Re: [PATCH 5/5] kernfs: add exportfs operations

[Christoph Hellwig]

On Tue, May 23, 2017 at 02:57:11PM -0400, Tejun Heo wrote:
> 
> Yeah, this is one of the repeatedly requested features - a cgroup id
> which can be looked up in a scalable way.  We probably should have
> added this earlier too as we already have places where we're passing
> in full cgroup path into the kernel (ipt_cgroup match).

I still have no idea how this ties into export ops.  Currently I don't
see any tracing code using export operations, so maybe a big part of
the series is missing/

> IIUC, Shaohua is adding it so that block tracing can be made aware of
> cgroups but something like this is necessary whenever we try to refer
> to a cgroup in a race-free / scalable way.

You can already get i_ino using statx, and i_generation using
FS_IOC_GETVERSION, so I'm a little lost on why you need the full
exportfs infrastructure.