Re: [PATCH v9 06/14] mm: multi-gen LRU: minimal implementation

[Barry Song]

> +static int folio_inc_gen(struct lruvec *lruvec, struct folio *folio, bool reclaiming)
> +{
> +       unsigned long old_flags, new_flags;
> +       int type = folio_is_file_lru(folio);
> +       struct lru_gen_struct *lrugen = &lruvec->lrugen;
> +       int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
> +
> +       do {
> +               new_flags = old_flags = READ_ONCE(folio->flags);
> +               VM_BUG_ON_FOLIO(!(new_flags & LRU_GEN_MASK), folio);
> +
> +               new_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
> +               new_gen = (old_gen + 1) % MAX_NR_GENS;

new_gen is assigned twice, i assume you mean
               old_gen = ((new_flags & LRU_GEN_MASK) >> LRU_GEN_PGOFF) - 1;
               new_gen = (old_gen + 1) % MAX_NR_GENS;

or do you always mean new_gen =  lru_gen_from_seq(min_seq) + 1?

> +
> +               new_flags &= ~LRU_GEN_MASK;
> +               new_flags |= (new_gen + 1UL) << LRU_GEN_PGOFF;
> +               new_flags &= ~(LRU_REFS_MASK | LRU_REFS_FLAGS);
> +               /* for folio_end_writeback() */
> +               if (reclaiming)
> +                       new_flags |= BIT(PG_reclaim);
> +       } while (cmpxchg(&folio->flags, old_flags, new_flags) != old_flags);
> +
> +       lru_gen_update_size(lruvec, folio, old_gen, new_gen);
> +
> +       return new_gen;
> +}
> +

Thanks
Barry