From a012b59ada6ecbc34fe8e690abb74a2fa8a1d8e6 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Wed, 6 Nov 2019 11:48:57 +0100
Subject: [PATCH] block: Warn if elevator= parameter is used
Patch-mainline: v5.5-rc1
Git-commit: f8db383507d658c5a729b062c97710efda876cd4
References: bsc#1156055

With transition to blk-mq, the elevator= kernel argument was removed as
it makes less and less sense with the current variety of devices.  Since
this may surprise some users and there are advices on the Internet that
still suggest to use it, let's at least warn if the parameter is used.

Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Jan Kara <jack@suse.cz>
---
 block/elevator.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/block/elevator.c b/block/elevator.c
index 5437059c9261..0b1db9afb586 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -831,3 +831,12 @@ struct request *elv_rb_latter_request(struct request_queue *q,
 	return NULL;
 }
 EXPORT_SYMBOL(elv_rb_latter_request);
+
+static int __init elevator_setup(char *str)
+{
+	pr_warn("Kernel parameter elevator= does not have any effect anymore.\n"
+		"Please use sysfs to set IO scheduler for individual devices.\n");
+	return 1;
+}
+
+__setup("elevator=", elevator_setup);
-- 
2.16.4