Commit 99de8ea9 authored by J. Bruce Fields's avatar J. Bruce Fields
Browse files

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: default avatarJ. Bruce Fields <bfields@redhat.com>
parent d75faea3
......@@ -13,6 +13,7 @@
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/svc_xprt.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/sunrpc/xprt.h>
#define RPCDBG_FACILITY RPCDBG_SVCXPRT
......@@ -128,6 +129,9 @@ static void svc_xprt_free(struct kref *kref)
if (test_bit(XPT_CACHE_AUTH, &xprt->xpt_flags))
svcauth_unix_info_release(xprt);
put_net(xprt->xpt_net);
/* See comment on corresponding get in xs_setup_bc_tcp(): */
if (xprt->xpt_bc_xprt)
xprt_put(xprt->xpt_bc_xprt);
xprt->xpt_ops->xpo_free(xprt);
module_put(owner);
}
......
......@@ -965,6 +965,7 @@ struct rpc_xprt *xprt_alloc(struct net *net, int size, int max_req)
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 @@ found:
return xprt;
}
kref_init(&xprt->kref);
spin_lock_init(&xprt->transport_lock);
spin_lock_init(&xprt->reserve_lock);
......
......@@ -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);
......
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