storvsc: add logging for error/warning messages

BugLink: http://bugs.launchpad.net/bugs/1583357

Introduce a logging level for storvsc to log certain error/warning
messages. Those messages are helpful in some environments,
e.g. Microsoft Azure, for customer support and troubleshooting purposes.
Signed-off-by: Long Li <longli@microsoft.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
(cherry picked from commit f8aea701)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/scsi/storvsc_drv.c

@@ -164,6 +164,26 @@ static int sense_buffer_size = PRE_WIN8_STORVSC_SENSE_BUFFER_SIZE;
 */
 static int vmstor_proto_version;
 
+#define STORVSC_LOGGING_NONE	0
+#define STORVSC_LOGGING_ERROR	1
+#define STORVSC_LOGGING_WARN	2
+
+static int logging_level = STORVSC_LOGGING_ERROR;
+module_param(logging_level, int, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(logging_level,
+	"Logging level, 0 - None, 1 - Error (default), 2 - Warning.");
+
+static inline bool do_logging(int level)
+{
+	return logging_level >= level;
+}
+
+#define storvsc_log(dev, level, fmt, ...)			\
+do {								\
+	if (do_logging(level))					\
+		dev_warn(&(dev)->device, fmt, ##__VA_ARGS__);	\
+} while (0)
+
 struct vmscsi_win8_extension {
 	/*
 	 * The following were added in Windows 8
@@ -942,7 +962,8 @@ static void storvsc_command_completion(struct storvsc_cmd_request *cmd_request)
 
 	if (scmnd->result) {
 		if (scsi_normalize_sense(scmnd->sense_buffer,
-				SCSI_SENSE_BUFFERSIZE, &sense_hdr))
+				SCSI_SENSE_BUFFERSIZE, &sense_hdr) &&
+		    do_logging(STORVSC_LOGGING_ERROR))
 			scsi_print_sense_hdr(scmnd->device, "storvsc",
 					     &sense_hdr);
 	}
@@ -996,6 +1017,13 @@ static void storvsc_on_io_completion(struct hv_device *device,
 	stor_pkt->vm_srb.sense_info_length =
 	vstor_packet->vm_srb.sense_info_length;
 
+	if (vstor_packet->vm_srb.scsi_status != 0 ||
+	    vstor_packet->vm_srb.srb_status != SRB_STATUS_SUCCESS)
+		storvsc_log(device, STORVSC_LOGGING_WARN,
+			"cmd 0x%x scsi status 0x%x srb status 0x%x\n",
+			stor_pkt->vm_srb.cdb[0],
+			vstor_packet->vm_srb.scsi_status,
+			vstor_packet->vm_srb.srb_status);
 
 	if ((vstor_packet->vm_srb.scsi_status & 0xFF) == 0x02) {
 		/* CHECK_CONDITION */
@@ -1003,6 +1031,10 @@ static void storvsc_on_io_completion(struct hv_device *device,
 			SRB_STATUS_AUTOSENSE_VALID) {
 			/* autosense data available */
 
+			storvsc_log(device, STORVSC_LOGGING_WARN,
+				"stor pkt %p autosense data valid - len %d\n",
+				request, vstor_packet->vm_srb.sense_info_length);
+
 			memcpy(request->cmd->sense_buffer,
 			       vstor_packet->vm_srb.sense_data,
 			       vstor_packet->vm_srb.sense_info_length);