From 0ec97ffc10844ba1c575e5d8c79c9259ff213749 Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Wed, 21 Jun 2017 18:54:28 +0000
Subject: [PATCH] Call pmap_copy() only for map entries which have the backing
 object instantiated.

Calling pmap_copy() on non-faulted anonymous memory entries is useless.

Noted and reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
---
 sys/vm/vm_map.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
index 86d17aeddea..ce03eb4c3e8 100644
--- a/sys/vm/vm_map.c
+++ b/sys/vm/vm_map.c
@@ -3239,6 +3239,10 @@ vm_map_copy_entry(
 				fake_entry->next = curthread->td_map_def_user;
 				curthread->td_map_def_user = fake_entry;
 			}
+
+			pmap_copy(dst_map->pmap, src_map->pmap,
+			    dst_entry->start, dst_entry->end - dst_entry->start,
+			    src_entry->start);
 		} else {
 			dst_entry->object.vm_object = NULL;
 			dst_entry->offset = 0;
@@ -3248,9 +3252,6 @@ vm_map_copy_entry(
 				*fork_charge += size;
 			}
 		}
-
-		pmap_copy(dst_map->pmap, src_map->pmap, dst_entry->start,
-		    dst_entry->end - dst_entry->start, src_entry->start);
 	} else {
 		/*
 		 * We don't want to make writeable wired pages copy-on-write.