fs/xfs/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
  23 typedef 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
  41 static inline void mraccess_nested(mrlock_t *mrp, int subclass)
  42 {
  43         down_read_nested(&mrp->mr_lock, subclass);
  44 }
  45
  46 static 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
  54 static inline int mrtryaccess(mrlock_t *mrp)
  55 {
  56         return down_read_trylock(&mrp->mr_lock);
  57 }
  58
  59 static 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
  69 static 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
  77 static inline void mrunlock_shared(mrlock_t *mrp)
  78 {
  79         up_read(&mrp->mr_lock);
  80 }
  81
  82 static 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__ */