+ mm-khugepaged-change-collapse_pte_mapped_thp-to-return-void.patch added to mm-new branch

+ mm-khugepaged-change-collapse_pte_mapped_thp-to-return-void.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/khugepaged: change collapse_pte_mapped_thp() to return void
has been added to the -mm mm-new branch.  Its filename is
     mm-khugepaged-change-collapse_pte_mapped_thp-to-return-void.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-change-collapse_pte_mapped_thp-to-return-void.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
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fixup patches in mm-new.

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------------------------------------------------------
From: Shivank Garg <shivankg@amd.com>
Subject: mm/khugepaged: change collapse_pte_mapped_thp() to return void
Date: Wed, 24 Dec 2025 11:13:55 +0000

The only external caller of collapse_pte_mapped_thp() is uprobe, which
ignores the return value.  Change the external API to return void to
simplify the interface.

Introduce try_collapse_pte_mapped_thp() for internal use that preserves
the return value.  This prepares for future patch that will convert the
return type to use enum scan_result.

Link: https://lkml.kernel.org/r/20251224111351.41042-10-shivankg@amd.com
Signed-off-by: Shivank Garg <shivankg@amd.com>
Suggested-by: David Hildenbrand (Red Hat) <david@kernel.org>
Acked-by: Lance Yang <lance.yang@linux.dev>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/khugepaged.h |    9 +++----
 mm/khugepaged.c            |   40 ++++++++++++++++++++---------------
 2 files changed, 27 insertions(+), 22 deletions(-)

--- a/include/linux/khugepaged.h~mm-khugepaged-change-collapse_pte_mapped_thp-to-return-void
+++ a/include/linux/khugepaged.h
@@ -17,8 +17,8 @@ extern void khugepaged_enter_vma(struct
 				 vm_flags_t vm_flags);
 extern void khugepaged_min_free_kbytes_update(void);
 extern bool current_is_khugepaged(void);
-extern int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
-				   bool install_pmd);
+extern void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
+				    bool install_pmd);
 
 static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 {
@@ -42,10 +42,9 @@ static inline void khugepaged_enter_vma(
 					vm_flags_t vm_flags)
 {
 }
-static inline int collapse_pte_mapped_thp(struct mm_struct *mm,
-					  unsigned long addr, bool install_pmd)
+static inline void collapse_pte_mapped_thp(struct mm_struct *mm,
+					   unsigned long addr, bool install_pmd)
 {
-	return 0;
 }
 
 static inline void khugepaged_min_free_kbytes_update(void)
--- a/mm/khugepaged.c~mm-khugepaged-change-collapse_pte_mapped_thp-to-return-void
+++ a/mm/khugepaged.c
@@ -1477,20 +1477,8 @@ static int set_huge_pmd(struct vm_area_s
 	return SCAN_SUCCEED;
 }
 
-/**
- * collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at
- * address haddr.
- *
- * @mm: process address space where collapse happens
- * @addr: THP collapse address
- * @install_pmd: If a huge PMD should be installed
- *
- * This function checks whether all the PTEs in the PMD are pointing to the
- * right THP. If so, retract the page table so the THP can refault in with
- * as pmd-mapped. Possibly install a huge PMD mapping the THP.
- */
-int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
-			    bool install_pmd)
+static int try_collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
+				       bool install_pmd)
 {
 	int nr_mapped_ptes = 0, result = SCAN_FAIL;
 	unsigned int nr_batch_ptes;
@@ -1711,6 +1699,24 @@ drop_folio:
 	return result;
 }
 
+/**
+ * collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at
+ * address haddr.
+ *
+ * @mm: process address space where collapse happens
+ * @addr: THP collapse address
+ * @install_pmd: If a huge PMD should be installed
+ *
+ * This function checks whether all the PTEs in the PMD are pointing to the
+ * right THP. If so, retract the page table so the THP can refault in with
+ * as pmd-mapped. Possibly install a huge PMD mapping the THP.
+ */
+void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
+			     bool install_pmd)
+{
+	try_collapse_pte_mapped_thp(mm, addr, install_pmd);
+}
+
 /* Can we retract page tables for this file-backed VMA? */
 static bool file_backed_vma_is_retractable(struct vm_area_struct *vma)
 {
@@ -2227,7 +2233,7 @@ immap_locked:
 
 	/*
 	 * Remove pte page tables, so we can re-fault the page as huge.
-	 * If MADV_COLLAPSE, adjust result to call collapse_pte_mapped_thp().
+	 * If MADV_COLLAPSE, adjust result to call try_collapse_pte_mapped_thp().
 	 */
 	retract_page_tables(mapping, start);
 	if (cc && !cc->is_khugepaged)
@@ -2480,7 +2486,7 @@ static unsigned int khugepaged_scan_mm_s
 					mmap_read_lock(mm);
 					if (hpage_collapse_test_exit_or_disable(mm))
 						goto breakouterloop;
-					*result = collapse_pte_mapped_thp(mm,
+					*result = try_collapse_pte_mapped_thp(mm,
 						khugepaged_scan.address, false);
 					if (*result == SCAN_PMD_MAPPED)
 						*result = SCAN_SUCCEED;
@@ -2870,7 +2876,7 @@ handle_result:
 		case SCAN_PTE_MAPPED_HUGEPAGE:
 			BUG_ON(mmap_locked);
 			mmap_read_lock(mm);
-			result = collapse_pte_mapped_thp(mm, addr, true);
+			result = try_collapse_pte_mapped_thp(mm, addr, true);
 			mmap_read_unlock(mm);
 			goto handle_result;
 		/* Whitelisted set of results where continuing OK */
_

Patches currently in -mm which might be from shivankg@amd.com are

mm-khugepaged-map-dirty-writeback-pages-failures-to-eagain.patch
mm-khugepaged-retry-with-sync-writeback-for-madv_collapse.patch
mm-khugepaged-remove-unnecessary-goto-skip-label.patch
mm-khugepaged-count-small-vmas-towards-scan-limit.patch
mm-khugepaged-count-small-vmas-towards-scan-limit-fix.patch
mm-khugepaged-change-collapse_pte_mapped_thp-to-return-void.patch
mm-khugepaged-use-enum-scan_result-for-result-variables-and-return-types.patch
mm-khugepaged-make-khugepaged_collapse_control-static.patch