Re: [RFC PATCH v1.1 3/5] mm/damon/vaddr: drop last same folio access check optimization

On Sun, 12 Jul 2026 17:10:09 +0000 [email protected] wrote:

> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] Unused parameter and dead code tracking logic left behind after removing optimization.
> --
> 
> --- Patch [3]: [RFC PATCH v1.1 3/5] mm/damon/vaddr: drop last same folio access check optimization ---
> commit 40e12defdea3b013644cc026283aa34cdd3ae2fb
> Author: SJ Park <[email protected]>
> mm/damon/vaddr: drop last same folio access check optimization
> 
> This commit removes the last same folio access check optimization from DAMON's
> virtual address space primitives. The optimization was found to cause race
> conditions when multiple kdamonds are running.
> 
> > diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
> > index d10b8042adb5b..16fe210d2042a 100644
> > --- a/mm/damon/vaddr.c
> > +++ b/mm/damon/vaddr.c
> 
> [ ... ]
> 
> > @@ -496,26 +489,15 @@ static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
> >  static void __damon_va_check_access(struct mm_struct *mm,
> >  				struct damon_region *r, bool same_target)
> >  {
> 
> [Severity: Low]
> Does this code still need the same_target parameter?
> 
> With the optimization removed below, the parameter is no longer used in
> __damon_va_check_access().
> 
> The caller, damon_va_check_accesses(), also still computes and tracks the local
> same_target variable on every iteration just to pass it here:
> 
> 	damon_for_each_target(t, ctx) {
> 		mm = damon_get_mm(t);
> 		same_target = false;
> 		damon_for_each_region(r, t) {
> 			__damon_va_check_access(mm, r, same_target);
> 			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
> 			same_target = true;
> 		}
> 		if (mm)
> 			mmput(mm);
> 	}
> 
> Could we remove the parameter and the dead tracking code in the caller as well?

Good finding.  I will drop that in the next revision.


Thanks,
SJ

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