[PATCH v4 06/14] SUNRPC: report local rpcbind calls that get no answer
From: Jeff Layton
Date: Mon Aug 31 2026 - 14:31:36 EST
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@xxxxxxxxxx>
---
include/linux/sunrpc/clnt.h | 3 ++-
include/linux/sunrpc/svc.h | 7 +++++--
net/sunrpc/rpcb_clnt.c | 21 ++++++++++++++++++---
net/sunrpc/svc.c | 42 +++++++++++++++++++++++++++++++++++++++++-
4 files changed, 66 insertions(+), 7 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);
diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
index 0aa376b82a52..50169ee12bd8 100644
--- a/net/sunrpc/rpcb_clnt.c
+++ b/net/sunrpc/rpcb_clnt.c
@@ -412,7 +412,8 @@ static struct rpc_clnt *rpcb_create(struct net *net, const char *nodename,
return rpc_create(&args);
}
-static int rpcb_register_call(struct sunrpc_net *sn, struct rpc_clnt *clnt, struct rpc_message *msg, bool is_set)
+static int rpcb_register_call(struct sunrpc_net *sn, struct rpc_clnt *clnt,
+ struct rpc_message *msg, bool is_set)
{
int flags = RPC_TASK_NOCONNECT;
int error, result = 0;
@@ -422,8 +423,22 @@ static int rpcb_register_call(struct sunrpc_net *sn, struct rpc_clnt *clnt, stru
msg->rpc_resp = &result;
error = rpc_call_sync(clnt, msg, flags);
- if (error < 0)
- return error;
+ if (error < 0) {
+ switch (error) {
+ /* rpcbind answered; the reply itself carries the error */
+ case -EPROTONOSUPPORT:
+ case -EPFNOSUPPORT:
+ case -EOPNOTSUPP:
+ case -EACCES:
+ /* the call never made it onto the wire */
+ case -ENOMEM:
+ case -EMSGSIZE:
+ case -ERESTARTSYS:
+ return error;
+ }
+ /* anything else, we assume that rpcbind isn't functional */
+ return -EIO;
+ }
if (!result)
return -EACCES;
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 4f402bbf97ba..ca6f90653327 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1179,10 +1179,40 @@ int svc_generic_rpcbind_set(struct net *net,
error = svc_rpcbind_set_version(net, progp, version,
family, proto, port);
+ /* -EIO means no answer, not a refusal, so vs_rpcb_optnl must keep it. */
+ if (error == -EIO)
+ return error;
+
return (vers->vs_rpcb_optnl) ? 0 : error;
}
EXPORT_SYMBOL_GPL(svc_generic_rpcbind_set);
+/**
+ * svc_rpcb_failure_count - local rpcbind calls for @serv that got no answer
+ * @serv: RPC service to query
+ *
+ * svc_register() adds one for each of its calls that got no answer. A reply
+ * that refuses one entry does not count, because rpcbind answered and the
+ * next entry may still succeed.
+ *
+ * The count is kept per serv rather than per net. The local rpcbind client
+ * is per-net and lockd shares it, but a count that another service can move
+ * says nothing about this serv's own calls.
+ *
+ * This is for callers that cannot see the svc_register() return, because a
+ * transport class sits in between. Such a caller reads the count before it
+ * starts and compares as it goes, so there is no state to reset between
+ * operations. The count never resets, and callers must not attach meaning
+ * to the value itself.
+ *
+ * Return: the number of unanswered calls since this serv was created.
+ */
+unsigned int svc_rpcb_failure_count(struct svc_serv *serv)
+{
+ return atomic_read(&serv->sv_rpcb_failures);
+}
+EXPORT_SYMBOL_GPL(svc_rpcb_failure_count);
+
/**
* svc_register - register an RPC service with the local portmapper
* @serv: svc_serv struct for the service to register
@@ -1193,10 +1223,11 @@ EXPORT_SYMBOL_GPL(svc_generic_rpcbind_set);
*
* Service is registered for any address in the passed-in protocol family
*/
-int svc_register(const struct svc_serv *serv, struct net *net,
+int svc_register(struct svc_serv *serv, struct net *net,
const int family, const unsigned short proto,
const unsigned short port)
{
+ bool noanswer = false;
unsigned int p, i;
int error = 0;
@@ -1208,10 +1239,16 @@ int svc_register(const struct svc_serv *serv, struct net *net,
struct svc_program *progp = &serv->sv_programs[p];
for (i = 0; i < progp->pg_nvers; i++) {
+ const struct svc_version *vers = progp->pg_vers[i];
int ret;
ret = progp->pg_rpcbind_set(net, progp, i,
family, proto, port);
+ if (ret == -EIO) {
+ noanswer = true;
+ if (vers && vers->vs_rpcb_optnl)
+ ret = 0;
+ }
if (ret < 0) {
printk(KERN_WARNING "svc: failed to register "
"%sv%u RPC service (errno %d).\n",
@@ -1223,6 +1260,9 @@ int svc_register(const struct svc_serv *serv, struct net *net,
}
}
+ if (noanswer)
+ atomic_inc(&serv->sv_rpcb_failures);
+
return error;
}
--
2.55.0