NFSv4 performance degradation with 12.0-CURRENT client

[Rick Macklem]

Alan Somers wrote:
[stuff snipped]
>Mounting nullfs with the nocache option, ad kib suggested, fixed the
>problem.  Also, applying kib's patch and then mounting nullfs with
>default options also fixed the problem.  Here is the nfsstat output
>for "ls -al" when using kib's patch.  Notice the client has far fewer
>opens:
I did a quick test which confirmed that the opens get closed when the "nocache"
option is used on the nullfs mount as well.

Kostik, I think your patch is a good idea and you can consider it reviewed by me
if you'd like.

I also did a quick test wth unionfs and it did not accumulate opens, so it doesn't
seem to suffer from this problem. (It does have issues, as noted by the BUGS
section of the mount_unionfs man page.)

rick