[PATCH v4 3/7] mm/khugepaged: introduce a count_collapse_event() helper

["Nico Pache (Red Hat)" <nico.pache@linux.dev>]

Provide a simple helper function to help reduce a often used, and
duplicate pattern across the khugepaged code.

When collapsing to a PMD we need to record a vm_event and the mTHP_stat
event. When doing mTHP collapse we only update the mTHP stat.

Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Usama Arif <usama.arif@linux.dev>
Signed-off-by: Nico Pache (Red Hat) <nico.pache@linux.dev>
---
 mm/khugepaged.c | 42 +++++++++++++++++++++---------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 8babd4c97db6..cae510aa2914 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -688,6 +688,14 @@ static inline bool folio_pte_referenced(struct folio *folio,
 	return pte_young(pteval) || mmu_notifier_test_young(vma->vm_mm, addr);
 }
 
+static void count_collapse_event(unsigned int order, enum vm_event_item vm_event,
+		enum mthp_stat_item mthp_event)
+{
+	if (is_pmd_order(order))
+		count_vm_event(vm_event);
+	count_mthp_stat(order, mthp_event);
+}
+
 static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		unsigned long start_addr, pte_t *pte, struct collapse_control *cc,
 		unsigned int order, struct list_head *compound_pagelist)
@@ -708,9 +716,8 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		if (pte_none_or_zero(pteval)) {
 			if (++none_or_zero > max_ptes_none) {
 				result = SCAN_EXCEED_NONE_PTE;
-				if (is_pmd_order(order))
-					count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
-				count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_NONE);
+				count_collapse_event(order, THP_SCAN_EXCEED_NONE_PTE,
+						     MTHP_STAT_COLLAPSE_EXCEED_NONE);
 				goto out;
 			}
 			continue;
@@ -752,9 +759,8 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma,
 			 */
 			if (++shared > max_ptes_shared) {
 				result = SCAN_EXCEED_SHARED_PTE;
-				if (is_pmd_order(order))
-					count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
-				count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
+				count_collapse_event(order, THP_SCAN_EXCEED_SHARED_PTE,
+						     MTHP_STAT_COLLAPSE_EXCEED_SHARED);
 				goto out;
 			}
 		}
@@ -1264,15 +1270,12 @@ static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_stru
 	folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask);
 	if (!folio) {
 		*foliop = NULL;
-		if (is_pmd_order(order))
-			count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
-		count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC_FAILED);
+		count_collapse_event(order, THP_COLLAPSE_ALLOC_FAILED,
+				     MTHP_STAT_COLLAPSE_ALLOC_FAILED);
 		return SCAN_ALLOC_HUGE_PAGE_FAIL;
 	}
 
-	if (is_pmd_order(order))
-		count_vm_event(THP_COLLAPSE_ALLOC);
-	count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC);
+	count_collapse_event(order, THP_COLLAPSE_ALLOC, MTHP_STAT_COLLAPSE_ALLOC);
 
 	if (unlikely(mem_cgroup_charge(folio, mm, gfp))) {
 		folio_put(folio);
@@ -1662,9 +1665,8 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm,
 		if (pte_none_or_zero(pteval)) {
 			if (++none_or_zero > max_ptes_none) {
 				result = SCAN_EXCEED_NONE_PTE;
-				count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
-				count_mthp_stat(HPAGE_PMD_ORDER,
-						MTHP_STAT_COLLAPSE_EXCEED_NONE);
+				count_collapse_event(HPAGE_PMD_ORDER, THP_SCAN_EXCEED_NONE_PTE,
+						     MTHP_STAT_COLLAPSE_EXCEED_NONE);
 				goto out_unmap;
 			}
 			continue;
@@ -1672,9 +1674,8 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm,
 		if (!pte_present(pteval)) {
 			if (++unmapped > max_ptes_swap) {
 				result = SCAN_EXCEED_SWAP_PTE;
-				count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
-				count_mthp_stat(HPAGE_PMD_ORDER,
-						MTHP_STAT_COLLAPSE_EXCEED_SWAP);
+				count_collapse_event(HPAGE_PMD_ORDER, THP_SCAN_EXCEED_SWAP_PTE,
+						     MTHP_STAT_COLLAPSE_EXCEED_SWAP);
 				goto out_unmap;
 			}
 			/*
@@ -1731,9 +1732,8 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm,
 		if (folio_maybe_mapped_shared(folio)) {
 			if (++shared > max_ptes_shared) {
 				result = SCAN_EXCEED_SHARED_PTE;
-				count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
-				count_mthp_stat(HPAGE_PMD_ORDER,
-						MTHP_STAT_COLLAPSE_EXCEED_SHARED);
+				count_collapse_event(HPAGE_PMD_ORDER, THP_SCAN_EXCEED_SHARED_PTE,
+						     MTHP_STAT_COLLAPSE_EXCEED_SHARED);
 				goto out_unmap;
 			}
 		}

-- 
2.55.0