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1275 |
phoenix |
/*
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* linux/fs/hfs/bfind.c
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*
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* Copyright (C) 1995, 1996 Paul H. Hargrove
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* This file may be distributed under the terms of the GNU General Public License.
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*
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* This file contains the code to access records in a btree.
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*
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* "XXX" in a comment is a note to myself to consider changing something.
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*
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* In function preconditions the term "valid" applied to a pointer to
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* a structure means that the pointer is non-NULL and the structure it
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* points to has all fields initialized to consistent values.
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*/
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#include "hfs_btree.h"
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/*================ Global functions ================*/
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/*
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* hfs_brec_relse()
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*
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* Description:
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* This function releases some of the nodes associated with a brec.
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* Input Variable(s):
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* struct hfs_brec *brec: pointer to the brec to release some nodes from.
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* struct hfs_belem *elem: the last node to release or NULL for all
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* Output Variable(s):
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* NONE
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* Returns:
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* void
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* Preconditions:
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* 'brec' points to a "valid" (struct hfs_brec)
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* Postconditions:
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* All nodes between the indicated node and the beginning of the path
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* are released.
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*/
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void hfs_brec_relse(struct hfs_brec *brec, struct hfs_belem *elem)
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{
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if (!elem) {
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elem = brec->bottom;
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}
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while (brec->top <= elem) {
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hfs_bnode_relse(&brec->top->bnr);
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++brec->top;
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}
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}
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/*
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* hfs_bfind()
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*
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* Description:
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* This function has sole responsibility for locating existing
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* records in a B-tree. Given a B-tree and a key it locates the
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* "greatest" record "less than or equal to" the given key. The
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* exact behavior is determined by the bits of the flags variable as
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* follows:
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* ('flags' & HFS_LOCK_MASK):
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* The lock_type argument to be used when calling hfs_bnode_find().
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* HFS_BFIND_EXACT: only accept an exact match, otherwise take the
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* "largest" record less than 'target' as a "match"
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* HFS_BFIND_LOCK: request HFS_LOCK_WRITE access to the node containing
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* the "matching" record when it is located
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* HFS_BPATH_FIRST: keep access to internal nodes when accessing their
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* first child.
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* HFS_BPATH_OVERFLOW: keep access to internal nodes when the accessed
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* child is too full to insert another pointer record.
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* HFS_BPATH_UNDERFLOW: keep access to internal nodes when the accessed
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* child is would be less than half full upon removing a pointer record.
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* Input Variable(s):
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* struct hfs_brec *brec: pointer to the (struct hfs_brec) to hold
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* the search results.
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* struct hfs_bkey *target: pointer to the (struct hfs_bkey)
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* to search for
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* int flags: bitwise OR of flags which determine the function's behavior
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* Output Variable(s):
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* 'brec' contains the results of the search on success or is invalid
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* on failure.
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* Returns:
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* int: 0 or 1 on success or an error code on failure:
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* -EINVAL: one of the input variables was NULL.
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* -ENOENT: tree is valid but empty or no "matching" record was located.
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* If the HFS_BFIND_EXACT bit of 'flags' is not set then the case of no
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* matching record will give a 'brec' with a 'record' field of zero
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* rather than returning this error.
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* -EIO: an I/O operation or an assertion about the structure of a
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* valid B-tree failed indicating corruption of either the B-tree
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* structure on the disk or one of the in-core structures representing
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* the B-tree.
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* (This could also be returned if a kmalloc() call failed in a
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* subordinate routine that is intended to get the data from the
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* disk or the buffer cache.)
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* Preconditions:
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* 'brec' is NULL or points to a (struct hfs_brec) with a 'tree' field
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* which points to a valid (struct hfs_btree).
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* 'target' is NULL or points to a "valid" (struct hfs_bkey)
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* Postconditions:
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* If 'brec', 'brec->tree' or 'target' is NULL then -EINVAL is returned.
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* If 'brec', 'brec->tree' and 'target' are non-NULL but the tree
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* is empty then -ENOENT is returned.
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* If 'brec', 'brec->tree' and 'target' are non-NULL but the call to
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* hfs_brec_init() fails then '*brec' is NULL and -EIO is returned.
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* If 'brec', 'brec->tree' and 'target' are non-NULL and the tree is
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* non-empty then the tree is searched as follows:
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* If any call to hfs_brec_next() fails or returns a node that is
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* neither an index node nor a leaf node then -EIO is returned to
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* indicate that the B-tree or buffer-cache are corrupted.
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* If every record in the tree is "greater than" the given key
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* and the HFS_BFIND_EXACT bit of 'flags' is set then -ENOENT is returned.
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* If every record in the tree is "greater than" the given key
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* and the HFS_BFIND_EXACT bit of 'flags' is clear then 'brec' refers
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* to the first leaf node in the tree and has a 'record' field of
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* zero, and 1 is returned.
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* If a "matching" record is located with key "equal to" 'target'
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* then the return value is 0 and 'brec' indicates the record.
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* If a "matching" record is located with key "greater than" 'target'
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* then the behavior is determined as follows:
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* If the HFS_BFIND_EXACT bit of 'flags' is not set then 1 is returned
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* and 'brec' refers to the "matching" record.
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* If the HFS_BFIND_EXACT bit of 'flags' is set then -ENOENT is returned.
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* If the return value is non-negative and the HFS_BFIND_LOCK bit of
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* 'flags' is set then hfs_brec_lock() is called on the bottom element
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* of 'brec' before returning.
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*/
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int hfs_bfind(struct hfs_brec *brec, struct hfs_btree *tree,
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const struct hfs_bkey *target, int flags)
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{
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struct hfs_belem *curr;
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struct hfs_bkey *key;
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struct hfs_bnode *bn;
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int result, ntype;
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/* check for invalid arguments */
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if (!brec || (tree->magic != HFS_BTREE_MAGIC) || !target) {
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return -EINVAL;
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}
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/* check for empty tree */
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if (!tree->root || !tree->bthNRecs) {
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return -ENOENT;
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}
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/* start search at root of tree */
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if (!(curr = hfs_brec_init(brec, tree, flags))) {
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return -EIO;
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}
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/* traverse the tree */
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do {
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bn = curr->bnr.bn;
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if (!curr->record) {
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hfs_warn("hfs_bfind: empty bnode\n");
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hfs_brec_relse(brec, NULL);
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return -EIO;
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}
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/* reverse linear search yielding largest key "less
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than or equal to" 'target'.
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It is questionable whether a binary search would be
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significantly faster */
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do {
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key = belem_key(curr);
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if (!key->KeyLen) {
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hfs_warn("hfs_bfind: empty key\n");
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hfs_brec_relse(brec, NULL);
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return -EIO;
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}
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result = (tree->compare)(target, key);
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} while ((result<0) && (--curr->record));
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ntype = bn->ndType;
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/* see if all keys > target */
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if (!curr->record) {
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if (bn->ndBLink) {
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/* at a node other than the left-most at a
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given level it means the parent had an
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incorrect key for this child */
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hfs_brec_relse(brec, NULL);
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hfs_warn("hfs_bfind: corrupted b-tree %d.\n",
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(int)ntohl(tree->entry.cnid));
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return -EIO;
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}
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if (flags & HFS_BFIND_EXACT) {
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/* we're not going to find it */
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hfs_brec_relse(brec, NULL);
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return -ENOENT;
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}
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if (ntype == ndIndxNode) {
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/* since we are at the left-most node at
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the current level and looking for the
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predecessor of 'target' keep going down */
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curr->record = 1;
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} else {
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/* we're at first leaf so fall through */
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}
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| 199 |
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}
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| 200 |
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| 201 |
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/* get next node if necessary */
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| 202 |
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if ((ntype == ndIndxNode) && !(curr = hfs_brec_next(brec))) {
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| 203 |
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return -EIO;
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}
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} while (ntype == ndIndxNode);
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| 207 |
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if (key->KeyLen > tree->bthKeyLen) {
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hfs_warn("hfs_bfind: oversized key\n");
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hfs_brec_relse(brec, NULL);
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return -EIO;
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| 211 |
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}
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| 213 |
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if (ntype != ndLeafNode) {
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hfs_warn("hfs_bfind: invalid node type %02x in node %d of "
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"btree %d\n", bn->ndType, bn->node,
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(int)ntohl(tree->entry.cnid));
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| 217 |
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hfs_brec_relse(brec, NULL);
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return -EIO;
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| 219 |
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}
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| 220 |
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| 221 |
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if ((flags & HFS_BFIND_EXACT) && result) {
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| 222 |
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hfs_brec_relse(brec, NULL);
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| 223 |
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return -ENOENT;
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| 224 |
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}
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| 225 |
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| 226 |
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if (!(flags & HFS_BPATH_MASK)) {
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| 227 |
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hfs_brec_relse(brec, brec->bottom-1);
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| 228 |
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}
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| 229 |
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| 230 |
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if (flags & HFS_BFIND_LOCK) {
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| 231 |
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hfs_brec_lock(brec, brec->bottom);
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| 232 |
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}
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| 233 |
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| 234 |
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brec->key = brec_key(brec);
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| 235 |
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brec->data = bkey_record(brec->key);
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| 236 |
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| 237 |
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return result ? 1 : 0;
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| 238 |
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}
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| 239 |
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| 240 |
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/*
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| 241 |
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* hfs_bsucc()
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| 242 |
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*
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| 243 |
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* Description:
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| 244 |
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* This function overwrites '*brec' with its successor in the B-tree,
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| 245 |
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* obtaining the same type of access.
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| 246 |
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* Input Variable(s):
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| 247 |
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* struct hfs_brec *brec: address of the (struct hfs_brec) to overwrite
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| 248 |
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* with its successor
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| 249 |
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* Output Variable(s):
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| 250 |
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* struct hfs_brec *brec: address of the successor of the original
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| 251 |
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* '*brec' or to invalid data
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| 252 |
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* Returns:
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| 253 |
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* int: 0 on success, or one of -EINVAL, -EIO, or -EINVAL on failure
|
| 254 |
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* Preconditions:
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| 255 |
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* 'brec' pointers to a "valid" (struct hfs_brec)
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| 256 |
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* Postconditions:
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| 257 |
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* If the given '*brec' is not "valid" -EINVAL is returned and
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| 258 |
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* '*brec' is unchanged.
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| 259 |
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* If the given 'brec' is "valid" but has no successor then -ENOENT
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| 260 |
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* is returned and '*brec' is invalid.
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| 261 |
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* If a call to hfs_bnode_find() is necessary to find the successor,
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| 262 |
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* but fails then -EIO is returned and '*brec' is invalid.
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| 263 |
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* If none of the three previous conditions prevents finding the
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| 264 |
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* successor of '*brec', then 0 is returned, and '*brec' is overwritten
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| 265 |
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* with the (struct hfs_brec) for its successor.
|
| 266 |
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* In the cases when '*brec' is invalid, the old records is freed.
|
| 267 |
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*/
|
| 268 |
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int hfs_bsucc(struct hfs_brec *brec, int count)
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| 269 |
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{
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| 270 |
|
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struct hfs_belem *belem;
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| 271 |
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struct hfs_bnode *bn;
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| 272 |
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| 273 |
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if (!brec || !(belem = brec->bottom) || (belem != brec->top) ||
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| 274 |
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!(bn = belem->bnr.bn) || (bn->magic != HFS_BNODE_MAGIC) ||
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| 275 |
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!bn->tree || (bn->tree->magic != HFS_BTREE_MAGIC) ||
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| 276 |
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!hfs_buffer_ok(bn->buf)) {
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| 277 |
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hfs_warn("hfs_bsucc: invalid/corrupt arguments.\n");
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| 278 |
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return -EINVAL;
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| 279 |
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}
|
| 280 |
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|
| 281 |
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while (count) {
|
| 282 |
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int left = bn->ndNRecs - belem->record;
|
| 283 |
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|
| 284 |
|
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if (left < count) {
|
| 285 |
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struct hfs_bnode_ref old;
|
| 286 |
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hfs_u32 node;
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| 287 |
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|
| 288 |
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/* Advance to next node */
|
| 289 |
|
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if (!(node = bn->ndFLink)) {
|
| 290 |
|
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hfs_brec_relse(brec, belem);
|
| 291 |
|
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return -ENOENT;
|
| 292 |
|
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}
|
| 293 |
|
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if (node == bn->node) {
|
| 294 |
|
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hfs_warn("hfs_bsucc: corrupt btree\n");
|
| 295 |
|
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hfs_brec_relse(brec, belem);
|
| 296 |
|
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return -EIO;
|
| 297 |
|
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}
|
| 298 |
|
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old = belem->bnr;
|
| 299 |
|
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belem->bnr = hfs_bnode_find(brec->tree, node,
|
| 300 |
|
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belem->bnr.lock_type);
|
| 301 |
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hfs_bnode_relse(&old);
|
| 302 |
|
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if (!(bn = belem->bnr.bn)) {
|
| 303 |
|
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return -EIO;
|
| 304 |
|
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}
|
| 305 |
|
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belem->record = 1;
|
| 306 |
|
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count -= (left + 1);
|
| 307 |
|
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} else {
|
| 308 |
|
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belem->record += count;
|
| 309 |
|
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break;
|
| 310 |
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}
|
| 311 |
|
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}
|
| 312 |
|
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brec->key = belem_key(belem);
|
| 313 |
|
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brec->data = bkey_record(brec->key);
|
| 314 |
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|
| 315 |
|
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if (brec->key->KeyLen > brec->tree->bthKeyLen) {
|
| 316 |
|
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hfs_warn("hfs_bsucc: oversized key\n");
|
| 317 |
|
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hfs_brec_relse(brec, NULL);
|
| 318 |
|
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return -EIO;
|
| 319 |
|
|
}
|
| 320 |
|
|
|
| 321 |
|
|
return 0;
|
| 322 |
|
|
}
|
