Add index causes DDL to get stuck when the temp dir does not exist

[tangenta]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. Create a TiDB cluster and bootstrap it.
2. Remove the directory /tmp/tmp_ddl-4000.
3. Turn on the fast add index feature: set global tidb_ddl_enable_fast_reorg = 1.
4. Add index for an arbitrary table.

2. What did you expect to see? (Required)

No error.

3. What did you see instead (Required)

DDL hangs.

[2023/07/19 09:36:45.117 +08:00] [INFO] [ddl_worker.go:981] ["run DDL job"] [worker="worker 2, tp add index"] [category=ddl] [job="ID:150, Type:add index, State:running, SchemaState:none, SchemaID:2, TableID:148, RowCount:0, ArgLen:0, start time: 2023-07-19 09:36:39.884 +0800 CST, Err:[ddl:-1]cannot get disk capacity at /tmp/tidb/tmp_ddl-4000: no such file or directory, ErrCount:5, SnapshotVersion:0, UniqueWarnings:0"]
[2023/07/19 09:36:45.118 +08:00] [INFO] [index.go:620] ["run add index job"] [category=ddl] [job="ID:150, Type:add index, State:running, SchemaState:none, SchemaID:2, TableID:148, RowCount:0, ArgLen:6, start time: 2023-07-19 09:36:39.884 +0800 CST, Err:[ddl:-1]cannot get disk capacity at /tmp/tidb/tmp_ddl-4000: no such file or directory, ErrCount:5, SnapshotVersion:0, UniqueWarnings:0"] [indexInfo="{\"id\":1,\"idx_name\":{\"O\":\"idx\",\"L\":\"idx\"},\"tbl_name\":{\"O\":\"\",\"L\":\"\"},\"idx_cols\":[{\"name\":{\"O\":\"k\",\"L\":\"k\"},\"offset\":2,\"length\":-1}],\"state\":0,\"backfill_state\":0,\"comment\":\"\",\"index_type\":1,\"is_unique\":false,\"is_primary\":false,\"is_invisible\":false,\"is_global\":false,\"mv_index\":false}"]
[2023/07/19 09:36:45.118 +08:00] [INFO] [backend_mgr.go:78] ["ingest backfill is not available"] [category=ddl-ingest] [error="cannot get disk capacity at /tmp/tidb/tmp_ddl-4000: no such file or directory"]
[2023/07/19 09:36:45.118 +08:00] [WARN] [ddl_worker.go:943] ["run DDL job error"] [worker="worker 2, tp add index"] [category=ddl] [error="cannot get disk capacity at /tmp/tidb/tmp_ddl-4000: no such file or directory"]
[2023/07/19 09:36:45.124 +08:00] [INFO] [ddl_worker.go:826] ["run DDL job failed, sleeps a while then retries it."] [worker="worker 2, tp add index"] [category=ddl] [waitTime=1s] [error="cannot get disk capacity at /tmp/tidb/tmp_ddl-4000: no such file or directory"]
[2023/07/19 09:36:46.124 +08:00] [INFO] [ddl_worker.go:1191] ["schema version doesn't change"] [category=ddl]

4. What is your TiDB version? (Required)

17cda10