Re: [patch 3/7] procfs: Add ability to plug in auxiliary fdinfo providers

[Pavel Emelyanov <xemul@parallels.com>]

> +static int prep_fdinfo_driver(struct proc_fdinfo_extra *extra)
> +{
> +	struct proc_fdinfo_driver *s;
> +
> +	down_read(&fdinfo_drivers_sem);
> +	list_for_each_entry(s, &fdinfo_drivers, list) {
> +		if (s->probe(extra->f_file)) {
> +			extra->driver = s;
> +			break;
> +		}
> +	}
> +	up_read(&fdinfo_drivers_sem);
> +
> +	return 0;
> +}

Maybe a simple list of file_operations:seq_operations mappings would be simpler?

> +static void *seq_next(struct seq_file *m, void *p, loff_t *pos)
> +{
> +	struct proc_fdinfo_extra *extra = m->private;
> +	void *v = NULL;
> +
> +	if (extra->driver) {
> +		int ret = 0;
> +
> +		if (*pos == 0) {
> +			v = extra->driver->ops->start(m, pos);
> +			if (v) {
> +				ret = extra->driver->ops->show(m, v);

Why is it necessary to call ->show here? The logic should be

seq_start = (pos == 0 ? nop : extra->start)
seq_next  = (pos == 0 ? extra->start : extra->next)
seq_stop  = (pos == 0 ? nop : extra->stop)
seq_show  = (pos == 0 ? proc_show : extra->show)

Or I'm missing something?

Thanks,
Pavel