Btrfs: using rcu lock in the reader side of devices list

fs_devices->devices is only updated on remove and add device paths, so we can
use rcu to protect it in the reader side

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index cc2eadaf7a27..f1b2e4f53fc2 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -86,6 +86,8 @@ struct btrfs_device {
         u8 uuid[BTRFS_UUID_SIZE];
 
         struct btrfs_work work;
+        struct rcu_head rcu;
+        struct work_struct rcu_work;
 };
 
 struct btrfs_fs_devices {