Re: [PATCH 1/2] mm/damon/core: initialize damos_quota_goal->last_psi_total

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:

New issues:
- [Low] Implicit declaration of function 'damos_get_some_mem_psi_total' causes a compilation error.

Pre-existing issues:
- [High] The DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP metric's 'nid' field is not copied when committing a quota goal parameter update, leading to an uninitialized node ID being used for eligible memory queries.
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commit 9597a197ecbd4f36e4fa8dfa9bd1bdbb5a5f1d93
Author: SJ Park <sj@kernel.org>

mm/damon/core: initialize damos_quota_goal->last_psi_total

Initializes the last_psi_total field at the beginning of kdamond and during
each commit for SOME_MEM_PSI_US type quota goals. This prevents unexpected
adjustments during the first iteration of the feedback loop.

Link: https://lore.kernel.org/20260718005316.89585-1-sj@kernel.org

> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index 644daf5a16560..6f360d61390ad 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -1122,6 +1122,9 @@ static void damos_commit_quota_goal_union(
>  		struct damos_quota_goal *dst, struct damos_quota_goal *src)
>  {
>  	switch (dst->metric) {
> +	case DAMOS_QUOTA_SOME_MEM_PSI_US:
> +		dst->last_psi_total = damos_get_some_mem_psi_total();

[Severity: Low]
Does this cause a compilation error due to an implicit function declaration?

The function damos_get_some_mem_psi_total() is called here, but it appears
to be defined later in mm/damon/core.c without a prior forward declaration.

> +		break;
>  	case DAMOS_QUOTA_NODE_MEM_USED_BP:
>  	case DAMOS_QUOTA_NODE_MEM_FREE_BP:
>  		dst->nid = src->nid;

[Severity: High]
This is a pre-existing issue, but does this switch statement omit the
DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP metric?

When a user configures a DAMOS quota goal using the
DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP metric via sysfs, a new quota goal is
allocated in damos_new_quota_goal() via kmalloc_obj(), where the memory is
not zeroed. 

Because DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP is missing from the switch statement
in damos_commit_quota_goal_union(), its nid field is not copied over during
parameter updates. This leaves the node ID uninitialized and potentially
causes eligible memory queries to evaluate using garbage data, completely
breaking the metric's functionality.

[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20260827042920.93580-1-sj@kernel.org?part=1