Re: [PATCH/RFC] NFS: handle NFSv4.1 server that doesn't support NFS4_OPEN_CLAIM_DELEG_CUR_FH

[NeilBrown <neilb@suse.de>]

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On Wed, Dec 18 2019, Trond Myklebust wrote:

> On Thu, 2019-12-19 at 09:47 +1100, NeilBrown wrote:
>> If an NFSv4.1 server doesn't support NFS4_OPEN_CLAIM_DELEG_CUR_FH
>> (e.g. Linux 3.0), and a newer NFS client tries to use it to claim
>> an open before returning a delegation, the server might return
>> NFS4ERR_BADXDR.
>> That is what Linux 3.0 does, though the RFC doesn't seem to be
>> explicit
>> on which flags must be supported, and what error can be returned for
>> unsupported flags.
>
> NFS4ERR_BADXDR is defined in RFC5661, section 15.1.1.1 as meaning
>
> "The arguments for this operation do not match those specified in the
> XDR definition."
>
> That's clearly not the case here, so I'd chalk this down to a fairly
> blatant server bug, at which point it makes no sense to fix it in the
> client.

Ok, but the RFC seems to suggest it is OK to not support this flag, so
suppose I fixed the server to return NFS4ERR_NOTSUPP instead.
The client still wouldn't handle this response gracefully.

Thanks,
NeilBrown


diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index caacf5e7f5e1..14f958d16648 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2174,6 +2174,13 @@ static int nfs4_open_reclaim(struct nfs4_state_owner *sp, struct nfs4_state *sta
 static int nfs4_handle_delegation_recall_error(struct nfs_server *server, struct nfs4_state *state, const
nfs4_stateid *stateid, struct file_lock *fl, int err)
 {
	switch (err) {
+		case -NFS4ERR_NOTSUPP: {
+			struct nfs4_exception exception;
+			if (nfs4_clear_cap_atomic_open_v1(server, -EINVAL,
+							  &exception))
+				return -EAGAIN;
+		}
+			/* fallthrough */
		default:
			printk(KERN_ERR "NFS: %s: unhandled error "
					"%d.\n", __func__, err);


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