Re: [PATCH 1/5] mm: hide laptop_mode_wb_timer entirely behind the BDI API

From: Jan Kara <jack@suse.cz>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
	Jan Kara <jack@suse.cz>,
	linux-block@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 1/5] mm: hide laptop_mode_wb_timer entirely behind the BDI API
Date: Mon, 9 Aug 2021 17:10:48 +0200	[thread overview]
Message-ID: <20210809151048.GE30319@quack2.suse.cz> (raw)
In-Reply-To: <20210809141744.1203023-2-hch@lst.de>

On Mon 09-08-21 16:17:40, Christoph Hellwig wrote:
> Don't leak the detaіls of the timer into the block layer, instead
> initialize the timer in bdi_alloc and delete it in bdi_unregister.
> Note that this means the timer is initialized (but not armed) for
> non-block queues as well now.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good. Feel free to add:

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

								Honza

> ---
>  block/blk-core.c    | 5 -----
>  mm/backing-dev.c    | 3 +++
>  mm/page-writeback.c | 2 --
>  3 files changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 04477697ee4b..5897bc37467d 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -394,10 +394,7 @@ void blk_cleanup_queue(struct request_queue *q)
>  	/* for synchronous bio-based driver finish in-flight integrity i/o */
>  	blk_flush_integrity();
>  
> -	/* @q won't process any more request, flush async actions */
> -	del_timer_sync(&q->backing_dev_info->laptop_mode_wb_timer);
>  	blk_sync_queue(q);
> -
>  	if (queue_is_mq(q))
>  		blk_mq_exit_queue(q);
>  
> @@ -546,8 +543,6 @@ struct request_queue *blk_alloc_queue(int node_id)
>  
>  	atomic_set(&q->nr_active_requests_shared_sbitmap, 0);
>  
> -	timer_setup(&q->backing_dev_info->laptop_mode_wb_timer,
> -		    laptop_mode_timer_fn, 0);
>  	timer_setup(&q->timeout, blk_rq_timed_out_timer, 0);
>  	INIT_WORK(&q->timeout_work, blk_timeout_work);
>  	INIT_LIST_HEAD(&q->icq_list);
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index f5561ea7d90a..cd06dca232c3 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -807,6 +807,7 @@ struct backing_dev_info *bdi_alloc(int node_id)
>  	bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
>  	bdi->ra_pages = VM_READAHEAD_PAGES;
>  	bdi->io_pages = VM_READAHEAD_PAGES;
> +	timer_setup(&bdi->laptop_mode_wb_timer, laptop_mode_timer_fn, 0);
>  	return bdi;
>  }
>  EXPORT_SYMBOL(bdi_alloc);
> @@ -928,6 +929,8 @@ static void bdi_remove_from_list(struct backing_dev_info *bdi)
>  
>  void bdi_unregister(struct backing_dev_info *bdi)
>  {
> +	del_timer_sync(&bdi->laptop_mode_wb_timer);
> +
>  	/* make sure nobody finds us on the bdi_list anymore */
>  	bdi_remove_from_list(bdi);
>  	wb_shutdown(&bdi->wb);
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 9f63548f247c..c12f67cbfa19 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -2010,7 +2010,6 @@ int dirty_writeback_centisecs_handler(struct ctl_table *table, int write,
>  	return ret;
>  }
>  
> -#ifdef CONFIG_BLOCK
>  void laptop_mode_timer_fn(struct timer_list *t)
>  {
>  	struct backing_dev_info *backing_dev_info =
> @@ -2045,7 +2044,6 @@ void laptop_sync_completion(void)
>  
>  	rcu_read_unlock();
>  }
> -#endif
>  
>  /*
>   * If ratelimit_pages is too high then we can get into dirty-data overload
> -- 
> 2.30.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR