From: Keith Busch <kbusch@kernel.org>

Date: Mon, 27 Apr 2020 11:54:46 -0700

Subject: [PATCH] nvme-pci: remove last_sq_tail

Git-commit: 54b2fcee1db041a83b52b51752dade6090cf952f

Patch-mainline: v5.8-rc1

References: git-fixes

The nvme driver does not have enough tags to wrap the queue, and blk-mq

will no longer call commit_rqs() when there are no new submissions to

notify.

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 | 23 ++++-------------------

 1 file changed, 4 insertions(+), 19 deletions(-)

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

index e95c7465c7bd..b945e9a89883 100644

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

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

@@ -173,7 +173,6 @@ struct nvme_queue {

 	u16 q_depth;

 	u16 cq_vector;

 	u16 sq_tail;

-	u16 last_sq_tail;

 	u16 cq_head;

 	u16 qid;

 	u8 cq_phase;

@@ -446,24 +445,11 @@ static int nvme_pci_map_queues(struct blk_mq_tag_set *set)

 	return 0;

 }

-/*

- * Write sq tail if we are asked to, or if the next command would wrap.

- */

-static inline void nvme_write_sq_db(struct nvme_queue *nvmeq, bool write_sq)

+static inline void nvme_write_sq_db(struct nvme_queue *nvmeq)

 {

-	if (!write_sq) {

-		u16 next_tail = nvmeq->sq_tail + 1;

-

-		if (next_tail == nvmeq->q_depth)

-			next_tail = 0;

-		if (next_tail != nvmeq->last_sq_tail)

-			return;

-	}

-

 	if (nvme_dbbuf_update_and_check_event(nvmeq->sq_tail,

 			nvmeq->dbbuf_sq_db, nvmeq->dbbuf_sq_ei))

 		writel(nvmeq->sq_tail, nvmeq->q_db);

-	nvmeq->last_sq_tail = nvmeq->sq_tail;

 }

 /**

@@ -480,7 +466,8 @@ static void nvme_submit_cmd(struct nvme_queue *nvmeq, struct nvme_command *cmd,

 	       cmd, sizeof(*cmd));

 	if (++nvmeq->sq_tail == nvmeq->q_depth)

 		nvmeq->sq_tail = 0;

-	nvme_write_sq_db(nvmeq, write_sq);

+	if (write_sq)

+		nvme_write_sq_db(nvmeq);

 	spin_unlock(&nvmeq->sq_lock);

 }

@@ -489,8 +476,7 @@ static void nvme_commit_rqs(struct blk_mq_hw_ctx *hctx)

 	struct nvme_queue *nvmeq = hctx->driver_data;

 	spin_lock(&nvmeq->sq_lock);

-	if (nvmeq->sq_tail != nvmeq->last_sq_tail)

-		nvme_write_sq_db(nvmeq, true);

+	nvme_write_sq_db(nvmeq);

 	spin_unlock(&nvmeq->sq_lock);

 }

@@ -1494,7 +1480,6 @@ static void nvme_init_queue(struct nvme_queue *nvmeq, u16 qid)

 	struct nvme_dev *dev = nvmeq->dev;

 	nvmeq->sq_tail = 0;

-	nvmeq->last_sq_tail = 0;

 	nvmeq->cq_head = 0;

 	nvmeq->cq_phase = 1;

 	nvmeq->q_db = &dev->dbs[qid * 2 * dev->db_stride];

-- 

2.29.2