[RFC patch 3/7] thp: make MADV_HUGEPAGE check for mm->def_flags

Gerald Schaefer
2012-08-23T17:19:07Z

[-- Attachment #1: linux-3.5-thp-madvise.patch --]
[-- Type: text/plain, Size: 977 bytes --]

This adds a check to hugepage_madvise(), to refuse MADV_HUGEPAGE
if VM_NOHUGEPAGE is set in mm->def_flags. On System z, the VM_NOHUGEPAGE
flag will be set in mm->def_flags for kvm processes, to prevent any
future thp mappings. In order to also prevent MADV_HUGEPAGE on such an
mm, hugepage_madvise() should check mm->def_flags.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
---
mm/huge_memory.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1464,6 +1464,8 @@ out:
int hugepage_madvise(struct vm_area_struct *vma,
unsigned long *vm_flags, int advice)
{
+ struct mm_struct *mm = vma->vm_mm;
+
switch (advice) {
case MADV_HUGEPAGE:
/*
@@ -1471,6 +1473,8 @@ int hugepage_madvise(struct vm_area_stru
*/
if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
return -EINVAL;
+ if (mm->def_flags & VM_NOHUGEPAGE)
+ return -EINVAL;
*vm_flags &= ~VM_NOHUGEPAGE;
*vm_flags |= VM_HUGEPAGE;
/*