/*
   * linux/fs/lockd/clntlock.c
   *
   * Lock handling for the client side NLM implementation
   *
   * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
   */
  
  #include <linux/module.h>
  #include <linux/types.h>

  #include <linux/slab.h>

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

  #include <linux/kthread.h>

  
  #define NLMDBG_FACILITY		NLMDBG_CLIENT
  
  /*
   * Local function prototypes
   */
  static int			reclaimer(void *ptr);
  
  /*
   * The following functions handle blocking and granting from the
   * client perspective.
   */
  
  /*
   * This is the representation of a blocked client lock.
   */
  struct nlm_wait {

  	struct list_head	b_list;		/* linked list */

  	wait_queue_head_t	b_wait;		/* where to wait on */
  	struct nlm_host *	b_host;
  	struct file_lock *	b_lock;		/* local file lock */
  	unsigned short		b_reclaim;	/* got to reclaim lock */

  	__be32			b_status;	/* grant callback status */

  };

  static LIST_HEAD(nlm_blocked);

  static DEFINE_SPINLOCK(nlm_blocked_lock);

  /**
   * nlmclnt_init - Set up per-NFS mount point lockd data structures

   * @nlm_init: pointer to arguments structure

   *
   * Returns pointer to an appropriate nlm_host struct,
   * or an ERR_PTR value.
   */

  struct nlm_host *nlmclnt_init(const struct nlmclnt_initdata *nlm_init)

  {
  	struct nlm_host *host;

  	u32 nlm_version = (nlm_init->nfs_version == 2) ? 1 : 4;

  	int status;

  	status = lockd_up();

  	if (status < 0)
  		return ERR_PTR(status);

  	host = nlmclnt_lookup_host(nlm_init->address, nlm_init->addrlen,

  				   nlm_init->protocol, nlm_version,

  				   nlm_init->hostname, nlm_init->noresvport);

  	if (host == NULL) {
  		lockd_down();
  		return ERR_PTR(-ENOLCK);
  	}
  
  	return host;
  }
  EXPORT_SYMBOL_GPL(nlmclnt_init);
  
  /**
   * nlmclnt_done - Release resources allocated by nlmclnt_init()
   * @host: nlm_host structure reserved by nlmclnt_init()
   *
   */
  void nlmclnt_done(struct nlm_host *host)
  {

  	nlmclnt_release_host(host);

  	lockd_down();
  }
  EXPORT_SYMBOL_GPL(nlmclnt_done);

  /*

   * Queue up a lock for blocking so that the GRANTED request can see it

   */

  struct nlm_wait *nlmclnt_prepare_block(struct nlm_host *host, struct file_lock *fl)

  {
  	struct nlm_wait *block;

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

  	if (block != NULL) {
  		block->b_host = host;
  		block->b_lock = fl;
  		init_waitqueue_head(&block->b_wait);

  		block->b_status = nlm_lck_blocked;

  
  		spin_lock(&nlm_blocked_lock);

  		list_add(&block->b_list, &nlm_blocked);

  		spin_unlock(&nlm_blocked_lock);

  	}
  	return block;

  }

  void nlmclnt_finish_block(struct nlm_wait *block)

  {

  	if (block == NULL)
  		return;

  	spin_lock(&nlm_blocked_lock);

  	list_del(&block->b_list);

  	spin_unlock(&nlm_blocked_lock);

  	kfree(block);
  }

  /*
   * Block on a lock
   */

  int nlmclnt_block(struct nlm_wait *block, struct nlm_rqst *req, long timeout)

  {

  	long ret;

  	/* A borken server might ask us to block even if we didn't
  	 * request it. Just say no!
  	 */

  	if (block == NULL)

  		return -EAGAIN;

  
  	/* Go to sleep waiting for GRANT callback. Some servers seem
  	 * to lose callbacks, however, so we're going to poll from
  	 * time to time just to make sure.
  	 *
  	 * For now, the retry frequency is pretty high; normally 
  	 * a 1 minute timeout would do. See the comment before
  	 * nlmclnt_lock for an explanation.
  	 */

  	ret = wait_event_interruptible_timeout(block->b_wait,

  			block->b_status != nlm_lck_blocked,

  			timeout);

  	if (ret < 0)
  		return -ERESTARTSYS;
  	req->a_res.status = block->b_status;
  	return 0;

  }
  
  /*
   * The server lockd has called us back to tell us the lock was granted
   */

  __be32 nlmclnt_grant(const struct sockaddr *addr, const struct nlm_lock *lock)

  {

  	const struct file_lock *fl = &lock->fl;
  	const struct nfs_fh *fh = &lock->fh;

  	struct nlm_wait	*block;

  	__be32 res = nlm_lck_denied;

  
  	/*
  	 * Look up blocked request based on arguments. 
  	 * Warning: must not use cookie to match it!
  	 */

  	spin_lock(&nlm_blocked_lock);

  	list_for_each_entry(block, &nlm_blocked, b_list) {

  		struct file_lock *fl_blocked = block->b_lock;

  		if (fl_blocked->fl_start != fl->fl_start)
  			continue;
  		if (fl_blocked->fl_end != fl->fl_end)
  			continue;
  		/*
  		 * Careful! The NLM server will return the 32-bit "pid" that
  		 * we put on the wire: in this case the lockowner "pid".
  		 */
  		if (fl_blocked->fl_u.nfs_fl.owner->pid != lock->svid)

  			continue;

  		if (!rpc_cmp_addr(nlm_addr(block->b_host), addr))

  			continue;

  		if (nfs_compare_fh(NFS_FH(fl_blocked->fl_file->f_path.dentry->d_inode) ,fh) != 0)

  			continue;
  		/* Alright, we found a lock. Set the return status
  		 * and wake up the caller
  		 */

  		block->b_status = nlm_granted;

  		wake_up(&block->b_wait);
  		res = nlm_granted;

  	}

  	spin_unlock(&nlm_blocked_lock);

  	return res;

  }
  
  /*
   * The following procedures deal with the recovery of locks after a
   * server crash.
   */
  
  /*

   * Reclaim all locks on server host. We do this by spawning a separate
   * reclaimer thread.
   */
  void

  nlmclnt_recovery(struct nlm_host *host)

  {

  	struct task_struct *task;

  	if (!host->h_reclaiming++) {

  		nlm_get_host(host);

  		task = kthread_run(reclaimer, host, "%s-reclaim", host->h_name);
  		if (IS_ERR(task))
  			printk(KERN_ERR "lockd: unable to spawn reclaimer "
  				"thread. Locks for %s won't be reclaimed! "
  				"(%ld)
  ", host->h_name, PTR_ERR(task));

  	}
  }
  
  static int
  reclaimer(void *ptr)
  {
  	struct nlm_host	  *host = (struct nlm_host *) ptr;
  	struct nlm_wait	  *block;

  	struct file_lock *fl, *next;

  	u32 nsmstate;

  	allow_signal(SIGKILL);

  	down_write(&host->h_rwsem);

  	lockd_up();	/* note: this cannot fail as lockd is already running */

  	dprintk("lockd: reclaiming locks for host %s
  ", host->h_name);

  restart:

  	nsmstate = host->h_nsmstate;

  
  	/* Force a portmap getport - the peer's lockd will
  	 * most likely end up on a different port.
  	 */

  	host->h_nextrebind = jiffies;

  	nlm_rebind_host(host);
  
  	/* First, reclaim all locks that have been granted. */
  	list_splice_init(&host->h_granted, &host->h_reclaim);

  	list_for_each_entry_safe(fl, next, &host->h_reclaim, fl_u.nfs_fl.list) {

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

  		/*
  		 * sending this thread a SIGKILL will result in any unreclaimed
  		 * locks being removed from the h_granted list. This means that
  		 * the kernel will not attempt to reclaim them again if a new
  		 * reclaimer thread is spawned for this host.
  		 */

  		if (signalled())

  			continue;

  		if (nlmclnt_reclaim(host, fl) != 0)
  			continue;
  		list_add_tail(&fl->fl_u.nfs_fl.list, &host->h_granted);
  		if (host->h_nsmstate != nsmstate) {
  			/* Argh! The server rebooted again! */

  			goto restart;
  		}

  	}

  
  	host->h_reclaiming = 0;
  	up_write(&host->h_rwsem);

  	dprintk("NLM: done reclaiming locks for host %s
  ", host->h_name);

  
  	/* Now, wake up all processes that sleep on a blocked lock */

  	spin_lock(&nlm_blocked_lock);

  	list_for_each_entry(block, &nlm_blocked, b_list) {

  		if (block->b_host == host) {

  			block->b_status = nlm_lck_denied_grace_period;

  			wake_up(&block->b_wait);
  		}
  	}

  	spin_unlock(&nlm_blocked_lock);

  
  	/* Release host handle after use */

  	nlmclnt_release_host(host);

  	lockd_down();

  	return 0;

  }