Re: [PATCH 2/5] sched: always use blk_schedule_flush_plug in io_schedule_out

[Shaohua Li]

On Fri, May 01, 2015 at 02:07:42PM -0400, Jeff Moyer wrote:
> Jeff Moyer <jmoyer@xxxxxxxxxx> writes:
> 
> > Shaohua Li <shli@xxxxxx> writes:
> >
> >> block plug callback could sleep, so we introduce a parameter
> >> 'from_schedule' and corresponding drivers can use it to destinguish a
> >> schedule plug flush or a plug finish. Unfortunately io_schedule_out
> >> still uses blk_flush_plug(). This causes below output (Note, I added a
> >> might_sleep() in raid1_unplug to make it trigger faster, but the whole
> >> thing doesn't matter if I add might_sleep). In raid1/10, this can cause
> >> deadlock.
> >>
> >> This patch makes io_schedule_out always uses blk_schedule_flush_plug.
> >> This should only impact drivers (as far as I know, raid 1/10) which are
> >> sensitive to the 'from_schedule' parameter.
> >
> > Why wouldn't you change io_schedule_timeout to use blk_flush_plug_list
> > instead?
> 
> Sorry, I did not fully engage my brain on this one.  I see that's
> exactly what you did.
> 
> I'll add my reviewed-by once you've addressed hch's concern.

Thanks! Updated patch.