[LU-17165] recovery-small test_141: mgc lost locks

• Type: Bug
• Resolution: Unresolved
• Priority: Minor
• Fix Version/s: Lustre 2.17.0
• Affects Version/s: Lustre 2.16.0
• Labels: failover mtg
• Severity: 3
• Assignee: Core Lustre Triage
• Reporter: Maloo

Description

This issue was created by maloo for S Buisson <[e-mail]>

This issue relates to the following test suite run: https://testing.whamcloud.com/test_sets/c7030573-01fa-4889-ae5f-64824986f779

test_141 failed with the following error:

mgc lost locks (12 != 4)

Test session details:
clients: https://build.whamcloud.com/job/lustre-reviews/99081 - 4.18.0-477.21.1.el8_8.x86_64
servers: https://build.whamcloud.com/job/lustre-reviews/99081 - 4.18.0-477.21.1.el8_lustre.x86_64

VVVVVVV DO NOT REMOVE LINES BELOW, Added by Maloo for auto-association VVVVVVV
recovery-small test_141 - mgc lost locks (12 != 4)

Issue Links

• is related to: LU-13316 frequent "Connection restored" messages without any prior errors/indicators

Comments

[Andreas Dilger]

The majority of failure cases are (confusingly) either "oldc 0 != newc 23" or "oldc 23 != newc 0". This makes me think that the delay between "cancel_lru_locks MGC" and "do_facet ost1 ... lock_count" is racy and they randomly get "23" or "0" and sometimes they match (either both "0" or both "23") and sometimes they don't.

It isn't clear to me why the DLM locks are cancelled before being read on the OST before it is restarted? If that is to check that the client is refreshing its locks, then it would make sense for there to be some gap (e.g. 3-5s) so that the client will refresh the MGC locks again before they are counted. Then afterward it should use wait_update() until there are the same number of locks before considering the test a failure.

[Jian Yu]

Lustre 2.16.0 RC5: https://testing.whamcloud.com/test_sets/631b2da4-fd5d-41b6-ab19-f1838b9c4ac5

[Jian Yu]

The failure occurred consistently in failover-part-1 test sessions.

[Sebastien Buisson]

From the recent test failures, it looks like the MGC lock count is pretty erratic. Sometimes the lock count before MGS restart is greater than after MGS restart, sometimes it is the other way around. And sometimes the MGC lock count before the MGS restart is even 0, which is a bit surprising for a running Lustre file system.
See the error message printed in this test results page:
https://testing.whamcloud.com/search?status%5B%5D=FAIL&test_set_script_id=f36cabd0-32c3-11e0-a61c-52540025f9ae&sub_test_script_id=be891259-db0f-49c1-bd23-eafc220a3fc8&start_date=2024-09-27&end_date=2024-10-03&source=sub_tests#redirect

I initially introduced recovery-small test_141, but it does not seem the problem is in the test itself. Unfortunately I am not an ldlm lock specialist.

[Jian Yu]

+1 on master branch: https://testing.whamcloud.com/test_sets/91343880-9495-40dd-b77f-895ac8f90176

[Andreas Dilger]

This is still failing regularly:

https://testing.whamcloud.com/search?horizon=2332800&status%5B%5D=FAIL&test_set_script_id=f36cabd0-32c3-11e0-a61c-52540025f9ae&sub_test_script_id=be891259-db0f-49c1-bd23-eafc220a3fc8&source=sub_tests#redirect

[Peter Jones]

Merged for 2.16

[Gerrit Updater]

"Oleg Drokin <[e-mail]>" merged in patch https://review.whamcloud.com/c/fs/lustre-release/+/55591/
Subject: LU-17165 tests: fix recovery-small test_141
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 755c9c0f78a777b342a42a74aa8fb93d04e7cad8

[Gerrit Updater]

"Sebastien Buisson <[e-mail]>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/55591
Subject: LU-17165 tests: fix recovery-small test_141
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: c7b45f61bda6d8efed4ec7ccda79e2d11aad823d

[Andreas Dilger]

This test was added in patch https://review.whamcloud.com/37344 "LU-13116 mgc: do not lose sptlrpc config lock". It isn't clear if there is a real problem or if there is some unrelated MGC lock that is being canceled during the test?