Re: [PATCH 1/1] NFSD: cancel CB_RECALL_ANY call when nfs4_client is about to be destroyed

[Chuck Lever <chuck.lever@oracle.com>]

On Tue, Mar 26, 2024 at 11:13:29AM -0700, Dai Ngo wrote:
> Currently when a nfs4_client is destroyed we wait for the cb_recall_any
> callback to complete before proceed. This adds unnecessary delay to the
> __destroy_client call if there is problem communicating with the client.

By "unnecessary delay" do you mean only the seven-second RPC
retransmit timeout, or is there something else?

I can see that a server shutdown might want to cancel these, but why
is this a problem when destroying an nfs4_client?


> This patch addresses this issue by cancelling the CB_RECALL_ANY call from
> the workqueue when the nfs4_client is about to be destroyed.

Does CB_OFFLOAD need similar treatment?


> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
> ---
>  fs/nfsd/nfs4callback.c | 10 ++++++++++
>  fs/nfsd/nfs4state.c    | 10 +++++++++-
>  fs/nfsd/state.h        |  1 +
>  3 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> index 87c9547989f6..e5b50c96be6a 100644
> --- a/fs/nfsd/nfs4callback.c
> +++ b/fs/nfsd/nfs4callback.c
> @@ -1568,3 +1568,13 @@ bool nfsd4_run_cb(struct nfsd4_callback *cb)
>  		nfsd41_cb_inflight_end(clp);
>  	return queued;
>  }
> +
> +void nfsd41_cb_recall_any_cancel(struct nfs4_client *clp)
> +{
> +	if (test_bit(NFSD4_CLIENT_CB_RECALL_ANY, &clp->cl_flags) &&
> +			cancel_delayed_work(&clp->cl_ra->ra_cb.cb_work)) {
> +		clear_bit(NFSD4_CLIENT_CB_RECALL_ANY, &clp->cl_flags);
> +		atomic_add_unless(&clp->cl_rpc_users, -1, 0);
> +		nfsd41_cb_inflight_end(clp);
> +	}
> +}
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 1a93c7fcf76c..0e1db57c9a19 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -2402,6 +2402,7 @@ __destroy_client(struct nfs4_client *clp)
>  	}
>  	nfsd4_return_all_client_layouts(clp);
>  	nfsd4_shutdown_copy(clp);
> +	nfsd41_cb_recall_any_cancel(clp);
>  	nfsd4_shutdown_callback(clp);
>  	if (clp->cl_cb_conn.cb_xprt)
>  		svc_xprt_put(clp->cl_cb_conn.cb_xprt);
> @@ -2980,6 +2981,12 @@ static void force_expire_client(struct nfs4_client *clp)
>  	clp->cl_time = 0;
>  	spin_unlock(&nn->client_lock);
>  
> +	/*
> +	 * no need to send and wait for CB_RECALL_ANY
> +	 * when client is about to be destroyed
> +	 */
> +	nfsd41_cb_recall_any_cancel(clp);
> +
>  	wait_event(expiry_wq, atomic_read(&clp->cl_rpc_users) == 0);
>  	spin_lock(&nn->client_lock);
>  	already_expired = list_empty(&clp->cl_lru);
> @@ -6617,7 +6624,8 @@ deleg_reaper(struct nfsd_net *nn)
>  		clp->cl_ra->ra_bmval[0] = BIT(RCA4_TYPE_MASK_RDATA_DLG) |
>  						BIT(RCA4_TYPE_MASK_WDATA_DLG);
>  		trace_nfsd_cb_recall_any(clp->cl_ra);
> -		nfsd4_run_cb(&clp->cl_ra->ra_cb);
> +		if (!nfsd4_run_cb(&clp->cl_ra->ra_cb))
> +			clear_bit(NFSD4_CLIENT_CB_RECALL_ANY, &clp->cl_flags);
>  	}
>  }
>  
> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> index 01c6f3445646..259b4af7d226 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -735,6 +735,7 @@ extern void nfsd4_change_callback(struct nfs4_client *clp, struct nfs4_cb_conn *
>  extern void nfsd4_init_cb(struct nfsd4_callback *cb, struct nfs4_client *clp,
>  		const struct nfsd4_callback_ops *ops, enum nfsd4_cb_op op);
>  extern bool nfsd4_run_cb(struct nfsd4_callback *cb);
> +extern void nfsd41_cb_recall_any_cancel(struct nfs4_client *clp);
>  extern int nfsd4_create_callback_queue(void);
>  extern void nfsd4_destroy_callback_queue(void);
>  extern void nfsd4_shutdown_callback(struct nfs4_client *);
> -- 
> 2.39.3
> 

-- 
Chuck Lever