Re: (sashiko review) [PATCH v4 1/2] mm/damon/lru_sort: validate min_region_size to be power of 2

[Liew Rui Yan <aethernet65535@gmail.com>]

On Fri, 10 Apr 2026 10:00:50 -0700 SeongJae Park <sj@kernel.org> wrote:

> On Sat, 11 Apr 2026 00:46:10 +0800 Liew Rui Yan <aethernet65535@gmail.com> wrote:
> 
> > On Fri, 10 Apr 2026 06:55:00 -0700 SeongJae Park <sj@kernel.org> wrote:
> > 
> > > On Fri, 10 Apr 2026 17:40:04 +0800 Liew Rui Yan <aethernet65535@gmail.com> wrote:
> > > 
> > > [...]
> > > 
> > > Agreed.  This was unclear to me in previous disucssions, though.  I still agree
> > > it is out of the scope of this patch.  But now I think we need to let users
> > > force-restart.  Adding this to my todo list.
> > 
> > Just to make sure - is this the same issue that my recent RFC patch [1]
> > aims to address? I want to make sure we're not duplicating efforts.
> 
> Hmm, this makes me confused about how we ended up working on this series, then.
> 
> > 
> > I'm still actively working on that patch, and I plan to send the next
> > version next week. I've been holding off because I didn't want to send
> > multiple patches in parallel.
> 
> Ok, seems I dropped a ball.  I was working like AI bot that only works with
> limited and nearly fresh context for each mail that on my inbox.  I will work
> on making another thing for tracking this kind of parallel works with good
> context.  But since I already dropped the ball for this, I'd like to make sure
> we are on the same page.  So I'd suggest below.
> 
> 1. Let's hold this patch series.  Andrew, please don't merge this for now until
>    this discussion is completed.
> 2. Please summarize your parallel works in progress with the context about how
>    you decided to do that in the way, with summaries of our previous
>    discussions.
> 
> Could you please do those, Liew?

TL;DR - There is no dependency between my parallel (2) works. I never
intended to merge these two works into a single series because they
address the problem at different level.

Yes, here is the summary of my parallel works and how I decided to
structure them.

My current parallel works
=========================
Series A - min_region_sz power-of-2 validation (this patch)
- Status: You gave Reviewed-by, asked Andrew to merge.
- Scope: Small, standalone fix for specific issue.
- Dependency: None

Series B - reset parameters (enabled/kdamond_pid) on unexpected
termination (RFC [1])
- Status: Preparing V2.
- Scope: Reset 'enabled' and 'kdamond_pid' when kdamond terminated
  unexpectedly.
- Dependency: None

Summary of Series B
===================
The design evolved through our discussion:
1. Extended 'struct damon_ctx' with 'thread_status' pointers
   - SJ pointed out: "This feels too much extension of core API for a
     problem that can more simply be fixed."

2. Alternative proposals discussed:
   - Option 1: Termination callback in core API (Too heavy for backport)
   - Option 2: Override '.get' operator for parameters (code duplication)
   - Option 3: On-demamd correction in enabled_store() (passive)

3. Final direction comfirmed:
   - SJ suggested: "Can't we catch damon_commit_ctx() failure from the
     calling place?"
   - We agreed: Simple, backportable fix is the priority.
   - Decision: Reset 'enabled' and 'kdamond_pid' immediately when
     damon_commit_ctx() fails, add a fallback in the damon_turn() 'N'
     path.

[1] https://lore.kernel.org/20260330164347.12772-1-aethernet65535@gmail.com

Best regards,
Rui Yan