xfs: fold xfs_rmapbt_init_common into xfs_rmapbt_init_cursor

Make the levels initialization in xfs_rmapbt_init_cursor conditional
and merge the two helpers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

fs/xfs/libxfs/xfs_rmap_btree.c

@@ -502,21 +502,11 @@ const struct xfs_btree_ops xfs_rmapbt_ops = {
 	.keys_contiguous	= xfs_rmapbt_keys_contiguous,
 };
 
-static struct xfs_btree_cur *
-xfs_rmapbt_init_common(
-	struct xfs_mount	*mp,
-	struct xfs_trans	*tp,
-	struct xfs_perag	*pag)
-{
-	struct xfs_btree_cur	*cur;
-
-	cur = xfs_btree_alloc_cursor(mp, tp, XFS_BTNUM_RMAP, &xfs_rmapbt_ops,
-			mp->m_rmap_maxlevels, xfs_rmapbt_cur_cache);
-	cur->bc_ag.pag = xfs_perag_hold(pag);
-	return cur;
-}
-
-/* Create a new reverse mapping btree cursor. */
+/*
+ * Create a new reverse mapping btree cursor.
+ *
+ * For staging cursors tp and agbp are NULL.
+ */
 struct xfs_btree_cur *
 xfs_rmapbt_init_cursor(
 	struct xfs_mount	*mp,
@@ -524,12 +514,17 @@ xfs_rmapbt_init_cursor(
 	struct xfs_buf		*agbp,
 	struct xfs_perag	*pag)
 {
-	struct xfs_agf		*agf = agbp->b_addr;
 	struct xfs_btree_cur	*cur;
 
-	cur = xfs_rmapbt_init_common(mp, tp, pag);
-	cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]);
+	cur = xfs_btree_alloc_cursor(mp, tp, XFS_BTNUM_RMAP, &xfs_rmapbt_ops,
+			mp->m_rmap_maxlevels, xfs_rmapbt_cur_cache);
+	cur->bc_ag.pag = xfs_perag_hold(pag);
 	cur->bc_ag.agbp = agbp;
+	if (agbp) {
+		struct xfs_agf		*agf = agbp->b_addr;
+
+		cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]);
+	}
 	return cur;
 }
 
@@ -542,7 +537,7 @@ xfs_rmapbt_stage_cursor(
 {
 	struct xfs_btree_cur	*cur;
 
-	cur = xfs_rmapbt_init_common(mp, NULL, pag);
+	cur = xfs_rmapbt_init_cursor(mp, NULL, NULL, pag);
 	xfs_btree_stage_afakeroot(cur, afake);
 	return cur;
 }