nvme-rdma: remove redundant reference between ib_device and tagset

In the past, before adding f41725bb ("nvme-rdma: Use mr pool") commit,
we needed a reference on the ib_device as long as the tagset
was alive, as the MRs in the request structures needed a valid ib_device.
Now, we allocate/deallocate MR pool per QP and consume on demand.

Also remove nvme_rdma_free_tagset function and use blk_mq_free_tag_set
instead, as it unneeded anymore.

This commit also fixes a memory leakage and possible segmentation fault.
When configuring the system with NIC teaming (aka bonding), we use 1
network interface to create an HA connection to the target side. In case
one connection breaks down, nvme-rdma driver will get notification from
rdma-cm layer that underlying address was change and will start error
recovery process. During this process, we'll reconnect to the target
via the second interface in the bond without destroying the tagset.
This will cause a leakage of the initial rdma device (ndev) and miscount
in the reference count of the new created rdma device (new ndev). In
the final destruction (or in another error flow), we'll get a warning
dump from the ib_dealloc_pd that we still have inflight MR's related to
that pd. This happens becasue of the miscount of the reference tag of
the rdma device and causing access violation to it's elements (some
queues are not destroyed yet).

Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/rdma.c

@@ -697,15 +697,6 @@ out_free_queues:
 	return ret;
 }
 
-static void nvme_rdma_free_tagset(struct nvme_ctrl *nctrl,
-		struct blk_mq_tag_set *set)
-{
-	struct nvme_rdma_ctrl *ctrl = to_rdma_ctrl(nctrl);
-
-	blk_mq_free_tag_set(set);
-	nvme_rdma_dev_put(ctrl->device);
-}
-
 static struct blk_mq_tag_set *nvme_rdma_alloc_tagset(struct nvme_ctrl *nctrl,
 		bool admin)
 {
@@ -744,24 +735,9 @@ static struct blk_mq_tag_set *nvme_rdma_alloc_tagset(struct nvme_ctrl *nctrl,
 
 	ret = blk_mq_alloc_tag_set(set);
 	if (ret)
-		goto out;
-
-	/*
-	 * We need a reference on the device as long as the tag_set is alive,
-	 * as the MRs in the request structures need a valid ib_device.
-	 */
-	ret = nvme_rdma_dev_get(ctrl->device);
-	if (!ret) {
-		ret = -EINVAL;
-		goto out_free_tagset;
-	}
+		return ERR_PTR(ret);
 
 	return set;
-
-out_free_tagset:
-	blk_mq_free_tag_set(set);
-out:
-	return ERR_PTR(ret);
 }
 
 static void nvme_rdma_destroy_admin_queue(struct nvme_rdma_ctrl *ctrl,
@@ -769,7 +745,7 @@ static void nvme_rdma_destroy_admin_queue(struct nvme_rdma_ctrl *ctrl,
 {
 	if (remove) {
 		blk_cleanup_queue(ctrl->ctrl.admin_q);
-		nvme_rdma_free_tagset(&ctrl->ctrl, ctrl->ctrl.admin_tagset);
+		blk_mq_free_tag_set(ctrl->ctrl.admin_tagset);
 	}
 	if (ctrl->async_event_sqe.data) {
 		nvme_rdma_free_qe(ctrl->device->dev, &ctrl->async_event_sqe,
@@ -847,7 +823,7 @@ out_cleanup_queue:
 		blk_cleanup_queue(ctrl->ctrl.admin_q);
 out_free_tagset:
 	if (new)
-		nvme_rdma_free_tagset(&ctrl->ctrl, ctrl->ctrl.admin_tagset);
+		blk_mq_free_tag_set(ctrl->ctrl.admin_tagset);
 out_free_async_qe:
 	nvme_rdma_free_qe(ctrl->device->dev, &ctrl->async_event_sqe,
 		sizeof(struct nvme_command), DMA_TO_DEVICE);
@@ -862,7 +838,7 @@ static void nvme_rdma_destroy_io_queues(struct nvme_rdma_ctrl *ctrl,
 {
 	if (remove) {
 		blk_cleanup_queue(ctrl->ctrl.connect_q);
-		nvme_rdma_free_tagset(&ctrl->ctrl, ctrl->ctrl.tagset);
+		blk_mq_free_tag_set(ctrl->ctrl.tagset);
 	}
 	nvme_rdma_free_io_queues(ctrl);
 }
@@ -903,7 +879,7 @@ out_cleanup_connect_q:
 		blk_cleanup_queue(ctrl->ctrl.connect_q);
 out_free_tag_set:
 	if (new)
-		nvme_rdma_free_tagset(&ctrl->ctrl, ctrl->ctrl.tagset);
+		blk_mq_free_tag_set(ctrl->ctrl.tagset);
 out_free_io_queues:
 	nvme_rdma_free_io_queues(ctrl);
 	return ret;