linux-kernel - Re: [PATCH v2 1/3] scsi: iscsi: Add helper functions to manage iscsi_cls

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Message-ID: <d7a0405f-f0df-1db0-e95e-562db1ef064f@huawei.com>
Date:   Wed, 9 Mar 2022 19:01:12 +0800
From:   Wenchao Hao <haowenchao@...wei.com>
To:     Mike Christie <michael.christie@...cle.com>,
        Lee Duncan <lduncan@...e.com>, Chris Leech <cleech@...hat.com>,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        <open-iscsi@...glegroups.com>, <linux-scsi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Wu Bo <wubo40@...wei.com>, Zhiqiang Liu <liuzhiqiang26@...wei.com>,
        <linfeilong@...wei.com>
Subject: Re: [PATCH v2 1/3] scsi: iscsi: Add helper functions to manage
 iscsi_cls_conn

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@...wei.com>
>> Signed-off-by: Wu Bo <wubo40@...wei.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.
> 

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.
> 
>