+ mm-khugepaged-refactor-per-scan-state-clearing-into-collapse_control_init_scan.patch added to mm-new branch

The patch titled
     Subject: mm/khugepaged: refactor per-scan state clearing into collapse_control_init_scan()
has been added to the -mm mm-new branch.  Its filename is
     mm-khugepaged-refactor-per-scan-state-clearing-into-collapse_control_init_scan.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-refactor-per-scan-state-clearing-into-collapse_control_init_scan.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: "Nico Pache (Red Hat)" <[email protected]>
Subject: mm/khugepaged: refactor per-scan state clearing into collapse_control_init_scan()
Date: Tue, 04 Aug 2026 13:24:59 -0600

Patch series "mm/khugepaged: several cleanups", v3.

The following changes stem from a number of reviews during my khugepaged
mTHP support series [1]. Some of these are minor code cleanups, issues or
reviews that we decided to deferred to a followup series, or in the case
of the more major patch of the series, changes [2] Lance Yang attempted
while my series was in-flight and we decided to wait till later to try.

The first 3 patches introduce helper functions to increase code reuse and
readability. This includes a per-scan state clearing function, extracting
the young page check into a helper, and a count_collapse_event() function
to reduce a repetative pattern used across mTHP collapse.

The 4th patch was the byproduct of me throwing Claude at all the
comments in khugepaged verifying and looking for any outdated info.

The 5th patch is based on Lance Yang's commit series [2] trying to extract
the PTE state checking into a helper function. This required a bit of
rewriting due to differences after mTHP collapse was introduced. I also
took into account the changes requested during his patches review cycle.

The remaining 2 patches were review points during my mTHP series that we
agreed can be deferred to a later series.


This patch (of 7):

Extract the repeated clearing of node_load, alloc_nmask, and
mthp_present_ptes into a helper to reduce duplication in
collapse_scan_pmd() and collapse_scan_file().  Althought file scans do not
current use the bitmap, they will in the future, and clearing it now is
harmless.

Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/all/[email protected]/ [1]
Link: https://lore.kernel.org/all/[email protected]/ [2]
Signed-off-by: Nico Pache (Red Hat) <[email protected]>
Reviewed-by: Baolin Wang <[email protected]>
Acked-by: Usama Arif <[email protected]>
Acked-by: David Hildenbrand (Arm) <[email protected]>
Reviewed-by: Lorenzo Stoakes (ARM) <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Barry Song <[email protected]>
Cc: Dev Jain <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Lance Yang <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/khugepaged.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

--- a/mm/khugepaged.c~mm-khugepaged-refactor-per-scan-state-clearing-into-collapse_control_init_scan
+++ a/mm/khugepaged.c
@@ -629,6 +629,13 @@ void __khugepaged_exit(struct mm_struct
 	}
 }
 
+static void collapse_control_init_scan(struct collapse_control *cc)
+{
+	memset(cc->node_load, 0, sizeof(cc->node_load));
+	nodes_clear(cc->alloc_nmask);
+	bitmap_zero(cc->mthp_present_ptes, MAX_PTRS_PER_PTE);
+}
+
 static void release_pte_folio(struct folio *folio)
 {
 	node_stat_mod_folio(folio,
@@ -1617,9 +1624,7 @@ static enum scan_result collapse_scan_pm
 		goto out;
 	}
 
-	bitmap_zero(cc->mthp_present_ptes, MAX_PTRS_PER_PTE);
-	memset(cc->node_load, 0, sizeof(cc->node_load));
-	nodes_clear(cc->alloc_nmask);
+	collapse_control_init_scan(cc);
 
 	enabled_orders = collapse_possible_orders(vma, vma->vm_flags, tva_flags);
 
@@ -2691,8 +2696,7 @@ static enum scan_result collapse_scan_fi
 
 	present = 0;
 	swap = 0;
-	memset(cc->node_load, 0, sizeof(cc->node_load));
-	nodes_clear(cc->alloc_nmask);
+	collapse_control_init_scan(cc);
 	rcu_read_lock();
 	xas_for_each(&xas, folio, start + HPAGE_PMD_NR - 1) {
 		if (xas_retry(&xas, folio))
_

Patches currently in -mm which might be from [email protected] are

mm-khugepaged-refactor-per-scan-state-clearing-into-collapse_control_init_scan.patch
mm-khugepaged-extract-young-page-check-into-pte_is_referenced-helper.patch
mm-khugepaged-introduce-a-count_collapse_event-helper.patch
mm-khugepaged-fix-outdated-comments.patch
mm-khugepaged-refactor-the-pte-state-checks-into-a-helper.patch
mm-khugepaged-unmap-pte-before-releasing-vma-write-lock.patch
mm-documentation-clarify-where-the-mthp-stats-live.patch