reiserfscore/stree.c

/*
 *  Copyright 1996-2004 by Hans Reiser, licensing governed by
 *  reiserfsprogs/README
 */

/*
 *  Written by Anatoly P. Pinchuk pap@namesys.botik.ru
 *  Programm System Institute
 *  Pereslavl-Zalessky Russia
 */

/*
 *  This file contains functions dealing with internal tree
 *
 * comp_keys
 * comp_short_keys
 * bin_search
 * get_lkey
 * get_rkey
 * key_in_buffer
 * decrement_bcount
 * decrement_counters_in_path
 * pathrelse
 * search_by_key
 * search_for_position_by_key
 * comp_items
 * prepare_for_delete_or_cut
 * calc_deleted_bytes_number
 * init_tb_struct
 * reiserfs_delete_item
 * indirect_to_direct
 * maybe_indirect_to_direct
 * reiserfs_cut_from_item
 * reiserfs_cut_dir_entry
 * reiserfs_paste_into_item
 * reiserfs_insert_item
 */
#include "includes.h"

/* Does the buffer contain a disk block which is in the tree. */
inline int B_IS_IN_TREE(const struct buffer_head *p_s_bh)
{
	return (get_blkh_level(B_BLK_HEAD(p_s_bh)) != FREE_LEVEL);
}

/*
 Compare keys using REISERFS_SHORT_KEY_LEN fields.
 Returns:  -1 if key1 < key2
            0 if key1 = key2
            1 if key1 > key2
*/

int comp_short_keys(const void *k1, const void *k2)
{
	int n_key_length = REISERFS_SHORT_KEY_LEN;
	__le32 *p_s_key1 = (__le32 *) k1;
	__le32 *p_s_key2 = (__le32 *) k2;
	__u32 u1, u2;

	for (; n_key_length--; ++p_s_key1, ++p_s_key2) {
		u1 = d32_get(p_s_key1, 0);
		u2 = d32_get(p_s_key2, 0);
		if (u1 < u2)
			return -1;
		if (u1 > u2)
			return 1;
	}

	return 0;
}

int comp_keys_3(const void *p1, const void *p2)
{
	int retval;
	const struct reiserfs_key *k1 = p1;
	const struct reiserfs_key *k2 = p2;
	loff_t off1, off2;

	retval = comp_short_keys(k1, k2);
	if (retval)
		return retval;
	off1 = get_offset(k1);
	off2 = get_offset(k2);
	if (off1 < off2)
		return -1;

	if (off1 > off2)
		return 1;

	return 0;
}

/*
 Compare keys using all 4 key fields.
 Returns:  -1 if key1 < key2
            0 if key1 = key2
            1 if key1 > key2
*/
int comp_keys(const void *p1, const void *p2)
{
	int retval;
	const struct reiserfs_key *k1 = p1;
	const struct reiserfs_key *k2 = p2;
	__u32 u1, u2;

	retval = comp_keys_3(k1, k2);
	if (retval)
		return retval;

	u1 = get_type(k1);
	u2 = get_type(k2);

	if (u1 < u2)
		return -1;

	if (u1 > u2)
		return 1;

	return 0;
}

/**************************************************************************
 *  Binary search toolkit function                                        *
 *  Search for an item in the array by the item key                       *
 *  Returns:    1 if found,  0 if not found;                              *
 *        *p_n_pos = number of the searched element if found, else the    *
 *        number of the first element that is larger than p_v_key.        *
 **************************************************************************/
/* For those not familiar with binary search: n_lbound is the leftmost item that it
 could be, n_rbound the rightmost item that it could be.  We examine the item
 halfway between n_lbound and n_rbound, and that tells us either that we can increase
 n_lbound, or decrease n_rbound, or that we have found it, or if n_lbound <= n_rbound that
 there are no possible items, and we have not found it. With each examination we
 cut the number of possible items it could be by one more than half rounded down,
 or we find it. */
int bin_search(const void *p_v_key,	/* Key to search for.                   */
	       const void *p_v_base,	/* First item in the array.             */
	       int p_n_num,	/* Number of items in the array.        */
	       int p_n_width,	/* Item size in the array.
				   searched. Lest the reader be
				   confused, note that this is crafted
				   as a general function, and when it
				   is applied specifically to the array
				   of item headers in a node, p_n_width
				   is actually the item header size not
				   the item size.                      */
	       unsigned int *p_n_pos	/* Number of the searched
					   for element. */
    )
{
	int n_rbound, n_lbound, n_j;

	for (n_j = ((n_rbound = p_n_num - 1) + (n_lbound = 0)) / 2;
	     n_lbound <= n_rbound; n_j = (n_rbound + n_lbound) / 2)
		switch (COMP_KEYS
			((struct reiserfs_key *)((char *)p_v_base +
						 n_j * p_n_width), p_v_key)) {
		case -1:
			n_lbound = n_j + 1;
			continue;
		case 1:
			n_rbound = n_j - 1;
			continue;
		case 0:
			*p_n_pos = n_j;
			return ITEM_FOUND;	/* Key found in the array.  */
		}

	/* bin_search did not find given key, it returns position of key,
	   that is minimal and greater than the given one. */
	*p_n_pos = n_lbound;
	return ITEM_NOT_FOUND;
}

/* Minimal possible key. It is never in the tree. */
const struct reiserfs_key MIN_KEY =
	{ constant_cpu_to_le32(0), constant_cpu_to_le32(0),
	  {{constant_cpu_to_le32(0), constant_cpu_to_le32(0)},} };

/* Maximal possible key. It is never in the tree. */
const struct reiserfs_key MAX_KEY =
	{ constant_cpu_to_le32(0xffffffff), constant_cpu_to_le32(0xffffffff),
	  {{constant_cpu_to_le32(0xffffffff),
	    constant_cpu_to_le32(0xffffffff)},} };

/* Get delimiting key of the buffer by looking for it in the buffers in the
   path, starting from the bottom of the path, and going upwards.  We must
   check the path's validity at each step.  If the key is not in the path,
   there is no delimiting key in the tree (buffer is first or last buffer in
   tree), and in this case we return a special key, either MIN_KEY or
   MAX_KEY. */
static const struct reiserfs_key *get_lkey(const struct reiserfs_path *p_s_chk_path,
				    const reiserfs_filsys_t fs)
{
	struct reiserfs_super_block *sb;
	int n_position, n_path_offset = p_s_chk_path->path_length;
	struct buffer_head *p_s_parent;

	sb = fs->fs_ondisk_sb;

	/* While not higher in path than first element. */
	while (n_path_offset-- > FIRST_PATH_ELEMENT_OFFSET) {
		/* Parent at the path is not in the tree now. */
		if (!B_IS_IN_TREE
		    (p_s_parent =
		     PATH_OFFSET_PBUFFER(p_s_chk_path, n_path_offset)))
			return &MAX_KEY;
		/* Check whether position in the parent is correct. */
		if ((n_position =
		     PATH_OFFSET_POSITION(p_s_chk_path,
					  n_path_offset)) >
		    B_NR_ITEMS(p_s_parent))
			return &MAX_KEY;
		/* Check whether parent at the path really points to the child. */
		if (get_dc_child_blocknr(B_N_CHILD(p_s_parent, n_position)) !=
		    PATH_OFFSET_PBUFFER(p_s_chk_path,
					n_path_offset + 1)->b_blocknr)
			return &MAX_KEY;
		/* Return delimiting key if position in the parent is not equal to zero. */
		if (n_position)
			return internal_key(p_s_parent, n_position - 1);
	}
	/* Return MIN_KEY if we are in the root of the buffer tree. */
	if (PATH_OFFSET_PBUFFER(p_s_chk_path, FIRST_PATH_ELEMENT_OFFSET)->
	    b_blocknr == get_sb_root_block(sb))
		return &MIN_KEY;
	return &MAX_KEY;
}

/* Get delimiting key of the buffer at the path and its right neighbor. */
const struct reiserfs_key *get_rkey(const struct reiserfs_path *p_s_chk_path,
				    const reiserfs_filsys_t fs)
{
	struct reiserfs_super_block *sb;
	int n_position, n_path_offset = p_s_chk_path->path_length;
	struct buffer_head *p_s_parent;

	sb = fs->fs_ondisk_sb;

	while (n_path_offset-- > FIRST_PATH_ELEMENT_OFFSET) {
		/* Parent at the path is not in the tree now. */
		if (!B_IS_IN_TREE
		    (p_s_parent =
		     PATH_OFFSET_PBUFFER(p_s_chk_path, n_path_offset)))
			return &MIN_KEY;
		/* Check whether position in the parrent is correct. */
		if ((n_position =
		     PATH_OFFSET_POSITION(p_s_chk_path,
					  n_path_offset)) >
		    B_NR_ITEMS(p_s_parent))
			return &MIN_KEY;
		/* Check whether parent at the path really points to the child. */
		if (get_dc_child_blocknr(B_N_CHILD(p_s_parent, n_position)) !=
		    PATH_OFFSET_PBUFFER(p_s_chk_path,
					n_path_offset + 1)->b_blocknr)
			return &MIN_KEY;
		/* Return delimiting key if position in the parent is not the last one. */
		if (n_position != B_NR_ITEMS(p_s_parent))
			return internal_key(p_s_parent, n_position);
	}
	/* Return MAX_KEY if we are in the root of the buffer tree. */
	if (PATH_OFFSET_PBUFFER(p_s_chk_path, FIRST_PATH_ELEMENT_OFFSET)->
	    b_blocknr == get_sb_root_block(sb))
		return &MAX_KEY;
	return &MIN_KEY;
}

/* Check whether a key is contained in the tree rooted from a buffer at a
   path.  This works by looking at the left and right delimiting keys for the
   buffer in the last path_element in the path.  These delimiting keys are
   stored at least one level above that buffer in the tree. If the buffer is
   the first or last node in the tree order then one of the delimiting keys
   may be absent, and in this case get_lkey and get_rkey return a special key
   which is MIN_KEY or MAX_KEY. */
static inline int key_in_buffer(const struct reiserfs_path *p_s_chk_path,	/* Path which should be checked.  */
				const struct reiserfs_key *p_s_key,	/* Key which should be checked.   */
				reiserfs_filsys_t fs	/* Super block pointer.           */
    )
{

	if (COMP_KEYS(get_lkey(p_s_chk_path, fs), p_s_key) == 1)
		return 0;
	if (COMP_KEYS(p_s_key, get_rkey(p_s_chk_path, fs)) != -1)
		return 0;
	return 1;
}

/* Release all buffers in the path. */
void pathrelse(struct reiserfs_path *p_s_search_path)
{
	int n_path_offset = p_s_search_path->path_length;

	while (n_path_offset > ILLEGAL_PATH_ELEMENT_OFFSET)
		brelse(PATH_OFFSET_PBUFFER(p_s_search_path, n_path_offset--));

	p_s_search_path->path_length = ILLEGAL_PATH_ELEMENT_OFFSET;
}

/**************************************************************************
 * Algorithm   SearchByKey                                                *
 *             look for item in internal tree on the disk by its key      *
 * Input:  p_s_sb   -  super block                                        *
 *         p_s_key  - pointer to the key to search                        *
 * Output: true value -  1 - found,  0 - not found                        *
 *         p_s_search_path - path from the root to the needed leaf        *
 **************************************************************************/

/* This function fills up the path from the root to the leaf as it
   descends the tree looking for the key.  It uses reiserfs_bread to
   try to find buffers in the cache given their block number.  If it
   does not find them in the cache it reads them from disk.  For each
   node search_by_key finds using reiserfs_bread it then uses
   bin_search to look through that node.  bin_search will find the
   position of the block_number of the next node if it is looking
   through an internal node.  If it is looking through a leaf node
   bin_search will find the position of the item which has key either
   equal to given key, or which is the maximal key less than the given
   key.  search_by_key returns a path that must be checked for the
   correctness of the top of the path but need not be checked for the
   correctness of the bottom of the path */
int search_by_key(reiserfs_filsys_t fs, const struct reiserfs_key *p_s_key,	/* Key to search */
		  struct reiserfs_path *p_s_search_path,	/* This structure was
								   allocated and
								   initialized by the
								   calling
								   function. It is
								   filled up by this
								   function.  */
		  int n_stop_level)
{				/* How far down the tree to search. */
	struct reiserfs_super_block *sb;
	unsigned int n_block_number,
	    expected_level, n_block_size = fs->fs_blocksize;
	struct buffer_head *p_s_bh;
	struct reiserfs_path_element *p_s_last_element;
	int n_retval;

	sb = fs->fs_ondisk_sb;
	n_block_number = get_sb_root_block(sb);
	expected_level = get_sb_tree_height(sb);

	/* As we add each node to a path we increase its count.  This
	   means that we must be careful to release all nodes in a path
	   before we either discard the path struct or re-use the path
	   struct, as we do here. */
	pathrelse(p_s_search_path);

	/* With each iteration of this loop we search through the items in
	   the current node, and calculate the next current node(next path
	   element) for the next iteration of this loop.. */
	while (1) {

		/* prep path to have another element added to it. */
		p_s_last_element =
		    PATH_OFFSET_PELEMENT(p_s_search_path,
					 ++p_s_search_path->path_length);
		expected_level--;

		/* Read the next tree node, and set the last element in the
		   path to have a pointer to it. */
		if (!(p_s_bh = p_s_last_element->pe_buffer =
		      bread(fs->fs_dev, n_block_number, n_block_size))) {
			p_s_search_path->path_length--;
			pathrelse(p_s_search_path);
			return IO_ERROR;
		}

		/* It is possible that schedule occured. We must check whether
		   the key to search is still in the tree rooted from the
		   current buffer. If not then repeat search from the root. */
		if (!B_IS_IN_TREE(p_s_bh) ||
		    !key_in_buffer(p_s_search_path, p_s_key, fs))
			reiserfs_panic
			    ("search_by_key: something wrong with the tree");

		/* make sure, that the node contents look like a node of
		   certain level */
		if (!is_tree_node(p_s_bh, expected_level)) {
			print_block(stderr, NULL, p_s_bh, 3, -1, -1);
			reiserfs_panic("search_by_key: expected level %d",
				       expected_level);
		}

		/* ok, we have acquired next formatted node in the tree */
		n_retval =
		    bin_search(p_s_key, item_head(p_s_bh, 0),
			       B_NR_ITEMS(p_s_bh),
			       is_leaf_node(p_s_bh) ? IH_SIZE : KEY_SIZE,
			       &(p_s_last_element->pe_position));
		if (get_blkh_level(B_BLK_HEAD(p_s_bh)) == n_stop_level)
			return n_retval;

		/* we are not in the stop level */
		if (n_retval == ITEM_FOUND)
			/* item has been found, so we choose the pointer which is
			   to the right of the found one */
			p_s_last_element->pe_position++;

		/* if item was not found we choose the position which is to
		   the left of the found item. This requires no code,
		   bin_search did it already. */

		/* So we have chosen a position in the current node which is
		   an internal node.  Now we calculate child block number by
		   position in the node. */
		n_block_number =
		    get_dc_child_blocknr(B_N_CHILD
					 (p_s_bh,
					  p_s_last_element->pe_position));
	}
}