NFSv4.1: Convert pNFS deviceid to use kfree_rcu()

Use of synchronize_rcu() when unmounting and potentially freeing a lot
of deviceids is problematic. There really is no reason why we can't just
use kfree_rcu() here.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/objlayout/objio_osd.c

@@ -57,7 +57,7 @@ objio_free_deviceid_node(struct nfs4_deviceid_node *d)
 
 	dprintk("%s: free od=%p\n", __func__, de->od.od);
 	osduld_put_device(de->od.od);
-	kfree(de);
+	kfree_rcu(d, rcu);
 }
 
 struct objio_segment {