linux-kernel - [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current

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Date:   Wed, 18 Apr 2018 15:32:47 +0800
From:   Jianchao Wang <jianchao.w.wang@...cle.com>
To:     keith.busch@...el.com, axboe@...com, hch@....de, sagi@...mberg.me,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] nvme: fix the suspicious RCU usage warning in nvme_mpath_clear_current_path

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.wang@...cle.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