2 * linux/fs/befs/btree.c
4 * Copyright (C) 2001-2002 Will Dyson <will_dyson@pobox.com>
6 * Licensed under the GNU GPL. See the file COPYING for details.
8 * 2002-02-05: Sergey S. Kostyliov added binary search withing
13 * Dominic Giampaolo, author of "Practical File System
14 * Design with the Be File System", for such a helpful book.
16 * Marcus J. Ranum, author of the b+tree package in
17 * comp.sources.misc volume 10. This code is not copied from that
18 * work, but it is partially based on it.
20 * Makoto Kato, author of the original BeFS for linux filesystem
24 #include <linux/kernel.h>
25 #include <linux/string.h>
26 #include <linux/slab.h>
31 #include "datastream.h"
35 * The btree functions in this file are built on top of the
36 * datastream.c interface, which is in turn built on top of the
40 /* Befs B+tree structure:
42 * The first thing in the tree is the tree superblock. It tells you
43 * all kinds of usefull things about the tree, like where the rootnode
44 * is located, and the size of the nodes (always 1024 with current version
47 * The rest of the tree consists of a series of nodes. Nodes contain a header
48 * (struct befs_btree_nodehead), the packed key data, an array of shorts
49 * containing the ending offsets for each of the keys, and an array of
50 * befs_off_t values. In interior nodes, the keys are the ending keys for
51 * the childnode they point to, and the values are offsets into the
52 * datastream containing the tree.
57 * The book states 2 confusing things about befs b+trees. First,
58 * it states that the overflow feild of node headers is used by internal nodes
59 * to point to another node that "effectivly continues this one". Here is what
60 * I belive that means. Each key in internal nodes points to another node that
61 * contains key values less than itself. Inspection reveals that the last key
62 * in the internal node is not the last key in the index. Keys that are
63 * greater than the last key in the internal node go into the overflow node.
64 * I imagine there is a performance reason for this.
66 * Second, it states that the header of a btree node is sufficient to
67 * distinguish internal nodes from leaf nodes. Without saying exactly how.
68 * After figuring out the first, it becomes obvious that internal nodes have
69 * overflow nodes and leafnodes do not.
73 * Currently, this code is only good for directory B+trees.
74 * In order to be used for other BFS indexes, it needs to be extended to handle
75 * duplicate keys and non-string keytypes (int32, int64, float, double).
79 * In memory structure of each btree node
82 befs_btree_nodehead head; /* head of node converted to cpu byteorder */
83 struct buffer_head *bh;
84 befs_btree_nodehead *od_node; /* on disk node */
88 const static befs_off_t befs_bt_inval = 0xffffffffffffffffULL;
91 static int befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
92 befs_btree_super * bt_super,
93 befs_btree_node * this_node,
94 befs_off_t * node_off);
96 static int befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
97 befs_btree_super * sup);
99 static int befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
100 befs_btree_node * node, befs_off_t node_off);
102 static int befs_leafnode(befs_btree_node * node);
104 static u16 *befs_bt_keylen_index(befs_btree_node * node);
106 static befs_off_t *befs_bt_valarray(befs_btree_node * node);
108 static char *befs_bt_keydata(befs_btree_node * node);
110 static int befs_find_key(struct super_block *sb, befs_btree_node * node,
111 const char *findkey, befs_off_t * value);
113 static char *befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
114 int index, u16 * keylen);
116 static int befs_compare_strings(const void *key1, int keylen1,
117 const void *key2, int keylen2);
120 * befs_bt_read_super - read in btree superblock convert to cpu byteorder
121 * @sb: Filesystem superblock
122 * @ds: Datastream to read from
123 * @sup: Buffer in which to place the btree superblock
125 * Calls befs_read_datastream to read in the btree superblock and
126 * makes sure it is in cpu byteorder, byteswapping if nessisary.
128 * On success, returns BEFS_OK and *@sup contains the btree superblock,
131 * On failure, BEFS_ERR is returned.
134 befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
135 befs_btree_super * sup)
137 struct buffer_head *bh = NULL;
138 befs_btree_super *od_sup = NULL;
140 befs_debug(sb, "---> befs_btree_read_super()");
142 bh = befs_read_datastream(sb, ds, 0, NULL);
145 befs_error(sb, "Couldn't read index header.");
148 od_sup = (befs_btree_super *) bh->b_data;
149 befs_dump_index_entry(sb, od_sup);
151 sup->magic = fs32_to_cpu(sb, od_sup->magic);
152 sup->node_size = fs32_to_cpu(sb, od_sup->node_size);
153 sup->max_depth = fs32_to_cpu(sb, od_sup->max_depth);
154 sup->data_type = fs32_to_cpu(sb, od_sup->data_type);
155 sup->root_node_ptr = fs64_to_cpu(sb, od_sup->root_node_ptr);
156 sup->free_node_ptr = fs64_to_cpu(sb, od_sup->free_node_ptr);
157 sup->max_size = fs64_to_cpu(sb, od_sup->max_size);
160 if (sup->magic != BEFS_BTREE_MAGIC) {
161 befs_error(sb, "Index header has bad magic.");
165 befs_debug(sb, "<--- befs_btree_read_super()");
169 befs_debug(sb, "<--- befs_btree_read_super() ERROR");
174 * befs_bt_read_node - read in btree node and convert to cpu byteorder
175 * @sb: Filesystem superblock
176 * @ds: Datastream to read from
177 * @node: Buffer in which to place the btree node
178 * @node_off: Starting offset (in bytes) of the node in @ds
180 * Calls befs_read_datastream to read in the indicated btree node and
181 * makes sure its header feilds are in cpu byteorder, byteswapping if
183 * Note: node->bh must be NULL when this function called first
184 * time. Don't forget brelse(node->bh) after last call.
186 * On success, returns BEFS_OK and *@node contains the btree node that
187 * starts at @node_off, with the node->head fields in cpu byte order.
189 * On failure, BEFS_ERR is returned.
193 befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
194 befs_btree_node * node, befs_off_t node_off)
198 befs_debug(sb, "---> befs_bt_read_node()");
203 node->bh = befs_read_datastream(sb, ds, node_off, &off);
205 befs_error(sb, "befs_bt_read_node() failed to read "
206 "node at %Lu", node_off);
207 befs_debug(sb, "<--- befs_bt_read_node() ERROR");
212 (befs_btree_nodehead *) ((void *) node->bh->b_data + off);
214 befs_dump_index_node(sb, node->od_node);
216 node->head.left = fs64_to_cpu(sb, node->od_node->left);
217 node->head.right = fs64_to_cpu(sb, node->od_node->right);
218 node->head.overflow = fs64_to_cpu(sb, node->od_node->overflow);
219 node->head.all_key_count =
220 fs16_to_cpu(sb, node->od_node->all_key_count);
221 node->head.all_key_length =
222 fs16_to_cpu(sb, node->od_node->all_key_length);
224 befs_debug(sb, "<--- befs_btree_read_node()");
229 * befs_btree_find - Find a key in a befs B+tree
230 * @sb: Filesystem superblock
231 * @ds: Datastream containing btree
232 * @key: Key string to lookup in btree
233 * @value: Value stored with @key
235 * On sucess, returns BEFS_OK and sets *@value to the value stored
236 * with @key (usually the disk block number of an inode).
238 * On failure, returns BEFS_ERR or BEFS_BT_NOT_FOUND.
241 * Read the superblock and rootnode of the b+tree.
242 * Drill down through the interior nodes using befs_find_key().
243 * Once at the correct leaf node, use befs_find_key() again to get the
244 * actuall value stored with the key.
247 befs_btree_find(struct super_block *sb, befs_data_stream * ds,
248 const char *key, befs_off_t * value)
250 befs_btree_node *this_node = NULL;
251 befs_btree_super bt_super;
255 befs_debug(sb, "---> befs_btree_find() Key: %s", key);
257 if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
259 "befs_btree_find() failed to read index superblock");
263 this_node = (befs_btree_node *) kmalloc(sizeof (befs_btree_node),
266 befs_error(sb, "befs_btree_find() failed to allocate %u "
267 "bytes of memory", sizeof (befs_btree_node));
271 this_node->bh = NULL;
273 /* read in root node */
274 node_off = bt_super.root_node_ptr;
275 if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
276 befs_error(sb, "befs_btree_find() failed to read "
277 "node at %Lu", node_off);
281 while (!befs_leafnode(this_node)) {
282 res = befs_find_key(sb, this_node, key, &node_off);
283 if (res == BEFS_BT_NOT_FOUND)
284 node_off = this_node->head.overflow;
285 /* if no match, go to overflow node */
286 if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
287 befs_error(sb, "befs_btree_find() failed to read "
288 "node at %Lu", node_off);
293 /* at the correct leaf node now */
295 res = befs_find_key(sb, this_node, key, value);
297 brelse(this_node->bh);
300 if (res != BEFS_BT_MATCH) {
301 befs_debug(sb, "<--- befs_btree_find() Key %s not found", key);
303 return BEFS_BT_NOT_FOUND;
305 befs_debug(sb, "<--- befs_btree_find() Found key %s, value %Lu",
313 befs_debug(sb, "<--- befs_btree_find() ERROR");
318 * befs_find_key - Search for a key within a node
319 * @sb: Filesystem superblock
320 * @node: Node to find the key within
321 * @key: Keystring to search for
322 * @value: If key is found, the value stored with the key is put here
324 * finds exact match if one exists, and returns BEFS_BT_MATCH
325 * If no exact match, finds first key in node that is greater
326 * (alpabeticly) than the search key and returns BEFS_BT_PARMATCH
327 * (for partial match, I guess). Can you think of something better to
330 * If no key was a match or greater than the search key, return
333 * Use binary search instead of a linear.
336 befs_find_key(struct super_block *sb, befs_btree_node * node,
337 const char *findkey, befs_off_t * value)
339 int first, last, mid;
344 befs_off_t *valarray;
346 befs_debug(sb, "---> befs_find_key() %s", findkey);
350 findkey_len = strlen(findkey);
352 /* if node can not contain key, just skeep this node */
353 last = node->head.all_key_count - 1;
354 thiskey = befs_bt_get_key(sb, node, last, &keylen);
356 eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len);
358 befs_debug(sb, "<--- befs_find_key() %s not found", findkey);
359 return BEFS_BT_NOT_FOUND;
362 valarray = befs_bt_valarray(node);
364 /* simple binary search */
367 while (last >= first) {
368 mid = (last + first) / 2;
369 befs_debug(sb, "first: %d, last: %d, mid: %d", first, last,
371 thiskey = befs_bt_get_key(sb, node, mid, &keylen);
372 eq = befs_compare_strings(thiskey, keylen, findkey,
374 *value = fs64_to_cpu(sb, valarray[mid]);
377 befs_debug(sb, "<--- befs_find_key() found %s at %d",
380 return BEFS_BT_MATCH;
388 *value = fs64_to_cpu(sb, valarray[mid + 1]);
389 befs_debug(sb, "<--- befs_find_key() found %s at %d", thiskey, mid);
390 return BEFS_BT_PARMATCH;
394 * befs_btree_read - Traverse leafnodes of a btree
395 * @sb: Filesystem superblock
396 * @ds: Datastream containing btree
397 * @key_no: Key number (alphabetical order) of key to read
398 * @bufsize: Size of the buffer to return key in
399 * @keybuf: Pointer to a buffer to put the key in
400 * @keysize: Length of the returned key
401 * @value: Value stored with the returned key
403 * Heres how it works: Key_no is the index of the key/value pair to
404 * retun in keybuf/value.
405 * Bufsize is the size of keybuf (BEFS_NAME_LEN+1 is a good size). Keysize is
406 * the number of charecters in the key (just a convience).
409 * Get the first leafnode of the tree. See if the requested key is in that
410 * node. If not, follow the node->right link to the next leafnode. Repeat
411 * until the (key_no)th key is found or the tree is out of keys.
414 befs_btree_read(struct super_block *sb, befs_data_stream * ds,
415 loff_t key_no, size_t bufsize, char *keybuf, size_t * keysize,
418 befs_btree_node *this_node;
419 befs_btree_super bt_super;
420 befs_off_t node_off = 0;
422 befs_off_t *valarray;
429 befs_debug(sb, "---> befs_btree_read()");
431 if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
433 "befs_btree_read() failed to read index superblock");
437 if ((this_node = (befs_btree_node *)
438 kmalloc(sizeof (befs_btree_node), GFP_NOFS)) == NULL) {
439 befs_error(sb, "befs_btree_read() failed to allocate %u "
440 "bytes of memory", sizeof (befs_btree_node));
444 node_off = bt_super.root_node_ptr;
445 this_node->bh = NULL;
447 /* seeks down to first leafnode, reads it into this_node */
448 res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off);
449 if (res == BEFS_BT_EMPTY) {
450 brelse(this_node->bh);
454 befs_debug(sb, "<--- befs_btree_read() Tree is EMPTY");
455 return BEFS_BT_EMPTY;
456 } else if (res == BEFS_ERR) {
460 /* find the leaf node containing the key_no key */
462 while (key_sum + this_node->head.all_key_count <= key_no) {
464 /* no more nodes to look in: key_no is too large */
465 if (this_node->head.right == befs_bt_inval) {
469 "<--- befs_btree_read() END of keys at %Lu",
470 key_sum + this_node->head.all_key_count);
471 brelse(this_node->bh);
476 key_sum += this_node->head.all_key_count;
477 node_off = this_node->head.right;
479 if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
480 befs_error(sb, "befs_btree_read() failed to read "
481 "node at %Lu", node_off);
486 /* how many keys into this_node is key_no */
487 cur_key = key_no - key_sum;
489 /* get pointers to datastructures within the node body */
490 valarray = befs_bt_valarray(this_node);
492 keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen);
494 befs_debug(sb, "Read [%Lu,%d]: keysize %d", node_off, cur_key, keylen);
496 if (bufsize < keylen + 1) {
497 befs_error(sb, "befs_btree_read() keybuf too small (%u) "
498 "for key of size %d", bufsize, keylen);
499 brelse(this_node->bh);
503 strncpy(keybuf, keystart, keylen);
504 *value = fs64_to_cpu(sb, valarray[cur_key]);
506 keybuf[keylen] = '\0';
508 befs_debug(sb, "Read [%Lu,%d]: Key \"%.*s\", Value %Lu", node_off,
509 cur_key, keylen, keybuf, *value);
511 brelse(this_node->bh);
514 befs_debug(sb, "<--- befs_btree_read()");
524 befs_debug(sb, "<--- befs_btree_read() ERROR");
529 * befs_btree_seekleaf - Find the first leafnode in the btree
530 * @sb: Filesystem superblock
531 * @ds: Datastream containing btree
532 * @bt_super: Pointer to the uperblock of the btree
533 * @this_node: Buffer to return the leafnode in
534 * @node_off: Pointer to offset of current node within datastream. Modified
538 * Helper function for btree traverse. Moves the current position to the
539 * start of the first leaf node.
541 * Also checks for an empty tree. If there are no keys, returns BEFS_BT_EMPTY.
544 befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
545 befs_btree_super * bt_super, befs_btree_node * this_node,
546 befs_off_t * node_off)
549 befs_debug(sb, "---> befs_btree_seekleaf()");
551 if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
552 befs_error(sb, "befs_btree_seekleaf() failed to read "
553 "node at %Lu", *node_off);
556 befs_debug(sb, "Seekleaf to root node %Lu", *node_off);
558 if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) {
559 befs_debug(sb, "<--- befs_btree_seekleaf() Tree is EMPTY");
560 return BEFS_BT_EMPTY;
563 while (!befs_leafnode(this_node)) {
565 if (this_node->head.all_key_count == 0) {
566 befs_debug(sb, "befs_btree_seekleaf() encountered "
567 "an empty interior node: %Lu. Using Overflow "
568 "node: %Lu", *node_off,
569 this_node->head.overflow);
570 *node_off = this_node->head.overflow;
572 befs_off_t *valarray = befs_bt_valarray(this_node);
573 *node_off = fs64_to_cpu(sb, valarray[0]);
575 if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
576 befs_error(sb, "befs_btree_seekleaf() failed to read "
577 "node at %Lu", *node_off);
581 befs_debug(sb, "Seekleaf to child node %Lu", *node_off);
583 befs_debug(sb, "Node %Lu is a leaf node", *node_off);
588 befs_debug(sb, "<--- befs_btree_seekleaf() ERROR");
593 * befs_leafnode - Determine if the btree node is a leaf node or an
595 * @node: Pointer to node structure to test
597 * Return 1 if leaf, 0 if interior
600 befs_leafnode(befs_btree_node * node)
602 /* all interior nodes (and only interior nodes) have an overflow node */
603 if (node->head.overflow == befs_bt_inval)
610 * befs_bt_keylen_index - Finds start of keylen index in a node
611 * @node: Pointer to the node structure to find the keylen index within
613 * Returns a pointer to the start of the key length index array
614 * of the B+tree node *@node
616 * "The length of all the keys in the node is added to the size of the
617 * header and then rounded up to a multiple of four to get the begining
618 * of the key length index" (p.88, practical filesystem design).
620 * Exept that rounding up to 8 works, and rounding up to 4 doesn't.
623 befs_bt_keylen_index(befs_btree_node * node)
625 const int keylen_align = 8;
626 unsigned long int off =
627 (sizeof (befs_btree_nodehead) + node->head.all_key_length);
628 ulong tmp = off % keylen_align;
631 off += keylen_align - tmp;
633 return (u16 *) ((void *) node->od_node + off);
637 * befs_bt_valarray - Finds the start of value array in a node
638 * @node: Pointer to the node structure to find the value array within
640 * Returns a pointer to the start of the value array
641 * of the node pointed to by the node header
644 befs_bt_valarray(befs_btree_node * node)
646 void *keylen_index_start = (void *) befs_bt_keylen_index(node);
647 size_t keylen_index_size = node->head.all_key_count * sizeof (u16);
649 return (befs_off_t *) (keylen_index_start + keylen_index_size);
653 * befs_bt_keydata - Finds start of keydata array in a node
654 * @node: Pointer to the node structure to find the keydata array within
656 * Returns a pointer to the start of the keydata array
657 * of the node pointed to by the node header
660 befs_bt_keydata(befs_btree_node * node)
662 return (char *) ((void *) node->od_node + sizeof (befs_btree_nodehead));
666 * befs_bt_get_key - returns a pointer to the start of a key
667 * @sb: filesystem superblock
668 * @node: node in which to look for the key
669 * @index: the index of the key to get
670 * @keylen: modified to be the length of the key at @index
672 * Returns a valid pointer into @node on success.
673 * Returns NULL on failure (bad input) and sets *@keylen = 0
676 befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
677 int index, u16 * keylen)
683 if (index < 0 || index > node->head.all_key_count) {
688 keystart = befs_bt_keydata(node);
689 keylen_index = befs_bt_keylen_index(node);
694 prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]);
696 *keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end;
698 return keystart + prev_key_end;
702 * befs_compare_strings - compare two strings
703 * @key1: pointer to the first key to be compared
704 * @keylen1: length in bytes of key1
705 * @key2: pointer to the second key to be compared
706 * @kelen2: lenght in bytes of key2
708 * Returns 0 if @key1 and @key2 are equal.
709 * Returns >0 if @key1 is greater.
710 * Returns <0 if @key2 is greater..
713 befs_compare_strings(const void *key1, int keylen1,
714 const void *key2, int keylen2)
716 int len = min_t(int, keylen1, keylen2);
717 int result = strncmp(key1, key2, len);
719 result = keylen1 - keylen2;
723 /* These will be used for non-string keyed btrees */
726 btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
728 return *(int32_t *) key1 - *(int32_t *) key2;
732 btree_compare_uint32(cont void *key1, int keylen1,
733 const void *key2, int keylen2)
735 if (*(u_int32_t *) key1 == *(u_int32_t *) key2)
737 else if (*(u_int32_t *) key1 > *(u_int32_t *) key2)
743 btree_compare_int64(cont void *key1, int keylen1, const void *key2, int keylen2)
745 if (*(int64_t *) key1 == *(int64_t *) key2)
747 else if (*(int64_t *) key1 > *(int64_t *) key2)
754 btree_compare_uint64(cont void *key1, int keylen1,
755 const void *key2, int keylen2)
757 if (*(u_int64_t *) key1 == *(u_int64_t *) key2)
759 else if (*(u_int64_t *) key1 > *(u_int64_t *) key2)
766 btree_compare_float(cont void *key1, int keylen1, const void *key2, int keylen2)
768 float result = *(float *) key1 - *(float *) key2;
772 return (result < 0.0f) ? -1 : 1;
776 btree_compare_double(cont void *key1, int keylen1,
777 const void *key2, int keylen2)
779 double result = *(double *) key1 - *(double *) key2;
783 return (result < 0.0) ? -1 : 1;