[systemd-devel] autofs and hugetlbfs on ARM

[Kay Sievers]

On Tue, Jun 28, 2011 at 09:43, Michael Olbrich <m.olbrich at pengutronix.de> wrote:
> more stuff from the embedded front. On ARM hugetlbfs is not supported. The
> result is rather confusing for the user:
> At first /dev/hugepages exists. If I run "ls /dev/hugepages",
> "mount[494]: mount: unknown filesystem type 'hugetlbfs'" is logged and
> ls says "ls: /dev/hugepages: No such device".
> Afterwards /dev/hugepages is gone.

That doesn't sound too bad. :) It doesn't hang the process that tries
to access the mountpoint? That's what others have seen.

> Any hint, on how to disable unsupported filesystems for autofs? I guess
> /proc/filesystems should be checked but I didn't understand the systemd
> autofs code.

It's not that easy for some filesystems, as we want to establish the
autofs mountpoint even when the kernel module is not loaded. We
actually want to defer the loading of some module to the access of the
mountpoint.

Maybe we should drop 'hugetlbfs' from the default, and people should
just use the new Transparent Hugepage Support in the kernel.

You should probably just not install
/lib/systemd/system/dev-hugepages.mount to avoid the issue.

Kay