linux-kernel - [PATCH v3 1/7] mm: khugepaged: extract vm flag setting outside of hugepage

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Message-ID: <20250519223307.3601786-2-usamaarif642@gmail.com>
Date: Mon, 19 May 2025 23:29:53 +0100
From: Usama Arif <usamaarif642@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	david@...hat.com,
	linux-mm@...ck.org
Cc: hannes@...xchg.org,
	shakeel.butt@...ux.dev,
	riel@...riel.com,
	ziy@...dia.com,
	laoar.shao@...il.com,
	baolin.wang@...ux.alibaba.com,
	lorenzo.stoakes@...cle.com,
	Liam.Howlett@...cle.com,
	npache@...hat.com,
	ryan.roberts@....com,
	vbabka@...e.cz,
	jannh@...gle.com,
	Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	kernel-team@...a.com,
	Usama Arif <usamaarif642@...il.com>
Subject: [PATCH v3 1/7] mm: khugepaged: extract vm flag setting outside of hugepage_madvise

This is so that flag setting can be resused later in other functions,
to reduce code duplication (including the s390 exception).

No functional change intended with this patch.

Signed-off-by: Usama Arif <usamaarif642@...il.com>
---
 include/linux/huge_mm.h |  1 +
 mm/khugepaged.c         | 26 +++++++++++++++++---------
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 2f190c90192d..23580a43787c 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -431,6 +431,7 @@ change_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
 			__split_huge_pud(__vma, __pud, __address);	\
 	}  while (0)
 
+int hugepage_set_vmflags(unsigned long *vm_flags, int advice);
 int hugepage_madvise(struct vm_area_struct *vma, unsigned long *vm_flags,
 		     int advice);
 int madvise_collapse(struct vm_area_struct *vma,
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index b04b6a770afe..ab3427c87422 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -346,8 +346,7 @@ struct attribute_group khugepaged_attr_group = {
 };
 #endif /* CONFIG_SYSFS */
 
-int hugepage_madvise(struct vm_area_struct *vma,
-		     unsigned long *vm_flags, int advice)
+int hugepage_set_vmflags(unsigned long *vm_flags, int advice)
 {
 	switch (advice) {
 	case MADV_HUGEPAGE:
@@ -358,16 +357,10 @@ int hugepage_madvise(struct vm_area_struct *vma,
 		 * ignore the madvise to prevent qemu from causing a SIGSEGV.
 		 */
 		if (mm_has_pgste(vma->vm_mm))
-			return 0;
+			return -EPERM;
 #endif
 		*vm_flags &= ~VM_NOHUGEPAGE;
 		*vm_flags |= VM_HUGEPAGE;
-		/*
-		 * If the vma become good for khugepaged to scan,
-		 * register it here without waiting a page fault that
-		 * may not happen any time soon.
-		 */
-		khugepaged_enter_vma(vma, *vm_flags);
 		break;
 	case MADV_NOHUGEPAGE:
 		*vm_flags &= ~VM_HUGEPAGE;
@@ -383,6 +376,21 @@ int hugepage_madvise(struct vm_area_struct *vma,
 	return 0;
 }
 
+int hugepage_madvise(struct vm_area_struct *vma,
+		     unsigned long *vm_flags, int advice)
+{
+	if (advice == MADV_HUGEPAGE && !hugepage_set_vmflags(vm_flags, advice)) {
+		/*
+		 * If the vma become good for khugepaged to scan,
+		 * register it here without waiting a page fault that
+		 * may not happen any time soon.
+		 */
+		khugepaged_enter_vma(vma, *vm_flags);
+	}
+
+	return 0;
+}
+
 int __init khugepaged_init(void)
 {
 	mm_slot_cache = KMEM_CACHE(khugepaged_mm_slot, 0);
-- 
2.47.1