unistore: check directio support before unistore boot

[YangKeao]

Signed-off-by: YangKeao yangkeao@chunibyo.icu

What problem does this PR solve?

Issue Number: close #39237

Problem Summary:

Unistore cannot work on a path, which doesn't support directio. TiDB should refuse to work on a tmpfs (or other fs which doesn't support directio).

What is changed and how it works?

Add a check to verify whether the target path supports directio before starting the unistore

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Start the tidb with unistore on a machine whose /tmp is a tmpfs, it will give an error and stop:

[2022/11/18 15:50:28.625 +08:00] [FATAL] [terror.go:300] ["unexpected error"] [error="open /tmp/tidb/direct-io-test: invalid argument"] [stack="github.com/pingcap/tidb/parser/terror.MustNil\n\t/home/yangkeao/Project/github.com/YangKeao/tidb/parser/terror/terror.go:300\nmain.createStoreAndDomain\n\t/home/yangkeao/Project/github.com/YangKeao/tidb/tidb-server/main.go:306\nmain.main\n\t/home/yangkeao/Project/github.com/YangKeao/tidb/tidb-server/main.go:211\nruntime.main\n\t/usr/lib/golang/src/runtime/proc.go:250"] [stack="github.com/pingcap/tidb/parser/terror.MustNil\n\t/home/yangkeao/Project/github.com/YangKeao/tidb/parser/terror/terror.go:300\nmain.createStoreAndDomain\n\t/home/yangkeao/Project/github.com/YangKeao/tidb/tidb-server/main.go:306\nmain.main\n\t/home/yangkeao/Project/github.com/YangKeao/tidb/tidb-server/main.go:211\nruntime.main\n\t/usr/lib/golang/src/runtime/proc.go:250"]

Release note

Fix the issue that the unistore will start but deadlock on a file system without directio support by throwing errors.

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• Defined2014
• xhebox

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[xhebox]

@YangKeao need to complete the issue triage

[YangKeao]

I'll update the implementation of badger to work around the directio, so close this pull request.