Re: [PATCH 05/12] mm/damon/sysfs: remove probes number validation

[SJ Park]

On Wed,  2 Sep 2026 22:07:13 +0800 Kunwu Chan <kunwu.chan@xxxxxxxxx> wrote:

> On Tue,  1 Sep 2026 22:47:38 -0700 SJ Park <sj@xxxxxxxxxx> wrote:
[...]
> I was wondering whether DAMON_MAX_PROBES is purely a core invariant
> or also an interface constraint.

Thank you for reviewing my patch and raising this question!

> 
> With this change, sysfs allows nr_probes larger than
> DAMON_MAX_PROBES and damon_sysfs_probes_add_dirs() will start creating
> probe objects before the configuration is later rejected by
> damon_valid_probe_params().
> 
> Since nr_probes directly controls the number of sysfs objects created,
> do we still want to keep an early check here?
> 
> I agree that the core validation is required for non-sysfs callers,
> but I am not sure whether this particular limit should be duplicated
> at the sysfs layer.

I agree the user experience may be not that good.

In my humble opinion, however, keeping code simplicity is more important than
the user experience here.  After all, DAMON_SYSFS is recommended to be used by
another high level tools like DAMON user-space tool (damo) rather than human
fingers.  The user-space tools like damo can do the early check.

Please feel free to let me know if you have any other opinions or questions.


Thanks,
SJ

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