diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index a36db4a..f5ca965 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -806,6 +806,9 @@
 	struct clear_refs_private *cp = walk->private;
 	struct vm_area_struct *vma = walk->vma;
 
+	if (vma->vm_flags & VM_PFNMAP)
+		return 1;
+
 	/*
 	 * Writing 1 to /proc/pid/clear_refs affects all pages.
 	 * Writing 2 to /proc/pid/clear_refs only affects anonymous pages.