Turning off delegations in NFSv4 server?

Post by Jeff Garzik
Besides hacking the code, is there an easy way to turn off NFSv4
delegations in the kernel v4 server?
I'd like to observe behavior of the Linux v4 client when delegations are
not available.

The easiest thing is probably just to turn off leases:

echo 0 >/proc/sys/fs/leases-enable

--b.

Matt Bernstein

2010-03-04 09:23:26 UTC

echo 0 >/proc/sys/fs/leases-enable

I found this from two years ago, and am wondering
- is this still the easiest thing to do?
- is this on server, client or both?
- will it break anything else?

We have a CentOS 5.4 NFS3/NFS4/samba server with about 300 clients on its
subnet, and another 100-200 on another subnet, which under high load has
started kernel-panicking (sometimes in nfsd4_cb_recall).

I want to disable delegations to see if that cures our symptoms--but I
worry that turning leases off might cause other problems.

For now I'll probably do it anyway, given that status quo isn't stable :(

Matt

J. Bruce Fields

2010-03-04 14:33:18 UTC

echo 0 >/proc/sys/fs/leases-enable

Have you filed a bug with the backtraces?

Post by Matt Bernstein
I want to disable delegations to see if that cures our symptoms--but I
worry that turning leases off might cause other problems.

No, it shouldn't cause problems, at least for NFSv4 clients. (Samba may
be more reliant on leases, especially if Samba and NFSv4 clients are
acting on the same files at the same time--but I don't know.)

--b.

Post by Matt Bernstein
For now I'll probably do it anyway, given that status quo isn't stable :(
Matt

Matt Bernstein

2010-03-05 15:12:46 UTC

Post by J. Bruce Fields
echo 0 >/proc/sys/fs/leases-enable

Have you filed a bug with the backtraces?

Duly nudged. I've posted the most recent one to
<http://bugs.centos.org/view.php?id=4229>.

Post by Matt Bernstein
I want to disable delegations to see if that cures our symptoms--but I
worry that turning leases off might cause other problems.

Thanks; no-one's grumbled just yet.

Matt

J. Bruce Fields

2010-03-05 15:30:30 UTC

Post by J. Bruce Fields
echo 0 >/proc/sys/fs/leases-enable

Have you filed a bug with the backtraces?

Duly nudged. I've posted the most recent one to
<http://bugs.centos.org/view.php?id=4229>.

OK, thanks. Unfortunately that code has changed quite a bit since
2.6.18. I don't recall this specific bug, but I wouldn't be suprised if
it's something we've since fixed. Looking through 'gitk v2.6.18..
fs/nfsd/nfs4callback.c fs/nfsd/nfs4state.c' for delegation/callback
fixes might be one approach.

--b.