+ mm-huge_memory-optimize-and-simplify-folio-stat-update-after-split.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/huge_memory: Optimize and simplify folio stat update after split
has been added to the -mm mm-new branch.  Its filename is
     mm-huge_memory-optimize-and-simplify-folio-stat-update-after-split.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-huge_memory-optimize-and-simplify-folio-stat-update-after-split.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: Wei Yang <richard.weiyang@gmail.com>
Subject: mm/huge_memory: Optimize and simplify folio stat update after split
Date: Tue, 14 Oct 2025 13:46:04 +0000

The loop executed after a successful folio split currently has two
combined responsibilities:

  * updating statistics for the new folios
  * determining the folio for the next split iteration.

This commit refactors the logic to directly calculate and update folio
statistics, eliminating the need for the iteration step.

We can do this because all necessary information is already available:

  * All resulting new folios have the same order, which is @split_order.
  * The exact number of new folios can be calculated directly using
    @old_order and @split_order.
  * The folio for the subsequent split is simply the one containing
    @split_at.

By leveraging this knowledge, we can achieve the stat update more cleanly
and efficiently without the looping logic.

Link: https://lkml.kernel.org/r/20251014134606.22543-4-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/huge_memory.c |   18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

--- a/mm/huge_memory.c~mm-huge_memory-optimize-and-simplify-folio-stat-update-after-split
+++ a/mm/huge_memory.c
@@ -3530,7 +3530,6 @@ static int __split_unmapped_folio(struct
 	bool is_anon = folio_test_anon(folio);
 	int order = folio_order(folio);
 	int start_order = uniform_split ? new_order : order - 1;
-	struct folio *next;
 	int split_order;
 
 	folio_clear_has_hwpoisoned(folio);
@@ -3542,9 +3541,8 @@ static int __split_unmapped_folio(struct
 	for (split_order = start_order;
 	     split_order >= new_order;
 	     split_order--) {
-		struct folio *end_folio = folio_next(folio);
 		int old_order = folio_order(folio);
-		struct folio *new_folio;
+		int new_folios = 1UL << (old_order - split_order);
 
 		/* order-1 anonymous folio is not supported */
 		if (is_anon && split_order == 1)
@@ -3573,19 +3571,11 @@ static int __split_unmapped_folio(struct
 		pgalloc_tag_split(folio, old_order, split_order);
 		__split_folio_to_order(folio, old_order, split_order);
 
-		if (is_anon)
+		if (is_anon) {
 			mod_mthp_stat(old_order, MTHP_STAT_NR_ANON, -1);
-		/*
-		 * Iterate through after-split folios and update folio stats.
-		 */
-		for (new_folio = folio; new_folio != end_folio; new_folio = next) {
-			next = folio_next(new_folio);
-			if (new_folio == page_folio(split_at))
-				folio = new_folio;
-			if (is_anon)
-				mod_mthp_stat(folio_order(new_folio),
-					      MTHP_STAT_NR_ANON, 1);
+			mod_mthp_stat(split_order, MTHP_STAT_NR_ANON, new_folios);
 		}
+		folio = page_folio(split_at);
 	}
 
 	return 0;
_

Patches currently in -mm which might be from richard.weiyang@gmail.com are

mm-compaction-check-the-range-to-pageblock_pfn_to_page-is-within-the-zone-first.patch
mm-compaction-fix-the-range-to-pageblock_pfn_to_page.patch
mm-huge_memory-add-pmd-folio-to-ds_queue-in-do_huge_zero_wp_pmd.patch
mm-khugepaged-unify-pmd-folio-installation-with-map_anon_folio_pmd.patch
mm-huge_memory-only-get-folio_order-once-during-__folio_split.patch
mm-huge_memory-cache-folio-attribute-in-__split_unmapped_folio.patch
mm-huge_memory-update-folio-stat-after-successful-split.patch
mm-huge_memory-optimize-and-simplify-folio-stat-update-after-split.patch
mm-huge_memory-optimize-old_order-derivation-during-folio-splitting.patch
mm-huge_memory-remove-redundant-split_order-=-new_order-check-in-uniform_split.patch