On 18 Oct 2023, at 11:18, Charles Hedrick wrote:

Ubuntu added fasc, but it's a kernel parameter. It can be changed without
a reboot, so we were able to fix the problem. It appears that this has
become the default upstream. I looked at Ubuntu's kernel code for their
next LTS, and it looks like they've accepted the upstream code, so the
problem shouldn't occur in the next LTS. Meanwhile we've taken precautions
to set the option on all our systems.

I'm surprised - I haven't seen any "fasc" mount option go upstream.  Where
did you see the upstream work?

I'll probably hack up a patch to dump the access cache via sysfs file and
send that sometime this week, I can copy you if you have interest.  I'm
thinking usage would look something like:

echo <uid> > /sys/fs/nfs/0\:57/drop_access_cache

Ben