On Mon, Jan 31, 2022 at 05:33:29PM -0800, Luis Chamberlain wrote:
> It would seem we keep tacking on things with ioctls for the block
> layer and filesystems. Even for new trendy things like io_uring [0].
> For a few years I have found this odd, and have slowly started
> asking folks why we don't consider alternatives like a generic
> netlink family. I've at least been told that this is desirable
> but no one has worked on it. *If* we do want this I think we just
> not only need to commit to do this, but also provide a target. LSFMM
> seems like a good place to do this.
>
> Possible issues? Kernels without CONFIG_NET. Is that a deal breaker?
> We already have a few filesystems with their own generic netlink
> families, so not sure if this is a good argument against this.
>
> mcgrof@fulton ~/linux-next (git::master)$ git grep genl_register_family fs
> fs/cifs/netlink.c: ret = genl_register_family(&cifs_genl_family);
> fs/dlm/netlink.c: return genl_register_family(&family);
> fs/ksmbd/transport_ipc.c: ret = genl_register_family(&ksmbd_genl_family);
> fs/quota/netlink.c: if (genl_register_family("a_genl_family) != 0)
> mcgrof@fulton ~/linux-next (git::master)$ git grep genl_register_family drivers/block
> drivers/block/nbd.c: if (genl_register_family(&nbd_genl_family)) {
>
> Are there other reasons to *not* use generic netlink for new features?
> For folks with experience using generic netlink on the block layer and
> their own fs, any issues or pain points observed so far?
Netlink is a giant pain to use for userspace tbh. ioctl()s aren't great
but they are way easier to add and use.
