mm/khugepaged: introduce a count_collapse_event() helper

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.

Link: https://lore.kernel.org/20260811-khugepaged_pte_refactor-v4-3-ddac39d61c4a@linux.dev
Signed-off-by: Nico Pache (Red Hat) <nico.pache@linux.dev>
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>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 21 insertions, 21 deletions

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index c3b3ef5c57b4..6521d2baa058 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -682,6 +682,14 @@ 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)
@@ -702,9 +710,8 @@ 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;
@@ -746,9 +753,8 @@ 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;
 			}
 		}
@@ -1258,15 +1264,12 @@ 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);
@@ -1656,9 +1659,8 @@ 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;
@@ -1666,9 +1668,8 @@ 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;
 			}
 			/*
@@ -1725,9 +1726,8 @@ 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;
 			}
 		}