From: J. Bruce Fields <bfields@redhat.com>
Date: Tue, 17 May 2016 16:38:21 +0000 (-0400)
Subject: rpc: share one xps between all backchannels
X-Git-Tag: v4.7-rc4~18^2~3
X-Git-Url: http://git.cascardo.eti.br/?a=commitdiff_plain;h=39a9beab5acb83176e8b9a4f0778749a09341f1f;p=cascardo%2Flinux.git

rpc: share one xps between all backchannels

The spec allows backchannels for multiple clients to share the same tcp
connection.  When that happens, we need to use the same xprt for all of
them.  Similarly, we need the same xps.

This fixes list corruption introduced by the multipath code.

Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: Trond Myklebust <trondmy@primarydata.com>
---

diff --git a/include/linux/sunrpc/svc_xprt.h b/include/linux/sunrpc/svc_xprt.h
index b7dabc4baafd..79ba50856707 100644
--- a/include/linux/sunrpc/svc_xprt.h
+++ b/include/linux/sunrpc/svc_xprt.h
@@ -84,6 +84,7 @@ struct svc_xprt {
 
 	struct net		*xpt_net;
 	struct rpc_xprt		*xpt_bc_xprt;	/* NFSv4.1 backchannel */
+	struct rpc_xprt_switch	*xpt_bc_xps;	/* NFSv4.1 backchannel */
 };
 
 static inline void unregister_xpt_user(struct svc_xprt *xpt, struct svc_xpt_user *u)
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 5aa3834619a8..5e3e1b63dbb3 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -297,6 +297,7 @@ struct xprt_create {
 	size_t			addrlen;
 	const char		*servername;
 	struct svc_xprt		*bc_xprt;	/* NFSv4.1 backchannel */
+	struct rpc_xprt_switch	*bc_xps;
 	unsigned int		flags;
 };
 
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index b33721d41adc..2808d550d273 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -452,10 +452,20 @@ static struct rpc_clnt *rpc_create_xprt(struct rpc_create_args *args,
 	struct rpc_clnt *clnt = NULL;
 	struct rpc_xprt_switch *xps;
 
-	xps = xprt_switch_alloc(xprt, GFP_KERNEL);
-	if (xps == NULL) {
-		xprt_put(xprt);
-		return ERR_PTR(-ENOMEM);
+	if (args->bc_xprt && args->bc_xprt->xpt_bc_xps) {
+		WARN_ON(args->protocol != XPRT_TRANSPORT_BC_TCP);
+		xps = args->bc_xprt->xpt_bc_xps;
+		xprt_switch_get(xps);
+	} else {
+		xps = xprt_switch_alloc(xprt, GFP_KERNEL);
+		if (xps == NULL) {
+			xprt_put(xprt);
+			return ERR_PTR(-ENOMEM);
+		}
+		if (xprt->bc_xprt) {
+			xprt_switch_get(xps);
+			xprt->bc_xprt->xpt_bc_xps = xps;
+		}
 	}
 	clnt = rpc_new_client(args, xps, xprt, NULL);
 	if (IS_ERR(clnt))
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index f5572e31d518..4f01f63102ee 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -136,6 +136,8 @@ static void svc_xprt_free(struct kref *kref)
 	/* See comment on corresponding get in xs_setup_bc_tcp(): */
 	if (xprt->xpt_bc_xprt)
 		xprt_put(xprt->xpt_bc_xprt);
+	if (xprt->xpt_bc_xps)
+		xprt_switch_put(xprt->xpt_bc_xps);
 	xprt->xpt_ops->xpo_free(xprt);
 	module_put(owner);
 }
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 2d3e0c42361e..7e2b2fa189c3 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -3057,6 +3057,7 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
 		return xprt;
 
 	args->bc_xprt->xpt_bc_xprt = NULL;
+	args->bc_xprt->xpt_bc_xps = NULL;
 	xprt_put(xprt);
 	ret = ERR_PTR(-EINVAL);
 out_err: