zfcp: decouple our scsi_eh callbacks from scsi_cmnd

Note: zfcp_scsi_eh_host_reset_handler() will be converted in a later patch.

zfcp_scsi_eh_device_reset_handler() now only depends on scsi_device. zfcp_scsi_eh_target_reset_handler() now only depends on scsi_target. All derive other objects from these intended callback arguments.

zfcp_scsi_eh_target_reset_handler() is special: The FCP channel requires a valid LUN handle so we try to find ourselves a stand-in scsi_device as suggested by Hannes Reinecke. If it cannot find a stand-in scsi device, trace a record like the following (formatted with zfcpdbf from s390-tools):

Timestamp : ...
Area : SCSI
Subarea : 00
Level : 1
Exception : -
CPU ID : ..
Caller : 0x...
Record ID : 1
Tag : tr_nosd target reset, no SCSI device
Request ID : 0x0000000000000000 none (invalid)
SCSI ID : 0x00000000 SCSI ID/target denoting scope
SCSI LUN : 0xffffffff none (invalid)
SCSI LUN high : 0xffffffff none (invalid)
SCSI result : 0x00002003 field re-used for midlayer value: FAILED
SCSI retries : 0xff none (invalid)
SCSI allowed : 0xff none (invalid)
SCSI scribble : 0xffffffffffffffff none (invalid)
SCSI opcode : ffffffff ffffffff ffffffff ffffffff none (invalid)
FCP rsp inf cod: 0xff none (invalid)
FCP rsp IU : 00000000 00000000 00000000 00000000 none (invalid)

                 00000000 00000000

Actually change the signature of zfcp_task_mgmt_function() used by zfcp_scsi_eh_device_reset_handler() & zfcp_scsi_eh_target_reset_handler(). Since it was prepared in a previous patch, we only need to delete a local auto variable which is now the intended argument.

---

Notes:
Changes since RFC:

Since the FCP channel always requires a valid LUN handle, we now use scsi_device as context data with any TMF instead of zfcp_port for FCP_TMF_TGT_RESET and an optional scsi_device for FCP_TMF_LUN_RESET.

zfcp_scsi_eh_target_reset_handler() became more involved as it needs to find a stand-in scsi_device within the target scope as suggested by Hannes.
Trace if we could not find a stand-in scsi_device along with an example trace in the commit description.
Put the refcount from shost_for_each_device for the stand-in scsi_device.

NB:
zfcp_scsi_eh_host_reset_handler() will be converted in a later patch. I need more time to resolve the proper sync with all fc_rports states with support for FAST_IO_FAIL.

 drivers/s390/scsi/zfcp_scsi.c | 41 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 4 deletions(-)

index e0c5735cf3db..fcc832b73960 100644
@@ -265,9 +265,14 @@ static void zfcp_scsi_forget_cmnds(struct zfcp_scsi_dev *zsdev, u8 tm_flags)
 	write_unlock_irqrestore(&adapter->abort_lock, flags);
 }
 
-static int zfcp_task_mgmt_function(struct scsi_cmnd *scpnt, u8 tm_flags)
+/**
+ * zfcp_task_mgmt_function() - Synchronously send a task management function.
+ * @sdev: Pointer to SCSI device to send the task management command to.
+ * @tm_flags: Task management flags,
+ *	      here we only handle %FCP_TMF_TGT_RESET or %FCP_TMF_LUN_RESET.
+ */
+static int zfcp_task_mgmt_function(struct scsi_device *sdev, u8 tm_flags)
 {
-	struct scsi_device *sdev = scpnt->device;
 	struct zfcp_scsi_dev *zfcp_sdev = sdev_to_zfcp(sdev);
 	struct zfcp_adapter *adapter = zfcp_sdev->port->adapter;
 	struct fc_rport *rport = starget_to_rport(scsi_target(sdev));

@@ -315,12 +320,40 @@ static int zfcp_task_mgmt_function(struct scsi_cmnd *scpnt, u8 tm_flags)
 
 static int zfcp_scsi_eh_device_reset_handler(struct scsi_cmnd *scpnt)
 {
-	return zfcp_task_mgmt_function(scpnt, FCP_TMF_LUN_RESET);
+	struct scsi_device *sdev = scpnt->device;
+
+	return zfcp_task_mgmt_function(sdev, FCP_TMF_LUN_RESET);
 }
 
 static int zfcp_scsi_eh_target_reset_handler(struct scsi_cmnd *scpnt)
 {
-	return zfcp_task_mgmt_function(scpnt, FCP_TMF_TGT_RESET);
+	struct scsi_target *starget = scsi_target(scpnt->device);
+	struct fc_rport *rport = starget_to_rport(starget);
+	struct Scsi_Host *shost = rport_to_shost(rport);
+	struct scsi_device *sdev = NULL, *tmp_sdev;
+	struct zfcp_adapter *adapter =
+		(struct zfcp_adapter *)shost->hostdata[0];
+	int ret;
+
+	shost_for_each_device(tmp_sdev, shost) {
+		if (tmp_sdev->id == starget->id) {
+			sdev = tmp_sdev;
+			break;
+		}
+	}
+	if (!sdev) {
+		ret = FAILED;
+		zfcp_dbf_scsi_eh("tr_nosd", adapter, starget->id, ret);
+		return ret;
+	}
+
+	ret = zfcp_task_mgmt_function(sdev, FCP_TMF_TGT_RESET);
+
+	/* release reference from above shost_for_each_device */
+	if (sdev)
+		scsi_device_put(tmp_sdev);
+
+	return ret;
 }
 
 static int zfcp_scsi_eh_host_reset_handler(struct scsi_cmnd *scpnt)

2.16.3