NFS: Fix memroy leak for double mounts

When double mounting same nfs filesystem, the devname saved in d_fsdata
will be lost.The second mount should not change the devname that
be saved in d_fsdata.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/getroot.c b/fs/nfs/getroot.c
index 66984a9..b94f804 100644
--- a/fs/nfs/getroot.c
+++ b/fs/nfs/getroot.c
@@ -120,7 +120,8 @@
 
 	security_d_instantiate(ret, inode);
 	spin_lock(&ret->d_lock);
-	if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
+	if (IS_ROOT(ret) && !ret->d_fsdata &&
+	    !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
 		ret->d_fsdata = name;
 		name = NULL;
 	}