xfs: add a xfs_rtgroup_raw_size helper

Add a helper to figure the on-disk size of a group, accounting for the
XFS_SB_FEAT_INCOMPAT_ZONE_GAPS feature if needed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

Author: Christoph Hellwig

fs/xfs/libxfs/xfs_rtgroup.h

@@ -371,4 +371,19 @@ xfs_rtgs_to_rfsbs(
 	return xfs_groups_to_rfsbs(mp, nr_groups, XG_TYPE_RTG);
 }
 
+/*
+ * Return the "raw" size of a group on the hardware device.  This includes the
+ * daddr gaps present for XFS_SB_FEAT_INCOMPAT_ZONE_GAPS file systems.
+ */
+static inline xfs_rgblock_t
+xfs_rtgroup_raw_size(
+	struct xfs_mount	*mp)
+{
+	struct xfs_groups	*g = &mp->m_groups[XG_TYPE_RTG];
+
+	if (g->has_daddr_gaps)
+		return 1U << g->blklog;
+	return g->blocks;
+}
+
 #endif /* __LIBXFS_RTGROUP_H */