Kernel: Get filename from "struct file *"

char *tmp;
char *pathname;

path_get(&file->f_path);

tmp = (char *)__get_free_page(GFP_TEMPORARY);
if (!tmp) {
    return -ENOMEM;
}

pathname = d_path(&file->f_path, tmp, PAGE_SIZE);
path_put(&file->f_path);

if (IS_ERR(pathname)) {
    free_page((unsigned long)tmp);
    return PTR_ERR(pathname);
}

printk(KERN_WARNING "File name: %s\n", pathname);
free_page((unsigned long)tmp);