[PATCH 2/2] mm: madvise: make MADV_NOHUGEPAGE a no-op if !THP

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

From: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@kuka.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@infradead.org>
Signed-off-by: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@kuka.com>
Reviewed-by: Yang Shi <yang@os.amperecomputing.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.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