netdevsim: move max vf config to dev

max_vfs is a strange little beast because the file
hangs off of nsim's debugfs, but it configures a field
in the bus device. Move it to dev.c, let's look at it
as if the device driver was imposing VF limit based
on FW info (like pci_sriov_set_totalvfs()).

Again, when moving refactor the function not to hold
the vfs lock pointlessly while parsing the input.
Wrap the access from the read side in READ_ONCE()
to appease concurrency checkers. Do not check if
return value from snprintf() is negative...

Signed-off-by: Jakub Kicinski <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/netdevsim/bus.c

···
 	__ATTR(sriov_numvfs, 0664, nsim_bus_dev_numvfs_show,
 	       nsim_bus_dev_numvfs_store);
 
-ssize_t nsim_bus_dev_max_vfs_read(struct file *file,
-				  char __user *data,
-				  size_t count, loff_t *ppos)
-{
-	struct nsim_dev *nsim_dev = file->private_data;
-	struct nsim_bus_dev *nsim_bus_dev = nsim_dev->nsim_bus_dev;
-	char buf[11];
-	ssize_t len;
-
-	len = snprintf(buf, sizeof(buf), "%u\n", nsim_bus_dev->max_vfs);
-	if (len < 0)
-		return len;
-
-	return simple_read_from_buffer(data, count, ppos, buf, len);
-}
-
-ssize_t nsim_bus_dev_max_vfs_write(struct file *file,
-				   const char __user *data,
-				   size_t count, loff_t *ppos)
-{
-	struct nsim_dev *nsim_dev = file->private_data;
-	struct nsim_bus_dev *nsim_bus_dev = nsim_dev->nsim_bus_dev;
-	struct nsim_vf_config *vfconfigs;
-	ssize_t ret;
-	char buf[10];
-	u32 val;
-
-	if (*ppos != 0)
-		return 0;
-
-	if (count >= sizeof(buf))
-		return -ENOSPC;
-
-	mutex_lock(&nsim_dev->vfs_lock);
-	/* Reject if VFs are configured */
-	if (nsim_bus_dev->num_vfs) {
-		ret = -EBUSY;
-		goto unlock;
-	}
-
-	ret = copy_from_user(buf, data, count);
-	if (ret) {
-		ret = -EFAULT;
-		goto unlock;
-	}
-
-	buf[count] = '\0';
-	ret = kstrtouint(buf, 10, &val);
-	if (ret) {
-		ret = -EIO;
-		goto unlock;
-	}
-
-	/* max_vfs limited by the maximum number of provided port indexes */
-	if (val > NSIM_DEV_VF_PORT_INDEX_MAX - NSIM_DEV_VF_PORT_INDEX_BASE) {
-		ret = -ERANGE;
-		goto unlock;
-	}
-
-	vfconfigs = kcalloc(val, sizeof(struct nsim_vf_config), GFP_KERNEL | __GFP_NOWARN);
-	if (!vfconfigs) {
-		ret = -ENOMEM;
-		goto unlock;
-	}
-
-	kfree(nsim_dev->vfconfigs);
-	nsim_dev->vfconfigs = vfconfigs;
-	nsim_bus_dev->max_vfs = val;
-	*ppos += count;
-	ret = count;
-unlock:
-	mutex_unlock(&nsim_dev->vfs_lock);
-	return ret;
-}
-
 static ssize_t
 new_port_store(struct device *dev, struct device_attribute *attr,
 	       const char *buf, size_t count)

drivers/net/netdevsim/dev.c

···
 	.owner = THIS_MODULE,
 };
 
+static ssize_t nsim_bus_dev_max_vfs_read(struct file *file, char __user *data,
+					 size_t count, loff_t *ppos)
+{
+	struct nsim_dev *nsim_dev = file->private_data;
+	char buf[11];
+	ssize_t len;
+
+	len = scnprintf(buf, sizeof(buf), "%u\n",
+			READ_ONCE(nsim_dev->nsim_bus_dev->max_vfs));
+
+	return simple_read_from_buffer(data, count, ppos, buf, len);
+}
+
+static ssize_t nsim_bus_dev_max_vfs_write(struct file *file,
+					  const char __user *data,
+					  size_t count, loff_t *ppos)
+{
+	struct nsim_vf_config *vfconfigs;
+	struct nsim_dev *nsim_dev;
+	char buf[10];
+	ssize_t ret;
+	u32 val;
+
+	if (*ppos != 0)
+		return 0;
+
+	if (count >= sizeof(buf))
+		return -ENOSPC;
+
+	ret = copy_from_user(buf, data, count);
+	if (ret)
+		return -EFAULT;
+	buf[count] = '\0';
+
+	ret = kstrtouint(buf, 10, &val);
+	if (ret)
+		return -EINVAL;
+
+	/* max_vfs limited by the maximum number of provided port indexes */
+	if (val > NSIM_DEV_VF_PORT_INDEX_MAX - NSIM_DEV_VF_PORT_INDEX_BASE)
+		return -ERANGE;
+
+	vfconfigs = kcalloc(val, sizeof(struct nsim_vf_config),
+			    GFP_KERNEL | __GFP_NOWARN);
+	if (!vfconfigs)
+		return -ENOMEM;
+
+	nsim_dev = file->private_data;
+	mutex_lock(&nsim_dev->vfs_lock);
+	/* Reject if VFs are configured */
+	if (nsim_dev_get_vfs(nsim_dev)) {
+		ret = -EBUSY;
+	} else {
+		swap(nsim_dev->vfconfigs, vfconfigs);
+		WRITE_ONCE(nsim_dev->nsim_bus_dev->max_vfs, val);
+		*ppos += count;
+		ret = count;
+	}
+	mutex_unlock(&nsim_dev->vfs_lock);
+
+	kfree(vfconfigs);
+	return ret;
+}
+
 static const struct file_operations nsim_dev_max_vfs_fops = {
 	.open = simple_open,
 	.read = nsim_bus_dev_max_vfs_read,

drivers/net/netdevsim/netdevsim.h

···
 u64 nsim_fib_get_val(struct nsim_fib_data *fib_data,
 		     enum nsim_resource_id res_id, bool max);
 
-ssize_t nsim_bus_dev_max_vfs_read(struct file *file,
-				  char __user *data,
-				  size_t count, loff_t *ppos);
-ssize_t nsim_bus_dev_max_vfs_write(struct file *file,
-				   const char __user *data,
-				   size_t count, loff_t *ppos);
-
 static inline bool nsim_dev_port_is_pf(struct nsim_dev_port *nsim_dev_port)
 {
 	return nsim_dev_port->port_type == NSIM_DEV_PORT_TYPE_PF;