SUNRPC: report local rpcbind calls that get no answer

A caller that creates many listeners in one operation calls svc_register()
once for each of them. Every call waits for the local rpcbind on its own,
so a rpcbind that never answers costs the caller one timeout per listener.
The caller has no way to learn that the first call already failed.

Split rpcb_register_call() failures by whether rpcbind answered:

 - answered: a FALSE reply, or an RPC-level rejection that
   rpc_decode_header() derives from the reply. -EACCES (FALSE reply or
   AUTH_ERROR), -EPROTONOSUPPORT, -EPFNOSUPPORT, -EOPNOTSUPP.
 - never sent: -ENOMEM, -EMSGSIZE, -ERESTARTSYS.
 - no answer: everything else, i.e. transport errors.

Any no-answer error gets represented by -EIO, which is already what the
RPC layer reports for most of it: rpc_check_timeout() returns -EIO for a
soft timeout without RPC_TASK_TIMEOUT, and call_status() documents -EIO
as "shutdown or soft timeout".

Keep a count of the number of rpcbind failures in the serv. Later
patches will use that to watch for hard rpcbind failures, and alter
their behavior accordingly.

Assisted-by: LLM
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260901-nfsd-nl-hang-v5-6-a540d86668b0@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

2 files changed, 7 insertions, 3 deletions

diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index 3c2b8c355ab3..30344c0d6a9d 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -199,7 +199,8 @@ struct rpc_xprt	*rpc_task_get_xprt(struct rpc_clnt *clnt,
 
 int		rpcb_create_local(struct net *);
 void		rpcb_put_local(struct net *);
-int		rpcb_register(struct net *, u32, u32, int, unsigned short);
+int		rpcb_register(struct net *net, u32 prog, u32 vers, int prot,
+			      unsigned short port);
 int		rpcb_v4_register(struct net *net, const u32 program,
 				 const u32 version,
 				 const struct sockaddr *address,
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 2db1b9ec5658..5fa9417e034d 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -78,6 +78,7 @@ struct svc_serv {
 	unsigned int		sv_max_payload;	/* datagram payload size */
 	unsigned int		sv_max_mesg;	/* max_payload + 1 page for overheads */
 	unsigned int		sv_xdrsize;	/* XDR buffer size */
+	atomic_t		sv_rpcb_failures; /* unanswered rpcbind calls */
 	struct list_head	sv_permsocks;	/* all permanent sockets */
 	struct list_head	sv_tempsocks;	/* all temporary sockets */
 	int			sv_tmpcnt;	/* count of temporary "valid" sockets */
@@ -451,6 +452,7 @@ int sunrpc_set_pool_mode(const char *val);
 int sunrpc_get_pool_mode(char *val, size_t size);
 void svc_rpcb_cleanup(struct svc_serv *serv, struct net *net);
 int svc_bind(struct svc_serv *serv, struct net *net);
+unsigned int svc_rpcb_failure_count(struct svc_serv *serv);
 struct svc_serv *svc_create(struct svc_program *, unsigned int,
 			    int (*threadfn)(void *data));
 bool		   svc_rqst_replace_page(struct svc_rqst *rqstp,
@@ -471,8 +473,9 @@ unsigned int	   svc_serv_maxthreads(const struct svc_serv *serv);
 int		   svc_pool_stats_open(struct svc_info *si, struct file *file);
 void		   svc_process(struct svc_rqst *rqstp);
 void		   svc_process_bc(struct rpc_rqst *req, struct svc_rqst *rqstp);
-int		   svc_register(const struct svc_serv *, struct net *, const int,
-				const unsigned short, const unsigned short);
+int		   svc_register(struct svc_serv *serv, struct net *net,
+				const int family, const unsigned short proto,
+				const unsigned short port);
 
 void		   svc_wake_up(struct svc_serv *);
 void		   svc_reserve(struct svc_rqst *rqstp, int space);