Re: [PATCH] mm/damon: validate addr_unit to be power of 2

[SeongJae Park <sj@kernel.org>]

On Fri, 27 Mar 2026 22:56:27 +0800 Liew Rui Yan <aethernet65535@gmail.com> wrote:

> Hi SeongJae,
> 
> Thank you for the detailed explaination and for pointing out the
> 'PAGE_SIZE' limitation. You are right; and I should have accounted for
> that.
> 
> However, I performend further testing to address your confusion
> regarding kdamond's termination. My patch didn't fix anything.
> 
> Here is my reproduction:
> 
> # Log (Both with and without this patch):
> 
> 	# cd /sys/module/damon_lru_sort/parameters/
> 	# echo Y > enabled 
> 	# echo 3 > addr_unit 
> 	# ps aux | rg "[k]damond"
> 	root    71  0.0 0.0 0   0   ?   I   22:26   0:00 [kdamond.0]
> 	# echo Y > commit_inputs 
> 	bash: echo: write error: Invalid argument
> 	# cat kdamond_pid 
> 	71
> 	# ps aux | rg "[k]damond"
> 	# ... kdamond terminated
> 
> I am very sorry for the noise caused by my misunderstanding of the
> sashiko review.
> 
> The real question I am facing now is:
> Should kdamond terminate itself when damon_commit_ctx() fails due to
> invalid user inputs?

It would be better to not terminate.  But not a big deal.  Users could be wary
of the consequence, as long as it is well documented.

From my perspective, therefore, code maintenance is more important.  If we can
make DAMON not terminated by invalid user inputs caused damon_commit_ctx() but
it introduces a significant amount of code complexity, I don't think that's a
good deal.


Thanks,
SJ

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