On Mon, Feb 27, 2017 at 05:36:20PM +0200, Sagi Grimberg wrote: > Signed-off-by: Sagi Grimberg <[email protected]> > --- > block/blk-mq-sched.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c > index 98c7b061781e..46ca965fff5c 100644 > --- a/block/blk-mq-sched.c > +++ b/block/blk-mq-sched.c > @@ -454,7 +454,8 @@ int blk_mq_sched_setup(struct request_queue *q) > */ > ret = 0; > queue_for_each_hw_ctx(q, hctx, i) { > - hctx->sched_tags = blk_mq_alloc_rq_map(set, i, q->nr_requests, > 0); > + hctx->sched_tags = blk_mq_alloc_rq_map(set, i, > + q->nr_requests, set->reserved_tags); > if (!hctx->sched_tags) { > ret = -ENOMEM; > break; > -- > 2.7.4
Hm, this may fix the crash, but I'm not sure it'll work as intended. When we allocate the request, we'll get a reserved scheduler tag, but then when we go to dispatch the request and call blk_mq_get_driver_tag(), we'll be competing with all of the normal requests for a regular driver tag. So maybe on top of this we should add the BLK_MQ_REQ_RESERVED flag to the allocation attempt in blk_mq_get_driver_tag() if the scheduler tag is reserved? I'm hazy on what we expect from reserved tags, so feel free to call me crazy.
