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zfs/config/kernel-elevator-change.m4

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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
2012-08-26 20:38:06 +00:00
dnl #
Linux 4.14 compat: blk_queue_stackable() The blk_queue_stackable() function was replaced in the 4.14 kernel by queue_is_rq_based(), commit torvalds/linux@5fdee212. This change resulted in the default elevator being used which can negatively impact performance. Rather than adding additional compatibility code to detect the new interface unconditionally attempt to set the elevator. Since we expect this to fail for block devices without an elevator the error message has been moved in to zfs_dbgmsg(). Finally, it was observed that the elevator_change() was removed from the 4.12 kernel, commit torvalds/linux@c033269. Update the comment to clearly specify which are expected to export the elevator_change() symbol. Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Tony Hutter <hutter2@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #7645
2018-06-20 04:52:45 +00:00
dnl # 2.6.36 API, exported elevator_change() symbol
dnl # 4.12 API, removed elevator_change() symbol
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
2012-08-26 20:38:06 +00:00
dnl #
AC_DEFUN([ZFS_AC_KERNEL_ELEVATOR_CHANGE], [
AC_MSG_CHECKING([whether elevator_change() is available])
tmp_flags="$EXTRA_KCFLAGS"
Only use gcc -Wunused-but-set-variable when available Certain versions of gcc generate an 'unrecognized command line option' error message when -Wunused-but-set-variable is used unconditionally. This in turn can cause several of the autoconf tests to misdetect an interface. Now, the use of -Wunused-but-set-variable in the autoconf tests was introduced by commit b9c59ec8 to address a gcc 4.6 compatibility problem. So we really only need to pass this option for version of gcc which are known to support it. Therefore, the tests have been updated to use the result of the existing ZFS_AC_CONFIG_ALWAYS_NO_UNUSED_BUT_SET_VARIABLE which determines if gcc supports this option. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1004
2013-01-11 00:09:31 +00:00
EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
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
2012-08-26 20:38:06 +00:00
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"
])