Re: [PATCH 1/2] mm: Make task in balance_dirty_pages() killable

[Wu Fengguang <fengguang.wu@intel.com>]

On Mon, Nov 14, 2011 at 07:10:29PM +0800, Jan Kara wrote:
> There is no reason why task in balance_dirty_pages() shouldn't be killable
> and it helps in recovering from some error conditions (like when filesystem
> goes in error state and cannot accept writeback anymore but we still want to
> kill processes using it to be able to unmount it).
> 
> Reported-by: Kazuya Mio <k-mio@sx.jp.nec.com>
> Tested-by: Kazuya Mio <k-mio@sx.jp.nec.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  mm/page-writeback.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 0360d1b..e83c286 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1133,8 +1133,10 @@ pause:
>  					  pages_dirtied,
>  					  pause,
>  					  start_time);
> -		__set_current_state(TASK_UNINTERRUPTIBLE);
> +		__set_current_state(TASK_KILLABLE);

Dumb question: will the task continue to show up as 'D' in ps?

>  		io_schedule_timeout(pause);
> +		if (fatal_signal_pending(current))
> +			break;

I'd like to move that several lines below, to the end of the loop, 
so that the condition is not tested at all in normal executions.

>  		dirty_thresh = hard_dirty_limit(dirty_thresh);
>  		/*
> -- 
> 1.7.1