On Wed, Jan 14, 2026 at 10:42:48PM -0800, Christoph Hellwig wrote: > On Wed, Jan 14, 2026 at 04:20:13PM +0100, Christian Brauner wrote: > > > You're still think of it the wrong way. If we do have file systems > > > that break the original exportfs semantics we need to fix that, and > > > something like a "stable handles" flag will work well for that. But > > > a totally arbitrary "is exportable" flag is total nonsense. > > > > File handles can legitimately be conceptualized independently of > > exporting a filesystem. If we wanted to tear those concepts apart > > implementation wise we could. > > > > It is complete nonsense to expect the kernel to support exporting any > > arbitrary internal filesystem or to not support file handles at all. > > You are going even further down the path of entirely missing the point > (or the two points by now).
You're arguing for the sake of arguing imho. You're getting exactly what we're all saying as evidenced by the last paragraph in your mail: it is entirely what this whole thing is about. > If a file systems meets all technical requirements of being nfsd > exportable and the users asks for it, it is not our job to make an > arbitrary policy decision to say no. This is an entirely irrelevant point because we're talking about cgroupfs, nsfs, and pidfs. And they don't meet this criteria. cgroupfs is a _local resource management filesystem_ why would we ever want to support exporting it over the network. It allows to break the local delegation model as I've explained. cgroupfs shows _local processes_. So a server will see completely nonsensical PID identifiers listed in cgroup files and it can fsck around with processes in a remote system. Hard NAK. Entirely irrelevant if that filesystem meets the theoretical standards. > If it does not meet the technical requirements it obviously should > not be exportable. And it seems like the spread of file handles > beyond nfs exporting created some ambiguity here, which we need to > fix. We are all in agreement here.
