xfs_bmap_split_extent_at(
        struct xfs_trans        *tp,
        struct xfs_inode        *ip,
-       xfs_fileoff_t           split_fsb,
-       xfs_fsblock_t           *firstfsb)
+       xfs_fileoff_t           split_fsb)
 {
        int                             whichfork = XFS_DATA_FORK;
        struct xfs_btree_cur            *cur = NULL;
 
        if (ifp->if_flags & XFS_IFBROOT) {
                cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
-               cur->bc_private.b.firstblock = *firstfsb;
+               cur->bc_private.b.firstblock = tp->t_firstblock;
                cur->bc_private.b.flags = 0;
                error = xfs_bmbt_lookup_eq(cur, &got, &i);
                if (error)
                int tmp_logflags; /* partial log flag return val */
 
                ASSERT(cur == NULL);
-               error = xfs_bmap_extents_to_btree(tp, ip, firstfsb, &cur, 0,
-                               &tmp_logflags, whichfork);
+               error = xfs_bmap_extents_to_btree(tp, ip, &tp->t_firstblock,
+                               &cur, 0, &tmp_logflags, whichfork);
                logflags |= tmp_logflags;
        }
 
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        struct xfs_defer_ops    dfops;
-       xfs_fsblock_t           firstfsb;
        int                     error;
 
        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write,
                        XFS_DIOSTRAT_SPACE_RES(mp, 0), 0, 0, &tp);
        if (error)
                return error;
-       xfs_defer_init(tp, &dfops, &firstfsb);
+       xfs_defer_init(tp, &dfops, &tp->t_firstblock);
 
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
 
-       error = xfs_bmap_split_extent_at(tp, ip, split_fsb,
-                                        &firstfsb);
+       error = xfs_bmap_split_extent_at(tp, ip, split_fsb);
        if (error)
                goto out;