[PATCH v4] mm/kfence: print disabling or re-enabling message

[Jackie Liu <liu.yun@xxxxxxxxx>]

From: Jackie Liu <liuyun01@xxxxxxxxxx>

By printing information, we can friendly prompt the status change
information of kfence by dmesg and record by syslog.

Also, set kfence_enabled to false only when needed.

Co-developed-by: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Jackie Liu <liuyun01@xxxxxxxxxx>
---
 v1->v2:
   fixup by Marco Elver <elver@xxxxxxxxxx>
 v2->v3:
   write kfence_enabled=false only true before
 v3->v4:
   cleanup

 mm/kfence/core.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 11a954763be9..af0489d4d149 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -67,8 +67,11 @@ static int param_set_sample_interval(const char *val, const struct kernel_param
 	if (ret < 0)
 		return ret;
 
-	if (!num) /* Using 0 to indicate KFENCE is disabled. */
+	/* Using 0 to indicate KFENCE is disabled. */
+	if (!num && READ_ONCE(kfence_enabled)) {
+		pr_info("disabled\n");
 		WRITE_ONCE(kfence_enabled, false);
+	}
 
 	*((unsigned long *)kp->arg) = num;
 
@@ -874,6 +877,7 @@ static int kfence_enable_late(void)
 
 	WRITE_ONCE(kfence_enabled, true);
 	queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
+	pr_info("re-enabled\n");
 	return 0;
 }
 
-- 
2.25.1