linux-kernel - [PATCH 2/2] mm: madvise: make MADV

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Message-ID: <3f99d6bc8cd1e78532077adf8b26e973d325188f.1747338438.git.lorenzo.stoakes@oracle.com>
Date: Thu, 15 May 2025 21:15:46 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: James Houghton <jthoughton@...gle.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>,
        Yang Shi <yang@...amperecomputing.com>,
        David Hildenbrand <david@...hat.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, pbonzini@...hat.com,
        kvm@...r.kernel.org, linux-s390@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] mm: madvise: make MADV_NOHUGEPAGE a no-op if !THP

From: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>

VM_NOHUGEPAGE is a no-op if CONFIG_TRANSPARENT_HUGEPAGE is disabled. So
it makes no sense to return an error when calling madvise() with
MADV_NOHUGEPAGE in that case.

Suggested-by: Matthew Wilcox <willy@...radead.org>
Signed-off-by: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>
Reviewed-by: Yang Shi <yang@...amperecomputing.com>
Acked-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 include/linux/huge_mm.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 2f190c90192d..1a8082c61e01 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -506,6 +506,8 @@ bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr,
 
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 
+#include <uapi/asm/mman.h>
+
 static inline bool folio_test_pmd_mappable(struct folio *folio)
 {
 	return false;
@@ -595,6 +597,9 @@ static inline bool unmap_huge_pmd_locked(struct vm_area_struct *vma,
 static inline int hugepage_madvise(struct vm_area_struct *vma,
 				   unsigned long *vm_flags, int advice)
 {
+	/* On a !THP kernel, MADV_NOHUGEPAGE is a no-op, but MADV_HUGEPAGE is not supported */
+	if (advice == MADV_NOHUGEPAGE)
+		return 0;
 	return -EINVAL;
 }
 
-- 
2.49.0