Re: [PATCH 3/4] qla2xxx: Add DebugFS node for target sess list.

[Giridhar Malavali <giridhar.malavali@qlogic.com>]

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On 2/5/16, 12:00 PM, "Bart Van Assche" <bart.vanassche@sandisk.com> wrote:

>On 02/05/2016 09:26 AM, Himanshu Madhani wrote:
>> On 2/4/16, 10:16 AM, "Bart Van Assche" <bart.vanassche@sandisk.com>
>>wrote:
>>> On 02/04/2016 08:45 AM, Himanshu Madhani wrote:
>>>> From: Quinn Tran <quinn.tran@qlogic.com>
>>>>
>>>>    #cat  /sys/kernel/debug/qla2xxx/qla2xxx_31/tgt_sess
>>>>    qla2xxx_31
>>>>    Port ID   Port Name                Handle
>>>>    ff:fc:01  21:fd:00:05:33:c7:ec:16  0
>>>>    01:0e:00  21:00:00:24:ff:7b:8a:e4  1
>>>>    01:0f:00  21:00:00:24:ff:7b:8a:e5  2
>>>>    ....
>>>
>>> Hello Quinn and Himanshu,
>>>
>>> The above information is not only useful to people who are debugging
>>>the
>>> QLogic target driver but also to end users who want to check which
>>> initiator ports have already logged in to a target port. Hence my
>>> proposal to move this information from debugfs to another location
>>>(e.g.
>>> configfs or sysfs). Users of other target drivers are probably also
>>> interested in seeing which sessions are active. How about adding the
>>> functionality for reporting session information per target port in the
>>> LIO core in such a way that some attributes are available for all
>>>target
>>> drivers (e.g. initiator port name, SCSI command statistics) and such
>>> that target drivers can define additional attributes to exported for
>>> each session (e.g. port ID, handle, ...).
>>
>> We had initially implemented this as a sysfs hook, but knowing that
>>sysfs
>> is not encouraged, we decided to put this information via debugfs.
>>Would it
>> make more sense if we send a sysfs patch?
>
>Hello Himanshu,
>
>Let's try to reach agreement about the approach first before starting to
>rework this patch.
>
>Five years ago I explained in a message that I posted on the linux-scsi
>mailing list why LIO should use sysfs to export information that changes
>dynamically (see also http://thread.gmane.org/gmane.linux.scsi/65615/).
>I think this patch shows that there is a real need to have detailed
>session information from LIO target drivers in user space. We need one
>directory per session instead of exporting all session information
>through a single file. sysfs is the right filesystem to export such
>information because configfs directories should be created by the user
>and not from inside the kernel. If no agreement can be reached about
>this over e-mail my proposal is to discuss this further at the 2016
>LSF/MM summit.

Bart, 

I see lot of target customers requesting for such information and having
something that can be created inside kernel space will be helpful. Let us
discuss further at 2016 LSF/MM summit.

‹ Giri



>
>Thanks,
>
>Bart.


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