[PATCH mm-unstable v1 1/3] mm/ksm: export ksm_is_running() to check KSM merge state

[Nico Pache <npache@redhat.com>]

Add ksm_is_running() which returns true when KSM is actively merging
(ksm_run & KSM_RUN_MERGE).

This will be used by try_to_map_unused_to_zeropage() to skip zero-page
remapping in VM_MERGEABLE VMAs when KSM is active.

Signed-off-by: Nico Pache <npache@redhat.com>
---
 include/linux/ksm.h | 6 ++++++
 mm/ksm.c            | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index d39d0d5483a2..c1048b690a92 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -17,6 +17,7 @@
 #ifdef CONFIG_KSM
 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 		unsigned long end, int advice, vm_flags_t *vm_flags);
+bool ksm_is_running(void);
 vma_flags_t ksm_vma_flags(struct mm_struct *mm, const struct file *file,
 			  vma_flags_t vma_flags);
 int ksm_enable_merge_any(struct mm_struct *mm);
@@ -144,6 +145,11 @@ static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 	return 0;
 }
 
+static inline bool ksm_is_running(void)
+{
+	return false;
+}
+
 static inline struct folio *ksm_might_need_to_copy(struct folio *folio,
 			struct vm_area_struct *vma, unsigned long addr)
 {
diff --git a/mm/ksm.c b/mm/ksm.c
index 7d5b76478f0b..edc2b961ff59 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -3015,6 +3015,12 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 }
 EXPORT_SYMBOL_GPL(ksm_madvise);
 
+bool ksm_is_running(void)
+{
+	return ksm_run & KSM_RUN_MERGE;
+}
+EXPORT_SYMBOL_GPL(ksm_is_running);
+
 int __ksm_enter(struct mm_struct *mm)
 {
 	struct ksm_mm_slot *mm_slot;
-- 
2.54.0