Re: [bug report] blktests srp/013 lead kernel panic with latest block/for-next and 5.13.15

[Bart Van Assche <bvanassche@acm.org>]

On 9/27/21 10:10 PM, Yi Zhang wrote:
> Hi Bart
> 
> Bisect shows this issue was introduced from bellow commit, btw, this is always reproduced on the s390x kvm environment:
> 
> commit 65ca846a53149a1a72cd8d02e7b2e73dd545b834
> Author: Bart Van Assche <bvanassche@acm.org <mailto:bvanassche@acm.org>>
> Date:   Wed Jan 22 19:56:34 2020 -0800
> 
>      scsi: core: Introduce {init,exit}_cmd_priv()
> 
>      The current behavior of the SCSI core is to clear driver-private data
>      before preparing a request for submission to the SCSI LLD. Make it possible
>      for SCSI LLDs to disable clearing of driver-private data.
> 
>      These hooks will be used by a later patch, namely "scsi: ufs: Let the SCSI
>      core allocate per-command UFS data".
> 
> (gdb) l *(scsi_mq_exit_request+0x2c)
> 0x8d7be4 is in scsi_mq_exit_request (drivers/scsi/scsi_lib.c:1780).
> 1775 unsigned int hctx_idx)
> 1776 {
> 1777 struct Scsi_Host *shost = set->driver_data;
> 1778 struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
> 1779
> 1780 if (shost->hostt->exit_cmd_priv)
> 1781 shost->hostt->exit_cmd_priv(shost, cmd);
> 1782 kmem_cache_free(scsi_sense_cache, cmd->sense_buffer);
> 1783 }
> 1784

Hi Yi,

Thank you for having taken the time to run a bisect. However, I strongly doubt
that the bisection result is correct. If there would be anything wrong with the
above patch it would already have been noticed on other architectures. I
recommend to proceed as follows:
* Verify whether the reported issue only occurs with the stable kernel series or
   also with mainline kernels.
* Work with the soft-iWARP author to improve the reliability of the siw driver.
   If I run blktests in an x86 VM then the following appears sporadically in
   the kernel log:

------------[ cut here ]------------
WARNING: CPU: 18 PID: 5462 at drivers/infiniband/sw/siw/siw_cm.c:255 __siw_cep_dealloc+0x184/0x190 [siw]
CPU: 1 PID: 5462 Comm: kworker/u144:13 Tainted: G            E     5.15.0-rc2-dbg+ #7
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Workqueue: iw_cm_wq cm_work_handler [iw_cm]
RIP: 0010:__siw_cep_dealloc+0x184/0x190 [siw]
Call Trace:
  siw_cep_put+0x5c/0x80 [siw]
  siw_reject+0x13c/0x230 [siw]
  iw_cm_reject+0xac/0x130 [iw_cm]
  cm_conn_req_handler+0x4f1/0x7d0 [iw_cm]
  cm_work_handler+0x885/0x9c0 [iw_cm]
  process_one_work+0x535/0xad0
  worker_thread+0x2e7/0x700
  kthread+0x1f6/0x220
  ret_from_fork+0x1f/0x30
irq event stamp: 11449266
hardirqs last  enabled at (11449265): [<ffffffff81fc4248>] _raw_spin_unlock_irq+0x28/0x50
hardirqs last disabled at (11449266): [<ffffffff81fb7e44>] __schedule+0x5f4/0xbb0
softirqs last  enabled at (11449176): [<ffffffffa06d142f>] p_fill_from_dev_buffer+0xff/0x140 [scsi_debug]
softirqs last disabled at (11449168): [<ffffffffa06d1400>] p_fill_from_dev_buffer+0xd0/0x140 [scsi_debug]
---[ end trace b23871487c995b72 ]---

* Use the rdma_rxe driver to run blktests since at least in my experience that
   driver is more reliable than the soft-iWARP driver.

Thanks,

Bart.