Get inode and file given FD in the Linux kernel

get_inode.c

static void get_inode(u64 fd, struct file **p_file, struct inode **p_inode)
{
	struct file *file = NULL;
	struct inode *f_inode = NULL;
#if (LINUX_VERSION_CODE > KERNEL_VERSION(3,7,0))
	file = fget_raw(fd);   // do not forget to fput(file)
#elif (LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)) && (LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,255))
	{
		struct files_struct *files = current->files;
		if (files)   // This is always the case, but I am not taking chances
		{
			int lock_result = spin_trylock(&files->file_lock); // Can I run lockless? What files_fdtable() does?
			if (lock_result)
			{
				struct fdtable *fdt;
				fdt = files_fdtable(files);   // fdt is never NULL 
				if (fdt)
				{
					if (fd < fdt->max_fds)  // This can not be wrong in syscall open
					{
						file = fdt->fd[fd];  
					}
				}
				spin_unlock(&files->file_lock); // This is a bug - I continue to use 'file' after giving up the lock
			}
		}
	}
#else
#error Driver lacks support of the kernel in get_inode(). The agent will have to use stat() to get the file creation time of a file.
#endif
	if (file)
	{
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,9,0))
		f_inode = file->f_inode;
#else	
		f_inode = file->f_path.dentry->d_inode;
#endif
	}
	else
	{
		DEBUG_COUNTERS_BUMP(DEBUG_SYSCALL_OPEN_CREATED_ERR1);
	}
	
	*p_inode = f_inode;
	*p_file = file;
	return ;
}