nvmet: support completion queue sharing

The NVMe PCI transport specification allows for completion queues to be
shared by different submission queues.

This patch allows a submission queue to keep track of the completion queue
it is using with reference counting. As such, it can be ensured that a
completion queue is not deleted while a submission queue is actively
using it.

This patch enables completion queue sharing in the pci-epf target driver.
For fabrics drivers, completion queue sharing is not enabled as it is
not possible as per the fabrics specification. However, this patch
modifies the fabrics drivers to correctly integrate the new API that
supports completion queue sharing.

Signed-off-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 10 insertions, 9 deletions

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 5e3699973d56..c7317299078d 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -63,14 +63,9 @@ static void nvmet_execute_create_sq(struct nvmet_req *req)
 	if (status != NVME_SC_SUCCESS)
 		goto complete;
 
-	/*
-	 * Note: The NVMe specification allows multiple SQs to use the same CQ.
-	 * However, the target code does not really support that. So for now,
-	 * prevent this and fail the command if sqid and cqid are different.
-	 */
-	if (!cqid || cqid != sqid) {
-		pr_err("SQ %u: Unsupported CQID %u\n", sqid, cqid);
-		status = NVME_SC_CQ_INVALID | NVME_STATUS_DNR;
+	status = nvmet_check_io_cqid(ctrl, cqid, false);
+	if (status != NVME_SC_SUCCESS) {
+		pr_err("SQ %u: Invalid CQID %u\n", sqid, cqid);
 		goto complete;
 	}
 
@@ -79,7 +74,7 @@ static void nvmet_execute_create_sq(struct nvmet_req *req)
 		goto complete;
 	}
 
-	status = ctrl->ops->create_sq(ctrl, sqid, sq_flags, qsize, prp1);
+	status = ctrl->ops->create_sq(ctrl, sqid, cqid, sq_flags, qsize, prp1);
 
 complete:
 	nvmet_req_complete(req, status);
@@ -100,6 +95,12 @@ static void nvmet_execute_delete_cq(struct nvmet_req *req)
 	if (status != NVME_SC_SUCCESS)
 		goto complete;
 
+	if (!ctrl->cqs[cqid] || nvmet_cq_in_use(ctrl->cqs[cqid])) {
+		/* Some SQs are still using this CQ */
+		status = NVME_SC_QID_INVALID | NVME_STATUS_DNR;
+		goto complete;
+	}
+
 	status = ctrl->ops->delete_cq(ctrl, cqid);
 
 complete: