From 1255584bb0a595fb555af7e14230ab1b7aa6adcd Mon Sep 17 00:00:00 2001
From: Lukas Nykryn <[email protected]>
Date: Tue, 12 Feb 2019 16:58:16 +0100
Subject: [PATCH] rules: add elevator= kernel command line parameter

Kernel removed the elevator= option, so let's reintroduce
it for rhel8 via udev rule.

rhel-only
Resolves: #1670126
---
 rules/40-elevator.rules | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 rules/40-elevator.rules

diff --git a/rules/40-elevator.rules b/rules/40-elevator.rules
new file mode 100644
index 0000000000..dbe8fc81a4
--- /dev/null
+++ b/rules/40-elevator.rules
@@ -0,0 +1,20 @@
+# We aren't adding devices skip the elevator check
+ACTION!="add", GOTO="sched_out"
+
+SUBSYSTEM!="block", GOTO="sched_out"
+ENV{DEVTYPE}!="disk", GOTO="sched_out"
+
+# Technically, dm-multipath can be configured to use an I/O scheduler.
+# However, there are races between the 'add' uevent and the linking in
+# of the queue/scheduler sysfs file.  For now, just skip dm- devices.
+KERNEL=="dm-*|md*", GOTO="sched_out"
+
+# Skip bio-based devices, which don't support an I/O scheduler.
+ATTR{queue/scheduler}=="none", GOTO="sched_out"
+
+# If elevator= is specified on the kernel command line, change the
+# scheduler to the one specified.
+IMPORT{cmdline}="elevator"
+ENV{elevator}!="", ATTR{queue/scheduler}="$env{elevator}"
+
+LABEL="sched_out"
\ No newline at end of file