linux-kernel - Re: [PATCH 03/12] drbd: remove RB_CONGESTED

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Date:   Thu, 17 Sep 2020 11:55:07 +0200
From:   Jan Kara <jack@...e.cz>
To:     Christoph Hellwig <hch@....de>
Cc:     Jens Axboe <axboe@...nel.dk>, Song Liu <song@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Richard Weinberger <richard@....at>,
        Minchan Kim <minchan@...nel.org>,
        linux-mtd@...ts.infradead.org, dm-devel@...hat.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        drbd-dev@...ts.linbit.com, linux-raid@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        cgroups@...r.kernel.org,
        Johannes Thumshirn <johannes.thumshirn@....com>
Subject: Re: [PATCH 03/12] drbd: remove RB_CONGESTED_REMOTE

On Thu 10-09-20 16:48:23, Christoph Hellwig wrote:
> This case isn't ever used.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>

Are you sure it's never used? As far as I'm reading drdb code the contents
of the disk_conf structure seems to be received through netlink (that code
is really a macro hell) and so read_balancing attribute passed to
remote_due_to_read_balancing() can have any value userspace passed to it.

								Honza

> ---
>  drivers/block/drbd/drbd_req.c | 4 ----
>  include/linux/drbd.h          | 1 -
>  2 files changed, 5 deletions(-)
> 
> diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
> index 5c975af9c15fb8..481bc34fcf386a 100644
> --- a/drivers/block/drbd/drbd_req.c
> +++ b/drivers/block/drbd/drbd_req.c
> @@ -901,13 +901,9 @@ static bool drbd_may_do_local_read(struct drbd_device *device, sector_t sector,
>  static bool remote_due_to_read_balancing(struct drbd_device *device, sector_t sector,
>  		enum drbd_read_balancing rbm)
>  {
> -	struct backing_dev_info *bdi;
>  	int stripe_shift;
>  
>  	switch (rbm) {
> -	case RB_CONGESTED_REMOTE:
> -		bdi = device->ldev->backing_bdev->bd_disk->queue->backing_dev_info;
> -		return bdi_read_congested(bdi);
>  	case RB_LEAST_PENDING:
>  		return atomic_read(&device->local_cnt) >
>  			atomic_read(&device->ap_pending_cnt) + atomic_read(&device->rs_pending_cnt);
> diff --git a/include/linux/drbd.h b/include/linux/drbd.h
> index 5755537b51b114..6a8286132751df 100644
> --- a/include/linux/drbd.h
> +++ b/include/linux/drbd.h
> @@ -94,7 +94,6 @@ enum drbd_read_balancing {
>  	RB_PREFER_REMOTE,
>  	RB_ROUND_ROBIN,
>  	RB_LEAST_PENDING,
> -	RB_CONGESTED_REMOTE,
>  	RB_32K_STRIPING,
>  	RB_64K_STRIPING,
>  	RB_128K_STRIPING,
> -- 
> 2.28.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR