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Message-ID: <8183661b-a513-9b04-b289-3707704084b2@oracle.com>
Date:   Tue, 8 Mar 2022 11:19:27 -0600
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Subject: Re: [PATCH v2 1/3] scsi: iscsi: Add helper functions to manage
 iscsi_cls_conn
Content-Language: en-US
To:     Wenchao Hao <haowenchao@huawei.com>, Lee Duncan <lduncan@suse.com>,
        Chris Leech <cleech@redhat.com>,
        "James E . J . Bottomley" <jejb@linux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@oracle.com>,
        open-iscsi@googlegroups.com, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     Wu Bo <wubo40@huawei.com>, Zhiqiang Liu <liuzhiqiang26@huawei.com>,
        linfeilong@huawei.com
References: <20220309030916.2932316-1-haowenchao@huawei.com>
 <20220309030916.2932316-2-haowenchao@huawei.com>
From:   Mike Christie <michael.christie@oracle.com>
In-Reply-To: <20220309030916.2932316-2-haowenchao@huawei.com>
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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@huawei.com>
> Signed-off-by: Wu Bo <wubo40@huawei.com>
> ---
>  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.

> +		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?

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.


> +		return err;
> +	}
> +
> +	spin_lock_irqsave(&connlock, flags);
> +	list_add(&conn->conn_list, &connlist);
> +	spin_unlock_irqrestore(&connlock, flags);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(iscsi_add_conn);
> +
> +/**
> + * iscsi_remove_conn - remove iscsi class connection from sysfs
> + * @conn: iscsi cls connection
> + *
> + * this would remove iscsi_cls_conn from sysfs, and wait for previous
> + * read/write of iscsi_cls_conn's attributes in sysfs finishing
> + */
> +void iscsi_remove_conn(struct iscsi_cls_conn *conn)
> +{
> +	device_del(&conn->dev);

This should have the guts of iscsi_destroy_conn which reverses what
the iscsi_add_conn did:

        spin_lock_irqsave(&connlock, flags);
        list_del(&conn->conn_list);
        spin_unlock_irqrestore(&connlock, flags);

        transport_unregister_device(&conn->dev);

	device_del(&conn->dev).

You can then kill iscsi_destroy_conn.


> +}
> +EXPORT_SYMBOL_GPL(iscsi_remove_conn);
> +
> +void iscsi_free_conn(struct iscsi_cls_conn *conn)
> +{
> +	put_device(&conn->dev);
> +}
> +EXPORT_SYMBOL_GPL(iscsi_free_conn);

Sorry I made a mistake with this suggestion. Kill this and just have
the user do iscsi_put_conn.


> +
>  /**
>   * iscsi_create_conn - create iscsi class connection
>   * @session: iscsi cls session
> diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h
> index c5d7810fd792..346f65bc3861 100644
> --- a/include/scsi/scsi_transport_iscsi.h
> +++ b/include/scsi/scsi_transport_iscsi.h
> @@ -441,6 +441,11 @@ extern struct iscsi_cls_session *iscsi_create_session(struct Scsi_Host *shost,
>  						unsigned int target_id);
>  extern void iscsi_remove_session(struct iscsi_cls_session *session);
>  extern void iscsi_free_session(struct iscsi_cls_session *session);
> +extern struct iscsi_cls_conn *iscsi_alloc_conn(struct iscsi_cls_session *sess,
> +						int dd_size, uint32_t cid);
> +extern int iscsi_add_conn(struct iscsi_cls_conn *conn);
> +extern void iscsi_remove_conn(struct iscsi_cls_conn *conn);
> +extern void iscsi_free_conn(struct iscsi_cls_conn *conn);
>  extern struct iscsi_cls_conn *iscsi_create_conn(struct iscsi_cls_session *sess,
>  						int dd_size, uint32_t cid);
>  extern void iscsi_put_conn(struct iscsi_cls_conn *conn);