nvme/multipath: Fix RCU list traversal to use SRCU primitive

The code currently uses list_for_each_entry_rcu() while holding an SRCU
lock, triggering false positive warnings with CONFIG_PROVE_RCU=y
enabled:

	drivers/nvme/host/multipath.c:168 RCU-list traversed in non-reader section!!
	drivers/nvme/host/multipath.c:227 RCU-list traversed in non-reader section!!
	drivers/nvme/host/multipath.c:260 RCU-list traversed in non-reader section!!

While the list is properly protected by SRCU lock, the code uses the
wrong list traversal primitive. Replace list_for_each_entry_rcu() with
list_for_each_entry_srcu() to correctly indicate SRCU-based protection
and eliminate the false warning.

Signed-off-by: Breno Leitao <leitao@debian.org>
Fixes: be647e2 ("nvme: use srcu for iterating namespace list")
Signed-off-by: Keith Busch <kbusch@kernel.org>

Author: leitao

drivers/nvme/host/multipath.c

@@ -165,7 +165,8 @@ void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl)
 	int srcu_idx;
 
 	srcu_idx = srcu_read_lock(&ctrl->srcu);
-	list_for_each_entry_rcu(ns, &ctrl->namespaces, list) {
+	list_for_each_entry_srcu(ns, &ctrl->namespaces, list,
+				 srcu_read_lock_held(&ctrl->srcu)) {
 		if (!ns->head->disk)
 			continue;
 		kblockd_schedule_work(&ns->head->requeue_work);
@@ -209,7 +210,8 @@ void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl)
 	int srcu_idx;
 
 	srcu_idx = srcu_read_lock(&ctrl->srcu);
-	list_for_each_entry_rcu(ns, &ctrl->namespaces, list) {
+	list_for_each_entry_srcu(ns, &ctrl->namespaces, list,
+				 srcu_read_lock_held(&ctrl->srcu)) {
 		nvme_mpath_clear_current_path(ns);
 		kblockd_schedule_work(&ns->head->requeue_work);
 	}
@@ -224,7 +226,8 @@ void nvme_mpath_revalidate_paths(struct nvme_ns *ns)
 	int srcu_idx;
 
 	srcu_idx = srcu_read_lock(&head->srcu);
-	list_for_each_entry_rcu(ns, &head->list, siblings) {
+	list_for_each_entry_srcu(ns, &head->list, siblings,
+				 srcu_read_lock_held(&head->srcu)) {
 		if (capacity != get_capacity(ns->disk))
 			clear_bit(NVME_NS_READY, &ns->flags);
 	}
@@ -257,7 +260,8 @@ static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
 	int found_distance = INT_MAX, fallback_distance = INT_MAX, distance;
 	struct nvme_ns *found = NULL, *fallback = NULL, *ns;
 
-	list_for_each_entry_rcu(ns, &head->list, siblings) {
+	list_for_each_entry_srcu(ns, &head->list, siblings,
+				 srcu_read_lock_held(&head->srcu)) {
 		if (nvme_path_is_disabled(ns))
 			continue;
 
@@ -356,7 +360,8 @@ static struct nvme_ns *nvme_queue_depth_path(struct nvme_ns_head *head)
 	unsigned int min_depth_opt = UINT_MAX, min_depth_nonopt = UINT_MAX;
 	unsigned int depth;
 
-	list_for_each_entry_rcu(ns, &head->list, siblings) {
+	list_for_each_entry_srcu(ns, &head->list, siblings,
+				 srcu_read_lock_held(&head->srcu)) {
 		if (nvme_path_is_disabled(ns))
 			continue;
 
@@ -424,7 +429,8 @@ static bool nvme_available_path(struct nvme_ns_head *head)
 	if (!test_bit(NVME_NSHEAD_DISK_LIVE, &head->flags))
 		return NULL;
 
-	list_for_each_entry_rcu(ns, &head->list, siblings) {
+	list_for_each_entry_srcu(ns, &head->list, siblings,
+				 srcu_read_lock_held(&head->srcu)) {
 		if (test_bit(NVME_CTRL_FAILFAST_EXPIRED, &ns->ctrl->flags))
 			continue;
 		switch (nvme_ctrl_state(ns->ctrl)) {
@@ -783,7 +789,8 @@ static int nvme_update_ana_state(struct nvme_ctrl *ctrl,
 		return 0;
 
 	srcu_idx = srcu_read_lock(&ctrl->srcu);
-	list_for_each_entry_rcu(ns, &ctrl->namespaces, list) {
+	list_for_each_entry_srcu(ns, &ctrl->namespaces, list,
+				 srcu_read_lock_held(&ctrl->srcu)) {
 		unsigned nsid;
 again:
 		nsid = le32_to_cpu(desc->nsids[n]);