alloc.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * alloc.c
 *
 * Extent allocs and frees
 *
 * Copyright (C) 2002, 2004 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 as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/swap.h>

#define MLOG_MASK_PREFIX ML_DISK_ALLOC
#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "aops.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "inode.h"
#include "journal.h"
#include "localalloc.h"
#include "suballoc.h"
#include "sysfile.h"
#include "file.h"
#include "super.h"
#include "uptodate.h"

#include "buffer_head_io.h"

/*
 * ocfs2_extent_tree and ocfs2_extent_tree_operations are used to abstract
 * the b-tree operations in ocfs2. Now all the b-tree operations are not
 * limited to ocfs2_dinode only. Any data which need to allocate clusters
 * to store can use b-tree. And it only needs to implement its ocfs2_extent_tree
 * and operation.
 *
 * ocfs2_extent_tree contains info for the root of the b-tree, it must have a
 * root ocfs2_extent_list and a root_bh so that they can be used in the b-tree
 * functions.
 * ocfs2_extent_tree_operations abstract the normal operations we do for
 * the root of extent b-tree.
 */
struct ocfs2_extent_tree;

struct ocfs2_extent_tree_operations {
	void (*set_last_eb_blk) (struct ocfs2_extent_tree *et, u64 blkno);
	u64 (*get_last_eb_blk) (struct ocfs2_extent_tree *et);
	void (*update_clusters) (struct inode *inode,
				 struct ocfs2_extent_tree *et,
				 u32 new_clusters);
	int (*sanity_check) (struct inode *inode, struct ocfs2_extent_tree *et);
};

struct ocfs2_extent_tree {
	enum ocfs2_extent_tree_type type;
	struct ocfs2_extent_tree_operations *eops;
	struct buffer_head *root_bh;
	struct ocfs2_extent_list *root_el;
	void *private;
	unsigned int max_leaf_clusters;
};

static void ocfs2_dinode_set_last_eb_blk(struct ocfs2_extent_tree *et,
					 u64 blkno)
{
	struct ocfs2_dinode *di = (struct ocfs2_dinode *)et->root_bh->b_data;

	BUG_ON(et->type != OCFS2_DINODE_EXTENT);
	di->i_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_dinode_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
	struct ocfs2_dinode *di = (struct ocfs2_dinode *)et->root_bh->b_data;

	BUG_ON(et->type != OCFS2_DINODE_EXTENT);
	return le64_to_cpu(di->i_last_eb_blk);
}

static void ocfs2_dinode_update_clusters(struct inode *inode,
					 struct ocfs2_extent_tree *et,
					 u32 clusters)
{
	struct ocfs2_dinode *di =
			(struct ocfs2_dinode *)et->root_bh->b_data;

	le32_add_cpu(&di->i_clusters, clusters);
	spin_lock(&OCFS2_I(inode)->ip_lock);
	OCFS2_I(inode)->ip_clusters = le32_to_cpu(di->i_clusters);
	spin_unlock(&OCFS2_I(inode)->ip_lock);
}

static int ocfs2_dinode_sanity_check(struct inode *inode,
				     struct ocfs2_extent_tree *et)
{
	int ret = 0;
	struct ocfs2_dinode *di;

	BUG_ON(et->type != OCFS2_DINODE_EXTENT);

	di = (struct ocfs2_dinode *)et->root_bh->b_data;
	if (!OCFS2_IS_VALID_DINODE(di)) {
		ret = -EIO;
		ocfs2_error(inode->i_sb,
			"Inode %llu has invalid path root",
			(unsigned long long)OCFS2_I(inode)->ip_blkno);
	}

	return ret;
}

static struct ocfs2_extent_tree_operations ocfs2_dinode_et_ops = {
	.set_last_eb_blk	= ocfs2_dinode_set_last_eb_blk,
	.get_last_eb_blk	= ocfs2_dinode_get_last_eb_blk,
	.update_clusters	= ocfs2_dinode_update_clusters,
	.sanity_check		= ocfs2_dinode_sanity_check,
};

static void ocfs2_xattr_value_set_last_eb_blk(struct ocfs2_extent_tree *et,
					      u64 blkno)
{
	struct ocfs2_xattr_value_root *xv =
		(struct ocfs2_xattr_value_root *)et->private;

	xv->xr_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_xattr_value_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
	struct ocfs2_xattr_value_root *xv =
		(struct ocfs2_xattr_value_root *) et->private;

	return le64_to_cpu(xv->xr_last_eb_blk);
}

static void ocfs2_xattr_value_update_clusters(struct inode *inode,
					      struct ocfs2_extent_tree *et,
					      u32 clusters)
{
	struct ocfs2_xattr_value_root *xv =
		(struct ocfs2_xattr_value_root *)et->private;

	le32_add_cpu(&xv->xr_clusters, clusters);
}

static int ocfs2_xattr_value_sanity_check(struct inode *inode,
					  struct ocfs2_extent_tree *et)
{
	return 0;
}

static struct ocfs2_extent_tree_operations ocfs2_xattr_et_ops = {
	.set_last_eb_blk	= ocfs2_xattr_value_set_last_eb_blk,
	.get_last_eb_blk	= ocfs2_xattr_value_get_last_eb_blk,
	.update_clusters	= ocfs2_xattr_value_update_clusters,
	.sanity_check		= ocfs2_xattr_value_sanity_check,
};

static void ocfs2_xattr_tree_set_last_eb_blk(struct ocfs2_extent_tree *et,
					     u64 blkno)
{
	struct ocfs2_xattr_block *xb =
		(struct ocfs2_xattr_block *) et->root_bh->b_data;
	struct ocfs2_xattr_tree_root *xt = &xb->xb_attrs.xb_root;

	xt->xt_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_xattr_tree_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
	struct ocfs2_xattr_block *xb =
		(struct ocfs2_xattr_block *) et->root_bh->b_data;
	struct ocfs2_xattr_tree_root *xt = &xb->xb_attrs.xb_root;

	return le64_to_cpu(xt->xt_last_eb_blk);
}

static void ocfs2_xattr_tree_update_clusters(struct inode *inode,
					     struct ocfs2_extent_tree *et,
					     u32 clusters)
{
	struct ocfs2_xattr_block *xb =
			(struct ocfs2_xattr_block *)et->root_bh->b_data;

	le32_add_cpu(&xb->xb_attrs.xb_root.xt_clusters, clusters);
}

static int ocfs2_xattr_tree_sanity_check(struct inode *inode,
					 struct ocfs2_extent_tree *et)
{
	return 0;
}

static struct ocfs2_extent_tree_operations ocfs2_xattr_tree_et_ops = {
	.set_last_eb_blk	= ocfs2_xattr_tree_set_last_eb_blk,
	.get_last_eb_blk	= ocfs2_xattr_tree_get_last_eb_blk,
	.update_clusters	= ocfs2_xattr_tree_update_clusters,
	.sanity_check		= ocfs2_xattr_tree_sanity_check,
};

static struct ocfs2_extent_tree*
	 ocfs2_new_extent_tree(struct inode *inode,
			       struct buffer_head *bh,
			       enum ocfs2_extent_tree_type et_type,
			       void *private)
{
	struct ocfs2_extent_tree *et;

	et = kzalloc(sizeof(*et), GFP_NOFS);
	if (!et)
		return NULL;

	et->type = et_type;
	get_bh(bh);
	et->root_bh = bh;
	et->private = private;

	if (et_type == OCFS2_DINODE_EXTENT) {
		et->root_el = &((struct ocfs2_dinode *)bh->b_data)->id2.i_list;
		et->eops = &ocfs2_dinode_et_ops;
	} else if (et_type == OCFS2_XATTR_VALUE_EXTENT) {
		struct ocfs2_xattr_value_root *xv =
			(struct ocfs2_xattr_value_root *) private;
		et->root_el = &xv->xr_list;
		et->eops = &ocfs2_xattr_et_ops;
	} else if (et_type == OCFS2_XATTR_TREE_EXTENT) {
		struct ocfs2_xattr_block *xb =
			(struct ocfs2_xattr_block *)bh->b_data;
		et->root_el = &xb->xb_attrs.xb_root.xt_list;
		et->eops = &ocfs2_xattr_tree_et_ops;
		et->max_leaf_clusters = ocfs2_clusters_for_bytes(inode->i_sb,
						OCFS2_MAX_XATTR_TREE_LEAF_SIZE);
	}

	return et;
}

static void ocfs2_free_extent_tree(struct ocfs2_extent_tree *et)
{
	if (et) {
		brelse(et->root_bh);
		kfree(et);
	}
}

static inline void ocfs2_set_last_eb_blk(struct ocfs2_extent_tree *et,
					 u64 new_last_eb_blk)
{
	et->eops->set_last_eb_blk(et, new_last_eb_blk);
}

static inline u64 ocfs2_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
	return et->eops->get_last_eb_blk(et);
}

static inline void ocfs2_update_clusters(struct inode *inode,
					 struct ocfs2_extent_tree *et,
					 u32 clusters)
{
	et->eops->update_clusters(inode, et, clusters);
}

static void ocfs2_free_truncate_context(struct ocfs2_truncate_context *tc);
static int ocfs2_cache_extent_block_free(struct ocfs2_cached_dealloc_ctxt *ctxt,
					 struct ocfs2_extent_block *eb);

/*
 * Structures which describe a path through a btree, and functions to
 * manipulate them.
 *
 * The idea here is to be as generic as possible with the tree
 * manipulation code.
 */
struct ocfs2_path_item {
	struct buffer_head		*bh;
	struct ocfs2_extent_list	*el;
};

#define OCFS2_MAX_PATH_DEPTH	5

struct ocfs2_path {
	int			p_tree_depth;
	struct ocfs2_path_item	p_node[OCFS2_MAX_PATH_DEPTH];
};

#define path_root_bh(_path) ((_path)->p_node[0].bh)
#define path_root_el(_path) ((_path)->p_node[0].el)
#define path_leaf_bh(_path) ((_path)->p_node[(_path)->p_tree_depth].bh)
#define path_leaf_el(_path) ((_path)->p_node[(_path)->p_tree_depth].el)
#define path_num_items(_path) ((_path)->p_tree_depth + 1)

/*
 * 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];

		brelse(node->bh);
		node->bh = 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 = le16_to_cpu(path_root_el(path)->l_tree_depth);

	path->p_tree_depth = depth;
}

static void ocfs2_free_path(struct ocfs2_path *path)
{
	if (path) {
		ocfs2_reinit_path(path, 0);
		kfree(path);
	}
}

/*
 * 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(struct ocfs2_path *dest, struct ocfs2_path *src)
{
	int i;

	BUG_ON(path_root_bh(dest) != path_root_bh(src));
	BUG_ON(path_root_el(dest) != path_root_el(src));

	ocfs2_reinit_path(dest, 1);

	for(i = 1; i < OCFS2_MAX_PATH_DEPTH; i++) {
		dest->p_node[i].bh = src->p_node[i].bh;
		dest->p_node[i].el = src->p_node[i].el;

		if (dest->p_node[i].bh)
			get_bh(dest->p_node[i].bh);
	}
}

/*
 * 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;

	BUG_ON(path_root_bh(dest) != path_root_bh(src));

	for(i = 1; i < OCFS2_MAX_PATH_DEPTH; i++) {
		brelse(dest->p_node[i].bh);

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

		src->p_node[i].bh = NULL;
		src->p_node[i].el = NULL;
	}
}

/*
 * Insert an extent block at given index.
 *
 * This will not take an additional reference on eb_bh.
 */
static inline void ocfs2_path_insert_eb(struct ocfs2_path *path, int index,
					struct buffer_head *eb_bh)
{
	struct ocfs2_extent_block *eb = (struct ocfs2_extent_block *)eb_bh->b_data;

	/*
	 * Right now, no root bh 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.
	 */
	BUG_ON(index == 0);

	path->p_node[index].bh = eb_bh;
	path->p_node[index].el = &eb->h_list;
}

static struct ocfs2_path *ocfs2_new_path(struct buffer_head *root_bh,
					 struct ocfs2_extent_list *root_el)
{
	struct ocfs2_path *path;

	BUG_ON(le16_to_cpu(root_el->l_tree_depth) >= OCFS2_MAX_PATH_DEPTH);

	path = kzalloc(sizeof(*path), GFP_NOFS);
	if (path) {
		path->p_tree_depth = le16_to_cpu(root_el->l_tree_depth);
		get_bh(root_bh);
		path_root_bh(path) = root_bh;
		path_root_el(path) = root_el;
	}

	return path;
}

/*
 * Convenience function to journal all components in a path.
 */
static int ocfs2_journal_access_path(struct inode *inode, handle_t *handle,
				     struct ocfs2_path *path)
{
	int i, ret = 0;

	if (!path)
		goto out;

	for(i = 0; i < path_num_items(path); i++) {
		ret = ocfs2_journal_access(handle, inode, path->p_node[i].bh,
					   OCFS2_JOURNAL_ACCESS_WRITE);
		if (ret < 0) {
			mlog_errno(ret);
			goto out;
		}
	}

out:
	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, u32 v_cluster)
{
	int ret = -1;
	int i;
	struct ocfs2_extent_rec *rec;
	u32 rec_end, rec_start, clusters;

	for(i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
		rec = &el->l_recs[i];

		rec_start = le32_to_cpu(rec->e_cpos);
		clusters = ocfs2_rec_clusters(el, rec);

		rec_end = rec_start + clusters;

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

	return ret;
}

enum ocfs2_contig_type {
	CONTIG_NONE = 0,
	CONTIG_LEFT,
	CONTIG_RIGHT,
	CONTIG_LEFTRIGHT,
};


/*
 * NOTE: ocfs2_block_extent_contig(), ocfs2_extents_adjacent() and
 * ocfs2_extent_contig only work properly against leaf nodes!
 */
static int ocfs2_block_extent_contig(struct super_block *sb,
				     struct ocfs2_extent_rec *ext,
				     u64 blkno)
{
	u64 blk_end = le64_to_cpu(ext->e_blkno);

	blk_end += ocfs2_clusters_to_blocks(sb,
				    le16_to_cpu(ext->e_leaf_clusters));

	return blkno == blk_end;
}

static int ocfs2_extents_adjacent(struct ocfs2_extent_rec *left,
				  struct ocfs2_extent_rec *right)
{
	u32 left_range;

	left_range = le32_to_cpu(left->e_cpos) +
		le16_to_cpu(left->e_leaf_clusters);

	return (left_range == le32_to_cpu(right->e_cpos));
}

static enum ocfs2_contig_type
	ocfs2_extent_contig(struct inode *inode,
			    struct ocfs2_extent_rec *ext,
			    struct ocfs2_extent_rec *insert_rec)
{
	u64 blkno = le64_to_cpu(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(inode->i_sb, ext, blkno))
			return CONTIG_RIGHT;

	blkno = le64_to_cpu(ext->e_blkno);
	if (ocfs2_extents_adjacent(insert_rec, ext) &&
	    ocfs2_block_extent_contig(inode->i_sb, 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;
};

/*
 * How many free extents have we got before we need more meta data?
 */
int ocfs2_num_free_extents(struct ocfs2_super *osb,
			   struct inode *inode,
			   struct buffer_head *root_bh,
			   enum ocfs2_extent_tree_type type,
			   void *private)
{
	int retval;
	struct ocfs2_extent_list *el = NULL;
	struct ocfs2_extent_block *eb;
	struct buffer_head *eb_bh = NULL;
	u64 last_eb_blk = 0;

	mlog_entry_void();

	if (type == OCFS2_DINODE_EXTENT) {
		struct ocfs2_dinode *fe =
				(struct ocfs2_dinode *)root_bh->b_data;
		if (!OCFS2_IS_VALID_DINODE(fe)) {
			OCFS2_RO_ON_INVALID_DINODE(inode->i_sb, fe);
			retval = -EIO;
			goto bail;
		}

		if (fe->i_last_eb_blk)
			last_eb_blk = le64_to_cpu(fe->i_last_eb_blk);
		el = &fe->id2.i_list;
	} else if (type == OCFS2_XATTR_VALUE_EXTENT) {
		struct ocfs2_xattr_value_root *xv =
			(struct ocfs2_xattr_value_root *) private;

		last_eb_blk = le64_to_cpu(xv->xr_last_eb_blk);
		el = &xv->xr_list;
	} else if (type == OCFS2_XATTR_TREE_EXTENT) {
		struct ocfs2_xattr_block *xb =
			(struct ocfs2_xattr_block *)root_bh->b_data;

		last_eb_blk = le64_to_cpu(xb->xb_attrs.xb_root.xt_last_eb_blk);
		el = &xb->xb_attrs.xb_root.xt_list;
	}

	if (last_eb_blk) {
		retval = ocfs2_read_block(osb, last_eb_blk,
					  &eb_bh, OCFS2_BH_CACHED, inode);
		if (retval < 0) {
			mlog_errno(retval);
			goto bail;
		}
		eb = (struct ocfs2_extent_block *) eb_bh->b_data;
		el = &eb->h_list;
	}

	BUG_ON(el->l_tree_depth != 0);

	retval = le16_to_cpu(el->l_count) - le16_to_cpu(el->l_next_free_rec);
bail:
	if (eb_bh)
		brelse(eb_bh);

	mlog_exit(retval);
	return retval;
}

/* expects array to already be allocated
 *
 * sets h_signature, h_blkno, h_suballoc_bit, h_suballoc_slot, and
 * l_count for you
 */
static int ocfs2_create_new_meta_bhs(struct ocfs2_super *osb,
				     handle_t *handle,
				     struct inode *inode,
				     int wanted,
				     struct ocfs2_alloc_context *meta_ac,
				     struct buffer_head *bhs[])
{
	int count, status, i;
	u16 suballoc_bit_start;
	u32 num_got;
	u64 first_blkno;
	struct ocfs2_extent_block *eb;

	mlog_entry_void();

	count = 0;
	while (count < wanted) {
		status = ocfs2_claim_metadata(osb,
					      handle,
					      meta_ac,
					      wanted - count,
					      &suballoc_bit_start,
					      &num_got,
					      &first_blkno);
		if (status < 0) {
			mlog_errno(status);
			goto bail;
		}

		for(i = count;  i < (num_got + count); i++) {
			bhs[i] = sb_getblk(osb->sb, first_blkno);
			if (bhs[i] == NULL) {
				status = -EIO;
				mlog_errno(status);
				goto bail;
			}
			ocfs2_set_new_buffer_uptodate(inode, bhs[i]);

			status = ocfs2_journal_access(handle, inode, bhs[i],
						      OCFS2_JOURNAL_ACCESS_CREATE);
			if (status < 0) {
				mlog_errno(status);
				goto bail;
			}

			memset(bhs[i]->b_data, 0, osb->sb->s_blocksize);
			eb = (struct ocfs2_extent_block *) bhs[i]->b_data;
			/* Ok, setup the minimal stuff here. */
			strcpy(eb->h_signature, OCFS2_EXTENT_BLOCK_SIGNATURE);
			eb->h_blkno = cpu_to_le64(first_blkno);
			eb->h_fs_generation = cpu_to_le32(osb->fs_generation);
			eb->h_suballoc_slot = cpu_to_le16(osb->slot_num);
			eb->h_suballoc_bit = cpu_to_le16(suballoc_bit_start);
			eb->h_list.l_count =
				cpu_to_le16(ocfs2_extent_recs_per_eb(osb->sb));

			suballoc_bit_start++;
			first_blkno++;

			/* We'll also be dirtied by the caller, so
			 * this isn't absolutely necessary. */
			status = ocfs2_journal_dirty(handle, bhs[i]);
			if (status < 0) {
				mlog_errno(status);
				goto bail;
			}
		}

		count += num_got;
	}

	status = 0;
bail:
	if (status < 0) {
		for(i = 0; i < wanted; i++) {
			if (bhs[i])
				brelse(bhs[i]);
			bhs[i] = NULL;
		}
	}
	mlog_exit(status);
	return status;
}

/*
 * Helper function for ocfs2_add_branch() and ocfs2_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.
 *
 * ocfs2_shift_tree_depth() uses this to determine the # clusters
 * value for the new topmost tree record.
 */
static inline u32 ocfs2_sum_rightmost_rec(struct ocfs2_extent_list  *el)
{
	int i;

	i = le16_to_cpu(el->l_next_free_rec) - 1;

	return le32_to_cpu(el->l_recs[i].e_cpos) +
		ocfs2_rec_clusters(el, &el->l_recs[i]);
}

/*
 * Add an entire tree branch to our inode. eb_bh is the extent block
 * to start at, if we don't want to start the branch at the dinode
 * structure.
 *
 * last_eb_bh 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 cluster count == 0.
 */
static int ocfs2_add_branch(struct ocfs2_super *osb,
			    handle_t *handle,
			    struct inode *inode,
			    struct ocfs2_extent_tree *et,
			    struct buffer_head *eb_bh,
			    struct buffer_head **last_eb_bh,
			    struct ocfs2_alloc_context *meta_ac)
{
	int status, new_blocks, i;
	u64 next_blkno, new_last_eb_blk;
	struct buffer_head *bh;
	struct buffer_head **new_eb_bhs = NULL;
	struct ocfs2_extent_block *eb;
	struct ocfs2_extent_list  *eb_el;
	struct ocfs2_extent_list  *el;
	u32 new_cpos;

	mlog_entry_void();

	BUG_ON(!last_eb_bh || !*last_eb_bh);

	if (eb_bh) {
		eb = (struct ocfs2_extent_block *) eb_bh->b_data;
		el = &eb->h_list;
	} else
		el = et->root_el;

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

	new_blocks = le16_to_cpu(el->l_tree_depth);

	/* allocate the number of new eb blocks we need */
	new_eb_bhs = kcalloc(new_blocks, sizeof(struct buffer_head *),
			     GFP_KERNEL);
	if (!new_eb_bhs) {
		status = -ENOMEM;
		mlog_errno(status);
		goto bail;
	}

	status = ocfs2_create_new_meta_bhs(osb, handle, inode, new_blocks,
					   meta_ac, new_eb_bhs);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

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

	/* Note: new_eb_bhs[new_blocks - 1] is the guy which will be
	 * linked with the rest of the tree.
	 * conversly, new_eb_bhs[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++) {
		bh = new_eb_bhs[i];
		eb = (struct ocfs2_extent_block *) bh->b_data;
		if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
			OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
			status = -EIO;
			goto bail;
		}
		eb_el = &eb->h_list;

		status = ocfs2_journal_access(handle, inode, bh,
					      OCFS2_JOURNAL_ACCESS_CREATE);
		if (status < 0) {
			mlog_errno(status);
			goto bail;
		}

		eb->h_next_leaf_blk = 0;
		eb_el->l_tree_depth = cpu_to_le16(i);
		eb_el->l_next_free_rec = cpu_to_le16(1);
		/*
		 * This actually counts as an empty extent as
		 * c_clusters == 0
		 */
		eb_el->l_recs[0].e_cpos = cpu_to_le32(new_cpos);
		eb_el->l_recs[0].e_blkno = cpu_to_le64(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 = cpu_to_le32(0);
		if (!eb_el->l_tree_depth)
			new_last_eb_blk = le64_to_cpu(eb->h_blkno);

		status = ocfs2_journal_dirty(handle, bh);
		if (status < 0) {
			mlog_errno(status);
			goto bail;
		}

		next_blkno = le64_to_cpu(eb->h_blkno);
	}

	/* This is a bit hairy. We want to update up to three blocks
	 * here without leaving any of them in an inconsistent state
	 * in case of error. We don't have to worry about
	 * journal_dirty erroring as it won't unless we've aborted the
	 * handle (in which case we would never be here) so reserving
	 * the write with journal_access is all we need to do. */
	status = ocfs2_journal_access(handle, inode, *last_eb_bh,
				      OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}
	status = ocfs2_journal_access(handle, inode, et->root_bh,
				      OCFS2_JOURNAL_ACCESS_WRITE);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}
	if (eb_bh) {
		status = ocfs2_journal_access(handle, inode, eb_bh,
					      OCFS2_JOURNAL_ACCESS_WRITE);
		if (status < 0) {
			mlog_errno(status);
			goto bail;
		}
	}

	/* Link the new branch into the rest of the tree (el will
	 * either be on the root_bh, or the extent block passed in. */
	i = le16_to_cpu(el->l_next_free_rec);
	el->l_recs[i].e_blkno = cpu_to_le64(next_blkno);
	el->l_recs[i].e_cpos = cpu_to_le32(new_cpos);
	el->l_recs[i].e_int_clusters = 0;
	le16_add_cpu(&el->l_next_free_rec, 1);

	/* fe needs a new last extent block pointer, as does the
	 * next_leaf on the previously last-extent-block. */
	ocfs2_set_last_eb_blk(et, new_last_eb_blk);

	eb = (struct ocfs2_extent_block *) (*last_eb_bh)->b_data;
	eb->h_next_leaf_blk = cpu_to_le64(new_last_eb_blk);

	status = ocfs2_journal_dirty(handle, *last_eb_bh);
	if (status < 0)
		mlog_errno(status);
	status = ocfs2_journal_dirty(handle, et->root_bh);
	if (status < 0)
		mlog_errno(status);
	if (eb_bh) {
		status = ocfs2_journal_dirty(handle, eb_bh);
		if (status < 0)
			mlog_errno(status);
	}

	/*
	 * Some callers want to track the rightmost leaf so pass it
	 * back here.
	 */
	brelse(*last_eb_bh);
	get_bh(new_eb_bhs[0]);
	*last_eb_bh = new_eb_bhs[0];

	status = 0;
bail:
	if (new_eb_bhs) {
		for (i = 0; i < new_blocks; i++)
			if (new_eb_bhs[i])
				brelse(new_eb_bhs[i]);
		kfree(new_eb_bhs);
	}

	mlog_exit(status);
	return status;
}

/*
 * adds another level to the allocation tree.
 * returns back the new extent block so you can add a branch to it
 * after this call.
 */
static int ocfs2_shift_tree_depth(struct ocfs2_super *osb,
				  handle_t *handle,
				  struct inode *inode,
				  struct ocfs2_extent_tree *et,
				  struct ocfs2_alloc_context *meta_ac,
				  struct buffer_head **ret_new_eb_bh)
{
	int status, i;
	u32 new_clusters;
	struct buffer_head *new_eb_bh = NULL;
	struct ocfs2_extent_block *eb;
	struct ocfs2_extent_list  *root_el;
	struct ocfs2_extent_list  *eb_el;

	mlog_entry_void();

	status = ocfs2_create_new_meta_bhs(osb, handle, inode, 1, meta_ac,
					   &new_eb_bh);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	eb = (struct ocfs2_extent_block *) new_eb_bh->b_data;
	if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
		OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
		status = -EIO;
		goto bail;
	}

	eb_el = &eb->h_list;
	root_el = et->root_el;

	status = ocfs2_journal_access(handle, inode, new_eb_bh,
				      OCFS2_JOURNAL_ACCESS_CREATE);
	if (status < 0) {
		mlog_errno(status);
		goto bail;
	}

	/* copy the root extent list data into the new extent block */
	eb_el->l_tree_depth = root_el->l_tree_depth;