On Mon, Nov 20 2017 at 4:23pm -0500, Shaohua Li <shli@xxxxxxxxxx> wrote: > On Mon, Nov 20, 2017 at 04:02:03PM -0500, Mike Snitzer wrote: > > On Sun, Nov 19, 2017 at 9:00 PM, Joseph Qi <jiangqi903@xxxxxxxxx> wrote: > > > From: Joseph Qi <qijiang.qj@xxxxxxxxxxxxxxx> > > > > > > dm device set QUEUE_FLAG_NONROT in resume, which is after register > > > queue. That is to mean, the previous initialization in > > > blk_throtl_register_queue is wrong in this case. > > > Fix it by checking and then updating the info during root tg > > > initialization as we don't have a better choice. > > > > Given DM motivated this change, curious why you didn't send this to dm-devel? > > > > In any case, not sure why you need to reference "resume". Very few > > people will appreciate that detail. > > > > Better to just say: DM device sets QUEUE_FLAG_NONROT after the queue > > is registered. > > > > > Signed-off-by: Joseph Qi <qijiang.qj@xxxxxxxxxxxxxxx> > > > --- > > > block/blk-throttle.c | 17 +++++++++++++++++ > > > 1 file changed, 17 insertions(+) > > > > > > diff --git a/block/blk-throttle.c b/block/blk-throttle.c > > > index bf52035..6d6b220 100644 > > > --- a/block/blk-throttle.c > > > +++ b/block/blk-throttle.c > > > @@ -541,6 +541,23 @@ static void throtl_pd_init(struct blkg_policy_data *pd) > > > if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent) > > > sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue; > > > tg->td = td; > > > + > > > + /* > > > + * dm device set QUEUE_FLAG_NONROT in resume, which is after resister > > > + * queue, so the previous initialization is wrong in this case. Check > > > + * and update it here. > > > + */ > > > > typo: s/resister/register/ > > But again, best to say: > > DM device sets QUEUE_FLAG_NONROT after the queue is registered, ... > > > > Also, an alternative to your patch would be to have DM's > > dm_table_set_restrictions() call a blk-throttle function to setup > > blk-throttle after it is done setting queue flags? > > Saves all other drivers from having to run this 2 stage initialization > > code.. just a thought. > > Though the patch is a workaround, I'd prefer limiting the code into > blk-throttle itself. Populating it to drivers is a layer violation to me. The > initialization only runs once, so I think it's ok. I fail to see how this is a "workaround". Whatever you call it, the blk-throttle code needs to cope with the fact that DM's request_queue setup is different than other block devices. If having DM call a function that blk-throttle provides (code that is in block/blk-throttle.c) I fail to see the layer violation. No more a layer violation than any of the other block core code that block drivers call to setup the request_queue's capabilities. But I'm not well-versed on blk-throttle code (hence DM coming up lacking relative to it). SO I'll defer to you guys to sort it out how you think best. Thanks, Mike
