Re: [PATCH v2] mm/damon/paddr: initialize 'folio' variables to NULL for safety and clarity

[SeongJae Park <sj@kernel.org>]

On Sun,  4 Jan 2026 09:32:55 +0800 Aaron Yang <yangqixiao@inspur.com> wrote:

> In damon_pa_mark_accessed_or_deactivate(), damon_pa_pageout(),
> damon_pa_migrate(), and damon_pa_stat(), the local variable 'folio' is
> declared but not initialized.
> 
> Initialize 'folio' to NULL to:
> - Follow kernel convention: uninitialized pointers should be
>   explicitly NULL

Technically speaking, this is required only if it avoids unsafe code such as
use of the uninitialized pointers.  Because zero-length DAMON region is not
allowed, this is not the main reason of this change that we discussed on v1 of
this patch [1].

> - Improve code readability and maintainability

This is the main goal of this change.  This change allows readers be able to
know the function is safe, without have to know the fact that length DAMON
regions is disallowed.

> - Provide safe fallback (NULL assignment to s->last_applied is harmless
>   and callers check for NULL before dereference)
> 
> Signed-off-by: Aaron Yang <yangqixiao@inspur.com>

Because my above comments are for only clarifications of minor details:

Reviewed-by: SeongJae Park <sj@kernel.org>

> ---

FYI, this is a good place to summarize changes you made from the previous
version.  For more details, please refer to the doc [2].

[1] https://lore.kernel.org/20251231055737.73325-1-yangqixiao@inspur.com
[2] https://origin.kernel.org/doc/html/latest/process/submitting-patches.html#commentary


Thanks,
SJ

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