NFS: reduce latency by using conditional rescheduling in nfs_scan_list

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 68f6bf1..8d2642f 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -429,7 +429,8 @@
 					goto out;
 			}
 		}
-
+		/* for latency reduction */
+		cond_resched_lock(&nfsi->req_lock);
 	}
 out:
 	return res;