On Thu, Dec 19, 2019 at 2:35 AM Christian Brauner <christian.brauner@xxxxxxxxxx> wrote: > I guess this is the remaining question we should settle, i.e. what do we > prefer. > I still think that adding a new syscall for this seems a bit rich. On > the other hand it seems that a lot more people agree that using a > dedicated syscall instead of an ioctl is the correct way; especially > when it touches core kernel functionality. I mean that was one of the > takeaways from the pidfd API ioctl-vs-syscall discussion. > > A syscall is nicer especially for core-kernel code like this. > So I guess the only way to find out is to try the syscall approach and > either get yelled and switch to an ioctl() or have it accepted. > > What does everyone else think? Arnd, still in favor of a syscall I take > it. Oleg, you had suggested a syscall too, right? Florian, any > thoughts/worries on/about this from the glibc side? > > Christian My feelings towards this are that syscalls might pose a problem if we ever want to extend this API. Of course we can have a reserved "flags" field, and populate it later, but what if we turn out to need a proper struct? I already know we're going to want to add one around cgroup metadata (net_cls), and likely we'll want to add a "steal" flag as well. As Arnd mentioned earlier, this is trivial to fix in a traditional ioctl environment, as ioctls are "cheap". How do we feel about potentially adding a pidfd_getfd2? Or are we confident that reserved flags will save us?
