NFS4ERR_FILE_OPEN handling in Linux

Neil Brown
2009-10-15T00:34:49Z

Hi Trond,

Following up for a customer who had problem with NFSv4 when talking
to a Solaris server with "nbman" enabled, I have questions about the
handling of NFS4ERR_FILE_OPEN.
In particular:
1/ should commit c514983d8d2260020543a81589a2b8c7d4bdab4e be
reverted, and
2/ should nfs_errtbl map NFS4ERR_FILE_OPEN to -EBUSY rather than
defaulting to -EIO

That commit, included below for reference, causes the NFS client to
retry indefinitely if NFS4ERR_FILE_OPEN is returned. This
contradicts the comment which suggests it will only "retry a few
times" and cannot be correct as a file could be held open (thus
causing the error) indefinitely.

The problem that the patch claims to address (relating to ordering of
async calls) is, I believe, addressed properly by the subsequent
patch

commit a49c3c7736a2e77931dabc5bc4a83fb4b2da013e
Author: Trond Myklebust <Trond.Myklebust@netapp.com>
Date: Thu Oct 18 18:03:27 2007 -0400

NFSv4: Ensure that we wait for the CLOSE request to complete

So I believe that first patch is both unnecessary and incorrect.

When the server refuses to perform an action because the file is
currently open, I think 'EIO' does not do justice to the situation at
all. EBUSY seems a lot more appropriate and does seem to be a
permitted error code for e.g. rename(2) and unlink(2). EACCES might
be a possible alternate. It doesn't really mean the same thing, but
it is likely to be handled in an appropriate way. Apparently the
Solaris client returns EACCES.

Thoughts?

Thanks,
NeilBrown

>From c514983d8d2260020543a81589a2b8c7d4bdab4e Mon Sep 17 00:00:00 2001
From: Trond Myklebust <Trond.Myklebust@netapp.com>
Date: Fri, 15 Sep 2006 08:25:04 -0400
Subject: [PATCH] NFSv4: Handle the condition NFS4ERR_FILE_OPEN

Retry a few times before we give up: the error is usually due to ordering
issues with asynchronous RPC calls.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---
fs/nfs/nfs4proc.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index c218cc4..c49ac3e 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2891,6 +2891,7 @@ int nfs4_handle_exception(const struct nfs_server *server, int errorcode, struct
if (ret == 0)
exception->retry = 1;
break;
+ case -NFS4ERR_FILE_OPEN:
case -NFS4ERR_GRACE:
case -NFS4ERR_DELAY:
ret = nfs4_delay(server->client, &exception->timeout);
--
1.6.4.3