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>

diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index fa211d80fc0a1e4e37603b1455184cbee7da6e56..92c64d162a92457c468e46f8cc15472febf0cfc7 100644 (file)
--- 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