linux-kernel - Re: [PATCH 2/6] fs-writeback: provide a wakeup_flusher_threads

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Date:   Wed, 20 Sep 2017 16:19:57 +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 2/6] fs-writeback: provide a wakeup_flusher_threads_bdi()

On Tue 19-09-17 13:53:03, Jens Axboe wrote:
> Similar to wakeup_flusher_threads(), except that we only wake
> up the flusher threads on the specified backing device.
> 
> No functional changes in this patch.
> 
> Signed-off-by: Jens Axboe <axboe@...nel.dk>

Looks good. You can add:

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

								Honza

> ---
>  fs/fs-writeback.c         | 40 ++++++++++++++++++++++++++++++----------
>  include/linux/writeback.h |  2 ++
>  2 files changed, 32 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 245c430a2e41..03fda0830bf8 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -1947,6 +1947,34 @@ void wb_workfn(struct work_struct *work)
>  }
>  
>  /*
> + * Start writeback of `nr_pages' pages on this bdi. If `nr_pages' is zero,
> + * write back the whole world.
> + */
> +static void __wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
> +					 long nr_pages, enum wb_reason reason)
> +{
> +	struct bdi_writeback *wb;
> +
> +	if (!bdi_has_dirty_io(bdi))
> +		return;
> +
> +	list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
> +		wb_start_writeback(wb, wb_split_bdi_pages(wb, nr_pages),
> +					   false, reason);
> +}
> +
> +void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi, long nr_pages,
> +				enum wb_reason reason)
> +{
> +	if (!nr_pages)
> +		nr_pages = get_nr_dirty_pages();
> +
> +	rcu_read_lock();
> +	__wakeup_flusher_threads_bdi(bdi, nr_pages, reason);
> +	rcu_read_unlock();
> +}
> +
> +/*
>   * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
>   * the whole world.
>   */
> @@ -1964,16 +1992,8 @@ void wakeup_flusher_threads(long nr_pages, enum wb_reason reason)
>  		nr_pages = get_nr_dirty_pages();
>  
>  	rcu_read_lock();
> -	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list) {
> -		struct bdi_writeback *wb;
> -
> -		if (!bdi_has_dirty_io(bdi))
> -			continue;
> -
> -		list_for_each_entry_rcu(wb, &bdi->wb_list, bdi_node)
> -			wb_start_writeback(wb, wb_split_bdi_pages(wb, nr_pages),
> -					   false, reason);
> -	}
> +	list_for_each_entry_rcu(bdi, &bdi_list, bdi_list)
> +		__wakeup_flusher_threads_bdi(bdi, nr_pages, reason);
>  	rcu_read_unlock();
>  }
>  
> diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> index d5815794416c..5a7ed74d1f6f 100644
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -190,6 +190,8 @@ bool try_to_writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
>  				   enum wb_reason reason);
>  void sync_inodes_sb(struct super_block *);
>  void wakeup_flusher_threads(long nr_pages, enum wb_reason reason);
> +void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi, long nr_pages,
> +				enum wb_reason reason);
>  void inode_wait_for_writeback(struct inode *inode);
>  
>  /* writeback.h requires fs.h; it, too, is not included from here. */
> -- 
> 2.7.4
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR