xfs: adjust the incore perag block_count when shrinking

If we reduce the number of blocks in an AG, we must update the incore
geometry values as well.

Fixes: 0800169e3e ("xfs: Pre-calculate per-AG agbno geometry")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_ag.c

@@ -1001,6 +1001,12 @@ xfs_ag_shrink_space(
 		error = -ENOSPC;
 		goto resv_init_out;
 	}
+
+	/* Update perag geometry */
+	pag->block_count -= delta;
+	__xfs_agino_range(pag->pag_mount, pag->block_count, &pag->agino_min,
+				&pag->agino_max);
+
 	xfs_ialloc_log_agi(*tpp, agibp, XFS_AGI_LENGTH);
 	xfs_alloc_log_agf(*tpp, agfbp, XFS_AGF_LENGTH);
 	return 0;