rpc: keep backchannel xprt as long as server connection
Multiple backchannels can share the same tcp connection; from rfc 5661 section
2.10.3.1:
A connection's association with a session is not exclusive. A
connection associated with the channel(s) of one session may be
simultaneously associated with the channel(s) of other sessions
including sessions associated with other client IDs.
However, multiple backchannels share a connection, they must all share
the same xid stream (hence the same rpc_xprt); the only way we have to
match replies with calls at the rpc layer is using the xid.
So, keep the rpc_xprt around as long as the connection lasts, in case
we're asked to use the connection as a backchannel again.
Requests to create new backchannel clients over a given server
connection should results in creating new clients that reuse the
existing rpc_xprt.
But to start, just reject attempts to associate multiple rpc_xprt's with
the same underlying bc_xprt.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 4c8f18a..749ad15 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -965,6 +965,7 @@
xprt = kzalloc(size, GFP_KERNEL);
if (xprt == NULL)
goto out;
+ kref_init(&xprt->kref);
xprt->max_reqs = max_req;
xprt->slot = kcalloc(max_req, sizeof(struct rpc_rqst), GFP_KERNEL);
@@ -1102,7 +1103,6 @@
return xprt;
}
- kref_init(&xprt->kref);
spin_lock_init(&xprt->transport_lock);
spin_lock_init(&xprt->reserve_lock);