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>
#include <linux/quotaops.h>

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

#include "ocfs2.h"

#include "alloc.h"
#include "aops.h"
#include "blockcheck.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"


/*
 * Operations for a specific extent tree type.
 *
 * To implement an on-disk btree (extent tree) type in ocfs2, add
 * an ocfs2_extent_tree_operations structure and the matching
 * ocfs2_init_<thingy>_extent_tree() function.  That's pretty much it
 * for the allocation portion of the extent tree.
 */
struct ocfs2_extent_tree_operations {
	/*
	 * last_eb_blk is the block number of the right most leaf extent
	 * block.  Most on-disk structures containing an extent tree store
	 * this value for fast access.  The ->eo_set_last_eb_blk() and
	 * ->eo_get_last_eb_blk() operations access this value.  They are
	 *  both required.
	 */
	void (*eo_set_last_eb_blk)(struct ocfs2_extent_tree *et,
				   u64 blkno);
	u64 (*eo_get_last_eb_blk)(struct ocfs2_extent_tree *et);

	/*
	 * The on-disk structure usually keeps track of how many total
	 * clusters are stored in this extent tree.  This function updates
	 * that value.  new_clusters is the delta, and must be
	 * added to the total.  Required.
	 */
	void (*eo_update_clusters)(struct inode *inode,
				   struct ocfs2_extent_tree *et,
				   u32 new_clusters);

	/*
	 * If ->eo_insert_check() exists, it is called before rec is
	 * inserted into the extent tree.  It is optional.
	 */
	int (*eo_insert_check)(struct inode *inode,
			       struct ocfs2_extent_tree *et,
			       struct ocfs2_extent_rec *rec);
	int (*eo_sanity_check)(struct inode *inode, struct ocfs2_extent_tree *et);

	/*
	 * --------------------------------------------------------------
	 * The remaining are internal to ocfs2_extent_tree and don't have
	 * accessor functions
	 */

	/*
	 * ->eo_fill_root_el() takes et->et_object and sets et->et_root_el.
	 * It is required.
	 */
	void (*eo_fill_root_el)(struct ocfs2_extent_tree *et);

	/*
	 * ->eo_fill_max_leaf_clusters sets et->et_max_leaf_clusters if
	 * it exists.  If it does not, et->et_max_leaf_clusters is set
	 * to 0 (unlimited).  Optional.
	 */
	void (*eo_fill_max_leaf_clusters)(struct inode *inode,
					  struct ocfs2_extent_tree *et);
};


/*
 * Pre-declare ocfs2_dinode_et_ops so we can use it as a sanity check
 * in the methods.
 */
static u64 ocfs2_dinode_get_last_eb_blk(struct ocfs2_extent_tree *et);
static void ocfs2_dinode_set_last_eb_blk(struct ocfs2_extent_tree *et,
					 u64 blkno);
static void ocfs2_dinode_update_clusters(struct inode *inode,
					 struct ocfs2_extent_tree *et,
					 u32 clusters);
static int ocfs2_dinode_insert_check(struct inode *inode,
				     struct ocfs2_extent_tree *et,
				     struct ocfs2_extent_rec *rec);
static int ocfs2_dinode_sanity_check(struct inode *inode,
				     struct ocfs2_extent_tree *et);
static void ocfs2_dinode_fill_root_el(struct ocfs2_extent_tree *et);
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_insert_check	= ocfs2_dinode_insert_check,
	.eo_sanity_check	= ocfs2_dinode_sanity_check,
	.eo_fill_root_el	= ocfs2_dinode_fill_root_el,
};

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

	BUG_ON(et->et_ops != &ocfs2_dinode_et_ops);
	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 = et->et_object;

	BUG_ON(et->et_ops != &ocfs2_dinode_et_ops);
	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 = et->et_object;

	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_insert_check(struct inode *inode,
				     struct ocfs2_extent_tree *et,
				     struct ocfs2_extent_rec *rec)
{
	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

	BUG_ON(OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL);
	mlog_bug_on_msg(!ocfs2_sparse_alloc(osb) &&
			(OCFS2_I(inode)->ip_clusters != rec->e_cpos),
			"Device %s, asking for sparse allocation: inode %llu, "
			"cpos %u, clusters %u\n",
			osb->dev_str,
			(unsigned long long)OCFS2_I(inode)->ip_blkno,
			rec->e_cpos,
			OCFS2_I(inode)->ip_clusters);

	return 0;
}

static int ocfs2_dinode_sanity_check(struct inode *inode,
				     struct ocfs2_extent_tree *et)
{
	struct ocfs2_dinode *di = et->et_object;

	BUG_ON(et->et_ops != &ocfs2_dinode_et_ops);
	BUG_ON(!OCFS2_IS_VALID_DINODE(di));

	return 0;
}

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 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,
					      u64 blkno)
{
	struct ocfs2_xattr_value_root *xv =
		(struct ocfs2_xattr_value_root *)et->et_object;

	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->et_object;

	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->et_object;

	le32_add_cpu(&xv->xr_clusters, 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_fill_root_el	= ocfs2_xattr_value_fill_root_el,
};

static void ocfs2_xattr_tree_fill_root_el(struct ocfs2_extent_tree *et)
{
	struct ocfs2_xattr_block *xb = et->et_object;

	et->et_root_el = &xb->xb_attrs.xb_root.xt_list;
}

static void ocfs2_xattr_tree_fill_max_leaf_clusters(struct inode *inode,
						    struct ocfs2_extent_tree *et)
{
	et->et_max_leaf_clusters =
		ocfs2_clusters_for_bytes(inode->i_sb,
					 OCFS2_MAX_XATTR_TREE_LEAF_SIZE);
}

static void ocfs2_xattr_tree_set_last_eb_blk(struct ocfs2_extent_tree *et,
					     u64 blkno)
{
	struct ocfs2_xattr_block *xb = et->et_object;
	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 = et->et_object;
	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 = et->et_object;

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

static struct ocfs2_extent_tree_operations ocfs2_xattr_tree_et_ops = {
	.eo_set_last_eb_blk	= ocfs2_xattr_tree_set_last_eb_blk,
	.eo_get_last_eb_blk	= ocfs2_xattr_tree_get_last_eb_blk,
	.eo_update_clusters	= ocfs2_xattr_tree_update_clusters,
	.eo_fill_root_el	= ocfs2_xattr_tree_fill_root_el,
	.eo_fill_max_leaf_clusters = ocfs2_xattr_tree_fill_max_leaf_clusters,
};

static void __ocfs2_init_extent_tree(struct ocfs2_extent_tree *et,
				     struct inode *inode,
				     struct buffer_head *bh,
				     ocfs2_journal_access_func access,
				     void *obj,
				     struct ocfs2_extent_tree_operations *ops)
{
	et->et_ops = ops;
	et->et_root_bh = bh;
	et->et_root_journal_access = access;
	if (!obj)
		obj = (void *)bh->b_data;
	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(inode, et);
}

void ocfs2_init_dinode_extent_tree(struct ocfs2_extent_tree *et,
				   struct inode *inode,
				   struct buffer_head *bh)
{
	__ocfs2_init_extent_tree(et, inode, bh, ocfs2_journal_access_di,
				 NULL, &ocfs2_dinode_et_ops);
}

void ocfs2_init_xattr_tree_extent_tree(struct ocfs2_extent_tree *et,
				       struct inode *inode,
				       struct buffer_head *bh)
{
	__ocfs2_init_extent_tree(et, inode, bh, ocfs2_journal_access_xb,
				 NULL, &ocfs2_xattr_tree_et_ops);
}

void ocfs2_init_xattr_value_extent_tree(struct ocfs2_extent_tree *et,
					struct inode *inode,
					struct buffer_head *bh,
					struct ocfs2_xattr_value_root *xv)
{
	__ocfs2_init_extent_tree(et, inode, bh, ocfs2_journal_access, xv,
				 &ocfs2_xattr_value_et_ops);
}

static inline void ocfs2_et_set_last_eb_blk(struct ocfs2_extent_tree *et,
					    u64 new_last_eb_blk)
{
	et->et_ops->eo_set_last_eb_blk(et, new_last_eb_blk);
}

static inline u64 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 inode *inode,
					    struct ocfs2_extent_tree *et,
					    u32 clusters)
{
	et->et_ops->eo_update_clusters(inode, et, clusters);
}

static inline int ocfs2_et_root_journal_access(handle_t *handle,
					       struct inode *inode,
					       struct ocfs2_extent_tree *et,
					       int type)
{
	return et->et_root_journal_access(handle, inode, et->et_root_bh,
					  type);
}

static inline int ocfs2_et_insert_check(struct inode *inode,
					struct ocfs2_extent_tree *et,
					struct ocfs2_extent_rec *rec)
{
	int ret = 0;

	if (et->et_ops->eo_insert_check)
		ret = et->et_ops->eo_insert_check(inode, et, rec);
	return ret;
}

static inline int ocfs2_et_sanity_check(struct inode *inode,
					struct ocfs2_extent_tree *et)
{
	int ret = 0;

	if (et->et_ops->eo_sanity_check)
		ret = et->et_ops->eo_sanity_check(inode, et);
	return ret;
}

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;
	ocfs2_journal_access_func	p_root_access;
	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_root_access(_path)((_path)->p_root_access)
#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);
	else
		path_root_access(path) = NULL;

	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));
	BUG_ON(path_root_access(dest) != path_root_access(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));
	BUG_ON(path_root_access(dest) != path_root_access(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,
					 ocfs2_journal_access_func access)
{
	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;
		path_root_access(path) = access;
	}

	return path;
}

static struct ocfs2_path *ocfs2_new_path_from_path(struct ocfs2_path *path)
{
	return ocfs2_new_path(path_root_bh(path), path_root_el(path),
			      path_root_access(path));
}

static struct ocfs2_path *ocfs2_new_path_from_et(struct ocfs2_extent_tree *et)
{
	return ocfs2_new_path(et->et_root_bh, et->et_root_el,
			      et->et_root_journal_access);
}

/*
 * Journal the buffer at depth idx.  All idx>0 are extent_blocks,
 * otherwise it's the root_access function.
 *
 * I don't like the way this function's name looks next to
 * ocfs2_journal_access_path(), but I don't have a better one.
 */
static int ocfs2_path_bh_journal_access(handle_t *handle,
					struct inode *inode,
					struct ocfs2_path *path,
					int idx)
{
	ocfs2_journal_access_func access = path_root_access(path);

	if (!access)
		access = ocfs2_journal_access;

	if (idx)
		access = ocfs2_journal_access_eb;

	return access(handle, inode, path->p_node[idx].bh,
		      OCFS2_JOURNAL_ACCESS_WRITE);
}

/*
 * 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_path_bh_journal_access(handle, inode, path, i);
		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;
};

static int ocfs2_validate_extent_block(struct super_block *sb,
				       struct buffer_head *bh)
{
	int rc;
	struct ocfs2_extent_block *eb =
		(struct ocfs2_extent_block *)bh->b_data;

	mlog(0, "Validating extent block %llu\n",
	     (unsigned long long)bh->b_blocknr);

	BUG_ON(!buffer_uptodate(bh));

	/*
	 * If the ecc fails, we return the error but otherwise
	 * leave the filesystem running.  We know any error is
	 * local to this block.
	 */
	rc = ocfs2_validate_meta_ecc(sb, bh->b_data, &eb->h_check);
	if (rc) {
		mlog(ML_ERROR, "Checksum failed for extent block %llu\n",
		     (unsigned long long)bh->b_blocknr);
		return rc;
	}

	/*
	 * Errors after here are fatal.
	 */

	if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
		ocfs2_error(sb,
			    "Extent block #%llu has bad signature %.*s",
			    (unsigned long long)bh->b_blocknr, 7,
			    eb->h_signature);
		return -EINVAL;
	}

	if (le64_to_cpu(eb->h_blkno) != bh->b_blocknr) {
		ocfs2_error(sb,
			    "Extent block #%llu has an invalid h_blkno "
			    "of %llu",
			    (unsigned long long)bh->b_blocknr,
			    (unsigned long long)le64_to_cpu(eb->h_blkno));
		return -EINVAL;
	}

	if (le32_to_cpu(eb->h_fs_generation) != OCFS2_SB(sb)->fs_generation) {
		ocfs2_error(sb,
			    "Extent block #%llu has an invalid "
			    "h_fs_generation of #%u",
			    (unsigned long long)bh->b_blocknr,
			    le32_to_cpu(eb->h_fs_generation));
		return -EINVAL;
	}

	return 0;
}

int ocfs2_read_extent_block(struct inode *inode, u64 eb_blkno,
			    struct buffer_head **bh)
{
	int rc;
	struct buffer_head *tmp = *bh;

	rc = ocfs2_read_block(inode, eb_blkno, &tmp,
			      ocfs2_validate_extent_block);

	/* If ocfs2_read_block() got us a new bh, pass it up. */
	if (!rc && !*bh)
		*bh = tmp;

	return rc;
}


/*
 * 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 ocfs2_extent_tree *et)
{
	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();

	el = et->et_root_el;
	last_eb_blk = ocfs2_et_get_last_eb_blk(et);

	if (last_eb_blk) {
		retval = ocfs2_read_extent_block(inode, last_eb_blk, &eb_bh);
		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:
	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_eb(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++) {
			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->et_root_el;

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