Couldn't we do here
if (!pmd_present(pmdval))
goto nomap;
To replace the original pmd_none() .. check.
A page table must always be present IIRC.
I am not sure about the pmd_none(), a page table may not be present, I've not
audited
the callers. But I think we can do
IIRC page tables must always have the present bit set. So we can just simplify
to the single pmd_present() check.
Not sure about that one, are you happy if we follow it up later with a separate
fix
Taking a look at other page table walkers, they couldn't possibly work if
tables would not be pmd_present().
E.g., walk_pmd_range() in mm/pagewalk.c has
if (walk->vma)
split_huge_pmd(walk->vma, pmd, addr);
else if (pmd_leaf(*pmd) || !pmd_present(*pmd))
continue; /* Nothing to do. */
err = walk_pte_range(pmd, addr, next, walk);
if (err)
break;
If a PTE table would not be pmd_present() we would never ever call
walk_pte_range().
So I am pretty sure that this can just be:
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 567e2d084071e..1916d22aaf1f1 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -290,7 +290,7 @@ pte_t *___pte_offset_map(pmd_t *pmd, unsigned long addr,
pmd_t *pmdvalp)
if (pmdvalp)
*pmdvalp = pmdval;
- if (unlikely(pmd_none(pmdval) || is_pmd_migration_entry(pmdval)))
+ if (unlikely(!pmd_present(pmdval)))
goto nomap;
if (unlikely(pmd_trans_huge(pmdval)))
goto nomap;
Unless I am missing something important :)
--
Cheers
David / dhildenb
