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Subject[PATCH 4/5] NVMe: add blk polling support
Date
Add nvme_poll(), which will check a specific completion queue for
command completions. Wire that up to the new block layer poll
mechanism.

Later on we'll setup specific sq/cq pairs that don't have interrups
enabled, so we can do more efficient polling. As of this patch, an
IRQ will still trigger on command completion.

Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/nvme/host/pci.c | 32 ++++++++++++++++++++++++++++----
1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index e878590e71b6..4a715f49f5db 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -90,7 +90,7 @@ static struct class *nvme_class;

static int __nvme_reset(struct nvme_dev *dev);
static int nvme_reset(struct nvme_dev *dev);
-static int nvme_process_cq(struct nvme_queue *nvmeq);
+static void nvme_process_cq(struct nvme_queue *nvmeq);
static void nvme_dead_ctrl(struct nvme_dev *dev);

struct async_cmd_info {
@@ -935,7 +935,7 @@ static int nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
return BLK_MQ_RQ_QUEUE_BUSY;
}

-static int nvme_process_cq(struct nvme_queue *nvmeq)
+static void __nvme_process_cq(struct nvme_queue *nvmeq, unsigned int *tag)
{
u16 head, phase;

@@ -953,6 +953,8 @@ static int nvme_process_cq(struct nvme_queue *nvmeq)
head = 0;
phase = !phase;
}
+ if (tag && *tag == cqe.command_id)
+ *tag = -1;
ctx = nvme_finish_cmd(nvmeq, cqe.command_id, &fn);
fn(nvmeq, ctx, &cqe);
}
@@ -964,14 +966,18 @@ static int nvme_process_cq(struct nvme_queue *nvmeq)
* a big problem.
*/
if (head == nvmeq->cq_head && phase == nvmeq->cq_phase)
- return 0;
+ return;

writel(head, nvmeq->q_db + nvmeq->dev->db_stride);
nvmeq->cq_head = head;
nvmeq->cq_phase = phase;

nvmeq->cqe_seen = 1;
- return 1;
+}
+
+static void nvme_process_cq(struct nvme_queue *nvmeq)
+{
+ __nvme_process_cq(nvmeq, NULL);
}

static irqreturn_t nvme_irq(int irq, void *data)
@@ -995,6 +1001,23 @@ static irqreturn_t nvme_irq_check(int irq, void *data)
return IRQ_WAKE_THREAD;
}

+static int nvme_poll(struct blk_mq_hw_ctx *hctx, unsigned int tag)
+{
+ struct nvme_queue *nvmeq = hctx->driver_data;
+
+ if ((le16_to_cpu(nvmeq->cqes[nvmeq->cq_head].status) & 1) ==
+ nvmeq->cq_phase) {
+ spin_lock_irq(&nvmeq->q_lock);
+ __nvme_process_cq(nvmeq, &tag);
+ spin_unlock_irq(&nvmeq->q_lock);
+
+ if (tag == -1)
+ return 1;
+ }
+
+ return 0;
+}
+
/*
* Returns 0 on success. If the result is negative, it's a Linux error code;
* if the result is positive, it's an NVM Express status code
@@ -1654,6 +1677,7 @@ static struct blk_mq_ops nvme_mq_ops = {
.init_hctx = nvme_init_hctx,
.init_request = nvme_init_request,
.timeout = nvme_timeout,
+ .poll = nvme_poll,
};

static void nvme_dev_remove_admin(struct nvme_dev *dev)
--
2.4.1.168.g1ea28e1


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