Merge branch 'for-2.6.31' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6

df36b439 · Linus Torvalds <[email protected]> · 2009-06-22 12:53:06 -07:00

* 'for-2.6.31' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6: (128 commits)
  nfs41: sunrpc: xprt_alloc_bc_request() should not use spin_lock_bh()
  nfs41: Move initialization of nfs4_opendata seq_res to nfs4_init_opendata_res
  nfs: remove unnecessary NFS_INO_INVALID_ACL checks
  NFS: More "sloppy" parsing problems
  NFS: Invalid mount option values should always fail, even with "sloppy"
  NFS: Remove unused XDR decoder functions
  NFS: Update MNT and MNT3 reply decoding functions
  NFS: add XDR decoder for mountd version 3 auth-flavor lists
  NFS: add new file handle decoders to in-kernel mountd client
  NFS: Add separate mountd status code decoders for each mountd version
  NFS: remove unused function in fs/nfs/mount_clnt.c
  NFS: Use xdr_stream-based XDR encoder for MNT's dirpath argument
  NFS: Clean up MNT program definitions
  lockd: Don't bother with RPC ping for NSM upcalls
  lockd: Update NSM state from SM_MON replies
  NFS: Fix false error return from nfs_callback_up() if ipv6.ko is not available
  NFS: Return error code from nfs_callback_up() to user space
  NFS: Do not display the setting of the "intr" mount option
  NFS: add support for splice writes
  nfs41: Backchannel: CB_SEQUENCE validation
  ...

Commit: df36b439c5fedefe013d4449cb6a50d15e2f4d70
Parents: a9b011f5 · e9f02985

Merge commit. Changes below are compared with the first parent: a9b011f5.

Changes

49 files changed · +5220 −603

File	Status	Add	Del	Content
fs/lockd/clntproc.c	modified	+3	−1	View file
fs/lockd/mon.c	modified	+13	−6	View file
fs/nfs/Kconfig	modified	+9	−0	View file
fs/nfs/callback.c	modified	+182	−36	View file
fs/nfs/callback.h	modified	+61	−7	View file
fs/nfs/callback_proc.c	modified	+127	−0	View file
fs/nfs/callback_xdr.c	modified	+258	−22	View file
fs/nfs/client.c	modified	+166	−25	View file
fs/nfs/delegation.c	modified	+16	−16	View file
fs/nfs/direct.c	modified	+9	−0	View file
fs/nfs/file.c	modified	+31	−6	View file
fs/nfs/internal.h	modified	+70	−0	View file
fs/nfs/mount_clnt.c	modified	+295	−42	View file
fs/nfs/nfs3acl.c	modified	+0	−2	View file
fs/nfs/nfs4_fs.h	modified	+35	−2	View file
fs/nfs/nfs4proc.c	modified	+1289	−59	View file
fs/nfs/nfs4renewd.c	modified	+4	−2	View file
fs/nfs/nfs4state.c	modified	+162	−28	View file
fs/nfs/nfs4xdr.c	modified	+940	−132	View file
fs/nfs/nfsroot.c	modified	+5	−0	View file
fs/nfs/read.c	modified	+30	−3	View file
fs/nfs/super.c	modified	+177	−118	View file
fs/nfs/unlink.c	modified	+19	−1	View file
fs/nfs/write.c	modified	+29	−2	View file
include/linux/lockd/lockd.h	modified	+1	−1	View file
include/linux/nfs.h	modified	+3	−2	View file
include/linux/nfs2.h	modified	+0	−7	View file
include/linux/nfs3.h	modified	+0	−5	View file
include/linux/nfs4.h	modified	+18	−0	View file
include/linux/nfs_fs_sb.h	modified	+66	−1	View file
include/linux/nfs_xdr.h	modified	+171	−0	View file
include/linux/nfsd/state.h	modified	+0	−1	View file
include/linux/sunrpc/bc_xprt.h	added	+49	−0	View file
include/linux/sunrpc/clnt.h	modified	+1	−0	View file
include/linux/sunrpc/sched.h	modified	+3	−0	View file
include/linux/sunrpc/svc.h	modified	+11	−0	View file
include/linux/sunrpc/svcsock.h	modified	+2	−0	View file
include/linux/sunrpc/xprt.h	modified	+37	−1	View file
net/sunrpc/Makefile	modified	+1	−0	View file
net/sunrpc/backchannel_rqst.c	added	+281	−0	View file
net/sunrpc/bc_svc.c	added	+81	−0	View file
net/sunrpc/clnt.c	modified	+136	−7	View file
net/sunrpc/sched.c	modified	+1	−1	View file
net/sunrpc/stats.c	modified	+5	−3	View file
net/sunrpc/sunrpc.h	added	+37	−0	View file
net/sunrpc/svc.c	modified	+104	−30	View file
net/sunrpc/svcsock.c	modified	+39	−0	View file
net/sunrpc/xprt.c	modified	+46	−14	View file
net/sunrpc/xprtsock.c	modified	+197	−20	View file

Only the first 600 diff lines are shown. Download the complete patch.

fs/lockd/clntproc.c

View file

diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index dd79570..f2fdcbc 100644
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -126,7 +126,6 @@ static void nlmclnt_setlockargs(struct nlm_rqst *req, struct file_lock *fl)
 	struct nlm_lock	*lock = &argp->lock;
 
 	nlmclnt_next_cookie(&argp->cookie);
-	argp->state   = nsm_local_state;
 	memcpy(&lock->fh, NFS_FH(fl->fl_file->f_path.dentry->d_inode), sizeof(struct nfs_fh));
 	lock->caller  = utsname()->nodename;
 	lock->oh.data = req->a_owner;
@@ -165,6 +164,7 @@ int nlmclnt_proc(struct nlm_host *host, int cmd, struct file_lock *fl)
 	/* Set up the argument struct */
 	nlmclnt_setlockargs(call, fl);
 
+	lock_kernel();
 	if (IS_SETLK(cmd) || IS_SETLKW(cmd)) {
 		if (fl->fl_type != F_UNLCK) {
 			call->a_args.block = IS_SETLKW(cmd) ? 1 : 0;
@@ -178,6 +178,7 @@ int nlmclnt_proc(struct nlm_host *host, int cmd, struct file_lock *fl)
 
 	fl->fl_ops->fl_release_private(fl);
 	fl->fl_ops = NULL;
+	unlock_kernel();
 
 	dprintk("lockd: clnt proc returns %d\n", status);
 	return status;
@@ -519,6 +520,7 @@ nlmclnt_lock(struct nlm_rqst *req, struct file_lock *fl)
 
 	if (nsm_monitor(host) < 0)
 		goto out;
+	req->a_args.state = nsm_local_state;
 
 	fl->fl_flags |= FL_ACCESS;
 	status = do_vfs_lock(fl);

fs/lockd/mon.c

View file

diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
index 6d5d4a4..7fce1b5 100644
--- a/fs/lockd/mon.c
+++ b/fs/lockd/mon.c
@@ -53,7 +53,7 @@ static				DEFINE_SPINLOCK(nsm_lock);
 /*
  * Local NSM state
  */
-int	__read_mostly		nsm_local_state;
+u32	__read_mostly		nsm_local_state;
 int	__read_mostly		nsm_use_hostnames;
 
 static inline struct sockaddr *nsm_addr(const struct nsm_handle *nsm)
@@ -112,6 +112,7 @@ static struct rpc_clnt *nsm_create(void)
 		.program		= &nsm_program,
 		.version		= NSM_VERSION,
 		.authflavor		= RPC_AUTH_NULL,
+		.flags			= RPC_CLNT_CREATE_NOPING,
 	};
 
 	return rpc_create(&args);
@@ -184,13 +185,19 @@ int nsm_monitor(const struct nlm_host *host)
 	nsm->sm_mon_name = nsm_use_hostnames ? nsm->sm_name : nsm->sm_addrbuf;
 
 	status = nsm_mon_unmon(nsm, NSMPROC_MON, &res);
-	if (res.status != 0)
+	if (unlikely(res.status != 0))
 		status = -EIO;
-	if (status < 0)
+	if (unlikely(status < 0)) {
 		printk(KERN_NOTICE "lockd: cannot monitor %s\n", nsm->sm_name);
-	else
-		nsm->sm_monitored = 1;
-	return status;
+		return status;
+	}
+
+	nsm->sm_monitored = 1;
+	if (unlikely(nsm_local_state != res.state)) {
+		nsm_local_state = res.state;
+		dprintk("lockd: NSM state changed to %d\n", nsm_local_state);
+	}
+	return 0;
 }
 
 /**

fs/nfs/Kconfig

View file

diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
index e67f3ec..5d6d6f4 100644
--- a/fs/nfs/Kconfig
+++ b/fs/nfs/Kconfig
@@ -74,6 +74,15 @@ config NFS_V4
 
 	  If unsure, say N.
 
+config NFS_V4_1
+	bool "NFS client support for NFSv4.1 (DEVELOPER ONLY)"
+	depends on NFS_V4 && EXPERIMENTAL
+	help
+	  This option enables support for minor version 1 of the NFSv4 protocol
+	  (draft-ietf-nfsv4-minorversion1) in the kernel's NFS client.
+
+	  Unless you're an NFS developer, say N.
+
 config ROOT_NFS
 	bool "Root file system on NFS"
 	depends on NFS_FS=y && IP_PNP

fs/nfs/callback.c

View file

diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index a886e69..7f604c7 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -17,6 +17,9 @@
 #include <linux/freezer.h>
 #include <linux/kthread.h>
 #include <linux/sunrpc/svcauth_gss.h>
+#if defined(CONFIG_NFS_V4_1)
+#include <linux/sunrpc/bc_xprt.h>
+#endif
 
 #include <net/inet_sock.h>
 
@@ -28,11 +31,12 @@
 
 struct nfs_callback_data {
 	unsigned int users;
+	struct svc_serv *serv;
 	struct svc_rqst *rqst;
 	struct task_struct *task;
 };
 
-static struct nfs_callback_data nfs_callback_info;
+static struct nfs_callback_data nfs_callback_info[NFS4_MAX_MINOR_VERSION + 1];
 static DEFINE_MUTEX(nfs_callback_mutex);
 static struct svc_program nfs4_callback_program;
 
@@ -56,10 +60,10 @@ module_param_call(callback_tcpport, param_set_port, param_get_int,
 		 &nfs_callback_set_tcpport, 0644);
 
 /*
- * This is the callback kernel thread.
+ * This is the NFSv4 callback kernel thread.
  */
 static int
-nfs_callback_svc(void *vrqstp)
+nfs4_callback_svc(void *vrqstp)
 {
 	int err, preverr = 0;
 	struct svc_rqst *rqstp = vrqstp;
@@ -97,20 +101,12 @@ nfs_callback_svc(void *vrqstp)
 }
 
 /*
- * Bring up the callback thread if it is not already up.
+ * Prepare to bring up the NFSv4 callback service
  */
-int nfs_callback_up(void)
+struct svc_rqst *
+nfs4_callback_up(struct svc_serv *serv)
 {
-	struct svc_serv *serv = NULL;
-	int ret = 0;
-
-	mutex_lock(&nfs_callback_mutex);
-	if (nfs_callback_info.users++ || nfs_callback_info.task != NULL)
-		goto out;
-	serv = svc_create(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE, NULL);
-	ret = -ENOMEM;
-	if (!serv)
-		goto out_err;
+	int ret;
 
 	ret = svc_create_xprt(serv, "tcp", PF_INET,
 				nfs_callback_set_tcpport, SVC_SOCK_ANONYMOUS);
@@ -127,27 +123,174 @@ int nfs_callback_up(void)
 		nfs_callback_tcpport6 = ret;
 		dprintk("NFS: Callback listener port = %u (af %u)\n",
 				nfs_callback_tcpport6, PF_INET6);
-	} else if (ret != -EAFNOSUPPORT)
+	} else if (ret == -EAFNOSUPPORT)
+		ret = 0;
+	else
 		goto out_err;
 #endif	/* defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) */
 
-	nfs_callback_info.rqst = svc_prepare_thread(serv, &serv->sv_pools[0]);
-	if (IS_ERR(nfs_callback_info.rqst)) {
-		ret = PTR_ERR(nfs_callback_info.rqst);
-		nfs_callback_info.rqst = NULL;
+	return svc_prepare_thread(serv, &serv->sv_pools[0]);
+
+out_err:
+	if (ret == 0)
+		ret = -ENOMEM;
+	return ERR_PTR(ret);
+}
+
+#if defined(CONFIG_NFS_V4_1)
+/*
+ * The callback service for NFSv4.1 callbacks
+ */
+static int
+nfs41_callback_svc(void *vrqstp)
+{
+	struct svc_rqst *rqstp = vrqstp;
+	struct svc_serv *serv = rqstp->rq_server;
+	struct rpc_rqst *req;
+	int error;
+	DEFINE_WAIT(wq);
+
+	set_freezable();
+
+	/*
+	 * FIXME: do we really need to run this under the BKL? If so, please
+	 * add a comment about what it's intended to protect.
+	 */
+	lock_kernel();
+	while (!kthread_should_stop()) {
+		prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_INTERRUPTIBLE);
+		spin_lock_bh(&serv->sv_cb_lock);
+		if (!list_empty(&serv->sv_cb_list)) {
+			req = list_first_entry(&serv->sv_cb_list,
+					struct rpc_rqst, rq_bc_list);
+			list_del(&req->rq_bc_list);
+			spin_unlock_bh(&serv->sv_cb_lock);
+			dprintk("Invoking bc_svc_process()\n");
+			error = bc_svc_process(serv, req, rqstp);
+			dprintk("bc_svc_process() returned w/ error code= %d\n",
+				error);
+		} else {
+			spin_unlock_bh(&serv->sv_cb_lock);
+			schedule();
+		}
+		finish_wait(&serv->sv_cb_waitq, &wq);
+	}
+	unlock_kernel();
+	return 0;
+}
+
+/*
+ * Bring up the NFSv4.1 callback service
+ */
+struct svc_rqst *
+nfs41_callback_up(struct svc_serv *serv, struct rpc_xprt *xprt)
+{
+	struct svc_xprt *bc_xprt;
+	struct svc_rqst *rqstp = ERR_PTR(-ENOMEM);
+
+	dprintk("--> %s\n", __func__);
+	/* Create a svc_sock for the service */
+	bc_xprt = svc_sock_create(serv, xprt->prot);
+	if (!bc_xprt)
+		goto out;
+
+	/*
+	 * Save the svc_serv in the transport so that it can
+	 * be referenced when the session backchannel is initialized
+	 */
+	serv->bc_xprt = bc_xprt;
+	xprt->bc_serv = serv;
+
+	INIT_LIST_HEAD(&serv->sv_cb_list);
+	spin_lock_init(&serv->sv_cb_lock);
+	init_waitqueue_head(&serv->sv_cb_waitq);
+	rqstp = svc_prepare_thread(serv, &serv->sv_pools[0]);
+	if (IS_ERR(rqstp))
+		svc_sock_destroy(bc_xprt);
+out:
+	dprintk("--> %s return %p\n", __func__, rqstp);
+	return rqstp;
+}
+
+static inline int nfs_minorversion_callback_svc_setup(u32 minorversion,
+		struct svc_serv *serv, struct rpc_xprt *xprt,
+		struct svc_rqst **rqstpp, int (**callback_svc)(void *vrqstp))
+{
+	if (minorversion) {
+		*rqstpp = nfs41_callback_up(serv, xprt);
+		*callback_svc = nfs41_callback_svc;
+	}
+	return minorversion;
+}
+
+static inline void nfs_callback_bc_serv(u32 minorversion, struct rpc_xprt *xprt,
+		struct nfs_callback_data *cb_info)
+{
+	if (minorversion)
+		xprt->bc_serv = cb_info->serv;
+}
+#else
+static inline int nfs_minorversion_callback_svc_setup(u32 minorversion,
+		struct svc_serv *serv, struct rpc_xprt *xprt,
+		struct svc_rqst **rqstpp, int (**callback_svc)(void *vrqstp))
+{
+	return 0;
+}
+
+static inline void nfs_callback_bc_serv(u32 minorversion, struct rpc_xprt *xprt,
+		struct nfs_callback_data *cb_info)
+{
+}
+#endif /* CONFIG_NFS_V4_1 */
+
+/*
+ * Bring up the callback thread if it is not already up.
+ */
+int nfs_callback_up(u32 minorversion, struct rpc_xprt *xprt)
+{
+	struct svc_serv *serv = NULL;
+	struct svc_rqst *rqstp;
+	int (*callback_svc)(void *vrqstp);
+	struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
+	char svc_name[12];
+	int ret = 0;
+	int minorversion_setup;
+
+	mutex_lock(&nfs_callback_mutex);
+	if (cb_info->users++ || cb_info->task != NULL) {
+		nfs_callback_bc_serv(minorversion, xprt, cb_info);
+		goto out;
+	}
+	serv = svc_create(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE, NULL);
+	if (!serv) {
+		ret = -ENOMEM;
+		goto out_err;
+	}
+
+	minorversion_setup =  nfs_minorversion_callback_svc_setup(minorversion,
+					serv, xprt, &rqstp, &callback_svc);
+	if (!minorversion_setup) {
+		/* v4.0 callback setup */
+		rqstp = nfs4_callback_up(serv);
+		callback_svc = nfs4_callback_svc;
+	}
+
+	if (IS_ERR(rqstp)) {
+		ret = PTR_ERR(rqstp);
 		goto out_err;
 	}
 
 	svc_sock_update_bufs(serv);
 
-	nfs_callback_info.task = kthread_run(nfs_callback_svc,
-					     nfs_callback_info.rqst,
-					     "nfsv4-svc");
-	if (IS_ERR(nfs_callback_info.task)) {
-		ret = PTR_ERR(nfs_callback_info.task);
-		svc_exit_thread(nfs_callback_info.rqst);
-		nfs_callback_info.rqst = NULL;
-		nfs_callback_info.task = NULL;
+	sprintf(svc_name, "nfsv4.%u-svc", minorversion);
+	cb_info->serv = serv;
+	cb_info->rqst = rqstp;
+	cb_info->task = kthread_run(callback_svc, cb_info->rqst, svc_name);
+	if (IS_ERR(cb_info->task)) {
+		ret = PTR_ERR(cb_info->task);
+		svc_exit_thread(cb_info->rqst);
+		cb_info->rqst = NULL;
+		cb_info->task = NULL;
 		goto out_err;
 	}
 out:
@@ -164,22 +307,25 @@ out:
 out_err:
 	dprintk("NFS: Couldn't create callback socket or server thread; "
 		"err = %d\n", ret);
-	nfs_callback_info.users--;
+	cb_info->users--;
 	goto out;
 }
 
 /*
  * Kill the callback thread if it's no longer being used.
  */
-void nfs_callback_down(void)
+void nfs_callback_down(int minorversion)
 {
+	struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
+
 	mutex_lock(&nfs_callback_mutex);
-	nfs_callback_info.users--;
-	if (nfs_callback_info.users == 0 && nfs_callback_info.task != NULL) {
-		kthread_stop(nfs_callback_info.task);
-		svc_exit_thread(nfs_callback_info.rqst);
-		nfs_callback_info.rqst = NULL;
-		nfs_callback_info.task = NULL;
+	cb_info->users--;
+	if (cb_info->users == 0 && cb_info->task != NULL) {
+		kthread_stop(cb_info->task);
+		svc_exit_thread(cb_info->rqst);
+		cb_info->serv = NULL;
+		cb_info->rqst = NULL;
+		cb_info->task = NULL;
 	}
 	mutex_unlock(&nfs_callback_mutex);
 }

fs/nfs/callback.h

View file

diff --git a/fs/nfs/callback.h b/fs/nfs/callback.h
index e110e28..07baa82 100644
--- a/fs/nfs/callback.h
+++ b/fs/nfs/callback.h
@@ -20,13 +20,24 @@ enum nfs4_callback_procnum {
 enum nfs4_callback_opnum {
 	OP_CB_GETATTR = 3,
 	OP_CB_RECALL  = 4,
+/* Callback operations new to NFSv4.1 */
+	OP_CB_LAYOUTRECALL  = 5,
+	OP_CB_NOTIFY        = 6,
+	OP_CB_PUSH_DELEG    = 7,
+	OP_CB_RECALL_ANY    = 8,
+	OP_CB_RECALLABLE_OBJ_AVAIL = 9,
+	OP_CB_RECALL_SLOT   = 10,
+	OP_CB_SEQUENCE      = 11,
+	OP_CB_WANTS_CANCELLED = 12,
+	OP_CB_NOTIFY_LOCK   = 13,
+	OP_CB_NOTIFY_DEVICEID = 14,
 	OP_CB_ILLEGAL = 10044,
 };
 
 struct cb_compound_hdr_arg {
 	unsigned int taglen;
 	const char *tag;
-	unsigned int callback_ident;
+	unsigned int minorversion;
 	unsigned nops;
 };
 
@@ -59,16 +70,59 @@ struct cb_recallargs {
 	uint32_t truncate;
 };
 
+#if defined(CONFIG_NFS_V4_1)
+
+struct referring_call {
+	uint32_t			rc_sequenceid;
+	uint32_t			rc_slotid;
+};
+
+struct referring_call_list {
+	struct nfs4_sessionid		rcl_sessionid;
+	uint32_t			rcl_nrefcalls;
+	struct referring_call 		*rcl_refcalls;
+};
+
+struct cb_sequenceargs {
+	struct sockaddr			*csa_addr;
+	struct nfs4_sessionid		csa_sessionid;
+	uint32_t			csa_sequenceid;
+	uint32_t			csa_slotid;
+	uint32_t			csa_highestslotid;
+	uint32_t			csa_cachethis;
+	uint32_t			csa_nrclists;
+	struct referring_call_list	*csa_rclists;
+};
+
+struct cb_sequenceres {
+	__be32				csr_status;
+	struct nfs4_sessionid		csr_sessionid;
+	uint32_t			csr_sequenceid;
+	uint32_t			csr_slotid;
+	uint32_t			csr_highestslotid;
+	uint32_t			csr_target_highestslotid;
+};
+
+extern unsigned nfs4_callback_sequence(struct cb_sequenceargs *args,
+				       struct cb_sequenceres *res);
+
+#endif /* CONFIG_NFS_V4_1 */
+
 extern __be32 nfs4_callback_getattr(struct cb_getattrargs *args, struct cb_getattrres *res);
 extern __be32 nfs4_callback_recall(struct cb_recallargs *args, void *dummy);
 
 #ifdef CONFIG_NFS_V4
-extern int nfs_callback_up(void);
-extern void nfs_callback_down(void);
-#else
-#define nfs_callback_up()	(0)
-#define nfs_callback_down()	do {} while(0)
-#endif
+extern int nfs_callback_up(u32 minorversion, struct rpc_xprt *xprt);
+extern void nfs_callback_down(int minorversion);
+#endif /* CONFIG_NFS_V4 */
+
+/*
+ * nfs41: Callbacks are expected to not cause substantial latency,
+ * so we limit their concurrency to 1 by setting up the maximum number
+ * of slots for the backchannel.
+ */
+#define NFS41_BC_MIN_CALLBACKS 1
+#define NFS41_BC_MAX_CALLBACKS 1
 
 extern unsigned int nfs_callback_set_tcpport;
 extern unsigned short nfs_callback_tcpport;

fs/nfs/callback_proc.c

View file

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index f7e83e2..b7da1f5 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -101,3 +101,130 @@ out:
 	dprintk("%s: exit with status = %d\n", __func__, ntohl(res));
 	return res;
 }
+
+#if defined(CONFIG_NFS_V4_1)
+
+/*
+ * Validate the sequenceID sent by the server.
+ * Return success if the sequenceID is one more than what we last saw on
+ * this slot, accounting for wraparound.  Increments the slot's sequence.
+ *
+ * We don't yet implement a duplicate request cache, so at this time
+ * we will log replays, and process them as if we had not seen them before,
+ * but we don't bump the sequence in the slot.  Not too worried about it,
+ * since we only currently implement idempotent callbacks anyway.
+ *
+ * We have a single slot backchannel at this time, so we don't bother
+ * checking the used_slots bit array on the table.  The lower layer guarantees
+ * a single outstanding callback request at a time.
+ */
+static int
+validate_seqid(struct nfs4_slot_table *tbl, u32 slotid, u32 seqid)
+{
+	struct nfs4_slot *slot;
+
+	dprintk("%s enter. slotid %d seqid %d\n",
+		__func__, slotid, seqid);
+
+	if (slotid > NFS41_BC_MAX_CALLBACKS)
+		return htonl(NFS4ERR_BADSLOT);
+
+	slot = tbl->slots + slotid;
+	dprintk("%s slot table seqid: %d\n", __func__, slot->seq_nr);
+
+	/* Normal */
+	if (likely(seqid == slot->seq_nr + 1)) {
+		slot->seq_nr++;
+		return htonl(NFS4_OK);
+	}
+
+	/* Replay */
+	if (seqid == slot->seq_nr) {
+		dprintk("%s seqid %d is a replay - no DRC available\n",
+			__func__, seqid);
+		return htonl(NFS4_OK);
+	}
+
+	/* Wraparound */
+	if (seqid == 1 && (slot->seq_nr + 1) == 0) {
+		slot->seq_nr = 1;
+		return htonl(NFS4_OK);
+	}
+
+	/* Misordered request */
+	return htonl(NFS4ERR_SEQ_MISORDERED);
+}
+
+/*
+ * Returns a pointer to a held 'struct nfs_client' that matches the server's
+ * address, major version number, and session ID.  It is the caller's
+ * responsibility to release the returned reference.
+ *
+ * Returns NULL if there are no connections with sessions, or if no session
+ * matches the one of interest.
+ */
+ static struct nfs_client *find_client_with_session(
+	const struct sockaddr *addr, u32 nfsversion,
+	struct nfs4_sessionid *sessionid)
+{
+	struct nfs_client *clp;
+
+	clp = nfs_find_client(addr, 4);
+	if (clp == NULL)
+		return NULL;
+
+	do {
+		struct nfs_client *prev = clp;
+
+		if (clp->cl_session != NULL) {
+			if (memcmp(clp->cl_session->sess_id.data,
+					sessionid->data,
+					NFS4_MAX_SESSIONID_LEN) == 0) {
+				/* Returns a held reference to clp */
+				return clp;
+			}
+		}
+		clp = nfs_find_client_next(prev);
+		nfs_put_client(prev);
+	} while (clp != NULL);
+
+	return NULL;
+}
+
+/* FIXME: referring calls should be processed */
+unsigned nfs4_callback_sequence(struct cb_sequenceargs *args,
+				struct cb_sequenceres *res)
+{
+	struct nfs_client *clp;
+	int i, status;
+
+	for (i = 0; i < args->csa_nrclists; i++)
+		kfree(args->csa_rclists[i].rcl_refcalls);
+	kfree(args->csa_rclists);
+
+	status = htonl(NFS4ERR_BADSESSION);
+	clp = find_client_with_session(args->csa_addr, 4, &args->csa_sessionid);
+	if (clp == NULL)
+		goto out;
+