diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 067538fc4d58..c982694c987b 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -17,7 +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);
-vm_flags_t ksm_vma_flags(const struct mm_struct *mm, const struct file *file,
+vm_flags_t ksm_vma_flags(struct mm_struct *mm, const struct file *file,
 			 vm_flags_t vm_flags);
 int ksm_enable_merge_any(struct mm_struct *mm);
 int ksm_disable_merge_any(struct mm_struct *mm);
@@ -103,7 +103,7 @@ bool ksm_process_mergeable(struct mm_struct *mm);
 
 #else  /* !CONFIG_KSM */
 
-static inline vm_flags_t ksm_vma_flags(const struct mm_struct *mm,
+static inline vm_flags_t ksm_vma_flags(struct mm_struct *mm,
 		const struct file *file, vm_flags_t vm_flags)
 {
 	return vm_flags;
diff --git a/mm/ksm.c b/mm/ksm.c
index cdefba633856..4f672f4f2140 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2712,8 +2712,14 @@ no_vmas:
 		spin_unlock(&ksm_mmlist_lock);
 
 		mm_slot_free(mm_slot_cache, mm_slot);
+		/*
+		 * Only clear MMF_VM_MERGEABLE. We must not clear
+		 * MMF_VM_MERGE_ANY, because for those MMF_VM_MERGE_ANY process,
+		 * perhaps their mm_struct has just been added to ksm_mm_slot
+		 * list, and its process has not yet officially started running
+		 * or has not yet performed mmap/brk to allocate anonymous VMAS.
+		 */
 		mm_flags_clear(MMF_VM_MERGEABLE, mm);
-		mm_flags_clear(MMF_VM_MERGE_ANY, mm);
 		mmap_read_unlock(mm);
 		mmdrop(mm);
 	} else {
@@ -2831,12 +2837,20 @@ static int __ksm_del_vma(struct vm_area_struct *vma)
  *
  * Returns: @vm_flags possibly updated to mark mergeable.
  */
-vm_flags_t ksm_vma_flags(const struct mm_struct *mm, const struct file *file,
+vm_flags_t ksm_vma_flags(struct mm_struct *mm, const struct file *file,
 			 vm_flags_t vm_flags)
 {
 	if (mm_flags_test(MMF_VM_MERGE_ANY, mm) &&
-	    __ksm_should_add_vma(file, vm_flags))
+	    __ksm_should_add_vma(file, vm_flags)) {
 		vm_flags |= VM_MERGEABLE;
+		/*
+		 * Generally, the flags here always include MMF_VM_MERGEABLE.
+		 * However, in rare cases, this flag may be cleared by ksmd who
+		 * scans a cycle without finding any mergeable vma.
+		 */
+		if (unlikely(!mm_flags_test(MMF_VM_MERGEABLE, mm)))
+			__ksm_enter(mm);
+	}
 
 	return vm_flags;
 }