+AC_MSG_CHECKING([whether to build ldiskfs based on ext4])
+if test x$RHEL_KERNEL = xyes; then
+ AC_ARG_ENABLE([ext4],
+ AC_HELP_STRING([--enable-ext4],
+ [enable building of ldiskfs based on ext4]),
+ [], [enable_ext4='no'])
+else
+ case $LINUXRELEASE in
+ # ext4 was in 2.6.22-2.6.26 but not stable enough to use
+ 2.6.2[06]*) enable_ext4='no' ;;
+ *) LC_KERNEL_WITH_EXT4([enable_ext4='yes'],
+ [enable_ext4='no']) ;;
+ esac
+fi
+AC_MSG_RESULT([$enable_ext4])
+
+if test x$enable_ext4 = xyes ; then
+ AC_DEFINE(HAVE_EXT4_LDISKFS, 1, [ldiskfs based on ext4])
+ BACKFS=ext4
+else
+ BACKFS=ext3
+fi
+
+AC_SUBST(BACKFS)
+BACKFSU=${BACKFS/ext/EXT}
+AC_SUBST(BACKFSU) # We need a Upper string
+
+AM_CONDITIONAL(USE_EXT4, test x$enable_ext4 = xyes)
+