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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

net/sunrpc/svc_xprt.c

+4 −0
Original line number Diff line number Diff line
@@ -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);

}

net/sunrpc/xprt.c

+1 −1
Original line number Diff line number Diff line
@@ -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 @@ struct rpc_xprt *xprt_create_transport(struct xprt_create *args) 
		return xprt;

	}



	kref_init(&xprt->kref);

	spin_lock_init(&xprt->transport_lock);

	spin_lock_init(&xprt->reserve_lock);

net/sunrpc/xprtsock.c

+24 −10
Original line number Diff line number Diff line
@@ -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);