2 files changed, 20 insertions, 7 deletions

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 3afe7fb403b2..3435d24bfe55 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -58,10 +58,13 @@ struct svc_serv {
         struct svc_stat *       sv_stats;       /* RPC statistics */
         spinlock_t              sv_lock;
         unsigned int            sv_nrthreads;   /* # of server threads */
+        unsigned int            sv_maxconn;     /* max connections allowed or
+                                                 * '0' causing max to be based
+                                                 * on number of threads. */
+
         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 */
-
         struct list_head        sv_permsocks;   /* all permanent sockets */
         struct list_head        sv_tempsocks;   /* all temporary sockets */
         int                     sv_tmpcnt;      /* count of temporary sockets */
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index bf5b5cdafebf..3fe4f1004278 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -515,8 +515,10 @@ int svc_port_is_privileged(struct sockaddr *sin)
 }
 
 /*
- * Make sure that we don't have too many active connections.  If we
- * have, something must be dropped.
+ * Make sure that we don't have too many active connections. If we have,
+ * something must be dropped. It's not clear what will happen if we allow
+ * "too many" connections, but when dealing with network-facing software,
+ * we have to code defensively. Here we do that by imposing hard limits.
  *
  * There's no point in trying to do random drop here for DoS
  * prevention. The NFS clients does 1 reconnect in 15 seconds. An
@@ -525,19 +527,27 @@ int svc_port_is_privileged(struct sockaddr *sin)
  * The only somewhat efficient mechanism would be if drop old
  * connections from the same IP first. But right now we don't even
  * record the client IP in svc_sock.
+ *
+ * single-threaded services that expect a lot of clients will probably
+ * need to set sv_maxconn to override the default value which is based
+ * on the number of threads
  */
 static void svc_check_conn_limits(struct svc_serv *serv)
 {
-        if (serv->sv_tmpcnt > (serv->sv_nrthreads+3)*20) {
+        unsigned int limit = serv->sv_maxconn ? serv->sv_maxconn :
+                                (serv->sv_nrthreads+3) * 20;
+
+        if (serv->sv_tmpcnt > limit) {
                 struct svc_xprt *xprt = NULL;
                 spin_lock_bh(&serv->sv_lock);
                 if (!list_empty(&serv->sv_tempsocks)) {
                         if (net_ratelimit()) {
                                 /* Try to help the admin */
                                 printk(KERN_NOTICE "%s: too many open  "
-                                       "connections, consider increasing the "
-                                       "number of nfsd threads\n",
-                                       serv->sv_name);
+                                       "connections, consider increasing %s\n",
+                                       serv->sv_name, serv->sv_maxconn ?
+                                       "the max number of connections." :
+                                       "the number of threads.");
                         }
                         /*
                          * Always select the oldest connection. It's not fair,