[PATCH 05/15] nvme: add Clang context annotations for nvme_ns_head::current_path

[Nilay Shroff <nilay@linux.ibm.com>]

Annotate nvme_ns_head::current_path[] with __rcu_guarded so that
Clang's context analysis can validate accesses to the SRCU/RCU
protected pointer.

The nvme_mpath_clear_current_path() helper only compares the
current_path[] pointer value using rcu_access_pointer() and does not
dereference the referenced namespace. Annotate this access with
context_unsafe() to suppress the corresponding context analysis
warning.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/host/multipath.c | 10 +++++++++-
 drivers/nvme/host/nvme.h      |  2 +-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 985a8c693c6f..ef072588eca0 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -231,8 +231,16 @@ bool nvme_mpath_clear_current_path(struct nvme_ns *ns)
 	bool changed = false;
 	int node;
 
+	/*
+	 * This helper is used by namespace failover/teardown and I/O policy
+	 * update paths. We only compare the head->current_path[] pointer value
+	 * and do not dereference the referenced namespace, so suppress the
+	 * context analysis warning for this lockless inspection of the
+	 * __rcu_guarded pointer.
+	 */
 	for_each_node(node) {
-		if (ns == rcu_access_pointer(head->current_path[node])) {
+		if (context_unsafe(ns ==
+				rcu_access_pointer(head->current_path[node]))) {
 			rcu_assign_pointer(head->current_path[node], NULL);
 			changed = true;
 		}
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index f60852944709..41f42f1aee09 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -565,7 +565,7 @@ struct nvme_ns_head {
 	unsigned int		delayed_removal_secs;
 #define NVME_NSHEAD_DISK_LIVE		0
 #define NVME_NSHEAD_QUEUE_IF_NO_PATH	1
-	struct nvme_ns __rcu	*current_path[];
+	struct nvme_ns __rcu_guarded	*current_path[];
 #endif
 };
 
-- 
2.53.0