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 <yefremov.denis@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index fa211d80fc0a..92c64d162a92 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -244,7 +244,9 @@ 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 +258,10 @@ 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