[PATCH] mm: introduce pmd|pte_need_soft_dirty_wp helpers for softdirty write-protect

[Barry Song]

From: Barry Song <v-songbaohua@xxxxxxxx>

This patch introduces the pte_need_soft_dirty_wp and
pmd_need_soft_dirty_wp helpers to determine if write protection is
required for softdirty tracking. This can enhance code readability
and improve its overall appearance.

These new helpers are utilized in gup, huge_memory, and protect,
and are particularly applied in do_swap_page() to optimize a
softdirty scenario where mkwrite can still be performed.

Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
---
 -v1:
 this is suggested by David here:
 https://lore.kernel.org/linux-mm/baf84b51-7e8a-4da8-9662-3f5cf14ad6f6@xxxxxxxxxx/
 thanks!

 mm/gup.c         |  4 ++--
 mm/huge_memory.c |  2 +-
 mm/internal.h    | 10 ++++++++++
 mm/memory.c      |  2 +-
 mm/mprotect.c    |  2 +-
 5 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 83e279731d1b..756d5416df9c 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -820,7 +820,7 @@ static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
 		return false;
 
 	/* ... and a write-fault isn't required for other reasons. */
-	if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
+	if (pmd_need_soft_dirty_wp(vma, pmd))
 		return false;
 	return !userfaultfd_huge_pmd_wp(vma, pmd);
 }
@@ -941,7 +941,7 @@ static inline bool can_follow_write_pte(pte_t pte, struct page *page,
 		return false;
 
 	/* ... and a write-fault isn't required for other reasons. */
-	if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte))
+	if (pte_need_soft_dirty_wp(vma, pte))
 		return false;
 	return !userfaultfd_pte_wp(vma, pte);
 }
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 3fbcd77f5957..8fbb62f6e491 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1625,7 +1625,7 @@ static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
 		return false;
 
 	/* Do we need write faults for softdirty tracking? */
-	if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
+	if (pmd_need_soft_dirty_wp(vma, pmd))
 		return false;
 
 	/* Do we need write faults for uffd-wp tracking? */
diff --git a/mm/internal.h b/mm/internal.h
index 12e95fdf61e9..51551626da68 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1348,6 +1348,16 @@ static inline bool vma_soft_dirty_enabled(struct vm_area_struct *vma)
 	return !(vma->vm_flags & VM_SOFTDIRTY);
 }
 
+static inline bool pmd_need_soft_dirty_wp(struct vm_area_struct *vma, pmd_t pmd)
+{
+	return vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd);
+}
+
+static inline bool pte_need_soft_dirty_wp(struct vm_area_struct *vma, pte_t pte)
+{
+	return vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte);
+}
+
 static inline void vma_iter_config(struct vma_iterator *vmi,
 		unsigned long index, unsigned long last)
 {
diff --git a/mm/memory.c b/mm/memory.c
index db9130488231..6307c43796aa 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4322,7 +4322,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	if (!folio_test_ksm(folio) &&
 	    (exclusive || folio_ref_count(folio) == 1)) {
 		if ((vma->vm_flags & VM_WRITE) && !userfaultfd_pte_wp(vma, pte) &&
-		    !vma_soft_dirty_enabled(vma)) {
+		    !pte_need_soft_dirty_wp(vma, pte)) {
 			pte = pte_mkwrite(pte, vma);
 			if (vmf->flags & FAULT_FLAG_WRITE) {
 				pte = pte_mkdirty(pte);
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 888ef66468db..5aea9ad11ae1 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -53,7 +53,7 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr,
 		return false;
 
 	/* Do we need write faults for softdirty tracking? */
-	if (vma_soft_dirty_enabled(vma) && !pte_soft_dirty(pte))
+	if (pte_need_soft_dirty_wp(vma, pte))
 		return false;
 
 	/* Do we need write faults for uffd-wp tracking? */
-- 
2.34.1