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

[Jan Kara <jack@suse.cz>]

On Mon 14-11-11 20:12:45, Wu Fengguang wrote:
> 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?
  Yes, it will. The only difference is that the task will be woken when
SIGKILL arrives.

> >  		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.
  OK, will do that.

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

									Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR