FreeBSD/Linux Kernel Cross Reference
sys/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 General 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;
   }

Cache object: 1e1a283032381ca3937d008ae74effc2