On Mon, Oct 07, 2019 at 08:27:38AM +0200, Hannes Reinecke wrote: > On 10/6/19 4:45 AM, Ming Lei wrote: > > When all CPUs in one hctx are offline, we shouldn't run this hw queue > > for completing request any more. > > > > So steal bios from the request, and resubmit them, and finally free > > the request in blk_mq_hctx_notify_dead(). > > > > Cc: Bart Van Assche <[email protected]> > > Cc: Hannes Reinecke <[email protected]> > > Cc: Christoph Hellwig <[email protected]> > > Cc: Thomas Gleixner <[email protected]> > > Cc: Keith Busch <[email protected]> > > Signed-off-by: Ming Lei <[email protected]> > > --- > > block/blk-mq.c | 48 +++++++++++++++++++++++++++++++++++++++++------- > > 1 file changed, 41 insertions(+), 7 deletions(-) > > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > > index d991c122abf2..0b35fdbd1f17 100644 > > --- a/block/blk-mq.c > > +++ b/block/blk-mq.c > > @@ -2280,10 +2280,30 @@ static int blk_mq_hctx_notify_online(unsigned int > > cpu, struct hlist_node *node) > > return 0; > > } > > > > +static void blk_mq_resubmit_io(struct request *rq) > > +{ > > + struct bio_list list; > > + struct bio *bio; > > + > > + bio_list_init(&list); > > + blk_steal_bios(&list, rq); > > + > > + while (true) { > > + bio = bio_list_pop(&list); > > + if (!bio) > > + break; > > + > > + generic_make_request(bio); > > + } > > + > > + blk_mq_cleanup_rq(rq); > > + blk_mq_end_request(rq, 0); > > +} > > + > Hmm. Not sure if this is a good idea. > Shouldn't we call 'blk_mq_end_request()' before calling > generic_make_request()? > otherwise the cloned request might be completed before original one, > which looks a bit dodgy to me; and might lead to quite a recursion if we > have several dead cpus to content with ...
Good catch, we should have freed the old empty request before calling generic_make_request(), will fix it in V3. Thanks, Ming
