Make installation of kernel uapi header files optional

The bundled kernel's uapi header files ("nilfs2_ondisk.h" and
"nilfs2_api.h") are included in kernel-related development packages
in modern Linux distributions, resulting in duplicate installations.

In order to eliminate this duplication, make the installation of these
files optional and not install them by default.

The utilities will continue to refer to the included uapi header files,
and will only allow installation on the system, which can be specified
using the "--enable-uapi-header-install" option in configure file
arguments.

This is a workaround for older environments and should normally be
disabled.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>

README

@@ -55,6 +55,23 @@ of selinux context mount options (-o context=<context>, etc):
 For helpers built with mount library (libmount), support of the
 context mount depends on the libmount that distro provides.
 
+If you are having problems due to the missing nilfs2 disk format or
+ioctl interface definition file (nilfs2_ondisk.h or nilfs2_api.h,
+respectively), try installing the Linux kernel source or header file
+package first.
+
+If you still cannot install these files, or if you want to overwrite
+them with files from this package, specify the
+"--enable-uapi-header-install" option as an argument to the configure
+script.  This will install the uapi header files included in this
+package:
+
+ $ ./configure --enable-uapi-header-install
+
+Note that the utility package itself references bundled local header
+files, so you don't need to install these files with this option to
+build.
+
 
 * How to get development sources
 

configure.ac

@@ -57,6 +57,12 @@ AC_ARG_WITH([blkid],
 	AS_HELP_STRING([--without-blkid], [compile without blkid support]),
 	[], with_blkid=yes)
 
+AC_ARG_ENABLE([uapi_header_install],
+	AS_HELP_STRING([--enable-uapi-header-install],
+		       [install kernel uapi header files]),
+	[enable_uapi_header_install="${enableval}"],
+	[enable_uapi_header_install=no])
+
 # Checks for libraries.
 AC_CHECK_LIB([uuid], [uuid_generate],
 	[AC_DEFINE([HAVE_LIBUUID], 1,
@@ -139,6 +145,9 @@ if test "${with_selinux}" = "yes"; then
 fi
 AC_SUBST([LIB_SELINUX])
 
+AM_CONDITIONAL(CONFIG_UAPI_HEADER_INSTALL,
+	       [test "$enable_uapi_header_install" = yes])
+
 # Checks for typedefs, structures, and compiler characteristics.
 AC_C_CONST
 AC_C_INLINE

include/Makefile.am

@@ -5,4 +5,8 @@ noinst_HEADERS = realpath.h nls.h parser.h nilfs_feature.h \
 	vector.h nilfs_gc.h cnormap.h cleaner_msg.h cleaner_exec.h \
 	compat.h crc32.h pathnames.h segment.h util.h
 
+if CONFIG_UAPI_HEADER_INSTALL
 nobase_include_HEADERS = linux/nilfs2_api.h linux/nilfs2_ondisk.h
+else
+noinst_HEADERS += linux/nilfs2_api.h linux/nilfs2_ondisk.h
+endif