[PATCH] md/linear: rcu_dereference outside read-lock section

According to the comment in linear_stop function
rcu_dereference in linear_start and linear_stop functions
occurs under reconfig_mutex. The patch represents this
agreement in code and prevents lockdep complaint.

Found by Linux Driver Verification project (linuxtesting.org)

Signed-off-by: Denis Efremov <redacted>
---
 drivers/md/linear.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index fa211d8..093f3e4 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c

@@ -244,7 +244,8 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
 	if (!newconf)
 		return -ENOMEM;
 
-	oldconf = rcu_dereference(mddev->private);
+	oldconf = rcu_dereference_protected(mddev->private,
+					    lockdep_is_held(&mddev->reconfig_mutex));
 	mddev->raid_disks++;
 	rcu_assign_pointer(mddev->private, newconf);
 	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));

@@ -256,7 +257,9 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
 
 static int linear_stop (struct mddev *mddev)
 {
-	struct linear_conf *conf = mddev->private;
+	struct linear_conf *conf =
+		rcu_dereference_protected(mddev->private,
+					  lockdep_is_held(&mddev->reconfig_mutex));
 
 	/*
 	 * We do not require rcu protection here since