Re: [PATCH mm-unstable v2 1/2] mm/vmscan: fix missing NR_ISOLATED counter update in MGLRU reclaim path

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 8/17/26 3:11 PM, Hui Zhu wrote:
> From: Hui Zhu <zhuhui@kylinos.cn>
> 
> MGLRU evict_folios() isolates folios from the LRU without updating
> the NR_ISOLATED_ANON/FILE counters, unlike the legacy
> shrink_inactive_list() path. This causes compaction's
> too_many_isolated() check to under-count isolated pages when MGLRU
> reclaim is active.
> 
> Add NR_ISOLATED counter updates in evict_folios(): increment after
> isolate_folios() and decrement after all retry passes complete, using
> the existing nr_isolated which holds the original isolated count.
> 
> Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
> ---

Changes look good to me with one nit below.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

>   mm/vmscan.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index c1404a59523d..fdc45d7d8fba 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -4892,6 +4892,9 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
>   	scanned = isolate_folios(nr_to_scan, lruvec, sc, swappiness,
>   				 &list, &isolated, &type, &type_scanned);
>   	nr_isolated = isolated;
> +	if (nr_isolated)
> +		__mod_node_page_state(pgdat, NR_ISOLATED_ANON + type,
> +				      nr_isolated);
>   
>   	/* Scanning may have emptied the oldest gen, flush it */
>   	if (scanned)
> @@ -4954,6 +4957,10 @@ static int evict_folios(unsigned long nr_to_scan, struct lruvec *lruvec,
>   		goto retry;
>   	}
>   
> +	if (nr_isolated)

Nit: we can remove this check, since we never reach here if nr_isolated 
is 0.

> +		mod_node_page_state(pgdat, NR_ISOLATED_ANON + type,
> +				    -nr_isolated);
> +
>   	if (nr_isolated > total_reclaimed)
>   		mod_lruvec_state(lruvec, PGROTATE_ANON + type,
>   				 nr_isolated - total_reclaimed);