Re: [PATCH 2/9] mm/madvise: split out populate behavior check logic

Lorenzo Stoakes
2025-03-11T11:30:02Z

On Mon, Mar 10, 2025 at 10:23:11AM -0700, SeongJae Park wrote:
> madvise_do_behavior() has a long open-coded 'behavior' check for
> MADV_POPULATE_{READ,WRITE}. It adds multiple layers[1] and make the
> code arguably take longer time to read. Like is_memory_failure(), split
> out the check to a separate function. This is not technically removing
> the additional layer but discourage further extending the switch-case.
> Also it makes madvise_do_behavior() code shorter and therefore easier to
> read.
>
> [1] https://lore.kernel.org/bd6d0bf1-c79e-46bd-a810-9791efb9ad73@lucifer.local
>
> Signed-off-by: SeongJae Park <sj@kernel.org>

LGTM, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

> ---
> mm/madvise.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index c3ab1f283b18..611db868ae38 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1640,6 +1640,17 @@ static bool is_valid_madvise(unsigned long start, size_t len_in, int behavior)
> return true;
> }
>
> +static bool is_madvise_populate(int behavior)
> +{
> + switch (behavior) {
> + case MADV_POPULATE_READ:
> + case MADV_POPULATE_WRITE:
> + return true;
> + default:
> + return false;
> + }
> +}
> +
> static int madvise_do_behavior(struct mm_struct *mm,
> unsigned long start, size_t len_in, size_t len, int behavior)
> {
> @@ -1653,16 +1664,11 @@ static int madvise_do_behavior(struct mm_struct *mm,
> end = start + len;
>
> blk_start_plug(&plug);
> - switch (behavior) {
> - case MADV_POPULATE_READ:
> - case MADV_POPULATE_WRITE:
> + if (is_madvise_populate(behavior))
> error = madvise_populate(mm, start, end, behavior);
> - break;
> - default:
> + else
> error = madvise_walk_vmas(mm, start, end, behavior,
> madvise_vma_behavior);
> - break;
> - }
> blk_finish_plug(&plug);
> return error;
> }
> --
> 2.39.5