mirror_zfs/config/kernel-blk-queue-flush.m4
Brian Behlendorf e191b54ecf 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
2013-01-10 16:09:39 -08:00

47 lines
1.4 KiB
Plaintext

dnl #
dnl # 2.6.36 API change
dnl # In 2.6.36 kernels the blk_queue_ordered() interface has been
dnl # replaced by the simpler blk_queue_flush(). However, while the
dnl # old interface was available to all the new one is GPL-only.
dnl # Thus in addition to detecting if this function is available
dnl # we determine if it is GPL-only. If the GPL-only interface is
dnl # there we implement our own compatibility function, otherwise
dnl # we use the function. The hope is that long term this function
dnl # will be opened up.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_BLK_QUEUE_FLUSH], [
AC_MSG_CHECKING([whether blk_queue_flush() is available])
tmp_flags="$EXTRA_KCFLAGS"
EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
ZFS_LINUX_TRY_COMPILE([
#include <linux/blkdev.h>
],[
struct request_queue *q = NULL;
(void) blk_queue_flush(q, REQ_FLUSH);
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BLK_QUEUE_FLUSH, 1,
[blk_queue_flush() is available])
],[
AC_MSG_RESULT(no)
])
AC_MSG_CHECKING([whether blk_queue_flush() is GPL-only])
ZFS_LINUX_TRY_COMPILE([
#include <linux/module.h>
#include <linux/blkdev.h>
MODULE_LICENSE("CDDL");
],[
struct request_queue *q = NULL;
(void) blk_queue_flush(q, REQ_FLUSH);
],[
AC_MSG_RESULT(no)
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BLK_QUEUE_FLUSH_GPL_ONLY, 1,
[blk_queue_flush() is GPL-only])
])
EXTRA_KCFLAGS="$tmp_flags"
])