linux-kernel - Re: [PATCH v2 11/12] md/raid5: Check all disks in a stripe

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Message-ID: <7f61aacd-d378-092c-1291-f2aaf42a5537@linux.dev>
Date:   Wed, 27 Apr 2022 09:53:16 +0800
From:   Guoqing Jiang <guoqing.jiang@...ux.dev>
To:     Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        Song Liu <song@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <Martin.Oliveira@...eticom.com>,
        David Sloan <David.Sloan@...eticom.com>
Subject: Re: [PATCH v2 11/12] md/raid5: Check all disks in a stripe_head for
 reshape progress



On 4/21/22 3:54 AM, Logan Gunthorpe wrote:
> When testing if a previous stripe has had reshape expand past it, use
> the earliest or latest logical sector in all the disks for that stripe
> head. This will allow adding multiple disks at a time in a subesquent
> patch.
>
> To do this cleaner, refactor the check into a helper function called
> stripe_ahead_of_reshape().
>
> Signed-off-by: Logan Gunthorpe<logang@...tatee.com>
> ---
>   drivers/md/raid5.c | 55 ++++++++++++++++++++++++++++++++++------------
>   1 file changed, 41 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 1fa82d8fa89e..40a25c4b80bd 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -5823,6 +5823,42 @@ static bool ahead_of_reshape(struct mddev *mddev, sector_t sector,
>   		return sector >= reshape_sector;
>   }
>   
> +static bool range_ahead_of_reshape(struct mddev *mddev, sector_t min,
> +				   sector_t max, sector_t reshape_sector)
> +{
> +	if (mddev->reshape_backwards)
> +		return max < reshape_sector;
> +	else
> +		return min >= reshape_sector;
> +}
> +
> +static bool stripe_ahead_of_reshape(struct mddev *mddev, struct r5conf *conf,
> +				    struct stripe_head *sh)
> +{
> +	sector_t max_sector = 0, min_sector = MaxSector;
> +	bool ret = false;
> +	int dd_idx;
> +
> +	for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) {
> +		if (dd_idx == sh->pd_idx)
> +			continue;
> +
> +		min_sector = min(min_sector, sh->dev[dd_idx].sector);
> +		max_sector = min(max_sector, sh->dev[dd_idx].sector);
> +	}
> +
> +	spin_lock_irq(&conf->device_lock);
> +
> +	if (!range_ahead_of_reshape(mddev, min_sector, max_sector,
> +				     conf->reshape_progress))
> +		/* mismatch, need to try again */
> +		ret = true;

I think we can just open code range_ahead_of_reshape.

And seems the above is not same as below original checking which compare
logical_sector with reshape_progress. Is it intentional or am I miss 
something?

...

> -		int must_retry = 0;
> -		spin_lock_irq(&conf->device_lock);
> -		if (!ahead_of_reshape(mddev, logical_sector,
> -				      conf->reshape_progress))
> -			/* mismatch, need to try again */
> -			must_retry = 1;
> -		spin_unlock_irq(&conf->device_lock);
> -		if (must_retry) {
> -			raid5_release_stripe(sh);
> -			return STRIPE_SCHEDULE_AND_RETRY;
> -		}
> +		raid5_release_stripe(sh);
> +		return STRIPE_SCHEDULE_AND_RETRY;
>   	}
>   
>   	if (read_seqcount_retry(&conf->gen_lock, seq)) {

Thanks,
Guoqing