linux/fs/xfs/mrlock.h
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   1/*
   2 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
   3 * All Rights Reserved.
   4 *
   5 * This program is free software; you can redistribute it and/or
   6 * modify it under the terms of the GNU General Public License as
   7 * published by the Free Software Foundation.
   8 *
   9 * This program is distributed in the hope that it would be useful,
  10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 * GNU General Public License for more details.
  13 *
  14 * You should have received a copy of the GNU General Public License
  15 * along with this program; if not, write the Free Software Foundation,
  16 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17 */
  18#ifndef __XFS_SUPPORT_MRLOCK_H__
  19#define __XFS_SUPPORT_MRLOCK_H__
  20
  21#include <linux/rwsem.h>
  22
  23typedef struct {
  24        struct rw_semaphore     mr_lock;
  25#ifdef DEBUG
  26        int                     mr_writer;
  27#endif
  28} mrlock_t;
  29
  30#ifdef DEBUG
  31#define mrinit(mrp, name)       \
  32        do { (mrp)->mr_writer = 0; init_rwsem(&(mrp)->mr_lock); } while (0)
  33#else
  34#define mrinit(mrp, name)       \
  35        do { init_rwsem(&(mrp)->mr_lock); } while (0)
  36#endif
  37
  38#define mrlock_init(mrp, t,n,s) mrinit(mrp, n)
  39#define mrfree(mrp)             do { } while (0)
  40
  41static inline void mraccess_nested(mrlock_t *mrp, int subclass)
  42{
  43        down_read_nested(&mrp->mr_lock, subclass);
  44}
  45
  46static inline void mrupdate_nested(mrlock_t *mrp, int subclass)
  47{
  48        down_write_nested(&mrp->mr_lock, subclass);
  49#ifdef DEBUG
  50        mrp->mr_writer = 1;
  51#endif
  52}
  53
  54static inline int mrtryaccess(mrlock_t *mrp)
  55{
  56        return down_read_trylock(&mrp->mr_lock);
  57}
  58
  59static inline int mrtryupdate(mrlock_t *mrp)
  60{
  61        if (!down_write_trylock(&mrp->mr_lock))
  62                return 0;
  63#ifdef DEBUG
  64        mrp->mr_writer = 1;
  65#endif
  66        return 1;
  67}
  68
  69static inline void mrunlock_excl(mrlock_t *mrp)
  70{
  71#ifdef DEBUG
  72        mrp->mr_writer = 0;
  73#endif
  74        up_write(&mrp->mr_lock);
  75}
  76
  77static inline void mrunlock_shared(mrlock_t *mrp)
  78{
  79        up_read(&mrp->mr_lock);
  80}
  81
  82static inline void mrdemote(mrlock_t *mrp)
  83{
  84#ifdef DEBUG
  85        mrp->mr_writer = 0;
  86#endif
  87        downgrade_write(&mrp->mr_lock);
  88}
  89
  90#endif /* __XFS_SUPPORT_MRLOCK_H__ */
  91
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