1/* 2 * Copyright (c) 2000-2003,2005 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_BEHAVIOR_H__ 19#define __XFS_BEHAVIOR_H__ 20 21/* 22 * Header file used to associate behaviors with virtualized objects. 23 * 24 * A virtualized object is an internal, virtualized representation of 25 * OS entities such as persistent files, processes, or sockets. Examples 26 * of virtualized objects include vnodes, vprocs, and vsockets. Often 27 * a virtualized object is referred to simply as an "object." 28 * 29 * A behavior is essentially an implementation layer associated with 30 * an object. Multiple behaviors for an object are chained together, 31 * the order of chaining determining the order of invocation. Each 32 * behavior of a given object implements the same set of interfaces 33 * (e.g., the VOP interfaces). 34 * 35 * Behaviors may be dynamically inserted into an object's behavior chain, 36 * such that the addition is transparent to consumers that already have 37 * references to the object. Typically, a given behavior will be inserted 38 * at a particular location in the behavior chain. Insertion of new 39 * behaviors is synchronized with operations-in-progress (oip's) so that 40 * the oip's always see a consistent view of the chain. 41 * 42 * The term "interposition" is used to refer to the act of inserting 43 * a behavior such that it interposes on (i.e., is inserted in front 44 * of) a particular other behavior. A key example of this is when a 45 * system implementing distributed single system image wishes to 46 * interpose a distribution layer (providing distributed coherency) 47 * in front of an object that is otherwise only accessed locally. 48 * 49 * Note that the traditional vnode/inode combination is simply a virtualized 50 * object that has exactly one associated behavior. 51 * 52 * Behavior synchronization is logic which is necessary under certain 53 * circumstances that there is no conflict between ongoing operations 54 * traversing the behavior chain and those dynamically modifying the 55 * behavior chain. Because behavior synchronization adds extra overhead 56 * to virtual operation invocation, we want to restrict, as much as 57 * we can, the requirement for this extra code, to those situations 58 * in which it is truly necessary. 59 * 60 * Behavior synchronization is needed whenever there's at least one class 61 * of object in the system for which: 62 * 1) multiple behaviors for a given object are supported, 63 * -- AND -- 64 * 2a) insertion of a new behavior can happen dynamically at any time during 65 * the life of an active object, 66 * -- AND -- 67 * 3a) insertion of a new behavior needs to synchronize with existing 68 * ops-in-progress. 69 * -- OR -- 70 * 3b) multiple different behaviors can be dynamically inserted at 71 * any time during the life of an active object 72 * -- OR -- 73 * 3c) removal of a behavior can occur at any time during the life of 74 * an active object. 75 * -- OR -- 76 * 2b) removal of a behavior can occur at any time during the life of an 77 * active object 78 * 79 */ 80 81/* 82 * Behavior head. Head of the chain of behaviors. 83 * Contained within each virtualized object data structure. 84 */ 85typedef struct bhv_head { 86 struct bhv_desc *bh_first; /* first behavior in chain */ 87} bhv_head_t; 88 89/* 90 * Behavior descriptor. Descriptor associated with each behavior. 91 * Contained within the behavior's private data structure. 92 */ 93typedef struct bhv_desc { 94 void *bd_pdata; /* private data for this behavior */ 95 void *bd_vobj; /* virtual object associated with */ 96 void *bd_ops; /* ops for this behavior */ 97 struct bhv_desc *bd_next; /* next behavior in chain */ 98} bhv_desc_t; 99 100/* 101 * Behavior identity field. A behavior's identity determines the position 102 * where it lives within a behavior chain, and it's always the first field 103 * of the behavior's ops vector. The optional id field further identifies the 104 * subsystem responsible for the behavior. 105 */ 106typedef struct bhv_identity { 107 __u16 bi_id; /* owning subsystem id */ 108 __u16 bi_position; /* position in chain */ 109} bhv_identity_t; 110 111typedef bhv_identity_t bhv_position_t; 112 113#define BHV_IDENTITY_INIT(id,pos) {id, pos} 114#define BHV_IDENTITY_INIT_POSITION(pos) BHV_IDENTITY_INIT(0, pos) 115 116/* 117 * Define boundaries of position values. 118 */ 119#define BHV_POSITION_INVALID 0 /* invalid position number */ 120#define BHV_POSITION_BASE 1 /* base (last) implementation layer */ 121#define BHV_POSITION_TOP 63 /* top (first) implementation layer */ 122 123/* 124 * Plumbing macros. 125 */ 126#define BHV_HEAD_FIRST(bhp) (ASSERT((bhp)->bh_first), (bhp)->bh_first) 127#define BHV_NEXT(bdp) (ASSERT((bdp)->bd_next), (bdp)->bd_next) 128#define BHV_NEXTNULL(bdp) ((bdp)->bd_next) 129#define BHV_VOBJ(bdp) (ASSERT((bdp)->bd_vobj), (bdp)->bd_vobj) 130#define BHV_VOBJNULL(bdp) ((bdp)->bd_vobj) 131#define BHV_PDATA(bdp) (bdp)->bd_pdata 132#define BHV_OPS(bdp) (bdp)->bd_ops 133#define BHV_IDENTITY(bdp) ((bhv_identity_t *)(bdp)->bd_ops) 134#define BHV_POSITION(bdp) (BHV_IDENTITY(bdp)->bi_position) 135 136extern void bhv_head_init(bhv_head_t *, char *); 137extern void bhv_head_destroy(bhv_head_t *); 138extern int bhv_insert(bhv_head_t *, bhv_desc_t *); 139extern void bhv_insert_initial(bhv_head_t *, bhv_desc_t *); 140 141/* 142 * Initialize a new behavior descriptor. 143 * Arguments: 144 * bdp - pointer to behavior descriptor 145 * pdata - pointer to behavior's private data 146 * vobj - pointer to associated virtual object 147 * ops - pointer to ops for this behavior 148 */ 149#define bhv_desc_init(bdp, pdata, vobj, ops) \ 150 { \ 151 (bdp)->bd_pdata = pdata; \ 152 (bdp)->bd_vobj = vobj; \ 153 (bdp)->bd_ops = ops; \ 154 (bdp)->bd_next = NULL; \ 155 } 156 157/* 158 * Remove a behavior descriptor from a behavior chain. 159 */ 160#define bhv_remove(bhp, bdp) \ 161 { \ 162 if ((bhp)->bh_first == (bdp)) { \ 163 /* \ 164 * Remove from front of chain. \ 165 * Atomic wrt oip's. \ 166 */ \ 167 (bhp)->bh_first = (bdp)->bd_next; \ 168 } else { \ 169 /* remove from non-front of chain */ \ 170 bhv_remove_not_first(bhp, bdp); \ 171 } \ 172 (bdp)->bd_vobj = NULL; \ 173 } 174 175/* 176 * Behavior module prototypes. 177 */ 178extern void bhv_remove_not_first(bhv_head_t *bhp, bhv_desc_t *bdp); 179extern bhv_desc_t * bhv_lookup_range(bhv_head_t *bhp, int low, int high); 180extern bhv_desc_t * bhv_base(bhv_head_t *bhp); 181 182/* No bhv locking on Linux */ 183#define bhv_base_unlocked bhv_base 184 185#endif /* __XFS_BEHAVIOR_H__ */ 186