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Diffstat (limited to 'fs/befs/btree.c')
| -rw-r--r-- | fs/befs/btree.c | 787 |
1 files changed, 787 insertions, 0 deletions
diff --git a/fs/befs/btree.c b/fs/befs/btree.c new file mode 100644 index 0000000..4202db7 --- /dev/null +++ b/fs/befs/btree.c @@ -0,0 +1,787 @@ +/* + * 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 |
