fs/xfs/xfs_behavior.h

   1 /*
   2  * Copyright (c) 2000-2003 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_BEHAVIOR_H__
  33 #define __XFS_BEHAVIOR_H__
  34
  35 /*
  36  * Header file used to associate behaviors with virtualized objects.
  37  *
  38  * A virtualized object is an internal, virtualized representation of
  39  * OS entities such as persistent files, processes, or sockets.  Examples
  40  * of virtualized objects include vnodes, vprocs, and vsockets.  Often
  41  * a virtualized object is referred to simply as an "object."
  42  *
  43  * A behavior is essentially an implementation layer associated with
  44  * an object.  Multiple behaviors for an object are chained together,
  45  * the order of chaining determining the order of invocation.  Each
  46  * behavior of a given object implements the same set of interfaces
  47  * (e.g., the VOP interfaces).
  48  *
  49  * Behaviors may be dynamically inserted into an object's behavior chain,
  50  * such that the addition is transparent to consumers that already have
  51  * references to the object.  Typically, a given behavior will be inserted
  52  * at a particular location in the behavior chain.  Insertion of new
  53  * behaviors is synchronized with operations-in-progress (oip's) so that
  54  * the oip's always see a consistent view of the chain.
  55  *
  56  * The term "interpostion" is used to refer to the act of inserting
  57  * a behavior such that it interposes on (i.e., is inserted in front
  58  * of) a particular other behavior.  A key example of this is when a
  59  * system implementing distributed single system image wishes to
  60  * interpose a distribution layer (providing distributed coherency)
  61  * in front of an object that is otherwise only accessed locally.
  62  *
  63  * Note that the traditional vnode/inode combination is simply a virtualized
  64  * object that has exactly one associated behavior.
  65  *
  66  * Behavior synchronization is logic which is necessary under certain
  67  * circumstances that there is no conflict between ongoing operations
  68  * traversing the behavior chain and those dunamically modifying the
  69  * behavior chain.  Because behavior synchronization adds extra overhead
  70  * to virtual operation invocation, we want to restrict, as much as
  71  * we can, the requirement for this extra code, to those situations
  72  * in which it is truly necessary.
  73  *
  74  * Behavior synchronization is needed whenever there's at least one class
  75  * of object in the system for which:
  76  * 1) multiple behaviors for a given object are supported,
  77  * -- AND --
  78  * 2a) insertion of a new behavior can happen dynamically at any time during
  79  *     the life of an active object,
  80  *      -- AND --
  81  *      3a) insertion of a new behavior needs to synchronize with existing
  82  *          ops-in-progress.
  83  *      -- OR --
  84  *      3b) multiple different behaviors can be dynamically inserted at
  85  *          any time during the life of an active object
  86  *      -- OR --
  87  *      3c) removal of a behavior can occur at any time during the life of
  88  *          an active object.
  89  * -- OR --
  90  * 2b) removal of a behavior can occur at any time during the life of an
  91  *     active object
  92  *
  93  */
  94
  95 struct bhv_head_lock;
  96
  97 /*
  98  * Behavior head.  Head of the chain of behaviors.
  99  * Contained within each virtualized object data structure.
 100  */
 101 typedef struct bhv_head {
 102         struct bhv_desc *bh_first;      /* first behavior in chain */
 103         struct bhv_head_lock *bh_lockp; /* pointer to lock info struct */
 104 } bhv_head_t;
 105
 106 /*
 107  * Behavior descriptor.  Descriptor associated with each behavior.
 108  * Contained within the behavior's private data structure.
 109  */
 110 typedef struct bhv_desc {
 111         void            *bd_pdata;      /* private data for this behavior */
 112         void            *bd_vobj;       /* virtual object associated with */
 113         void            *bd_ops;        /* ops for this behavior */
 114         struct bhv_desc *bd_next;       /* next behavior in chain */
 115 } bhv_desc_t;
 116
 117 /*
 118  * Behavior identity field.  A behavior's identity determines the position
 119  * where it lives within a behavior chain, and it's always the first field
 120  * of the behavior's ops vector. The optional id field further identifies the
 121  * subsystem responsible for the behavior.
 122  */
 123 typedef struct bhv_identity {
 124         __u16   bi_id;          /* owning subsystem id */
 125         __u16   bi_position;    /* position in chain */
 126 } bhv_identity_t;
 127
 128 typedef bhv_identity_t bhv_position_t;
 129
 130 #define BHV_IDENTITY_INIT(id,pos)       {id, pos}
 131 #define BHV_IDENTITY_INIT_POSITION(pos) BHV_IDENTITY_INIT(0, pos)
 132
 133 /*
 134  * Define boundaries of position values.
 135  */
 136 #define BHV_POSITION_INVALID    0       /* invalid position number */
 137 #define BHV_POSITION_BASE       1       /* base (last) implementation layer */
 138 #define BHV_POSITION_TOP        63      /* top (first) implementation layer */
 139
 140 /*
 141  * Plumbing macros.
 142  */
 143 #define BHV_HEAD_FIRST(bhp)     (ASSERT((bhp)->bh_first), (bhp)->bh_first)
 144 #define BHV_NEXT(bdp)           (ASSERT((bdp)->bd_next), (bdp)->bd_next)
 145 #define BHV_NEXTNULL(bdp)       ((bdp)->bd_next)
 146 #define BHV_VOBJ(bdp)           (ASSERT((bdp)->bd_vobj), (bdp)->bd_vobj)
 147 #define BHV_VOBJNULL(bdp)       ((bdp)->bd_vobj)
 148 #define BHV_PDATA(bdp)          (bdp)->bd_pdata
 149 #define BHV_OPS(bdp)            (bdp)->bd_ops
 150 #define BHV_IDENTITY(bdp)       ((bhv_identity_t *)(bdp)->bd_ops)
 151 #define BHV_POSITION(bdp)       (BHV_IDENTITY(bdp)->bi_position)
 152
 153 extern void bhv_head_init(bhv_head_t *, char *);
 154 extern void bhv_head_destroy(bhv_head_t *);
 155 extern int  bhv_insert(bhv_head_t *, bhv_desc_t *);
 156 extern void bhv_insert_initial(bhv_head_t *, bhv_desc_t *);
 157
 158 /*
 159  * Initialize a new behavior descriptor.
 160  * Arguments:
 161  *   bdp - pointer to behavior descriptor
 162  *   pdata - pointer to behavior's private data
 163  *   vobj - pointer to associated virtual object
 164  *   ops - pointer to ops for this behavior
 165  */
 166 #define bhv_desc_init(bdp, pdata, vobj, ops)            \
 167  {                                                      \
 168         (bdp)->bd_pdata = pdata;                        \
 169         (bdp)->bd_vobj = vobj;                          \
 170         (bdp)->bd_ops = ops;                            \
 171         (bdp)->bd_next = NULL;                          \
 172  }
 173
 174 /*
 175  * Remove a behavior descriptor from a behavior chain.
 176  */
 177 #define bhv_remove(bhp, bdp)                            \
 178  {                                                      \
 179         if ((bhp)->bh_first == (bdp)) {                 \
 180                 /*                                      \
 181                 * Remove from front of chain.           \
 182                 * Atomic wrt oip's.                     \
 183                 */                                      \
 184                (bhp)->bh_first = (bdp)->bd_next;        \
 185         } else {                                        \
 186                /* remove from non-front of chain */     \
 187                bhv_remove_not_first(bhp, bdp);          \
 188         }                                               \
 189         (bdp)->bd_vobj = NULL;                          \
 190  }
 191
 192 /*
 193  * Behavior module prototypes.
 194  */
 195 extern void             bhv_remove_not_first(bhv_head_t *bhp, bhv_desc_t *bdp);
 196 extern bhv_desc_t *     bhv_lookup(bhv_head_t *bhp, void *ops);
 197 extern bhv_desc_t *     bhv_lookup_range(bhv_head_t *bhp, int low, int high);
 198 extern bhv_desc_t *     bhv_base(bhv_head_t *bhp);
 199
 200 /* No bhv locking on Linux */
 201 #define bhv_lookup_unlocked     bhv_lookup
 202 #define bhv_base_unlocked       bhv_base
 203
 204 #endif /* __XFS_BEHAVIOR_H__ */