mm/ksm: move disabling KSM from s390/gmap code to KSM code

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.

Link: https://lkml.kernel.org/r/20230422210156.33630-1-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Acked-by: Stefan Roesch <shr@devkernel.io>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index 823bb3475a68..0156bded3a66 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2628,6 +2628,17 @@ 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)
 {