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1da177e4 | 1 | /* |
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2 | * Copyright (c) 2000-2003,2005 Silicon Graphics, Inc. |
3 | * All Rights Reserved. | |
1da177e4 | 4 | * |
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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 | |
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7 | * published by the Free Software Foundation. |
8 | * | |
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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. | |
1da177e4 | 13 | * |
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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 | |
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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 | * | |
c41564b5 | 42 | * The term "interposition" is used to refer to the act of inserting |
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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 | |
c41564b5 | 54 | * traversing the behavior chain and those dynamically modifying the |
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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 | ||
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81 | /* |
82 | * Behavior head. Head of the chain of behaviors. | |
83 | * Contained within each virtualized object data structure. | |
84 | */ | |
85 | typedef struct bhv_head { | |
86 | struct bhv_desc *bh_first; /* first behavior in chain */ | |
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87 | } bhv_head_t; |
88 | ||
89 | /* | |
90 | * Behavior descriptor. Descriptor associated with each behavior. | |
91 | * Contained within the behavior's private data structure. | |
92 | */ | |
93 | typedef 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 | */ | |
106 | typedef struct bhv_identity { | |
107 | __u16 bi_id; /* owning subsystem id */ | |
108 | __u16 bi_position; /* position in chain */ | |
109 | } bhv_identity_t; | |
110 | ||
111 | typedef 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 | ||
136 | extern void bhv_head_init(bhv_head_t *, char *); | |
137 | extern void bhv_head_destroy(bhv_head_t *); | |
138 | extern int bhv_insert(bhv_head_t *, bhv_desc_t *); | |
139 | extern 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 | */ | |
178 | extern void bhv_remove_not_first(bhv_head_t *bhp, bhv_desc_t *bdp); | |
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179 | extern bhv_desc_t * bhv_lookup_range(bhv_head_t *bhp, int low, int high); |
180 | extern bhv_desc_t * bhv_base(bhv_head_t *bhp); | |
181 | ||
182 | /* No bhv locking on Linux */ | |
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183 | #define bhv_base_unlocked bhv_base |
184 | ||
185 | #endif /* __XFS_BEHAVIOR_H__ */ |