OpenCloudOS-Kernel/drivers/scsi/ibmvscsi
Brian King 764907293e scsi: ibmvfc: Set default timeout to avoid crash during migration
While testing live partition mobility, we have observed occasional crashes
of the Linux partition. What we've seen is that during the live migration,
for specific configurations with large amounts of memory, slow network
links, and workloads that are changing memory a lot, the partition can end
up being suspended for 30 seconds or longer. This resulted in the following
scenario:

CPU 0                          CPU 1
-------------------------------  ----------------------------------
scsi_queue_rq                    migration_store
 -> blk_mq_start_request          -> rtas_ibm_suspend_me
  -> blk_add_timer                 -> on_each_cpu(rtas_percpu_suspend_me
              _______________________________________V
             |
             V
    -> IPI from CPU 1
     -> rtas_percpu_suspend_me
                                     -> __rtas_suspend_last_cpu

-- Linux partition suspended for > 30 seconds --
                                      -> for_each_online_cpu(cpu)
                                           plpar_hcall_norets(H_PROD
 -> scsi_dispatch_cmd
                                      -> scsi_times_out
                                       -> scsi_abort_command
                                        -> queue_delayed_work
  -> ibmvfc_queuecommand_lck
   -> ibmvfc_send_event
    -> ibmvfc_send_crq
     - returns H_CLOSED
   <- returns SCSI_MLQUEUE_HOST_BUSY
-> __blk_mq_requeue_request

                                      -> scmd_eh_abort_handler
                                       -> scsi_try_to_abort_cmd
                                         - returns SUCCESS
                                       -> scsi_queue_insert

Normally, the SCMD_STATE_COMPLETE bit would protect against the command
completion and the timeout, but that doesn't work here, since we don't
check that at all in the SCSI_MLQUEUE_HOST_BUSY path.

In this case we end up calling scsi_queue_insert on a request that has
already been queued, or possibly even freed, and we crash.

The patch below simply increases the default I/O timeout to avoid this race
condition. This is also the timeout value that nearly all IBM SAN storage
recommends setting as the default value.

Link: https://lore.kernel.org/r/1610463998-19791-1-git-send-email-brking@linux.vnet.ibm.com
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
2021-01-14 22:02:59 -05:00
..
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
ibmvfc.c scsi: ibmvfc: Set default timeout to avoid crash during migration 2021-01-14 22:02:59 -05:00
ibmvfc.h scsi: ibmvfc: Add new fields for version 2 of several MADs 2020-11-19 22:09:11 -05:00
ibmvscsi.c scsi: ibmvscsi: Fix potential race after loss of transport 2020-10-26 17:14:40 -04:00
ibmvscsi.h SCSI misc on 20190709 2019-07-11 15:14:01 -07:00