Assert that page is VPO_BUSY or page owner object is locked in

vm_page_undirty(). The assert is not precise due to VPO_BUSY owner
to tracked, so assertion does not catch the case when VPO_BUSY is
owned by other thread.

Reviewed by:	alc

2 files changed, 26 insertions, 0 deletions

diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index e2758ec..21c7080 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -2636,6 +2636,23 @@ vm_page_cowsetup(vm_page_t m)
 	return (0);
 }
 
+#ifdef INVARIANTS
+void
+vm_page_object_lock_assert(vm_page_t m)
+{
+
+	/*
+	 * Certain of the page's fields may only be modified by the
+	 * holder of the containing object's lock or the setter of the
+	 * page's VPO_BUSY flag.  Unfortunately, the setter of the
+	 * VPO_BUSY flag is not recorded, and thus cannot be checked
+	 * here.
+	 */
+	if (m->object != NULL && (m->oflags & VPO_BUSY) == 0)
+		VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
+}
+#endif
+
 #include "opt_ddb.h"
 #ifdef DDB
 #include <sys/kernel.h>
diff --git a/sys/vm/vm_page.h b/sys/vm/vm_page.h
index c34d2f0..898857b 100644
--- a/sys/vm/vm_page.h
+++ b/sys/vm/vm_page.h
@@ -383,6 +383,13 @@ void vm_page_cowfault (vm_page_t);
 int vm_page_cowsetup(vm_page_t);
 void vm_page_cowclear (vm_page_t);
 
+#ifdef INVARIANTS
+void vm_page_object_lock_assert(vm_page_t m);
+#define	VM_PAGE_OBJECT_LOCK_ASSERT(m)	vm_page_object_lock_assert(m)
+#else
+#define	VM_PAGE_OBJECT_LOCK_ASSERT(m)	(void)0
+#endif
+
 /*
  *	vm_page_sleep_if_busy:
  *
@@ -412,6 +419,8 @@ vm_page_sleep_if_busy(vm_page_t m, int also_m_busy, const char *msg)
 static __inline void
 vm_page_undirty(vm_page_t m)
 {
+
+	VM_PAGE_OBJECT_LOCK_ASSERT(m);
 	m->dirty = 0;
 }