rxrpc: Use IDR to allocate client conn IDs on a machine-wide basis

Use the IDR facility to allocate client connection IDs on a machine-wide
basis so that each client connection has a unique identifier.  When the
connection ID space wraps, we advance the epoch by 1, thereby effectively
having a 62-bit ID space.  The IDR facility is then used to look up client
connections during incoming packet routing instead of using an rbtree
rooted on the transport.

This change allows for the removal of the transport in the future and also
means that client connections can be looked up directly in the data-ready
handler by connection ID.

The ID management code is placed in a new file, conn-client.c, to which all
the client connection-specific code will eventually move.

Note that the IDR tree gets very expensive on memory if the connection IDs
are widely scattered throughout the number space, so we shall need to
retire connections that have, say, an ID more than four times the maximum
number of client conns away from the current allocation point to try and
keep the IDs concentrated.  We will also need to retire connections from an
old epoch.

Also note that, for the moment, a pointer to the transport has to be passed
through into the ID allocation function so that we can take a BH lock to
prevent a locking issue against in-BH lookup of client connections.  This
will go away later when RCU is used for server connections also.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 60ba22f56957..89966508b26c 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -233,7 +233,6 @@ struct rxrpc_transport {
 	struct rxrpc_local	*local;		/* local transport endpoint */
 	struct rxrpc_peer	*peer;		/* remote transport endpoint */
 	struct rb_root		bundles;	/* client connection bundles on this transport */
-	struct rb_root		client_conns;	/* client connections on this transport */
 	struct rb_root		server_conns;	/* server connections on this transport */
 	struct list_head	link;		/* link in master session list */
 	unsigned long		put_time;	/* time at which to reap */
@@ -241,7 +240,6 @@ struct rxrpc_transport {
 	rwlock_t		conn_lock;	/* lock for active/dead connections */
 	atomic_t		usage;
 	int			debug_id;	/* debug ID for printks */
-	unsigned int		conn_idcounter;	/* connection ID counter (client) */
 };
 
 /*
@@ -312,6 +310,8 @@ struct rxrpc_connection {
 	struct key		*server_key;	/* security for this service */
 	struct crypto_skcipher	*cipher;	/* encryption handle */
 	struct rxrpc_crypt	csum_iv;	/* packet checksum base */
+	unsigned long		flags;
+#define RXRPC_CONN_HAS_IDR	0		/* - Has a client conn ID assigned */
 	unsigned long		events;
 #define RXRPC_CONN_CHALLENGE	0		/* send challenge packet */
 	unsigned long		put_time;	/* time at which to reap */
@@ -551,6 +551,15 @@ void __rxrpc_put_call(struct rxrpc_call *);
 void __exit rxrpc_destroy_all_calls(void);
 
 /*
+ * conn_client.c
+ */
+extern struct idr rxrpc_client_conn_ids;
+
+int rxrpc_get_client_connection_id(struct rxrpc_connection *,
+				   struct rxrpc_transport *, gfp_t);
+void rxrpc_put_client_connection_id(struct rxrpc_connection *);
+
+/*
  * conn_event.c
  */
 void rxrpc_process_connection(struct work_struct *);