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

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

On Wed, Nov 16, 2011 at 07:12:14PM +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).

Here I'd like to add a paragraph from my original patch:

The follow up patches will further abort the generic_perform_write() and
other filesystem write loops, to avoid large write + SIGKILL combination
exceeding the dirty limit and possibly strange OOM.

Thanks,
Fengguang

> 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 |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 0360d1b..39f5805 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1133,7 +1133,7 @@ pause:
>  					  pages_dirtied,
>  					  pause,
>  					  start_time);
> -		__set_current_state(TASK_UNINTERRUPTIBLE);
> +		__set_current_state(TASK_KILLABLE);
>  		io_schedule_timeout(pause);
>  
>  		dirty_thresh = hard_dirty_limit(dirty_thresh);
> @@ -1145,6 +1145,9 @@ pause:
>  		 */
>  		if (nr_dirty < dirty_thresh)
>  			break;
> +
> +		if (fatal_signal_pending(current))
> +			break;
>  	}
>  
>  	if (!dirty_exceeded && bdi->dirty_exceeded)
> -- 
> 1.7.1