linux-kernel - Re: [PATCH 5/6] fs-writeback: move nr

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Message-ID: <20170920153627.GI11106@quack2.suse.cz>
Date:   Wed, 20 Sep 2017 17:36:27 +0200
From:   Jan Kara <jack@...e.cz>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        hannes@...xchg.org, clm@...com
Subject: Re: [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one
 location

On Wed 20-09-17 09:05:51, Jens Axboe wrote:
> On 09/20/2017 08:41 AM, Jan Kara wrote:
> > On Tue 19-09-17 13:53:06, Jens Axboe wrote:
> >> Now that we have no external callers of wb_start_writeback(),
> >> we can move the nr_pages == 0 logic into that function.
> >>
> >> Signed-off-by: Jens Axboe <axboe@...nel.dk>
> > 
> > ...
> > 
> >> +static unsigned long get_nr_dirty_pages(void)
> >> +{
> >> +	return global_node_page_state(NR_FILE_DIRTY) +
> >> +		global_node_page_state(NR_UNSTABLE_NFS) +
> >> +		get_nr_dirty_inodes();
> >> +}
> >> +
> >>  static void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
> >>  			       bool range_cyclic, enum wb_reason reason)
> >>  {
> >> @@ -942,6 +953,12 @@ static void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
> >>  		return;
> >>  
> >>  	/*
> >> +	 * If someone asked for zero pages, we write out the WORLD
> >> +	 */
> >> +	if (!nr_pages)
> >> +		nr_pages = get_nr_dirty_pages();
> >> +
> > 
> > So for 'wb' we have a better estimate of the amount we should write - use
> > wb_stat_sum(wb, WB_RECLAIMABLE) statistics - that is essentially dirty +
> > unstable_nfs broken down to bdi_writeback.
> 
> I don't mind making that change, but I think that should be a separate
> patch. We're using get_nr_dirty_pages() in existing locations where
> we have the 'wb', like in wb_check_old_data_flush().

Good point and fully agreed. So you can add:

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

for this patch.

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