diff --git a/lib/Makefile b/lib/Makefile
index 320ac46a..45477c2 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -242,3 +242,4 @@
 obj-$(CONFIG_SBITMAP) += sbitmap.o
 
 obj-$(CONFIG_PARMAN) += parman.o
+obj-m += test-cfu.o
diff --git a/lib/test-cfu.c b/lib/test-cfu.c
new file mode 100644
index 0000000..219fc82
--- /dev/null
+++ b/lib/test-cfu.c
@@ -0,0 +1,107 @@
+/*
+ *
+ * Copyright (c) 2014 Samsung Electronics Co., Ltd.
+ * Author: Andrey Ryabinin <a.ryabinin@samsung.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#define pr_fmt(fmt) "cfu test: %s " fmt, __func__
+
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+
+static char pat[2 * PAGE_SIZE];
+static void run_test(int n, int m, char __user *up, char *kp)
+{
+	int i;
+	for (i = 0; i < 4; i++) {
+		int r;
+		memset(kp, 0, 2 * PAGE_SIZE);
+		r = __copy_from_user_inatomic(kp + i, up, m);
+		if (m <= n) {
+			if (r) {
+				pr_err("bogus fault (%d, %d, %d)\n", r, m, n);
+				return;
+			}
+		} else {
+			if (r < m - n) {
+				pr_err("claims too much (%d, %d, %d)\n", r, m, n);
+				return;
+			}
+		}
+		r = m - r;	/* claim to have copied that much */
+		if (memcmp(kp + i, pat + PAGE_SIZE - n, r)) {
+			int j;
+			pr_err("crap in copy (%d, %d, %d)", r, m, n);
+			for (j = 0; j < r; j++) {
+				if (!kp[i+j]) {
+					if (!memcmp(kp + i + j, pat + PAGE_SIZE, PAGE_SIZE)) {
+						pr_cont(" only %d copied\n", j);
+						return;
+					}
+					break;
+				}
+			}
+			pr_cont("\n");
+			return;
+		}
+		if (memcmp(kp + i + r, pat + PAGE_SIZE, PAGE_SIZE)) {
+			pr_err("crap after copy (%d, %d, %d)\n", r, m, n);
+			return;
+		}
+	}
+}
+
+static int __init cfu_test(void)
+{
+	char *kp;
+	char __user *up;
+	int i;
+
+	kp = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
+	if (!kp)
+		return -EAGAIN;
+
+	up = (char __user *)vm_mmap(NULL, 0, 2 * PAGE_SIZE,
+			    PROT_READ | PROT_WRITE | PROT_EXEC,
+			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
+	if (IS_ERR(up)) {
+		pr_err("Failed to allocate user memory\n");
+		kfree(kp);
+		return -EAGAIN;
+	}
+	vm_munmap((unsigned long)up + PAGE_SIZE, PAGE_SIZE);
+
+	for (i = 0; i < PAGE_SIZE; i++)
+		pat[i] = 128 | i;
+	if (copy_to_user(up, pat, PAGE_SIZE)) {
+		pr_err("failed to copy to user memory\n");
+		goto out;
+	}
+
+	for (i = 0; i <= 128; i++) {
+		int j;
+		pr_err("trying %d\n", i);
+		for (j = 0; j <= 128; j++)
+			run_test(i, j, up + PAGE_SIZE - i, kp);
+	}
+
+out:
+	vm_munmap((unsigned long)up, PAGE_SIZE);
+	kfree(kp);
+	return -EAGAIN;
+}
+
+module_init(cfu_test);
+MODULE_LICENSE("GPL");