nvmet: add safety check for subsys lock

Replace comment about required lock with a lockdep_assert_held()
check in the following functions:
 - nvmet_p2pmem_ns_add_p2p()
 - nvmet_setup_p2p_ns_map()
 - nvmet_release_p2p_ns_map()

This ensures the subsystem lock is held at runtime.

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

Author: mgurtovoy

drivers/nvme/target/core.c

@@ -513,16 +513,15 @@ static int nvmet_p2pmem_ns_enable(struct nvmet_ns *ns)
 	return 0;
 }
 
-/*
- * Note: ctrl->subsys->lock should be held when calling this function
- */
 static void nvmet_p2pmem_ns_add_p2p(struct nvmet_ctrl *ctrl,
 				    struct nvmet_ns *ns)
 {
 	struct device *clients[2];
 	struct pci_dev *p2p_dev;
 	int ret;
 
+	lockdep_assert_held(&ctrl->subsys->lock);
+
 	if (!ctrl->p2p_client || !ns->use_p2pmem)
 		return;
 
@@ -1539,15 +1538,14 @@ bool nvmet_host_allowed(struct nvmet_subsys *subsys, const char *hostnqn)
 	return false;
 }
 
-/*
- * Note: ctrl->subsys->lock should be held when calling this function
- */
 static void nvmet_setup_p2p_ns_map(struct nvmet_ctrl *ctrl,
 		struct device *p2p_client)
 {
 	struct nvmet_ns *ns;
 	unsigned long idx;
 
+	lockdep_assert_held(&ctrl->subsys->lock);
+
 	if (!p2p_client)
 		return;
 
@@ -1557,14 +1555,13 @@ static void nvmet_setup_p2p_ns_map(struct nvmet_ctrl *ctrl,
 		nvmet_p2pmem_ns_add_p2p(ctrl, ns);
 }
 
-/*
- * Note: ctrl->subsys->lock should be held when calling this function
- */
 static void nvmet_release_p2p_ns_map(struct nvmet_ctrl *ctrl)
 {
 	struct radix_tree_iter iter;
 	void __rcu **slot;
 
+	lockdep_assert_held(&ctrl->subsys->lock);
+
 	radix_tree_for_each_slot(slot, &ctrl->p2p_ns_map, &iter, 0)
 		pci_dev_put(radix_tree_deref_slot(slot));