From 776f729c86a929eb3543bbcc8bc02e708fbff113 Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sun, 14 Jun 2015 20:23:41 +0000
Subject: [PATCH] Invalid pages do not need neither update of the activation
 count nor they coould be dirty.  Move the handling if the invalid pages in
 the inactive scan earlier.

Remove some code duplication in the scan by introducing the
'drop_page' label, which centralizes the object and the page unlock.

Suggested and reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
---
 sys/vm/vm_pageout.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index 6bfd50ca0f5..bd77500ecbe 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1158,6 +1158,17 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
 		vm_pagequeue_unlock(pq);
 		queues_locked = FALSE;
 
+		/*
+		 * Invalid pages can be easily freed. They cannot be
+		 * mapped, vm_page_free() asserts this.
+		 */
+		if (m->valid == 0 && m->hold_count == 0) {
+			vm_page_free(m);
+			PCPU_INC(cnt.v_dfree);
+			--page_shortage;
+			goto drop_page;
+		}
+
 		/*
 		 * We bump the activation count if the page has been
 		 * referenced while in the inactive queue.  This makes
@@ -1192,15 +1203,10 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
 				queues_locked = TRUE;
 				vm_page_requeue_locked(m);
 			}
-			VM_OBJECT_WUNLOCK(object);
-			vm_page_unlock(m);
-			goto relock_queues;
+			goto drop_page;
 		}
 
 		if (m->hold_count != 0) {
-			vm_page_unlock(m);
-			VM_OBJECT_WUNLOCK(object);
-
 			/*
 			 * Held pages are essentially stuck in the
 			 * queue.  So, they ought to be discounted
@@ -1209,7 +1215,7 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
 			 * loop over the active queue below.
 			 */
 			addl_page_shortage++;
-			goto relock_queues;
+			goto drop_page;
 		}
 
 		/*
@@ -1224,14 +1230,7 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
 		if (m->dirty == 0 && object->ref_count != 0)
 			pmap_remove_all(m);
 
-		if (m->valid == 0) {
-			/*
-			 * Invalid pages can be easily freed
-			 */
-			vm_page_free(m);
-			PCPU_INC(cnt.v_dfree);
-			--page_shortage;
-		} else if (m->dirty == 0) {
+		if (m->dirty == 0) {
 			/*
 			 * Clean pages can be freed.
 			 */
@@ -1305,6 +1304,7 @@ vm_pageout_scan(struct vm_domain *vmd, int pass)
 			vm_page_lock_assert(m, MA_NOTOWNED);
 			goto relock_queues;
 		}
+drop_page:
 		vm_page_unlock(m);
 		VM_OBJECT_WUNLOCK(object);
 relock_queues: