Re: [PATCH] mm/damon/core: Initialize sampling_addr in damon_new_region()

[SeongJae Park <sj@kernel.org>]

On Mon, 21 Apr 2025 11:39:19 +0800 Enze Li <lienze@kylinos.cn> wrote:

> Since sampling_addr is used across vaddr and paddr modules, initialize
> it in damon_new_region().
> 
> Signed-off-by: Enze Li <lienze@kylinos.cn>
> ---
>  mm/damon/core.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index f0c1676f0599..d197a5e3901c 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -128,6 +128,7 @@ struct damon_region *damon_new_region(unsigned long start, unsigned long end)
>  
>  	region->ar.start = start;
>  	region->ar.end = end;
> +	region->sampling_addr = 0;
>  	region->nr_accesses = 0;
>  	region->nr_accesses_bp = 0;
>  	INIT_LIST_HEAD(&region->list);

I unfortunately cannot find why this is required.  Is there a use case that
reads uninitialized sampling_addr or any problem that comes from the fact that
damon_new_regions() is not initializing the field?

Only operations set implementations write and read damon_region->sampling_addr,
so I was thinking not initializing the field on the core layer is no problem.
I will be happy to be corrected if I'm missing something.


Thanks,
SJ

> 
> base-commit: 9d7a0577c9db35c4cc52db90bc415ea248446472
> -- 
> 2.43.0