Re: [RFC][PATCH 2/7] writeback: fix queue_io() ordering

[Jan Kara <jack@suse.cz>]

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@fromorbit.com>
> Cc: Martin Bligh <mbligh@google.com>
> Cc: Michael Rubin <mrubin@google.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Fengguang Wu <wfg@mail.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@suse.cz>
SUSE Labs, CR