linux-kernel - Re: [RFC][PATCH 2/7] writeback: fix queue

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Date:	Wed, 9 Sep 2009 17:53:30 +0200
From:	Jan Kara <jack@...e.cz>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Christoph Hellwig <hch@...radead.org>, jack@...e.cz,
	Artem Bityutskiy <dedekind1@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [RFC][PATCH 2/7] writeback: fix queue_io() ordering

On Wed 09-09-09 22:51:43, Wu Fengguang wrote:
> This was not a bug, since b_io is empty for kupdate writeback.
> The next patch will do requeue_io() for non-kupdate writeback,
> so let's fix it.
  But doesn't this patch also need your "anti-starvation" patch?
Looking into the code, we put inode to b_more_io when nr_to_write
drops to zero and this way we'd just start writing it again
in the next round...

							Honza
> 
> CC: Dave Chinner <david@...morbit.com>
> Cc: Martin Bligh <mbligh@...gle.com>
> Cc: Michael Rubin <mrubin@...gle.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Fengguang Wu <wfg@...l.ustc.edu.cn>
> ---
>  fs/fs-writeback.c |    7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> --- linux.orig/fs/fs-writeback.c	2009-09-09 21:41:14.000000000 +0800
> +++ linux/fs/fs-writeback.c	2009-09-09 21:45:15.000000000 +0800
> @@ -313,11 +313,14 @@ static void move_expired_inodes(struct l
>  }
>  
>  /*
> - * Queue all expired dirty inodes for io, eldest first.
> + * Queue all expired dirty inodes for io, eldest first:
> + * (newly dirtied) => b_dirty inodes
> + *                 => b_more_io inodes
> + *                 => remaining inodes in b_io => (dequeue for sync)
>   */
>  static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
>  {
> -	list_splice_init(&wb->b_more_io, wb->b_io.prev);
> +	list_splice_init(&wb->b_more_io, &wb->b_io);
>  	move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
>  }
>  
> 
> -- 
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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