Re: Mounting NFS root FS

From: Trond Myklebust
Date: Mon Dec 04 2006 - 13:22:00 EST


On Mon, 2006-12-04 at 19:12 +0200, Janne Karhunen wrote:
> > 2) NFS provides persistent storage.
>
> To me this sounds like a chicken and an egg problem. It
> both depends and provides this at the same time :/. But
> hey, if it's supposed to work then OK.

??? Locking depends on persistent storage, but persistent storage never
depended on locking. Neither rpc.statd nor lockd, nor the nfs client
depend on locking working a priori.

> Anyhoo, I tried this at some stage and failed as random
> clients seemed to occasionally get stuck in insmod at
> boot (infinite wait on lock that never gets released).
> At that stage guess was that server could not properly
> recognize client reboot given stale client lock data.
> But if it's supposed to work I guess I have to give it
> another shot and do better analysis on it.
>
> What about NLM/NSM protocol issues - do they properly
> deal with packet loss and clients that stay down (client
> holding a lock crashing and staying down; will the lock
> ever be released)?

1) Packet loss is dealt with by retrying ad-infinitum.

2) No. The problem of client crashes was fixed in NFSv4 with the
addition of lease-based locks.

> Â And why does insmod require a lock on module at load??

Does it? I've no idea why it should need that.

Trond

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