[RFC Patch 06/11] mm/huge_memory: introduce __split_folio_and_update_stats() to consolidate split task

[Wei Yang <richard.weiyang@gmail.com>]

The folio splitting process involves several related tasks that are
executed together:

    Adjusting memcg (memory control group) accounting.
    Updating page owner tracking.
    Splitting the folio to the target size (new_order).
    Updating necessary folio statistics.

This commit introduces the new helper function,
__split_folio_and_update_stats(), to gather all these tasks. This
consolidation improves modularity and is a necessary preparation step
for further cleanup and simplification of the surrounding folio
splitting logic.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: "David Hildenbrand (Red Hat)" <david@kernel.org>

---
v2:
  * add const to nr_new_folios
  * remove is_anon parameter
---
 mm/huge_memory.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 37a73bfb96ff..7160254ce76c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3571,6 +3571,22 @@ static void __split_folio_to_order(struct folio *folio, int old_order,
 		ClearPageCompound(&folio->page);
 }
 
+static void __split_folio_and_update_stats(struct folio *folio, int old_order,
+					   int new_order)
+{
+	const int nr_new_folios = 1UL << (old_order - new_order);
+
+	folio_split_memcg_refs(folio, old_order, new_order);
+	split_page_owner(&folio->page, old_order, new_order);
+	pgalloc_tag_split(folio, old_order, new_order);
+	__split_folio_to_order(folio, old_order, new_order);
+
+	if (folio_test_anon(folio)) {
+		mod_mthp_stat(old_order, MTHP_STAT_NR_ANON, -1);
+		mod_mthp_stat(new_order, MTHP_STAT_NR_ANON, nr_new_folios);
+	}
+}
+
 /**
  * __split_unmapped_folio() - splits an unmapped @folio to lower order folios in
  * two ways: uniform split or non-uniform split.
@@ -3628,8 +3644,6 @@ static int __split_unmapped_folio(struct folio *folio, int new_order,
 	for (split_order = start_order;
 	     split_order >= new_order;
 	     split_order--) {
-		int nr_new_folios = 1UL << (old_order - split_order);
-
 		/* order-1 anonymous folio is not supported */
 		if (is_anon && split_order == 1)
 			continue;
@@ -3650,15 +3664,7 @@ static int __split_unmapped_folio(struct folio *folio, int new_order,
 			}
 		}
 
-		folio_split_memcg_refs(folio, old_order, split_order);
-		split_page_owner(&folio->page, old_order, split_order);
-		pgalloc_tag_split(folio, old_order, split_order);
-		__split_folio_to_order(folio, old_order, split_order);
-
-		if (is_anon) {
-			mod_mthp_stat(old_order, MTHP_STAT_NR_ANON, -1);
-			mod_mthp_stat(split_order, MTHP_STAT_NR_ANON, nr_new_folios);
-		}
+		__split_folio_and_update_stats(folio, old_order, split_order);
 		/*
 		 * If uniform split, the process is complete.
 		 * If non-uniform, continue splitting the folio at @split_at
-- 
2.34.1