linux-kernel - Re: [PATCH 3/6] page-writeback: pass in '0' for nr

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Message-ID: <20170920143505.GD11106@quack2.suse.cz>
Date:   Wed, 20 Sep 2017 16:35:05 +0200
From:   Jan Kara <jack@...e.cz>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, hannes@...xchg.org, clm@...com, jack@...e.cz
Subject: Re: [PATCH 3/6] page-writeback: pass in '0' for nr_pages writeback
 in laptop mode

On Tue 19-09-17 13:53:04, Jens Axboe wrote:
> Laptop mode really wants to writeback the number of dirty
> pages and inodes. Instead of calculating this in the caller,
> just pass in 0 and let wakeup_flusher_threads() handle it.
> 
> Use the new wakeup_flusher_threads_bdi() instead of rolling
> our own.
> 
> Signed-off-by: Jens Axboe <axboe@...nel.dk>
...
> -	rcu_read_lock();
> -	list_for_each_entry_rcu(wb, &q->backing_dev_info->wb_list, bdi_node)
> -		if (wb_has_dirty_io(wb))
> -			wb_start_writeback(wb, nr_pages, true,
> -					   WB_REASON_LAPTOP_TIMER);
> -	rcu_read_unlock();
> +	wakeup_flusher_threads_bdi(q->backing_dev_info, 0,
> +					WB_REASON_LAPTOP_TIMER);
>  }

So this slightly changes the semantics since previously we were doing
range_cyclic writeback and now we don't. I don't think this matters in
practice but please mention that in the changelog. With that you can add:

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

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