Re: [PATCH 0/2] Make task doing heavy writing killable

[Jan Kara <jack@suse.cz>]

On Mon 14-11-11 07:05:46, Christoph Hellwig wrote:
> On Mon, Nov 14, 2011 at 07:59:12PM +0800, Wu Fengguang wrote:
> > On Mon, Nov 14, 2011 at 07:10:28PM +0800, Jan Kara wrote:
> > > 
> > >   Hello,
> > > 
> > >   these two patches aim at making task waiting in balance_dirty_pages()
> > > killable.  This is desirable because otherwise if filesystem stops accepting
> > > writes (e.g. if device has been removed or other serious error condidion) we
> > > have a task stuck in D state forever.
> > 
> > Agreed totally. I myself has run into such conditions and get very
> > annoyed not being able to kill the hard throttled tasks -- they just
> > stuck there for ever if the error condition does not change.
> > 
> > >   I'm not sure who should merge these two patches... Al, Fengguang?
> > 
> > I'd like to do it -- otherwise there will obviously be merge conflicts.
> > 
> > Actually I also queued a patch to do this (attached). Your patches do
> > better on TASK_KILLABLE and the use of signal_pending() in write
> > routines, while mine goes further to add the break to various
> > filesystems.  How about combining them together?
> 
> Can you make balance_dirty_pages(_ratelimited) return an error instead
> of opencoding the fatal signal check everywhere?  That would make the
> interface a bit more obvious.
  We can do this. It's just that signal_pending() check e.g. in
generic_perform_write() has a sense even when balance_dirty_pages() will be
returning error because it also catches other cases...

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