From: Venkatesh Srinivas <me@endeavour.zapto.org>
Date: Sat, 24 Sep 2011 13:41:13 +0000 (-0700)
Subject: kernel -- vm_page_dontneed: Fix interaction with vm_page_madvise and pagedaemon
X-Git-Tag: v2.12.0~17
X-Git-Url: http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/31da5e4d0cbd142b2ea4e6281890ee475f1f9711

kernel -- vm_page_dontneed: Fix interaction with vm_page_madvise and pagedaemon

vm_page_dontneed didn't clear the PG_REFERENCED flag on pages it is
deactivating. The pagedaemon would see references on the page (via
PG_REFERENCED) and reactivate it, undoing the effect of vm_page_dontneed.
---

diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index 91527c6..fe28554 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -1529,6 +1529,15 @@ vm_page_dontneed(vm_page_t m)
 		return;
 	}
 
+	/*
+	 * If vm_page_dontneed() is inactivating a page, it must clear
+	 * the referenced flag; otherwise the pagedaemon will see references
+	 * on the page in the inactive queue and reactivate it. Until the 
+	 * page can move to the cache queue, madvise's job is not done.
+	 */
+	vm_page_flag_clear(m, PG_REFERENCED);
+	pmap_clear_reference(m);
+
 	if (m->dirty == 0)
 		vm_page_test_dirty(m);