On 02/12/2016 11:54 AM, James Bottomley wrote: > On Fri, 2016-02-12 at 09:38 -0800, Lee Duncan wrote: >> The scsi_transport_iscsi module already uses the ida_simple >> routines for managing the target ID, if requested to do >> so. This change replaces an ever-increasing atomic integer >> that tracks the session ID itself with the ida_simple >> family of routines. This means that the session ID >> will be reclaimed and can be reused when the session >> is freed. > > Is reusing session ID's really a good idea? I think it is if we do it by the iscsi rfc. We have two issues. 1. For iSCSI's iSID we need a 24 bit id. The iSID + initiator name is the SCSI initiator port ID, so targets want the iSID to be reused for things like persistent reservation tracking. There are a couple red hat bugzillas. I am not sure if they are open though. Here is a KB https://access.redhat.com/solutions/66861 for more info. We have been lazy and did not implement this and were just reusing part of the session->sid. 2. For the kobject/sysfs name we want a unique name/id. Linux boxes stay up a long time and some users login and logout of sessions a lot. We roll over and have collisions. Lee's patch was only meant to fix this. The reuse part was not meant to fix #1, and so it does not handle every case like you suspect. To fix everything how about this: - Use Lee's patch to fix #2. We do not need the iSID to match the sysfs name. Userspace does not do any type of iSCSI iSID <-> kernel session id matching. - For #1, in the userespace node db code we can implement some iSID allocation/management code that follows the spec. We can also add a blacklist there in case we find broken targets. -- 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
