Re: [PATCH 09/14] nfsd: return hard failure for OP_SETCLIENTID when there are too many clients.

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2024-07-15 at 17:14 +1000, NeilBrown wrote:
> If there are more non-courteous clients than the calculated limit, we
> should fail the request rather than report a soft failure and
> encouraging the client to retry indefinitely.
> 
> If there a courteous clients which push us over the limit, then expedite
> their removal.
> 
> This is not known to have caused a problem is production use, but
> testing of lots of clients reports repeated NFS4ERR_DELAY responses
> which doesn't seem helpful.
> 
> Also remove an outdated comment - we do use a slab cache.
> 
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>  fs/nfsd/nfs4state.c | 23 +++++++++++++----------
>  1 file changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index a20c2c9d7d45..88936f3189e1 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -2212,21 +2212,20 @@ STALE_CLIENTID(clientid_t *clid, struct nfsd_net *nn)
>  	return 1;
>  }
>  
> -/* 
> - * XXX Should we use a slab cache ?
> - * This type of memory management is somewhat inefficient, but we use it
> - * anyway since SETCLIENTID is not a common operation.
> - */
>  static struct nfs4_client *alloc_client(struct xdr_netobj name,
>  				struct nfsd_net *nn)
>  {
>  	struct nfs4_client *clp;
>  	int i;
>  
> -	if (atomic_read(&nn->nfs4_client_count) >= nn->nfs4_max_clients) {
> +	if (atomic_read(&nn->nfs4_client_count) -
> +	    atomic_read(&nn->nfsd_courtesy_clients) >= nn->nfs4_max_clients)
> +		return ERR_PTR(-EREMOTEIO);
> +

nit: I know it gets remapped, but why EREMOTEIO? From nfsd's standpoint
this would seem to imply a problem on the client. Maybe:

#define EUSERS          87      /* Too many users */

...instead?

> +	if (atomic_read(&nn->nfs4_client_count) >= nn->nfs4_max_clients &&
> +	    atomic_read(&nn->nfsd_courtesy_clients) > 0)
>  		mod_delayed_work(laundry_wq, &nn->laundromat_work, 0);
> -		return NULL;
> -	}
> +
>  	clp = kmem_cache_zalloc(client_slab, GFP_KERNEL);
>  	if (clp == NULL)
>  		return NULL;
> @@ -3115,8 +3114,8 @@ static struct nfs4_client *create_client(struct xdr_netobj name,
>  	struct dentry *dentries[ARRAY_SIZE(client_files)];
>  
>  	clp = alloc_client(name, nn);
> -	if (clp == NULL)
> -		return NULL;
> +	if (IS_ERR_OR_NULL(clp))
> +		return clp;
>  
>  	ret = copy_cred(&clp->cl_cred, &rqstp->rq_cred);
>  	if (ret) {
> @@ -3498,6 +3497,8 @@ nfsd4_exchange_id(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	new = create_client(exid->clname, rqstp, &verf);
>  	if (new == NULL)
>  		return nfserr_jukebox;
> +	if (IS_ERR(new))
> +		return nfserr_resource;
>  	status = copy_impl_id(new, exid);
>  	if (status)
>  		goto out_nolock;
> @@ -4416,6 +4417,8 @@ nfsd4_setclientid(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	new = create_client(clname, rqstp, &clverifier);
>  	if (new == NULL)
>  		return nfserr_jukebox;
> +	if (IS_ERR(new))
> +		return nfserr_resource;
>  	spin_lock(&nn->client_lock);
>  	conf = find_confirmed_client_by_name(&clname, nn);
>  	if (conf && client_has_state(conf)) {

Patch looks fine otherwise though.

Reviewed-by: Jeff Layton <jlayton@kernel.org>