[PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path

[Jianchao Wang]

With lockdep enabled, when trigger nvme_remove, suspicious RCU
usage warning will be printed out.
Fix it with adding srcu_read_lock/unlock in it.

Signed-off-by: Jianchao Wang <jianchao.w.w...@oracle.com>
---
 drivers/nvme/host/nvme.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 061fecf..d326c23 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -446,9 +446,14 @@ void nvme_mpath_remove_disk(struct nvme_ns_head *head);
 static inline void nvme_mpath_clear_current_path(struct nvme_ns *ns)
 {
        struct nvme_ns_head *head = ns->head;
+       int srcu_idx;
 
-       if (head && ns == srcu_dereference(head->current_path, &head->srcu))
-               rcu_assign_pointer(head->current_path, NULL);
+       if (head) {
+               srcu_idx = srcu_read_lock(&head->srcu);
+               if (ns == srcu_dereference(head->current_path, &head->srcu))
+                       rcu_assign_pointer(head->current_path, NULL);
+               srcu_read_unlock(&head->srcu, srcu_idx);
+       }
 }
 struct nvme_ns *nvme_find_path(struct nvme_ns_head *head);
 
-- 
2.7.4