[PATCH v2] mm: huge_memory: add the missing folio_test_pmd_mappable() for THP split statistics

[Baolin Wang]

Now the mTHP can also be split or added into the deferred list, so add
folio_test_pmd_mappable() validation for PMD mapped THP, to avoid confusion
with PMD mapped THP related statistics.

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
---
Changes from v1:
 - Add acked tag from David.
 - Check the THP earlier in case the folio is split per Lance.
---
 mm/huge_memory.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 716d29c21b6e..a9789ca823bc 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2994,6 +2994,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
 	XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order);
 	struct anon_vma *anon_vma = NULL;
 	struct address_space *mapping = NULL;
+	bool is_thp = folio_test_pmd_mappable(folio);
 	int extra_pins, ret;
 	pgoff_t end;
 	bool is_hzp;
@@ -3172,7 +3173,8 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
 		i_mmap_unlock_read(mapping);
 out:
 	xas_destroy(&xas);
-	count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
+	if (is_thp)
+		count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
 	return ret;
 }
 
@@ -3234,7 +3236,8 @@ void deferred_split_folio(struct folio *folio)
 
 	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
 	if (list_empty(&folio->_deferred_list)) {
-		count_vm_event(THP_DEFERRED_SPLIT_PAGE);
+		if (folio_test_pmd_mappable(folio))
+			count_vm_event(THP_DEFERRED_SPLIT_PAGE);
 		list_add_tail(&folio->_deferred_list, &ds_queue->split_queue);
 		ds_queue->split_queue_len++;
 #ifdef CONFIG_MEMCG
-- 
2.39.3