nvme-pci: remove last_sq_tail

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>

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index e95c746..b945e9a 100644 (file)
--- 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];