fs/xfs/linux-2.6/mrlock.h

   1 /*
   2  * Copyright (c) 2000-2004 Silicon Graphics, Inc.  All Rights Reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of version 2 of the GNU General Public License as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it would be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  11  *
  12  * Further, this software is distributed without any warranty that it is
  13  * free of the rightful claim of any third person regarding infringement
  14  * or the like.  Any license provided herein, whether implied or
  15  * otherwise, applies only to this software file.  Patent licenses, if
  16  * any, provided herein do not apply to combinations of this program with
  17  * other software, or any other product whatsoever.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write the Free Software Foundation, Inc., 59
  21  * Temple Place - Suite 330, Boston MA 02111-1307, USA.
  22  *
  23  * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
  24  * Mountain View, CA  94043, or:
  25  *
  26  * http://www.sgi.com
  27  *
  28  * For further information regarding this notice, see:
  29  *
  30  * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
  31  */
  32 #ifndef __XFS_SUPPORT_MRLOCK_H__
  33 #define __XFS_SUPPORT_MRLOCK_H__
  34
  35 #include <linux/rwsem.h>
  36
  37 enum { MR_NONE, MR_ACCESS, MR_UPDATE };
  38
  39 typedef struct {
  40         struct rw_semaphore     mr_lock;
  41         int                     mr_writer;
  42 } mrlock_t;
  43
  44 #define mrinit(mrp, name)       \
  45         ( (mrp)->mr_writer = 0, init_rwsem(&(mrp)->mr_lock) )
  46 #define mrlock_init(mrp, t,n,s) mrinit(mrp, n)
  47 #define mrfree(mrp)             do { } while (0)
  48 #define mraccess(mrp)           mraccessf(mrp, 0)
  49 #define mrupdate(mrp)           mrupdatef(mrp, 0)
  50
  51 static inline void mraccessf(mrlock_t *mrp, int flags)
  52 {
  53         down_read(&mrp->mr_lock);
  54 }
  55
  56 static inline void mrupdatef(mrlock_t *mrp, int flags)
  57 {
  58         down_write(&mrp->mr_lock);
  59         mrp->mr_writer = 1;
  60 }
  61
  62 static inline int mrtryaccess(mrlock_t *mrp)
  63 {
  64         return down_read_trylock(&mrp->mr_lock);
  65 }
  66
  67 static inline int mrtryupdate(mrlock_t *mrp)
  68 {
  69         if (!down_write_trylock(&mrp->mr_lock))
  70                 return 0;
  71         mrp->mr_writer = 1;
  72         return 1;
  73 }
  74
  75 static inline void mrunlock(mrlock_t *mrp)
  76 {
  77         if (mrp->mr_writer) {
  78                 mrp->mr_writer = 0;
  79                 up_write(&mrp->mr_lock);
  80         } else {
  81                 up_read(&mrp->mr_lock);
  82         }
  83 }
  84
  85 static inline void mrdemote(mrlock_t *mrp)
  86 {
  87         mrp->mr_writer = 0;
  88         downgrade_write(&mrp->mr_lock);
  89 }
  90
  91 #ifdef DEBUG
  92 /*
  93  * Debug-only routine, without some platform-specific asm code, we can
  94  * now only answer requests regarding whether we hold the lock for write
  95  * (reader state is outside our visibility, we only track writer state).
  96  * Note: means !ismrlocked would give false positivies, so don't do that.
  97  */
  98 static inline int ismrlocked(mrlock_t *mrp, int type)
  99 {
 100         if (mrp && type == MR_UPDATE)
 101                 return mrp->mr_writer;
 102         return 1;
 103 }
 104 #endif
 105
 106 #endif /* __XFS_SUPPORT_MRLOCK_H__ */