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Commit 40b00b6b authored by Trond Myklebust's avatar Trond Myklebust
Browse files

SUNRPC: Add a helper to switch the transport of an rpc_clnt 



Add an RPC client API to redirect an rpc_clnt's transport from a
source server to a destination server during a migration event.

Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
[ cel: forward ported to 3.12 ]
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent d746e545

include/linux/sunrpc/clnt.h

+4 −0
Original line number Diff line number Diff line
@@ -136,6 +136,10 @@ void rpc_task_reset_client(struct rpc_task *task, struct rpc_clnt *clnt); 
struct rpc_clnt *rpc_clone_client(struct rpc_clnt *);

struct rpc_clnt *rpc_clone_client_set_auth(struct rpc_clnt *,

				rpc_authflavor_t);

int		rpc_switch_client_transport(struct rpc_clnt *,

				struct xprt_create *,

				const struct rpc_timeout *);



void		rpc_shutdown_client(struct rpc_clnt *);

void		rpc_release_client(struct rpc_clnt *);

void		rpc_task_release_client(struct rpc_task *);

net/sunrpc/clnt.c

+100 −7
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
#include <linux/namei.h>

#include <linux/mount.h>

#include <linux/slab.h>

#include <linux/rcupdate.h>

#include <linux/utsname.h>

#include <linux/workqueue.h>

#include <linux/in.h>
@@ -264,6 +265,25 @@ void rpc_clients_notifier_unregister(void) 
	return rpc_pipefs_notifier_unregister(&rpc_clients_block);

}



static struct rpc_xprt *rpc_clnt_set_transport(struct rpc_clnt *clnt,

		struct rpc_xprt *xprt,

		const struct rpc_timeout *timeout)

{

	struct rpc_xprt *old;



	spin_lock(&clnt->cl_lock);

	old = clnt->cl_xprt;



	if (!xprt_bound(xprt))

		clnt->cl_autobind = 1;



	clnt->cl_timeout = timeout;

	rcu_assign_pointer(clnt->cl_xprt, xprt);

	spin_unlock(&clnt->cl_lock);



	return old;

}



static void rpc_clnt_set_nodename(struct rpc_clnt *clnt, const char *nodename)

{

	clnt->cl_nodelen = strlen(nodename);
@@ -339,6 +359,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, 
	const struct rpc_program *program = args->program;

	const struct rpc_version *version;

	struct rpc_clnt *clnt = NULL;

	const struct rpc_timeout *timeout;

	int err;



	/* sanity check the name before trying to print it */
@@ -366,7 +387,6 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, 
	if (err)

		goto out_no_clid;



	rcu_assign_pointer(clnt->cl_xprt, xprt);

	clnt->cl_procinfo = version->procs;

	clnt->cl_maxproc  = version->nrprocs;

	clnt->cl_prog     = args->prognumber ? : program->number;
@@ -381,16 +401,15 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, 
	INIT_LIST_HEAD(&clnt->cl_tasks);

	spin_lock_init(&clnt->cl_lock);



	if (!xprt_bound(xprt))

		clnt->cl_autobind = 1;



	clnt->cl_timeout = xprt->timeout;

	timeout = xprt->timeout;

	if (args->timeout != NULL) {

		memcpy(&clnt->cl_timeout_default, args->timeout,

				sizeof(clnt->cl_timeout_default));

		clnt->cl_timeout = &clnt->cl_timeout_default;

		timeout = &clnt->cl_timeout_default;

	}



	rpc_clnt_set_transport(clnt, xprt, timeout);



	clnt->cl_rtt = &clnt->cl_rtt_default;

	rpc_init_rtt(&clnt->cl_rtt_default, clnt->cl_timeout->to_initval);
@@ -601,6 +620,80 @@ rpc_clone_client_set_auth(struct rpc_clnt *clnt, rpc_authflavor_t flavor) 
}

EXPORT_SYMBOL_GPL(rpc_clone_client_set_auth);



/**

 * rpc_switch_client_transport: switch the RPC transport on the fly

 * @clnt: pointer to a struct rpc_clnt

 * @args: pointer to the new transport arguments

 * @timeout: pointer to the new timeout parameters

 *

 * This function allows the caller to switch the RPC transport for the

 * rpc_clnt structure 'clnt' to allow it to connect to a mirrored NFS

 * server, for instance.  It assumes that the caller has ensured that

 * there are no active RPC tasks by using some form of locking.

 *

 * Returns zero if "clnt" is now using the new xprt.  Otherwise a

 * negative errno is returned, and "clnt" continues to use the old

 * xprt.

 */

int rpc_switch_client_transport(struct rpc_clnt *clnt,

		struct xprt_create *args,

		const struct rpc_timeout *timeout)

{

	const struct rpc_timeout *old_timeo;

	rpc_authflavor_t pseudoflavor;

	struct rpc_xprt *xprt, *old;

	struct rpc_clnt *parent;

	int err;



	xprt = xprt_create_transport(args);

	if (IS_ERR(xprt)) {

		dprintk("RPC:       failed to create new xprt for clnt %p\n",

			clnt);

		return PTR_ERR(xprt);

	}



	pseudoflavor = clnt->cl_auth->au_flavor;



	old_timeo = clnt->cl_timeout;

	old = rpc_clnt_set_transport(clnt, xprt, timeout);



	rpc_unregister_client(clnt);

	__rpc_clnt_remove_pipedir(clnt);



	/*

	 * A new transport was created.  "clnt" therefore

	 * becomes the root of a new cl_parent tree.  clnt's

	 * children, if it has any, still point to the old xprt.

	 */

	parent = clnt->cl_parent;

	clnt->cl_parent = clnt;



	/*

	 * The old rpc_auth cache cannot be re-used.  GSS

	 * contexts in particular are between a single

	 * client and server.

	 */

	err = rpc_client_register(clnt, pseudoflavor, NULL);

	if (err)

		goto out_revert;



	synchronize_rcu();

	if (parent != clnt)

		rpc_release_client(parent);

	xprt_put(old);

	dprintk("RPC:       replaced xprt for clnt %p\n", clnt);

	return 0;



out_revert:

	rpc_clnt_set_transport(clnt, old, old_timeo);

	clnt->cl_parent = parent;

	rpc_client_register(clnt, pseudoflavor, NULL);

	xprt_put(xprt);

	dprintk("RPC:       failed to switch xprt for clnt %p\n", clnt);

	return err;

}

EXPORT_SYMBOL_GPL(rpc_switch_client_transport);



/*

 * Kill all tasks for the given client.

 * XXX: kill their descendants as well?