On Fri, Jun 07, 2019 at 12:36:36PM +0200, Jan Kara wrote: > Because the pins would be invisible to sysadmin from that point on.
It is not invisible, it just shows up in a rdma specific kernel interface. You have to use rdma netlink to see the kernel object holding this pin. If this visibility is the main sticking point I suggest just enhancing the existing MR reporting to include the file info for current GUP pins and teaching lsof to collect information from there as well so it is easy to use. If the ownership of the lease transfers to the MR, and we report that ownership to userspace in a way lsof can find, then I think all the concerns that have been raised are met, right? > ugly to live so we have to come up with something better. The best I can > currently come up with is to have a method associated with the lease that > would invalidate the RDMA context that holds the pins in the same way that > a file close would do it. This is back to requiring all RDMA HW to have some new behavior they currently don't have.. The main objection to the current ODP & DAX solution is that very little HW can actually implement it, having the alternative still require HW support doesn't seem like progress. I think we will eventually start seein some HW be able to do this invalidation, but it won't be universal, and I'd rather leave it optional, for recovery from truely catastrophic errors (ie my DAX is on fire, I need to unplug it). Jason
