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SubjectRe: [NFS] [PATCH 008 of 11] knfsd: Prepare knfsd for support of rsize/wsize of up to 1MB, over TCP.
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On Tue, Oct 03, 2006 at 11:36:32AM +1000, Neil Brown wrote:
> The only real problem is that NFSv4 can have arbitrarily large
> non-payload data, and arbitrarily many payloads. But I guess any
> client that trying to send two full-sized payloads in the one request
> is asking for trouble (I don't suppose the RPC spells this out at
> all?).

The RFC? Well, it does have a "RESOURCE" error that the server can
return for overly complicated compounds. It doesn't give much guidance
on when exactly that could happen, but if there's ever a clear case for
returning NFS4ERR_RESOURCE, I think it must be the case of a client
trying to circumvent the maximum read/write size by using multiple read
or write operations in a single compound.

(We have some other odd restrictions on the sorts of compounds we can
accept, which I'd like to relax. But that's a problem for another day.)

> And the fact that the code change to effect this is so tiny seems to
> imply that most of the code was already assuming that sv_bufsz was
> really the payload size rather than the packet size.

There's also the check at the end of svc_tcp_recvfrom():

if (svsk->sk_reclen > serv->sv_bufsz) {
printk(KERN_NOTICE "RPC: bad TCP reclen 0x%08lx (large)\n",
(unsigned long) svsk->sk_reclen);
goto err_delete;
}
--b.
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