| Message ID | 1610463998-19791-1-git-send-email-brking@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | ibmvfc: Set default timeout to avoid crash during migration | expand |
On Tue, 12 Jan 2021 09:06:38 -0600, Brian King wrote: > 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: > > [...] Applied to 5.11/scsi-fixes, thanks! [1/1] ibmvfc: Set default timeout to avoid crash during migration https://git.kernel.org/mkp/scsi/c/764907293edc -- Martin K. Petersen Oracle Linux Engineering
diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c index 42e4d35..79badaa 100644 --- a/drivers/scsi/ibmvscsi/ibmvfc.c +++ b/drivers/scsi/ibmvscsi/ibmvfc.c @@ -3007,8 +3007,10 @@ static int ibmvfc_slave_configure(struct scsi_device *sdev) unsigned long flags = 0; spin_lock_irqsave(shost->host_lock, flags); - if (sdev->type == TYPE_DISK) + if (sdev->type == TYPE_DISK) { sdev->allow_restart = 1; + blk_queue_rq_timeout(sdev->request_queue, 120 * HZ); + } spin_unlock_irqrestore(shost->host_lock, flags); return 0; }
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. Signed-off-by: Brian King <brking@linux.vnet.ibm.com> --- drivers/scsi/ibmvscsi/ibmvfc.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)