[PATCH v2 11/32] mm/vmwgfx: simplify pmd & pud mapping dirty helpers

Hugh Dickins
2023-06-09T01:20:12Z

wp_clean_pmd_entry() need not check pmd_trans_unstable() or pmd_none(),
wp_clean_pud_entry() need not check pud_trans_unstable() or pud_none():
it's just the ACTION_CONTINUE when trans_huge or devmap that's needed
to prevent splitting, and we're hoping to remove pmd_trans_unstable().
Is that PUD #ifdef necessary? Maybe some configs are missing a stub.

Signed-off-by: Hugh Dickins <hughd@google.com>
---
mm/mapping_dirty_helpers.c | 34 +++++++++-------------------------
1 file changed, 9 insertions(+), 25 deletions(-)

diff --git a/mm/mapping_dirty_helpers.c b/mm/mapping_dirty_helpers.c
index e1eb33f49059..87b4beeda4fa 100644
--- a/mm/mapping_dirty_helpers.c
+++ b/mm/mapping_dirty_helpers.c
@@ -128,19 +128,11 @@ static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,
{
pmd_t pmdval = pmdp_get_lockless(pmd);

- if (!pmd_trans_unstable(&pmdval))
- return 0;
-
- if (pmd_none(pmdval)) {
- walk->action = ACTION_AGAIN;
- return 0;
- }
-
- /* Huge pmd, present or migrated */
- walk->action = ACTION_CONTINUE;
- if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval))
+ /* Do not split a huge pmd, present or migrated */
+ if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval)) {
WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval));
-
+ walk->action = ACTION_CONTINUE;
+ }
return 0;
}

@@ -156,23 +148,15 @@ static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,
static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
pud_t pudval = READ_ONCE(*pud);

- if (!pud_trans_unstable(&pudval))
- return 0;
-
- if (pud_none(pudval)) {
- walk->action = ACTION_AGAIN;
- return 0;
- }
-
-#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
- /* Huge pud */
- walk->action = ACTION_CONTINUE;
- if (pud_trans_huge(pudval) || pud_devmap(pudval))
+ /* Do not split a huge pud */
+ if (pud_trans_huge(pudval) || pud_devmap(pudval)) {
WARN_ON(pud_write(pudval) || pud_dirty(pudval));
+ walk->action = ACTION_CONTINUE;
+ }
#endif
-
return 0;
}

--
2.35.3