Opening a file from userspace from a Linux kernel module

I've been following a tutorial for opening files from userspace from a Linux kernel module at http://www.howtoforge.com/reading-files-from-the-linux-kernel-space-module-driver-fedora-14

The code is the following:

#include <linux/module.h>  // Needed by all modules
#include <linux/kernel.h>  // Needed for KERN_INFO
#include <linux/fs.h>      // Needed by filp
#include <asm/uaccess.h>   // Needed by segment descriptors

int init_module(void)
{
    // Create variables
    struct file *f;
    char buf[128];
    mm_segment_t fs;
    int i;
    // Init the buffer with 0
    for(i=0;i<128;i++)
        buf[i] = 0;
    // To see in /var/log/messages that the module is operating
    printk(KERN_INFO "My module is loadedn");
    // I am using Fedora and for the test I have chosen following file
    // Obviously it is much smaller than the 128 bytes, but hell with it =)
    f = filp_open("/etc/fedora-release", O_RDONLY, 0);
    if(f == NULL)
        printk(KERN_ALERT "filp_open error!!.n");
    else{
        // Get current segment descriptor
        fs = get_fs();
        // Set segment descriptor associated to kernel space
        set_fs(get_ds());
        // Read the file
        f->f_op->read(f, buf, 128, &f->f_pos);
        // Restore segment descriptor
        set_fs(fs);
        // See what we read from file
        printk(KERN_INFO "buf:%sn",buf);
    }
    filp_close(f,NULL);
    return 0;
}

void cleanup_module(void)
{
    printk(KERN_INFO "My module is unloadedn");
}

The code is copy-pasted from the link above. On my machine, running Fedora 19 with 3.11.10-200 kernel, it seems that filp_open isn't run, providing the buf variable with null values.

What could be wrong? I am still learning the ropes of Linux kernel module development.