Re: [PATCH v2 1/3] scsi: iscsi: Add helper functions to manage iscsi_cls_conn

[Wenchao Hao]

On 2022/3/9 1:19, Mike Christie wrote:
> On 3/8/22 9:09 PM, Wenchao Hao wrote:
> > iscsi_alloc_conn(): alloc and initialize iscsi_cls_conn
> > iscsi_add_conn(): expose iscsi_cls_conn to userspace's via sysfs.
> > iscsi_remove_conn(): remove iscsi_cls_conn from sysfs
> > iscsi_free_conn(): free iscsi_cls_conn
> >
> > Signed-off-by: Wenchao Hao <haowenchao@xxxxxxxxxx>
> > Signed-off-by: Wu Bo <wubo40@xxxxxxxxxx>
> > ---
> >   drivers/scsi/scsi_transport_iscsi.c | 107 ++++++++++++++++++++++++++++
> >   include/scsi/scsi_transport_iscsi.h |   5 ++
> >   2 files changed, 112 insertions(+)
> >
> > diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
> > index 554b6f784223..8e97c6f88359 100644
> > --- a/drivers/scsi/scsi_transport_iscsi.c
> > +++ b/drivers/scsi/scsi_transport_iscsi.c
> > @@ -2340,6 +2340,113 @@ void iscsi_free_session(struct iscsi_cls_session *session)
> >   }
> >   EXPORT_SYMBOL_GPL(iscsi_free_session);
> >   
> > +/**
> > + * iscsi_alloc_conn - alloc iscsi class connection
> > + * @session: iscsi cls session
> > + * @dd_size: private driver data size
> > + * @cid: connection id
> > + *
> > + * This can be called from a LLD or iscsi_transport. The connection
> > + * is child of the session so cid must be unique for all connections
> > + * on the session.
> > + *
> > + * Since we do not support MCS, cid will normally be zero. In some cases
> > + * for software iscsi we could be trying to preallocate a connection struct
> > + * in which case there could be two connection structs and cid would be
> > + * non-zero.
>
> Is that with the upstream iscsi tools or your version? I don't think the comment
> is needed or is needed somewhere else.
>
> If this happens then they will have the same sysfs/device name so when we do the
> device_add it will spit an error about duplicate names.
>
>
> > + */
> > +struct iscsi_cls_conn *
> > +iscsi_alloc_conn(struct iscsi_cls_session *session, int dd_size, uint32_t cid)
> > +{
> > +	struct iscsi_transport *transport = session->transport;
> > +	struct iscsi_cls_conn *conn;
> > +
> > +	conn = kzalloc(sizeof(*conn) + dd_size, GFP_KERNEL);
> > +	if (!conn)
> > +		return NULL;
> > +	if (dd_size)
> > +		conn->dd_data = &conn[1];
> > +
> > +	mutex_init(&conn->ep_mutex);
> > +	INIT_LIST_HEAD(&conn->conn_list);
> > +	INIT_WORK(&conn->cleanup_work, iscsi_cleanup_conn_work_fn);
> > +	conn->transport = transport;
> > +	conn->cid = cid;
> > +	conn->state = ISCSI_CONN_DOWN;
> > +
> > +	/* this is released in the dev's release function */
> > +	if (!get_device(&session->dev))
> > +		goto free_conn;
> > +
> > +	dev_set_name(&conn->dev, "connection%d:%u", session->sid, cid);
> > +	device_initialize(&conn->dev);
> > +	conn->dev.parent = &session->dev;
> > +	conn->dev.release = iscsi_conn_release;
> > +
> > +	return conn;
> > +
> > +free_conn:
> > +	kfree(conn);
> > +	return NULL;
> > +}
> > +EXPORT_SYMBOL_GPL(iscsi_alloc_conn);
> > +
> > +/**
> > + * iscsi_add_conn - add iscsi class connection
> > + * @conn: iscsi cls connection
> > + *
> > + * this would expose iscsi_cls_conn to sysfs, so make sure the related
> > + * resources when access sysfs attributes are initialized before calling this.
> > + */
> > +int iscsi_add_conn(struct iscsi_cls_conn *conn)
> > +{
> > +	int err;
> > +	unsigned long flags;
> > +	struct iscsi_cls_session *session = iscsi_dev_to_session(conn->dev.parent);
> > +
> > +	err = device_add(&conn->dev);
> > +	if (err) {
> > +		iscsi_cls_session_printk(KERN_ERR, session,
> > +					 "could not register connection's dev\n");
> > +		put_device(&session->dev);
>
> I would call iscsi_free_conn. instead of put_device.

Sorry I noticed it but forget to remove it. Here should not call 
put_device() or iscsi_free_conn(). If iscsi_add_conn() failed, we shoule 
not call any put operation which might cause resource free.

> > +		return err;
> > +	}
> > +	err = transport_register_device(&conn->dev);
> > +	if (err) {
> > +		iscsi_cls_session_printk(KERN_ERR, session,
> > +					 "could not register transport's dev\n");
> > +		device_del(&conn->dev);
> > +		put_device(&session->dev);
>
>
> Is for the get_device(&session->dev) in iscsi_alloc_conn? If so you don't need to
> do it because when the last put is done on the conn->dev, it will call
> iscsi_conn_release which does the put on the session when it does "put_device(parent).
>
> Or did you mean to call put_device on the conn->dev?

As above, we shouldn't call put_device() here.

> I would do device_el(&conn->dev) then do a goto free_conn at the bottom which
> does iscsi_free_conn. The place above should do the goto as well.