Change the way how pgd_offset, p4d_offset, pud_offset and pmd_offset
walk the page tables. pgd_offset now always calculates the index for
the top-level page table and adds it to the pgd, this is either a
segment table offset for a 2-level setup, a region-3 offset for 3-levels,
region-2 offset for 4-levels, or a region-1 offset for a 5-level setup.
The other three functions p4d_offset, pud_offset and pmd_offset will
only add the respective offset if they dereference the passed pointer.
With the new way of walking the page tables a sequence like this from
mm/gup.c now works:
pgdp = pgd_offset(current->mm, addr);
pgd = READ_ONCE(*pgdp);
p4dp = p4d_offset(&pgd, addr);
p4d = READ_ONCE(*p4dp);
pudp = pud_offset(&p4d, addr);
pud = READ_ONCE(*pudp);
pmdp = pmd_offset(&pud, addr);
pmd = READ_ONCE(*pmdp);
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
d1874a0c28