On 08/10/2016 06:30 PM, Steffen Maier wrote:
> On a successful end of reopen port forced,
> zfcp_erp_strategy_followup_success() re-uses the port erp_action
> and the subsequent zfcp_erp_action_cleanup() now
> sees ZFCP_ERP_SUCCEEDED with
> erp_action->action==ZFCP_ERP_ACTION_REOPEN_PORT
> instead of ZFCP_ERP_ACTION_REOPEN_PORT_FORCED
> but must not perform zfcp_scsi_schedule_rport_register().
>
> We can detect this because the fresh port reopen erp_action
> is in its very first step ZFCP_ERP_STEP_UNINITIALIZED.
>
> Otherwise this opens a time window with unblocked rport
> (until the followup port reopen recovery would block it again).
> If a scsi_cmnd timeout occurs during this time window
> fc_timed_out() cannot work as desired and such command
> would indeed time out and trigger scsi_eh. This prevents
> a clean and timely path failover.
> This should not happen if the path issue can be recovered
> on FC transport layer such as path issues involving RSCNs.
>
> Also, unnecessary and repeated DID_IMM_RETRY for pending and
> undesired new requests occur because internally zfcp still
> has its zfcp_port blocked.
>
> As follow-on errors with scsi_eh, it can cause,
> in the worst case, permanently lost paths due to one of:
> sd <scsidev>: [<scsidisk>] Medium access timeout failure. Offlining disk!
> sd <scsidev>: Device offlined - not ready after error recovery
>
> For fix validation and to aid future debugging with other recoveries
> we now also trace (un)blocking of rports.
>
> Signed-off-by: Steffen Maier <maier@xxxxxxxxxxxxxxxxxx>
> Fixes: 5767620c383a ("[SCSI] zfcp: Do not unblock rport from REOPEN_PORT_FORCED")
> Fixes: a2fa0aede07c ("[SCSI] zfcp: Block FC transport rports early on errors")
> Fixes: 5f852be9e11d ("[SCSI] zfcp: Fix deadlock between zfcp ERP and SCSI")
> Fixes: 338151e06608 ("[SCSI] zfcp: make use of fc_remote_port_delete when target port is unavailable")
> Fixes: 3859f6a248cb ("[PATCH] zfcp: add rports to enable scsi_add_device to work again")
> Cc: <stable@xxxxxxxxxxxxxxx> #2.6.32+
> Reviewed-by: Benjamin Block <bblock@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/s390/scsi/zfcp_dbf.h | 7 ++++++-
> drivers/s390/scsi/zfcp_erp.c | 12 +++++++++---
> drivers/s390/scsi/zfcp_scsi.c | 8 +++++++-
> 3 files changed, 22 insertions(+), 5 deletions(-)
>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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