LXR linux/fs/xfs/linux-2.6/mrlock.h

   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
  23enum { MR_NONE, MR_ACCESS, MR_UPDATE };
  24
  25typedef struct {
  26        struct rw_semaphore     mr_lock;
  27        int                     mr_writer;
  28} mrlock_t;
  29
  30#define mrinit(mrp, name)       \
  31        do { (mrp)->mr_writer = 0; init_rwsem(&(mrp)->mr_lock); } while (0)
  32#define mrlock_init(mrp, t,n,s) mrinit(mrp, n)
  33#define mrfree(mrp)             do { } while (0)
  34
  35static inline void mraccess(mrlock_t *mrp)
  36{
  37        down_read(&mrp->mr_lock);
  38}
  39
  40static inline void mrupdate(mrlock_t *mrp)
  41{
  42        down_write(&mrp->mr_lock);
  43        mrp->mr_writer = 1;
  44}
  45
  46static inline void mraccess_nested(mrlock_t *mrp, int subclass)
  47{
  48        down_read_nested(&mrp->mr_lock, subclass);
  49}
  50
  51static inline void mrupdate_nested(mrlock_t *mrp, int subclass)
  52{
  53        down_write_nested(&mrp->mr_lock, subclass);
  54        mrp->mr_writer = 1;
  55}
  56
  57
  58static inline int mrtryaccess(mrlock_t *mrp)
  59{
  60        return down_read_trylock(&mrp->mr_lock);
  61}
  62
  63static inline int mrtryupdate(mrlock_t *mrp)
  64{
  65        if (!down_write_trylock(&mrp->mr_lock))
  66                return 0;
  67        mrp->mr_writer = 1;
  68        return 1;
  69}
  70
  71static inline void mrunlock(mrlock_t *mrp)
  72{
  73        if (mrp->mr_writer) {
  74                mrp->mr_writer = 0;
  75                up_write(&mrp->mr_lock);
  76        } else {
  77                up_read(&mrp->mr_lock);
  78        }
  79}
  80
  81static inline void mrdemote(mrlock_t *mrp)
  82{
  83        mrp->mr_writer = 0;
  84        downgrade_write(&mrp->mr_lock);
  85}
  86
  87#ifdef DEBUG
  88/*
  89 * Debug-only routine, without some platform-specific asm code, we can
  90 * now only answer requests regarding whether we hold the lock for write
  91 * (reader state is outside our visibility, we only track writer state).
  92 * Note: means !ismrlocked would give false positives, so don't do that.
  93 */
  94static inline int ismrlocked(mrlock_t *mrp, int type)
  95{
  96        if (mrp && type == MR_UPDATE)
  97                return mrp->mr_writer;
  98        return 1;
  99}
 100#endif
 101
 102#endif /* __XFS_SUPPORT_MRLOCK_H__ */
 103