xfs: be more explicit if RT mount fails due to config

Recent testers were slightly confused that a realtime mount failed
due to missing CONFIG_XFS_RT; we can make that a little more
obvious.

V2: drop the else as suggested by Christoph
Signed-off-by: NEric Sandeen <sandeen@sandeen.net>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAlex Elder <aelder@sgi.com>

fs/xfs/xfs_rtalloc.h

@@ -147,7 +147,16 @@ xfs_growfs_rt(
 # define xfs_rtfree_extent(t,b,l)                       (ENOSYS)
 # define xfs_rtpick_extent(m,t,l,rb)                    (ENOSYS)
 # define xfs_growfs_rt(mp,in)                           (ENOSYS)
-# define xfs_rtmount_init(m)    (((mp)->m_sb.sb_rblocks == 0)? 0 : (ENOSYS))
+static inline int		/* error */
+xfs_rtmount_init(
+	xfs_mount_t	*mp)	/* file system mount structure */
+{
+	if (mp->m_sb.sb_rblocks == 0)
+		return 0;
+
+	cmn_err(CE_WARN, "XFS: Not built with CONFIG_XFS_RT");
+	return ENOSYS;
+}
 # define xfs_rtmount_inodes(m)  (((mp)->m_sb.sb_rblocks == 0)? 0 : (ENOSYS))
 # define xfs_rtunmount_inodes(m)
 #endif	/* CONFIG_XFS_RT */