On Wed, Mar 06, 2024 at 06:41:35PM +0800, peterx@xxxxxxxxxx wrote:
> From: Peter Xu <peterx@xxxxxxxxxx>
>
> Swap pud entries do not always return true for pud_huge() for all archs.
> x86 and sparc (so far) allow it, but all the rest do not accept a swap
> entry to be reported as pud_huge(). So it's not safe to check swap entries
> within pud_huge(). Check swap entries before pud_huge(), so it should be
> always safe.
>
> This is the only place in the kernel that (IMHO, wrongly) relies on
> pud_huge() to return true on pud swap entries. The plan is to cleanup
> pXd_huge() to only report non-swap mappings for all archs.
>
> Cc: Alistair Popple <apopple@xxxxxxxxxx>
> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
> ---
> mm/hmm.c | 7 +------
> 1 file changed, 1 insertion(+), 6 deletions(-)
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> @@ -424,7 +424,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
> walk->action = ACTION_CONTINUE;
>
> pud = READ_ONCE(*pudp);
> - if (pud_none(pud)) {
> + if (pud_none(pud) || !pud_present(pud)) {
Isn't this a tautology? pud_none always implies !present() ?
Jason
