Re: [PATCH v6 04/14] nfsd: allow unrecognisable filehandle for foreign servers in COPY

[Chuck Lever <cel@kernel.org>]

On Sat, Nov 22, 2025 at 11:47:02AM +1100, NeilBrown wrote:
> From: NeilBrown <neil@brown.name>
> 
> RFC-7862 acknowledges that a filehandle provided as the source of an
> inter-server copy might result in NFS4ERR_STALE when given to PUTFH, and
> gives guidance on how this error can be ignored (section 15.2.3).
> 
> NFS4ERR_BADHANDLE is also a possible error in this circumstance if the
> foreign server is running a different implementation of NFS than the
> current one.

The RFC uses the terms "source" and "destination" server, fwiw.

It would be interesting to see if nfserr_badhandle can be triggered
during an NFSD <-> NFSD copy.


> This appears to be a simple omission in the RFC.

Perhaps. It might also be the result of the RFC authors giving
implementers flexibility to innovate.

I would like to consult with the WG and possibly file an errata, or
add this observation to the "NFSv4.2 COPY implementation experience"
document I'm helping Olga with:

https://datatracker.ietf.org/doc/draft-cel-nfsv4-copy-implementation-experience/

They might want to consider NFS4ERR_MOVED as well.


> There can be no harm in delaying a BADHANDLE error in the same situation
> where we already delay STALE errors, and no harm in sending a locally
> "bad" handle to a foreign server to request a COPY.

These are plausible claims. But IMO, they need firmer rationale.


> So extend the test in nfsd4_putfh to also check for nfserr_badhandle.
> 
> Signed-off-by: NeilBrown <neil@brown.name>
> ---
>  fs/nfsd/nfs4proc.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 112e62b6b9c6..ae34b816371c 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -693,7 +693,8 @@ nfsd4_putfh(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	       putfh->pf_fhlen);
>  	ret = fh_verify(rqstp, &cstate->current_fh, 0, NFSD_MAY_BYPASS_GSS);
>  #ifdef CONFIG_NFSD_V4_2_INTER_SSC
> -	if (ret == nfserr_stale && inter_copy_offload_enable) {
> +	if ((ret == nfserr_badhandle || ret == nfserr_stale) &&
> +	    inter_copy_offload_enable) {
>  		struct nfsd4_compoundargs *args = rqstp->rq_argp;
>  		struct nfsd4_compoundres *resp = rqstp->rq_resp;
>  
> @@ -713,7 +714,11 @@ nfsd4_putfh(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  			 *  NOT return NFS4ERR_STALE for either
>  			 *  operation.
>  			 * We limit this to when there is a COPY
> -			 * in the COMPOUND.
> +			 * in the COMPOUND, and extend it to
> +			 * also ignore NFS4ERR_BADHANDLE despite the
> +			 * RFC not requiring this.  If the remote
> +			 * server is running a different NFS implementation,
> +			 * NFS4ERR_BADHANDLE is a likely error.
>  			 */
>  			ret = 0;
>  		}
> -- 
> 2.50.0.107.gf914562f5916.dirty
> 
> 

-- 
Chuck Lever