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From 1255584bb0a595fb555af7e14230ab1b7aa6adcd Mon Sep 17 00:00:00 2001
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From: Lukas Nykryn <lnykryn@redhat.com>
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Date: Tue, 12 Feb 2019 16:58:16 +0100
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Subject: [PATCH] rules: add elevator= kernel command line parameter
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Kernel removed the elevator= option, so let's reintroduce
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it for rhel8 via udev rule.
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rhel-only
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Resolves: #1670126
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---
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 rules/40-elevator.rules | 20 ++++++++++++++++++++
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 1 file changed, 20 insertions(+)
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 create mode 100644 rules/40-elevator.rules
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diff --git a/rules/40-elevator.rules b/rules/40-elevator.rules
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new file mode 100644
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index 000000000..dbe8fc81a
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--- /dev/null
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+++ b/rules/40-elevator.rules
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@@ -0,0 +1,20 @@
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+# We aren't adding devices skip the elevator check
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+ACTION!="add", GOTO="sched_out"
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+
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+SUBSYSTEM!="block", GOTO="sched_out"
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+ENV{DEVTYPE}!="disk", GOTO="sched_out"
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+
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+# Technically, dm-multipath can be configured to use an I/O scheduler.
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+# However, there are races between the 'add' uevent and the linking in
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+# of the queue/scheduler sysfs file.  For now, just skip dm- devices.
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+KERNEL=="dm-*|md*", GOTO="sched_out"
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+
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+# Skip bio-based devices, which don't support an I/O scheduler.
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+ATTR{queue/scheduler}=="none", GOTO="sched_out"
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+
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+# If elevator= is specified on the kernel command line, change the
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+# scheduler to the one specified.
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+IMPORT{cmdline}="elevator"
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+ENV{elevator}!="", ATTR{queue/scheduler}="$env{elevator}"
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+
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+LABEL="sched_out"
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\ No newline at end of file