netdev - Re: [PATCH 4/4] bnx2i: Add bnx2i iSCSI driver.

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Date:	Tue, 19 May 2009 13:47:19 -0700
From:	"Michael Chan" <mchan@...adcom.com>
To:	"Mike Christie" <michaelc@...wisc.edu>
cc:	"open-iscsi@...glegroups.com" <open-iscsi@...glegroups.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"James.Bottomley@...senPartnership.com" 
	<James.Bottomley@...senPartnership.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"Karen Xie" <kxie@...lsio.com>,
	"Anil Veerabhadrappa" <anilgv@...adcom.com>,
	"Benjamin Li" <benli@...adcom.com>
Subject: Re: [PATCH 4/4] bnx2i: Add bnx2i iSCSI driver.


On Tue, 2009-05-19 at 07:22 -0700, Mike Christie wrote:
> Michael Chan wrote:
> > 
> > Here are the more generic NETLINK_ISCSI messages and the iscsi transport
> > code to support them, please review.
> > 
> > diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
> > index d69a53a..60cb6cb 100644
> > --- a/drivers/scsi/scsi_transport_iscsi.c
> > +++ b/drivers/scsi/scsi_transport_iscsi.c
> > @@ -995,6 +995,39 @@ int iscsi_recv_pdu(struct iscsi_cls_conn *conn, struct iscsi_hdr *hdr,
> >  }
> >  EXPORT_SYMBOL_GPL(iscsi_recv_pdu);
> >  
> > +int iscsi_offload_mesg(struct Scsi_Host *shost,
> > +		       struct iscsi_transport *transport, uint32_t type,
> > +		       char *data, uint16_t data_size)
> > +{
> > +	struct nlmsghdr	*nlh;
> > +	struct sk_buff *skb;
> > +	struct iscsi_uevent *ev;
> > +	int len = NLMSG_SPACE(sizeof(*ev) + data_size);
> > +
> > +	skb = alloc_skb(len, GFP_ATOMIC);
> > +	if (!skb) {
> > +		printk(KERN_ERR "can not deliver iscsi offload message:OOM\n");
> > +		return -ENOMEM;
> > +	}
> > +
> > +	nlh = __nlmsg_put(skb, 0, 0, 0, (len - sizeof(*nlh)), 0);
> > +	ev = NLMSG_DATA(nlh);
> > +	memset(ev, 0, sizeof(*ev));
> > +	ev->type = type;
> > +	ev->transport_handle = iscsi_handle(transport);
> > +	switch (type) {
> > +	case ISCSI_KEVENT_PATH_REQ:
> > +		ev->r.req_path.host_no = shost->host_no;
> > +	case ISCSI_KEVENT_IF_DOWN:
> > +		ev->r.notify_if_down.host_no = shost->host_no;
> > +	}
> > +
> > +	memcpy((char*)ev + sizeof(*ev), data, data_size);
> > +
> > +	return iscsi_broadcast_skb(skb, GFP_KERNEL);
> 
> 
> You can sync up what the gfp flag used here and for the alloc_skb call 
> above. If you have process context, you probably want to use GFP_NOIO, 
> because this could be called for reconnect for a disk in use.
> 
> If you do not have process context then you would need to use GFP_ATOMIC.
> 
> 

We have process context, but I think we should make it more general for
other future drivers and use GFP_ATOMIC.

> > +}
> > +EXPORT_SYMBOL_GPL(iscsi_offload_mesg);
> > +
> >  void iscsi_conn_error_event(struct iscsi_cls_conn *conn, enum iscsi_err error)
> >  {
> >  	struct nlmsghdr	*nlh;
> > @@ -1393,6 +1426,30 @@ iscsi_set_host_param(struct iscsi_transport *transport,
> >  }
> >  
> >  static int
> > +iscsi_set_path(struct iscsi_transport *transport, struct iscsi_uevent *ev)
> > +{
> > +	struct Scsi_Host *shost;
> > +	struct iscsi_path *params;
> > +	int err;
> > +
> > +	if (!transport->set_path)
> > +		return -ENOSYS;
> > +
> > +	shost = scsi_host_lookup(ev->u.set_path.host_no);
> > +	if (!shost) {
> > +		printk(KERN_ERR "set path could not find host no %u\n",
> > +		       ev->u.set_path.host_no);
> > +		return -ENODEV;
> > +	}
> > +
> > +	params = (struct iscsi_path *)((char*)ev + sizeof(*ev));
> > +	err = transport->set_path(shost, params);
> > +				      
> > +	scsi_host_put(shost);
> > +	return err;
> > +}
> > +
> > +static int
> >  iscsi_if_recv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> >  {
> >  	int err = 0;
> > @@ -1411,7 +1468,8 @@ iscsi_if_recv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
> >  	if (!try_module_get(transport->owner))
> >  		return -EINVAL;
> >  
> > -	priv->daemon_pid = NETLINK_CREDS(skb)->pid;
> > +	if (nlh->nlmsg_type != ISCSI_UEVENT_PATH_UPDATE)
> > +		priv->daemon_pid = NETLINK_CREDS(skb)->pid;
> >  
> 
> Instead of using broadcast above and in some other places and then doing 
> this check, could we just use multicast groups or something else? The 
> events from iscsid could be in one group and then events for uip would 
> be in another?

We need to do this check because we don't want the daemon_pid to be
overwritten with a pid that is not iscsid's.  If it was overwritten,
unicast NETLINK_ISCSI messages will not reach iscsid.

We can use multicast group 2 for the new messages if you prefer.  This
way, I think iscsid will not receive the new messages since it is only
listening on group 1.  The pid check will still be needed though.

> 
> Or is it more common to do it like this or will it break compat with 
> other tools if we change it?
> 


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