patch-2.1.78 linux/fs/hfs/bdelete.c

• Lines: 484
• Date: Sun Jan 4 10:40:17 1998
• Orig file: v2.1.77/linux/fs/hfs/bdelete.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.77/linux/fs/hfs/bdelete.c linux/fs/hfs/bdelete.c
@@ -0,0 +1,483 @@
+/*
+ * linux/fs/hfs/bdelete.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 delete 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"
+
+/*================ Variable-like macros ================*/
+
+#define FULL (HFS_SECTOR_SIZE - sizeof(struct NodeDescriptor))
+#define NO_SPACE (HFS_SECTOR_SIZE+1)
+
+/*================ File-local functions ================*/
+
+/*
+ * bdelete_nonempty()
+ *
+ * Description:
+ *   Deletes a record from a given bnode without regard to it becoming empty.
+ * Input Variable(s):
+ *   struct hfs_brec* brec: pointer to the brec for the deletion
+ *   struct hfs_belem* belem: which node in 'brec' to delete from
+ * Output Variable(s):
+ *   NONE
+ * Returns:
+ *   void
+ * Preconditions:
+ *   'brec' points to a valid (struct hfs_brec).
+ *   'belem' points to a valid (struct hfs_belem) in 'brec'.
+ * Postconditions:
+ *   The record has been inserted in the position indicated by 'brec'.
+ */
+static void bdelete_nonempty(struct hfs_brec *brec, struct hfs_belem *belem)
+{
+	int i, rec, nrecs, tomove;
+	hfs_u16 size;
+	hfs_u8 *start;
+	struct hfs_bnode *bnode = belem->bnr.bn;
+
+	rec = belem->record;
+	nrecs = bnode->ndNRecs;
+	size = bnode_rsize(bnode, rec);
+	tomove = bnode_offset(bnode, nrecs+1) - bnode_offset(bnode, rec+1);
+	
+	/* adjust the record table */
+	for (i = rec+1; i <= nrecs; ++i) {
+		hfs_put_hs(bnode_offset(bnode,i+1) - size, RECTBL(bnode,i));
+	}
+
+	/* move it down */
+	start = bnode_key(bnode, rec);
+	memmove(start, start + size, tomove);
+
+	/* update record count */
+	--bnode->ndNRecs;
+}
+
+/*
+ * del_root()
+ *
+ * Description:
+ *   Delete the current root bnode.
+ * Input Variable(s):
+ *   struct hfs_bnode_ref *root: reference to the root bnode
+ * Output Variable(s):
+ *   NONE
+ * Returns:
+ *   int: 0 on success, error code on failure
+ * Preconditions:
+ *   'root' refers to the root bnode with HFS_LOCK_WRITE access.
+ *   None of 'root's children are held with HFS_LOCK_WRITE access.
+ * Postconditions:
+ *   The current 'root' node is removed from the tree and the depth
+ *    of the tree is reduced by one.
+ *   If 'root' is an index node with exactly one child, then that
+ *    child becomes the new root of the tree.
+ *   If 'root' is an empty leaf node the tree becomes empty.
+ *   Upon return access to 'root' is relinquished.
+ */
+static int del_root(struct hfs_bnode_ref *root)
+{
+	struct hfs_btree *tree = root->bn->tree;
+	struct hfs_bnode_ref child;
+	hfs_u32 node;
+
+	if (root->bn->ndNRecs > 1) {
+		return 0;
+	} else if (root->bn->ndNRecs == 0) {
+		/* tree is empty */
+		tree->bthRoot = 0;
+		tree->root = NULL;
+		tree->bthRoot = 0;
+		tree->bthFNode = 0;
+		tree->bthLNode = 0;
+		--tree->bthDepth;
+		tree->dirt = 1;
+		if (tree->bthDepth) {
+			hfs_warn("hfs_bdelete: empty tree with bthDepth=%d\n",
+				 tree->bthDepth);
+			goto bail;
+		}
+		return hfs_bnode_free(root);
+	} else if (root->bn->ndType == ndIndxNode) {
+		/* tree is non-empty */
+		node = hfs_get_hl(bkey_record(bnode_datastart(root->bn)));
+
+		child = hfs_bnode_find(tree, node, HFS_LOCK_READ);
+		if (!child.bn) {
+			hfs_warn("hfs_bdelete: can't read child node.\n");
+			goto bail;
+		}
+			
+		child.bn->sticky = HFS_STICKY;
+        	if (child.bn->next) {
+                	child.bn->next->prev = child.bn->prev;
+        	}
+        	if (child.bn->prev) {
+                	child.bn->prev->next = child.bn->next;
+        	}
+        	if (bhash(tree, child.bn->node) == child.bn) {
+                	bhash(tree, child.bn->node) = child.bn->next;
+        	}
+		child.bn->next = NULL;
+		child.bn->prev = NULL;
+
+		tree->bthRoot = child.bn->node;
+		tree->root = child.bn;
+		hfs_bnode_relse(&child);
+
+		tree->bthRoot = node;
+		tree->bthFNode = node;
+		tree->bthLNode = node;
+		--tree->bthDepth;
+		tree->dirt = 1;
+		if (!tree->bthDepth) {
+			hfs_warn("hfs_bdelete: non-empty tree with "
+				 "bthDepth == 0\n");
+			goto bail;
+		}
+		return hfs_bnode_free(root);	/* marks tree dirty */
+	}
+	hfs_bnode_relse(root);
+	return 0;
+
+bail:
+	hfs_bnode_relse(root);
+	return -EIO;
+}
+
+
+/*
+ * delete_empty_bnode()
+ *
+ * Description:
+ *   Removes an empty non-root bnode from between 'left' and 'right'
+ * Input Variable(s):
+ *   hfs_u32 left_node: node number of 'left' or zero if 'left' is invalid
+ *   struct hfs_bnode_ref *left: reference to the left neighbor of the
+ *    bnode to remove, or invalid if no such neighbor exists.
+ *   struct hfs_bnode_ref *center: reference to the bnode to remove
+ *   hfs_u32 right_node: node number of 'right' or zero if 'right' is invalid
+ *   struct hfs_bnode_ref *right: reference to the right neighbor of the
+ *    bnode to remove, or invalid if no such neighbor exists.
+ * Output Variable(s):
+ *   NONE
+ * Returns:
+ *   void
+ * Preconditions:
+ *   'left_node' is as described above.
+ *   'left' points to a valid (struct hfs_bnode_ref) having HFS_LOCK_WRITE
+ *    access and referring to the left neighbor of 'center' if such a
+ *    neighbor exists, or invalid if no such neighbor exists.
+ *   'center' points to a valid (struct hfs_bnode_ref) having HFS_LOCK_WRITE
+ *    access and referring to the bnode to delete.
+ *   'right_node' is as described above.
+ *   'right' points to a valid (struct hfs_bnode_ref) having HFS_LOCK_WRITE
+ *    access and referring to the right neighbor of 'center' if such a
+ *    neighbor exists, or invalid if no such neighbor exists.
+ * Postconditions:
+ *   If 'left' is valid its 'ndFLink' field becomes 'right_node'.
+ *   If 'right' is valid its 'ndBLink' field becomes 'left_node'.
+ *   If 'center' was the first leaf node then the tree's 'bthFNode'
+ *    field becomes 'right_node' 
+ *   If 'center' was the last leaf node then the tree's 'bthLNode'
+ *    field becomes 'left_node' 
+ *   'center' is NOT freed and access to the nodes is NOT relinquished.
+ */
+static void delete_empty_bnode(hfs_u32 left_node, struct hfs_bnode_ref *left,
+			       struct hfs_bnode_ref *center,
+			       hfs_u32 right_node, struct hfs_bnode_ref *right)
+{
+	struct hfs_bnode *bnode = center->bn;
+
+	if (left_node) {
+		left->bn->ndFLink = right_node;
+	} else if (bnode->ndType == ndLeafNode) {
+		bnode->tree->bthFNode = right_node;
+		bnode->tree->dirt = 1;
+	}
+
+	if (right_node) {
+		right->bn->ndBLink = left_node;
+	} else if (bnode->ndType == ndLeafNode) {
+		bnode->tree->bthLNode = left_node;
+		bnode->tree->dirt = 1;
+	}
+}
+
+/*
+ * balance()
+ *
+ * Description:
+ *   Attempt to equalize space usage in neighboring bnodes.
+ * Input Variable(s):
+ *   struct hfs_bnode *left: the left bnode.
+ *   struct hfs_bnode *right: the right bnode.
+ * Output Variable(s):
+ *   NONE
+ * Returns:
+ *   void
+ * Preconditions:
+ *   'left' and 'right' point to valid (struct hfs_bnode)s obtained
+ *    with HFS_LOCK_WRITE access, and are neighbors.
+ * Postconditions:
+ *   Records are shifted either left or right to make the space usage
+ *   nearly equal.  When exact equality is not possible the break
+ *   point is chosen to reduce data movement.
+ *   The key corresponding to 'right' in its parent is NOT updated.
+ */
+static void balance(struct hfs_bnode *left, struct hfs_bnode *right)
+{
+	int index, left_free, right_free, half;
+
+	left_free = bnode_freespace(left);
+	right_free = bnode_freespace(right);
+	half = (left_free + right_free)/2;
+
+	if (left_free < right_free) {
+		/* shift right to balance */
+		index = left->ndNRecs + 1;
+		while (right_free >= half) {
+			--index;
+			right_free -= bnode_rsize(left,index)+sizeof(hfs_u16);
+		}
+		if (index < left->ndNRecs) {
+#if defined(DEBUG_ALL) || defined(DEBUG_BALANCE)
+			hfs_warn("shifting %d of %d recs right to balance: ",
+			       left->ndNRecs - index, left->ndNRecs);
+#endif
+			hfs_bnode_shift_right(left, right, index+1);
+#if defined(DEBUG_ALL) || defined(DEBUG_BALANCE)
+			hfs_warn("%d,%d\n", left->ndNRecs, right->ndNRecs);
+#endif
+		}
+	} else {
+		/* shift left to balance */
+		index = 0;
+		while (left_free >= half) {
+			++index;
+			left_free -= bnode_rsize(right,index)+sizeof(hfs_u16);
+		}
+		if (index > 1) {
+#if defined(DEBUG_ALL) || defined(DEBUG_BALANCE)
+			hfs_warn("shifting %d of %d recs left to balance: ",
+			       index-1, right->ndNRecs);
+#endif
+			hfs_bnode_shift_left(left, right, index-1);
+#if defined(DEBUG_ALL) || defined(DEBUG_BALANCE)
+			hfs_warn("%d,%d\n", left->ndNRecs, right->ndNRecs);
+#endif
+		}
+	}
+}
+
+/*
+ * bdelete()
+ *
+ * Delete the given record from a B-tree.
+ */
+static int bdelete(struct hfs_brec *brec)
+{
+	struct hfs_btree *tree = brec->tree;
+	struct hfs_belem *belem = brec->bottom;
+	struct hfs_belem *parent = (belem-1);
+	struct hfs_bnode *bnode;
+	hfs_u32 left_node, right_node;
+	struct hfs_bnode_ref left, right;
+	int left_space, right_space, min_space;
+	int fix_right_key;
+	int fix_key;
+	
+	while ((belem > brec->top) &&
+	       (belem->flags & (HFS_BPATH_UNDERFLOW | HFS_BPATH_FIRST))) {
+		bnode = belem->bnr.bn;
+		fix_key = belem->flags & HFS_BPATH_FIRST;
+		fix_right_key = 0;
+
+		bdelete_nonempty(brec, belem);
+
+		if (bnode->node == tree->root->node) {
+			del_root(&belem->bnr);
+			--brec->bottom;
+			goto done;
+		}
+
+		/* check for btree corruption which could lead to deadlock */
+		left_node = bnode->ndBLink;
+		right_node = bnode->ndFLink;
+		if ((left_node && hfs_bnode_in_brec(left_node, brec)) ||
+		    (right_node && hfs_bnode_in_brec(right_node, brec)) ||
+		    (left_node == right_node)) {
+			hfs_warn("hfs_bdelete: corrupt btree\n");
+			hfs_brec_relse(brec, NULL);
+			return -EIO;
+		}
+
+		/* grab the left neighbor if it exists */
+		if (left_node) {
+			hfs_bnode_lock(&belem->bnr, HFS_LOCK_RESRV);
+			left = hfs_bnode_find(tree,left_node,HFS_LOCK_WRITE);
+			if (!left.bn) {
+				hfs_warn("hfs_bdelete: unable to read left "
+					 "neighbor.\n");
+				hfs_brec_relse(brec, NULL);
+				return -EIO;
+			}
+			hfs_bnode_lock(&belem->bnr, HFS_LOCK_WRITE);
+			if (parent->record != 1) {
+				left_space = bnode_freespace(left.bn);
+			} else {
+				left_space = NO_SPACE;
+			}
+		} else {
+			left.bn = NULL;
+			left_space = NO_SPACE;
+		}
+
+		/* grab the right neighbor if it exists */
+		if (right_node) {
+			right = hfs_bnode_find(tree,right_node,HFS_LOCK_WRITE);
+			if (!right.bn) {
+				hfs_warn("hfs_bdelete: unable to read right "
+					 "neighbor.\n");
+				hfs_bnode_relse(&left);
+				hfs_brec_relse(brec, NULL);
+				return -EIO;
+			}
+			if (parent->record < parent->bnr.bn->ndNRecs) {
+				right_space = bnode_freespace(right.bn);
+			} else {
+				right_space = NO_SPACE;
+			}
+		} else {
+			right.bn = NULL;
+			right_space = NO_SPACE;
+		}
+
+		if (left_space < right_space) {
+			min_space = left_space;
+		} else {
+			min_space = right_space;
+		}
+
+		if (min_space == NO_SPACE) {
+			hfs_warn("hfs_bdelete: no siblings?\n");
+			hfs_brec_relse(brec, NULL);
+			return -EIO;
+		}
+
+		if (bnode->ndNRecs == 0) {
+			delete_empty_bnode(left_node, &left, &belem->bnr,
+					   right_node, &right);
+		} else if (min_space + bnode_freespace(bnode) >= FULL) {
+			if ((right_space == NO_SPACE) ||
+			    ((right_space == min_space) &&
+			     (left_space != NO_SPACE))) {
+				hfs_bnode_shift_left(left.bn, bnode,
+						     bnode->ndNRecs);
+			} else {
+				hfs_bnode_shift_right(bnode, right.bn, 1);
+				fix_right_key = 1;
+			}
+			delete_empty_bnode(left_node, &left, &belem->bnr,
+					   right_node, &right);
+		} else if (min_space == right_space) {
+			balance(bnode, right.bn);
+			fix_right_key = 1;
+		} else {
+			balance(left.bn, bnode);
+			fix_key = 1;
+		}
+
+		if (fix_right_key) {
+			hfs_bnode_update_key(brec, belem, right.bn, 1);
+		}
+
+		hfs_bnode_relse(&left);
+		hfs_bnode_relse(&right);
+
+		if (bnode->ndNRecs) {
+			if (fix_key) {
+				hfs_bnode_update_key(brec, belem, bnode, 0);
+			}
+			goto done;
+		}
+
+		hfs_bnode_free(&belem->bnr);
+		--brec->bottom;
+		belem = parent;
+		--parent;
+	}
+
+	if (belem < brec->top) {
+		hfs_warn("hfs_bdelete: Missing parent.\n");
+		hfs_brec_relse(brec, NULL);
+		return -EIO;
+	}
+
+	bdelete_nonempty(brec, belem);
+
+done:
+	hfs_brec_relse(brec, NULL);
+	return 0;
+}
+
+/*================ Global functions ================*/
+
+/*
+ * hfs_bdelete()
+ *
+ * Delete the requested record from a B-tree.
+ */
+int hfs_bdelete(struct hfs_btree *tree, const struct hfs_bkey *key)
+{ 
+	struct hfs_belem *belem;
+	struct hfs_bnode *bnode;
+	struct hfs_brec brec;
+	int retval;
+
+	if (!tree || (tree->magic != HFS_BTREE_MAGIC) || !key) {
+		hfs_warn("hfs_bdelete: invalid arguments.\n");
+		return -EINVAL;
+	}
+
+	retval = hfs_bfind(&brec, tree, key, HFS_BFIND_DELETE);
+	if (!retval) {
+		belem = brec.bottom;
+		bnode = belem->bnr.bn;
+
+		belem->flags = 0;
+        	if ((bnode->ndNRecs * sizeof(hfs_u16) + bnode_end(bnode) -
+		     bnode_rsize(bnode, belem->record)) < FULL/2) {
+			belem->flags |= HFS_BPATH_UNDERFLOW;
+		}
+		if (belem->record == 1) {
+			belem->flags |= HFS_BPATH_FIRST;
+		}
+
+		if (!belem->flags) {
+			hfs_brec_lock(&brec, brec.bottom);
+		} else {
+			hfs_brec_lock(&brec, NULL);
+		}
+
+		retval = bdelete(&brec);
+		if (!retval) {
+			--brec.tree->bthNRecs;
+			brec.tree->dirt = 1;
+		}
+		hfs_brec_relse(&brec, NULL);
+	}
+	return retval;
+}