/*
   * linux/fs/lockd/clntproc.c
   *
   * RPC procedures for the client side NLM implementation
   *
   * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
   */

  #include <linux/module.h>

  #include <linux/slab.h>

  #include <linux/types.h>
  #include <linux/errno.h>
  #include <linux/fs.h>
  #include <linux/nfs_fs.h>
  #include <linux/utsname.h>

  #include <linux/freezer.h>

  #include <linux/sunrpc/clnt.h>
  #include <linux/sunrpc/svc.h>
  #include <linux/lockd/lockd.h>

  
  #define NLMDBG_FACILITY		NLMDBG_CLIENT
  #define NLMCLNT_GRACE_WAIT	(5*HZ)

  #define NLMCLNT_POLL_TIMEOUT	(30*HZ)

  #define NLMCLNT_MAX_RETRIES	3

  
  static int	nlmclnt_test(struct nlm_rqst *, struct file_lock *);
  static int	nlmclnt_lock(struct nlm_rqst *, struct file_lock *);
  static int	nlmclnt_unlock(struct nlm_rqst *, struct file_lock *);

  static int	nlm_stat_to_errno(__be32 stat);

  static void	nlmclnt_locks_init_private(struct file_lock *fl, struct nlm_host *host);

  static int	nlmclnt_cancel(struct nlm_host *, int , struct file_lock *);

  static const struct rpc_call_ops nlmclnt_unlock_ops;
  static const struct rpc_call_ops nlmclnt_cancel_ops;

  /*
   * Cookie counter for NLM requests
   */

  static atomic_t	nlm_cookie = ATOMIC_INIT(0x1234);

  void nlmclnt_next_cookie(struct nlm_cookie *c)

  {

  	u32	cookie = atomic_inc_return(&nlm_cookie);
  
  	memcpy(c->data, &cookie, 4);

  	c->len=4;

  }
  
  static struct nlm_lockowner *nlm_get_lockowner(struct nlm_lockowner *lockowner)
  {
  	atomic_inc(&lockowner->count);
  	return lockowner;
  }
  
  static void nlm_put_lockowner(struct nlm_lockowner *lockowner)
  {
  	if (!atomic_dec_and_lock(&lockowner->count, &lockowner->host->h_lock))
  		return;
  	list_del(&lockowner->list);
  	spin_unlock(&lockowner->host->h_lock);

  	nlmclnt_release_host(lockowner->host);

  	kfree(lockowner);
  }
  
  static inline int nlm_pidbusy(struct nlm_host *host, uint32_t pid)
  {
  	struct nlm_lockowner *lockowner;
  	list_for_each_entry(lockowner, &host->h_lockowners, list) {
  		if (lockowner->pid == pid)
  			return -EBUSY;
  	}
  	return 0;
  }
  
  static inline uint32_t __nlm_alloc_pid(struct nlm_host *host)
  {
  	uint32_t res;
  	do {
  		res = host->h_pidcount++;
  	} while (nlm_pidbusy(host, res) < 0);
  	return res;
  }
  
  static struct nlm_lockowner *__nlm_find_lockowner(struct nlm_host *host, fl_owner_t owner)
  {
  	struct nlm_lockowner *lockowner;
  	list_for_each_entry(lockowner, &host->h_lockowners, list) {
  		if (lockowner->owner != owner)
  			continue;
  		return nlm_get_lockowner(lockowner);
  	}
  	return NULL;
  }
  
  static struct nlm_lockowner *nlm_find_lockowner(struct nlm_host *host, fl_owner_t owner)
  {
  	struct nlm_lockowner *res, *new = NULL;
  
  	spin_lock(&host->h_lock);
  	res = __nlm_find_lockowner(host, owner);
  	if (res == NULL) {
  		spin_unlock(&host->h_lock);

  		new = kmalloc(sizeof(*new), GFP_KERNEL);

  		spin_lock(&host->h_lock);
  		res = __nlm_find_lockowner(host, owner);
  		if (res == NULL && new != NULL) {
  			res = new;
  			atomic_set(&new->count, 1);
  			new->owner = owner;
  			new->pid = __nlm_alloc_pid(host);
  			new->host = nlm_get_host(host);
  			list_add(&new->list, &host->h_lockowners);
  			new = NULL;
  		}
  	}
  	spin_unlock(&host->h_lock);

  	kfree(new);

  	return res;
  }
  
  /*
   * Initialize arguments for TEST/LOCK/UNLOCK/CANCEL calls
   */
  static void nlmclnt_setlockargs(struct nlm_rqst *req, struct file_lock *fl)
  {
  	struct nlm_args	*argp = &req->a_args;
  	struct nlm_lock	*lock = &argp->lock;
  
  	nlmclnt_next_cookie(&argp->cookie);

  	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;

  	lock->oh.len  = snprintf(req->a_owner, sizeof(req->a_owner), "%u@%s",
  				(unsigned int)fl->fl_u.nfs_fl.owner->pid,

  				utsname()->nodename);

  	lock->svid = fl->fl_u.nfs_fl.owner->pid;

  	lock->fl.fl_start = fl->fl_start;
  	lock->fl.fl_end = fl->fl_end;
  	lock->fl.fl_type = fl->fl_type;

  }
  
  static void nlmclnt_release_lockargs(struct nlm_rqst *req)
  {

  	BUG_ON(req->a_args.lock.fl.fl_ops != NULL);

  }

  /**
   * nlmclnt_proc - Perform a single client-side lock request
   * @host: address of a valid nlm_host context representing the NLM server
   * @cmd: fcntl-style file lock operation to perform
   * @fl: address of arguments for the lock operation
   *

   */

  int nlmclnt_proc(struct nlm_host *host, int cmd, struct file_lock *fl)

  {

  	struct nlm_rqst		*call;

  	int			status;

  	nlm_get_host(host);

  	call = nlm_alloc_call(host);
  	if (call == NULL)
  		return -ENOMEM;

  	nlmclnt_locks_init_private(fl, host);
  	/* Set up the argument struct */
  	nlmclnt_setlockargs(call, fl);

  	if (IS_SETLK(cmd) || IS_SETLKW(cmd)) {
  		if (fl->fl_type != F_UNLCK) {
  			call->a_args.block = IS_SETLKW(cmd) ? 1 : 0;
  			status = nlmclnt_lock(call, fl);
  		} else
  			status = nlmclnt_unlock(call, fl);
  	} else if (IS_GETLK(cmd))
  		status = nlmclnt_test(call, fl);
  	else
  		status = -EINVAL;

  	fl->fl_ops->fl_release_private(fl);
  	fl->fl_ops = NULL;

  	dprintk("lockd: clnt proc returns %d
  ", status);

  	return status;
  }

  EXPORT_SYMBOL_GPL(nlmclnt_proc);

  
  /*
   * Allocate an NLM RPC call struct

   *
   * Note: the caller must hold a reference to host. In case of failure,
   * this reference will be released.

   */

  struct nlm_rqst *nlm_alloc_call(struct nlm_host *host)

  {
  	struct nlm_rqst	*call;

  	for(;;) {
  		call = kzalloc(sizeof(*call), GFP_KERNEL);
  		if (call != NULL) {

  			atomic_set(&call->a_count, 1);

  			locks_init_lock(&call->a_args.lock.fl);
  			locks_init_lock(&call->a_res.lock.fl);

  			call->a_host = host;

  			return call;
  		}

  		if (signalled())
  			break;

  		printk("nlm_alloc_call: failed, waiting for memory
  ");

  		schedule_timeout_interruptible(5*HZ);

  	}

  	nlmclnt_release_host(host);

  	return NULL;
  }

  void nlmclnt_release_call(struct nlm_rqst *call)

  {

  	if (!atomic_dec_and_test(&call->a_count))
  		return;

  	nlmclnt_release_host(call->a_host);

  	nlmclnt_release_lockargs(call);
  	kfree(call);
  }
  
  static void nlmclnt_rpc_release(void *data)
  {

  	nlmclnt_release_call(data);

  }

  static int nlm_wait_on_grace(wait_queue_head_t *queue)
  {
  	DEFINE_WAIT(wait);
  	int status = -EINTR;
  
  	prepare_to_wait(queue, &wait, TASK_INTERRUPTIBLE);
  	if (!signalled ()) {
  		schedule_timeout(NLMCLNT_GRACE_WAIT);

  		try_to_freeze();

  		if (!signalled ())
  			status = 0;
  	}
  	finish_wait(queue, &wait);
  	return status;
  }
  
  /*
   * Generic NLM call
   */
  static int

  nlmclnt_call(struct rpc_cred *cred, struct nlm_rqst *req, u32 proc)

  {
  	struct nlm_host	*host = req->a_host;
  	struct rpc_clnt	*clnt;
  	struct nlm_args	*argp = &req->a_args;
  	struct nlm_res	*resp = &req->a_res;
  	struct rpc_message msg = {
  		.rpc_argp	= argp,
  		.rpc_resp	= resp,

  		.rpc_cred	= cred,

  	};
  	int		status;
  
  	dprintk("lockd: call procedure %d on %s
  ",
  			(int)proc, host->h_name);
  
  	do {
  		if (host->h_reclaiming && !argp->reclaim)
  			goto in_grace_period;
  
  		/* If we have no RPC client yet, create one. */
  		if ((clnt = nlm_bind_host(host)) == NULL)
  			return -ENOLCK;
  		msg.rpc_proc = &clnt->cl_procinfo[proc];
  
  		/* Perform the RPC call. If an error occurs, try again */
  		if ((status = rpc_call_sync(clnt, &msg, 0)) < 0) {
  			dprintk("lockd: rpc_call returned error %d
  ", -status);
  			switch (status) {
  			case -EPROTONOSUPPORT:
  				status = -EINVAL;
  				break;
  			case -ECONNREFUSED:
  			case -ETIMEDOUT:
  			case -ENOTCONN:
  				nlm_rebind_host(host);
  				status = -EAGAIN;
  				break;
  			case -ERESTARTSYS:
  				return signalled () ? -EINTR : status;
  			default:
  				break;
  			}
  			break;
  		} else

  		if (resp->status == nlm_lck_denied_grace_period) {

  			dprintk("lockd: server in grace period
  ");
  			if (argp->reclaim) {
  				printk(KERN_WARNING
  				     "lockd: spurious grace period reject?!
  ");
  				return -ENOLCK;
  			}
  		} else {
  			if (!argp->reclaim) {
  				/* We appear to be out of the grace period */
  				wake_up_all(&host->h_gracewait);
  			}

  			dprintk("lockd: server returns status %d
  ",
  				ntohl(resp->status));

  			return 0;	/* Okay, call complete */
  		}
  
  in_grace_period:
  		/*
  		 * The server has rebooted and appears to be in the grace
  		 * period during which locks are only allowed to be
  		 * reclaimed.
  		 * We can only back off and try again later.
  		 */
  		status = nlm_wait_on_grace(&host->h_gracewait);
  	} while (status == 0);
  
  	return status;
  }
  
  /*
   * Generic NLM call, async version.
   */

  static struct rpc_task *__nlm_async_call(struct nlm_rqst *req, u32 proc, struct rpc_message *msg, const struct rpc_call_ops *tk_ops)

  {
  	struct nlm_host	*host = req->a_host;
  	struct rpc_clnt	*clnt;

  	struct rpc_task_setup task_setup_data = {
  		.rpc_message = msg,
  		.callback_ops = tk_ops,
  		.callback_data = req,
  		.flags = RPC_TASK_ASYNC,
  	};

  
  	dprintk("lockd: call procedure %d on %s (async)
  ",
  			(int)proc, host->h_name);
  
  	/* If we have no RPC client yet, create one. */

  	clnt = nlm_bind_host(host);
  	if (clnt == NULL)
  		goto out_err;

  	msg->rpc_proc = &clnt->cl_procinfo[proc];

  	task_setup_data.rpc_client = clnt;

          /* bootstrap and kick off the async RPC call */

  	return rpc_run_task(&task_setup_data);

  out_err:

  	tk_ops->rpc_release(req);

  	return ERR_PTR(-ENOLCK);
  }
  
  static int nlm_do_async_call(struct nlm_rqst *req, u32 proc, struct rpc_message *msg, const struct rpc_call_ops *tk_ops)
  {
  	struct rpc_task *task;
  
  	task = __nlm_async_call(req, proc, msg, tk_ops);
  	if (IS_ERR(task))
  		return PTR_ERR(task);
  	rpc_put_task(task);
  	return 0;

  }

  /*
   * NLM asynchronous call.
   */

  int nlm_async_call(struct nlm_rqst *req, u32 proc, const struct rpc_call_ops *tk_ops)
  {
  	struct rpc_message msg = {
  		.rpc_argp	= &req->a_args,
  		.rpc_resp	= &req->a_res,
  	};

  	return nlm_do_async_call(req, proc, &msg, tk_ops);

  }
  
  int nlm_async_reply(struct nlm_rqst *req, u32 proc, const struct rpc_call_ops *tk_ops)
  {
  	struct rpc_message msg = {
  		.rpc_argp	= &req->a_res,
  	};

  	return nlm_do_async_call(req, proc, &msg, tk_ops);
  }
  
  /*
   * NLM client asynchronous call.
   *
   * Note that although the calls are asynchronous, and are therefore
   *      guaranteed to complete, we still always attempt to wait for
   *      completion in order to be able to correctly track the lock
   *      state.
   */

  static int nlmclnt_async_call(struct rpc_cred *cred, struct nlm_rqst *req, u32 proc, const struct rpc_call_ops *tk_ops)

  {
  	struct rpc_message msg = {
  		.rpc_argp	= &req->a_args,
  		.rpc_resp	= &req->a_res,

  		.rpc_cred	= cred,

  	};
  	struct rpc_task *task;
  	int err;
  
  	task = __nlm_async_call(req, proc, &msg, tk_ops);
  	if (IS_ERR(task))
  		return PTR_ERR(task);
  	err = rpc_wait_for_completion_task(task);
  	rpc_put_task(task);
  	return err;

  }

  /*
   * TEST for the presence of a conflicting lock
   */
  static int
  nlmclnt_test(struct nlm_rqst *req, struct file_lock *fl)
  {
  	int	status;

  	status = nlmclnt_call(nfs_file_cred(fl->fl_file), req, NLMPROC_TEST);

  	if (status < 0)

  		goto out;

  	switch (req->a_res.status) {

  		case nlm_granted:

  			fl->fl_type = F_UNLCK;
  			break;

  		case nlm_lck_denied:

  			/*
  			 * Report the conflicting lock back to the application.
  			 */
  			fl->fl_start = req->a_res.lock.fl.fl_start;

  			fl->fl_end = req->a_res.lock.fl.fl_end;

  			fl->fl_type = req->a_res.lock.fl.fl_type;
  			fl->fl_pid = 0;
  			break;
  		default:
  			status = nlm_stat_to_errno(req->a_res.status);

  	}

  out:

  	nlmclnt_release_call(req);

  	return status;

  }
  
  static void nlmclnt_locks_copy_lock(struct file_lock *new, struct file_lock *fl)
  {

  	spin_lock(&fl->fl_u.nfs_fl.owner->host->h_lock);

  	new->fl_u.nfs_fl.state = fl->fl_u.nfs_fl.state;
  	new->fl_u.nfs_fl.owner = nlm_get_lockowner(fl->fl_u.nfs_fl.owner);
  	list_add_tail(&new->fl_u.nfs_fl.list, &fl->fl_u.nfs_fl.owner->host->h_granted);

  	spin_unlock(&fl->fl_u.nfs_fl.owner->host->h_lock);

  }
  
  static void nlmclnt_locks_release_private(struct file_lock *fl)
  {

  	spin_lock(&fl->fl_u.nfs_fl.owner->host->h_lock);

  	list_del(&fl->fl_u.nfs_fl.list);

  	spin_unlock(&fl->fl_u.nfs_fl.owner->host->h_lock);

  	nlm_put_lockowner(fl->fl_u.nfs_fl.owner);

  }

  static const struct file_lock_operations nlmclnt_lock_ops = {

  	.fl_copy_lock = nlmclnt_locks_copy_lock,
  	.fl_release_private = nlmclnt_locks_release_private,
  };
  
  static void nlmclnt_locks_init_private(struct file_lock *fl, struct nlm_host *host)
  {
  	BUG_ON(fl->fl_ops != NULL);
  	fl->fl_u.nfs_fl.state = 0;

  	fl->fl_u.nfs_fl.owner = nlm_find_lockowner(host, fl->fl_owner);

  	INIT_LIST_HEAD(&fl->fl_u.nfs_fl.list);

  	fl->fl_ops = &nlmclnt_lock_ops;
  }

  static int do_vfs_lock(struct file_lock *fl)

  {
  	int res = 0;
  	switch (fl->fl_flags & (FL_POSIX|FL_FLOCK)) {
  		case FL_POSIX:
  			res = posix_lock_file_wait(fl->fl_file, fl);
  			break;
  		case FL_FLOCK:
  			res = flock_lock_file_wait(fl->fl_file, fl);
  			break;
  		default:
  			BUG();
  	}

  	return res;

  }
  
  /*
   * LOCK: Try to create a lock
   *
   *			Programmer Harassment Alert
   *
   * When given a blocking lock request in a sync RPC call, the HPUX lockd
   * will faithfully return LCK_BLOCKED but never cares to notify us when
   * the lock could be granted. This way, our local process could hang
   * around forever waiting for the callback.
   *
   *  Solution A:	Implement busy-waiting
   *  Solution B: Use the async version of the call (NLM_LOCK_{MSG,RES})
   *
   * For now I am implementing solution A, because I hate the idea of
   * re-implementing lockd for a third time in two months. The async
   * calls shouldn't be too hard to do, however.
   *
   * This is one of the lovely things about standards in the NFS area:
   * they're so soft and squishy you can't really blame HP for doing this.
   */
  static int
  nlmclnt_lock(struct nlm_rqst *req, struct file_lock *fl)
  {

  	struct rpc_cred *cred = nfs_file_cred(fl->fl_file);

  	struct nlm_host	*host = req->a_host;
  	struct nlm_res	*resp = &req->a_res;

  	struct nlm_wait *block = NULL;

  	unsigned char fl_flags = fl->fl_flags;

  	unsigned char fl_type;

  	int status = -ENOLCK;

  	if (nsm_monitor(host) < 0)

  		goto out;

  	req->a_args.state = nsm_local_state;

  	fl->fl_flags |= FL_ACCESS;
  	status = do_vfs_lock(fl);

  	fl->fl_flags = fl_flags;

  	if (status < 0)
  		goto out;

  	block = nlmclnt_prepare_block(host, fl);

  again:

  	/*
  	 * Initialise resp->status to a valid non-zero value,
  	 * since 0 == nlm_lck_granted
  	 */
  	resp->status = nlm_lck_blocked;

  	for(;;) {

  		/* Reboot protection */
  		fl->fl_u.nfs_fl.state = host->h_state;

  		status = nlmclnt_call(cred, req, NLMPROC_LOCK);

  		if (status < 0)

  			break;

  		/* Did a reclaimer thread notify us of a server reboot? */

  		if (resp->status ==  nlm_lck_denied_grace_period)

  			continue;

  		if (resp->status != nlm_lck_blocked)

  			break;

  		/* Wait on an NLM blocking lock */
  		status = nlmclnt_block(block, req, NLMCLNT_POLL_TIMEOUT);

  		if (status < 0)

  			break;

  		if (resp->status != nlm_lck_blocked)

  			break;

  	}

  	/* if we were interrupted while blocking, then cancel the lock request
  	 * and exit
  	 */
  	if (resp->status == nlm_lck_blocked) {
  		if (!req->a_args.block)
  			goto out_unlock;
  		if (nlmclnt_cancel(host, req->a_args.block, fl) == 0)
  			goto out_unblock;
  	}

  	if (resp->status == nlm_granted) {

  		down_read(&host->h_rwsem);
  		/* Check whether or not the server has rebooted */
  		if (fl->fl_u.nfs_fl.state != host->h_state) {
  			up_read(&host->h_rwsem);
  			goto again;
  		}

  		/* Ensure the resulting lock will get added to granted list */

  		fl->fl_flags |= FL_SLEEP;

  		if (do_vfs_lock(fl) < 0)

  			printk(KERN_WARNING "%s: VFS is out of sync with lock manager!
  ", __func__);

  		up_read(&host->h_rwsem);

  		fl->fl_flags = fl_flags;

  		status = 0;

  	}

  	if (status < 0)
  		goto out_unlock;

  	/*
  	 * EAGAIN doesn't make sense for sleeping locks, and in some
  	 * cases NLM_LCK_DENIED is returned for a permanent error.  So
  	 * turn it into an ENOLCK.
  	 */
  	if (resp->status == nlm_lck_denied && (fl_flags & FL_SLEEP))
  		status = -ENOLCK;
  	else
  		status = nlm_stat_to_errno(resp->status);

  out_unblock:

  	nlmclnt_finish_block(block);

  out:

  	nlmclnt_release_call(req);

  	return status;

  out_unlock:
  	/* Fatal error: ensure that we remove the lock altogether */
  	dprintk("lockd: lock attempt ended in fatal error.
  "
  		"       Attempting to unlock.
  ");
  	nlmclnt_finish_block(block);
  	fl_type = fl->fl_type;
  	fl->fl_type = F_UNLCK;
  	down_read(&host->h_rwsem);
  	do_vfs_lock(fl);
  	up_read(&host->h_rwsem);
  	fl->fl_type = fl_type;
  	fl->fl_flags = fl_flags;

  	nlmclnt_async_call(cred, req, NLMPROC_UNLOCK, &nlmclnt_unlock_ops);

  	return status;

  }
  
  /*
   * RECLAIM: Try to reclaim a lock
   */
  int
  nlmclnt_reclaim(struct nlm_host *host, struct file_lock *fl)
  {
  	struct nlm_rqst reqst, *req;
  	int		status;
  
  	req = &reqst;
  	memset(req, 0, sizeof(*req));
  	locks_init_lock(&req->a_args.lock.fl);
  	locks_init_lock(&req->a_res.lock.fl);
  	req->a_host  = host;
  	req->a_flags = 0;
  
  	/* Set up the argument struct */
  	nlmclnt_setlockargs(req, fl);
  	req->a_args.reclaim = 1;

  	status = nlmclnt_call(nfs_file_cred(fl->fl_file), req, NLMPROC_LOCK);
  	if (status >= 0 && req->a_res.status == nlm_granted)

  		return 0;
  
  	printk(KERN_WARNING "lockd: failed to reclaim lock for pid %d "
  				"(errno %d, status %d)
  ", fl->fl_pid,

  				status, ntohl(req->a_res.status));

  
  	/*
  	 * FIXME: This is a serious failure. We can
  	 *
  	 *  a.	Ignore the problem
  	 *  b.	Send the owning process some signal (Linux doesn't have
  	 *	SIGLOST, though...)
  	 *  c.	Retry the operation
  	 *
  	 * Until someone comes up with a simple implementation
  	 * for b or c, I'll choose option a.
  	 */
  
  	return -ENOLCK;
  }
  
  /*
   * UNLOCK: remove an existing lock
   */
  static int
  nlmclnt_unlock(struct nlm_rqst *req, struct file_lock *fl)
  {

  	struct nlm_host	*host = req->a_host;

  	struct nlm_res	*resp = &req->a_res;

  	int status;
  	unsigned char fl_flags = fl->fl_flags;

  	/*

  	 * Note: the server is supposed to either grant us the unlock
  	 * request, or to deny it with NLM_LCK_DENIED_GRACE_PERIOD. In either
  	 * case, we want to unlock.
  	 */

  	fl->fl_flags |= FL_EXISTS;

  	down_read(&host->h_rwsem);

  	status = do_vfs_lock(fl);
  	up_read(&host->h_rwsem);
  	fl->fl_flags = fl_flags;
  	if (status == -ENOENT) {
  		status = 0;

  		goto out;
  	}

  	atomic_inc(&req->a_count);

  	status = nlmclnt_async_call(nfs_file_cred(fl->fl_file), req,
  			NLMPROC_UNLOCK, &nlmclnt_unlock_ops);

  	if (status < 0)

  		goto out;

  	if (resp->status == nlm_granted)

  		goto out;

  	if (resp->status != nlm_lck_denied_nolocks)

  		printk("lockd: unexpected unlock status: %d
  ",
  			ntohl(resp->status));

  	/* What to do now? I'm out of my depth... */

  	status = -ENOLCK;
  out:

  	nlmclnt_release_call(req);

  	return status;

  }

  static void nlmclnt_unlock_callback(struct rpc_task *task, void *data)

  {

  	struct nlm_rqst	*req = data;

  	u32 status = ntohl(req->a_res.status);

  
  	if (RPC_ASSASSINATED(task))
  		goto die;
  
  	if (task->tk_status < 0) {
  		dprintk("lockd: unlock failed (err = %d)
  ", -task->tk_status);

  		switch (task->tk_status) {
  		case -EACCES:
  		case -EIO:
  			goto die;
  		default:
  			goto retry_rebind;
  		}

  	}
  	if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
  		rpc_delay(task, NLMCLNT_GRACE_WAIT);
  		goto retry_unlock;
  	}
  	if (status != NLM_LCK_GRANTED)
  		printk(KERN_WARNING "lockd: unexpected unlock status: %d
  ", status);
  die:

  	return;
   retry_rebind:
  	nlm_rebind_host(req->a_host);
   retry_unlock:
  	rpc_restart_call(task);
  }

  static const struct rpc_call_ops nlmclnt_unlock_ops = {
  	.rpc_call_done = nlmclnt_unlock_callback,

  	.rpc_release = nlmclnt_rpc_release,

  };

  /*
   * Cancel a blocked lock request.
   * We always use an async RPC call for this in order not to hang a
   * process that has been Ctrl-C'ed.
   */

  static int nlmclnt_cancel(struct nlm_host *host, int block, struct file_lock *fl)

  {
  	struct nlm_rqst	*req;

  	int status;
  
  	dprintk("lockd: blocking lock attempt was interrupted by a signal.
  "
  		"       Attempting to cancel lock.
  ");

  	req = nlm_alloc_call(nlm_get_host(host));

  	if (!req)
  		return -ENOMEM;

  	req->a_flags = RPC_TASK_ASYNC;
  
  	nlmclnt_setlockargs(req, fl);

  	req->a_args.block = block;

  	atomic_inc(&req->a_count);

  	status = nlmclnt_async_call(nfs_file_cred(fl->fl_file), req,
  			NLMPROC_CANCEL, &nlmclnt_cancel_ops);

  	if (status == 0 && req->a_res.status == nlm_lck_denied)
  		status = -ENOLCK;

  	nlmclnt_release_call(req);

  	return status;

  }

  static void nlmclnt_cancel_callback(struct rpc_task *task, void *data)

  {

  	struct nlm_rqst	*req = data;

  	u32 status = ntohl(req->a_res.status);

  
  	if (RPC_ASSASSINATED(task))
  		goto die;
  
  	if (task->tk_status < 0) {
  		dprintk("lockd: CANCEL call error %d, retrying.
  ",
  					task->tk_status);
  		goto retry_cancel;
  	}

  	dprintk("lockd: cancel status %u (task %u)
  ",

  			status, task->tk_pid);

  	switch (status) {

  	case NLM_LCK_GRANTED:
  	case NLM_LCK_DENIED_GRACE_PERIOD:

  	case NLM_LCK_DENIED:

  		/* Everything's good */
  		break;
  	case NLM_LCK_DENIED_NOLOCKS:
  		dprintk("lockd: CANCEL failed (server has no locks)
  ");
  		goto retry_cancel;
  	default:
  		printk(KERN_NOTICE "lockd: weird return %d for CANCEL call
  ",

  			status);

  	}
  
  die:

  	return;
  
  retry_cancel:

  	/* Don't ever retry more than 3 times */
  	if (req->a_retries++ >= NLMCLNT_MAX_RETRIES)
  		goto die;

  	nlm_rebind_host(req->a_host);
  	rpc_restart_call(task);
  	rpc_delay(task, 30 * HZ);
  }

  static const struct rpc_call_ops nlmclnt_cancel_ops = {
  	.rpc_call_done = nlmclnt_cancel_callback,

  	.rpc_release = nlmclnt_rpc_release,

  };

  /*
   * Convert an NLM status code to a generic kernel errno
   */
  static int

  nlm_stat_to_errno(__be32 status)

  {

  	switch(ntohl(status)) {

  	case NLM_LCK_GRANTED:
  		return 0;
  	case NLM_LCK_DENIED:
  		return -EAGAIN;
  	case NLM_LCK_DENIED_NOLOCKS:
  	case NLM_LCK_DENIED_GRACE_PERIOD:
  		return -ENOLCK;
  	case NLM_LCK_BLOCKED:
  		printk(KERN_NOTICE "lockd: unexpected status NLM_BLOCKED
  ");
  		return -ENOLCK;
  #ifdef CONFIG_LOCKD_V4
  	case NLM_DEADLCK:
  		return -EDEADLK;
  	case NLM_ROFS:
  		return -EROFS;
  	case NLM_STALE_FH:
  		return -ESTALE;
  	case NLM_FBIG:
  		return -EOVERFLOW;
  	case NLM_FAILED:
  		return -ENOLCK;
  #endif
  	}

  	printk(KERN_NOTICE "lockd: unexpected server status %d
  ",
  		 ntohl(status));

  	return -ENOLCK;
  }