cherry pick pingcap#29730 to release-5.3

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

br/pkg/backup/schema.go

@@ -88,10 +88,13 @@ func (ss *Schemas) BackupSchemas(
 	metaWriter.StartWriteMetasAsync(ctx, op)
 	for _, s := range ss.schemas {
 		schema := s
+		// Because schema.dbInfo is a pointer that many tables point to.
+		// Remove "add Temporary-prefix into dbName" from closure to prevent concurrent operations.
+		if utils.IsSysDB(schema.dbInfo.Name.L) {
+			schema.dbInfo.Name = utils.TemporaryDBName(schema.dbInfo.Name.O)
+		}
+
 		workerPool.ApplyOnErrorGroup(errg, func() error {
-			if utils.IsSysDB(schema.dbInfo.Name.L) {
-				schema.dbInfo.Name = utils.TemporaryDBName(schema.dbInfo.Name.O)
-			}
 			logger := log.With(
 				zap.String("db", schema.dbInfo.Name.O),
 				zap.String("table", schema.tableInfo.Name.O),

br/pkg/backup/schema_test.go

@@ -4,7 +4,9 @@ package backup_test
 
 import (
 	"context"
+	"fmt"
 	"math"
+	"strings"
 	"sync/atomic"
 
 	"github.com/golang/protobuf/proto"
@@ -16,6 +18,7 @@ import (
 	"github.com/pingcap/tidb/br/pkg/metautil"
 	"github.com/pingcap/tidb/br/pkg/mock"
 	"github.com/pingcap/tidb/br/pkg/storage"
+	"github.com/pingcap/tidb/br/pkg/utils"
 	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/util/testkit"
 	"github.com/pingcap/tidb/util/testleak"
@@ -260,3 +263,42 @@ func (s *testBackupSchemaSuite) TestBuildBackupRangeAndSchemaWithBrokenStats(c *
 	c.Assert(schemas2[0].Info, DeepEquals, schemas[0].Info)
 	c.Assert(schemas2[0].DB, DeepEquals, schemas[0].DB)
 }
+
+func (s *testBackupSchemaSuite) TestBackupSchemasForSystemTable(c *C) {
+	tk := testkit.NewTestKit(c, s.mock.Storage)
+	es2 := s.GetRandomStorage(c)
+
+	systemTablesCount := 32
+	tablePrefix := "systable"
+	tk.MustExec("use mysql")
+	for i := 1; i <= systemTablesCount; i++ {
+		query := fmt.Sprintf("create table %s%d (a char(1));", tablePrefix, i)
+		tk.MustExec(query)
+	}
+
+	f, err := filter.Parse([]string{"mysql.systable*"})
+	c.Assert(err, IsNil)
+	_, backupSchemas, err := backup.BuildBackupRangeAndSchema(s.mock.Storage, f, math.MaxUint64)
+	c.Assert(err, IsNil)
+	c.Assert(backupSchemas.Len(), Equals, systemTablesCount)
+
+	ctx := context.Background()
+	cipher := backuppb.CipherInfo{
+		CipherType: encryptionpb.EncryptionMethod_PLAINTEXT,
+	}
+	updateCh := new(simpleProgress)
+
+	metaWriter2 := metautil.NewMetaWriter(es2, metautil.MetaFileSize, false, &cipher)
+	err = backupSchemas.BackupSchemas(ctx, metaWriter2, s.mock.Storage, nil,
+		math.MaxUint64, 1, variable.DefChecksumTableConcurrency, true, updateCh)
+	c.Assert(err, IsNil)
+	err = metaWriter2.FlushBackupMeta(ctx)
+	c.Assert(err, IsNil)
+
+	schemas2 := s.GetSchemasFromMeta(c, es2)
+	c.Assert(schemas2, HasLen, systemTablesCount)
+	for _, schema := range schemas2 {
+		c.Assert(schema.DB.Name, Equals, utils.TemporaryDBName("mysql"))
+		c.Assert(strings.HasPrefix(schema.Info.Name.O, tablePrefix), Equals, true)
+	}
+}