HAMMER 46/Many: Performance pass, media changes, bug fixes.
[dragonfly.git] / sys / vfs / hammer / hammer_btree.h
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1/*
2 * Copyright (c) 2007 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
2f85fa4d 34 * $DragonFly: src/sys/vfs/hammer/hammer_btree.h,v 1.16 2008/05/18 01:48:50 dillon Exp $
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35 */
36
37/*
8cd0a023 38 * HAMMER B-Tree index
8750964d 39 *
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40 * HAMMER implements a modified B+Tree. B+Trees store records only
41 * at their leaves and HAMMER's modification is to adjust the internal
42 * elements so there is a boundary element on each side instead of sub-tree
43 * pointers.
8750964d 44 *
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45 * We just call our modified B+Tree a 'B-Tree' in HAMMER documentation to
46 * reduce confusion.
47 *
48 * A B-Tree internal node looks like this:
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49 *
50 * B N N N N N N B <-- boundary and internal elements
51 * S S S S S S S <-- subtree pointers
52 *
8cd0a023 53 * A B-Tree leaf node looks like this:
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54 *
55 * L L L L L L L L <-- leaf elemenets
56 * (there is also a previous and next-leaf pointer)
57 *
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58 * The recursion radix of an internal node is reduced by 1 relative to
59 * a normal B-Tree in order to accomodate the right-hand boundary.
60 *
61 * The big benefit to using a B-Tree with built-in bounds information is
62 * that it makes it possible to cache pointers into the middle of the tree
63 * and not have to start searches, insertions, OR deletions at the root node.
64 * The boundary elements allow searches to progress in a definitive direction
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65 * from any point in the tree without revisting nodes. It is also possible
66 * to terminate searches early and make minor adjustments to the boundaries
67 * (within the confines of the parent's boundaries) on the fly. This greatly
11ad5ade 68 * improves the efficiency of many operations.
427e5fc6 69 *
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70 * HAMMER B-Trees are per-cluster. The global multi-cluster B-Tree is
71 * constructed by allowing internal nodes to link to the roots of other
72 * clusters. Fields in the cluster header then reference back to its
73 * parent and use the cluster generation number to detect stale linkages.
427e5fc6 74 *
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75 * The B-Tree balancing code can operate within a cluster or across the
76 * filesystem's ENTIRE B-Tree super-structure. A cluster's B-Tree root
77 * can be a leaf node in the worse case. A cluster is guarenteed to have
78 * sufficient free space to hold a single completely full leaf in the
79 * degenerate case.
427e5fc6 80 *
8cd0a023 81 * All of the structures below are on-disk structures.
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82 */
83
84/*
8cd0a023 85 * Common base for all B-Tree element types (40 bytes)
c60bb2c5 86 *
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87 * obj_type is set to the object type the record represents if an inode,
88 * directory entry, or an inter-cluster reference. A cluster range is
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89 * special in that the B-Tree nodes represent a range within the B-Tree
90 * inclusive of rec_type field, so obj_type must be used to detect the
91 * cluster range entries.
427e5fc6 92 *
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93 * btype is only used by the elements making up an internal or leaf B-Tree
94 * node and applies to the node rather then to the key. This means that
95 * btype must be assigned/reassigned after any update to the base_elm making
96 * up a B-Tree element.
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97 */
98struct hammer_base_elm {
99 int64_t obj_id; /* 00 object record is associated with */
100 int64_t key; /* 08 indexing key (offset or namekey) */
101
102 hammer_tid_t create_tid; /* 10 transaction id for record creation */
103 hammer_tid_t delete_tid; /* 18 transaction id for record update/del */
104
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105 u_int16_t rec_type; /* 20 _RECTYPE_ */
106 u_int8_t obj_type; /* 22 _OBJTYPE_ (restricted) */
fe7678ee 107 u_int8_t btype; /* 23 B-Tree element type */
2f85fa4d 108 u_int32_t localization; /* 24 B-Tree localization parameter */
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109 /* 28 */
110};
111
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112typedef struct hammer_base_elm *hammer_base_elm_t;
113
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114/*
115 * Localization has sorting priority over the obj_id and is used to
116 * localize inodes for very fast directory scans.
117 */
118#define HAMMER_LOCALIZE_RESERVED00 0x00000000
119#define HAMMER_LOCALIZE_INODE 0x00000001
120#define HAMMER_LOCALIZE_MISC 0x00000002
121#define HAMMER_LOCALIZE_RESERVED03 0x00000003
122
123#define HAMMER_MIN_LOCALIZATION 0x00000000U
124#define HAMMER_MAX_LOCALIZATION 0xFFFFFFFFU
125
427e5fc6 126/*
47197d71 127 * Internal element (40 + 24 = 64 bytes).
8cd0a023 128 *
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129 * An internal element contains the left-hand boundary, right-hand boundary,
130 * and a recursion to another B-Tree node.
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131 */
132struct hammer_btree_internal_elm {
133 struct hammer_base_elm base;
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134 hammer_off_t unused00;
135 hammer_off_t subtree_offset;
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136 int32_t unused02;
137 int32_t unused03;
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138};
139
8750964d 140/*
47197d71 141 * Leaf B-Tree element (40 + 24 = 64 bytes).
8cd0a023 142 *
47197d71 143 * A leaf element.
8750964d 144 */
8cd0a023 145struct hammer_btree_leaf_elm {
8750964d 146 struct hammer_base_elm base;
11ad5ade 147 hammer_off_t atime; /* access time */
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148 hammer_off_t data_offset;
149 int32_t data_len;
150 hammer_crc_t data_crc;
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151};
152
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153typedef struct hammer_btree_leaf_elm *hammer_btree_leaf_elm_t;
154
8750964d 155/*
47197d71 156 * Rollup btree leaf element types - 64 byte structure
8750964d 157 */
8cd0a023 158union hammer_btree_elm {
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159 struct hammer_base_elm base;
160 struct hammer_btree_leaf_elm leaf;
8cd0a023 161 struct hammer_btree_internal_elm internal;
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162};
163
8cd0a023 164typedef union hammer_btree_elm *hammer_btree_elm_t;
427e5fc6 165
8750964d 166/*
40043e7f 167 * B-Tree node (normal or meta) (16x64 = 1K structure)
427e5fc6 168 *
40043e7f 169 * Each node contains 15 elements. The last element for an internal node
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170 * is the right-boundary so internal nodes have one fewer logical elements
171 * then leaf nodes.
427e5fc6 172 *
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173 * 'count' always refers to the number of elements and is non-inclusive of
174 * the right-hand boundary for an internal node.
427e5fc6 175 *
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176 * NOTE: The node head for an internal does not contain the subtype
177 * (The B-Tree node type for the nodes referenced by its elements).
178 * Instead, each element specifies the subtype (elm->base.subtype).
179 * This allows us to maintain an unbalanced B-Tree and to easily identify
180 * special inter-cluster link elements.
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181 *
182 * NOTE: FUTURE EXPANSION: The reserved fields in hammer_node_ondisk are
183 * reserved for left/right leaf linkage fields, flags, and other future
184 * features.
427e5fc6 185 */
40043e7f 186#define HAMMER_BTREE_LEAF_ELMS 15
8cd0a023 187#define HAMMER_BTREE_INT_ELMS (HAMMER_BTREE_LEAF_ELMS - 1)
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188
189/*
190 * It is safe to combine two adjacent nodes if the total number of elements
191 * is less then or equal to the *_FILL constant.
8750964d 192 */
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193#define HAMMER_BTREE_LEAF_FILL (HAMMER_BTREE_LEAF_ELMS - 3)
194#define HAMMER_BTREE_INT_FILL (HAMMER_BTREE_INT_ELMS - 3)
195
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196#define HAMMER_BTREE_TYPE_INTERNAL ((u_int8_t)'I')
197#define HAMMER_BTREE_TYPE_LEAF ((u_int8_t)'L')
fe7678ee 198#define HAMMER_BTREE_TYPE_RECORD ((u_int8_t)'R')
f36a9737 199#define HAMMER_BTREE_TYPE_DELETED ((u_int8_t)'D')
427e5fc6 200
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201struct hammer_node_ondisk {
202 /*
47197d71 203 * B-Tree node header (64 bytes)
8cd0a023 204 */
19619882 205 hammer_crc_t crc; /* MUST BE FIRST FIELD OF STRUCTURE */
40043e7f 206 u_int32_t signature;
47197d71 207 hammer_off_t parent; /* 0 if at root of cluster */
427e5fc6 208 int32_t count;
427e5fc6 209 u_int8_t type;
8cd0a023 210 u_int8_t reserved01;
427e5fc6 211 u_int16_t reserved02;
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212 hammer_off_t reserved03; /* future link_left */
213 hammer_off_t reserved04; /* future link_right */
214 hammer_off_t reserved05;
215 hammer_off_t reserved06;
40043e7f 216 hammer_off_t reserved07;
8750964d 217
8750964d 218 /*
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219 * Element array. Internal nodes have one less logical element
220 * (meaning: the same number of physical elements) in order to
221 * accomodate the right-hand boundary. The left-hand boundary
222 * is integrated into the first element. Leaf nodes have no
223 * boundary elements.
8750964d 224 */
8cd0a023 225 union hammer_btree_elm elms[HAMMER_BTREE_LEAF_ELMS];
427e5fc6 226};
8750964d 227
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228#define HAMMER_BTREE_SIGNATURE_GOOD 0xB3A49586
229#define HAMMER_BTREE_SIGNATURE_DESTROYED 0x4A3B2C1D
230#define HAMMER_BTREE_CRCSIZE \
231 (sizeof(struct hammer_node_ondisk) - sizeof(hammer_crc_t))
232
8cd0a023 233typedef struct hammer_node_ondisk *hammer_node_ondisk_t;
427e5fc6 234