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rpc: keep backchannel xprt as long as server connection

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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>
This commit is contained in:
J. Bruce Fields
2010-12-08 12:45:44 -05:00
parent d75faea330
commit 99de8ea962
3 changed files with 29 additions and 11 deletions
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34
net/sunrpc/xprtsock.c
View File

@@ -2375,16 +2375,6 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
xprt->reestablish_timeout = 0;
xprt->idle_timeout = 0;
/*
* The backchannel uses the same socket connection as the
* forechannel
*/
args->bc_xprt->xpt_bc_xprt = xprt;
xprt->bc_xprt = args->bc_xprt;
bc_sock = container_of(args->bc_xprt, struct svc_sock, sk_xprt);
transport->sock = bc_sock->sk_sock;
transport->inet = bc_sock->sk_sk;
xprt->ops = &bc_tcp_ops;
switch (addr->sa_family) {
@@ -2406,6 +2396,29 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
xprt->address_strings[RPC_DISPLAY_PORT],
xprt->address_strings[RPC_DISPLAY_PROTO]);
/*
* The backchannel uses the same socket connection as the
* forechannel
*/
if (args->bc_xprt->xpt_bc_xprt) {
/* XXX: actually, want to catch this case... */
ret = ERR_PTR(-EINVAL);
goto out_err;
}
/*
* Once we've associated a backchannel xprt with a connection,
* we want to keep it around as long as long as the connection
* lasts, in case we need to start using it for a backchannel
* again; this reference won't be dropped until bc_xprt is
* destroyed.
*/
xprt_get(xprt);
args->bc_xprt->xpt_bc_xprt = xprt;
xprt->bc_xprt = args->bc_xprt;
bc_sock = container_of(args->bc_xprt, struct svc_sock, sk_xprt);
transport->sock = bc_sock->sk_sock;
transport->inet = bc_sock->sk_sk;
/*
* Since we don't want connections for the backchannel, we set
* the xprt status to connected
@@ -2415,6 +2428,7 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
if (try_module_get(THIS_MODULE))
return xprt;
xprt_put(xprt);
ret = ERR_PTR(-EINVAL);
out_err:
xprt_free(xprt);