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__ */ 205