Re: [PATCH v2] mm/page_owner: warn when stack trace depth hits PAGE_OWNER_STACK_DEPTH limit

[Andrew Morton <akpm@linux-foundation.org>]

On Sun, 29 Mar 2026 05:44:08 +0800 Jiayuan Liang <ljykernel@163.com> wrote:

> page_owner silently truncates stack traces deeper than
> PAGE_OWNER_STACK_DEPTH (16), which hides root caller information during
> memory debugging.
> 
> Add a ratelimited warning to notify developers when this truncation occurs.
> 
> ...
>
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -163,6 +163,9 @@ static noinline depot_stack_handle_t save_stack(gfp_t flags)
>  
>  	set_current_in_page_owner();
>  	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
> +	if (nr_entries >= PAGE_OWNER_STACK_DEPTH)
> +		pr_warn_ratelimited("page_owner: stack depth %u exceeds limit %u\n",
> +			nr_entries, PAGE_OWNER_STACK_DEPTH);
>  	handle = stack_depot_save(entries, nr_entries, flags);
>  	if (!handle)
>  		handle = failure_handle;

Is it ideal to emit this warning in real time?  Would it be better to
tell the user "this was truncated" when they actually _use_ the data? 
Presumably this would require alteration to page_owner_sort.c and
page_owner.rst.