[PATCH v3 24/29] lockd: Use xdrgen XDR functions for the NLMv4 UNSHARE procedure

[Chuck Lever <cel@kernel.org>]

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

Now that the share helpers have been decoupled from the
NLMv3-specific struct nlm_args and file_lock initialization
has been hoisted into the procedure handler, the NLMv4 UNSHARE
procedure can be converted to use xdrgen-generated XDR
functions.

Replace the NLMPROC4_UNSHARE entry in the nlm_procedures4
array with an entry that uses xdrgen-built XDR decoders and
encoders. The procedure handler is updated to use the new
wrapper structures (nlm4_shareargs_wrapper and
nlm4_shareres_wrapper) and access arguments through the
argp->xdrgen hierarchy.

The .pc_argzero field is set to zero because xdrgen decoders
fully initialize all fields in argp->xdrgen, making the early
defensive memset unnecessary. The remaining argp fields that
fall outside the xdrgen structures are cleared explicitly as
needed.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/lockd/svc4proc.c | 98 ++++++++++++++++++++++++++++-----------------
 1 file changed, 62 insertions(+), 36 deletions(-)

diff --git a/fs/lockd/svc4proc.c b/fs/lockd/svc4proc.c
index fbbc5db7a4f7..5d85f888fdf4 100644
--- a/fs/lockd/svc4proc.c
+++ b/fs/lockd/svc4proc.c
@@ -1124,44 +1124,70 @@ static __be32 nlm4svc_proc_share(struct svc_rqst *rqstp)
 		rpc_drop_reply : rpc_success;
 }
 
-/*
- * UNSHARE: Release a DOS share.
+/**
+ * nlm4svc_proc_unshare - UNSHARE: Release a share reservation
+ * @rqstp: RPC transaction context
+ *
+ * Returns:
+ *   %rpc_success:		RPC executed successfully.
+ *   %rpc_drop_reply:		Do not send an RPC reply.
+ *
+ * RPC synopsis:
+ *   nlm4_shareres NLMPROC4_UNSHARE(nlm4_shareargs) = 21;
+ *
+ * Permissible procedure status codes:
+ *   %NLM4_GRANTED:		The share reservation was released.
+ *   %NLM4_DENIED_GRACE_PERIOD:	The server has recently restarted and is
+ *				re-establishing existing locks, and is not
+ *				yet ready to accept normal service requests.
+ *
+ * The Linux NLM server implementation also returns:
+ *   %NLM4_DENIED_NOLOCKS:	A needed resource could not be allocated.
+ *   %NLM4_STALE_FH:		The request specified an invalid file handle.
+ *   %NLM4_FBIG:		The request specified a length or offset
+ *				that exceeds the range supported by the
+ *				server.
+ *   %NLM4_FAILED:		The request failed for an unspecified reason.
  */
-static __be32
-nlm4svc_proc_unshare(struct svc_rqst *rqstp)
+static __be32 nlm4svc_proc_unshare(struct svc_rqst *rqstp)
 {
-	struct nlm_args *argp = rqstp->rq_argp;
-	struct nlm_res *resp = rqstp->rq_resp;
+	struct nlm4_shareargs_wrapper *argp = rqstp->rq_argp;
+	struct nlm4_shareres_wrapper *resp = rqstp->rq_resp;
 	struct nlm_lock	*lock = &argp->lock;
-	struct nlm_host	*host;
-	struct nlm_file	*file;
+	struct nlm4_lock xdr_lock = {
+		.fh		= argp->xdrgen.share.fh,
+		.oh		= argp->xdrgen.share.oh,
+		.svid		= ~(u32)0,
+	};
+	struct nlm_host	*host = NULL;
+	struct nlm_file	*file = NULL;
 
-	dprintk("lockd: UNSHARE       called\n");
+	resp->xdrgen.cookie = argp->xdrgen.cookie;
 
-	resp->cookie = argp->cookie;
+	resp->xdrgen.stat = nlm_lck_denied_grace_period;
+	if (locks_in_grace(SVC_NET(rqstp)))
+		goto out;
 
-	/* Don't accept requests during grace period */
-	if (locks_in_grace(SVC_NET(rqstp))) {
-		resp->status = nlm_lck_denied_grace_period;
-		return rpc_success;
-	}
+	resp->xdrgen.stat = nlm_lck_denied_nolocks;
+	host = nlm4svc_lookup_host(rqstp, argp->xdrgen.share.caller_name, true);
+	if (!host)
+		goto out;
 
-	/* Obtain client and file */
-	locks_init_lock(&lock->fl);
-	lock->svid = ~(u32)0;
-	resp->status = nlm4svc_retrieve_args(rqstp, argp, &host, &file);
-	if (resp->status)
-		return resp->status == nlm__int__drop_reply ?
-			rpc_drop_reply : rpc_success;
+	resp->xdrgen.stat = nlm4svc_lookup_file(rqstp, host, lock, &file,
+						&xdr_lock, F_RDLCK);
+	if (resp->xdrgen.stat)
+		goto out;
 
-	/* Now try to unshare the file */
-	resp->status = nlmsvc_unshare_file(host, file, &lock->oh);
+	resp->xdrgen.stat = nlmsvc_unshare_file(host, file, &lock->oh);
 
-	dprintk("lockd: UNSHARE       status %d\n", ntohl(resp->status));
 	nlmsvc_release_lockowner(lock);
+
+out:
+	if (file)
+		nlm_release_file(file);
 	nlmsvc_release_host(host);
-	nlm_release_file(file);
-	return rpc_success;
+	return resp->xdrgen.stat == nlm__int__drop_reply ?
+		rpc_drop_reply : rpc_success;
 }
 
 /*
@@ -1419,15 +1445,15 @@ static const struct svc_procedure nlm4svc_procedures[24] = {
 		.pc_xdrressize	= NLM4_nlm4_shareres_sz,
 		.pc_name	= "SHARE",
 	},
-	[NLMPROC_UNSHARE] = {
-		.pc_func = nlm4svc_proc_unshare,
-		.pc_decode = nlm4svc_decode_shareargs,
-		.pc_encode = nlm4svc_encode_shareres,
-		.pc_argsize = sizeof(struct nlm_args),
-		.pc_argzero = sizeof(struct nlm_args),
-		.pc_ressize = sizeof(struct nlm_res),
-		.pc_xdrressize = Ck+St+1,
-		.pc_name = "UNSHARE",
+	[NLMPROC4_UNSHARE] = {
+		.pc_func	= nlm4svc_proc_unshare,
+		.pc_decode	= nlm4_svc_decode_nlm4_shareargs,
+		.pc_encode	= nlm4_svc_encode_nlm4_shareres,
+		.pc_argsize	= sizeof(struct nlm4_shareargs_wrapper),
+		.pc_argzero	= 0,
+		.pc_ressize	= sizeof(struct nlm4_shareres_wrapper),
+		.pc_xdrressize	= NLM4_nlm4_shareres_sz,
+		.pc_name	= "UNSHARE",
 	},
 	[NLMPROC_NM_LOCK] = {
 		.pc_func = nlm4svc_proc_nm_lock,
-- 
2.53.0