[PATCH 4/5] mm/rmap: refactor anon swapbacked folio unmap in try_to_unmap_one

[Dev Jain <dev.jain@arm.com>]

Refactor anonymous swapbacked folio unmap to ttu_anon_swapbacked_folio().

No functional change intended.

Signed-off-by: Dev Jain <dev.jain@arm.com>
---
 mm/rmap.c | 105 ++++++++++++++++++++++++++++++++----------------------
 1 file changed, 62 insertions(+), 43 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 00b571c2a1bab..ade78df5be2bd 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -2113,6 +2113,64 @@ static inline bool ttu_anon_lazyfree_folio(struct vm_area_struct *vma,
 	return true;
 }
 
+static inline void set_swp_pte_at(struct mm_struct *mm, unsigned long address,
+		pte_t *ptep, swp_entry_t entry, pte_t pteval, bool anon_exclusive)
+{
+	pte_t swp_pte = swp_entry_to_pte(entry);
+
+	if (anon_exclusive)
+		swp_pte = pte_swp_mkexclusive(swp_pte);
+
+	if (likely(pte_present(pteval))) {
+		if (pte_soft_dirty(pteval))
+			swp_pte = pte_swp_mksoft_dirty(swp_pte);
+		if (pte_uffd_wp(pteval))
+			swp_pte = pte_swp_mkuffd_wp(swp_pte);
+	} else {
+		/* Device-exclusive entry */
+		if (pte_swp_soft_dirty(pteval))
+			swp_pte = pte_swp_mksoft_dirty(swp_pte);
+		if (pte_swp_uffd_wp(pteval))
+			swp_pte = pte_swp_mkuffd_wp(swp_pte);
+	}
+
+	set_pte_at(mm, address, ptep, swp_pte);
+}
+
+static inline bool ttu_anon_swapbacked_folio(struct vm_area_struct *vma, struct folio *folio,
+		struct page *subpage, unsigned long address, pte_t *ptep,
+		pte_t pteval)
+{
+	bool anon_exclusive = folio_test_anon(folio) && PageAnonExclusive(subpage);
+	swp_entry_t entry = page_swap_entry(subpage);
+	struct mm_struct *mm = vma->vm_mm;
+
+	if (folio_dup_swap(folio, subpage) < 0)
+		return false;
+
+	/*
+	 * arch_unmap_one() is expected to be a NOP on
+	 * architectures where we could have PFN swap PTEs,
+	 * so we'll not check/care.
+	 */
+	if (arch_unmap_one(mm, vma, address, pteval) < 0) {
+		folio_put_swap(folio, subpage);
+		return false;
+	}
+
+	/* See folio_try_share_anon_rmap(): clear PTE first. */
+	if (anon_exclusive && folio_try_share_anon_rmap_pte(folio, subpage)) {
+		folio_put_swap(folio, subpage);
+		return false;
+	}
+
+	mm_prepare_for_swap_entries(mm);
+	dec_mm_counter(mm, MM_ANONPAGES);
+	inc_mm_counter(mm, MM_SWAPENTS);
+	set_swp_pte_at(mm, address, ptep, entry, pteval, anon_exclusive);
+	return true;
+}
+
 /*
  * @arg: enum ttu_flags will be passed to this argument
  */
@@ -2121,7 +2179,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 {
 	struct mm_struct *mm = vma->vm_mm;
 	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
-	bool anon_exclusive, ret = true;
+	bool ret = true;
 	pte_t pteval;
 	struct page *subpage;
 	struct mmu_notifier_range range;
@@ -2235,8 +2293,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 		}
 
 		subpage = folio_page(folio, pfn - folio_pfn(folio));
-		anon_exclusive = folio_test_anon(folio) &&
-				 PageAnonExclusive(subpage);
 
 		if (likely(pte_present(pteval))) {
 			nr_pages = folio_unmap_pte_batch(folio, &pvmw, flags, pteval);
@@ -2295,8 +2351,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 			 */
 			dec_mm_counter(mm, mm_counter(folio));
 		} else if (folio_test_anon(folio)) {
-			swp_entry_t entry = page_swap_entry(subpage);
-			pte_t swp_pte;
 			/*
 			 * Store the swap location in the pte.
 			 * See handle_pte_fault() ...
@@ -2317,47 +2371,12 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 				goto finish_unmap;
 			}
 
-			if (folio_dup_swap(folio, subpage) < 0) {
-				set_pte_at(mm, address, pvmw.pte, pteval);
-				goto walk_abort;
-			}
-
-			/*
-			 * arch_unmap_one() is expected to be a NOP on
-			 * architectures where we could have PFN swap PTEs,
-			 * so we'll not check/care.
-			 */
-			if (arch_unmap_one(mm, vma, address, pteval) < 0) {
-				folio_put_swap(folio, subpage);
-				set_pte_at(mm, address, pvmw.pte, pteval);
-				goto walk_abort;
-			}
-
-			/* See folio_try_share_anon_rmap(): clear PTE first. */
-			if (anon_exclusive &&
-			    folio_try_share_anon_rmap_pte(folio, subpage)) {
-				folio_put_swap(folio, subpage);
+			if (!ttu_anon_swapbacked_folio(vma, folio, subpage, address,
+						pvmw.pte, pteval)) {
 				set_pte_at(mm, address, pvmw.pte, pteval);
 				goto walk_abort;
 			}
-			mm_prepare_for_swap_entries(mm);
-			dec_mm_counter(mm, MM_ANONPAGES);
-			inc_mm_counter(mm, MM_SWAPENTS);
-			swp_pte = swp_entry_to_pte(entry);
-			if (anon_exclusive)
-				swp_pte = pte_swp_mkexclusive(swp_pte);
-			if (likely(pte_present(pteval))) {
-				if (pte_soft_dirty(pteval))
-					swp_pte = pte_swp_mksoft_dirty(swp_pte);
-				if (pte_uffd_wp(pteval))
-					swp_pte = pte_swp_mkuffd_wp(swp_pte);
-			} else {
-				if (pte_swp_soft_dirty(pteval))
-					swp_pte = pte_swp_mksoft_dirty(swp_pte);
-				if (pte_swp_uffd_wp(pteval))
-					swp_pte = pte_swp_mkuffd_wp(swp_pte);
-			}
-			set_pte_at(mm, address, pvmw.pte, swp_pte);
+			goto finish_unmap;
 		} else {
 			/*
 			 * This is a locked file-backed folio,
-- 
2.43.0