/* * linux/fs/befs/btree.c * * Copyright (C) 2001-2002 Will Dyson <will_dyson@pobox.com> * * Licensed under the GNU GPL. See the file COPYING for details. * * 2002-02-05: Sergey S. Kostyliov added binary search withing * btree nodes. * * Many thanks to: * * Dominic Giampaolo, author of "Practical File System * Design with the Be File System", for such a helpful book. * * Marcus J. Ranum, author of the b+tree package in * comp.sources.misc volume 10. This code is not copied from that * work, but it is partially based on it. * * Makoto Kato, author of the original BeFS for linux filesystem * driver. */ #include <linux/kernel.h> #include <linux/string.h> #include <linux/slab.h> #include <linux/mm.h> #include <linux/buffer_head.h> #include "befs.h" #include "btree.h" #include "datastream.h" /* * The btree functions in this file are built on top of the * datastream.c interface, which is in turn built on top of the * io.c interface. */ /* Befs B+tree structure: * * The first thing in the tree is the tree superblock. It tells you * all kinds of useful things about the tree, like where the rootnode * is located, and the size of the nodes (always 1024 with current version * of BeOS). * * The rest of the tree consists of a series of nodes. Nodes contain a header * (struct befs_btree_nodehead), the packed key data, an array of shorts * containing the ending offsets for each of the keys, and an array of * befs_off_t values. In interior nodes, the keys are the ending keys for * the childnode they point to, and the values are offsets into the * datastream containing the tree. */ /* Note: * * The book states 2 confusing things about befs b+trees. First, * it states that the overflow field of node headers is used by internal nodes * to point to another node that "effectively continues this one". Here is what * I believe that means. Each key in internal nodes points to another node that * contains key values less than itself. Inspection reveals that the last key * in the internal node is not the last key in the index. Keys that are * greater than the last key in the internal node go into the overflow node. * I imagine there is a performance reason for this. * * Second, it states that the header of a btree node is sufficient to * distinguish internal nodes from leaf nodes. Without saying exactly how. * After figuring out the first, it becomes obvious that internal nodes have * overflow nodes and leafnodes do not. */ /* * Currently, this code is only good for directory B+trees. * In order to be used for other BFS indexes, it needs to be extended to handle * duplicate keys and non-string keytypes (int32, int64, float, double). */ /* * In memory structure of each btree node */ typedef struct { befs_host_btree_nodehead head; /* head of node converted to cpu byteorder */ struct buffer_head *bh; befs_btree_nodehead *od_node; /* on disk node */ } befs_btree_node; /* local constants */ static const befs_off_t befs_bt_inval = 0xffffffffffffffffULL; /* local functions */ static int befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds, befs_btree_super * bt_super, befs_btree_node * this_node, befs_off_t * node_off); static int befs_bt_read_super(struct super_block *sb, befs_data_stream * ds, befs_btree_super * sup); static int befs_bt_read_node(struct super_block *sb, befs_data_stream * ds, befs_btree_node * node, befs_off_t node_off); static int befs_leafnode(befs_btree_node * node); static fs16 *befs_bt_keylen_index(befs_btree_node * node); static fs64 *befs_bt_valarray(befs_btree_node * node); static char *befs_bt_keydata(befs_btree_node * node); static int befs_find_key(struct super_block *sb, befs_btree_node * node, const char *findkey, befs_off_t * value); static char *befs_bt_get_key(struct super_block *sb, befs_btree_node * node, int index, u16 * keylen); static int befs_compare_strings(const void *key1, int keylen1, const void *key2, int keylen2); /** * befs_bt_read_super - read in btree superblock convert to cpu byteorder * @sb: Filesystem superblock * @ds: Datastream to read from * @sup: Buffer in which to place the btree superblock * * Calls befs_read_datastream to read in the btree superblock and * makes sure it is in cpu byteorder, byteswapping if necessary. * * On success, returns BEFS_OK and *@sup contains the btree superblock, * in cpu byte order. * * On failure, BEFS_ERR is returned. */ static int befs_bt_read_super(struct super_block *sb, befs_data_stream * ds, befs_btree_super * sup) { struct buffer_head *bh = NULL; befs_disk_btree_super *od_sup = NULL; befs_debug(sb, "---> befs_btree_read_super()"); bh = befs_read_datastream(sb, ds, 0, NULL); if (!bh) { befs_error(sb, "Couldn't read index header."); goto error; } od_sup = (befs_disk_btree_super *) bh->b_data; befs_dump_index_entry(sb, od_sup); sup->magic = fs32_to_cpu(sb, od_sup->magic); sup->node_size = fs32_to_cpu(sb, od_sup->node_size); sup->max_depth = fs32_to_cpu(sb, od_sup->max_depth); sup->data_type = fs32_to_cpu(sb, od_sup->data_type); sup->root_node_ptr = fs64_to_cpu(sb, od_sup->root_node_ptr); sup->free_node_ptr = fs64_to_cpu(sb, od_sup->free_node_ptr); sup->max_size = fs64_to_cpu(sb, od_sup->max_size); brelse(bh); if (sup->magic != BEFS_BTREE_MAGIC) { befs_error(sb, "Index header has bad magic."); goto error; } befs_debug(sb, "<--- befs_btree_read_super()"); return BEFS_OK; error: befs_debug(sb, "<--- befs_btree_read_super() ERROR"); return BEFS_ERR; } /** * befs_bt_read_node - read in btree node and convert to cpu byteorder * @sb: Filesystem superblock * @ds: Datastream to read from * @node: Buffer in which to place the btree node * @node_off: Starting offset (in bytes) of the node in @ds * * Calls befs_read_datastream to read in the indicated btree node and * makes sure its header fields are in cpu byteorder, byteswapping if * necessary. * Note: node->bh must be NULL when this function called first * time. Don't forget brelse(node->bh) after last call. * * On success, returns BEFS_OK and *@node contains the btree node that * starts at @node_off, with the node->head fields in cpu byte order. * * On failure, BEFS_ERR is returned. */ static int befs_bt_read_node(struct super_block *sb, befs_data_stream * ds, befs_btree_node * node, befs_off_t node_off) { uint off = 0; befs_debug(sb, "---> befs_bt_read_node()"); if (node->bh) brelse(node->bh); node->bh = befs_read_datastream(sb, ds, node_off, &off); if (!node->bh) { befs_error(sb, "befs_bt_read_node() failed to read " "node at %Lu", node_off); befs_debug(sb, "<--- befs_bt_read_node() ERROR"); return BEFS_ERR; } node->od_node = (befs_btree_nodehead *) ((void *) node->bh->b_data + off); befs_dump_index_node(sb, node->od_node); node->head.left = fs64_to_cpu(sb, node->od_node->left); node->head.right = fs64_to_cpu(sb, node->od_node->right); node->head.overflow = fs64_to_cpu(sb, node->od_node->overflow); node->head.all_key_count = fs16_to_cpu(sb, node->od_node->all_key_count); node->head.all_key_length = fs16_to_cpu(sb, node->od_node->all_key_length); befs_debug(sb, "<--- befs_btree_read_node()"); return BEFS_OK; } /** * befs_btree_find - Find a key in a befs B+tree * @sb: Filesystem superblock * @ds: Datastream containing btree * @key: Key string to lookup in btree * @value: Value stored with @key * * On success, returns BEFS_OK and sets *@value to the value stored * with @key (usually the disk block number of an inode). * * On failure, returns BEFS_ERR or BEFS_BT_NOT_FOUND. * * Algorithm: * Read the superblock and rootnode of the b+tree. * Drill down through the interior nodes using befs_find_key(). * Once at the correct leaf node, use befs_find_key() again to get the * actuall value stored with the key. */ int befs_btree_find(struct super_block *sb, befs_data_stream * ds, const char *key, befs_off_t * value) { befs_btree_node *this_node = NULL; befs_btree_super bt_super; befs_off_t node_off; int res; befs_debug(sb, "---> befs_btree_find() Key: %s", key); if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) { befs_error(sb, "befs_btree_find() failed to read index superblock"); goto error; } this_node = kmalloc(sizeof (befs_btree_node), GFP_NOFS); if (!this_node) { befs_error(sb, "befs_btree_find() failed to allocate %u " "bytes of memory", sizeof (befs_btree_node)); goto error; } this_node->bh = NULL; /* read in root node */ node_off = bt_super.root_node_ptr; if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) { befs_error(sb, "befs_btree_find() failed to read " "node at %Lu", node_off); goto error_alloc; } while (!befs_leafnode(this_node)) { res = befs_find_key(sb, this_node, key, &node_off); if (res == BEFS_BT_NOT_FOUND) node_off = this_node->head.overflow; /* if no match, go to overflow node */ if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) { befs_error(sb, "befs_btree_find() failed to read " "node at %Lu", node_off); goto error_alloc; } } /* at the correct leaf node now */ res = befs_find_key(sb, this_node, key, value); brelse(this_node->bh); kfree(this_node); if (res != BEFS_BT_MATCH) { befs_debug(sb, "<--- befs_btree_find() Key %s not found", key); *value = 0; return BEFS_BT_NOT_FOUND; } befs_debug(sb, "<--- befs_btree_find() Found key %s, value %Lu", key, *value); return BEFS_OK; error_alloc: kfree(this_node); error: *value = 0; befs_debug(sb, "<--- befs_btree_find() ERROR"); return BEFS_ERR; } /** * befs_find_key - Search for a key within a node * @sb: Filesystem superblock * @node: Node to find the key within * @key: Keystring to search for * @value: If key is found, the value stored with the key is put here * * finds exact match if one exists, and returns BEFS_BT_MATCH * If no exact match, finds first key in node that is greater * (alphabetically) than the search key and returns BEFS_BT_PARMATCH * (for partial match, I guess). Can you think of something better to * call it? * * If no key was a match or greater than the search key, return * BEFS_BT_NOT_FOUND. * * Use binary search instead of a linear. */ static int befs_find_key(struct super_block *sb, befs_btree_node * node, const char *findkey, befs_off_t * value) { int first, last, mid; int eq; u16 keylen; int findkey_len; char *thiskey; fs64 *valarray; befs_debug(sb, "---> befs_find_key() %s", findkey); *value = 0; findkey_len = strlen(findkey); /* if node can not contain key, just skeep this node */ last = node->head.all_key_count - 1; thiskey = befs_bt_get_key(sb, node, last, &keylen); eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len); if (eq < 0) { befs_debug(sb, "<--- befs_find_key() %s not found", findkey); return BEFS_BT_NOT_FOUND; } valarray = befs_bt_valarray(node); /* simple binary search */ first = 0; mid = 0; while (last >= first) { mid = (last + first) / 2; befs_debug(sb, "first: %d, last: %d, mid: %d", first, last, mid); thiskey = befs_bt_get_key(sb, node, mid, &keylen); eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len); if (eq == 0) { befs_debug(sb, "<--- befs_find_key() found %s at %d", thiskey, mid); *value = fs64_to_cpu(sb, valarray[mid]); return BEFS_BT_MATCH; } if (eq > 0) last = mid - 1; else first = mid + 1; } if (eq < 0) *value = fs64_to_cpu(sb, valarray[mid + 1]); else *value = fs64_to_cpu(sb, valarray[mid]); befs_debug(sb, "<--- befs_find_key() found %s at %d", thiskey, mid); return BEFS_BT_PARMATCH; } /** * befs_btree_read - Traverse leafnodes of a btree * @sb: Filesystem superblock * @ds: Datastream containing btree * @key_no: Key number (alphabetical order) of key to read * @bufsize: Size of the buffer to return key in * @keybuf: Pointer to a buffer to put the key in * @keysize: Length of the returned key * @value: Value stored with the returned key * * Heres how it works: Key_no is the index of the key/value pair to * return in keybuf/value. * Bufsize is the size of keybuf (BEFS_NAME_LEN+1 is a good size). Keysize is * the number of charecters in the key (just a convenience). * * Algorithm: * Get the first leafnode of the tree. See if the requested key is in that * node. If not, follow the node->right link to the next leafnode. Repeat * until the (key_no)th key is found or the tree is out of keys. */ int befs_btree_read(struct super_block *sb, befs_data_stream * ds, loff_t key_no, size_t bufsize, char *keybuf, size_t * keysize, befs_off_t * value) { befs_btree_node *this_node; befs_btree_super bt_super; befs_off_t node_off = 0; int cur_key; fs64 *valarray; char *keystart; u16 keylen; int res; uint key_sum = 0; befs_debug(sb, "---> befs_btree_read()"); if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) { befs_error(sb, "befs_btree_read() failed to read index superblock"); goto error; } if ((this_node = (befs_btree_node *) kmalloc(sizeof (befs_btree_node), GFP_NOFS)) == NULL) { befs_error(sb, "befs_btree_read() failed to allocate %u " "bytes of memory", sizeof (befs_btree_node)); goto error; } node_off = bt_super.root_node_ptr; this_node->bh = NULL; /* seeks down to first leafnode, reads it into this_node */ res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off); if (res == BEFS_BT_EMPTY) { brelse(this_node->bh); kfree(this_node); *value = 0; *keysize = 0; befs_debug(sb, "<--- befs_btree_read() Tree is EMPTY"); return BEFS_BT_EMPTY; } else if (res == BEFS_ERR) { goto error_alloc; } /* find the leaf node containing the key_no key */ while (key_sum + this_node->head.all_key_count <= key_no) { /* no more nodes to look in: key_no is too large */ if (this_node->head.right == befs_bt_inval) { *keysize = 0; *value = 0; befs_debug(sb, "<--- befs_btree_read() END of keys at %Lu", key_sum + this_node->head.all_key_count); brelse(this_node->bh); kfree(this_node); return BEFS_BT_END; } key_sum += this_node->head.all_key_count; node_off = this_node->head.right; if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) { befs_error(sb, "befs_btree_read() failed to read " "node at %Lu", node_off); goto error_alloc; } } /* how many keys into this_node is key_no */ cur_key = key_no - key_sum; /* get pointers to datastructures within the node body */ valarray = befs_bt_valarray(this_node); keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen); befs_debug(sb, "Read [%Lu,%d]: keysize %d", node_off, cur_key, keylen); if (bufsize < keylen + 1) { befs_error(sb, "befs_btree_read() keybuf too small (%u) " "for key of size %d", bufsize, keylen); brelse(this_node->bh); goto error_alloc; }; strncpy(keybuf, keystart, keylen); *value = fs64_to_cpu(sb, valarray[cur_key]); *keysize = keylen; keybuf[keylen] = '\0'; befs_debug(sb, "Read [%Lu,%d]: Key \"%.*s\", Value %Lu", node_off, cur_key, keylen, keybuf, *value); brelse(this_node->bh); kfree(this_node); befs_debug(sb, "<--- befs_btree_read()"); return BEFS_OK; error_alloc: kfree(this_node); error: *keysize = 0; *value = 0; befs_debug(sb, "<--- befs_btree_read() ERROR"); return BEFS_ERR; } /** * befs_btree_seekleaf - Find the first leafnode in the btree * @sb: Filesystem superblock * @ds: Datastream containing btree * @bt_super: Pointer to the superblock of the btree * @this_node: Buffer to return the leafnode in * @node_off: Pointer to offset of current node within datastream. Modified * by the function. * * * Helper function for btree traverse. Moves the current position to the * start of the first leaf node. * * Also checks for an empty tree. If there are no keys, returns BEFS_BT_EMPTY. */ static int befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds, befs_btree_super * bt_super, befs_btree_node * this_node, befs_off_t * node_off) { befs_debug(sb, "---> befs_btree_seekleaf()"); if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) { befs_error(sb, "befs_btree_seekleaf() failed to read " "node at %Lu", *node_off); goto error; } befs_debug(sb, "Seekleaf to root node %Lu", *node_off); if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) { befs_debug(sb, "<--- befs_btree_seekleaf() Tree is EMPTY"); return BEFS_BT_EMPTY; } while (!befs_leafnode(this_node)) { if (this_node->head.all_key_count == 0) { befs_debug(sb, "befs_btree_seekleaf() encountered " "an empty interior node: %Lu. Using Overflow " "node: %Lu", *node_off, this_node->head.overflow); *node_off = this_node->head.overflow; } else { fs64 *valarray = befs_bt_valarray(this_node); *node_off = fs64_to_cpu(sb, valarray[0]); } if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) { befs_error(sb, "befs_btree_seekleaf() failed to read " "node at %Lu", *node_off); goto error; } befs_debug(sb, "Seekleaf to child node %Lu", *node_off); } befs_debug(sb, "Node %Lu is a leaf node", *node_off); return BEFS_OK; error: befs_debug(sb, "<--- befs_btree_seekleaf() ERROR"); return BEFS_ERR; } /** * befs_leafnode - Determine if the btree node is a leaf node or an * interior node * @node: Pointer to node structure to test * * Return 1 if leaf, 0 if interior */ static int befs_leafnode(befs_btree_node * node) { /* all interior nodes (and only interior nodes) have an overflow node */ if (node->head.overflow == befs_bt_inval) return 1; else return 0; } /** * befs_bt_keylen_index - Finds start of keylen index in a node * @node: Pointer to the node structure to find the keylen index within * * Returns a pointer to the start of the key length index array * of the B+tree node *@node * * "The length of all the keys in the node is added to the size of the * header and then rounded up to a multiple of four to get the beginning * of the key length index" (p.88, practical filesystem design). * * Except that rounding up to 8 works, and rounding up to 4 doesn't. */ static fs16 * befs_bt_keylen_index(befs_btree_node * node) { const int keylen_align = 8; unsigned long int off = (sizeof (befs_btree_nodehead) + node->head.all_key_length); ulong tmp = off % keylen_align; if (tmp) off += keylen_align - tmp; return (fs16 *) ((void *) node->od_node + off); } /** * befs_bt_valarray - Finds the start of value array in a node * @node: Pointer to the node structure to find the value array within * * Returns a pointer to the start of the value array * of the node pointed to by the node header */ static fs64 * befs_bt_valarray(befs_btree_node * node) { void *keylen_index_start = (void *) befs_bt_keylen_index(node); size_t keylen_index_size = node->head.all_key_count * sizeof (fs16); return (fs64 *) (keylen_index_start + keylen_index_size); } /** * befs_bt_keydata - Finds start of keydata array in a node * @node: Pointer to the node structure to find the keydata array within * * Returns a pointer to the start of the keydata array * of the node pointed to by the node header */ static char * befs_bt_keydata(befs_btree_node * node) { return (char *) ((void *) node->od_node + sizeof (befs_btree_nodehead)); } /** * befs_bt_get_key - returns a pointer to the start of a key * @sb: filesystem superblock * @node: node in which to look for the key * @index: the index of the key to get * @keylen: modified to be the length of the key at @index * * Returns a valid pointer into @node on success. * Returns NULL on failure (bad input) and sets *@keylen = 0 */ static char * befs_bt_get_key(struct super_block *sb, befs_btree_node * node, int index, u16 * keylen) { int prev_key_end; char *keystart; fs16 *keylen_index; if (index < 0 || index > node->head.all_key_count) { *keylen = 0; return NULL; } keystart = befs_bt_keydata(node); keylen_index = befs_bt_keylen_index(node); if (index == 0) prev_key_end = 0; else prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]); *keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end; return keystart + prev_key_end; } /** * befs_compare_strings - compare two strings * @key1: pointer to the first key to be compared * @keylen1: length in bytes of key1 * @key2: pointer to the second key to be compared * @kelen2: length in bytes of key2 * * Returns 0 if @key1 and @key2 are equal. * Returns >0 if @key1 is greater. * Returns <0 if @key2 is greater.. */ static int befs_compare_strings(const void *key1, int keylen1, const void *key2, int keylen2) { int len = min_t(int, keylen1, keylen2); int result = strncmp(key1, key2, len); if (result == 0) result = keylen1 - keylen2; return result; } /* These will be used for non-string keyed btrees */ #if 0 static int btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2) { return *(int32_t *) key1 - *(int32_t *) key2; } static int btree_compare_uint32(cont void *key1, int keylen1, const void *key2, int keylen2) { if (*(u_int32_t *) key1 == *(u_int32_t *) key2) return 0; else if (*(u_int32_t *) key1 > *(u_int32_t *) key2) return 1; return -1; } static int btree_compare_int64(cont void *key1, int keylen1, const void *key2, int keylen2) { if (*(int64_t *) key1 == *(int64_t *) key2) return 0; else if (*(int64_t *) key1 > *(int64_t *) key2) return 1; return -1; } static int btree_compare_uint64(cont void *key1, int keylen1, const void *key2, int keylen2) { if (*(u_int64_t *) key1 == *(u_int64_t *) key2) return 0; else if (*(u_int64_t *) key1 > *(u_int64_t *) key2) return 1; return -1; } static int btree_compare_float(cont void *key1, int keylen1, const void *key2, int keylen2) { float result = *(float *) key1 - *(float *) key2; if (result == 0.0f) return 0; return (result < 0.0f) ? -1 : 1; } static int btree_compare_double(cont void *key1, int keylen1, const void *key2, int keylen2) { double result = *(double *) key1 - *(double *) key2; if (result == 0.0) return 0; return (result < 0.0) ? -1 : 1; } #endif //0