[PATCH v1 3/3] mm/ksm: move disabling KSM from s390/gmap code to KSM code

David Hildenbrand
2023-04-18T15:30:39Z

Let's factor out actual disabling of KSM. The existing
"mm->def_flags &= ~VM_MERGEABLE;" was essentially a NOP and can be dropped,
because def_flags should never include VM_MERGEABLE. Note that we don't
currently prevent re-enabling KSM.

This should now be faster in case KSM was never enabled, because we only
conditionally iterate all VMAs. Further, it certainly looks cleaner.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
arch/s390/mm/gmap.c | 20 +-------------------
include/linux/ksm.h | 6 ++++++
mm/ksm.c | 11 +++++++++++
3 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 0949811761e6..dfe905c7bd8e 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2585,30 +2585,12 @@ EXPORT_SYMBOL_GPL(s390_enable_sie);

int gmap_mark_unmergeable(void)
{
- struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma;
- unsigned long vm_flags;
- int ret;
- VMA_ITERATOR(vmi, mm, 0);
-
/*
* Make sure to disable KSM (if enabled for the whole process or
* individual VMAs). Note that nothing currently hinders user space
* from re-enabling it.
*/
- clear_bit(MMF_VM_MERGE_ANY, &mm->flags);
-
- for_each_vma(vmi, vma) {
- /* Copy vm_flags to avoid partial modifications in ksm_madvise */
- vm_flags = vma->vm_flags;
- ret = ksm_madvise(vma, vma->vm_start, vma->vm_end,
- MADV_UNMERGEABLE, &vm_flags);
- if (ret)
- return ret;
- vm_flags_reset(vma, vm_flags);
- }
- mm->def_flags &= ~VM_MERGEABLE;
- return 0;
+ return ksm_disable(current->mm);
}
EXPORT_SYMBOL_GPL(gmap_mark_unmergeable);

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 7108bc65dc2a..b3d8b7849e18 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -22,6 +22,7 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
void ksm_add_vma(struct vm_area_struct *vma);
int ksm_enable_merge_any(struct mm_struct *mm);
int ksm_disable_merge_any(struct mm_struct *mm);
+int ksm_disable(struct mm_struct *mm);

int __ksm_enter(struct mm_struct *mm);
void __ksm_exit(struct mm_struct *mm);
@@ -75,6 +76,11 @@ static inline void ksm_add_vma(struct vm_area_struct *vma)
{
}

+static inline int ksm_disable(struct mm_struct *mm)
+{
+ return 0;
+}
+
static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
{
return 0;
diff --git a/mm/ksm.c b/mm/ksm.c
index 813f7fbc1832..208311cbb019 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2616,6 +2616,17 @@ int ksm_disable_merge_any(struct mm_struct *mm)
return 0;
}

+int ksm_disable(struct mm_struct *mm)
+{
+ mmap_assert_write_locked(mm);
+
+ if (!test_bit(MMF_VM_MERGEABLE, &mm->flags))
+ return 0;
+ if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+ return ksm_disable_merge_any(mm);
+ return ksm_del_vmas(mm);
+}
+
int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
unsigned long end, int advice, unsigned long *vm_flags)
{
--
2.39.2