Re: mountd prevents spindown of non-exported disk

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Feb 25, 2008 at 03:24:49PM +0100, Timo Reimann wrote:
> Neil Brown wrote:
> > On Wednesday February 20, mailinglist-d4LLFNs4DFRA7UZ8SB9NFg@public.gmane.org wrote:
> >> Although there should be nothing accessing the disk except my custom
> >> backup cron job initiating at 5am daily, something was constantly
> >> bringing it back into active state after a rough 20-25 minutes. With the
> >> help of blktrace, I monitored every single I/O access to the disk and
> >> found a single process only that would cause the wake-up:
> >>
> >>
> >> $ sudo blkparse -i hda.blktrace.0
> >> Input file hda.blktrace.0 added
> >> [...]
> >>   3,0    0        6    88.950000000  6806  Q   R 447 + 8 [rpc.mountd]
> >> [...]
> >>
> >>
> >> So for some reason, rpc.mountd issues this disk request in regular
> >> intervals although nothing on the disk is being NFS-exported according
> >> to /etc/exports.
> > 
> > This is doubtlessly something related to libblkid.
> > 
> > We only ever ask it for the UID of specific devices that have been
> > exported.  However it is quite possible that it touches other devices
> > as well...
> > 
> > I'm using libblkid in a way that it wasn't originally designed to be
> > used.  It was (as far as I can tell) designed to find a device given a
> > UUID or similar.  In that case you would expect it to touch every
> > device.
> > 
> > You could always build your own nfs-utils and configure with
> > --without-uuid.
> 
> I did so and re-compiled the nfs-utils package, resulting in new
> packages of nfs-common and nfs-kernel-server under Ubuntu 7.10.
> 
> However, another re-run of blktrace yielded that the problem did not go
> away. There are still lots of disk accesses from mountd, and the strace
> output continuously contains open calls to the unmounted backup filesystem.
> 
> 
> Is there anything else I can do in attempt to resolve this issue? I
> suppose pasting the complete output of strace might help, but I wouldn't
> do so without explicit confirmation of yours as the log-file is 3.2 MB
> large.

Probably the most likely to read such an strace are me, Neil, and Steve
(<steved@redhat.com>), so you might just send it privately to the three
of us.

--b.