diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 84fa004..648f475 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -143,10 +143,12 @@
  *
  * @vma:      vma that holds the pte pointing to page
  * @addr:     address the old @page is mapped at
- * @page:     the cowed page we are replacing by kpage
- * @kpage:    the modified page we replace page by
+ * @old_page: the page we are replacing by new_page
+ * @new_page: the modified page we replace page by
  *
- * Returns 0 on success, -EFAULT on failure.
+ * If @new_page is NULL, only unmap @old_page.
+ *
+ * Returns 0 on success, negative error code otherwise.
  */
 static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
 				struct page *old_page, struct page *new_page)
@@ -166,10 +168,12 @@
 
 	VM_BUG_ON_PAGE(PageTransHuge(old_page), old_page);
 
-	err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL, &memcg,
-			false);
-	if (err)
-		return err;
+	if (new_page) {
+		err = mem_cgroup_try_charge(new_page, vma->vm_mm, GFP_KERNEL,
+					    &memcg, false);
+		if (err)
+			return err;
+	}
 
 	/* For try_to_free_swap() and munlock_vma_page() below */
 	lock_page(old_page);
@@ -177,15 +181,20 @@
 	mmu_notifier_invalidate_range_start(&range);
 	err = -EAGAIN;
 	if (!page_vma_mapped_walk(&pvmw)) {
-		mem_cgroup_cancel_charge(new_page, memcg, false);
+		if (new_page)
+			mem_cgroup_cancel_charge(new_page, memcg, false);
 		goto unlock;
 	}
 	VM_BUG_ON_PAGE(addr != pvmw.address, old_page);
 
-	get_page(new_page);
-	page_add_new_anon_rmap(new_page, vma, addr, false);
-	mem_cgroup_commit_charge(new_page, memcg, false, false);
-	lru_cache_add_active_or_unevictable(new_page, vma);
+	if (new_page) {
+		get_page(new_page);
+		page_add_new_anon_rmap(new_page, vma, addr, false);
+		mem_cgroup_commit_charge(new_page, memcg, false, false);
+		lru_cache_add_active_or_unevictable(new_page, vma);
+	} else
+		/* no new page, just dec_mm_counter for old_page */
+		dec_mm_counter(mm, MM_ANONPAGES);
 
 	if (!PageAnon(old_page)) {
 		dec_mm_counter(mm, mm_counter_file(old_page));
@@ -194,8 +203,9 @@
 
 	flush_cache_page(vma, addr, pte_pfn(*pvmw.pte));
 	ptep_clear_flush_notify(vma, addr, pvmw.pte);
-	set_pte_at_notify(mm, addr, pvmw.pte,
-			mk_pte(new_page, vma->vm_page_prot));
+	if (new_page)
+		set_pte_at_notify(mm, addr, pvmw.pte,
+				  mk_pte(new_page, vma->vm_page_prot));
 
 	page_remove_rmap(old_page, false);
 	if (!page_mapped(old_page))
@@ -488,6 +498,10 @@
 		ref_ctr_updated = 1;
 	}
 
+	ret = 0;
+	if (!is_register && !PageAnon(old_page))
+		goto put_old;
+
 	ret = anon_vma_prepare(vma);
 	if (ret)
 		goto put_old;
@@ -501,8 +515,30 @@
 	copy_highpage(new_page, old_page);
 	copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
 
+	if (!is_register) {
+		struct page *orig_page;
+		pgoff_t index;
+
+		VM_BUG_ON_PAGE(!PageAnon(old_page), old_page);
+
+		index = vaddr_to_offset(vma, vaddr & PAGE_MASK) >> PAGE_SHIFT;
+		orig_page = find_get_page(vma->vm_file->f_inode->i_mapping,
+					  index);
+
+		if (orig_page) {
+			if (PageUptodate(orig_page) &&
+			    pages_identical(new_page, orig_page)) {
+				/* let go new_page */
+				put_page(new_page);
+				new_page = NULL;
+			}
+			put_page(orig_page);
+		}
+	}
+
 	ret = __replace_page(vma, vaddr, old_page, new_page);
-	put_page(new_page);
+	if (new_page)
+		put_page(new_page);
 put_old:
 	put_page(old_page);