On Wed, Mar 05, 2025 at 10:15:57AM -0800, 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@xxxxxxxxxx>
> ---
> mm/madvise.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index dbc8fec05cc6..4a91590656dc 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1633,6 +1633,17 @@ static bool is_valid_madvise(unsigned long start, size_t len_in, int behavior)
> return true;
> }
>
> +static bool is_memory_populate(int behavior)
No strong opinion on this patch but if you want to keep it, the above
name feels weird. How about either is_madvise_populate() or
is_populate_memory()?
> +{
> + 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)
> {
> @@ -1646,16 +1657,11 @@ 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_memory_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
