Re: [PATCH 03/12] mm/pagewalk: Skip dax pages in pagewalk

Jason Gunthorpe
2025-06-03T13:37:01Z

On Thu, May 29, 2025 at 04:32:04PM +1000, Alistair Popple wrote:
> Previously dax pages were skipped by the pagewalk code as pud_special() or
> vm_normal_page{_pmd}() would be false for DAX pages. Now that dax pages are
> refcounted normally that is no longer the case, so add explicit checks to
> skip them.
>
> Signed-off-by: Alistair Popple <apopple@nvidia.com>
> ---
> include/linux/memremap.h | 11 +++++++++++
> mm/pagewalk.c | 12 ++++++++++--
> 2 files changed, 21 insertions(+), 2 deletions(-)

But why do we want to skip them?

Like hmm uses pagewalk and it would like to see DAX pages?

I guess it makes sense from the perspective of not changing things,
but it seems like a comment should be left behind explaining that this
is just for legacy reasons until someone audits the callers.

Jason