BR's "store based backup" version check should be tightened and allow restoring to v8.1.1+ etc.

[kennytm]

Enhancement

tidb/br/pkg/version/version.go

Lines 245 to 252 in 1f32c8e

	// 8.2 br(store based backup) does not support tikv <= 8.1
	// due to the performance issue https://github.com/tikv/tikv/issues/17168
	// TODO: we can remove this check if the performance issue is fixed and cherry-pick
	if (BRVersion.Major > 8 || (BRVersion.Major == 8 && BRVersion.Minor >= 2)) &&
	(tikvVersion.Major < 8 || (tikvVersion.Major == 8 && tikvVersion.Minor < 2)) {
	return errors.Annotatef(berrors.ErrVersionMismatch, "TiKV node %s version %s and BR %s version mismatch, please use the same version of BR",
	s.Address, tikvVersion, build.ReleaseVersion)
	}

BR starting from v8.2 rejected interacting with TiKV v8.1 or below even with --check-requirements=false because of tikv/tikv#17168. However, the fix has subsequently cherry-picked back to earlier versions:

• backup: continue to seek regions if one range has no located leader region tikv/tikv#17169 - v8.2+
• backup: continue to seek regions if one range has no located leader region (#17169) tikv/tikv#17198 - v8.1.1+
• backup: continue to seek regions if one range has no located leader region (#17169) tikv/tikv#17196 - v7.5.3+
• backup: continue to seek regions if one range has no located leader region (#17169) tikv/tikv#17197 - v7.1.6+
• backup: continue to seek regions if one range has no located leader region (#17169) tikv/tikv#17195 - v6.5.11+

So, as promised in the TODO, the check should be tightened to check only v6.5.10- / v7.1.5- / v7.5.2- / v8.1.0 or just entirely removed.