On Mon, Mar 30, 2020 at 11:17 PM Christian Brauner <christian.brauner@xxxxxxxxxx> wrote: > Fwiw, putting down my kernel hat and speaking as someone who maintains > two container runtimes and various other low-level bits and pieces in > userspace who'd make heavy use of this stuff I would prefer the fd-based > fsinfo() approach especially in the light of across namespace > operations, querying all properties of a mount atomically all-at-once, fsinfo(2) doesn't meet the atomically all-at-once requirement. Sure, it's possible to check the various change counters before and after a batch of calls to check that the result is consistent. Still, that's not an atomic all-at-once query, if you'd really require that, than fsinfo(2) as it currently stands would be inadequate. > and safe delegation through fds. Another heavy user of this would be > systemd (Cced Lennart who I've discussed this with) which would prefer > the fd-based approach as well. I think pulling this into a filesystem > and making userspace parse around in a filesystem tree to query mount > information is the wrong approach and will get messy pretty quickly > especially in the face of mount and user namespace interactions and > various other pitfalls. Have you actually looked at my proposed patch? Do you have concrete issues or just vague bad feelings? Thanks, Miklos
