Import 2.3.1pre2

[davej-history.git] / fs / hfs / binsert.c

/*
 * linux/fs/hfs/binsert.c
 *
 * Copyright (C) 1995-1997  Paul H. Hargrove
 * This file may be distributed under the terms of the GNU Public License.
 *
 * This file contains the code to insert records in a B-tree.
 *
 * "XXX" in a comment is a note to myself to consider changing something.
 *
 * In function preconditions the term "valid" applied to a pointer to
 * a structure means that the pointer is non-NULL and the structure it
 * points to has all fields initialized to consistent values.
 */

#include "hfs_btree.h"

/*================ File-local functions ================*/

/* btree locking functions */
static inline void hfs_btree_lock(struct hfs_btree *tree)
{
  while (tree->lock) 
    hfs_sleep_on(&tree->wait);
  tree->lock = 1;
}

static inline void hfs_btree_unlock(struct hfs_btree *tree)
{
  tree->lock = 0;
  hfs_wake_up(&tree->wait);
}

/*
 * binsert_nonfull()
 *
 * Description:
 *   Inserts a record in a given bnode known to have sufficient space.
 * Input Variable(s):
 *   struct hfs_brec* brec: pointer to the brec for the insertion
 *   struct hfs_belem* belem: the element in the search path to insert in
 *   struct hfs_bkey* key: pointer to the key for the record to insert
 *   void* data: pointer to the record to insert
 *   hfs_u16 keysize: size of the key to insert
 *   hfs_u16 datasize: size of the record to insert
 * Output Variable(s):
 *   NONE
 * Returns:
 *   NONE
 * Preconditions:
 *   'brec' points to a valid (struct hfs_brec).
 *   'belem' points to a valid (struct hfs_belem) in 'brec', the node
 *    of which has enough free space to insert 'key' and 'data'.
 *   'key' is a pointer to a valid (struct hfs_bkey) of length 'keysize'
 *    which, in sorted order, belongs at the location indicated by 'brec'.
 *   'data' is non-NULL an points to appropriate data of length 'datasize'
 * Postconditions:
 *   The record has been inserted in the position indicated by 'brec'.
 */
static void binsert_nonfull(struct hfs_brec *brec, struct hfs_belem *belem,
                            const struct hfs_bkey *key, const void *data,
                            hfs_u8 keysize, hfs_u16 datasize)
{
        int i, rec, nrecs, size, tomove;
        hfs_u8 *start;
        struct hfs_bnode *bnode = belem->bnr.bn;

        rec = ++(belem->record);
        size = ROUND(keysize+1) + datasize;
        nrecs = bnode->ndNRecs + 1;
        tomove = bnode_offset(bnode, nrecs) - bnode_offset(bnode, rec);
        
        /* adjust the record table */
        for (i = nrecs; i >= rec; --i) {
                hfs_put_hs(bnode_offset(bnode,i) + size, RECTBL(bnode,i+1));
        }

        /* make room */
        start = bnode_key(bnode, rec);
        memmove(start + size, start, tomove);

        /* copy in the key and the data*/
        *start = keysize;
        keysize = ROUND(keysize+1);
        memcpy(start + 1, (hfs_u8 *)key + 1, keysize-1);
        memcpy(start + keysize, data, datasize);

        /* update record count */
        ++bnode->ndNRecs;
}

/*
 * add_root()
 *
 * Description:
 *   Adds a new root to a B*-tree, increasing its height.
 * Input Variable(s):
 *   struct hfs_btree *tree: the tree to add a new root to
 *   struct hfs_bnode *left: the new root's first child or NULL
 *   struct hfs_bnode *right: the new root's second child or NULL
 * Output Variable(s):
 *   NONE
 * Returns:
 *   void
 * Preconditions:
 *   'tree' points to a valid (struct hfs_btree).
 *   'left' and 'right' point to valid (struct hfs_bnode)s, which
 *    resulted from splitting the old root node, or are both NULL
 *    if there was no root node before.
 * Postconditions:
 *   Upon success a new root node is added to 'tree' with either
 *    two children ('left' and 'right') or none.
 */
static void add_root(struct hfs_btree *tree,
                     struct hfs_bnode *left,
                     struct hfs_bnode *right)
{
        struct hfs_bnode_ref bnr;
        struct hfs_bnode *root;
        struct hfs_bkey *key;
        int keylen = tree->bthKeyLen;

        if (left && !right) {
                hfs_warn("add_root: LEFT but no RIGHT\n");
                return;
        }

        bnr = hfs_bnode_alloc(tree);
        if (!(root = bnr.bn)) {
                return;
        }

        root->sticky = HFS_STICKY;
        tree->root = root;
        tree->bthRoot = root->node;
        ++tree->bthDepth;

        root->ndNHeight = tree->bthDepth;
        root->ndFLink = 0;
        root->ndBLink = 0;

        if (!left) {
                /* tree was empty */
                root->ndType  = ndLeafNode;
                root->ndNRecs = 0;

                tree->bthFNode = root->node;
                tree->bthLNode = root->node;
        } else {
                root->ndType  = ndIndxNode;
                root->ndNRecs = 2;

                hfs_put_hs(sizeof(struct NodeDescriptor) + ROUND(1+keylen) +
                           sizeof(hfs_u32), RECTBL(root, 2));
                key = bnode_key(root, 1);
                key->KeyLen = keylen;
                memcpy(key->value,
                       ((struct hfs_bkey *)bnode_key(left, 1))->value, keylen);
                hfs_put_hl(left->node, bkey_record(key));
                
                hfs_put_hs(sizeof(struct NodeDescriptor) + 2*ROUND(1+keylen) +
                           2*sizeof(hfs_u32), RECTBL(root, 3));
                key = bnode_key(root, 2);
                key->KeyLen = keylen;
                memcpy(key->value,
                       ((struct hfs_bkey *)bnode_key(right, 1))->value, keylen);
                hfs_put_hl(right->node, bkey_record(key));

                /* the former root (left) is now just a normal node */
                left->sticky = HFS_NOT_STICKY;
                if ((left->next = bhash(tree, left->node))) {
                        left->next->prev = left;
                }
                bhash(tree, left->node) = left;
        }
        hfs_bnode_relse(&bnr);
        tree->dirt = 1;
}

/*
 * insert_empty_bnode()
 *
 * Description:
 *   Adds an empty node to the right of 'left'.
 * Input Variable(s):
 *   struct hfs_btree *tree: the tree to add a node to
 *   struct hfs_bnode *left: the node to add a node after
 * Output Variable(s):
 *   NONE
 * Returns:
 *   struct hfs_bnode_ref *: reference to the new bnode.
 * Preconditions:
 *   'tree' points to a valid (struct hfs_btree) with at least 1 free node.
 *   'left' points to a valid (struct hfs_bnode) belonging to 'tree'.
 * Postconditions:
 *   If NULL is returned then 'tree' and 'left' are unchanged.
 *   Otherwise a node with 0 records is inserted in the tree to the right
 *   of the node 'left'.  The 'ndFLink' of 'left' and the 'ndBLink' of
 *   the former right-neighbor of 'left' (if one existed) point to the
 *   new node.  If 'left' had no right neighbor and is a leaf node the
 *   the 'bthLNode' of 'tree' points to the new node.  The free-count and
 *   bitmap for 'tree' are kept current by hfs_bnode_alloc() which supplies
 *   the required node.
 */
static struct hfs_bnode_ref insert_empty_bnode(struct hfs_btree *tree,
                                               struct hfs_bnode *left)
{
        struct hfs_bnode_ref retval;
        struct hfs_bnode_ref right;

        retval = hfs_bnode_alloc(tree);
        if (!retval.bn) {
                hfs_warn("hfs_binsert: out of bnodes?.\n");
                goto done;
        }
        retval.bn->sticky = HFS_NOT_STICKY;
        if ((retval.bn->next = bhash(tree, retval.bn->node))) {
                retval.bn->next->prev = retval.bn;
        }
        bhash(tree, retval.bn->node) = retval.bn;

        if (left->ndFLink) {
                right = hfs_bnode_find(tree, left->ndFLink, HFS_LOCK_WRITE);
                if (!right.bn) {
                        hfs_warn("hfs_binsert: corrupt btree.\n");
                        hfs_bnode_bitop(tree, retval.bn->node, 0);
                        hfs_bnode_relse(&retval);
                        goto done;
                }
                right.bn->ndBLink = retval.bn->node;
                hfs_bnode_relse(&right);
        } else if (left->ndType == ndLeafNode) {
                tree->bthLNode = retval.bn->node;
                tree->dirt = 1;
        }

        retval.bn->ndFLink   = left->ndFLink;
        retval.bn->ndBLink   = left->node;
        retval.bn->ndType    = left->ndType;
        retval.bn->ndNHeight = left->ndNHeight;
        retval.bn->ndNRecs   = 0;

        left->ndFLink = retval.bn->node;

 done:
        return retval;
}

/*
 * split()
 *
 * Description:
 *   Splits an over full node during insertion.
 *   Picks the split point that results in the most-nearly equal
 *   space usage in the new and old nodes.
 * Input Variable(s):
 *   struct hfs_belem *elem: the over full node.
 *   int size: the number of bytes to be used by the new record and its key.
 * Output Variable(s):
 *   struct hfs_belem *elem: changed to indicate where the new record
 *    should be inserted.
 * Returns:
 *   struct hfs_bnode_ref: reference to the new bnode.
 * Preconditions:
 *   'elem' points to a valid path element corresponding to the over full node.
 *   'size' is positive.
 * Postconditions:
 *   The records in the node corresponding to 'elem' are redistributed across
 *   the old and new nodes so that after inserting the new record, the space
 *   usage in these two nodes is as equal as possible.
 *   'elem' is updated so that a call to binsert_nonfull() will insert the
 *   new record in the correct location.
 */
static inline struct hfs_bnode_ref split(struct hfs_belem *elem, int size)
{
        struct hfs_bnode *bnode = elem->bnr.bn;
        int nrecs, cutoff, index, tmp, used, in_right;
        struct hfs_bnode_ref right;

        right = insert_empty_bnode(bnode->tree, bnode);
        if (right.bn) {
                nrecs = bnode->ndNRecs;
                cutoff = (size + bnode_end(bnode) -
                              sizeof(struct NodeDescriptor) +
                              (nrecs+1)*sizeof(hfs_u16))/2;
                used = 0;
                in_right = 1;
                /* note that this only works because records sizes are even */
                for (index=1; index <= elem->record; ++index) {
                        tmp = (sizeof(hfs_u16) + bnode_rsize(bnode, index))/2;
                        used += tmp;
                        if (used > cutoff) {
                                goto found;
                        }
                        used += tmp;
                }
                tmp = (size + sizeof(hfs_u16))/2;
                used += tmp;
                if (used > cutoff) {
                        goto found;
                }
                in_right = 0;
                used += tmp;
                for (; index <= nrecs; ++index) {
                        tmp = (sizeof(hfs_u16) + bnode_rsize(bnode, index))/2;
                        used += tmp;
                        if (used > cutoff) {
                                goto found;
                        }
                        used += tmp;
                }
                /* couldn't find the split point! */
                hfs_bnode_relse(&right);
        }
        return right;

found:
        if (in_right) {
                elem->bnr = right;
                elem->record -= index-1;
        }
        hfs_bnode_shift_right(bnode, right.bn, index);

        return right;
}

/*
 * binsert()
 *
 * Description:
 *   Inserts a record in a tree known to have enough room, even if the
 *   insertion requires the splitting of nodes.
 * Input Variable(s):
 *    struct hfs_brec *brec: partial path to the node to insert in
 *    const struct hfs_bkey *key: key for the new record
 *    const void *data: data for the new record
 *    hfs_u8 keysize: size of the key
 *    hfs_u16 datasize: size of the data
 *    int reserve: number of nodes reserved in case of splits
 * Output Variable(s):
 *    *brec = NULL
 * Returns:
 *    int: 0 on success, error code on failure
 * Preconditions:
 *    'brec' points to a valid (struct hfs_brec) corresponding to a
 *     record in a leaf node, after which a record is to be inserted,
 *     or to "record 0" of the leaf node if the record is to be inserted
 *     before all existing records in the node.  The (struct hfs_brec)
 *     includes all ancestors of the leaf node that are needed to
 *     complete the insertion including the parents of any nodes that
 *     will be split.
 *    'key' points to a valid (struct hfs_bkey) which is appropriate
 *     to this tree, and which belongs at the insertion point.
 *    'data' points data appropriate for the indicated node.
 *    'keysize' gives the size in bytes of the key.
 *    'datasize' gives the size in bytes of the data.
 *    'reserve' gives the number of nodes that have been reserved in the
 *     tree to allow for splitting of nodes.
 * Postconditions:
 *    All 'reserve'd nodes have been either used or released.
 *    *brec = NULL
 *    On success the key and data have been inserted at the indicated
 *    location in the tree, all appropriate fields of the in-core data
 *    structures have been changed and updated versions of the on-disk
 *    data structures have been scheduled for write-back to disk.
 *    On failure the B*-tree is probably invalid both on disk and in-core.
 *
 *    XXX: Some attempt at repair might be made in the event of failure,
 *    or the fs should be remounted read-only so things don't get worse.
 */
static int binsert(struct hfs_brec *brec, const struct hfs_bkey *key,
                   const void *data, hfs_u8 keysize, hfs_u16 datasize,
                   int reserve)
{
        struct hfs_bnode_ref left, right, other;
        struct hfs_btree *tree = brec->tree;
        struct hfs_belem *belem = brec->bottom;
        int tmpsize = 1 + tree->bthKeyLen;
        struct hfs_bkey *tmpkey = hfs_malloc(tmpsize);
        hfs_u32 node;
        
        while ((belem >= brec->top) && (belem->flags & HFS_BPATH_OVERFLOW)) {
                left = belem->bnr;
                if (left.bn->ndFLink &&
                    hfs_bnode_in_brec(left.bn->ndFLink, brec)) {
                        hfs_warn("hfs_binsert: corrupt btree\n");
                        tree->reserved -= reserve;
                        hfs_free(tmpkey, tmpsize);
                        return -EIO;
                }
                        
                right = split(belem, ROUND(keysize+1) + ROUND(datasize));
                --reserve;
                --tree->reserved;
                if (!right.bn) {
                        hfs_warn("hfs_binsert: unable to split node!\n");
                        tree->reserved -= reserve;
                        hfs_free(tmpkey, tmpsize);
                        return -ENOSPC;
                }
                binsert_nonfull(brec, belem, key, data, keysize, datasize);
        
                if (belem->bnr.bn == left.bn) {
                        other = right;
                        if (belem->record == 1) {
                                hfs_bnode_update_key(brec, belem, left.bn, 0);
                        }
                } else {
                        other = left;
                }

                if (left.bn->node == tree->root->node) {
                        add_root(tree, left.bn, right.bn);
                        hfs_bnode_relse(&other);
                        goto done;
                }

                data = &node;
                datasize = sizeof(node);
                node = htonl(right.bn->node);
                key = tmpkey;
                keysize = tree->bthKeyLen;
                memcpy(tmpkey, bnode_key(right.bn, 1), keysize+1);
                hfs_bnode_relse(&other);
                
                --belem;
        }

        if (belem < brec->top) {
                hfs_warn("hfs_binsert: Missing parent.\n");
                tree->reserved -= reserve;
                hfs_free(tmpkey, tmpsize);
                return -EIO;
        }

        binsert_nonfull(brec, belem, key, data, keysize, datasize);

done:
        tree->reserved -= reserve;
        hfs_free(tmpkey, tmpsize);
        return 0;
}

/*================ Global functions ================*/

/*
 * hfs_binsert()
 *
 * Description:
 *   This function inserts a new record into a b-tree.
 * Input Variable(s):
 *   struct hfs_btree *tree: pointer to the (struct hfs_btree) to insert in
 *   struct hfs_bkey *key: pointer to the (struct hfs_bkey) to insert
 *   void *data: pointer to the data to associate with 'key' in the b-tree
 *   unsigned int datasize: the size of the data
 * Output Variable(s):
 *   NONE
 * Returns:
 *   int: 0 on success, error code on failure
 * Preconditions:
 *   'tree' points to a valid (struct hfs_btree)
 *   'key' points to a valid (struct hfs_bkey)
 *   'data' points to valid memory of length 'datasize'
 * Postconditions:
 *   If zero is returned then the record has been inserted in the
 *    indicated location updating all in-core data structures and
 *    scheduling all on-disk data structures for write-back.
 */
int hfs_binsert(struct hfs_btree *tree, const struct hfs_bkey *key,
                const void *data, hfs_u16 datasize)
{ 
        struct hfs_brec brec;
        struct hfs_belem *belem;
        int err, reserve, retval;
        hfs_u8 keysize;

        if (!tree || (tree->magic != HFS_BTREE_MAGIC) || !key || !data) {
                hfs_warn("hfs_binsert: invalid arguments.\n");
                return -EINVAL;
        }

        if (key->KeyLen > tree->bthKeyLen) {
                hfs_warn("hfs_binsert: oversized key\n");
                return -EINVAL;
        }

restart:
        if (!tree->bthNRecs) {
                /* create the root bnode */
                add_root(tree, NULL, NULL);
                if (!hfs_brec_init(&brec, tree, HFS_BFIND_INSERT)) {
                        hfs_warn("hfs_binsert: failed to create root.\n");
                        return -ENOSPC;
                }
        } else {
                err = hfs_bfind(&brec, tree, key, HFS_BFIND_INSERT);
                if (err < 0) {
                        hfs_warn("hfs_binsert: hfs_brec_find failed.\n");
                        return err;
                } else if (err == 0) {
                        hfs_brec_relse(&brec, NULL);
                        return -EEXIST;
                }
        }

        keysize = key->KeyLen;
        datasize = ROUND(datasize);
        belem = brec.bottom;
        belem->flags = 0;
        if (bnode_freespace(belem->bnr.bn) <
                            (sizeof(hfs_u16) + ROUND(keysize+1) + datasize)) {
                belem->flags |= HFS_BPATH_OVERFLOW;
        }
        if (belem->record == 0) {
                belem->flags |= HFS_BPATH_FIRST;
        }

        if (!belem->flags) {
                hfs_brec_lock(&brec, brec.bottom);
                reserve = 0;
        } else {
                reserve = brec.bottom - brec.top;
                if (brec.top == 0) {
                        ++reserve;
                }
                /* make certain we have enough nodes to proceed */
                if ((tree->bthFree - tree->reserved) < reserve) {
                        hfs_brec_relse(&brec, NULL);
                        hfs_btree_lock(tree);
                        if ((tree->bthFree - tree->reserved) < reserve) {
                                hfs_btree_extend(tree);
                        }
                        hfs_btree_unlock(tree);
                        if ((tree->bthFree - tree->reserved) < reserve) {
                                return -ENOSPC;
                        } else {
                                goto restart;
                        }
                }
                tree->reserved += reserve;
                hfs_brec_lock(&brec, NULL);
        }

        retval = binsert(&brec, key, data, keysize, datasize, reserve);
        hfs_brec_relse(&brec, NULL);
        if (!retval) {
                ++tree->bthNRecs;
                tree->dirt = 1;
        }
        return retval;
}