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Subject: Re: [nfs-utils RPC-PATCH 0/4] Add options to nfsd etc to avoid needing to write to /proc
From: Trond Myklebust <trond.myklebust@primarydata.com>
In-Reply-To: <6C00269A-B840-4835-B277-CBCA9EE69AA8@primarydata.com>
Date: Mon, 24 Feb 2014 17:47:35 -0800
Cc: Dickson Steve <SteveD@redhat.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Message-Id: <5A5D3C51-B7DC-4D4E-9C38-A4A294467ADC@primarydata.com>
References: <20140220063616.6548.42556.stgit@notabene.brown> <33021BB9-598C-4A65-B386-BE230E91894F@primarydata.com> <20140225123701.08c59745@notabene.brown> <6C00269A-B840-4835-B277-CBCA9EE69AA8@primarydata.com>
To: Brown Neil <neilb@suse.de>
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On Feb 24, 2014, at 17:44, Trond Myklebust <trond.myklebust@primarydata.com> wrote:

> 
> On Feb 24, 2014, at 17:37, NeilBrown <neilb@suse.de> wrote:
> 
>> On Thu, 20 Feb 2014 08:11:47 -0500 Trond Myklebust
>> <trond.myklebust@primarydata.com> wrote:
>> 
>>> 
>>> On Feb 20, 2014, at 1:36, Neil Brown <neilb@suse.de> wrote:
>>> 
>>>> There are a number of NFS-related setting that currently must be set
>>>> by writing to various files under /proc.
>>>> This is a bit clumsy, particularly for systemd unit files.
>>>> 
>>>> So this series adds options to a number of commands where relevant.
>>>> 
>>>> The first two (rdma, and  nfsv4{grace,lease}time) I am quite comfortable with.
>>>> The third (nlm grace time) I think is probably right but if someone can argue
>>>> an alternate approach I'm unlikely to resist.
>>>> The fourth is .... uhm.  You better look yourself.
>>>> 
>>>> Part of me thinks that nlm port numbers should be set in /etc/sysctl.conf (or sysctl.d)
>>>> and /etc/modprobe.d should have something like
>>>> 
>>>> install lockd  sysctl -p /etc/sysctl.d/lockd
>>>> 
>>>> but last time I tried that it broke "modprobe --show-depends".
>>>> Also it is awkward to get setting from /etc/sysconfig/nfs into /etc/sysctl.d/lockd
>>>> 
>>>> Thoughts?
>>> 
>>> Why not just do most of this at module load time with something like "modprobe lockd lockd.nlm_grace_period=<nsecs> lockd.nlm_tcpport=<portnr> ???
>>> Better yet, add/edit appropriate entries in /etc/modprobe.conf.d at system setup time.
>>> 
>> 
>> Adding entries to /etc/modprobe.conf.d doesn't help if nfs is compiled in to
>> the base kernel.
>> Conversely, adding entries to /etc/sysctl.d doesn't help if nfs is a module.
>> You could conceivable do both (for those few values that are available both
>> as module parameters and sysctl settings) but that is clumsy and error prone.
>> 
> 
> All the NFS sysctl settings now have module parameter equivalents.
> Note that systemd can also override using the /sys/module interface, but the problem with both sysctl and /sys/module is that they get set _after_ the module has been loaded, and hence there is plenty of potential for races with mount requests.

BTW: if you don?t want to compile your kernel with module support, then those same parameters can be used on the kernel command line. That provides the same guarantees w.r.t. races...

_________________________________
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@primarydata.com