[PATCH 0/5] xen-netback: Fine-tuning for three function implementations

From: Markus Elfring <redacted>
Date: Sat, 2 Jan 2016 18:46:45 +0100

A few update suggestions were taken into account
from static source code analysis.

Markus Elfring (5):
  Delete an unnecessary assignment in connect_rings()
  Delete an unnecessary goto statement in connect_rings()
  Replace a variable initialisation by an assignment in read_xenbus_vif_flags()
  Replace a variable initialisation by an assignment in xen_register_watchers()
  Delete an unnecessary variable initialisation in xen_register_watchers()

 drivers/net/xen-netback/xenbus.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

-- 
2.6.3

From: Markus Elfring <redacted>
Date: Sat, 2 Jan 2016 17:32:40 +0100

Remove the assignment for a local variable because its value is not
changed compared to the one from a previous function call.

Signed-off-by: Markus Elfring <redacted>
---
 drivers/net/xen-netback/xenbus.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 56ebd82..7f2895d 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c

@@ -941,7 +941,6 @@ static int connect_rings(struct backend_info *be, struct xenvif_queue *queue)
 		goto err;
 	}
 
-	err = 0;
 err: /* Regular return falls through with err == 0 */
 	kfree(xspath);
 	return err;

-- 
2.6.3

From: Markus Elfring <redacted>
Date: Sat, 2 Jan 2016 17:50:21 +0100

One goto statement referred to a source code position directly behind it.
Thus omit such an unnecessary jump.

Signed-off-by: Markus Elfring <redacted>
---
 drivers/net/xen-netback/xenbus.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 7f2895d..d4947e1 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c

@@ -933,13 +933,11 @@ static int connect_rings(struct backend_info *be, struct xenvif_queue *queue)
 	/* Map the shared frame, irq etc. */
 	err = xenvif_connect(queue, tx_ring_ref, rx_ring_ref,
 			     tx_evtchn, rx_evtchn);
-	if (err) {
+	if (err)
 		xenbus_dev_fatal(dev, err,
 				 "mapping shared-frames %lu/%lu port tx %u rx %u",
 				 tx_ring_ref, rx_ring_ref,
 				 tx_evtchn, rx_evtchn);
-		goto err;
-	}
 
 err: /* Regular return falls through with err == 0 */
 	kfree(xspath);

-- 
2.6.3

From: Markus Elfring <redacted>
Date: Sat, 2 Jan 2016 18:01:57 +0100

Replace an explicit initialisation for one local variable at the beginning
by an assignment.

Signed-off-by: Markus Elfring <redacted>
---
 drivers/net/xen-netback/xenbus.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index d4947e1..aff963f 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c

@@ -946,7 +946,7 @@ err: /* Regular return falls through with err == 0 */
 
 static int read_xenbus_vif_flags(struct backend_info *be)
 {
-	struct xenvif *vif = be->vif;
+	struct xenvif *vif;
 	struct xenbus_device *dev = be->dev;
 	unsigned int rx_copy;
 	int err, val;

@@ -968,13 +968,14 @@ static int read_xenbus_vif_flags(struct backend_info *be)
 	if (xenbus_scanf(XBT_NIL, dev->otherend,
 			 "feature-rx-notify", "%d", &val) < 0)
 		val = 0;
+	vif = be->vif;
 	if (!val) {
 		/* - Reduce drain timeout to poll more frequently for
 		 *   Rx requests.
 		 * - Disable Rx stall detection.
 		 */
-		be->vif->drain_timeout = msecs_to_jiffies(30);
-		be->vif->stall_timeout = 0;
+		vif->drain_timeout = msecs_to_jiffies(30);
+		vif->stall_timeout = 0;
 	}
 
 	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg",

-- 
2.6.3

From: Markus Elfring <redacted>
Date: Sat, 2 Jan 2016 18:23:16 +0100

Replace an explicit initialisation for one local variable at the beginning
by an assignment.

Signed-off-by: Markus Elfring <redacted>
---
 drivers/net/xen-netback/xenbus.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index aff963f..e8dfc3d 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c

@@ -687,11 +687,12 @@ static int xen_register_watchers(struct xenbus_device *dev, struct xenvif *vif)
 {
 	int err = 0;
 	char *node;
-	unsigned maxlen = strlen(dev->nodename) + sizeof("/rate");
+	unsigned maxlen;
 
 	if (vif->credit_watch.node)
 		return -EADDRINUSE;
 
+	maxlen = strlen(dev->nodename) + sizeof("/rate");
 	node = kmalloc(maxlen, GFP_KERNEL);
 	if (!node)
 		return -ENOMEM;

-- 
2.6.3

From: Markus Elfring <redacted>
Date: Sat, 2 Jan 2016 18:28:26 +0100

Omit explicit initialisation at the beginning for one local variable
that is redefined before its first use.

Signed-off-by: Markus Elfring <redacted>
---
 drivers/net/xen-netback/xenbus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index e8dfc3d..55f0735 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c

@@ -685,7 +685,7 @@ static void xen_net_rate_changed(struct xenbus_watch *watch,
 
 static int xen_register_watchers(struct xenbus_device *dev, struct xenvif *vif)
 {
-	int err = 0;
+	int err;
 	char *node;
 	unsigned maxlen;
 

-- 
2.6.3

On Sat, 2016-01-02 at 18:50 +0100, SF Markus Elfring wrote:

A few update suggestions were taken into account
from static source code analysis.

While static analysis can be useful, I don't think these
specific conversions are generally useful.

Perhaps it would be more useful to convert the string
duplication or snprintf logic to kstrdup/kasprintf

This:

	if (num_queues == 1) {
		xspath = kzalloc(strlen(dev->otherend) + 1, GFP_KERNEL);
		if (!xspath) {
			xenbus_dev_fatal(dev, -ENOMEM,
					 "reading ring references");
			return -ENOMEM;
		}
		strcpy(xspath, dev->otherend);
	} else {
		xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
		xspath = kzalloc(xspathsize, GFP_KERNEL);
		if (!xspath) {
			xenbus_dev_fatal(dev, -ENOMEM,
					 "reading ring references");
			return -ENOMEM;
		}
		snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend,
			 queue->id);
	}

could be simplified to something like:

	if (num_queues == 1)
		xspath = kstrdup(dev->otherend, GFP_KERNEL);
	else
		xspath = kasprintf(GFP_KERNEL, "%s/queue-%u",
				   dev->otherend, queue->id);
	if (!xspath)
		etc...

The original code is fine.

regards,
dan carpenter

I think the original code is fine.

Wei.