/*

   * Copyright (c) 2000-2006 Silicon Graphics, Inc.

   * All Rights Reserved.

   *

   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as

   * published by the Free Software Foundation.
   *

   * This program is distributed in the hope that it would be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.

   *

   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write the Free Software Foundation,
   * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

   */
  #ifndef __XFS_SUPPORT_MRLOCK_H__
  #define __XFS_SUPPORT_MRLOCK_H__
  
  #include <linux/rwsem.h>

  typedef struct {
  	struct rw_semaphore	mr_lock;

  #if defined(DEBUG) || defined(XFS_WARN)

  	int			mr_writer;

  #endif

  } mrlock_t;

  #if defined(DEBUG) || defined(XFS_WARN)

  #define mrinit(mrp, name)	\

  	do { (mrp)->mr_writer = 0; init_rwsem(&(mrp)->mr_lock); } while (0)

  #else
  #define mrinit(mrp, name)	\
  	do { init_rwsem(&(mrp)->mr_lock); } while (0)
  #endif

  #define mrlock_init(mrp, t,n,s)	mrinit(mrp, n)
  #define mrfree(mrp)		do { } while (0)

  static inline void mraccess_nested(mrlock_t *mrp, int subclass)
  {
  	down_read_nested(&mrp->mr_lock, subclass);
  }
  
  static inline void mrupdate_nested(mrlock_t *mrp, int subclass)
  {
  	down_write_nested(&mrp->mr_lock, subclass);

  #if defined(DEBUG) || defined(XFS_WARN)

  	mrp->mr_writer = 1;

  #endif

  }

  static inline int mrtryaccess(mrlock_t *mrp)
  {
  	return down_read_trylock(&mrp->mr_lock);
  }
  
  static inline int mrtryupdate(mrlock_t *mrp)
  {
  	if (!down_write_trylock(&mrp->mr_lock))
  		return 0;

  #if defined(DEBUG) || defined(XFS_WARN)

  	mrp->mr_writer = 1;

  #endif

  	return 1;
  }

  static inline void mrunlock_excl(mrlock_t *mrp)

  {

  #if defined(DEBUG) || defined(XFS_WARN)

  	mrp->mr_writer = 0;
  #endif
  	up_write(&mrp->mr_lock);

  }

  static inline void mrunlock_shared(mrlock_t *mrp)

  {

  	up_read(&mrp->mr_lock);

  }

  static inline void mrdemote(mrlock_t *mrp)

  {

  #if defined(DEBUG) || defined(XFS_WARN)

  	mrp->mr_writer = 0;

  #endif

  	downgrade_write(&mrp->mr_lock);
  }

  
  #endif /* __XFS_SUPPORT_MRLOCK_H__ */