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

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Message-Id: <20250508-madvise-nohugepage-noop-without-thp-v1-1-e7ceffb197f3@kuka.com>
Date: Thu, 08 May 2025 12:20:27 +0200
From: Ignacio Moreno Gonzalez via B4 Relay <devnull+Ignacio.MorenoGonzalez.kuka.com@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>, 
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
 "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: yang@...amperecomputing.com, willy@...radead.org, linux-mm@...ck.org, 
 linux-kernel@...r.kernel.org, 
 Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>
Subject: [PATCH] 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>
---
https://lore.kernel.org/linux-mm/20250502-map-map_stack-to-vm_nohugepage-only-if-thp-is-enabled-v1-1-113cc634cd51@kuka.com

Here it is presented as a separate thread to avoid mixing stable and
non-stable patches.

This change makes calling madvise(addr, size, MADV_NOHUGEPAGE) on !THP
kernels to return 0 instead of -EINVAL.
---
 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 e893d546a49f464f7586db639fe216231f03651a..5fca742dc5ba784ffccea055b07247707d16cc67 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -509,6 +509,8 @@ 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;
@@ -598,6 +600,9 @@ 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_NOHUGEPAGE is not supported */
+	if (advice == MADV_NOHUGEPAGE)
+		return 0;
 	return -EINVAL;
 }

---
base-commit: fc96b232f8e7c0a6c282f47726b2ff6a5fb341d2
change-id: 20250508-madvise-nohugepage-noop-without-thp-e0721b973d82

Best regards,
-- 
Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>