Re: [PATCH 6.12.y 2/2] mm/damon/lru_sort: detect and use fresh enabled and kdamond_pid values

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The commit fixes a state synchronization bug in `mm/damon/lru_sort.c` but misses the identical bug in `mm/damon/reclaim.c`.
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commit 1cc3b4aed4385359f20cea12e2233bf01f20b6b6
Author: SeongJae Park <sj@kernel.org>

mm/damon/lru_sort: detect and use fresh enabled and kdamond_pid values

This commit updates DAMON_LRU_SORT to dynamically check the 'enabled' and
'kdamond_pid' statuses instead of relying on cached values. This prevents
a state synchronization bug where stale parameters could prevent restarting
DAMON after an unintentional stop.

Link: https://lore.kernel.org/20260419161003.79176-3-sj@kernel.org

> diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
> index 5654e31a198a4..4fdc5c76ff109 100644
> --- a/mm/damon/lru_sort.c
> +++ b/mm/damon/lru_sort.c
[ ... ]
> @@ -239,60 +230,93 @@ static int damon_lru_sort_turn(bool on)
[ ... ]
>  static int damon_lru_sort_enabled_store(const char *val,
>  		const struct kernel_param *kp)
>  {
> -	bool is_enabled = enabled;
> -	bool enable;
>  	int err;
>  
> -	err = kstrtobool(val, &enable);
> +	err = kstrtobool(val, &enabled);
>  	if (err)
>  		return err;
>  
> -	if (is_enabled == enable)
> +	if (damon_lru_sort_enabled() == enabled)
>  		return 0;

Should this same fix be applied to mm/damon/reclaim.c?

It appears DAMON LRU Sort and DAMON Reclaim share identical module parameter
logic. In mm/damon/reclaim.c, damon_reclaim_enabled_store() still uses the
cached enabled variable:

static int damon_reclaim_enabled_store(const char *val,
		const struct kernel_param *kp)
{
	bool is_enabled = enabled;
	bool enable;
	int err;

	err = kstrtobool(val, &enable);
	if (err)
		return err;

	if (is_enabled == enable)
		return 0;

If the kdamond thread stops automatically there, would leaving this identical
logic cause an issue where the stale enabled and kdamond_pid values prevent
the user from restarting it without a reboot?

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Sashiko AI review · https://sashiko.dev/#/patchset/2026051241-thievish-uncurious-73fe@gregkh?part=2