From: "J. Bruce Fields" <bfields@fieldses.org>
Subject: Re: ETIMEDOUT in nfsd?
Date: Tue, 3 Aug 2004 15:16:10 -0400
Sender: nfs-admin@lists.sourceforge.net
Message-ID: <20040803191610.GC7781@fieldses.org>
References: <20040803081503.GM5581@sgi.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Neil Brown <neilb@cse.unsw.edu.au>,
	Linux NFS Mailing List <nfs@lists.sourceforge.net>
To: Greg Banks <gnb@sgi.com>
In-Reply-To: <20040803081503.GM5581@sgi.com>
Errors-To: nfs-admin@lists.sourceforge.net

On Tue, Aug 03, 2004 at 06:15:03PM +1000, Greg Banks wrote:
> So I was somewhat surprised to see that in 2.6, the mapping from
> Linux errno to NFS error in fs/nfsd/nfsproc.c:nfserrno() maps
> -EAGAIN to nfserr_dropit, causing nfsd_dispatch to just drop the
> call and not reply.  Furthermore I need to return the network
> error -ETIMEDOUT to get NFSERR_JUKEBOX.  I don't get it...can
> someone explain both of these?

The server does upcalls to userspace daemons (usually to mountd to get
export options or IP address->client name mappings) by doing a lookup in
a cache, and returning -EAGAIN if an upcall is required.  The request is
then dropped, a copy of the request is made (see svcsock.c:svc_defer())
and reprocessed at a later time (see svcsock.c:svc_revisit()).

I have some rough notes on all this at

http://www.fieldses.org/~bfields/kernel/svc_caches/sunrpc_svc_cache.txt

and Neil has some documentation in Documentation/sunrpc-cache.txt.

--Bruce Fields


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