xfs: add rmap btree geometry feature flag

Originally-From: Dave Chinner <dchinner@redhat.com>

So xfs_info and other userspace utilities know the filesystem is
using this feature.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/libxfs/xfs_fs.h

@@ -206,6 +206,7 @@ typedef struct xfs_fsop_resblks {
 #define XFS_FSOP_GEOM_FLAGS_FTYPE	0x10000	/* inode directory types */
 #define XFS_FSOP_GEOM_FLAGS_FINOBT	0x20000	/* free inode btree */
 #define XFS_FSOP_GEOM_FLAGS_SPINODES	0x40000	/* sparse inode chunks	*/
+#define XFS_FSOP_GEOM_FLAGS_RMAPBT	0x80000	/* Reverse mapping btree */
 
 /*
  * Minimum and maximum sizes need for growth checks.

fs/xfs/xfs_fsops.c

@@ -106,7 +106,9 @@ xfs_fs_geometry(
 			(xfs_sb_version_hasfinobt(&mp->m_sb) ?
 				XFS_FSOP_GEOM_FLAGS_FINOBT : 0) |
 			(xfs_sb_version_hassparseinodes(&mp->m_sb) ?
-				XFS_FSOP_GEOM_FLAGS_SPINODES : 0);
+				XFS_FSOP_GEOM_FLAGS_SPINODES : 0) |
+			(xfs_sb_version_hasrmapbt(&mp->m_sb) ?
+				XFS_FSOP_GEOM_FLAGS_RMAPBT : 0);
 		geo->logsectsize = xfs_sb_version_hassector(&mp->m_sb) ?
 				mp->m_sb.sb_logsectsize : BBSIZE;
 		geo->rtsectsize = mp->m_sb.sb_blocksize;