On Tue, Feb 01, 2022 at 02:14:42AM +0000, Matthew Wilcox wrote:
> 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].
>
> I think the problem is that it's a huge effort to add a new syscall.
As we'll all agree it should be.
> You have to get it into each architecture. Having a single place to
> add a new syscall would help reduce the number of places we use
> multiplexor syscalls like ioctl().
Jeesh, is such a thing really possible? I wonder if Arnd has tried or
what he'd think...
I'm not arguing in favor of this, I am not sure if we want to be
encouraging new syscalls for everything. I'd agree that if its generic
perhaps so, but my own focus on this thread was block / fs.
So my hope with this thread was to encourage discussion for alternatives
to ioctls specifically for the block layer / filesystems.
> > 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.
>
> I don't know that I agree that "generic netlink" is desirable.
> I'd like to know more about the pros and cons of this idea.
Yeah it was just an idea example of a framework which does actually
get us closer to some form of real data types for what is being
supported, and which also pushes us to use kdoc.
> > 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)
>
> I'm not sure these are good arguments in favour ... other than quota,
> these are all network filesystems, which aren't much use without
> CONFIG_NET.
It's a good point.
> > mcgrof@fulton ~/linux-next (git::master)$ git grep genl_register_family drivers/block
> > drivers/block/nbd.c: if (genl_register_family(&nbd_genl_family)) {
>
> The, er, _network_ block device, right?
:) Sure.
Luis
