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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__ */ |