[LU-16478] faulty MDT connection can leak a reference to export

• Status: Resolved
• Project: Lustre
• Fix Version/s: Lustre 2.16.0
• Type: Bug
• Priority: Minor
• Reporter: Alex Zhuravlev
• Assignee: Alex Zhuravlev
• Resolution: Fixed
• Severity: 3

Description

if target_handle_connect() races with an export eviction then the following scenario can happen:

• mdt_obd_reconnect() -> .. nodemap_add_member() grabs a reference to the export
• then target_handle_connect() finds the export invalide and exits with -ENODEV:

  	if (export->exp_disconnected) {
  		spin_unlock(&export->exp_lock);
  		GOTO(out, rc = -ENODEV);
  

  after umount won't be able to complete with the following symptoms:

  00000020:02000400:1.0:1673726953.882508:0:8583:0:(genops.c:1792:obd_exports_barrier()) lustre-MDT0000 is waiting for obd_unlinked_exports more than 7 seconds. The obd refcount = 4. Is it stuck?
  00000020:02000400:1.0:1673726953.889142:0:8583:0:(genops.c:1758:print_export_data()) lustre-MDT0000: UNLINKED 000000002760c5c2 5a4bd497-6ace-43e0-8e46-c6b0e7dc84ba 0@lo 1 (0 0 0) 1 0 1 0: 00000000e9920e55  4294967301 stale:0
  

Issue Links

• is related to: LU-11388 replay-single test_131b: test timeout

Comments

[Gerrit Updater]

"Alex Zhuravlev <[e-mail]>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/49642
Subject: LU-16478 ldlm: don't reconnect disconnected exports
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 03a4fee9aa9d4a4430655becd796622d79343363

[Gerrit Updater]

"Alex Zhuravlev <[e-mail]>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/50041
Subject: LU-16478 tests: a reproducer
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 95c65f97cdc9cc28935518a3f5d755d4bc416d56

[Gerrit Updater]

"Oleg Drokin <[e-mail]>" merged in patch https://review.whamcloud.com/c/fs/lustre-release/+/50041/
Subject: LU-16478 target: disconnected export
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 654d5f3fa4df2a0f7275a6da0f050a18881f4f75

[Peter Jones]

Landed for 2.16