diff --git a/kernel_module/anonymous_inode.c b/kernel_module/anonymous_inode.c
index 77eb7ef..7fc0740 100644
--- a/kernel_module/anonymous_inode.c
+++ b/kernel_module/anonymous_inode.c
@@ -24,7 +24,7 @@ which reduces namespace pollution.
 
 MODULE_LICENSE("GPL");
 
-static struct dentry *dir;
+static struct dentry *debugfs_file;
 
 static ssize_t read(struct file *filp, char __user *buf, size_t len, loff_t *off)
 {
@@ -72,14 +72,13 @@ static const struct file_operations fops_ioctl = {
 
 static int myinit(void)
 {
-	dir = debugfs_create_dir("lkmc_anonymous_inode", 0);
-	debugfs_create_file("f", 0, dir, NULL, &fops_ioctl);
+	debugfs_file = debugfs_create_file("lkmc_anonymous_inode", 0, NULL, NULL, &fops_ioctl);
 	return 0;
 }
 
 static void myexit(void)
 {
-	debugfs_remove_recursive(dir);
+	debugfs_remove(debugfs_file);
 }
 
 module_init(myinit)
diff --git a/kernel_module/fops.c b/kernel_module/fops.c
index b0dd3bb..3f8d47a 100644
--- a/kernel_module/fops.c
+++ b/kernel_module/fops.c
@@ -28,7 +28,7 @@ Here we use debugfs.
 
 MODULE_LICENSE("GPL");
 
-static struct dentry *dir;
+static struct dentry *debugfs_file;
 static char data[] = {'a', 'b', 'c', 'd'};
 
 static int open(struct inode *inode, struct file *filp)
@@ -143,14 +143,13 @@ static const struct file_operations fops = {
 
 static int myinit(void)
 {
-	dir = debugfs_create_dir("lkmc_fops", 0);
-	debugfs_create_file("f", S_IRUSR | S_IWUSR, dir, NULL, &fops);
+	debugfs_file = debugfs_create_file("lkmc_fops", S_IRUSR | S_IWUSR, NULL, NULL, &fops);
 	return 0;
 }
 
 static void myexit(void)
 {
-	debugfs_remove_recursive(dir);
+	debugfs_remove_recursive(debugfs_file);
 }
 
 module_init(myinit)
diff --git a/kernel_module/ioctl.c b/kernel_module/ioctl.c
index fe68962..d507111 100644
--- a/kernel_module/ioctl.c
+++ b/kernel_module/ioctl.c
@@ -28,7 +28,7 @@ Documentation/ioctl/ioctl-number.txt has some info:
 
 MODULE_LICENSE("GPL");
 
-static struct dentry *dir;
+static struct dentry *debugfs_file;
 
 static long unlocked_ioctl(struct file *filp, unsigned int cmd, unsigned long argp)
 {
@@ -76,17 +76,16 @@ static const struct file_operations fops = {
 
 static int myinit(void)
 {
-	dir = debugfs_create_dir("lkmc_ioctl", 0);
 	/* ioctl permissions are not automatically restricted by rwx as for read / write,
 	 * but we could of course implement that ourselves:
 	 * https://stackoverflow.com/questions/29891803/user-permission-check-on-ioctl-command */
-	debugfs_create_file("f", 0, dir, NULL, &fops);
+	debugfs_file = debugfs_create_file("lkmc_ioctl", 0, NULL, NULL, &fops);
 	return 0;
 }
 
 static void myexit(void)
 {
-	debugfs_remove_recursive(dir);
+	debugfs_remove(debugfs_file);
 }
 
 module_init(myinit)
diff --git a/kernel_module/poll.c b/kernel_module/poll.c
index d582289..8b7b7d7 100644
--- a/kernel_module/poll.c
+++ b/kernel_module/poll.c
@@ -24,7 +24,7 @@ MODULE_LICENSE("GPL");
 
 static char readbuf[1024];
 static size_t readbuflen;
-static struct dentry *dir;
+static struct dentry *debugfs_file;
 static struct task_struct *kthread;
 static wait_queue_head_t waitqueue;
 
@@ -74,8 +74,8 @@ static const struct file_operations fops = {
 
 static int myinit(void)
 {
-	dir = debugfs_create_dir("lkmc_poll", 0);
-	debugfs_create_file("f", S_IRUSR | S_IWUSR, dir, NULL, &fops);
+	debugfs_file = debugfs_create_file(
+		"lkmc_poll", S_IRUSR | S_IWUSR, NULL, NULL, &fops);
 	init_waitqueue_head(&waitqueue);
 	kthread = kthread_create(kthread_func, NULL, "mykthread");
 	wake_up_process(kthread);
@@ -85,7 +85,7 @@ static int myinit(void)
 static void myexit(void)
 {
 	kthread_stop(kthread);
-	debugfs_remove_recursive(dir);
+	debugfs_remove(debugfs_file);
 }
 
 module_init(myinit)
diff --git a/kernel_module/seq_file_single.c b/kernel_module/seq_file_single.c
index 80ba920..cc60ff9 100644
--- a/kernel_module/seq_file_single.c
+++ b/kernel_module/seq_file_single.c
@@ -44,11 +44,7 @@ static int myinit(void)
 {
 	debugfs_file = debugfs_create_file(
 		"lkmc_seq_file_single", S_IRUSR, NULL, NULL, &fops);
-	if (debugfs_file) {
-		return 0;
-	} else {
-		return -EINVAL;
-	}
+	return 0;
 }
 
 static void myexit(void)
diff --git a/rootfs_overlay/anonymous_inode.sh b/rootfs_overlay/anonymous_inode.sh
index e10b237..d8d988b 100755
--- a/rootfs_overlay/anonymous_inode.sh
+++ b/rootfs_overlay/anonymous_inode.sh
@@ -1,6 +1,5 @@
 #!/bin/sh
 set -e
 insmod /anonymous_inode.ko
-cd /sys/kernel/debug/lkmc_anonymous_inode/
-/anonymous_inode.out f
+/anonymous_inode.out /sys/kernel/debug/lkmc_anonymous_inode
 rmmod anonymous_inode
diff --git a/rootfs_overlay/ioctl.sh b/rootfs_overlay/ioctl.sh
index ec3acd9..4c48308 100755
--- a/rootfs_overlay/ioctl.sh
+++ b/rootfs_overlay/ioctl.sh
@@ -1,6 +1,5 @@
 #!/bin/sh
 set -e
 insmod /ioctl.ko
-cd /sys/kernel/debug/lkmc_ioctl/
-/ioctl.out f
+/ioctl.out /sys/kernel/debug/lkmc_ioctl
 rmmod ioctl
diff --git a/rootfs_overlay/poll.sh b/rootfs_overlay/poll.sh
index 287ebfe..2301972 100755
--- a/rootfs_overlay/poll.sh
+++ b/rootfs_overlay/poll.sh
@@ -1,3 +1,3 @@
 #!/bin/sh
 insmod /poll.ko
-/poll.out /sys/kernel/debug/lkmc_poll/f
+/poll.out /sys/kernel/debug/lkmc_poll
diff --git a/rootfs_overlay/seq_file.sh b/rootfs_overlay/seq_file.sh
index 12be441..f29e506 100755
--- a/rootfs_overlay/seq_file.sh
+++ b/rootfs_overlay/seq_file.sh
@@ -25,3 +25,5 @@ dd if='lkmc_seq_file' bs=1 count=2 skip=2 status=none
 dd if='lkmc_seq_file' bs=4 count=1 skip=0 status=none
 # => 0
 # => 1
+
+rmmod seq_file
diff --git a/rootfs_overlay/seq_file_single.sh b/rootfs_overlay/seq_file_single.sh
index 48f4d00..795ef58 100755
--- a/rootfs_overlay/seq_file_single.sh
+++ b/rootfs_overlay/seq_file_single.sh
@@ -8,3 +8,5 @@ cat 'lkmc_seq_file_single'
 dd if='lkmc_seq_file_single' bs=1 count=3 skip=1
 # => b
 # => c
+
+rmmod seq_file_single