From 6d1d976b2c2c6b80de75a480c998466068066846 Mon Sep 17 00:00:00 2001
From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Mon, 27 Aug 2012 03:38:06 +0700
Subject: Modify vdev_elevator_switch() to use elevator_change()

As of Linux 2.6.36 an elevator_change() interface was added.
This commit updates vdev_elevator_switch() to use this interface
when available, otherwise it falls back to the usermodehelper
method.

Original-patch-by: foobarz <sysop@xeon.(none)>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #906
---
 config/kernel-elevator-change.m4 | 25 +++++++++++++++++++++++++
 config/kernel.m4                 |  1 +
 2 files changed, 26 insertions(+)
 create mode 100644 config/kernel-elevator-change.m4

(limited to 'config')

diff --git a/config/kernel-elevator-change.m4 b/config/kernel-elevator-change.m4
new file mode 100644
index 000000000..90ab51b2e
--- /dev/null
+++ b/config/kernel-elevator-change.m4
@@ -0,0 +1,25 @@
+dnl #
+dnl # 2.6.36 API change
+dnl # Verify the elevator_change() symbol is available.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_ELEVATOR_CHANGE], [
+	AC_MSG_CHECKING([whether elevator_change() is available])
+	tmp_flags="$EXTRA_KCFLAGS"
+	EXTRA_KCFLAGS="-Wno-unused-but-set-variable"
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/blkdev.h>
+		#include <linux/elevator.h>
+	],[
+		int ret;
+		struct request_queue *q = NULL;
+		char *elevator = NULL;
+		ret = elevator_change(q, elevator);
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_ELEVATOR_CHANGE, 1,
+			  [elevator_change() is available])
+	],[
+		AC_MSG_RESULT(no)
+	])
+	EXTRA_KCFLAGS="$tmp_flags"
+])
diff --git a/config/kernel.m4 b/config/kernel.m4
index 262dc7fcb..89b0a9806 100644
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -67,6 +67,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_BDI
 	ZFS_AC_KERNEL_BDI_SETUP_AND_REGISTER
 	ZFS_AC_KERNEL_SET_NLINK
+	ZFS_AC_KERNEL_ELEVATOR_CHANGE
 
 	AS_IF([test "$LINUX_OBJ" != "$LINUX"], [
 		KERNELMAKE_PARAMS="$KERNELMAKE_PARAMS O=$LINUX_OBJ"
-- 
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