1 files changed, 34 insertions, 4 deletions

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index df8f3612107f..3be352403839 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -198,6 +198,7 @@ struct nvme_queue {
 	u32 q_depth;
 	u16 cq_vector;
 	u16 sq_tail;
+	u16 last_sq_tail;
 	u16 cq_head;
 	u16 qid;
 	u8 cq_phase;
@@ -291,9 +292,21 @@ static void nvme_dbbuf_init(struct nvme_dev *dev,
 	nvmeq->dbbuf_cq_ei = &dev->dbbuf_eis[cq_idx(qid, dev->db_stride)];
 }
 
+static void nvme_dbbuf_free(struct nvme_queue *nvmeq)
+{
+	if (!nvmeq->qid)
+		return;
+
+	nvmeq->dbbuf_sq_db = NULL;
+	nvmeq->dbbuf_cq_db = NULL;
+	nvmeq->dbbuf_sq_ei = NULL;
+	nvmeq->dbbuf_cq_ei = NULL;
+}
+
 static void nvme_dbbuf_set(struct nvme_dev *dev)
 {
 	struct nvme_command c;
+	unsigned int i;
 
 	if (!dev->dbbuf_dbs)
 		return;
@@ -307,6 +320,9 @@ static void nvme_dbbuf_set(struct nvme_dev *dev)
 		dev_warn(dev->ctrl.device, "unable to set dbbuf\n");
 		/* Free memory and continue on */
 		nvme_dbbuf_dma_free(dev);
+
+		for (i = 1; i <= dev->online_queues; i++)
+			nvme_dbbuf_free(&dev->queues[i]);
 	}
 }
 
@@ -455,11 +471,24 @@ static int nvme_pci_map_queues(struct blk_mq_tag_set *set)
 	return 0;
 }
 
-static inline void nvme_write_sq_db(struct nvme_queue *nvmeq)
+/*
+ * 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)
 {
+	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;
 }
 
 /**
@@ -476,8 +505,7 @@ 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;
-	if (write_sq)
-		nvme_write_sq_db(nvmeq);
+	nvme_write_sq_db(nvmeq, write_sq);
 	spin_unlock(&nvmeq->sq_lock);
 }
 
@@ -486,7 +514,8 @@ static void nvme_commit_rqs(struct blk_mq_hw_ctx *hctx)
 	struct nvme_queue *nvmeq = hctx->driver_data;
 
 	spin_lock(&nvmeq->sq_lock);
-	nvme_write_sq_db(nvmeq);
+	if (nvmeq->sq_tail != nvmeq->last_sq_tail)
+		nvme_write_sq_db(nvmeq, true);
 	spin_unlock(&nvmeq->sq_lock);
 }
 
@@ -1496,6 +1525,7 @@ 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];