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 struct bhv_head_lock; 82 83 /* 84 * Behavior head. Head of the chain of behaviors. 85 * Contained within each virtualized object data structure. 86 */ 87 typedef struct bhv_head { 88 struct bhv_desc *bh_first; /* first behavior in chain */ 89 struct bhv_head_lock *bh_lockp; /* pointer to lock info struct */ 90 } bhv_head_t; 91 92 /* 93 * Behavior descriptor. Descriptor associated with each behavior. 94 * Contained within the behavior's private data structure. 95 */ 96 typedef struct bhv_desc { 97 void *bd_pdata; /* private data for this behavior */ 98 void *bd_vobj; /* virtual object associated with */ 99 void *bd_ops; /* ops for this behavior */ 100 struct bhv_desc *bd_next; /* next behavior in chain */ 101 } bhv_desc_t; 102 103 /* 104 * Behavior identity field. A behavior's identity determines the position 105 * where it lives within a behavior chain, and it's always the first field 106 * of the behavior's ops vector. The optional id field further identifies the 107 * subsystem responsible for the behavior. 108 */ 109 typedef struct bhv_identity { 110 __u16 bi_id; /* owning subsystem id */ 111 __u16 bi_position; /* position in chain */ 112 } bhv_identity_t; 113 114 typedef bhv_identity_t bhv_position_t; 115 116 #define BHV_IDENTITY_INIT(id,pos) {id, pos} 117 #define BHV_IDENTITY_INIT_POSITION(pos) BHV_IDENTITY_INIT(0, pos) 118 119 /* 120 * Define boundaries of position values. 121 */ 122 #define BHV_POSITION_INVALID 0 /* invalid position number */ 123 #define BHV_POSITION_BASE 1 /* base (last) implementation layer */ 124 #define BHV_POSITION_TOP 63 /* top (first) implementation layer */ 125 126 /* 127 * Plumbing macros. 128 */ 129 #define BHV_HEAD_FIRST(bhp) (ASSERT((bhp)->bh_first), (bhp)->bh_first) 130 #define BHV_NEXT(bdp) (ASSERT((bdp)->bd_next), (bdp)->bd_next) 131 #define BHV_NEXTNULL(bdp) ((bdp)->bd_next) 132 #define BHV_VOBJ(bdp) (ASSERT((bdp)->bd_vobj), (bdp)->bd_vobj) 133 #define BHV_VOBJNULL(bdp) ((bdp)->bd_vobj) 134 #define BHV_PDATA(bdp) (bdp)->bd_pdata 135 #define BHV_OPS(bdp) (bdp)->bd_ops 136 #define BHV_IDENTITY(bdp) ((bhv_identity_t *)(bdp)->bd_ops) 137 #define BHV_POSITION(bdp) (BHV_IDENTITY(bdp)->bi_position) 138 139 extern void bhv_head_init(bhv_head_t *, char *); 140 extern void bhv_head_destroy(bhv_head_t *); 141 extern int bhv_insert(bhv_head_t *, bhv_desc_t *); 142 extern void bhv_insert_initial(bhv_head_t *, bhv_desc_t *); 143 144 /* 145 * Initialize a new behavior descriptor. 146 * Arguments: 147 * bdp - pointer to behavior descriptor 148 * pdata - pointer to behavior's private data 149 * vobj - pointer to associated virtual object 150 * ops - pointer to ops for this behavior 151 */ 152 #define bhv_desc_init(bdp, pdata, vobj, ops) \ 153 { \ 154 (bdp)->bd_pdata = pdata; \ 155 (bdp)->bd_vobj = vobj; \ 156 (bdp)->bd_ops = ops; \ 157 (bdp)->bd_next = NULL; \ 158 } 159 160 /* 161 * Remove a behavior descriptor from a behavior chain. 162 */ 163 #define bhv_remove(bhp, bdp) \ 164 { \ 165 if ((bhp)->bh_first == (bdp)) { \ 166 /* \ 167 * Remove from front of chain. \ 168 * Atomic wrt oip's. \ 169 */ \ 170 (bhp)->bh_first = (bdp)->bd_next; \ 171 } else { \ 172 /* remove from non-front of chain */ \ 173 bhv_remove_not_first(bhp, bdp); \ 174 } \ 175 (bdp)->bd_vobj = NULL; \ 176 } 177 178 /* 179 * Behavior module prototypes. 180 */ 181 extern void bhv_remove_not_first(bhv_head_t *bhp, bhv_desc_t *bdp); 182 extern bhv_desc_t * bhv_lookup(bhv_head_t *bhp, void *ops); 183 extern bhv_desc_t * bhv_lookup_range(bhv_head_t *bhp, int low, int high); 184 extern bhv_desc_t * bhv_base(bhv_head_t *bhp); 185 186 /* No bhv locking on Linux */ 187 #define bhv_lookup_unlocked bhv_lookup 188 #define bhv_base_unlocked bhv_base 189 190 #endif /* __XFS_BEHAVIOR_H__ */ 191