Re: [PATCH v7 02/16] mm/mglru: extract lruvec_populated_min_seq() helper

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] mm/mglru: shadowed local variable seq in try_to_inc_min_seq()
--

commit 7a4927e9f0aa8623b1c83f69afd1fb935c342dd5
Author: Kairui Song <kasong@tencent.com>

mm/mglru: extract lruvec_populated_min_seq() helper

This commit extracts the search for the oldest populated generation of a
type from try_to_inc_min_seq() into a new lruvec_populated_min_seq()
helper.

> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index ed224cb80a75a..f98cd483f014a 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c

[ ... ]

>  static void try_to_inc_min_seq(struct lruvec *lruvec, int swappiness)
>  {
> -	int gen, type, zone;
> +	int type;
>  	bool seq_inc_flag = false;
>  	struct lru_gen_folio *lrugen = &lruvec->lrugen;
>  	DEFINE_MIN_SEQ(lruvec);
> +	unsigned long seq;
>  
>  	VM_WARN_ON_ONCE(!seq_is_valid(lruvec));
>  
> -	/* find the oldest populated generation */
> +	/* Requires at least MIN_NR_GENS gens for basic functionality */
> +	seq = lrugen->max_seq - MIN_NR_GENS;
>  	for_each_evictable_type(type, swappiness) {
> -		while (min_seq[type] + MIN_NR_GENS <= lrugen->max_seq) {
> -			gen = lru_gen_from_seq(min_seq[type]);
> -
> -			for (zone = 0; zone < MAX_NR_ZONES; zone++) {
> -				if (!list_empty(&lrugen->folios[gen][type][zone]))
> -					goto next;
> -			}
> -
> -			min_seq[type]++;
> +		min_seq[type] = lruvec_populated_min_seq(lruvec, type, seq + 1);
> +		if (min_seq[type] > lrugen->min_seq[type])
>  			seq_inc_flag = true;
> -		}
> -next:
> -		;
>  	}

[Severity: Low]
This isn't a bug, but adding seq at function scope causes the existing
inner declaration in try_to_inc_min_seq() to shadow it and recompute the
same value:

mm/vmscan.c:try_to_inc_min_seq() {
	...
	if (swappiness && swappiness <= MAX_SWAPPINESS) {
		unsigned long seq = lrugen->max_seq - MIN_NR_GENS;
	...
}

Dropping the inner declaration would avoid the -Wshadow warning under W=2
and reuse the value already computed.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261111232603.9934-1-baohua@kernel.org?part=2