On Mon, Jan 16, 2023 at 06:11:00PM -0800, Amy Parker wrote:
> This patch uses a switch statement for pe_order, which improves
> readability and on some platforms may minorly improve performance. It
> also, to improve readability, recognizes that `PAGE_SHIFT - PAGE_SHIFT' is
> a constant, and uses 0 in its place instead.
>
> Signed-off-by: Amy Parker <apark0006@xxxxxxxxxxxxxxxxxxxx>
Hi Amy,
Thanks for the patch! Two problems. First, your mailer seems to have
mangled the patch; in my tree these are tab indents, and the patch has
arrived with four-space indents, so it can't be applied.
The second problem is that this function should simply not exist.
I forget how we ended up with enum page_entry_size, but elsewhere
we simply pass 'order' around. So what I'd really like to see is
a patch series that eliminates page_entry_size everywhere.
I can outline a way to do that in individual patches if that would be
helpful.
> fs/dax.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index c48a3a93ab29..e8beed601384 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -32,13 +32,16 @@
>
> static inline unsigned int pe_order(enum page_entry_size pe_size)
> {
> - if (pe_size == PE_SIZE_PTE)
> - return PAGE_SHIFT - PAGE_SHIFT;
> - if (pe_size == PE_SIZE_PMD)
> + switch (pe_size) {
> + case PE_SIZE_PTE:
> + return 0;
> + case PE_SIZE_PMD:
> return PMD_SHIFT - PAGE_SHIFT;
> - if (pe_size == PE_SIZE_PUD)
> + case PE_SIZE_PUD:
> return PUD_SHIFT - PAGE_SHIFT;
> - return ~0;
> + default:
> + return ~0;
> + }
> }
>
> /* We choose 4096 entries - same as per-zone page wait tables */
> --
> 2.39.0
