s390/hugetlb: switch to generic version of follow_huge_pud()

When pud-sized hugepages were introduced for s390, the generic version of
follow_huge_pud() was using pte_page() instead of pud_page().  This would
be wrong for s390, see also commit 9753412 ("mm/hugetlb: use
pmd_page() in follow_huge_pmd()").  Therefore, and probably because not
all archs were supporting pud_page() at that time, a private version of
follow_huge_pud() was added for s390, correctly using pud_page().

Since commit 3a194f3 ("mm/hugetlb: make pud_huge() and
follow_huge_pud() aware of non-present pud entry"), the generic version of
follow_huge_pud() is now also using pud_page(), and in general behaves
similar to follow_huge_pmd().

Therefore we can now switch to the generic version and get rid of the
s390-specific follow_huge_pud().

Link: https://lkml.kernel.org/r/20220818135717.609eef8a@thinkpad
Signed-off-by: Gerald Schaefer <[email protected]>
Cc: Haiyue Wang <[email protected]>
Cc: Miaohe Lin <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Muchun Song <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

arch/s390/mm/hugetlbpage.c

@@ -237,16 +237,6 @@ int pud_huge(pud_t pud)
 	return pud_large(pud);
 }
 
-struct page *
-follow_huge_pud(struct mm_struct *mm, unsigned long address,
-		pud_t *pud, int flags)
-{
-	if (flags & FOLL_GET)
-		return NULL;
-
-	return pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
-}
-
 bool __init arch_hugetlb_valid_size(unsigned long size)
 {
 	if (MACHINE_HAS_EDAT1 && size == PMD_SIZE)