if (unlikely(fdt->fd[fd] != NULL)) BUG(); fdt->fd[fd] = file;
BUG_ON(fdt->fd[fd] != NULL); rcu_assign_pointer(fdt->fd[fd], file);
void fastcall fd_install(unsigned int fd, struct file * file){	struct files_struct *files = current->files;	struct fdtable *fdt;	spin_lock(&files->file_lock);	fdt = files_fdtable(files);	if (unlikely(fdt->fd[fd] != NULL))		BUG();	fdt->fd[fd] = file;	spin_unlock(&files->file_lock);}