Re: [PATCH 1/2] blk-mq-sched: Allocate sched reserved tags as specified in the original queue tagset
From: Omar Sandoval <osandov@osandov.com>
Date: 2017-02-27 15:49:39
Also in:
linux-nvme
On Mon, Feb 27, 2017 at 05:36:20PM +0200, Sagi Grimberg wrote:
quoted hunk ↗ jump to hunk
Signed-off-by: Sagi Grimberg <sagi@grimberg.me> --- 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.