Re: [PATCH 2/9] blkcg, writeback: Add wbc->no_wbc_acct

From: Jan Kara <jack@suse.cz>
To: Tejun Heo <tj@kernel.org>
Cc: dsterba@suse.com, clm@fb.com, josef@toxicpanda.com,
	axboe@kernel.dk, jack@suse.cz, linux-btrfs@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
	kernel-team@fb.com
Subject: Re: [PATCH 2/9] blkcg, writeback: Add wbc->no_wbc_acct
Date: Mon, 24 Jun 2019 18:49:32 +0200	[thread overview]
Message-ID: <20190624164932.GN32376@quack2.suse.cz> (raw)
In-Reply-To: <20190615182453.843275-3-tj@kernel.org>

On Sat 15-06-19 11:24:46, Tejun Heo wrote:
> When writeback IOs are bounced through async layers, the IOs should
> only be accounted against the wbc from the original bdi writeback to
> avoid confusing cgroup inode ownership arbitration.  Add
> wbc->no_wbc_acct to allow disabling wbc accounting.  This will be used
> make btfs compression work well with cgroup IO control.
       ^^ btrfs

> Signed-off-by: Tejun Heo <tj@kernel.org>
> Reviewed-by: Josef Bacik <josef@toxicpanda.com>
...
> diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> index 738a0c24874f..b8f5f000cde4 100644
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -68,6 +68,7 @@ struct writeback_control {
>  	unsigned for_reclaim:1;		/* Invoked from the page allocator */
>  	unsigned range_cyclic:1;	/* range_start is cyclic */
>  	unsigned for_sync:1;		/* sync(2) WB_SYNC_ALL writeback */
> +	unsigned no_wbc_acct:1;		/* skip wbc IO accounting */
>  #ifdef CONFIG_CGROUP_WRITEBACK
>  	struct bdi_writeback *wb;	/* wb this writeback is issued under */
>  	struct inode *inode;		/* inode being written out */

Can you add comment here that this is for writeback which has been already
accounted for?

Otherwise the patch looks good to me so feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR