On Fri, 2015-03-06 at 08:25 +0100, Bart Van Assche wrote: > 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. Not exactly. configfs in this context works similar to hotplug remove of a FC HBA in initiator mode (or a USB drive even) with a mounted filesystem on one of the LUNs. That is, a kobject reference is obtained on Scsi_Host->shost_gendev at /sys/kernel/config/target/qla2xxx_npiv/$NPIV_WWPN/ creation time, preventing the final device_release() from being called until the last reference is dropped via rmdir ../target/qla2xxx_npiv/$NPIV_WWPN/. The practical method is to use a udev script called at hotplug remove time (similar to USB) to drop the NPIV configfs groups associated with device(s) being removed, allowing the underlying kernel data structures to be released. --nab -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
