[PATCH RFC v2 1/4] mm/ksm: introduce ksm_enter() helper

Oleksandr Natalenko
2019-05-14T13:17:06Z

Move MADV_MERGEABLE part of ksm_madvise() into a dedicated helper since
it will be further used for marking VMAs to be merged forcibly.

This does not bring any functional changes.

Signed-off-by: Oleksandr Natalenko <oleksandr@redhat.com>
---
mm/ksm.c | 60 +++++++++++++++++++++++++++++++++-----------------------
1 file changed, 36 insertions(+), 24 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index fc64874dc6f4..02fdbee394cc 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2442,41 +2442,53 @@ static int ksm_scan_thread(void *nothing)
return 0;
}

-int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
- unsigned long end, int advice, unsigned long *vm_flags)
+static int ksm_enter(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long *vm_flags)
{
- struct mm_struct *mm = vma->vm_mm;
int err;

- switch (advice) {
- case MADV_MERGEABLE:
- /*
- * Be somewhat over-protective for now!
- */
- if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE |
- VM_PFNMAP | VM_IO | VM_DONTEXPAND |
- VM_HUGETLB | VM_MIXEDMAP))
- return 0; /* just ignore the advice */
+ /*
+ * Be somewhat over-protective for now!
+ */
+ if (*vm_flags & (VM_MERGEABLE | VM_SHARED | VM_MAYSHARE |
+ VM_PFNMAP | VM_IO | VM_DONTEXPAND |
+ VM_HUGETLB | VM_MIXEDMAP))
+ return 0; /* just ignore the advice */

- if (vma_is_dax(vma))
- return 0;
+ if (vma_is_dax(vma))
+ return 0;

#ifdef VM_SAO
- if (*vm_flags & VM_SAO)
- return 0;
+ if (*vm_flags & VM_SAO)
+ return 0;
#endif
#ifdef VM_SPARC_ADI
- if (*vm_flags & VM_SPARC_ADI)
- return 0;
+ if (*vm_flags & VM_SPARC_ADI)
+ return 0;
#endif

- if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) {
- err = __ksm_enter(mm);
- if (err)
- return err;
- }
+ if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) {
+ err = __ksm_enter(mm);
+ if (err)
+ return err;
+ }
+
+ *vm_flags |= VM_MERGEABLE;
+
+ return 0;
+}

- *vm_flags |= VM_MERGEABLE;
+int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
+ unsigned long end, int advice, unsigned long *vm_flags)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ int err;
+
+ switch (advice) {
+ case MADV_MERGEABLE:
+ err = ksm_enter(mm, vma, vm_flags);
+ if (err)
+ return err;
break;

case MADV_UNMERGEABLE:
--
2.21.0