loggen: fix build vs. newer xfsprogs headers

v2: just include xfs/libxfs.h for the conftest prerequisites

commit cc085d770adb in xfsprogs removed some header files that are
included by loggen.c. Add an autoconf test that checks to see whether
xfs_log_format.h is present. If it is, include that instead of the
deprecated headers and add an alias for XFS_TRANS_MAGIC since that
value no longer exists.

With this patch, xfstests builds on both f20 and rawhide (f21) boxes.

Signed-off-by: Jeff Layton <jlayton@poochiereds.net>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

configure.ac

@@ -26,14 +26,15 @@ AC_HEADER_STDC
 			sys/types.h		\
 			strings.h		\
 			err.h			\
-			linux/falloc.h
-    ])
-    AC_CHECK_HEADERS([	sys/fs/xfs_fsops.h	\
+			linux/falloc.h		\
+			sys/fs/xfs_fsops.h	\
 			sys/fs/xfs_itable.h	\
 			xfs/platform_defs.h	\
 			btrfs/ioctl.h		\
     ])
 
+AC_CHECK_HEADERS([xfs/xfs_log_format.h],,,[#include <xfs/libxfs.h>])
+
 AC_PACKAGE_NEED_UUIDCOMPARE
 
 case $pkg_platform

src/loggen.c

@@ -25,9 +25,16 @@
  *                                                  - dxm 29/09/00
  */
 
+#include <config.h>
+
 #include <xfs/libxfs.h>
+#ifdef HAVE_XFS_XFS_LOG_FORMAT_H
+#include <xfs/xfs_log_format.h>
+#define XFS_TRANS_MAGIC	XFS_TRANS_HEADER_MAGIC
+#else /* HAVE_XFS_XFS_LOG_FORMAT_H */
 #include <xfs/xfs_log.h>
 #include <xfs/xfs_log_priv.h>
+#endif /* HAVE_XFS_XFS_LOG_FORMAT_H */
 
 #ifndef ASSIGN_ANY_LSN_DISK
 #define ASSIGN_ANY_LSN_DISK(lsn,cycle,block)  \