build-sys: don't check for swapon() number of arguments

The syscall swapon() with two arguments is supported since Linux 1.3.2
and it's really long time ago... Let's assume that all libc header files
have been already fixed.

Signed-off-by: Karel Zak <kzak@redhat.com>

configure.ac

@@ -343,20 +343,6 @@ AC_CHECK_MEMBERS([struct termios.c_line],,,
 AC_CHECK_MEMBERS([struct stat.st_mtim.tv_nsec],,,
 	[#include <sys/stat.h>])
 
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
-[[
-#ifdef HAVE_SYS_SWAP_H
-# include <sys/swap.h>
-#endif
-#include <unistd.h>
-]],
-[[swapon("/dev/null", 0);]])],
-[AC_DEFINE([SWAPON_HAS_TWO_ARGS], [1], [Is swapon() declared with two parameters?])
-],
-[AC_MSG_NOTICE([Your libc thinks that swapon has 1 arg only.])
-])
-
-
 AC_CHECK_DECLS([_NL_TIME_WEEK_1STDAY],[],[],[[#include <langinfo.h>]])
 
 AC_CHECK_DECL([llseek],
@@ -1431,10 +1417,14 @@ AM_CONDITIONAL([BUILD_FSTRIM], [test "x$build_fstrim" = xyes])
 
 UL_BUILD_INIT([swapon], [check])
 UL_REQUIRES_LINUX([swapon])
+UL_REQUIRES_SYSCALL_CHECK([swapon], [UL_CHECK_SYSCALL([swapon])], [swapon])
+UL_REQUIRES_SYSCALL_CHECK([swapon], [UL_CHECK_SYSCALL([swapoff])], [swapoff])
 UL_REQUIRES_BUILD([swapon], [libblkid])
 UL_REQUIRES_BUILD([swapon], [libmount])
 UL_REQUIRES_BUILD([swapon], [libsmartcols])
 AM_CONDITIONAL([BUILD_SWAPON], [test "x$build_swapon" = xyes])
+AC_CHECK_FUNCS([swapon])
+AC_CHECK_FUNCS([swapoff])
 
 
 UL_BUILD_INIT([lsblk], [check])

sys-utils/swapoff.c

@@ -14,8 +14,7 @@
 #include "swapprober.h"
 #include "swapon-common.h"
 
-#ifndef SWAPON_HAS_TWO_ARGS
-/* libc is insane, let's call the kernel */
+#if !defined(HAVE_SWAPOFF) && defined(SYS_swapoff)
 # include <sys/syscall.h>
 # define swapoff(path) syscall(SYS_swapoff, path)
 #endif

sys-utils/swapon.c

@@ -59,8 +59,7 @@
 # define SWAP_FLAG_PRIO_SHIFT	0
 #endif
 
-#ifndef SWAPON_HAS_TWO_ARGS
-/* libc is insane, let's call the kernel */
+#if !defined(HAVE_SWAPON) && defined(SYS_swapon)
 # include <sys/syscall.h>
 # define swapon(path, flags) syscall(SYS_swapon, path, flags)
 #endif