NFS: Add a ->migratepage() aop for NFS

Make NFS a bit more friendly to NUMA and memory hot removal...

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 0506232..dfc8967 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -479,6 +479,7 @@
 	.invalidatepage = nfs_invalidate_page,
 	.releasepage = nfs_release_page,
 	.direct_IO = nfs_direct_IO,
+	.migratepage = nfs_migrate_page,
 	.launder_page = nfs_launder_page,
 };