[S390] ccwreq: add ability to use all paths

Change the ccwrequest infrastructure to use more than one channel
path per start I/O. A flag "singlepath" is added to struct
ccw_request - if set, the old behavior is used. This flag is set
for all exploiters of the ccwrequest infrastructure - so there
is no functional change through this patch.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/ccwreq.c

@@ -38,9 +38,13 @@ static u16 ccwreq_next_path(struct ccw_device *cdev)
 {
 	struct ccw_request *req = &cdev->private->req;
 
+	if (!req->singlepath) {
+		req->mask = 0;
+		goto out;
+	}
 	req->retries	= req->maxretries;
 	req->mask	= lpm_adjust(req->mask >>= 1, req->lpm);
-
+out:
 	return req->mask;
 }
 
@@ -113,8 +117,12 @@ void ccw_request_start(struct ccw_device *cdev)
 {
 	struct ccw_request *req = &cdev->private->req;
 
-	/* Try all paths twice to counter link flapping. */
-	req->mask	= 0x8080;
+	if (req->singlepath) {
+		/* Try all paths twice to counter link flapping. */
+		req->mask = 0x8080;
+	} else
+		req->mask = req->lpm;
+
 	req->retries	= req->maxretries;
 	req->mask	= lpm_adjust(req->mask, req->lpm);
 	req->drc	= 0;

drivers/s390/cio/device_id.c

@@ -216,6 +216,7 @@ void ccw_device_sense_id_start(struct ccw_device *cdev)
 	req->timeout	= SENSE_ID_TIMEOUT;
 	req->maxretries	= SENSE_ID_RETRIES;
 	req->lpm	= sch->schib.pmcw.pam & sch->opm;
+	req->singlepath	= 1;
 	req->check	= snsid_check;
 	req->callback	= snsid_callback;
 	ccw_request_start(cdev);

drivers/s390/cio/device_pgid.c

@@ -208,6 +208,7 @@ static void spid_start(struct ccw_device *cdev)
 	req->timeout	= PGID_TIMEOUT;
 	req->maxretries	= PGID_RETRIES;
 	req->lpm	= 0x80;
+	req->singlepath	= 1;
 	req->callback	= spid_callback;
 	spid_do(cdev);
 }
@@ -420,6 +421,7 @@ static void verify_start(struct ccw_device *cdev)
 	req->timeout	= PGID_TIMEOUT;
 	req->maxretries	= PGID_RETRIES;
 	req->lpm	= 0x80;
+	req->singlepath	= 1;
 	if (cdev->private->flags.pgroup) {
 		CIO_TRACE_EVENT(4, "snid");
 		CIO_HEX_EVENT(4, devid, sizeof(*devid));
@@ -507,6 +509,7 @@ void ccw_device_disband_start(struct ccw_device *cdev)
 	req->timeout	= PGID_TIMEOUT;
 	req->maxretries	= PGID_RETRIES;
 	req->lpm	= sch->schib.pmcw.pam & sch->opm;
+	req->singlepath	= 1;
 	req->callback	= disband_callback;
 	fn = SPID_FUNC_DISBAND;
 	if (cdev->private->flags.mpath)
@@ -560,6 +563,7 @@ void ccw_device_stlck_start(struct ccw_device *cdev, void *data, void *buf1,
 	req->timeout	= PGID_TIMEOUT;
 	req->maxretries	= PGID_RETRIES;
 	req->lpm	= sch->schib.pmcw.pam & sch->opm;
+	req->singlepath	= 1;
 	req->data	= data;
 	req->callback	= stlck_callback;
 	stlck_build_cp(cdev, buf1, buf2);

drivers/s390/cio/io_sch.h

@@ -92,11 +92,12 @@ enum io_status {
  * @filter: optional callback to adjust request status based on IRB data
  * @callback: final callback
  * @data: user-defined pointer passed to all callbacks
+ * @singlepath: if set, use only one path from @lpm per start I/O
+ * @cancel: non-zero if request was cancelled
+ * @done: non-zero if request was finished
  * @mask: current path mask
  * @retries: current number of retries
  * @drc: delayed return code
- * @cancel: non-zero if request was cancelled
- * @done: non-zero if request was finished
  */
 struct ccw_request {
 	struct ccw1 *cp;
@@ -108,12 +109,13 @@ struct ccw_request {
 				 enum io_status);
 	void (*callback)(struct ccw_device *, void *, int);
 	void *data;
+	unsigned int singlepath:1;
 	/* These fields are used internally. */
+	unsigned int cancel:1;
+	unsigned int done:1;
 	u16 mask;
 	u16 retries;
 	int drc;
-	int cancel:1;
-	int done:1;
 } __attribute__((packed));
 
 /*