kernel BUG at ../drivers/md/bcache/bset.c:884

This document (000020355) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server for SAP 15 SP2

Situation

This issue was noticed when using bcache  for cache acceleration of SAP HANA data disks. 
The following was seen in /var/log/messages: 
 
xy1d kernel: [721646.767939] ------------[ cut here ]------------ 
xy1d kernel: [721646.767942] kernel BUG at ../drivers/md/bcache/bset.c:884! 
xy1d kernel: [721646.767950] invalid opcode: 0000 [#1] SMP NOPTI
xy1d kernel: [721646.767962] CPU: 309 PID: 217475 Comm: SubmitThread-DA Tainted: G             L X    5.3.18-24.52-default #1 SLE15-SP2
xy1d kernel: [721646.767966] Hardware name: Inspur TS860M5/YZCP-00916-101, BIOS 4.1.16 09/10/2020
xy1d kernel: [721646.767989] RIP: 0010:bch_btree_insert_key+0x28c/0x2b0 [bcache]

In addition SAP HANA hung during shutdown process. 
Currently it was only seen on the hardware mentioned above. Other hardware may be affected, too.

Resolution

Kindly contact SUSE Technical Support and refer to this Knowledge Base article to get a Program Temporary Fix (PTF). 
Once these fixes are released  as a Maintenance Update this TID will be updated.
Issue is already fixed in SLES15 SP3. The systemd unit mentioned below is still recommended until further notice.

Status

Reported to Engineering

Additional Information

There may be situations where SAP HANA hangs during system shutdown when using bcache.
This is caused by a race condition where the bcache device vanishes before the cache is written back completely. This leads to cache corruption and bcache needs to be reinitialized before next usage.
Upstream bug pending.

To mitigate SUSE Technical Support can provide a systemd unit to stop bcache safely before reboot. This  can also be shared upon request. 

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:000020355
  • Creation Date: 05-Aug-2021
  • Modified Date:05-Aug-2021
    • SUSE Linux Enterprise Server for SAP Applications

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