ceph: use READ_ONCE to access d_parent in RCU critical section

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 0b78507..88bc68d 100644 (file)
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -913,7 +913,7 @@ static int __choose_mds(struct ceph_mds_client *mdsc,
                struct inode *dir;
 
                rcu_read_lock();
-               parent = req->r_dentry->d_parent;
+               parent = READ_ONCE(req->r_dentry->d_parent);
                dir = req->r_parent ? : d_inode_rcu(parent);
 
                if (!dir || dir->i_sb != mdsc->fsc->sb) {
@@ -2145,7 +2145,7 @@ retry:
                        memcpy(path + pos, temp->d_name.name, temp->d_name.len);
                }
                spin_unlock(&temp->d_lock);
-               temp = temp->d_parent;
+               temp = READ_ONCE(temp->d_parent);
 
                /* Are we at the root? */
                if (IS_ROOT(temp))