Re: [PATCH 5/7] mm/mglru: use explicit tier range in read_ctrl_pos()

[Kairui Song]

On Thu, Aug 20, 2026 at 10:34 AM Ridong Chen <ridong.chen@xxxxxxxxx> wrote:
> On 8/18/2026 1:38 PM, Kairui Song via B4 Relay wrote:
> > From: Kairui Song <kasong@xxxxxxxxxxx>
> >
> > read_ctrl_pos() encodes the tier range in a single "tier" parameter
> > via "tier % MAX_NR_TIERS" as the start and "min(tier, MAX_NR_TIERS-1)"
> > as the end. This is hard to follow, maintain, or extend. Tier values
> > 0..3 select a single tier, while tier == MAX_NR_TIERS selects the
> > full range.
> >
> > Replace it with explicit (tier_min, tier_max) parameters using a
> > closed [tier_min, tier_max] interval, and add LRU_TIER_MIN and
> > LRU_TIER_MAX for the tier bounds. The call sites now become
> > self-documenting:
> >
> >    - get_tier_idx:   (LRU_TIER_MIN, LRU_TIER_MIN) for the first tier,
> >                      (tier, tier) for each subsequent tier
> >    - get_type_to_scan: (LRU_TIER_MIN, LRU_TIER_MAX) for the full range
> >
> > No functional change.
> >
>
> Just like LRU_GEN_MAX and MAX_NR_GENS issue.
> Why do we have to add LRU_TIER_MAX, can we just use [tier_min, MAX_NR_TIERS)?
>

I did that previously, but reviewer suggested LRU_TIER_MAX, :D

I'm fine either way, it's really trivial.