Re: [PATCH] pidfd: add NSpid entries to fdinfo

On Mon, 2019-10-14 at 17:10 +0200, Jann Horn wrote:

On Mon, Oct 14, 2019 at 12:32 PM Christian Brauner wrote:

quoted

On Mon, Oct 14, 2019 at 11:43:01AM +0200, Christian Kellner wrote:
You could probably do:

#ifdef CONFIG_PID_NS
seq_put_decimal_ull(m, "\nNSpid:\t", nr);
for (i = ns->level + 1; i <= pid->level && nr; i++)
        seq_put_decimal_ull(m, "\t", pid->numbers[i].nr);
#endif

Personally, I dislike hiding the precondition for running the loop in
the loop statement like that. While it makes the code more concise,
it somewhat obfuscates the high-level logic at a first glance.

I agree and it has the side-effect of needing another #ifdef at the end
of the variable block for "i". I think I will go with:

if (nr) {
	int i;

	/* If nr is non-zero it means that 'pid' is valid and that
	 * ns, i.e. the pid namespace associated with the procfs
	 * instance, is in the pid namespace hierarchy of pid.
	 * Start at one below the already printed level.
	 */
	for (i = ns->level + 1; i <= pid->level; i++)
		seq_put_decimal_ull(m, "\t", pid->numbers[i].nr);
}

I will re-work the comment block and then send a new version of
the patch.

Thanks,
Christian