- Hold the page queues lock around vm_page_hold().

- Assert that the page queues lock rather than Giant is held in
   vm_page_hold().

sys/kern/vfs_bio.c

@@ -3579,7 +3579,9 @@ vmapbuf(struct buf *bp)
 		if (pa == 0)
 			panic("vmapbuf: page not present");
 		m = PHYS_TO_VM_PAGE(pa);
+		vm_page_lock_queues();
 		vm_page_hold(m);
+		vm_page_unlock_queues();
 		bp->b_pages[pidx] = m;
 	}
 	if (pidx > btoc(MAXPHYS))

sys/vm/vm_page.c

@@ -358,7 +358,8 @@ vm_page_io_finish(vm_page_t m)
 void
 vm_page_hold(vm_page_t mem)
 {
-        GIANT_REQUIRED;
+
+	mtx_assert(&vm_page_queue_mtx, MA_OWNED);
         mem->hold_count++;
 }