[PATCH 2/3] nvme/pci: Remove cq_vector check in IO path

Keith Busch
2017-12-21T20:46:35Z

This is a micro-optimization removing unnecessary check for a disabled
queue. We no longer need this check because blk-mq provides the ability
to quiesce queues that nvme uses, and the doorbell registers are never
unmapped as long as requests are active.

Signed-off-by: Keith Busch <keith.busch@intel.com>
---
drivers/nvme/host/pci.c | 11 ++---------
1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index df5550ce0531..0be5124a3a49 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -887,11 +887,6 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
}

spin_lock_irq(&nvmeq->q_lock);
- if (unlikely(nvmeq->cq_vector < 0)) {
- ret = BLK_STS_IOERR;
- spin_unlock_irq(&nvmeq->q_lock);
- goto out_cleanup_iod;
- }
__nvme_submit_cmd(nvmeq, &cmnd);
blk_mq_start_request(req);
nvme_process_cq(nvmeq);
@@ -923,11 +918,9 @@ static inline void nvme_ring_cq_doorbell(struct nvme_queue *nvmeq)
{
u16 head = nvmeq->cq_head;

- if (likely(nvmeq->cq_vector >= 0)) {
- if (nvme_dbbuf_update_and_check_event(head, nvmeq->dbbuf_cq_db,
+ if (nvme_dbbuf_update_and_check_event(head, nvmeq->dbbuf_cq_db,
nvmeq->dbbuf_cq_ei))
- writel(head, nvmeq->q_db + nvmeq->dev->db_stride);
- }
+ writel(head, nvmeq->q_db + nvmeq->dev->db_stride);
}

static inline void nvme_handle_cqe(struct nvme_queue *nvmeq,
--
2.13.6