[PATCH v2 24/42] lockd: Use xdrgen XDR functions for the NLMv4 CANCEL_MSG procedure

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

The CANCEL_MSG procedure is part of NLM's asynchronous lock
request flow, where clients send CANCEL_MSG to cancel pending
lock requests. This patch continues the xdrgen migration by
converting CANCEL_MSG to use generated XDR functions.

This patch converts the CANCEL_MSG procedure to use xdrgen
functions nlm4_svc_decode_nlm4_cancargs and
nlm4_svc_encode_void generated from the NLM version 4 protocol
specification. The procedure handler uses xdrgen types through
the nlm4_cancargs_wrapper structure that bridges between
generated code and the legacy nlm_lock representation.

The pc_argzero field is set to zero because xdrgen decoders
reliably initialize all arguments in the argp->xdrgen field,
making the early defensive memset unnecessary. Remaining argp
fields are cleared as needed.

The NLM async callback mechanism uses client-side functions
which continue to take legacy results like struct nlm_res,
preventing CANCEL and CANCEL_MSG from sharing code for now.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/lockd/svc4proc.c | 111 +++++++++++++++++++++++++-------------------
 1 file changed, 64 insertions(+), 47 deletions(-)

diff --git a/fs/lockd/svc4proc.c b/fs/lockd/svc4proc.c
index 7ab458648637..4c983a04e9f1 100644
--- a/fs/lockd/svc4proc.c
+++ b/fs/lockd/svc4proc.c
@@ -453,37 +453,6 @@ nlm4svc_proc_lock(struct svc_rqst *rqstp)
 	return nlm4svc_do_lock(rqstp, true);
 }
 
-static __be32
-__nlm4svc_proc_cancel(struct svc_rqst *rqstp, struct nlm_res *resp)
-{
-	struct nlm_args *argp = rqstp->rq_argp;
-	struct nlm_host	*host;
-	struct nlm_file	*file;
-
-	dprintk("lockd: CANCEL        called\n");
-
-	resp->cookie = argp->cookie;
-
-	/* Don't accept requests during grace period */
-	if (locks_in_grace(SVC_NET(rqstp))) {
-		resp->status = nlm_lck_denied_grace_period;
-		return rpc_success;
-	}
-
-	/* Obtain client and file */
-	if ((resp->status = nlm4svc_retrieve_args(rqstp, argp, &host, &file)))
-		return resp->status == nlm_drop_reply ? rpc_drop_reply :rpc_success;
-
-	/* Try to cancel request. */
-	resp->status = nlmsvc_cancel_blocked(SVC_NET(rqstp), file, &argp->lock);
-
-	dprintk("lockd: CANCEL        status %d\n", ntohl(resp->status));
-	nlmsvc_release_lockowner(&argp->lock);
-	nlmsvc_release_host(host);
-	nlm_release_file(file);
-	return rpc_success;
-}
-
 /**
  * nlm4svc_proc_cancel - CANCEL: Cancel an outstanding blocked lock request
  * @rqstp: RPC transaction context
@@ -863,19 +832,67 @@ static __be32 nlm4svc_proc_lock_msg(struct svc_rqst *rqstp)
 				__nlm4svc_proc_lock_msg);
 }
 
+static __be32
+__nlm4svc_proc_cancel_msg(struct svc_rqst *rqstp, struct nlm_res *resp)
+{
+	struct nlm4_cancargs_wrapper *argp = rqstp->rq_argp;
+	unsigned char type = argp->xdrgen.exclusive ? F_WRLCK : F_RDLCK;
+	struct net *net = SVC_NET(rqstp);
+	struct nlm_file	*file = NULL;
+	struct nlm_host	*host = NULL;
+
+	resp->status = nlm_lck_denied_nolocks;
+	if (nlm4_netobj_to_cookie(&resp->cookie, &argp->xdrgen.cookie))
+		goto out;
+
+	resp->status = nlm_lck_denied_grace_period;
+	if (locks_in_grace(net))
+		goto out;
+
+	resp->status = nlm_lck_denied_nolocks;
+	host = nlm4svc_lookup_host(rqstp, argp->xdrgen.alock.caller_name, false);
+	if (!host)
+		goto out;
+
+	resp->status = nlm4svc_lookup_file(rqstp, host, &argp->lock,
+					   &file, &argp->xdrgen.alock, type);
+	if (resp->status)
+		goto out;
+
+	resp->status = nlmsvc_cancel_blocked(net, file, &argp->lock);
+	nlmsvc_release_lockowner(&argp->lock);
+
+out:
+	if (file)
+		nlm_release_file(file);
+	nlmsvc_release_host(host);
+	return resp->status == nlm_drop_reply ? rpc_drop_reply : rpc_success;
+}
+
+/**
+ * nlm4svc_proc_cancel_msg - CANCEL_MSG: Cancel an outstanding lock request
+ * @rqstp: RPC transaction context
+ *
+ * Returns:
+ *   %rpc_success:		RPC executed successfully.
+ *   %rpc_system_err:		RPC execution failed.
+ *
+ * RPC synopsis:
+ *   void NLMPROC4_CANCEL_MSG(nlm4_cancargs) = 8;
+ *
+ * The response to this request is delivered via the CANCEL_RES procedure.
+ */
 static __be32 nlm4svc_proc_cancel_msg(struct svc_rqst *rqstp)
 {
-	struct nlm_args *argp = rqstp->rq_argp;
-	struct nlm_host	*host;
+	struct nlm4_cancargs_wrapper *argp = rqstp->rq_argp;
+	struct nlm_host *host;
 
-	dprintk("lockd: CANCEL_MSG    called\n");
-
-	host = nlmsvc_lookup_host(rqstp, argp->lock.caller, argp->lock.len);
+	host = nlm4svc_lookup_host(rqstp, argp->xdrgen.alock.caller_name, false);
 	if (!host)
 		return rpc_system_err;
 
-	return nlm4svc_callback(rqstp, host, NLMPROC_CANCEL_RES,
-				__nlm4svc_proc_cancel);
+	return nlm4svc_callback(rqstp, host, NLMPROC4_CANCEL_RES,
+				__nlm4svc_proc_cancel_msg);
 }
 
 static __be32 nlm4svc_proc_unlock_msg(struct svc_rqst *rqstp)
@@ -1147,15 +1164,15 @@ static const struct svc_procedure nlm4svc_procedures[24] = {
 		.pc_xdrressize	= XDR_void,
 		.pc_name	= "LOCK_MSG",
 	},
-	[NLMPROC_CANCEL_MSG] = {
-		.pc_func = nlm4svc_proc_cancel_msg,
-		.pc_decode = nlm4svc_decode_cancargs,
-		.pc_encode = nlm4svc_encode_void,
-		.pc_argsize = sizeof(struct nlm_args),
-		.pc_argzero = sizeof(struct nlm_args),
-		.pc_ressize = sizeof(struct nlm_void),
-		.pc_xdrressize = St,
-		.pc_name = "CANCEL_MSG",
+	[NLMPROC4_CANCEL_MSG] = {
+		.pc_func	= nlm4svc_proc_cancel_msg,
+		.pc_decode	= nlm4_svc_decode_nlm4_cancargs,
+		.pc_encode	= nlm4_svc_encode_void,
+		.pc_argsize	= sizeof(struct nlm4_cancargs_wrapper),
+		.pc_argzero	= 0,
+		.pc_ressize	= 0,
+		.pc_xdrressize	= XDR_void,
+		.pc_name	= "CANCEL_MSG",
 	},
 	[NLMPROC_UNLOCK_MSG] = {
 		.pc_func = nlm4svc_proc_unlock_msg,
-- 
2.52.0