/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * extent_tree.c
 *
 * Copyright (C) 2009 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <errno.h>
#include <assert.h>

#include "ocfs2/byteorder.h"
#include "ocfs2/ocfs2.h"
#include "extent_tree.h"

static void ocfs2_dinode_set_last_eb_blk(struct ocfs2_extent_tree *et,
					 uint64_t blkno)
{
	struct ocfs2_dinode *di = et->et_object;

	di->i_last_eb_blk = blkno;
}

static uint64_t ocfs2_dinode_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
	struct ocfs2_dinode *di = et->et_object;

	return di->i_last_eb_blk;
}

static void ocfs2_dinode_update_clusters(struct ocfs2_extent_tree *et,
					 uint32_t clusters)
{
	struct ocfs2_dinode *di = et->et_object;

	di->i_clusters += clusters;
}
static void ocfs2_dinode_fill_root_el(struct ocfs2_extent_tree *et)
{
	struct ocfs2_dinode *di = et->et_object;

	et->et_root_el = &di->id2.i_list;
}

static struct ocfs2_extent_tree_operations ocfs2_dinode_et_ops = {
	.eo_set_last_eb_blk	= ocfs2_dinode_set_last_eb_blk,
	.eo_get_last_eb_blk	= ocfs2_dinode_get_last_eb_blk,
	.eo_update_clusters	= ocfs2_dinode_update_clusters,
	.eo_fill_root_el	= ocfs2_dinode_fill_root_el,
};

static void ocfs2_refcount_tree_fill_root_el(struct ocfs2_extent_tree *et)
{
	struct ocfs2_refcount_block *rb = et->et_object;

	et->et_root_el = &rb->rf_list;
}

static void ocfs2_refcount_tree_set_last_eb_blk(struct ocfs2_extent_tree *et,
						uint64_t blkno)
{
	struct ocfs2_refcount_block *rb = et->et_object;

	rb->rf_last_eb_blk = blkno;
}

static uint64_t
ocfs2_refcount_tree_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
	struct ocfs2_refcount_block *rb = et->et_object;

	return rb->rf_last_eb_blk;
}

static void ocfs2_refcount_tree_update_clusters(struct ocfs2_extent_tree *et,
						uint32_t clusters)
{
	struct ocfs2_refcount_block *rb = et->et_object;

	rb->rf_clusters += clusters;
}

static enum ocfs2_contig_type
ocfs2_refcount_tree_extent_contig(ocfs2_filesys *fs,
				  struct ocfs2_extent_tree *et,
				  struct ocfs2_extent_rec *ext,
				  struct ocfs2_extent_rec *insert_rec)
{
	return CONTIG_NONE;
}

static struct ocfs2_extent_tree_operations ocfs2_refcount_tree_et_ops = {
	.eo_set_last_eb_blk	= ocfs2_refcount_tree_set_last_eb_blk,
	.eo_get_last_eb_blk	= ocfs2_refcount_tree_get_last_eb_blk,
	.eo_update_clusters	= ocfs2_refcount_tree_update_clusters,
	.eo_fill_root_el	= ocfs2_refcount_tree_fill_root_el,
	.eo_extent_contig	= ocfs2_refcount_tree_extent_contig,
};

static void ocfs2_xattr_value_fill_root_el(struct ocfs2_extent_tree *et)
{
	struct ocfs2_xattr_value_root *xv = et->et_object;

	et->et_root_el = &xv->xr_list;
}

static void ocfs2_xattr_value_set_last_eb_blk(struct ocfs2_extent_tree *et,
					      uint64_t blkno)
{
	struct ocfs2_xattr_value_root *xv = et->et_object;

	xv->xr_last_eb_blk = blkno;
}

static uint64_t ocfs2_xattr_value_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
	struct ocfs2_xattr_value_root *xv = et->et_object;

	return xv->xr_last_eb_blk;
}

static void ocfs2_xattr_value_update_clusters(struct ocfs2_extent_tree *et,
					      uint32_t clusters)
{
	struct ocfs2_xattr_value_root *xv = et->et_object;

	xv->xr_clusters += clusters;
}

static uint32_t ocfs2_xattr_value_get_clusters(struct ocfs2_extent_tree *et)
{
	struct ocfs2_xattr_value_root *xv = et->et_object;

	return xv->xr_clusters;
}

static struct ocfs2_extent_tree_operations ocfs2_xattr_value_et_ops = {
	.eo_set_last_eb_blk	= ocfs2_xattr_value_set_last_eb_blk,
	.eo_get_last_eb_blk	= ocfs2_xattr_value_get_last_eb_blk,
	.eo_update_clusters	= ocfs2_xattr_value_update_clusters,
	.eo_get_clusters	= ocfs2_xattr_value_get_clusters,
	.eo_fill_root_el	= ocfs2_xattr_value_fill_root_el,
};

static void ocfs2_dx_root_set_last_eb_blk (struct ocfs2_extent_tree *et,
						uint64_t blkno)
{
	struct ocfs2_dx_root_block *dx_root = et->et_object;
	dx_root->dr_last_eb_blk = blkno;
}

static uint64_t ocfs2_dx_root_get_last_eb_blk (struct ocfs2_extent_tree *et)
{
	struct ocfs2_dx_root_block *dx_root = et->et_object;
	return dx_root->dr_last_eb_blk;
}

static void ocfs2_dx_root_update_clusters(struct ocfs2_extent_tree *et,
					uint32_t clusters)
{
	struct ocfs2_dx_root_block *dx_root = et->et_object;
	dx_root->dr_clusters += clusters;
}

static int ocfs2_dx_root_sanity_check(struct ocfs2_extent_tree *et)
{
	struct ocfs2_dx_root_block *dx_root = (struct ocfs2_dx_root_block *)et->et_object;
	assert(OCFS2_IS_VALID_DX_ROOT(dx_root));

	return 0;
}

static void ocfs2_dx_root_fill_root_el (struct ocfs2_extent_tree *et)
{
	struct ocfs2_dx_root_block *dx_root = et->et_object;

	et->et_root_el = &dx_root->dr_list;
}

static struct ocfs2_extent_tree_operations ocfs2_dx_root_et_ops = {
	.eo_set_last_eb_blk	= ocfs2_dx_root_set_last_eb_blk,
	.eo_get_last_eb_blk	= ocfs2_dx_root_get_last_eb_blk,
	.eo_update_clusters	= ocfs2_dx_root_update_clusters,
	.eo_sanity_check	= ocfs2_dx_root_sanity_check,
	.eo_fill_root_el	= ocfs2_dx_root_fill_root_el,
};

static void __ocfs2_init_extent_tree(struct ocfs2_extent_tree *et,
				     ocfs2_filesys *fs,
				     char *buf,
				     uint64_t blkno,
				     ocfs2_root_write_func write,
				     void *obj,
				     struct ocfs2_extent_tree_operations *ops)
{
	et->et_ops = ops;
	et->et_root_buf = buf;
	et->et_root_blkno = blkno;
	et->et_root_write = write;
	et->et_object = obj;

	et->et_ops->eo_fill_root_el(et);
	if (!et->et_ops->eo_fill_max_leaf_clusters)
		et->et_max_leaf_clusters = 0;
	else
		et->et_ops->eo_fill_max_leaf_clusters(fs, et);
}

void ocfs2_init_dinode_extent_tree(struct ocfs2_extent_tree *et,
				   ocfs2_filesys *fs,
				   char *buf, uint64_t blkno)
{
	__ocfs2_init_extent_tree(et, fs, buf, blkno,
				 ocfs2_write_inode,
				 buf, &ocfs2_dinode_et_ops);
}

void ocfs2_init_refcount_extent_tree(struct ocfs2_extent_tree *et,
				     ocfs2_filesys *fs,
				     char *buf, uint64_t blkno)
{
	__ocfs2_init_extent_tree(et, fs, buf, blkno,
				 ocfs2_write_refcount_block,
				 buf, &ocfs2_refcount_tree_et_ops);
}

void ocfs2_init_xattr_value_extent_tree(struct ocfs2_extent_tree *et,
					ocfs2_filesys *fs,
					char *buf, uint64_t blkno,
					ocfs2_root_write_func write,
					struct ocfs2_xattr_value_root *xv)
{
	__ocfs2_init_extent_tree(et, fs, buf, blkno, write,
				 xv, &ocfs2_xattr_value_et_ops);
}

void ocfs2_init_dx_root_extent_tree(struct ocfs2_extent_tree *et,
				    ocfs2_filesys *fs,
				    char *buf, uint64_t blkno)
{
	__ocfs2_init_extent_tree(et, fs, buf, blkno,
				ocfs2_write_dx_root,
				buf, &ocfs2_dx_root_et_ops);
}

static inline void ocfs2_et_set_last_eb_blk(struct ocfs2_extent_tree *et,
					    uint64_t new_last_eb_blk)
{
	et->et_ops->eo_set_last_eb_blk(et, new_last_eb_blk);
}

static inline uint64_t ocfs2_et_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
	return et->et_ops->eo_get_last_eb_blk(et);
}

static inline void ocfs2_et_update_clusters(struct ocfs2_extent_tree *et,
					    uint32_t clusters)
{
	return et->et_ops->eo_update_clusters(et, clusters);
}

struct insert_ctxt {
	ocfs2_filesys *fs;
	struct ocfs2_extent_tree *et;
	struct ocfs2_extent_rec rec;
};
/*
 * Reset the actual path elements so that we can re-use the structure
 * to build another path. Generally, this involves freeing the buffer
 * heads.
 */
static void ocfs2_reinit_path(struct ocfs2_path *path, int keep_root)
{
	int i, start = 0, depth = 0;
	struct ocfs2_path_item *node;

	if (keep_root)
		start = 1;

	for(i = start; i < path_num_items(path); i++) {
		node = &path->p_node[i];
		if (!node->buf)
			continue;

		ocfs2_free(&node->buf);
		node->blkno = 0;
		node->buf = NULL;
		node->el = NULL;
	}

	/*
	 * Tree depth may change during truncate, or insert. If we're
	 * keeping the root extent list, then make sure that our path
	 * structure reflects the proper depth.
	 */
	if (keep_root)
		depth = path_root_el(path)->l_tree_depth;

	path->p_tree_depth = depth;
}

void ocfs2_free_path(struct ocfs2_path *path)
{
	/* We don't free the root because often in libocfs2 the root is a
	 * shared buffer such as the inode.  Caller must be responsible for
	 * handling the root of the path.
	 */
	if (path) {
		ocfs2_reinit_path(path, 1);
		ocfs2_free(&path);
	}
}

static enum ocfs2_contig_type
	ocfs2_extent_rec_contig(ocfs2_filesys *fs,
				struct ocfs2_extent_rec *ext,
				struct ocfs2_extent_rec *insert_rec);
static inline enum ocfs2_contig_type
	ocfs2_et_extent_contig(ocfs2_filesys *fs,
			       struct ocfs2_extent_tree *et,
			       struct ocfs2_extent_rec *rec,
			       struct ocfs2_extent_rec *insert_rec)
{
	if (et->et_ops->eo_extent_contig)
		return et->et_ops->eo_extent_contig(fs, et, rec, insert_rec);

	return ocfs2_extent_rec_contig(fs, rec, insert_rec);
}

/*
 * All the elements of src into dest. After this call, src could be freed
 * without affecting dest.
 *
 * Both paths should have the same root. Any non-root elements of dest
 * will be freed.
 */
static void ocfs2_cp_path(ocfs2_filesys *fs,
			  struct ocfs2_path *dest,
			  struct ocfs2_path *src)
{
	int i;
	struct ocfs2_extent_block *eb = NULL;

	assert(path_root_blkno(dest) == path_root_blkno(src));
	dest->p_tree_depth = src->p_tree_depth;

	for(i = 1; i < OCFS2_MAX_PATH_DEPTH; i++) {
		if (!src->p_node[i].buf) {
			if (dest->p_node[i].buf)
				ocfs2_free(dest->p_node[i].buf);
			dest->p_node[i].blkno = 0;
			dest->p_node[i].buf = NULL;
			dest->p_node[i].el = NULL;
			continue;
		}

		if (!dest->p_node[i].buf)
			ocfs2_malloc_block(fs->fs_io, &dest->p_node[i].buf);

		assert(dest->p_node[i].buf);
		memcpy(dest->p_node[i].buf, src->p_node[i].buf,
		       fs->fs_blocksize);
		eb = (struct ocfs2_extent_block *)dest->p_node[i].buf;
		dest->p_node[i].el = &eb->h_list;

		dest->p_node[i].blkno = src->p_node[i].blkno;
	}
}

/*
 * Make the *dest path the same as src and re-initialize src path to
 * have a root only.
 */
static void ocfs2_mv_path(struct ocfs2_path *dest, struct ocfs2_path *src)
{
	int i;

	assert(path_root_blkno(dest) == path_root_blkno(src));

	for(i = 1; i < OCFS2_MAX_PATH_DEPTH; i++) {
		ocfs2_free(&dest->p_node[i].buf);

		dest->p_node[i].blkno = src->p_node[i].blkno;
		dest->p_node[i].buf = src->p_node[i].buf;
		dest->p_node[i].el = src->p_node[i].el;

		src->p_node[i].blkno = 0;
		src->p_node[i].buf = NULL;
		src->p_node[i].el = NULL;
	}
}

/*
 * Insert an extent block at given index.
 *
 * Note:
 * This buf will be inserted into the path, so the caller shouldn't free it.
 */
static inline void ocfs2_path_insert_eb(struct ocfs2_path *path, int index,
					char *buf)
{
	struct ocfs2_extent_block *eb = (struct ocfs2_extent_block *) buf;
	/*
	 * Right now, no root buf is an extent block, so this helps
	 * catch code errors with dinode trees. The assertion can be
	 * safely removed if we ever need to insert extent block
	 * structures at the root.
	 */
	assert(index);

	path->p_node[index].blkno = eb->h_blkno;
	path->p_node[index].buf = (char *)buf;
	path->p_node[index].el = &eb->h_list;
}

static struct ocfs2_path *ocfs2_new_path(char *buf,
					 struct ocfs2_extent_list *root_el,
					 uint64_t blkno)
{
	struct ocfs2_path *path = NULL;

	assert(root_el->l_tree_depth < OCFS2_MAX_PATH_DEPTH);

	ocfs2_malloc0(sizeof(*path), &path);
	if (path) {
		path->p_tree_depth = root_el->l_tree_depth;
		path->p_node[0].blkno = blkno;
		path->p_node[0].buf = buf;
		path->p_node[0].el = root_el;
	}

	return path;
}

static struct ocfs2_path *ocfs2_new_path_from_path(struct ocfs2_path *path)
{
	return ocfs2_new_path(path_root_buf(path), path_root_el(path),
			      path_root_blkno(path));
}

struct ocfs2_path *ocfs2_new_path_from_et(struct ocfs2_extent_tree *et)
{
	return ocfs2_new_path(et->et_root_buf, et->et_root_el,
			      et->et_root_blkno);
}
/* Write all the extent block information to the disk.
 * We write all paths furthur down than subtree_index.
 * The caller will handle writing the sub_index.
 */
static errcode_t ocfs2_write_path_eb(ocfs2_filesys *fs,
				     struct ocfs2_path *path, int sub_index)
{
	errcode_t ret;
	int i;

	for (i = path->p_tree_depth; i > sub_index; i--) {
		ret = ocfs2_write_extent_block(fs,
					       path->p_node[i].blkno,
					       path->p_node[i].buf);
		if (ret)
			return ret;
	}

	return 0;
}

/* some extent blocks is modified and we need to synchronize them to the disk
 * accordingly.
 *
 * We will not update the inode if subtree_index is "0" since it should be
 * updated by the caller.
 *
 * left_path or right_path can be NULL, but they can't be NULL in the same time.
 * And if they are both not NULL, we will treat subtree_index in the right_path
 * as the right extent block information.
 */
static errcode_t ocfs2_sync_path_to_disk(ocfs2_filesys *fs,
					 struct ocfs2_path *left_path,
					 struct ocfs2_path *right_path,
					 int subtree_index)
{
	errcode_t ret = 0;
	struct ocfs2_path *path = NULL;

	assert(left_path || right_path);
	if (left_path) {
		ret = ocfs2_write_path_eb(fs, left_path, subtree_index);
		if (ret)
			goto bail;
	}

	if (right_path) {
		ret = ocfs2_write_path_eb(fs, right_path, subtree_index);
		if (ret)
			goto bail;
	}

	if (subtree_index) {
		/* subtree_index indicates an extent block. */
		path = right_path ? right_path : left_path;

		ret = ocfs2_write_extent_block(fs,
					path->p_node[subtree_index].blkno,
					path->p_node[subtree_index].buf);
		if (ret)
			goto bail;
	}
bail:
	return ret;
}

/*
 * Return the index of the extent record which contains cluster #v_cluster.
 * -1 is returned if it was not found.
 *
 * Should work fine on interior and exterior nodes.
 */
int ocfs2_search_extent_list(struct ocfs2_extent_list *el, uint32_t v_cluster)
{
	int ret = -1;
	int i;
	struct ocfs2_extent_rec *rec;
	uint32_t rec_end, rec_start, clusters;

	for(i = 0; i < el->l_next_free_rec; i++) {
		rec = &el->l_recs[i];

		rec_start = rec->e_cpos;
		clusters = ocfs2_rec_clusters(el->l_tree_depth, rec);

		rec_end = rec_start + clusters;

		if (v_cluster >= rec_start && v_cluster < rec_end) {
			ret = i;
			break;
		}
	}

	return ret;
}

/*
 * NOTE: ocfs2_block_extent_contig(), ocfs2_extents_adjacent() and
 * ocfs2_extent_rec_contig only work properly against leaf nodes!
 */
static inline int ocfs2_block_extent_contig(ocfs2_filesys *fs,
					    struct ocfs2_extent_rec *ext,
					    uint64_t blkno)
{
	uint64_t blk_end = ext->e_blkno;

	blk_end += ocfs2_clusters_to_blocks(fs, ext->e_leaf_clusters);

	return blkno == blk_end;
}

static inline int ocfs2_extents_adjacent(struct ocfs2_extent_rec *left,
					 struct ocfs2_extent_rec *right)
{
	uint32_t left_range;

	left_range = left->e_cpos + left->e_leaf_clusters;

	return (left_range == right->e_cpos);
}

static enum ocfs2_contig_type
	ocfs2_extent_rec_contig(ocfs2_filesys *fs,
				struct ocfs2_extent_rec *ext,
				struct ocfs2_extent_rec *insert_rec)
{
	uint64_t blkno = insert_rec->e_blkno;

	/*
	 * Refuse to coalesce extent records with different flag
	 * fields - we don't want to mix unwritten extents with user
	 * data.
	 */
	if (ext->e_flags != insert_rec->e_flags)
		return CONTIG_NONE;

	if (ocfs2_extents_adjacent(ext, insert_rec) &&
	    ocfs2_block_extent_contig(fs, ext, blkno))
			return CONTIG_RIGHT;

	blkno = ext->e_blkno;
	if (ocfs2_extents_adjacent(insert_rec, ext) &&
	    ocfs2_block_extent_contig(fs, insert_rec, blkno))
		return CONTIG_LEFT;

	return CONTIG_NONE;
}

/*
 * NOTE: We can have pretty much any combination of contiguousness and
 * appending.
 *
 * The usefulness of APPEND_TAIL is more in that it lets us know that
 * we'll have to update the path to that leaf.
 */
enum ocfs2_append_type {
	APPEND_NONE = 0,
	APPEND_TAIL,
};

enum ocfs2_split_type {
	SPLIT_NONE = 0,
	SPLIT_LEFT,
	SPLIT_RIGHT,
};

struct ocfs2_insert_type {
	enum ocfs2_split_type	ins_split;
	enum ocfs2_append_type	ins_appending;
	enum ocfs2_contig_type	ins_contig;
	int			ins_contig_index;
	int			ins_tree_depth;
};

struct ocfs2_merge_ctxt {
	enum ocfs2_contig_type	c_contig_type;
	int			c_has_empty_extent;
	int			c_split_covers_rec;
};

/*
 * Helper function for ocfs2_add_branch() and shift_tree_depth().
 *
 * Returns the sum of the rightmost extent rec logical offset and
 * cluster count.
 *
 * ocfs2_add_branch() uses this to determine what logical cluster
 * value should be populated into the leftmost new branch records.
 *
 * shift_tree_depth() uses this to determine the # clusters
 * value for the new topmost tree record.
 */
static inline uint32_t ocfs2_sum_rightmost_rec(struct ocfs2_extent_list  *el)
{
	uint16_t i = el->l_next_free_rec - 1;

	return el->l_recs[i].e_cpos +
		 ocfs2_rec_clusters(el->l_tree_depth, &el->l_recs[i]);

}

/*
 * Add an entire tree branch to our inode. eb_buf is the extent block
 * to start at, if we don't want to start the branch at the dinode
 * structure.
 *
 * last_eb_buf is required as we have to update it's next_leaf pointer
 * for the new last extent block.
 *
 * the new branch will be 'empty' in the sense that every block will
 * contain a single record with e_clusters == 0.
 */
static int ocfs2_add_branch(ocfs2_filesys *fs,
			    struct ocfs2_extent_tree *et,
			    char *eb_buf,
			    char **last_eb_buf)
{
	errcode_t ret;
	int new_blocks, i;
	uint64_t next_blkno, new_last_eb_blk;
	struct ocfs2_extent_block *eb;
	struct ocfs2_extent_list  *eb_el;
	struct ocfs2_extent_list  *el;
	uint32_t new_cpos;
	uint64_t *new_blknos = NULL;
	char	**new_eb_bufs = NULL;
	char *buf = NULL;

	assert(*last_eb_buf);

	if (eb_buf) {
		eb = (struct ocfs2_extent_block *) eb_buf;
		el = &eb->h_list;
	} else
		el = et->et_root_el;

	/* we never add a branch to a leaf. */
	assert(el->l_tree_depth);

	new_blocks = el->l_tree_depth;

	/* allocate the number of new eb blocks we need new_blocks should be
	 * allocated here.*/
	ret = ocfs2_malloc0(sizeof(uint64_t) * new_blocks, &new_blknos);
	if (ret)
		goto bail;
	memset(new_blknos, 0, sizeof(uint64_t) * new_blocks);

	ret = ocfs2_malloc0(sizeof(char *) * new_blocks, &new_eb_bufs);
	if (ret)
		goto bail;
	memset(new_eb_bufs, 0, sizeof(char *) * new_blocks);

	for (i = 0; i < new_blocks; i++) {
		ret = ocfs2_malloc_block(fs->fs_io, &buf);
		if (ret)
			return ret;
		new_eb_bufs[i] = buf;

		ret = ocfs2_new_extent_block(fs, &new_blknos[i]);
		if (ret)
			goto bail;

		ret = ocfs2_read_extent_block(fs, new_blknos[i], buf);
		if (ret)
			goto bail;
	}

	eb = (struct ocfs2_extent_block *)(*last_eb_buf);
	new_cpos = ocfs2_sum_rightmost_rec(&eb->h_list);

	/* Note: new_eb_bufs[new_blocks - 1] is the guy which will be
	 * linked with the rest of the tree.
	 * conversly, new_eb_bufs[0] is the new bottommost leaf.
	 *
	 * when we leave the loop, new_last_eb_blk will point to the
	 * newest leaf, and next_blkno will point to the topmost extent
	 * block.
	 */
	next_blkno = new_last_eb_blk = 0;
	for(i = 0; i < new_blocks; i++) {
		buf = new_eb_bufs[i];
		eb = (struct ocfs2_extent_block *) buf;
		eb_el = &eb->h_list;

		eb->h_next_leaf_blk = 0;
		eb_el->l_tree_depth = i;
		eb_el->l_next_free_rec = 1;
		memset(eb_el->l_recs, 0,
		       sizeof(struct ocfs2_extent_rec) * eb_el->l_count);
		/*
		 * This actually counts as an empty extent as
		 * c_clusters == 0
		 */
		eb_el->l_recs[0].e_cpos = new_cpos;
		eb_el->l_recs[0].e_blkno = next_blkno;
		/*
		 * eb_el isn't always an interior node, but even leaf
		 * nodes want a zero'd flags and reserved field so
		 * this gets the whole 32 bits regardless of use.
		 */
		eb_el->l_recs[0].e_int_clusters = 0;

		if (!eb_el->l_tree_depth)
			new_last_eb_blk = eb->h_blkno;

		next_blkno = eb->h_blkno;
	}

	/* Link the new branch into the rest of the tree (el will
	 * either be on the fe, or the extent block passed in.
	 */
	i = el->l_next_free_rec;
	el->l_recs[i].e_blkno = next_blkno;
	el->l_recs[i].e_cpos = new_cpos;
	el->l_recs[i].e_int_clusters = 0;
	el->l_next_free_rec++;

	/* fe needs a new last extent block pointer, as does the
	 * next_leaf on the previously last-extent-block.
	 */
	ocfs2_et_set_last_eb_blk(et, new_last_eb_blk);

	/* here all the extent block and the new inode information should be
	 * written back to the disk.
	 */
	for(i = 0; i < new_blocks; i++) {
		buf = new_eb_bufs[i];
		ret = ocfs2_write_extent_block(fs, new_blknos[i], buf);
		if (ret)
			goto bail;
	}

	/* update last_eb_buf's next_leaf pointer for
	 * the new last extent block.
	 */
	eb = (struct ocfs2_extent_block *)(*last_eb_buf);
	eb->h_next_leaf_blk = new_last_eb_blk;
	ret = ocfs2_write_extent_block(fs, eb->h_blkno, *last_eb_buf);
	if (ret)
		goto bail;

	if (eb_buf) {
		eb = (struct ocfs2_extent_block *)eb_buf;
		ret = ocfs2_write_extent_block(fs, eb->h_blkno, eb_buf);
		if (ret)
			goto bail;
	}

	/*
	 * Some callers want to track the rightmost leaf so pass it
	 * back here.
	 */
	memcpy(*last_eb_buf, new_eb_bufs[0], fs->fs_blocksize);

	/* The inode information isn't updated since we use duplicated extent
	 * block in the insertion and it may fail in other steps.
	 */
	ret = 0;
bail:
	if (new_eb_bufs) {
		for (i = 0; i < new_blocks; i++)
			if (new_eb_bufs[i])
				ocfs2_free(&new_eb_bufs[i]);
		ocfs2_free(&new_eb_bufs);
	}

	if (ret && new_blknos)
		for (i = 0; i < new_blocks; i++)
			if (new_blknos[i])
				ocfs2_delete_extent_block(fs, new_blknos[i]);

	if (new_blknos)
		ocfs2_free(&new_blknos);

	return ret;
}

/*
 * Should only be called when there is no space left in any of the
 * leaf nodes. What we want to do is find the lowest tree depth
 * non-leaf extent block with room for new records. There are three
 * valid results of this search:
 *
 * 1) a lowest extent block is found, then we pass it back in
 *    *target_buf and return '0'
 *
 * 2) the search fails to find anything, but the dinode has room. We
 *    pass NULL back in *target_buf, but still return '0'
 *
 * 3) the search fails to find anything AND the dinode is full, in
 *    which case we return > 0
 *
 * return status < 0 indicates an error.
 */
static errcode_t ocfs2_find_branch_target(ocfs2_filesys *fs,
					  struct ocfs2_extent_tree *et,
					  char **target_buf)
{
	errcode_t ret = 0;
	int i;
	uint64_t blkno;
	struct ocfs2_extent_block *eb;
	char *buf = NULL, *lowest_buf = NULL;
	struct ocfs2_extent_list *el = et->et_root_el;

	*target_buf = NULL;

	ret = ocfs2_malloc_block(fs->fs_io, &buf);
	if (ret)
		return ret;

	while(el->l_tree_depth > 1) {
		if (el->l_next_free_rec == 0) {
			ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
			goto bail;
		}
		i = el->l_next_free_rec - 1;
		blkno = el->l_recs[i].e_blkno;
		if (!blkno) {
			ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
			goto bail;
		}

		ret = ocfs2_read_extent_block(fs, blkno, buf);
		if (ret)
			goto bail;

		eb = (struct ocfs2_extent_block *) buf;
		el = &eb->h_list;

		if (el->l_next_free_rec < el->l_count)
			lowest_buf = buf;
	}

	el = et->et_root_el;
	/* If we didn't find one and the fe doesn't have any room,
	 * then return '1' */
	if (!lowest_buf && el->l_next_free_rec == el->l_count)
		ret = 1;

	*target_buf = lowest_buf;
bail:
	if (buf && !*target_buf)
		ocfs2_free(&buf);

	return ret;
}

/*
 * This function will discard the rightmost extent record.
 */
static void ocfs2_shift_records_right(struct ocfs2_extent_list *el)
{
	int next_free = el->l_next_free_rec;
	int count = el->l_count;
	unsigned int num_bytes;

	assert(next_free);
	/* This will cause us to go off the end of our extent list. */
	assert(next_free < count);

	num_bytes = sizeof(struct ocfs2_extent_rec) * next_free;

	memmove(&el->l_recs[1], &el->l_recs[0], num_bytes);
}

static void ocfs2_rotate_leaf(struct ocfs2_extent_list *el,
			      struct ocfs2_extent_rec *insert_rec)
{
	int i, insert_index, next_free, has_empty, num_bytes;
	uint32_t insert_cpos = insert_rec->e_cpos;
	struct ocfs2_extent_rec *rec;

	next_free = el->l_next_free_rec;
	has_empty = ocfs2_is_empty_extent(&el->l_recs[0]);

	assert(next_free);

	/* The tree code before us didn't allow enough room in the leaf. */
	if (el->l_next_free_rec == el->l_count && !has_empty)
		assert(0);

	/*
	 * The easiest way to approach this is to just remove the
	 * empty extent and temporarily decrement next_free.
	 */
	if (has_empty) {
		/*
		 * If next_free was 1 (only an empty extent), this
		 * loop won't execute, which is fine. We still want
		 * the decrement above to happen.
		 */
		for(i = 0; i < (next_free - 1); i++)
			el->l_recs[i] = el->l_recs[i+1];

		next_free--;
	}

	/* Figure out what the new record index should be. */
	for(i = 0; i < next_free; i++) {
		rec = &el->l_recs[i];

		if (insert_cpos < rec->e_cpos)
			break;
	}
	insert_index = i;

	assert(insert_index >= 0);
	assert(insert_index < el->l_count);
	assert(insert_index <= next_free);

	/* No need to memmove if we're just adding to the tail. */
	if (insert_index != next_free) {
		assert(next_free < el->l_count);

		num_bytes = next_free - insert_index;
		num_bytes *= sizeof(struct ocfs2_extent_rec);
		memmove(&el->l_recs[insert_index + 1],
			&el->l_recs[insert_index],
			num_bytes);
	}

	/*
	 * Either we had an empty extent, and need to re-increment or
	 * there was no empty extent on a non full rightmost leaf node,
	 * in which case we still need to increment.
	 */
	next_free++;
	el->l_next_free_rec = next_free;
	/* Make sure none of the math above just messed up our tree. */
	assert(el->l_next_free_rec <= el->l_count);

	el->l_recs[insert_index] = *insert_rec;
}

static void ocfs2_remove_empty_extent(struct ocfs2_extent_list *el)
{
	int size, num_recs = el->l_next_free_rec;

	assert(num_recs);

	if (ocfs2_is_empty_extent(&el->l_recs[0])) {
		num_recs--;
		size = num_recs * sizeof(struct ocfs2_extent_rec);
		memmove(&el->l_recs[0], &el->l_recs[1], size);
		memset(&el->l_recs[num_recs], 0,
		       sizeof(struct ocfs2_extent_rec));
		el->l_next_free_rec = num_recs;
	}
}

/*
 * Create an empty extent record .
 *
 * l_next_free_rec may be updated.
 *
 * If an empty extent already exists do nothing.
 */
static void ocfs2_create_empty_extent(struct ocfs2_extent_list *el)
{
	int next_free = el->l_next_free_rec;

	assert(el->l_tree_depth == 0);

	if (next_free == 0)
		goto set_and_inc;

	if (ocfs2_is_empty_extent(&el->l_recs[0]))
		return;

	ocfs2_shift_records_right(el);

set_and_inc:
	el->l_next_free_rec += 1;
	memset(&el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));
}

/*
 * For a rotation which involves two leaf nodes, the "root node" is
 * the lowest level tree node which contains a path to both leafs. This
 * resulting set of information can be used to form a complete "subtree"
 *
 * This function is passed two full paths from the dinode down to a
 * pair of adjacent leaves. It's task is to figure out which path
 * index contains the subtree root - this can be the root index itself
 * in a worst-case rotation.
 *
 * The array index of the subtree root is passed back.
 */
static int ocfs2_find_subtree_root(struct ocfs2_path *left,
				   struct ocfs2_path *right)
{
	int i = 0;

	/* Check that the caller passed in two paths from the same tree. */
	assert(path_root_blkno(left) == path_root_blkno(right));

	do {
		i++;

		/* The caller didn't pass two adjacent paths. */
 		if (i > left->p_tree_depth)
			assert(0);
	} while (left->p_node[i].blkno == right->p_node[i].blkno);

	return i - 1;
}

typedef errcode_t (path_insert_t)(void *, char *);

/*
 * Traverse a btree path in search of cpos, starting at root_el.
 *
 * This code can be called with a cpos larger than the tree, in which
 * case it will return the rightmost path.
 */
static errcode_t __ocfs2_find_path(ocfs2_filesys *fs,
				   struct ocfs2_extent_list *root_el,
				   uint32_t cpos,
				   path_insert_t *func,
				   void *data)
{
	int i, ret = 0;
	uint32_t range;
	uint64_t blkno;
	char *buf = NULL;
	struct ocfs2_extent_block *eb;
	struct ocfs2_extent_list *el;
	struct ocfs2_extent_rec *rec;

	el = root_el;
	while (el->l_tree_depth) {
		if (el->l_next_free_rec == 0) {
			ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
			goto out;

		}


		for(i = 0; i < el->l_next_free_rec - 1; i++) {
			rec = &el->l_recs[i];

			/*
			 * In the case that cpos is off the allocation
			 * tree, this should just wind up returning the
			 * rightmost record.
			 */
			range = rec->e_cpos +
				ocfs2_rec_clusters(el->l_tree_depth, rec);
			if (cpos >= rec->e_cpos && cpos < range)
			    break;
		}

		blkno = el->l_recs[i].e_blkno;
		if (blkno == 0) {
			ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
			goto out;
		}

		ret = ocfs2_malloc_block(fs->fs_io, &buf);
		if (ret)
			return ret;

		ret = ocfs2_read_extent_block(fs, blkno, buf);
		if (ret)
			goto out;

		eb = (struct ocfs2_extent_block *) buf;
		el = &eb->h_list;

		if (el->l_next_free_rec > el->l_count) {
			ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
			goto out;
		}

		/* The user's callback must give us the tip for how to
		 * handle the buf we allocated by return values.
		 *
 		 * 1) return '0':
		 *    the function succeeds,and it will use the buf and
		 *    take care of the buffer release.
		 *
 		 * 2) return > 0:
		 *    the function succeeds, and there is no need for buf,
		 *    so we will release it.
		 *
		 * 3) return < 0:
		 *    the function fails.
		 */
		if (func) {
			ret = func(data, buf);

			if (ret == 0) {
				buf = NULL;
				continue;
			}
			else if (ret < 0)
				goto out;
		}
		ocfs2_free(&buf);
		buf = NULL;
	}

out:
	/* Catch any trailing buf that the loop didn't handle. */
	if (buf)
		ocfs2_free(&buf);

	return ret;
}

/*
 * Given an initialized path (that is, it has a valid root extent
 * list), this function will traverse the btree in search of the path
 * which would contain cpos.
 *
 * The path traveled is recorded in the path structure.
 *
 * Note that this will not do any comparisons on leaf node extent
 * records, so it will work fine in the case that we just added a tree
 * branch.
 */
struct find_path_data {
	int index;
	struct ocfs2_path *path;
};

static errcode_t find_path_ins(void *data, char *eb)
{
	struct find_path_data *fp = data;

	ocfs2_path_insert_eb(fp->path, fp->index, eb);
	fp->index++;

	return 0;
}

int ocfs2_find_path(ocfs2_filesys *fs, struct ocfs2_path *path,
		    uint32_t cpos)
{
	struct find_path_data data;

	data.index = 1;
	data.path = path;
	return __ocfs2_find_path(fs, path_root_el(path), cpos,
				 find_path_ins, &data);
}

/*
 * Find the leaf block in the tree which would contain cpos. No
 * checking of the actual leaf is done.
 *
 * This function doesn't handle non btree extent lists.
 */
int ocfs2_tree_find_leaf(ocfs2_filesys *fs, struct ocfs2_extent_list *el,
			 uint64_t el_blkno, char *el_blk,
			 uint32_t cpos, char **leaf_buf)
{
	int ret;
	char *buf = NULL;
	struct ocfs2_path *path = NULL;

	assert(el->l_tree_depth > 0);

	path = ocfs2_new_path(el_blk, el, el_blkno);
	if (!path) {
		ret = OCFS2_ET_NO_MEMORY;
		goto out;
	}

	ret = ocfs2_find_path(fs, path, cpos);
	if (ret)
		goto out;

	ret = ocfs2_malloc_block(fs->fs_io, &buf);
	if (ret)
		goto out;

	memcpy(buf, path_leaf_buf(path), fs->fs_blocksize);
	*leaf_buf = buf;
out:
	ocfs2_free_path(path);
	return ret;
}

int ocfs2_find_leaf(ocfs2_filesys *fs, struct ocfs2_dinode *di,
		    uint32_t cpos, char **leaf_buf)
{
	return ocfs2_tree_find_leaf(fs, &di->id2.i_list, di->i_blkno,
				    (char *)di, cpos, leaf_buf);
}

/*
 * Adjust the adjacent records (left_rec, right_rec) involved in a rotation.
 *
 * Basically, we've moved stuff around at the bottom of the tree and
 * we need to fix up the extent records above the changes to reflect
 * the new changes.
 *
 * left_rec: the record on the left.
 * left_child_el: is the child list pointed to by left_rec
 * right_rec: the record to the right of left_rec
 * right_child_el: is the child list pointed to by right_rec
 *
 * By definition, this only works on interior nodes.
 */
static void ocfs2_adjust_adjacent_records(struct ocfs2_extent_rec *left_rec,
				    struct ocfs2_extent_list *left_child_el,
				    struct ocfs2_extent_rec *right_rec,
				    struct ocfs2_extent_list *right_child_el)
{
	uint32_t left_clusters, right_end;

	/*
	 * Interior nodes never have holes. Their cpos is the cpos of
	 * the leftmost record in their child list. Their cluster
	 * count covers the full theoretical range of their child list
	 * - the range between their cpos and the cpos of the record
	 * immediately to their right.
	 */
	left_clusters = right_child_el->l_recs[0].e_cpos;
	if (ocfs2_is_empty_extent(&right_child_el->l_recs[0])) {
		assert(right_child_el->l_next_free_rec > 1);
		left_clusters = right_child_el->l_recs[1].e_cpos;
	}
	left_clusters -= left_rec->e_cpos;
	left_rec->e_int_clusters = left_clusters;

	/*
	 * Calculate the rightmost cluster count boundary before
	 * moving cpos - we will need to adjust clusters after
	 * updating e_cpos to keep the same highest cluster count.
	 */
	right_end = right_rec->e_cpos;
	right_end += right_rec->e_int_clusters;

	right_rec->e_cpos = left_rec->e_cpos;
	right_rec->e_cpos += left_clusters;

	right_end -= right_rec->e_cpos;
	right_rec->e_int_clusters = right_end;
}

/*
 * Adjust the adjacent root node records involved in a
 * rotation. left_el_blkno is passed in as a key so that we can easily
 * find it's index in the root list.
 */
static void ocfs2_adjust_root_records(struct ocfs2_extent_list *root_el,
				      struct ocfs2_extent_list *left_el,
				      struct ocfs2_extent_list *right_el,
				      uint64_t left_el_blkno)
{
	int i;

	assert(root_el->l_tree_depth > left_el->l_tree_depth);

	for(i = 0; i < root_el->l_next_free_rec - 1; i++) {
		if (root_el->l_recs[i].e_blkno == left_el_blkno)
			break;
	}

	/*
	 * The path walking code should have never returned a root and
	 * two paths which are not adjacent.
	 */
	assert(i < (root_el->l_next_free_rec - 1));

	ocfs2_adjust_adjacent_records(&root_el->l_recs[i], left_el,
				      &root_el->l_recs[i + 1], right_el);
}

/*
 * We've changed a leaf block (in right_path) and need to reflect that
 * change back up the subtree.
 *
 * This happens in multiple places:
 *   - When we've moved an extent record from the left path leaf to the right
 *     path leaf to make room for an empty extent in the left path leaf.
 *   - When our insert into the right path leaf is at the leftmost edge
 *     and requires an update of the path immediately to it's left. This
 *     can occur at the end of some types of rotation and appending inserts.
 */
static void ocfs2_complete_edge_insert(ocfs2_filesys *fs,
				       struct ocfs2_path *left_path,
				       struct ocfs2_path *right_path,
				       int subtree_index)
{
	int i, idx;
	uint64_t blkno;
	struct ocfs2_extent_list *el, *left_el, *right_el;
	struct ocfs2_extent_rec *left_rec, *right_rec;

	/*
	 * Update the counts and position values within all the
	 * interior nodes to reflect the leaf rotation we just did.
	 *
	 * The root node is handled below the loop.
	 *
	 * We begin the loop with right_el and left_el pointing to the
	 * leaf lists and work our way up.
	 *
	 * NOTE: within this loop, left_el and right_el always refer
	 * to the *child* lists.
	 */
	left_el = path_leaf_el(left_path);
	right_el = path_leaf_el(right_path);
	for(i = left_path->p_tree_depth - 1; i > subtree_index; i--) {

		/*
		 * One nice property of knowing that all of these
		 * nodes are below the root is that we only deal with
		 * the leftmost right node record and the rightmost
		 * left node record.
		 */
		el = left_path->p_node[i].el;
		idx = left_el->l_next_free_rec - 1;
		left_rec = &el->l_recs[idx];

		el = right_path->p_node[i].el;
		right_rec = &el->l_recs[0];

		ocfs2_adjust_adjacent_records(left_rec, left_el, right_rec,
					      right_el);

		/*
		 * Setup our list pointers now so that the current
		 * parents become children in the next iteration.
		 */
		left_el = left_path->p_node[i].el;
		right_el = right_path->p_node[i].el;
	}

	/*
	 * At the root node, adjust the two adjacent records which
	 * begin our path to the leaves.
	 */

	el = left_path->p_node[subtree_index].el;
	left_el = left_path->p_node[subtree_index + 1].el;
	right_el = right_path->p_node[subtree_index + 1].el;
	blkno = left_path->p_node[subtree_index + 1].blkno;

	ocfs2_adjust_root_records(el, left_el, right_el, blkno);

	/* ocfs2_adjust_root_records only update the extent block in the left
	 * path, and actually right_path->p_node[subtree_index].eb indicates the
	 * same extent block, so we must keep them the same content.
	 */
	memcpy(right_path->p_node[subtree_index].buf,
	       left_path->p_node[subtree_index].buf, fs->fs_blocksize);
}

/* Rotate the subtree to right.
 *
 * Note: After successful rotation, the extent block will be flashed
 * to disk accordingly.
 */
static errcode_t ocfs2_rotate_subtree_right(ocfs2_filesys *fs,
					    struct ocfs2_path *left_path,
					    struct ocfs2_path *right_path,
					    int subtree_index)
{
	errcode_t ret;
	int i;
	struct ocfs2_extent_list *right_el, *left_el;
	struct ocfs2_extent_rec move_rec;

	left_el = path_leaf_el(left_path);

	if (left_el->l_next_free_rec != left_el->l_count)
		return OCFS2_ET_CORRUPT_EXTENT_BLOCK;

	/*
	 * This extent block may already have an empty record, so we
	 * return early if so.
	 */
	if (ocfs2_is_empty_extent(&left_el->l_recs[0]))
		return 0;

	assert(left_path->p_node[subtree_index].blkno ==
	       right_path->p_node[subtree_index].blkno);

	right_el = path_leaf_el(right_path);

	ocfs2_create_empty_extent(right_el);

	/* Do the copy now. */
	i = left_el->l_next_free_rec - 1;
	move_rec = left_el->l_recs[i];
	right_el->l_recs[0] = move_rec;

	/*
	 * Clear out the record we just copied and shift everything
	 * over, leaving an empty extent in the left leaf.
	 *
	 * We temporarily subtract from next_free_rec so that the
	 * shift will lose the tail record (which is now defunct).
	 */
	left_el->l_next_free_rec -= 1;
	ocfs2_shift_records_right(left_el);
	memset(&left_el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));
	left_el->l_next_free_rec += 1;

	ocfs2_complete_edge_insert(fs, left_path, right_path, subtree_index);

	ret = ocfs2_sync_path_to_disk(fs, left_path, right_path, subtree_index);

	return ret;
}

/*
 * Given a full path, determine what cpos value would return us a path
 * containing the leaf immediately to the left of the current one.
 *
 * Will return zero if the path passed in is already the leftmost path.
 */
static int ocfs2_find_cpos_for_left_leaf(struct ocfs2_path *path,
					 uint32_t *cpos)
{
	int i, j, ret = 0;
	uint64_t blkno;
	struct ocfs2_extent_list *el;

	assert(path->p_tree_depth > 0);

	*cpos = 0;

	blkno = path_leaf_blkno(path);

	/* Start at the tree node just above the leaf and work our way up. */
	i = path->p_tree_depth - 1;
	while (i >= 0) {
		el = path->p_node[i].el;

		/* Find the extent record just before the one in our path. */
		for(j = 0; j < el->l_next_free_rec; j++) {
			if (el->l_recs[j].e_blkno == blkno) {
				if (j == 0) {
					if (i == 0) {
						/*
						 * We've determined that the
						 * path specified is already
						 * the leftmost one - return a
						 * cpos of zero.
						 */
						goto out;
					}
					/*
					 * The leftmost record points to our
					 * leaf - we need to travel up the
					 * tree one level.
					 */
					goto next_node;
				}

				*cpos = el->l_recs[j - 1].e_cpos;
				*cpos = *cpos + ocfs2_rec_clusters(
							el->l_tree_depth,
							&el->l_recs[j - 1]);
				*cpos = *cpos - 1;
				goto out;
			}
		}

		/*
		 * If we got here, we never found a valid node where
		 * the tree indicated one should be.
		 */
		ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
		goto out;

next_node:
		blkno = path->p_node[i].blkno;
		i--;
	}

out:
	return ret;
}

/*
 * Trap the case where we're inserting into the theoretical range past
 * the _actual_ left leaf range. Otherwise, we'll rotate a record
 * whose cpos is less than ours into the right leaf.
 *
 * It's only necessary to look at the rightmost record of the left
 * leaf because the logic that calls us should ensure that the
 * theoretical ranges in the path components above the leaves are
 * correct.
 */
static int ocfs2_rotate_requires_path_adjustment(struct ocfs2_path *left_path,
						 uint32_t insert_cpos)
{
	struct ocfs2_extent_list *left_el;
	struct ocfs2_extent_rec *rec;
	int next_free;

	left_el = path_leaf_el(left_path);
	next_free = left_el->l_next_free_rec;
	rec = &left_el->l_recs[next_free - 1];

	if (insert_cpos > rec->e_cpos)
		return 1;
	return 0;
}

static int ocfs2_leftmost_rec_contains(struct ocfs2_extent_list *el,
				       uint32_t cpos)
{
	int next_free = el->l_next_free_rec;
	unsigned int range;
	struct ocfs2_extent_rec *rec;

	if (next_free == 0)
		return 0;

	rec = &el->l_recs[0];
	if (ocfs2_is_empty_extent(rec)) {
		/* Empty list. */
		if (next_free == 1)
			return 0;
		rec = &el->l_recs[1];
	}

	range = rec->e_cpos + ocfs2_rec_clusters(el->l_tree_depth, rec);
	if (cpos >= rec->e_cpos && cpos < range)
		return 1;
	return 0;
}

/*
 * Rotate all the records in a btree right one record, starting at insert_cpos.
 *
 * The path to the rightmost leaf should be passed in.
 *
 * The array is assumed to be large enough to hold an entire path (tree depth).
 *
 * Upon succesful return from this function:
 *
 * - The 'right_path' array will contain a path to the leaf block
 *   whose range contains e_cpos.
 * - That leaf block will have a single empty extent in list index 0.
 * - In the case that the rotation requires a post-insert update,
 *   *ret_left_path will contain a valid path which can be passed to
 *   ocfs2_insert_path().
 */
static int ocfs2_rotate_tree_right(ocfs2_filesys *fs,
				   enum ocfs2_split_type split,
				   uint32_t insert_cpos,
				   struct ocfs2_path *right_path,
				   struct ocfs2_path **ret_left_path)
{
	int ret, start;
	uint32_t cpos;
	struct ocfs2_path *left_path = NULL;

	*ret_left_path = NULL;

	left_path = ocfs2_new_path_from_path(right_path);
	if (!left_path) {
		ret = OCFS2_ET_NO_MEMORY;
		goto out;
	}

	ret = ocfs2_find_cpos_for_left_leaf(right_path, &cpos);
	if (ret)
		goto out;

	/*
	 * What we want to do here is:
	 *
	 * 1) Start with the rightmost path.
	 *
	 * 2) Determine a path to the leaf block directly to the left
         *    of that leaf.
	 *
	 * 3) Determine the 'subtree root' - the lowest level tree node
	 *    which contains a path to both leaves.
	 *
	 * 4) Rotate the subtree.
	 *
	 * 5) Find the next subtree by considering the left path to be
         *    the new right path.
	 *
	 * The check at the top of this while loop also accepts
	 * insert_cpos == cpos because cpos is only a _theoretical_
	 * value to get us the left path - insert_cpos might very well
	 * be filling that hole.
	 *
	 * Stop at a cpos of '0' because we either started at the
	 * leftmost branch (i.e., a tree with one branch and a
	 * rotation inside of it), or we've gone as far as we can in
	 * rotating subtrees.
	 */
	while (cpos && insert_cpos <= cpos) {

		ret = ocfs2_find_path(fs, left_path, cpos);
		if (ret)
			goto out;

		if (path_leaf_blkno(left_path) == path_leaf_blkno(right_path))
			assert(0);

		if (split == SPLIT_NONE &&
		    ocfs2_rotate_requires_path_adjustment(left_path,
							  insert_cpos)) {
			/*
			 * We've rotated the tree as much as we
			 * should. The rest is up to
			 * ocfs2_insert_path() to complete, after the
			 * record insertion. We indicate this
			 * situation by returning the left path.
			 *
			 * The reason we don't adjust the records here
			 * before the record insert is that an error
			 * later might break the rule where a parent
			 * record e_cpos will reflect the actual
			 * e_cpos of the 1st nonempty record of the
			 * child list.
			 */
			*ret_left_path = left_path;
			goto out_ret_path;
		}

		start = ocfs2_find_subtree_root(left_path, right_path);

		ret = ocfs2_rotate_subtree_right(fs, left_path, right_path,
						 start);
		if (ret)
			goto out;

		if (split != SPLIT_NONE &&
		    ocfs2_leftmost_rec_contains(path_leaf_el(right_path),
						insert_cpos)) {
			/*
			 * A rotate moves the rightmost left leaf
			 * record over to the leftmost right leaf
			 * slot. If we're doing an extent split
			 * instead of a real insert, then we have to
			 * check that the extent to be split wasn't
			 * just moved over. If it was, then we can
			 * exit here, passing left_path back -
			 * ocfs2_split_extent() is smart enough to
			 * search both leaves.
			 */
			*ret_left_path = left_path;
			goto out_ret_path;
		}
		/*
		 * There is no need to re-read the next right path
		 * as we know that it'll be our current left
		 * path. Optimize by copying values instead.
		 */
		ocfs2_mv_path(right_path, left_path);

		ret = ocfs2_find_cpos_for_left_leaf(right_path, &cpos);
		if (ret)
			goto out;
	}

out:
	ocfs2_free_path(left_path);

out_ret_path:
	return ret;
}

static void ocfs2_update_edge_lengths(struct ocfs2_path *path)
{
	int i, idx;
	struct ocfs2_extent_rec *rec;
	struct ocfs2_extent_list *el;
	struct ocfs2_extent_block *eb;
	uint32_t range;

	/* Path should always be rightmost. */
	eb = (struct ocfs2_extent_block *)path_leaf_buf(path);
	assert(eb->h_next_leaf_blk == 0ULL);

	el = &eb->h_list;
	assert(el->l_next_free_rec > 0);
	idx = el->l_next_free_rec - 1;
	rec = &el->l_recs[idx];
	range = rec->e_cpos + ocfs2_rec_clusters(el->l_tree_depth, rec);

	for (i = 0; i < path->p_tree_depth; i++) {
		el = path->p_node[i].el;
		idx = el->l_next_free_rec - 1;
		rec = &el->l_recs[idx];

		rec->e_int_clusters = range;
		rec->e_int_clusters -= rec->e_cpos;
	}
}

static errcode_t ocfs2_unlink_path(ocfs2_filesys *fs,
				   struct ocfs2_path *path, int unlink_start)
{
	int ret, i;
	struct ocfs2_extent_block *eb;
	struct ocfs2_extent_list *el;
	char *buf;

	for(i = unlink_start; i < path_num_items(path); i++) {
		buf = path->p_node[i].buf;

		eb = (struct ocfs2_extent_block *)buf;
		/*
		 * Not all nodes might have had their final count
		 * decremented by the caller - handle this here.
		 */
		el = &eb->h_list;
		assert(el->l_next_free_rec <= 1);

		el->l_next_free_rec = 0;
		memset(&el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));
		ret = ocfs2_delete_extent_block(fs, path->p_node[i].blkno);
		if (ret)
			return ret;
	}
	return 0;
}

/*
 * ocfs2_unlink_subtree will delete extent blocks in the "right_path"
 * from "subtree_index".
 */
static errcode_t ocfs2_unlink_subtree(ocfs2_filesys *fs,
				      struct ocfs2_path *left_path,
				      struct ocfs2_path *right_path,
				      int subtree_index)
{
	errcode_t ret;
	int i;
	struct ocfs2_extent_list *root_el = left_path->p_node[subtree_index].el;
	struct ocfs2_extent_block *eb;

	eb = (struct ocfs2_extent_block *)right_path->p_node[subtree_index + 1].buf;

	for(i = 1; i < root_el->l_next_free_rec; i++)
		if (root_el->l_recs[i].e_blkno == eb->h_blkno)
			break;

	assert(i < root_el->l_next_free_rec);

	memset(&root_el->l_recs[i], 0, sizeof(struct ocfs2_extent_rec));
	root_el->l_next_free_rec -= 1;

	eb = (struct ocfs2_extent_block *)path_leaf_buf(left_path);
	eb->h_next_leaf_blk = 0;

	ret = ocfs2_unlink_path(fs, right_path, subtree_index + 1);
	if (ret)
		return ret;

	return 0;
}

static int ocfs2_rotate_subtree_left(ocfs2_filesys *fs,
				     struct ocfs2_extent_tree *et,
				     struct ocfs2_path *left_path,
				     struct ocfs2_path *right_path,
				     int subtree_index,
				     int *deleted)
{
	errcode_t ret;
	int i, del_right_subtree = 0, right_has_empty = 0;
	struct ocfs2_extent_list *right_leaf_el, *left_leaf_el;
	struct ocfs2_extent_block *eb;

	*deleted = 0;

	right_leaf_el = path_leaf_el(right_path);
	left_leaf_el = path_leaf_el(left_path);
	assert(left_path->p_node[subtree_index].blkno ==
	       right_path->p_node[subtree_index].blkno);

	if (!ocfs2_is_empty_extent(&left_leaf_el->l_recs[0]))
		return 0;

	eb = (struct ocfs2_extent_block *)path_leaf_buf(right_path);
	if (ocfs2_is_empty_extent(&right_leaf_el->l_recs[0])) {
		/*
		 * It's legal for us to proceed if the right leaf is
		 * the rightmost one and it has an empty extent. There
		 * are two cases to handle - whether the leaf will be
		 * empty after removal or not. If the leaf isn't empty
		 * then just remove the empty extent up front. The
		 * next block will handle empty leaves by flagging
		 * them for unlink.
		 *
		 * Non rightmost leaves will throw EAGAIN and the
		 * caller can manually move the subtree and retry.
		 */

		if (eb->h_next_leaf_blk != 0ULL)
			return EAGAIN;

		if (right_leaf_el->l_next_free_rec > 1) {
			ocfs2_remove_empty_extent(right_leaf_el);
		} else
			right_has_empty = 1;
	}

	if (eb->h_next_leaf_blk == 0ULL &&
	    right_leaf_el->l_next_free_rec == 1) {
		/*
		 * We have to update i_last_eb_blk during the meta
		 * data delete.
		 */
		del_right_subtree = 1;
	}

	/*
	 * Getting here with an empty extent in the right path implies
	 * that it's the rightmost path and will be deleted.
	 */
	assert(!right_has_empty || del_right_subtree);

	if (!right_has_empty) {
		/*
		 * Only do this if we're moving a real
		 * record. Otherwise, the action is delayed until
		 * after removal of the right path in which case we
		 * can do a simple shift to remove the empty extent.
		 */
		ocfs2_rotate_leaf(left_leaf_el, &right_leaf_el->l_recs[0]);
		memset(&right_leaf_el->l_recs[0], 0,
		       sizeof(struct ocfs2_extent_rec));
	}
	if (eb->h_next_leaf_blk == 0ULL) {
		/*
		 * Move recs over to get rid of empty extent, decrease
		 * next_free. This is allowed to remove the last
		 * extent in our leaf (setting l_next_free_rec to
		 * zero) - the delete code below won't care.
		 */
		ocfs2_remove_empty_extent(right_leaf_el);
	}

	if (del_right_subtree) {
		ocfs2_unlink_subtree(fs, left_path, right_path, subtree_index);
		ocfs2_update_edge_lengths(left_path);

		/*
		 * Now the good extent block information is stored in left_path, so
		 * synchronize the right path with it.
		 */
		for (i = 0; i <= subtree_index; i++)
			memcpy(right_path->p_node[i].buf,
			       left_path->p_node[i].buf,
			       fs->fs_blocksize);

		eb = (struct ocfs2_extent_block *)path_leaf_buf(left_path);
		ocfs2_et_set_last_eb_blk(et, eb->h_blkno);

		/*
		 * Removal of the extent in the left leaf was skipped
		 * above so we could delete the right path
		 * 1st.
		 */
		if (right_has_empty)
			ocfs2_remove_empty_extent(left_leaf_el);

		*deleted = 1;

		/*
		 * The extent block in the right path belwo subtree_index
		 * have been deleted, so we don't need to synchronize
		 * them to the disk.
		 */
		ret = ocfs2_sync_path_to_disk(fs, left_path, NULL,
					      subtree_index);
	} else {
		ocfs2_complete_edge_insert(fs, left_path, right_path,
					   subtree_index);

		ret = ocfs2_sync_path_to_disk(fs, left_path, right_path,
					      subtree_index);
	}

	return ret;
}

/*
 * Given a full path, determine what cpos value would return us a path
 * containing the leaf immediately to the right of the current one.
 *
 * Will return zero if the path passed in is already the rightmost path.
 *
 * This looks similar, but is subtly different to
 * ocfs2_find_cpos_for_left_leaf().
 */
static int ocfs2_find_cpos_for_right_leaf(ocfs2_filesys *fs,
					  struct ocfs2_path *path,
					  uint32_t *cpos)
{
	int i, j, ret = 0;
	uint64_t blkno;
	struct ocfs2_extent_list *el;

	*cpos = 0;

	if (path->p_tree_depth == 0)
		return 0;

	blkno = path_leaf_blkno(path);

	/* Start at the tree node just above the leaf and work our way up. */
	i = path->p_tree_depth - 1;
	while (i >= 0) {
		int next_free;

		el = path->p_node[i].el;

		/*
		 * Find the extent record just after the one in our
		 * path.
		 */
		next_free = el->l_next_free_rec;
		for(j = 0; j < el->l_next_free_rec; j++) {
			if (el->l_recs[j].e_blkno == blkno) {
				if (j == (next_free - 1)) {
					if (i == 0) {
						/*
						 * We've determined that the
						 * path specified is already
						 * the rightmost one - return a
						 * cpos of zero.
						 */
						goto out;
					}
					/*
					 * The rightmost record points to our
					 * leaf - we need to travel up the
					 * tree one level.
					 */
					goto next_node;
				}

				*cpos = el->l_recs[j + 1].e_cpos;
				goto out;
			}
		}

		/*
		 * If we got here, we never found a valid node where
		 * the tree indicated one should be.
		 */
		ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
		goto out;

next_node:
		blkno = path->p_node[i].blkno;
		i--;
	}

out:
	return ret;
}

static void ocfs2_rotate_rightmost_leaf_left(ocfs2_filesys *fs,
					    struct ocfs2_extent_list *el)
{
	if (!ocfs2_is_empty_extent(&el->l_recs[0]))
		return;

	ocfs2_remove_empty_extent(el);

	return;
}

static int __ocfs2_rotate_tree_left(ocfs2_filesys *fs,
				    struct ocfs2_extent_tree *et,
				    struct ocfs2_path *path,
				    struct ocfs2_path **empty_extent_path)
{
	int i, ret, subtree_root, deleted;
	uint32_t right_cpos;
	struct ocfs2_path *left_path = NULL;
	struct ocfs2_path *right_path = NULL;

	assert(ocfs2_is_empty_extent(&(path_leaf_el(path)->l_recs[0])));

	*empty_extent_path = NULL;

	ret = ocfs2_find_cpos_for_right_leaf(fs, path, &right_cpos);
	if (ret)
		goto out;

	left_path = ocfs2_new_path_from_path(path);
	if (!left_path) {
		ret = OCFS2_ET_NO_MEMORY;
		goto out;
	}

	ocfs2_cp_path(fs, left_path, path);

	right_path = ocfs2_new_path_from_path(path);
	if (!right_path) {
		ret = OCFS2_ET_NO_MEMORY;
		goto out;
	}

	while (right_cpos) {
		ret = ocfs2_find_path(fs, right_path, right_cpos);
		if (ret)
			goto out;

		subtree_root = ocfs2_find_subtree_root(left_path,
						       right_path);

		ret = ocfs2_rotate_subtree_left(fs, et, left_path,
						right_path, subtree_root,
						&deleted);
		if (ret == EAGAIN) {
			/*
			 * The rotation has to temporarily stop due to
			 * the right subtree having an empty
			 * extent. Pass it back to the caller for a
			 * fixup.
			 */
			*empty_extent_path = right_path;
			right_path = NULL;
			goto out;
		}
		if (ret)
			goto out;

		/*
		 * The subtree rotate might have removed records on
		 * the rightmost edge. If so, then rotation is
		 * complete.
		 */
		if (deleted)
			break;

		ocfs2_mv_path(left_path, right_path);

		ret = ocfs2_find_cpos_for_right_leaf(fs, left_path,
						     &right_cpos);
		if (ret)
			goto out;
	}

out:
	ocfs2_free_path(right_path);
	ocfs2_free_path(left_path);

	/*
	 * the path's information is changed during the process of rotation,
	 * so re-read them.
	 */
	for (i = 1; i <= path->p_tree_depth; i++) {
		ret = ocfs2_read_extent_block(fs, path->p_node[i].blkno,
					      path->p_node[i].buf);
		if (ret)
			break;
	}

	return ret;
}

static int ocfs2_remove_rightmost_path(ocfs2_filesys *fs,
				       struct ocfs2_extent_tree *et,
				       struct ocfs2_path *path)
{
	int ret, subtree_index, i;
	uint32_t cpos;
	struct ocfs2_path *left_path = NULL;
	struct ocfs2_extent_block *eb;
	struct ocfs2_extent_list *el;

	ret = ocfs2_find_cpos_for_left_leaf(path, &cpos);
	if (ret)
		goto out;

	if (cpos) {
		/*
		 * We have a path to the left of this one - it needs
		 * an update too.
		 */
		left_path = ocfs2_new_path_from_path(path);
		if (!left_path) {
			ret = OCFS2_ET_NO_MEMORY;
			goto out;
		}

		ret = ocfs2_find_path(fs, left_path, cpos);
		if (ret)
			goto out;

		subtree_index = ocfs2_find_subtree_root(left_path, path);

		ocfs2_unlink_subtree(fs, left_path, path,
				     subtree_index);
		ocfs2_update_edge_lengths(left_path);

		/*
		 * Now the good extent block information is stored in left_path, so
		 * synchronize the right path with it.
		 */
		for (i = 0; i <= subtree_index; i++)
			memcpy(path->p_node[i].buf,
			       left_path->p_node[i].buf,
			       fs->fs_blocksize);
		ret = ocfs2_sync_path_to_disk(fs, left_path,
					      NULL, subtree_index);
		if (ret)
			goto out;

		eb = (struct ocfs2_extent_block *)path_leaf_buf(left_path);
		ocfs2_et_set_last_eb_blk(et, eb->h_blkno);
	} else {
		/*
		 * 'path' is also the leftmost path which
		 * means it must be the only one. This gets
		 * handled differently because we want to
		 * revert the inode back to having extents
		 * in-line.
		 */
		ocfs2_unlink_path(fs, path, 1);

		el = et->et_root_el;
		el->l_tree_depth = 0;
		el->l_next_free_rec = 0;
		memset(&el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));

		ocfs2_et_set_last_eb_blk(et, 0);
	}

out:
	ocfs2_free_path(left_path);
	return ret;
}

/*
 * Left rotation of btree records.
 *
 * In many ways, this is (unsurprisingly) the opposite of right
 * rotation. We start at some non-rightmost path containing an empty
 * extent in the leaf block. The code works its way to the rightmost
 * path by rotating records to the left in every subtree.
 *
 * This is used by any code which reduces the number of extent records
 * in a leaf. After removal, an empty record should be placed in the
 * leftmost list position.
 *
 * This won't handle a length update of the rightmost path records if
 * the rightmost tree leaf record is removed so the caller is
 * responsible for detecting and correcting that.
 */
static int ocfs2_rotate_tree_left(ocfs2_filesys *fs,
				  struct ocfs2_extent_tree *et,
				  struct ocfs2_path *path)
{
	int ret = 0;
	struct ocfs2_path *tmp_path = NULL, *restart_path = NULL;
	struct ocfs2_extent_block *eb;
	struct ocfs2_extent_list *el;

	el = path_leaf_el(path);
	if (!ocfs2_is_empty_extent(&el->l_recs[0]))
		return 0;

	if (path->p_tree_depth == 0) {
rightmost_no_delete:
		/*
		 * In-inode extents. This is trivially handled, so do
		 * it up front.
		 */
		ocfs2_rotate_rightmost_leaf_left(fs,
						 path_leaf_el(path));

		/* we have to synchronize the modified extent block to disk. */
		if (path->p_tree_depth > 0) {
			ret = ocfs2_write_extent_block(fs,
						       path_leaf_blkno(path),
						       path_leaf_buf(path));
		}

		goto out;
	}

	/*
	 * Handle rightmost branch now. There's several cases:
	 *  1) simple rotation leaving records in there. That's trivial.
	 *  2) rotation requiring a branch delete - there's no more
	 *     records left. Two cases of this:
	 *     a) There are branches to the left.
	 *     b) This is also the leftmost (the only) branch.
	 *
	 *  1) is handled via ocfs2_rotate_rightmost_leaf_left()
	 *  2a) we need the left branch so that we can update it with the unlink
	 *  2b) we need to bring the inode back to inline extents.
	 */

	eb = (struct ocfs2_extent_block *)path_leaf_buf(path);
	el = &eb->h_list;
	if (eb->h_next_leaf_blk == 0) {
		/*
		 * This gets a bit tricky if we're going to delete the
		 * rightmost path. Get the other cases out of the way
		 * 1st.
		 */
		if (el->l_next_free_rec > 1)
			goto rightmost_no_delete;

		if (el->l_next_free_rec == 0) {
			ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
			goto out;
		}

		/*
		 * XXX: The caller can not trust "path" any more after
		 * this as it will have been deleted. What do we do?
		 *
		 * In theory the rotate-for-merge code will never get
		 * here because it'll always ask for a rotate in a
		 * nonempty list.
		 */

		ret = ocfs2_remove_rightmost_path(fs, et, path);
		goto out;
	}

	/*
	 * Now we can loop, remembering the path we get from EAGAIN
	 * and restarting from there.
	 */
try_rotate:
	ret = __ocfs2_rotate_tree_left(fs, et, path, &restart_path);
	if (ret && ret != EAGAIN) {
		goto out;
	}

	while (ret == EAGAIN) {
		tmp_path = restart_path;
		restart_path = NULL;

		ret = __ocfs2_rotate_tree_left(fs, et, tmp_path, &restart_path);
		if (ret && ret != EAGAIN) {
			goto out;
		}

		ocfs2_free_path(tmp_path);
		tmp_path = NULL;

		if (ret == 0)
			goto try_rotate;
	}

out:
	ocfs2_free_path(tmp_path);
	ocfs2_free_path(restart_path);
	return ret;
}

static void ocfs2_cleanup_merge(struct ocfs2_extent_list *el,
				int index)
{
	struct ocfs2_extent_rec *rec = &el->l_recs[index];
	unsigned int size;

	if (rec->e_leaf_clusters == 0) {
		/*
		 * We consumed all of the merged-from record. An empty
		 * extent cannot exist anywhere but the 1st array
		 * position, so move things over if the merged-from
		 * record doesn't occupy that position.
		 *
		 * This creates a new empty extent so the caller
		 * should be smart enough to have removed any existing
		 * ones.
		 */
		if (index > 0) {
			assert(!ocfs2_is_empty_extent(&el->l_recs[0]));
			size = index * sizeof(struct ocfs2_extent_rec);
			memmove(&el->l_recs[1], &el->l_recs[0], size);
		}

		/*
		 * Always memset - the caller doesn't check whether it
		 * created an empty extent, so there could be junk in
		 * the other fields.
		 */
		memset(&el->l_recs[0], 0, sizeof(struct ocfs2_extent_rec));
	}
}

/*
 * Remove split_rec clusters from the record at index and merge them
 * onto the beginning of the record at index + 1.
 */
static int ocfs2_merge_rec_right(ocfs2_filesys *fs,
				struct ocfs2_extent_rec *split_rec,
				struct ocfs2_extent_list *el, int index)
{
	unsigned int split_clusters = split_rec->e_leaf_clusters;
	struct ocfs2_extent_rec *left_rec;
	struct ocfs2_extent_rec *right_rec;

	assert(index < el->l_next_free_rec);

	left_rec = &el->l_recs[index];
	right_rec = &el->l_recs[index + 1];

	left_rec->e_leaf_clusters -= split_clusters;

	right_rec->e_cpos -= split_clusters;
	right_rec->e_blkno -=
			ocfs2_clusters_to_blocks(fs, split_clusters);
	right_rec->e_leaf_clusters += split_clusters;

	ocfs2_cleanup_merge(el, index);

	return 0;
}

/*
 * Remove split_rec clusters from the record at index and merge them
 * onto the tail of the record at index - 1.
 */
static int ocfs2_merge_rec_left(ocfs2_filesys *fs,
				struct ocfs2_extent_rec *split_rec,
				struct ocfs2_extent_list *el, int index)
{
	int has_empty_extent = 0;
	unsigned int split_clusters = split_rec->e_leaf_clusters;
	struct ocfs2_extent_rec *left_rec;
	struct ocfs2_extent_rec *right_rec;

	assert(index > 0);

	left_rec = &el->l_recs[index - 1];
	right_rec = &el->l_recs[index];
	if (ocfs2_is_empty_extent(&el->l_recs[0]))
		has_empty_extent = 1;

	if (has_empty_extent && index == 1) {
		/*
		 * The easy case - we can just plop the record right in.
		 */
		*left_rec = *split_rec;

		has_empty_extent = 0;
	} else {
		left_rec->e_leaf_clusters += split_clusters;
	}

	right_rec->e_cpos += split_clusters;
	right_rec->e_blkno +=
		ocfs2_clusters_to_blocks(fs, split_clusters);
	right_rec->e_leaf_clusters -= split_clusters;

	ocfs2_cleanup_merge(el, index);

	return 0;
}

static int ocfs2_try_to_merge_extent(ocfs2_filesys *fs,
				     struct ocfs2_extent_tree *et,
				     struct ocfs2_path *left_path,
				     int split_index,
				     struct ocfs2_extent_rec *split_rec,
				     struct ocfs2_merge_ctxt *ctxt)

{
	int ret = 0;
	struct ocfs2_extent_list *el = path_leaf_el(left_path);
	struct ocfs2_extent_rec *rec = &el->l_recs[split_index];

	assert(ctxt->c_contig_type != CONTIG_NONE);

	if (ctxt->c_split_covers_rec && ctxt->c_has_empty_extent) {
		/*
		 * The merge code will need to create an empty
		 * extent to take the place of the newly
		 * emptied slot. Remove any pre-existing empty
		 * extents - having more than one in a leaf is
		 * illegal.
		 */
		ret = ocfs2_rotate_tree_left(fs, et, left_path);
		if (ret)
			goto out;

		split_index--;
		rec = &el->l_recs[split_index];
	}

	if (ctxt->c_contig_type == CONTIG_LEFTRIGHT) {
		/*
		 * Left-right contig implies this.
		 */
		assert(ctxt->c_split_covers_rec);
		assert(split_index != 0);

		/*
		 * Since the leftright insert always covers the entire
		 * extent, this call will delete the insert record
		 * entirely, resulting in an empty extent record added to
		 * the extent block.
		 *
		 * Since the adding of an empty extent shifts
		 * everything back to the right, there's no need to
		 * update split_index here.
		 */
		ret = ocfs2_merge_rec_left(fs, split_rec, el, split_index);
		if (ret)
			goto out;

		/*
		 * We can only get this from logic error above.
		 */
		assert(ocfs2_is_empty_extent(&el->l_recs[0]));

		/*
		 * The left merge left us with an empty extent, remove
		 * it.
		 */
		ret = ocfs2_rotate_tree_left(fs, et, left_path);
		if (ret)
			goto out;

		split_index--;
		rec = &el->l_recs[split_index];

		/*
		 * Note that we don't pass split_rec here on purpose -
		 * we've merged it into the left side.
		 */
		ret = ocfs2_merge_rec_right(fs, rec, el, split_index);
		if (ret)
			goto out;

		assert(ocfs2_is_empty_extent(&el->l_recs[0]));

		ret = ocfs2_rotate_tree_left(fs, et, left_path);
		/*
		 * Error from this last rotate is not critical, so
		 * don't bubble it up.
		 */
		ret = 0;
	} else {
		/*
		 * Merge a record to the left or right.
		 *
		 * 'contig_type' is relative to the existing record,
		 * so for example, if we're "right contig", it's to
		 * the record on the left (hence the left merge).
		 */
		if (ctxt->c_contig_type == CONTIG_RIGHT) {
			ret = ocfs2_merge_rec_left(fs,
						   split_rec, el,
						   split_index);
			if (ret)
				goto out;
		} else {
			ret = ocfs2_merge_rec_right(fs,
						    split_rec, el,
						    split_index);
			if (ret)
				goto out;
		}

		/* we have to synchronize the modified extent block to disk. */
		if (left_path->p_tree_depth > 0) {
			ret = ocfs2_write_extent_block(fs,
					       path_leaf_blkno(left_path),
					       path_leaf_buf(left_path));
			if (ret)
				goto out;
		}

		if (ctxt->c_split_covers_rec) {
			/*
			 * The merge may have left an empty extent in
			 * our leaf. Try to rotate it away.
			 */
			ret = ocfs2_rotate_tree_left(fs, et, left_path);
			ret = 0;
		}
	}

out:
	return ret;
}

static void ocfs2_subtract_from_rec(ocfs2_filesys *fs,
				    enum ocfs2_split_type split,
				    struct ocfs2_extent_rec *rec,
				    struct ocfs2_extent_rec *split_rec)
{
	uint64_t len_blocks;

	len_blocks = ocfs2_clusters_to_blocks(fs, split_rec->e_leaf_clusters);

	if (split == SPLIT_LEFT) {
		/*
		 * Region is on the left edge of the existing
		 * record.
		 */
		rec->e_cpos += split_rec->e_leaf_clusters;
		rec->e_blkno += len_blocks;
		rec->e_leaf_clusters -= split_rec->e_leaf_clusters;
	} else {
		/*
		 * Region is on the right edge of the existing
		 * record.
		 */
		rec->e_leaf_clusters -= split_rec->e_leaf_clusters;
	}
}

/*
 * Change the depth of the tree. That means allocating an extent block,
 * copying all extent records from the dinode into the extent block,
 * and then pointing the dinode to the new extent_block.
 */
static errcode_t shift_tree_depth(ocfs2_filesys *fs,
				  struct ocfs2_extent_tree *et,
				  char **new_eb)
{
	errcode_t ret;
	char *buf = NULL;
	uint64_t blkno;
	struct ocfs2_extent_list *el = et->et_root_el;
	struct ocfs2_extent_block *eb;
	uint32_t new_clusters;

	if (el->l_next_free_rec != el->l_count)
		return OCFS2_ET_INTERNAL_FAILURE;

	ret = ocfs2_malloc_block(fs->fs_io, &buf);
	if (ret)
		return ret;

	ret = ocfs2_new_extent_block(fs, &blkno);
	if (ret)
		goto out;

	ret = ocfs2_read_extent_block(fs, blkno, buf);
	if (ret)
		goto out;

	eb = (struct ocfs2_extent_block *)buf;
	eb->h_list.l_tree_depth = el->l_tree_depth;
	eb->h_list.l_next_free_rec = el->l_next_free_rec;
	memcpy(eb->h_list.l_recs, el->l_recs,
	       sizeof(struct ocfs2_extent_rec) * el->l_count);

	new_clusters = ocfs2_sum_rightmost_rec(&eb->h_list);

	el->l_tree_depth++;
	memset(el->l_recs, 0,
	       sizeof(struct ocfs2_extent_rec) * el->l_count);
	el->l_recs[0].e_cpos = 0;
	el->l_recs[0].e_blkno = blkno;
	el->l_recs[0].e_int_clusters = new_clusters;
	el->l_next_free_rec = 1;

	if (el->l_tree_depth == 1)
		ocfs2_et_set_last_eb_blk(et, blkno);

	ret = ocfs2_write_extent_block(fs, blkno, buf);
	if (!ret)
		*new_eb = buf;
out:
	if (buf && !*new_eb)
		ocfs2_free(&buf);

	return ret;
}

static enum ocfs2_contig_type
ocfs2_figure_merge_contig_type(ocfs2_filesys *fs,
			       struct ocfs2_extent_tree *et,
			       struct ocfs2_extent_list *el, int index,
			       struct ocfs2_extent_rec *split_rec)
{
	struct ocfs2_extent_rec *rec;
	enum ocfs2_contig_type ret = CONTIG_NONE;

	/*
	 * We're careful to check for an empty extent record here -
	 * the merge code will know what to do if it sees one.
	 */

	if (index > 0) {
		rec = &el->l_recs[index - 1];
		if (index == 1 && ocfs2_is_empty_extent(rec)) {
			if (split_rec->e_cpos == el->l_recs[index].e_cpos)
				ret = CONTIG_RIGHT;
		} else {
			ret = ocfs2_et_extent_contig(fs, et, rec, split_rec);
		}
	}

	if (index < el->l_next_free_rec - 1) {
		enum ocfs2_contig_type contig_type;

		rec = &el->l_recs[index + 1];
		contig_type = ocfs2_et_extent_contig(fs, et, rec, split_rec);

		if (contig_type == CONTIG_LEFT && ret == CONTIG_RIGHT)
			ret = CONTIG_LEFTRIGHT;
		else if (ret == CONTIG_NONE)
			ret = contig_type;
	}

	return ret;
}

static void ocfs2_figure_contig_type(ocfs2_filesys *fs,
				     struct ocfs2_extent_tree *et,
				     struct ocfs2_insert_type *insert,
				     struct ocfs2_extent_list *el,
				     struct ocfs2_extent_rec *insert_rec)
{
	int i;
	enum ocfs2_contig_type contig_type = CONTIG_NONE;

	assert(el->l_tree_depth == 0);

	for(i = 0; i < el->l_next_free_rec; i++) {
		contig_type = ocfs2_et_extent_contig(fs, et, &el->l_recs[i],
						     insert_rec);
		if (contig_type != CONTIG_NONE) {
			insert->ins_contig_index = i;
			break;
		}
	}
	insert->ins_contig = contig_type;
}

/*
 * This should only be called against the righmost leaf extent list.
 *
 * ocfs2_figure_appending_type() will figure out whether we'll have to
 * insert at the tail of the rightmost leaf.
 *
 * This should also work against the dinode list for tree's with 0
 * depth. If we consider the dinode list to be the rightmost leaf node
 * then the logic here makes sense.
 */
static void ocfs2_figure_appending_type(struct ocfs2_insert_type *insert,
					struct ocfs2_extent_list *el,
					struct ocfs2_extent_rec *insert_rec)
{
	int i;
	uint32_t cpos = insert_rec->e_cpos;
	struct ocfs2_extent_rec *rec;

	insert->ins_appending = APPEND_NONE;

	assert(el->l_tree_depth == 0);

	if (!el->l_next_free_rec)
		goto set_tail_append;

	if (ocfs2_is_empty_extent(&el->l_recs[0])) {
		/* Were all records empty? */
		if (el->l_next_free_rec == 1)
			goto set_tail_append;
	}

	i = el->l_next_free_rec - 1;
	rec = &el->l_recs[i];

	if (cpos >= (rec->e_cpos + rec->e_leaf_clusters))
		goto set_tail_append;

	return;

set_tail_append:
	insert->ins_appending = APPEND_TAIL;
}

/*
 * Helper function called at the begining of an insert.
 *
 * This computes a few things that are commonly used in the process of
 * inserting into the btree:
 *   - Whether the new extent is contiguous with an existing one.
 *   - The current tree depth.
 *   - Whether the insert is an appending one.
 *   - The total # of free records in the tree.
 *
 * All of the information is stored on the ocfs2_insert_type
 * structure.
 */
static int ocfs2_figure_insert_type(struct insert_ctxt *ctxt,
				    char **last_eb_buf,
				    int *free_records,
				    struct ocfs2_insert_type *insert)
{
	int ret;
	struct ocfs2_extent_block *eb;
	struct ocfs2_extent_list *el;
	struct ocfs2_extent_rec *insert_rec = &ctxt->rec;
	ocfs2_filesys *fs = ctxt->fs;
	struct ocfs2_extent_tree *et = ctxt->et;
	struct ocfs2_path *path = NULL;
	char *buf = *last_eb_buf;
	uint64_t last_eb_blk = ocfs2_et_get_last_eb_blk(et);

	insert->ins_split = SPLIT_NONE;

	el = et->et_root_el;
	insert->ins_tree_depth = el->l_tree_depth;

	if (el->l_tree_depth) {
		/*
		 * If we have tree depth, we read in the
		 * rightmost extent block ahead of time as
		 * ocfs2_figure_insert_type() and ocfs2_add_branch()
		 * may want it later.
		 */
		assert(buf);
		ret = ocfs2_read_extent_block(fs, last_eb_blk, buf);
		if (ret)
			goto out;

		eb = (struct ocfs2_extent_block *) buf;
		el = &eb->h_list;
	}
	/*
	 * Unless we have a contiguous insert, we'll need to know if
	 * there is room left in our allocation tree for another
	 * extent record.
	 *
	 * XXX: This test is simplistic, we can search for empty
	 * extent records too.
	 */
	*free_records = el->l_count - el->l_next_free_rec;

	if (!insert->ins_tree_depth) {
		ocfs2_figure_contig_type(fs, et, insert, el, insert_rec);
		ocfs2_figure_appending_type(insert, el, insert_rec);
		return 0;
	}

	path = ocfs2_new_path_from_et(et);
	if (!path) {
		ret = OCFS2_ET_NO_MEMORY;
		goto out;
	}
	/*
	 * In the case that we're inserting past what the tree
	 * currently accounts for, ocf2_find_path() will return for
	 * us the rightmost tree path. This is accounted for below in
	 * the appending code.
	 */
	ret = ocfs2_find_path(fs, path, insert_rec->e_cpos);
	if (ret)
		goto out;

	el = path_leaf_el(path);

	/*
	 * Now that we have the path, there's two things we want to determine:
	 * 1) Contiguousness (also set contig_index if this is so)
	 *
	 * 2) Are we doing an append? We can trivially break this up
         *     into two types of appends: simple record append, or a
         *     rotate inside the tail leaf.
	 */
	ocfs2_figure_contig_type(fs, et, insert, el, insert_rec);

	/*
	 * The insert code isn't quite ready to deal with all cases of
	 * left contiguousness. Specifically, if it's an insert into
	 * the 1st record in a leaf, it will require the adjustment of
	 * e_clusters on the last record of the path directly to it's
	 * left. For now, just catch that case and fool the layers
	 * above us. This works just fine for tree_depth == 0, which
	 * is why we allow that above.
	 */
	if (insert->ins_contig == CONTIG_LEFT &&
	    insert->ins_contig_index == 0)
		insert->ins_contig = CONTIG_NONE;

	/*
	 * Ok, so we can simply compare against last_eb to figure out
	 * whether the path doesn't exist. This will only happen in
	 * the case that we're doing a tail append, so maybe we can
	 * take advantage of that information somehow.
	 */
	if (last_eb_blk == path_leaf_blkno(path)) {
		/*
		 * Ok, ocfs2_find_path() returned us the rightmost
		 * tree path. This might be an appending insert. There are
		 * two cases:
		 *    1) We're doing a true append at the tail:
		 *	-This might even be off the end of the leaf
		 *    2) We're "appending" by rotating in the tail
		 */
		ocfs2_figure_appending_type(insert, el, insert_rec);
	}

out:
	ocfs2_free_path(path);

	return ret;
}

/*
 * Do the final bits of extent record insertion at the target leaf
 * list. If this leaf is part of an allocation tree, it is assumed
 * that the tree above has been prepared.
 */
static void ocfs2_insert_at_leaf(ocfs2_filesys *fs,
				 struct ocfs2_extent_rec *insert_rec,
				 struct ocfs2_extent_list *el,
				 struct ocfs2_insert_type *insert)
{
	int i = insert->ins_contig_index;
	unsigned int range;
	struct ocfs2_extent_rec *rec;

	assert(el->l_tree_depth == 0);

	if (insert->ins_split != SPLIT_NONE) {
		i = ocfs2_search_extent_list(el, insert_rec->e_cpos);
		assert(i != -1);
		rec = &el->l_recs[i];
		ocfs2_subtract_from_rec(fs, insert->ins_split, rec,
					insert_rec);
		goto rotate;
	}

	/*
	 * Contiguous insert - either left or right.
	 */
	if (insert->ins_contig != CONTIG_NONE) {
		rec = &el->l_recs[i];
		if (insert->ins_contig == CONTIG_LEFT) {
			rec->e_blkno = insert_rec->e_blkno;
			rec->e_cpos = insert_rec->e_cpos;
		}
		rec->e_leaf_clusters += insert_rec->e_leaf_clusters;
		return;
	}

	/*
	 * Handle insert into an empty leaf.
	 */
	if (el->l_next_free_rec == 0 ||
	    (el->l_next_free_rec == 1 &&
	     ocfs2_is_empty_extent(&el->l_recs[0]))) {
		el->l_recs[0] = *insert_rec;
		el->l_next_free_rec = 1;
		return;
	}

	/*
	 * Appending insert.
	 */
	if (insert->ins_appending == APPEND_TAIL) {
		i = el->l_next_free_rec - 1;
		rec = &el->l_recs[i];
		range = rec->e_cpos + rec->e_leaf_clusters;
		assert(insert_rec->e_cpos >= range);

		i++;
		el->l_recs[i] = *insert_rec;
		el->l_next_free_rec += 1;
		return;
	}

rotate:
	/*
	 * Ok, we have to rotate.
	 *
	 * At this point, it is safe to assume that inserting into an
	 * empty leaf and appending to a leaf have both been handled
	 * above.
	 *
	 * This leaf needs to have space, either by the empty 1st
	 * extent record, or by virtue of an l_next_rec < l_count.
	 */
	ocfs2_rotate_leaf(el, insert_rec);
}

static int ocfs2_adjust_rightmost_records(ocfs2_filesys *fs,
					  struct ocfs2_path *path,
					  struct ocfs2_extent_rec *insert_rec)
{
	int i, next_free;
	struct ocfs2_extent_list *el;
	struct ocfs2_extent_rec *rec;

	/*
	 * Update everything except the leaf block.
	 */
	for (i = 0; i < path->p_tree_depth; i++) {
		el = path->p_node[i].el;

		next_free = el->l_next_free_rec;
		if (next_free == 0)
			return OCFS2_ET_CORRUPT_EXTENT_BLOCK;

		rec = &el->l_recs[next_free - 1];

		rec->e_int_clusters = insert_rec->e_cpos;
		rec->e_int_clusters += insert_rec->e_leaf_clusters;
		rec->e_int_clusters -= rec->e_cpos;
	}

	return 0;
}

static int ocfs2_append_rec_to_path(ocfs2_filesys *fs,
				    struct ocfs2_extent_rec *insert_rec,
				    struct ocfs2_path *right_path,
				    struct ocfs2_path **ret_left_path)
{
	int ret, next_free, i;
	struct ocfs2_extent_list *el;
	struct ocfs2_path *left_path = NULL;

	*ret_left_path = NULL;

	/*
	 * This shouldn't happen for non-trees. The extent rec cluster
	 * count manipulation below only works for interior nodes.
	 */
	assert(right_path->p_tree_depth > 0);

	/*
	 * If our appending insert is at the leftmost edge of a leaf,
	 * then we might need to update the rightmost records of the
	 * neighboring path.
	 */

	el = path_leaf_el(right_path);
	next_free = el->l_next_free_rec;
	if (next_free == 0 ||
	    (next_free == 1 && ocfs2_is_empty_extent(&el->l_recs[0]))) {
		uint32_t left_cpos;

		ret = ocfs2_find_cpos_for_left_leaf(right_path, &left_cpos);
		if (ret)
			goto out;
		/*
		 * No need to worry if the append is already in the
		 * leftmost leaf.
		 */
		if (left_cpos) {
			left_path = ocfs2_new_path_from_path(right_path);
			if (!left_path) {
				ret = OCFS2_ET_NO_MEMORY;
				goto out;
			}

			ret = ocfs2_find_path(fs, left_path, left_cpos);
			if (ret)
				goto out;
		}
	}

	ret = ocfs2_adjust_rightmost_records(fs, right_path, insert_rec);
	if (ret)
		goto out;

	if (left_path) {
		/*
		 * Userspace sepcially.
		 * In case we have changed some blocks that is also in
		 * right_path, we have to update them in the left_path.
		 */
		i = 0;
		while (i++ < left_path->p_tree_depth)
			if (left_path->p_node[i].blkno ==
			    right_path->p_node[i].blkno)
				memcpy(left_path->p_node[i].buf,
				       right_path->p_node[i].buf,
				       fs->fs_blocksize);
	}

	*ret_left_path = left_path;
	ret = 0;
out:
	if (ret)
		ocfs2_free_path(left_path);
	return ret;
}

static void ocfs2_split_record(ocfs2_filesys *fs,
			       struct ocfs2_path *left_path,
			       struct ocfs2_path *right_path,
			       struct ocfs2_extent_rec *split_rec,
			       enum ocfs2_split_type split)
{
	int index;
	uint32_t cpos = split_rec->e_cpos;
	struct ocfs2_extent_list *left_el = NULL, *right_el, *insert_el, *el;
	struct ocfs2_extent_rec *rec, *tmprec;

	right_el = path_leaf_el(right_path);;
	if (left_path)
		left_el = path_leaf_el(left_path);

	el = right_el;
	insert_el = right_el;
	index = ocfs2_search_extent_list(el, cpos);
	if (index != -1) {
		if (index == 0 && left_path) {
			assert(!ocfs2_is_empty_extent(&el->l_recs[0]));

			/*
			 * This typically means that the record
			 * started in the left path but moved to the
			 * right as a result of rotation. We either
			 * move the existing record to the left, or we
			 * do the later insert there.
			 *
			 * In this case, the left path should always
			 * exist as the rotate code will have passed
			 * it back for a post-insert update.
			 */

			if (split == SPLIT_LEFT) {
				/*
				 * It's a left split. Since we know
				 * that the rotate code gave us an
				 * empty extent in the left path, we
				 * can just do the insert there.
				 */
				insert_el = left_el;
			} else {
				/*
				 * Right split - we have to move the
				 * existing record over to the left
				 * leaf. The insert will be into the
				 * newly created empty extent in the
				 * right leaf.
				 */
				tmprec = &right_el->l_recs[index];
				ocfs2_rotate_leaf(left_el, tmprec);
				el = left_el;

				memset(tmprec, 0, sizeof(*tmprec));
				index = ocfs2_search_extent_list(left_el, cpos);
				assert(index != -1);
			}
		}
	} else {
		assert(left_path);
		assert(ocfs2_is_empty_extent(&left_el->l_recs[0]));
		/*
		 * Left path is easy - we can just allow the insert to
		 * happen.
		 */
		el = left_el;
		insert_el = left_el;
		index = ocfs2_search_extent_list(el, cpos);
		assert(index != -1);
	}

	rec = &el->l_recs[index];
	ocfs2_subtract_from_rec(fs, split, rec, split_rec);
	ocfs2_rotate_leaf(insert_el, split_rec);
}

/*
 * This function only does inserts on an allocation b-tree. For dinode
 * lists, ocfs2_insert_at_leaf() is called directly.
 *
 * right_path is the path we want to do the actual insert
 * in. left_path should only be passed in if we need to update that
 * portion of the tree after an edge insert.
 */
static int ocfs2_insert_path(ocfs2_filesys *fs,
			     struct ocfs2_path *left_path,
			     struct ocfs2_path *right_path,
			     struct ocfs2_extent_rec *insert_rec,
			     struct ocfs2_insert_type *insert)
{
	int ret, subtree_index;

	if (insert->ins_split != SPLIT_NONE) {
		/*
		 * We could call ocfs2_insert_at_leaf() for some types
		 * of splits, but it's easier to just let one seperate
		 * function sort it all out.
		 */
		ocfs2_split_record(fs, left_path, right_path,
				   insert_rec, insert->ins_split);
	} else
		ocfs2_insert_at_leaf(fs, insert_rec, path_leaf_el(right_path),
				     insert);

	if (left_path) {
		/*
		 * The rotate code has indicated that we need to fix
		 * up portions of the tree after the insert.
		 */
		subtree_index = ocfs2_find_subtree_root(left_path, right_path);
		ocfs2_complete_edge_insert(fs, left_path,
				        right_path, subtree_index);
	} else
		subtree_index = 0;

	ret = ocfs2_sync_path_to_disk(fs, left_path,
				      right_path, subtree_index);
	if (ret)
		goto out;

	ret = 0;
out:
	return ret;
}

static int ocfs2_do_insert_extent(struct insert_ctxt* ctxt,
				  struct ocfs2_insert_type *type)
{
	int ret, rotate = 0;
	uint32_t cpos;
	struct ocfs2_path *right_path = NULL;
	struct ocfs2_path *left_path = NULL;
	struct ocfs2_extent_rec *insert_rec = &ctxt->rec;
	ocfs2_filesys *fs = ctxt->fs;
	struct ocfs2_extent_list *el = ctxt->et->et_root_el;

	if (el->l_tree_depth == 0) {
		ocfs2_insert_at_leaf(fs, insert_rec, el, type);
		goto out_update_clusters;
	}

	right_path = ocfs2_new_path_from_et(ctxt->et);
	if (!right_path) {
		ret = OCFS2_ET_NO_MEMORY;
		goto out;
	}

	/*
	 * Determine the path to start with. Rotations need the
	 * rightmost path, everything else can go directly to the
	 * target leaf.
	 */
	cpos = insert_rec->e_cpos;
	if (type->ins_appending == APPEND_NONE &&
	    type->ins_contig == CONTIG_NONE) {
		rotate = 1;
		cpos = UINT_MAX;
	}

	ret = ocfs2_find_path(fs, right_path, cpos);
	if (ret)
		goto out;

	/*
	 * Rotations and appends need special treatment - they modify
	 * parts of the tree's above them.
	 *
	 * Both might pass back a path immediate to the left of the
	 * one being inserted to. This will be cause
	 * ocfs2_insert_path() to modify the rightmost records of
	 * left_path to account for an edge insert.
	 *
	 * XXX: When modifying this code, keep in mind that an insert
	 * can wind up skipping both of these two special cases...
	 */

	if (rotate) {
		ret = ocfs2_rotate_tree_right(fs, type->ins_split,
					      insert_rec->e_cpos,
					      right_path, &left_path);
		if (ret)
			goto out;
	} else if (type->ins_appending == APPEND_TAIL
		   && type->ins_contig != CONTIG_LEFT) {
		ret = ocfs2_append_rec_to_path(fs, insert_rec,
					       right_path, &left_path);
		if (ret)
			goto out;
 	}

	ret = ocfs2_insert_path(fs, left_path, right_path, insert_rec, type);
	if (ret)
		goto out;

out_update_clusters:
	if (type->ins_split == SPLIT_NONE)
		ocfs2_et_update_clusters(ctxt->et, insert_rec->e_leaf_clusters);
	ret = 0;

out:
	ocfs2_free_path(left_path);
	ocfs2_free_path(right_path);

	return ret;
}

struct duplicate_ctxt {
	struct ocfs2_extent_tree *et;
	uint64_t next_leaf_blk;
};

static errcode_t duplicate_extent_block(ocfs2_filesys *fs,
					struct ocfs2_extent_list *old_el,
					struct ocfs2_extent_list *new_el,
					struct duplicate_ctxt *ctxt)
{
	int i;
	errcode_t ret;
	uint64_t blkno, new_blkno;
	struct ocfs2_extent_rec *rec = NULL;
	char *eb_buf = NULL, *new_eb_buf = NULL;
	struct ocfs2_extent_block *eb = NULL;
	struct ocfs2_extent_list *child_old_el = NULL, *child_new_el = NULL;

	assert (old_el->l_tree_depth > 0);

	/* empty the whole extent list at first. */
	*new_el = *old_el;
	new_el->l_next_free_rec = 0;
	memset(new_el->l_recs, 0,
	       sizeof(struct ocfs2_extent_rec) * new_el->l_count);

	if (old_el->l_next_free_rec == 0) {
		/* XXX:
		 * We have a tree depth > 0 and no extent record in it,
		 * should it be a corrupted block?
		 */
		ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
		goto bail;
	}

	ret = ocfs2_malloc_block(fs->fs_io, &eb_buf);
	if (ret)
		goto bail;
	ret = ocfs2_malloc_block(fs->fs_io, &new_eb_buf);
	if (ret)
		goto bail;

	/* we iterate the extent list from the last one for recording
	 * the next_leaf_blk for the previous leaf.
	 */
	for (i = old_el->l_next_free_rec - 1; i >= 0; i--) {
		rec = &old_el->l_recs[i];

		if (!ocfs2_rec_clusters(old_el->l_tree_depth, rec))
			continue;

		blkno = rec->e_blkno;
		ret = ocfs2_read_extent_block(fs, blkno, eb_buf);
		if (ret)
			goto bail;

		/* First make the new_buf the same as the old buf. */
		memcpy(new_eb_buf, eb_buf, fs->fs_blocksize);

		eb = (struct ocfs2_extent_block *)eb_buf;
		child_old_el = &eb->h_list;
		eb = (struct ocfs2_extent_block *)new_eb_buf;
		child_new_el = &eb->h_list;

		if (child_old_el->l_tree_depth > 0) {
			/* the extent record in our list still has child extent
			 * block, so we have to iterate it.
			 */
			ret = duplicate_extent_block(fs,
						     child_old_el,
						     child_new_el,
						     ctxt);
			if (ret)
				goto bail;
		}

		/* now we allocate a new extent block and save it. */
		ret = ocfs2_new_extent_block(fs, &new_blkno);
		if (ret)
			goto bail;

		eb = (struct ocfs2_extent_block *)new_eb_buf;
		eb->h_blkno = new_blkno;
		if (child_old_el->l_tree_depth == 0) {
			/*
			 * This is the leaf blkno, we have to set its
			 * h_next_leaf_blk and then record itself for
			 * future use.
			 */
			eb->h_next_leaf_blk = ctxt->next_leaf_blk;
			ctxt->next_leaf_blk = new_blkno;
		}

		ret = ocfs2_write_extent_block(fs, new_blkno, new_eb_buf);
		if (ret)
			goto bail;

		memcpy(&new_el->l_recs[i], rec, sizeof(struct ocfs2_extent_rec));
		new_el->l_recs[i].e_blkno = new_blkno;

		eb = (struct ocfs2_extent_block *)new_eb_buf;
		/* set the new i_last_eb_blk in the new dinode. */
		if (ocfs2_et_get_last_eb_blk(ctxt->et) == blkno)
			ocfs2_et_set_last_eb_blk(ctxt->et, new_blkno);
	}

	new_el->l_next_free_rec = old_el->l_next_free_rec;
	ret = 0;

bail:
	if (eb_buf)
		ocfs2_free(&eb_buf);
	if (new_eb_buf)
		ocfs2_free(&new_eb_buf);
	/* Free all the extent block we allocate. */
	if (ret) {
		for (i = 0; i < old_el->l_next_free_rec; i++) {
			rec = &new_el->l_recs[i];
			if (rec->e_blkno)
				ocfs2_delete_extent_block(fs, rec->e_blkno);
		}
	}

	return ret;
}

static errcode_t duplicate_extent_block_et(ocfs2_filesys *fs,
					   struct ocfs2_extent_tree *et)
{
	errcode_t ret = 0;
	struct ocfs2_extent_list *old_el = NULL, *new_el = NULL;
	char *old_buf, *new_buf;
	struct duplicate_ctxt ctxt;

	ret = ocfs2_malloc_block(fs->fs_io, &old_buf);
	if (ret)
		return ret;

	memcpy(old_buf, et->et_root_buf, fs->fs_blocksize);
	new_buf = et->et_root_buf;
	new_el = et->et_root_el;
	old_el = (struct ocfs2_extent_list *)
			(old_buf + ((char *)new_el - new_buf));

	assert(old_el->l_tree_depth > 0);

	/* empty the whole extent list at first. */
	*new_el = *old_el;
	memset(new_el->l_recs, 0,
	       sizeof(struct ocfs2_extent_rec) * new_el->l_count);
	new_el->l_next_free_rec = 0;

	memset(&ctxt, 0, sizeof(ctxt));
	ctxt.et = et;
	ctxt.next_leaf_blk = 0;
	ret = duplicate_extent_block(fs, old_el, new_el, &ctxt);

	ocfs2_free(&old_buf);
	return ret;
}

static void free_duplicated_extent_block(ocfs2_filesys *fs,
					struct ocfs2_extent_list *el)
{
	int i;
	errcode_t ret;
	char *buf = NULL;
	struct ocfs2_extent_rec *rec;
	struct ocfs2_extent_list *child_el;
	struct ocfs2_extent_block *eb;

	assert(el->l_tree_depth > 0);

	ret = ocfs2_malloc_block(fs->fs_io, &buf);
	if (ret)
		return;

	for (i = 0; i < el->l_next_free_rec; i ++) {
		rec = &el->l_recs[i];

		if (!ocfs2_rec_clusters(el->l_tree_depth, rec))
			continue;

		ret = ocfs2_read_extent_block(fs, rec->e_blkno, buf);
		if (ret)
			continue;

		eb = (struct ocfs2_extent_block *)buf;
		child_el = &eb->h_list;
		if (child_el->l_tree_depth > 0)
			free_duplicated_extent_block(fs, child_el);

		ocfs2_delete_extent_block(fs, rec->e_blkno);
	}

	if(buf)
		ocfs2_free(&buf);
}

/*
 * Grow a b-tree so that it has more records.
 *
 * We might shift the tree depth in which case existing paths should
 * be considered invalid.
 *
 * Tree depth after the grow is returned via *final_depth.
 *
 * *last_eb will be updated by ocfs2_add_branch().
 */
static int ocfs2_grow_tree(ocfs2_filesys *fs,
			   struct ocfs2_extent_tree *et,
			   int *final_depth, char **last_eb)
{
	errcode_t ret;
	char *eb_buf = NULL;
	int shift;
	struct ocfs2_extent_list *el = et->et_root_el;
	int depth = el->l_tree_depth;

	shift = ocfs2_find_branch_target(fs, et, &eb_buf);
	if (shift < 0) {
		ret = shift;
		goto out;
	}

	/* We traveled all the way to the bottom of the allocation tree
	 * and didn't find room for any more extents - we need to add
	 * another tree level */
	if (shift) {

		/* shift_tree_depth will return us a buffer with
		 * the new extent block (so we can pass that to
		 * ocfs2_add_branch). */
		ret = shift_tree_depth(fs, et, &eb_buf);
		if (ret)
			goto out;

		depth++;
		if (depth == 1) {
			/*
			 * Special case: we have room now if we shifted from
			 * tree_depth 0, so no more work needs to be done.
			 *
			 * We won't be calling add_branch, so pass
			 * back *last_eb as the new leaf.
			 */
			assert(*last_eb);
			memcpy(*last_eb, eb_buf, fs->fs_blocksize);
			goto out;
		}
	}

	/* call ocfs2_add_branch to add the final part of the tree with
	 * the new data. */
	ret = ocfs2_add_branch(fs, et, eb_buf, last_eb);

out:
	if (final_depth)
		*final_depth = depth;
	return ret;
}

errcode_t ocfs2_tree_insert_extent(ocfs2_filesys *fs,
				   struct ocfs2_extent_tree *et,
				   uint32_t cpos, uint64_t c_blkno,
				   uint32_t clusters, uint16_t flag)
{
	errcode_t ret;
	struct insert_ctxt ctxt;
	struct ocfs2_insert_type insert = {0, };
	char *last_eb = NULL;
	char *backup_buf = NULL;
	char *root_buf = et->et_root_buf;
	int free_records = 0;

	ctxt.fs = fs;
	ctxt.et = et;

	/* In order to orderize the written block sequence and avoid
	 * the corruption for the b-tree, we duplicate the extent block
	 * here and do the insertion in the duplicated ones.
	 *
	 * Note: we only do this in case the b-tree has extent blocks.
	 * And if the duplicate process fails, we should go on the normal
	 * insert process.
	 */
	if (et->et_root_el->l_tree_depth) {
		ret = ocfs2_malloc_block(fs->fs_io, &backup_buf);
		if (ret)
			goto bail;

		memcpy(backup_buf, root_buf, fs->fs_blocksize);

		/* duplicate the extent block. If it succeeds, di_buf
		 * will point to the new allocated extent blocks, and
		 * the following insertion will happens to the new ones.
		 */
		ret = duplicate_extent_block_et(fs, et);
		if (ret) {
			memcpy(root_buf, backup_buf, fs->fs_blocksize);
			ocfs2_free(&backup_buf);
			backup_buf = NULL;
		}
	}

	memset(&ctxt.rec, 0, sizeof(struct ocfs2_extent_rec));
	ctxt.rec.e_cpos = cpos;
	ctxt.rec.e_blkno = c_blkno;
	ctxt.rec.e_leaf_clusters = clusters;
	ctxt.rec.e_flags = flag;

	ret = ocfs2_malloc_block(fs->fs_io, &last_eb);
	if (ret)
		return ret;

	ret = ocfs2_figure_insert_type(&ctxt, &last_eb, &free_records, &insert);
	if (ret)
		goto bail;

	if (insert.ins_contig == CONTIG_NONE && free_records == 0) {
		ret = ocfs2_grow_tree(fs, ctxt.et,
				      &insert.ins_tree_depth, &last_eb);
		if (ret)
			goto bail;
	}

	/* Finally, we can add clusters. This might rotate the tree for us. */
	ret = ocfs2_do_insert_extent(&ctxt, &insert);
	if (ret)
		goto bail;

bail:
	if (backup_buf) {
		struct ocfs2_extent_list *free_el;
		int offset = (char *)et->et_root_el - et->et_root_buf;
		/* we have duplicated the extent block during the insertion.
		 * so if it succeeds, we should free the old ones, and if fails,
		 * the duplicate ones should be freed.
		 */

		if (ret)
			free_el = (struct ocfs2_extent_list *)
						(et->et_root_buf + offset);
		else
			free_el = (struct ocfs2_extent_list *)
						(backup_buf + offset);

		free_duplicated_extent_block(fs, free_el);
		ocfs2_free(&backup_buf);
	}

	if (last_eb)
		ocfs2_free(&last_eb);

	/*
	 * Write the root buffer here.
	 * If the caller don't initialize the write function, it should
	 * be responsible for write the root buffer.
	 */
	if (!ret && et->et_root_write)
		ret = et->et_root_write(fs, et->et_root_blkno, root_buf);

	return ret;
}

static void ocfs2_make_right_split_rec(ocfs2_filesys *fs,
				       struct ocfs2_extent_rec *split_rec,
				       uint32_t cpos,
				       struct ocfs2_extent_rec *rec)
{
	uint32_t rec_cpos = rec->e_cpos;
	uint32_t rec_range = rec_cpos + rec->e_leaf_clusters;

	memset(split_rec, 0, sizeof(struct ocfs2_extent_rec));

	split_rec->e_cpos = cpos;
	split_rec->e_leaf_clusters = rec_range - cpos;

	split_rec->e_blkno = rec->e_blkno;
	split_rec->e_blkno += ocfs2_clusters_to_blocks(fs, cpos - rec_cpos);

	split_rec->e_flags = rec->e_flags;
}

static int ocfs2_split_and_insert(struct insert_ctxt *ctxt,
				  struct ocfs2_path *path,
				  char **last_eb_buf,
				  int split_index,
				  struct ocfs2_extent_rec *orig_split_rec)
{
	int ret = 0, depth;
	unsigned int insert_range, rec_range, do_leftright = 0;
	struct ocfs2_extent_rec tmprec;
	struct ocfs2_extent_list *rightmost_el;
	struct ocfs2_extent_rec rec;
	struct ocfs2_insert_type insert;
	struct ocfs2_extent_block *eb;

leftright:
	/*
	 * Store a copy of the record on the stack - it might move
	 * around as the tree is manipulated below.
	 */
	rec = path_leaf_el(path)->l_recs[split_index];

	rightmost_el = ctxt->et->et_root_el;

	depth = rightmost_el->l_tree_depth;
	if (depth) {
		assert(*last_eb_buf);
		eb = (struct ocfs2_extent_block *) (*last_eb_buf);
		rightmost_el = &eb->h_list;
	}

	if (rightmost_el->l_next_free_rec == rightmost_el->l_count) {
		ret = ocfs2_grow_tree(ctxt->fs, ctxt->et,
				      &depth, last_eb_buf);
		if (ret)
			goto out;
	}

	memset(&insert, 0, sizeof(struct ocfs2_insert_type));
	insert.ins_appending = APPEND_NONE;
	insert.ins_contig = CONTIG_NONE;
	insert.ins_tree_depth = depth;

	insert_range = ctxt->rec.e_cpos + ctxt->rec.e_leaf_clusters;
	rec_range = rec.e_cpos + rec.e_leaf_clusters;

	if (ctxt->rec.e_cpos == rec.e_cpos) {
		insert.ins_split = SPLIT_LEFT;
	} else if (insert_range == rec_range) {
		insert.ins_split = SPLIT_RIGHT;
	} else {
		/*
		 * Left/right split. We fake this as a right split
		 * first and then make a second pass as a left split.
		 */
		insert.ins_split = SPLIT_RIGHT;

		ocfs2_make_right_split_rec(ctxt->fs, &tmprec, insert_range,
					   &rec);

		ctxt->rec = tmprec;

		assert(!do_leftright);
		do_leftright = 1;
	}

	ret = ocfs2_do_insert_extent(ctxt, &insert);
	if (ret)
		goto out;

	if (do_leftright == 1) {
		uint32_t cpos;
		struct ocfs2_extent_list *el;

		do_leftright++;
		ctxt->rec = *orig_split_rec;

		ocfs2_reinit_path(path, 1);

		cpos = ctxt->rec.e_cpos;
		ret = ocfs2_find_path(ctxt->fs, path, cpos);
		if (ret)
			goto out;

		el = path_leaf_el(path);
		split_index = ocfs2_search_extent_list(el, cpos);
		goto leftright;
	}
out:

	return ret;
}

/*
 * Split part or all of the extent record at split_index in the leaf
 * pointed to by path. Merge with the contiguous extent record if needed.
 *
 * Care is taken to handle contiguousness so as to not grow the tree.
 *
 * last_eb_buf should be the rightmost leaf block for any inode with a
 * btree. Since a split may grow the tree or a merge might shrink it,
 * the caller cannot trust the contents of that buffer after this call.
 *
 * This code is optimized for readability - several passes might be
 * made over certain portions of the tree.
 */
static int ocfs2_split_extent(struct insert_ctxt *insert_ctxt,
			      struct ocfs2_path *path,
			      int split_index)
{
	int ret = 0;
	struct ocfs2_extent_rec split_rec = insert_ctxt->rec;
	struct ocfs2_extent_list *el = path_leaf_el(path);
	char *last_eb_buf = NULL;
	struct ocfs2_extent_rec *rec = &el->l_recs[split_index];
	struct ocfs2_merge_ctxt merge_ctxt;
	ocfs2_filesys *fs = insert_ctxt->fs;

	if (rec->e_cpos > split_rec.e_cpos ||
	    ((rec->e_cpos + rec->e_leaf_clusters) <
	     (split_rec.e_cpos + split_rec.e_leaf_clusters))) {
		ret = OCFS2_ET_INVALID_ARGUMENT;
		goto out;
	}

	merge_ctxt.c_contig_type =
		ocfs2_figure_merge_contig_type(fs, insert_ctxt->et, el,
					       split_index, &split_rec);

	/*
	 * We have to allocate the last_eb_buf no matter the current tree
	 * depth is since we may shift the tree depth from 0 to 1 in
	 * ocfs2_split_and_insert and use last_eb_buf to store.
	 */
	ret = ocfs2_malloc_block(fs->fs_io, &last_eb_buf);
	if (ret)
		goto out;
	/*
	 * The core merge / split code wants to know how much room is
	 * left in this inodes allocation tree, so we pass the
	 * rightmost extent list.
	 */
	if (path->p_tree_depth) {
		ret = ocfs2_read_extent_block(fs,
				ocfs2_et_get_last_eb_blk(insert_ctxt->et),
				last_eb_buf);
		if (ret)
			goto out;
	}

	if (rec->e_cpos == split_rec.e_cpos &&
	    rec->e_leaf_clusters == split_rec.e_leaf_clusters)
		merge_ctxt.c_split_covers_rec = 1;
	else
		merge_ctxt.c_split_covers_rec = 0;

	merge_ctxt.c_has_empty_extent = ocfs2_is_empty_extent(&el->l_recs[0]);

	if (merge_ctxt.c_contig_type == CONTIG_NONE) {
		if (merge_ctxt.c_split_covers_rec) {
			el->l_recs[split_index] = split_rec;
			/*
			 * We only write the leaf block, and leave
			 * the write of the root to the caller.
			 */
			if (path->p_tree_depth)
				ret = ocfs2_write_extent_block(fs,
							path_leaf_blkno(path),
							path_leaf_buf(path));
		} else
			ret = ocfs2_split_and_insert(insert_ctxt, path,
						     &last_eb_buf, split_index,
						     &split_rec);
	} else {
		ret = ocfs2_try_to_merge_extent(fs, insert_ctxt->et, path,
						split_index, &split_rec,
						&merge_ctxt);
	}

out:
	if (last_eb_buf)
		ocfs2_free(&last_eb_buf);
	return ret;
}

/*
 * Change the flags of the already-existing extent at cpos for len clusters.
 *
 * new_flags: the flags we want to set.
 * clear_flags: the flags we want to clear.
 * p_blkno: the new physical offset we want this new extent starts from.
 *
 * If the existing extent is larger than the request, initiate a
 * split. An attempt will be made at merging with adjacent extents.
 */
int ocfs2_change_extent_flag(ocfs2_filesys *fs,
			     struct ocfs2_extent_tree *et,
			     uint32_t cpos, uint32_t len,
			     uint64_t p_blkno,
			     int new_flags, int clear_flags)
{
	int ret, index;
	struct ocfs2_path *left_path = NULL;
	struct ocfs2_extent_list *el;
	struct insert_ctxt ctxt;
	struct ocfs2_extent_rec *rec;
	char *backup_buf = NULL;

	/* In order to orderize the written block sequence and avoid
	 * the corruption for the inode, we duplicate the extent block
	 * here and do the insertion in the duplicated ones.
	 *
	 * Note: we only do this in case the file has extent blocks.
	 * And if the duplicate process fails, we should go on the normal
	 * insert process.
	 */
	if (et->et_root_el->l_tree_depth) {
		ret = ocfs2_malloc_block(fs->fs_io, &backup_buf);
		if (ret)
			goto out;

		memcpy(backup_buf, et->et_root_buf, fs->fs_blocksize);

		/* duplicate the extent block. If it succeeds, di_buf
		 * will point to the new allocated extent blocks, and
		 * the following insertion will happens to the new ones.
		 */
		ret = duplicate_extent_block_et(fs, et);
		if (ret) {
			memcpy(et->et_root_buf, backup_buf, fs->fs_blocksize);
			ocfs2_free(&backup_buf);
			backup_buf = NULL;
		}
	}

	left_path = ocfs2_new_path_from_et(et);
	if (!left_path) {
		ret = OCFS2_ET_NO_MEMORY;
		goto out;
	}

	ret = ocfs2_find_path(fs, left_path, cpos);
	if (ret)
		goto out;

	el = path_leaf_el(left_path);

	index = ocfs2_search_extent_list(el, cpos);
	if (index == -1 || index >= el->l_next_free_rec) {
		ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
		goto out;
	}

	ctxt.fs = fs;
	ctxt.et = et;

	ret = OCFS2_ET_IO;
	rec = &el->l_recs[index];
	if (new_flags && (rec->e_flags & new_flags))
		goto out;

	if (clear_flags && !(rec->e_flags & clear_flags))
		goto out;

	memset(&ctxt.rec, 0, sizeof(struct ocfs2_extent_rec));
	ctxt.rec.e_cpos = cpos;
	ctxt.rec.e_leaf_clusters = len;
	ctxt.rec.e_blkno = p_blkno;
	ctxt.rec.e_flags = rec->e_flags;
	if (new_flags)
		ctxt.rec.e_flags |= new_flags;
	if (clear_flags)
		ctxt.rec.e_flags &= ~clear_flags;

	ret = ocfs2_split_extent(&ctxt, left_path, index);
	if (ret)
		goto out;

	/*
	 * Write the root buffer here.
	 * If the caller don't initialize the write function, it should
	 * be responsible for write the root buffer.
	 */
	if (!ret && et->et_root_write)
		ret = et->et_root_write(fs, et->et_root_blkno, et->et_root_buf);

out:
	if (backup_buf) {
		struct ocfs2_extent_list *free_el;
		int offset = (char *)et->et_root_el - et->et_root_buf;
		/* we have duplicated the extent block during the insertion.
		 * so if it succeeds, we should free the old ones, and if fails,
		 * the duplicate ones should be freed.
		 */

		if (ret)
			free_el = (struct ocfs2_extent_list *)
					(et->et_root_buf + offset);
		else
			free_el = (struct ocfs2_extent_list *)
						(backup_buf + offset);

		free_duplicated_extent_block(fs, free_el);
		ocfs2_free(&backup_buf);
	}
	ocfs2_free_path(left_path);
	return ret;
}

static int ocfs2_split_tree(ocfs2_filesys *fs,
			    struct ocfs2_extent_tree *et,
			    struct ocfs2_path *path,
			    int index, uint32_t new_range)
{
	errcode_t ret;
	int depth;
	char *last_eb_buf = NULL;
	struct ocfs2_extent_block *eb;
	struct ocfs2_extent_list *rightmost_el, *el;
	struct ocfs2_extent_rec *rec;
	struct ocfs2_insert_type insert;
	struct insert_ctxt ctxt;

	ctxt.fs = fs;
	ctxt.et = et;

	ret = ocfs2_malloc_block(fs->fs_io, &last_eb_buf);
	if (ret)
		return ret;
	/*
	 * Setup the record to split before we grow the tree.
	 */
	el = path_leaf_el(path);
	rec = &el->l_recs[index];
	ocfs2_make_right_split_rec(fs, &ctxt.rec, new_range, rec);

	depth = path->p_tree_depth;
	if (depth > 0) {
		ret = ocfs2_read_extent_block(fs,
					      ocfs2_et_get_last_eb_blk(et),
					      last_eb_buf);
		if (ret)
			goto out;

		eb = (struct ocfs2_extent_block *)last_eb_buf;
		rightmost_el = &eb->h_list;
	} else
		rightmost_el = path_leaf_el(path);

	if (rightmost_el->l_next_free_rec == rightmost_el->l_count) {
		ret = ocfs2_grow_tree(fs, et, &depth, &last_eb_buf);
		if (ret)
			goto out;
	}

	memset(&insert, 0, sizeof(struct ocfs2_insert_type));
	insert.ins_appending = APPEND_NONE;
	insert.ins_contig = CONTIG_NONE;
	insert.ins_split = SPLIT_RIGHT;
	insert.ins_tree_depth = depth;

	ret = ocfs2_do_insert_extent(&ctxt, &insert);

out:
	if (last_eb_buf)
		ocfs2_free(&last_eb_buf);
	return ret;
}

static int ocfs2_truncate_rec(ocfs2_filesys *fs,
			      struct ocfs2_extent_tree *et,
			      struct ocfs2_path *path, int index,
			      uint32_t cpos, uint32_t len)
{
	errcode_t ret;
	uint32_t left_cpos, rec_range, trunc_range;
	int is_rightmost_tree_rec = 0;
	struct ocfs2_path *left_path = NULL;
	struct ocfs2_extent_list *el = path_leaf_el(path);
	struct ocfs2_extent_rec *rec;
	struct ocfs2_extent_block *eb;

	if (ocfs2_is_empty_extent(&el->l_recs[0]) && index > 0) {
		ret = ocfs2_rotate_tree_left(fs, et, path);
		if (ret)
			goto out;

		index--;
	}

	if (index == el->l_next_free_rec - 1 && path->p_tree_depth) {
		/*
		 * Check whether this is the rightmost tree record. If
		 * we remove all of this record or part of its right
		 * edge then an update of the record lengths above it
		 * will be required.
		 */
		eb = (struct ocfs2_extent_block *)path_leaf_buf(path);
		if (eb->h_next_leaf_blk == 0)
			is_rightmost_tree_rec = 1;
	}

	rec = &el->l_recs[index];
	if (index == 0 && path->p_tree_depth && rec->e_cpos == cpos) {
		/*
		 * Changing the leftmost offset (via partial or whole
		 * record truncate) of an interior (or rightmost) path
		 * means we have to update the subtree that is formed
		 * by this leaf and the one to it's left.
		 *
		 * There are two cases we can skip:
		 *   1) Path is the leftmost one in our btree.
		 *   2) The leaf is rightmost and will be empty after
		 *      we remove the extent record - the rotate code
		 *      knows how to update the newly formed edge.
		 */

		ret = ocfs2_find_cpos_for_left_leaf(path, &left_cpos);
		if (ret)
			goto out;

		if (left_cpos && el->l_next_free_rec > 1) {
			left_path = ocfs2_new_path_from_path(path);
			if (!left_path) {
				ret = OCFS2_ET_NO_MEMORY;
				goto out;
			}

			ret = ocfs2_find_path(fs, left_path, left_cpos);
			if (ret)
				goto out;
		}
	}

	rec_range = rec->e_cpos + ocfs2_rec_clusters(el->l_tree_depth, rec);
	trunc_range = cpos + len;

	if (rec->e_cpos == cpos && rec_range == trunc_range) {
		int next_free;

		memset(rec, 0, sizeof(*rec));
		ocfs2_cleanup_merge(el, index);

		next_free = el->l_next_free_rec;
		if (is_rightmost_tree_rec && next_free > 1) {
			/*
			 * We skip the edge update if this path will
			 * be deleted by the rotate code.
			 */
			rec = &el->l_recs[next_free - 1];
			ocfs2_adjust_rightmost_records(fs, path, rec);
		}
	} else if (rec->e_cpos == cpos) {
		/* Remove leftmost portion of the record. */
		rec->e_cpos += len;
		rec->e_blkno += ocfs2_clusters_to_blocks(fs, len);
		rec->e_leaf_clusters -= len;
	} else if (rec_range == trunc_range) {
		/* Remove rightmost portion of the record */
		rec->e_leaf_clusters -= len;
		if (is_rightmost_tree_rec)
			ocfs2_adjust_rightmost_records(fs, path, rec);
	} else {
		/* Caller should have trapped this. */
		assert(0);
	}

	if (left_path) {
		int subtree_index;

		subtree_index = ocfs2_find_subtree_root(left_path, path);
		ocfs2_complete_edge_insert(fs, left_path, path,
					   subtree_index);
	}

	ret = ocfs2_rotate_tree_left(fs, et, path);
out:
	ocfs2_free_path(left_path);
	return ret;
}

int ocfs2_remove_extent(ocfs2_filesys *fs,
			struct ocfs2_extent_tree *et,
			uint32_t cpos, uint32_t len)
{
	int ret, index;
	uint32_t rec_range, trunc_range;
	struct ocfs2_extent_rec *rec;
	struct ocfs2_extent_list *el;
	struct ocfs2_path *path = NULL;

	path = ocfs2_new_path_from_et(et);
	if (!path) {
		ret = OCFS2_ET_NO_MEMORY;
		goto out;
	}

	ret = ocfs2_find_path(fs, path, cpos);
	if (ret)
		goto out;

	el = path_leaf_el(path);
	index = ocfs2_search_extent_list(el, cpos);
	if (index == -1 || index >= el->l_next_free_rec) {
		ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
		goto out;
	}

	/*
	 * We have 3 cases of extent removal:
	 *   1) Range covers the entire extent rec
	 *   2) Range begins or ends on one edge of the extent rec
	 *   3) Range is in the middle of the extent rec (no shared edges)
	 *
	 * For case 1 we remove the extent rec and left rotate to
	 * fill the hole.
	 *
	 * For case 2 we just shrink the existing extent rec, with a
	 * tree update if the shrinking edge is also the edge of an
	 * extent block.
	 *
	 * For case 3 we do a right split to turn the extent rec into
	 * something case 2 can handle.
	 */
	rec = &el->l_recs[index];
	rec_range = rec->e_cpos + ocfs2_rec_clusters(el->l_tree_depth, rec);
	trunc_range = cpos + len;

	assert(cpos >= rec->e_cpos && trunc_range <= rec_range);

	if (rec->e_cpos == cpos || rec_range == trunc_range) {
		ret = ocfs2_truncate_rec(fs, et, path, index, cpos, len);
		if (ret)
			goto out;
	} else {
		ret = ocfs2_split_tree(fs, et, path, index, trunc_range);
		if (ret)
			goto out;

		/*
		 * The split could have manipulated the tree enough to
		 * move the record location, so we have to look for it again.
		 */
		ocfs2_reinit_path(path, 1);

		ret = ocfs2_find_path(fs, path, cpos);
		if (ret)
			goto out;

		el = path_leaf_el(path);
		index = ocfs2_search_extent_list(el, cpos);
		if (index == -1 || index >= el->l_next_free_rec) {
			ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
			goto out;
		}

		/*
		 * Double check our values here. If anything is fishy,
		 * it's easier to catch it at the top level.
		 */
		rec = &el->l_recs[index];
		rec_range = rec->e_cpos +
				ocfs2_rec_clusters(el->l_tree_depth, rec);
		if (rec_range != trunc_range) {
			ret = OCFS2_ET_CORRUPT_EXTENT_BLOCK;
			goto out;
		}

		ret = ocfs2_truncate_rec(fs, et, path, index, cpos, len);
		if (ret)
			goto out;
	}

out:
	ocfs2_free_path(path);
	return ret;
}

