Re: [Lsf-pc] [LSF/MM TOPIC] Unifying the LIO and SCST target drivers

[Bart Van Assche <bart.vanassche@sandisk.com>]

On 03/05/15 19:39, Andy Grover wrote:
> On 03/05/2015 08:06 AM, Bart Van Assche wrote:
>> If we would do what Nic proposed - modify SCST such that it uses
>> configfs instead of sysfs - then that would result in the removal of at
>> least one SCST feature that is important to its users, namely automatic
>> population of the configuration filesystem with hardware target port
>> information. Apparently Nic does not want to convert LIO from configfs
>> to sysfs.
> 
> Clearly configfs is here to stay, but is there anything that says LIO 
> couldn't have both? Besides the issue at hand, there are some other bits 
> of useful info in LIO that aren't available because of configfs' 
> limitations, but that would be possible via sysfs.

(resending my reply since apparently my previous e-mail didn't make it
to the lists)

Hello Andy,

Let's have a look at FC HBAs. Most FC HBAs have a PCIe connector and
support NPIV. If an NPIV WWN is configured then that WWN is passed from
user space to the kernel. The PCIe specification supports hot-plugging.
Although I'm not sure there exist FC HBAs that support hot-plugging,
upon hot removal of a PCIe HBA the kernel is notified of this and must
remove all NPIV WWNs from the filesystem that is used to configure the
SCSI target subsystem. Since it is not allowed to remove configfs
directories from inside the kernel I think NPIV is an example of a use
case that cannot be handled properly when using configfs for configuring
a SCSI target subsystem, even when combined in some way with sysfs.

Bart.