From: Keith Busch <kbusch@kernel.org>

Date: Tue, 28 Apr 2020 07:21:56 -0700

Subject: [PATCH] nvme-pci: remove volatile cqes

Git-commit: 74943d45eef4db64b1e5c9f7ad1d018576e113c5

Patch-mainline: v5.8-rc1

References: git-fixes

The completion queue entry is not volatile once the phase is confirmed.

Remove the volatile keywords and check the phase using the appropriate

READ_ONCE() accessor, allowing the compiler to optimize the remaining

completion path.

Signed-off-by: Keith Busch <kbusch@kernel.org>

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

Signed-off-by: Christoph Hellwig <hch@lst.de>

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Acked-by: Hannes Reinecke <hare@suse.com>

---

 drivers/nvme/host/pci.c | 9 +++++----

 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c

index e13c370de830..e95c7465c7bd 100644

--- a/drivers/nvme/host/pci.c

+++ b/drivers/nvme/host/pci.c

@@ -166,7 +166,7 @@ struct nvme_queue {

 	void *sq_cmds;

 	 /* only used for poll queues: */

 	spinlock_t cq_poll_lock ____cacheline_aligned_in_smp;

-	volatile struct nvme_completion *cqes;

+	struct nvme_completion *cqes;

 	dma_addr_t sq_dma_addr;

 	dma_addr_t cq_dma_addr;

 	u32 __iomem *q_db;

@@ -922,8 +922,9 @@ static void nvme_pci_complete_rq(struct request *req)

 /* We read the CQE phase first to check if the rest of the entry is valid */

 static inline bool nvme_cqe_pending(struct nvme_queue *nvmeq)

 {

-	return (le16_to_cpu(nvmeq->cqes[nvmeq->cq_head].status) & 1) ==

-			nvmeq->cq_phase;

+	struct nvme_completion *hcqe = &nvmeq->cqes[nvmeq->cq_head];

+

+	return (le16_to_cpu(READ_ONCE(hcqe->status)) & 1) == nvmeq->cq_phase;

 }

 static inline void nvme_ring_cq_doorbell(struct nvme_queue *nvmeq)

@@ -944,7 +945,7 @@ static inline struct blk_mq_tags *nvme_queue_tagset(struct nvme_queue *nvmeq)

 static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)

 {

-	volatile struct nvme_completion *cqe = &nvmeq->cqes[idx];

+	struct nvme_completion *cqe = &nvmeq->cqes[idx];

 	struct request *req;

 	if (unlikely(cqe->command_id >= nvmeq->q_depth)) {

-- 

2.29.2