[PATCHv3 02/17] mm/khugepaged: Do not collapse pages in encrypted VMAs

[Kirill A. Shutemov]

Pages for encrypted VMAs have to be allocated in a special way:
we would need to propagate down not only desired NUMA node but also
whether the page is encrypted.

It complicates not-so-trivial routine of huge page allocation in
khugepaged even more. It also puts more pressure on page allocator:
we cannot re-use pages allocated for encrypted VMA to collapse
page in unencrypted one or vice versa.

I think for now it worth skipping encrypted VMAs. We can return
to this topic later.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 include/linux/mm.h | 7 +++++++
 mm/khugepaged.c    | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1c3c15f37ed6..435b053c457c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1492,6 +1492,13 @@ static inline bool vma_is_anonymous(struct vm_area_struct *vma)
 	return !vma->vm_ops;
 }
 
+#ifndef vma_is_encrypted
+static inline bool vma_is_encrypted(struct vm_area_struct *vma)
+{
+	return false;
+}
+#endif
+
 #ifndef vma_keyid
 static inline int vma_keyid(struct vm_area_struct *vma)
 {
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index d7b2a4bf8671..a03b40bef033 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -835,6 +835,8 @@ static bool hugepage_vma_check(struct vm_area_struct *vma)
 		return false;
 	if (is_vma_temporary_stack(vma))
 		return false;
+	if (vma_is_encrypted(vma))
+		return false;
 	return !(vma->vm_flags & VM_NO_KHUGEPAGED);
 }
 
-- 
2.17.1