Re: [RFC 01/16] blkcg:Introduce blkio.app_identifier knob to blkio controller

Tejun Heo
2020-08-05T20:12:17Z

Hello,

On Wed, Aug 05, 2020 at 08:33:19AM +0200, Hannes Reinecke wrote:
> None of these are guaranteed to be either present or unique.
> It's not uncommon to have VMs with more than one MAC address, and any other
> unique identifier like system UUID is not required to be present.

I have a really hard time seeing how this fits into block cgroup interface.
The last time we did something similar (tagging from cgroup interface side)
was for netcls and it ended poorly. There are basic problems with e.g.
delegation as these things are at odds with everything else sharing the
interface.

My not-too-well informed suggestions are either building mapping somewhere
in the stack or at least implement the interface where it fits better so
that people who don't need app_identifier don't see them and preferably can
disable them. I don't mind cgroup data structs carrying extra bits for stuff
which want to make use of the cgroup tree but I'm a pretty firm nack on the
proposed interface.

Thanks.

--
tejun