[LU-17283] sles12.5 always crashes at client unmount

• Type: Bug
• Resolution: Unresolved
• Priority: Critical
• Fix Version/s: Lustre 2.16.0
• Affects Version/s: Lustre 2.16.0
• Severity: 3
• Assignee: WC Triage
• Reporter: Maloo

Description

This issue was created by maloo for Andreas Dilger <[e-mail]>

This issue relates to the following test suite run:
https://testing.whamcloud.com/test_sets/f43b22b1-5c6c-444b-b9be-ecfe70a1c164

Test session details:
clients: https://build.whamcloud.com/job/lustre-master/4475 - 4.12.14-122.133-default
servers: https://build.whamcloud.com/job/lustre-master/4475 - 4.18.0-477.27.1.el8_lustre.x86_64

It looks like the sles12.5 client is crashing 100% of test runs on master right at unmount:

 2025.506089] Lustre: Unmounted lustre-client
[ 2025.507805] BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
[ 2025.509455] IP: wb_workfn+0x2b/0x450
[ 2025.511544] CPU: 0 PID: 282 Comm: kworker/u4:3 Tainted: G           OE      4.12.14-122.133-default #1 SLE12-SP5
[ 2025.513428] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[ 2025.514554] Workqueue: writeback wb_workfn
[ 2025.516554] RIP: 0010:wb_workfn+0x2b/0x450
[ 2025.529303] Call Trace:
[ 2025.532599]  process_one_work+0x14c/0x390
[ 2025.533464]  worker_thread+0x1c3/0x3e0
[ 2025.534241]  kthread+0xf6/0x130

It looks like some kind of workqueue that is not flushed before unmount, or maybe RCU related?

This is commit v2_15_58-183-g21295b169b (2 commits before 2.15.59).