(MD_RECOVERY_RUNNING,
> -						       &conf->mddev->recovery) &&
> -					      conf->nr_queued > 0),
> +					    stop_waiting_barrier(conf),
>   					    conf->resync_lock);
> +			conf->nr_waiting--;
>   		}
> -		conf->nr_waiting--;
>   		if (!conf->nr_waiting)
>   			wake_up(&conf->wait_barrier);
>   	}

Acked-by: Paul Menzel <pmenzel@...gen.mpg.de>


Kind regards,

Paul