[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>

1 files changed, 11 insertions, 3 deletions

diff --git a/drivers/s390/cio/ccwreq.c b/drivers/s390/cio/ccwreq.c
index fd03687..d15f8b4 100644
--- a/drivers/s390/cio/ccwreq.c
+++ b/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;