From 12a73f207a8a53ec84533b59555313b2a37efe06 Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Wed, 14 Oct 2015 09:03:32 +0000
Subject: [PATCH] Invalid pages should not appear on the inactive queue. 
 Change the check into an assertion.

Reviewed by:	alc
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
---
 sys/vm/vm_pageout.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index e0d00f5172f..5611ae66694 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1174,11 +1174,12 @@ unlock_page:
 		queues_locked = FALSE;
 
 		/*
-		 * Invalid pages can be easily freed. They cannot be
-		 * mapped, vm_page_free() asserts this.
+		 * Invalid pages cannot appear on a queue.  If
+		 * vm_pageout_fallback_object_lock() allowed a window
+		 * where the page could be invalidated, it should
+		 * detect this.
 		 */
-		if (m->valid == 0)
-			goto free_page;
+		KASSERT(m->valid != 0, ("Invalid page %p on inact queue", m));
 
 		/*
 		 * If the page has been referenced and the object is not dead,
@@ -1231,7 +1232,6 @@ unlock_page:
 			/*
 			 * Clean pages can be freed.
 			 */
-free_page:
 			vm_page_free(m);
 			PCPU_INC(cnt.v_dfree);
 			--page_shortage;