Index: head/sys/vm/vm_object.h
===================================================================
--- head/sys/vm/vm_object.h
+++ head/sys/vm/vm_object.h
@@ -255,6 +255,10 @@
 	rw_wowned(&(object)->lock)
 #define	VM_OBJECT_WUNLOCK(object)					\
 	rw_wunlock(&(object)->lock)
+#define	VM_OBJECT_DROP(object)						\
+	lock_class_rw.lc_unlock(&(object)->lock.lock_object)
+#define	VM_OBJECT_PICKUP(object, state)					\
+	lock_class_rw.lc_lock(&(object)->lock.lock_object, (state))
 
 struct vnode;
 
Index: head/sys/vm/vm_pager.h
===================================================================
--- head/sys/vm/vm_pager.h
+++ head/sys/vm/vm_pager.h
@@ -151,7 +151,7 @@
 ) {
 	boolean_t ret;
 
-	VM_OBJECT_ASSERT_WLOCKED(object);
+	VM_OBJECT_ASSERT_LOCKED(object);
 	ret = (*pagertab[object->type]->pgo_haspage)
 	    (object, offset, before, after);
 	return (ret);
Index: head/sys/vm/vnode_pager.c
===================================================================
--- head/sys/vm/vnode_pager.c
+++ head/sys/vm/vnode_pager.c
@@ -355,13 +355,14 @@
 {
 	struct vnode *vp = object->handle;
 	daddr_t bn;
+	uintptr_t lockstate;
 	int err;
 	daddr_t reqblock;
 	int poff;
 	int bsize;
 	int pagesperblock, blocksperpage;
 
-	VM_OBJECT_ASSERT_WLOCKED(object);
+	VM_OBJECT_ASSERT_LOCKED(object);
 	/*
 	 * If no vp or vp is doomed or marked transparent to VM, we do not
 	 * have the page.
@@ -384,9 +385,9 @@
 		blocksperpage = (PAGE_SIZE / bsize);
 		reqblock = pindex * blocksperpage;
 	}
-	VM_OBJECT_WUNLOCK(object);
+	lockstate = VM_OBJECT_DROP(object);
 	err = VOP_BMAP(vp, reqblock, NULL, &bn, after, before);
-	VM_OBJECT_WLOCK(object);
+	VM_OBJECT_PICKUP(object, lockstate);
 	if (err)
 		return TRUE;
 	if (bn == -1)