Add FILEID_INVALID macro

FILEID_INVALID macro doesn't exist in kernel 3.7 and earlier.  This
adds it to allow build on the earlier kernels.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

fs/nilfs2/kern_feature.h

@@ -137,6 +137,13 @@
 # define HAVE_WAIT_FOR_STABLE_PAGE \
 	(LINUX_VERSION_CODE >= KERNEL_VERSION(3, 9, 0))
 #endif
+/*
+ * FILEID_INVALID was introduced in kernel 3.8
+ */
+#ifndef HAVE_FILEID_INVALID
+# define HAVE_FILEID_INVALID \
+	(LINUX_VERSION_CODE >= KERNEL_VERSION(3, 8, 0))
+#endif
 #endif /* LINUX_VERSION_CODE */
 
 
@@ -226,4 +233,8 @@ static inline void wait_for_stable_page(struct page *page)
 }
 #endif
 
+#if !HAVE_FILEID_INVALID
+# define FILEID_INVALID	0xff
+#endif
+
 #endif /* NILFS_KERN_FEATURE_H */

fs/nilfs2/namei.c

@@ -39,6 +39,7 @@
  */
 
 #include <linux/pagemap.h>
+#include "kern_feature.h"
 #include "nilfs.h"
 #include "export.h"