/* -*- 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>
#include <linux/blkdev.h>

#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 "xattr.h"
#include "refcounttree.h"
#include "ocfs2_trace.h"

#include "buffer_head_io.h"

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

static enum ocfs2_contig_type
        ocfs2_extent_rec_contig(struct super_block *sb,
                                struct ocfs2_extent_rec *ext,
                                struct ocfs2_extent_rec *insert_rec);
/*
 * 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 ocfs2_extent_tree *et,
                                   u32 new_clusters);

        /*
         * If this extent tree is supported by an extent map, insert
         * a record into the map.
         */
        void (*eo_extent_map_insert)(struct ocfs2_extent_tree *et,
                                     struct ocfs2_extent_rec *rec);

        /*
         * If this extent tree is supported by an extent map, truncate the
         * map to clusters,
         */
        void (*eo_extent_map_truncate)(struct ocfs2_extent_tree *et,
                                       u32 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 ocfs2_extent_tree *et,
                               struct ocfs2_extent_rec *rec);
        int (*eo_sanity_check)(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 ocfs2_extent_tree *et);

        /*
         * ->eo_extent_contig test whether the 2 ocfs2_extent_rec
         * are contiguous or not. Optional. Don't need to set it if use
         * ocfs2_extent_rec as the tree leaf.
         */
        enum ocfs2_contig_type
                (*eo_extent_contig)(struct ocfs2_extent_tree *et,
                                    struct ocfs2_extent_rec *ext,
                                    struct ocfs2_extent_rec *insert_rec);
};


/*
 * 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 ocfs2_extent_tree *et,
                                         u32 clusters);
static void ocfs2_dinode_extent_map_insert(struct ocfs2_extent_tree *et,
                                           struct ocfs2_extent_rec *rec);
static void ocfs2_dinode_extent_map_truncate(struct ocfs2_extent_tree *et,
                                             u32 clusters);
static int ocfs2_dinode_insert_check(struct ocfs2_extent_tree *et,
                                     struct ocfs2_extent_rec *rec);
static int ocfs2_dinode_sanity_check(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_extent_map_insert   = ocfs2_dinode_extent_map_insert,
        .eo_extent_map_truncate = ocfs2_dinode_extent_map_truncate,
        .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 ocfs2_extent_tree *et,
                                         u32 clusters)
{
        struct ocfs2_inode_info *oi = cache_info_to_inode(et->et_ci);
        struct ocfs2_dinode *di = et->et_object;

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

static void ocfs2_dinode_extent_map_insert(struct ocfs2_extent_tree *et,
                                           struct ocfs2_extent_rec *rec)
{
        struct inode *inode = &cache_info_to_inode(et->et_ci)->vfs_inode;

        ocfs2_extent_map_insert_rec(inode, rec);
}

static void ocfs2_dinode_extent_map_truncate(struct ocfs2_extent_tree *et,
                                             u32 clusters)
{
        struct inode *inode = &cache_info_to_inode(et->et_ci)->vfs_inode;

        ocfs2_extent_map_trunc(inode, clusters);
}

static int ocfs2_dinode_insert_check(struct ocfs2_extent_tree *et,
                                     struct ocfs2_extent_rec *rec)
{
        struct ocfs2_inode_info *oi = cache_info_to_inode(et->et_ci);
        struct ocfs2_super *osb = OCFS2_SB(oi->vfs_inode.i_sb);

        BUG_ON(oi->ip_dyn_features & OCFS2_INLINE_DATA_FL);
        mlog_bug_on_msg(!ocfs2_sparse_alloc(osb) &&
                        (oi->ip_clusters != le32_to_cpu(rec->e_cpos)),
                        "Device %s, asking for sparse allocation: inode %llu, "
                        "cpos %u, clusters %u\n",
                        osb->dev_str,
                        (unsigned long long)oi->ip_blkno,
                        rec->e_cpos, oi->ip_clusters);

        return 0;
}

static int ocfs2_dinode_sanity_check(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_buf *vb = et->et_object;

        et->et_root_el = &vb->vb_xv->xr_list;
}

static void ocfs2_xattr_value_set_last_eb_blk(struct ocfs2_extent_tree *et,
                                              u64 blkno)
{
        struct ocfs2_xattr_value_buf *vb = et->et_object;

        vb->vb_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_buf *vb = et->et_object;

        return le64_to_cpu(vb->vb_xv->xr_last_eb_blk);
}

static void ocfs2_xattr_value_update_clusters(struct ocfs2_extent_tree *et,
                                              u32 clusters)
{
        struct ocfs2_xattr_value_buf *vb = et->et_object;

        le32_add_cpu(&vb->vb_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 ocfs2_extent_tree *et)
{
        struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);
        et->et_max_leaf_clusters =
                ocfs2_clusters_for_bytes(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 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_dx_root_set_last_eb_blk(struct ocfs2_extent_tree *et,
                                          u64 blkno)
{
        struct ocfs2_dx_root_block *dx_root = et->et_object;

        dx_root->dr_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_dx_root_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
        struct ocfs2_dx_root_block *dx_root = et->et_object;

        return le64_to_cpu(dx_root->dr_last_eb_blk);
}

static void ocfs2_dx_root_update_clusters(struct ocfs2_extent_tree *et,
                                          u32 clusters)
{
        struct ocfs2_dx_root_block *dx_root = et->et_object;

        le32_add_cpu(&dx_root->dr_clusters, clusters);
}

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

        BUG_ON(!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_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,
                                                u64 blkno)
{
        struct ocfs2_refcount_block *rb = et->et_object;

        rb->rf_last_eb_blk = cpu_to_le64(blkno);
}

static u64 ocfs2_refcount_tree_get_last_eb_blk(struct ocfs2_extent_tree *et)
{
        struct ocfs2_refcount_block *rb = et->et_object;

        return le64_to_cpu(rb->rf_last_eb_blk);
}

static void ocfs2_refcount_tree_update_clusters(struct ocfs2_extent_tree *et,
                                                u32 clusters)
{
        struct ocfs2_refcount_block *rb = et->et_object;

        le32_add_cpu(&rb->rf_clusters, clusters);
}

static enum ocfs2_contig_type
ocfs2_refcount_tree_extent_contig(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_init_extent_tree(struct ocfs2_extent_tree *et,
                                     struct ocfs2_caching_info *ci,
                                     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_ci = ci;
        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(et);
}

void ocfs2_init_dinode_extent_tree(struct ocfs2_extent_tree *et,
                                   struct ocfs2_caching_info *ci,
                                   struct buffer_head *bh)
{
        __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_di,
                                 NULL, &ocfs2_dinode_et_ops);
}

void ocfs2_init_xattr_tree_extent_tree(struct ocfs2_extent_tree *et,
                                       struct ocfs2_caching_info *ci,
                                       struct buffer_head *bh)
{
        __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_xb,
                                 NULL, &ocfs2_xattr_tree_et_ops);
}

void ocfs2_init_xattr_value_extent_tree(struct ocfs2_extent_tree *et,
                                        struct ocfs2_caching_info *ci,
                                        struct ocfs2_xattr_value_buf *vb)
{
        __ocfs2_init_extent_tree(et, ci, vb->vb_bh, vb->vb_access, vb,
                                 &ocfs2_xattr_value_et_ops);
}

void ocfs2_init_dx_root_extent_tree(struct ocfs2_extent_tree *et,
                                    struct ocfs2_caching_info *ci,
                                    struct buffer_head *bh)
{
        __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_dr,
                                 NULL, &ocfs2_dx_root_et_ops);
}

void ocfs2_init_refcount_extent_tree(struct ocfs2_extent_tree *et,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *bh)
{
        __ocfs2_init_extent_tree(et, ci, bh, ocfs2_journal_access_rb,
                                 NULL, &ocfs2_refcount_tree_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 ocfs2_extent_tree *et,
                                            u32 clusters)
{
        et->et_ops->eo_update_clusters(et, clusters);
}

static inline void ocfs2_et_extent_map_insert(struct ocfs2_extent_tree *et,
                                              struct ocfs2_extent_rec *rec)
{
        if (et->et_ops->eo_extent_map_insert)
                et->et_ops->eo_extent_map_insert(et, rec);
}

static inline void ocfs2_et_extent_map_truncate(struct ocfs2_extent_tree *et,
                                                u32 clusters)
{
        if (et->et_ops->eo_extent_map_truncate)
                et->et_ops->eo_extent_map_truncate(et, clusters);
}

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

static inline enum ocfs2_contig_type
        ocfs2_et_extent_contig(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(et, rec, insert_rec);

        return ocfs2_extent_rec_contig(
                                ocfs2_metadata_cache_get_super(et->et_ci),
                                rec, insert_rec);
}

static inline int ocfs2_et_insert_check(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(et, rec);
        return ret;
}

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

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

static int ocfs2_cache_extent_block_free(struct ocfs2_cached_dealloc_ctxt *ctxt,
                                         struct ocfs2_extent_block *eb);
static void ocfs2_adjust_rightmost_records(handle_t *handle,
                                           struct ocfs2_extent_tree *et,
                                           struct ocfs2_path *path,
                                           struct ocfs2_extent_rec *insert_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.
 */
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;
}

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;
}

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));
}

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.
 */
int ocfs2_path_bh_journal_access(handle_t *handle,
                                 struct ocfs2_caching_info *ci,
                                 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, ci, path->p_node[idx].bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
}

/*
 * Convenience function to journal all components in a path.
 */
int ocfs2_journal_access_path(struct ocfs2_caching_info *ci,
                              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, ci, 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;
}

/*
 * NOTE: ocfs2_block_extent_contig(), ocfs2_extents_adjacent() and
 * ocfs2_extent_rec_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_rec_contig(struct super_block *sb,
                                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(sb, ext, blkno))
                        return CONTIG_RIGHT;

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

        trace_ocfs2_validate_extent_block((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)) {
                rc = ocfs2_error(sb,
                                 "Extent block #%llu has bad signature %.*s\n",
                                 (unsigned long long)bh->b_blocknr, 7,
                                 eb->h_signature);
                goto bail;
        }

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

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

int ocfs2_read_extent_block(struct ocfs2_caching_info *ci, u64 eb_blkno,
                            struct buffer_head **bh)
{
        int rc;
        struct buffer_head *tmp = *bh;

        rc = ocfs2_read_block(ci, 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 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;

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

        if (last_eb_blk) {
                retval = ocfs2_read_extent_block(et->et_ci, 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);

        trace_ocfs2_num_free_extents(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(handle_t *handle,
                                     struct ocfs2_extent_tree *et,
                                     int wanted,
                                     struct ocfs2_alloc_context *meta_ac,
                                     struct buffer_head *bhs[])
{

        int count, status, i;
        u16 suballoc_bit_start;
        u32 num_got;
        u64 suballoc_loc, first_blkno;
        struct ocfs2_super *osb =
                OCFS2_SB(ocfs2_metadata_cache_get_super(et->et_ci));
        struct ocfs2_extent_block *eb;

        count = 0;
        while (count < wanted) {
                status = ocfs2_claim_metadata(handle,
                                              meta_ac,
                                              wanted - count,
                                              &suballoc_loc,
                                              &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 = -ENOMEM;
                                mlog_errno(status);
                                goto bail;
                        }
                        ocfs2_set_new_buffer_uptodate(et->et_ci, bhs[i]);

                        status = ocfs2_journal_access_eb(handle, et->et_ci,
                                                         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(meta_ac->ac_alloc_slot);
                        eb->h_suballoc_loc = cpu_to_le64(suballoc_loc);
                        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. */
                        ocfs2_journal_dirty(handle, bhs[i]);
                }

                count += num_got;
        }

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

/*
 * Change range of the branches in the right most path according to the leaf
 * extent block's rightmost record.
 */
static int ocfs2_adjust_rightmost_branch(handle_t *handle,
                                         struct ocfs2_extent_tree *et)
{
        int status;
        struct ocfs2_path *path = NULL;
        struct ocfs2_extent_list *el;
        struct ocfs2_extent_rec *rec;

        path = ocfs2_new_path_from_et(et);
        if (!path) {
                status = -ENOMEM;
                return status;
        }

        status = ocfs2_find_path(et->et_ci, path, UINT_MAX);
        if (status < 0) {
                mlog_errno(status);
                goto out;
        }

        status = ocfs2_extend_trans(handle, path_num_items(path));
        if (status < 0) {
                mlog_errno(status);
                goto out;
        }

        status = ocfs2_journal_access_path(et->et_ci, handle, path);
        if (status < 0) {
                mlog_errno(status);
                goto out;
        }

        el = path_leaf_el(path);
        rec = &el->l_recs[le16_to_cpu(el->l_next_free_rec) - 1];

        ocfs2_adjust_rightmost_records(handle, et, path, rec);

out:
        ocfs2_free_path(path);
        return status;
}

/*
 * 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 root
 * 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(handle_t *handle,
                            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, root_end;

        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);

        new_blocks = le16_to_cpu(el->l_tree_depth);

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

        /*
         * If there is a gap before the root end and the real end
         * of the righmost leaf block, we need to remove the gap
         * between new_cpos and root_end first so that the tree
         * is consistent after we add a new branch(it will start
         * from new_cpos).
         */
        if (root_end > new_cpos) {
                trace_ocfs2_adjust_rightmost_branch(
                        (unsigned long long)
                        ocfs2_metadata_cache_owner(et->et_ci),
                        root_end, new_cpos);

                status = ocfs2_adjust_rightmost_branch(handle, et);
                if (status) {
                        mlog_errno(status);
                        goto bail;
                }
        }

        /* 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(handle, et, new_blocks,
                                           meta_ac, new_eb_bhs);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        /* 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;
                /* ocfs2_create_new_meta_bhs() should create it right! */
                BUG_ON(!OCFS2_IS_VALID_EXTENT_BLOCK(eb));
                eb_el = &eb->h_list;

                status = ocfs2_journal_access_eb(handle, et->et_ci, 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);

                ocfs2_journal_dirty(handle, bh);
                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_eb(handle, et->et_ci, *last_eb_bh,
                                         OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }
        status = ocfs2_et_root_journal_access(handle, et,
                                              OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }
        if (eb_bh) {
                status = ocfs2_journal_access_eb(handle, et->et_ci, 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_et_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);

        ocfs2_journal_dirty(handle, *last_eb_bh);
        ocfs2_journal_dirty(handle, et->et_root_bh);
        if (eb_bh)
                ocfs2_journal_dirty(handle, eb_bh);

        /*
         * 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++)
                        brelse(new_eb_bhs[i]);
                kfree(new_eb_bhs);
        }

        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(handle_t *handle,
                                  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;

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

        eb = (struct ocfs2_extent_block *) new_eb_bh->b_data;
        /* ocfs2_create_new_meta_bhs() should create it right! */
        BUG_ON(!OCFS2_IS_VALID_EXTENT_BLOCK(eb));

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

        status = ocfs2_journal_access_eb(handle, et->et_ci, 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;
        eb_el->l_next_free_rec = root_el->l_next_free_rec;
        for (i = 0; i < le16_to_cpu(root_el->l_next_free_rec); i++)
                eb_el->l_recs[i] = root_el->l_recs[i];

        ocfs2_journal_dirty(handle, new_eb_bh);

        status = ocfs2_et_root_journal_access(handle, et,
                                              OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        new_clusters = ocfs2_sum_rightmost_rec(eb_el);

        /* update root_bh now */
        le16_add_cpu(&root_el->l_tree_depth, 1);
        root_el->l_recs[0].e_cpos = 0;
        root_el->l_recs[0].e_blkno = eb->h_blkno;
        root_el->l_recs[0].e_int_clusters = cpu_to_le32(new_clusters);
        for (i = 1; i < le16_to_cpu(root_el->l_next_free_rec); i++)
                memset(&root_el->l_recs[i], 0, sizeof(struct ocfs2_extent_rec));
        root_el->l_next_free_rec = cpu_to_le16(1);

        /* If this is our 1st tree depth shift, then last_eb_blk
         * becomes the allocated extent block */
        if (root_el->l_tree_depth == cpu_to_le16(1))
                ocfs2_et_set_last_eb_blk(et, le64_to_cpu(eb->h_blkno));

        ocfs2_journal_dirty(handle, et->et_root_bh);

        *ret_new_eb_bh = new_eb_bh;
        new_eb_bh = NULL;
        status = 0;
bail:
        brelse(new_eb_bh);

        return status;
}

/*
 * 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
 *    *lowest_eb_bh and return '0'
 *
 * 2) the search fails to find anything, but the root_el has room. We
 *    pass NULL back in *lowest_eb_bh, but still return '0'
 *
 * 3) the search fails to find anything AND the root_el is full, in
 *    which case we return > 0
 *
 * return status < 0 indicates an error.
 */
static int ocfs2_find_branch_target(struct ocfs2_extent_tree *et,
                                    struct buffer_head **target_bh)
{
        int status = 0, i;
        u64 blkno;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list  *el;
        struct buffer_head *bh = NULL;
        struct buffer_head *lowest_bh = NULL;

        *target_bh = NULL;

        el = et->et_root_el;

        while(le16_to_cpu(el->l_tree_depth) > 1) {
                if (le16_to_cpu(el->l_next_free_rec) == 0) {
                        ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                                    "Owner %llu has empty extent list (next_free_rec == 0)\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci));
                        status = -EIO;
                        goto bail;
                }
                i = le16_to_cpu(el->l_next_free_rec) - 1;
                blkno = le64_to_cpu(el->l_recs[i].e_blkno);
                if (!blkno) {
                        ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                                    "Owner %llu has extent list where extent # %d has no physical block start\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci), i);
                        status = -EIO;
                        goto bail;
                }

                brelse(bh);
                bh = NULL;

                status = ocfs2_read_extent_block(et->et_ci, blkno, &bh);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }

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

                if (le16_to_cpu(el->l_next_free_rec) <
                    le16_to_cpu(el->l_count)) {
                        brelse(lowest_bh);
                        lowest_bh = bh;
                        get_bh(lowest_bh);
                }
        }

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

        *target_bh = lowest_bh;
bail:
        brelse(bh);

        return status;
}

/*
 * 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_bh will be updated by ocfs2_add_branch().
 */
static int ocfs2_grow_tree(handle_t *handle, struct ocfs2_extent_tree *et,
                           int *final_depth, struct buffer_head **last_eb_bh,
                           struct ocfs2_alloc_context *meta_ac)
{
        int ret, shift;
        struct ocfs2_extent_list *el = et->et_root_el;
        int depth = le16_to_cpu(el->l_tree_depth);
        struct buffer_head *bh = NULL;

        BUG_ON(meta_ac == NULL);

        shift = ocfs2_find_branch_target(et, &bh);
        if (shift < 0) {
                ret = shift;
                mlog_errno(ret);
                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) {
                BUG_ON(bh);
                trace_ocfs2_grow_tree(
                        (unsigned long long)
                        ocfs2_metadata_cache_owner(et->et_ci),
                        depth);

                /* ocfs2_shift_tree_depth will return us a buffer with
                 * the new extent block (so we can pass that to
                 * ocfs2_add_branch). */
                ret = ocfs2_shift_tree_depth(handle, et, meta_ac, &bh);
                if (ret < 0) {
                        mlog_errno(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_bh as the new leaf. At depth
                         * zero, it should always be null so there's
                         * no reason to brelse.
                         */
                        BUG_ON(*last_eb_bh);
                        get_bh(bh);
                        *last_eb_bh = bh;
                        goto out;
                }
        }

        /* call ocfs2_add_branch to add the final part of the tree with
         * the new data. */
        ret = ocfs2_add_branch(handle, et, bh, last_eb_bh,
                               meta_ac);
        if (ret < 0) {
                mlog_errno(ret);
                goto out;
        }

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

/*
 * This function will discard the rightmost extent record.
 */
static void ocfs2_shift_records_right(struct ocfs2_extent_list *el)
{
        int next_free = le16_to_cpu(el->l_next_free_rec);
        int count = le16_to_cpu(el->l_count);
        unsigned int num_bytes;

        BUG_ON(!next_free);
        /* This will cause us to go off the end of our extent list. */
        BUG_ON(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;
        u32 insert_cpos = le32_to_cpu(insert_rec->e_cpos);
        struct ocfs2_extent_rec *rec;

        next_free = le16_to_cpu(el->l_next_free_rec);
        has_empty = ocfs2_is_empty_extent(&el->l_recs[0]);

        BUG_ON(!next_free);

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

        /*
         * 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 < le32_to_cpu(rec->e_cpos))
                        break;
        }
        insert_index = i;

        trace_ocfs2_rotate_leaf(insert_cpos, insert_index,
                                has_empty, next_free,
                                le16_to_cpu(el->l_count));

        BUG_ON(insert_index < 0);
        BUG_ON(insert_index >= le16_to_cpu(el->l_count));
        BUG_ON(insert_index > next_free);

        /*
         * No need to memmove if we're just adding to the tail.
         */
        if (insert_index != next_free) {
                BUG_ON(next_free >= le16_to_cpu(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 = cpu_to_le16(next_free);
        /*
         * Make sure none of the math above just messed up our tree.
         */
        BUG_ON(le16_to_cpu(el->l_next_free_rec) > le16_to_cpu(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 = le16_to_cpu(el->l_next_free_rec);

        BUG_ON(num_recs == 0);

        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 = cpu_to_le16(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 = le16_to_cpu(el->l_next_free_rec);

        BUG_ON(le16_to_cpu(el->l_tree_depth) != 0);

        if (next_free == 0)
                goto set_and_inc;

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

        mlog_bug_on_msg(el->l_count == el->l_next_free_rec,
                        "Asked to create an empty extent in a full list:\n"
                        "count = %u, tree depth = %u",
                        le16_to_cpu(el->l_count),
                        le16_to_cpu(el->l_tree_depth));

        ocfs2_shift_records_right(el);

set_and_inc:
        le16_add_cpu(&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.
 */
int ocfs2_find_subtree_root(struct ocfs2_extent_tree *et,
                            struct ocfs2_path *left,
                            struct ocfs2_path *right)
{
        int i = 0;

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

        do {
                i++;

                /*
                 * The caller didn't pass two adjacent paths.
                 */
                mlog_bug_on_msg(i > left->p_tree_depth,
                                "Owner %llu, left depth %u, right depth %u\n"
                                "left leaf blk %llu, right leaf blk %llu\n",
                                (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                                left->p_tree_depth, right->p_tree_depth,
                                (unsigned long long)path_leaf_bh(left)->b_blocknr,
                                (unsigned long long)path_leaf_bh(right)->b_blocknr);
        } while (left->p_node[i].bh->b_blocknr ==
                 right->p_node[i].bh->b_blocknr);

        return i - 1;
}

typedef void (path_insert_t)(void *, struct buffer_head *);

/*
 * 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 int __ocfs2_find_path(struct ocfs2_caching_info *ci,
                             struct ocfs2_extent_list *root_el, u32 cpos,
                             path_insert_t *func, void *data)
{
        int i, ret = 0;
        u32 range;
        u64 blkno;
        struct buffer_head *bh = 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 (le16_to_cpu(el->l_next_free_rec) == 0) {
                        ocfs2_error(ocfs2_metadata_cache_get_super(ci),
                                    "Owner %llu has empty extent list at depth %u\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(ci),
                                    le16_to_cpu(el->l_tree_depth));
                        ret = -EROFS;
                        goto out;

                }

                for(i = 0; i < le16_to_cpu(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 = le32_to_cpu(rec->e_cpos) +
                                ocfs2_rec_clusters(el, rec);
                        if (cpos >= le32_to_cpu(rec->e_cpos) && cpos < range)
                            break;
                }

                blkno = le64_to_cpu(el->l_recs[i].e_blkno);
                if (blkno == 0) {
                        ocfs2_error(ocfs2_metadata_cache_get_super(ci),
                                    "Owner %llu has bad blkno in extent list at depth %u (index %d)\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(ci),
                                    le16_to_cpu(el->l_tree_depth), i);
                        ret = -EROFS;
                        goto out;
                }

                brelse(bh);
                bh = NULL;
                ret = ocfs2_read_extent_block(ci, blkno, &bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

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

                if (le16_to_cpu(el->l_next_free_rec) >
                    le16_to_cpu(el->l_count)) {
                        ocfs2_error(ocfs2_metadata_cache_get_super(ci),
                                    "Owner %llu has bad count in extent list at block %llu (next free=%u, count=%u)\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(ci),
                                    (unsigned long long)bh->b_blocknr,
                                    le16_to_cpu(el->l_next_free_rec),
                                    le16_to_cpu(el->l_count));
                        ret = -EROFS;
                        goto out;
                }

                if (func)
                        func(data, bh);
        }

out:
        /*
         * Catch any trailing bh that the loop didn't handle.
         */
        brelse(bh);

        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 void find_path_ins(void *data, struct buffer_head *bh)
{
        struct find_path_data *fp = data;

        get_bh(bh);
        ocfs2_path_insert_eb(fp->path, fp->index, bh);
        fp->index++;
}
int ocfs2_find_path(struct ocfs2_caching_info *ci,
                    struct ocfs2_path *path, u32 cpos)
{
        struct find_path_data data;

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

static void find_leaf_ins(void *data, struct buffer_head *bh)
{
        struct ocfs2_extent_block *eb =(struct ocfs2_extent_block *)bh->b_data;
        struct ocfs2_extent_list *el = &eb->h_list;
        struct buffer_head **ret = data;

        /* We want to retain only the leaf block. */
        if (le16_to_cpu(el->l_tree_depth) == 0) {
                get_bh(bh);
                *ret = bh;
        }
}
/*
 * Find the leaf block in the tree which would contain cpos. No
 * checking of the actual leaf is done.
 *
 * Some paths want to call this instead of allocating a path structure
 * and calling ocfs2_find_path().
 *
 * This function doesn't handle non btree extent lists.
 */
int ocfs2_find_leaf(struct ocfs2_caching_info *ci,
                    struct ocfs2_extent_list *root_el, u32 cpos,
                    struct buffer_head **leaf_bh)
{
        int ret;
        struct buffer_head *bh = NULL;

        ret = __ocfs2_find_path(ci, root_el, cpos, find_leaf_ins, &bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        *leaf_bh = bh;
out:
        return ret;
}

/*
 * 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)
{
        u32 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 = le32_to_cpu(right_child_el->l_recs[0].e_cpos);
        if (!ocfs2_rec_clusters(right_child_el, &right_child_el->l_recs[0])) {
                BUG_ON(right_child_el->l_tree_depth);
                BUG_ON(le16_to_cpu(right_child_el->l_next_free_rec) <= 1);
                left_clusters = le32_to_cpu(right_child_el->l_recs[1].e_cpos);
        }
        left_clusters -= le32_to_cpu(left_rec->e_cpos);
        left_rec->e_int_clusters = cpu_to_le32(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 = le32_to_cpu(right_rec->e_cpos);
        right_end += le32_to_cpu(right_rec->e_int_clusters);

        right_rec->e_cpos = left_rec->e_cpos;
        le32_add_cpu(&right_rec->e_cpos, left_clusters);

        right_end -= le32_to_cpu(right_rec->e_cpos);
        right_rec->e_int_clusters = cpu_to_le32(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,
                                      u64 left_el_blkno)
{
        int i;

        BUG_ON(le16_to_cpu(root_el->l_tree_depth) <=
               le16_to_cpu(left_el->l_tree_depth));

        for(i = 0; i < le16_to_cpu(root_el->l_next_free_rec) - 1; i++) {
                if (le64_to_cpu(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.
         */
        BUG_ON(i >= (le16_to_cpu(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.
 *   - When we've adjusted the last extent record in the left path leaf and the
 *     1st extent record in the right path leaf during cross extent block merge.
 */
static void ocfs2_complete_edge_insert(handle_t *handle,
                                       struct ocfs2_path *left_path,
                                       struct ocfs2_path *right_path,
                                       int subtree_index)
{
        int i, idx;
        struct ocfs2_extent_list *el, *left_el, *right_el;
        struct ocfs2_extent_rec *left_rec, *right_rec;
        struct buffer_head *root_bh = left_path->p_node[subtree_index].bh;

        /*
         * 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--) {
                trace_ocfs2_complete_edge_insert(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 = le16_to_cpu(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);

                ocfs2_journal_dirty(handle, left_path->p_node[i].bh);
                ocfs2_journal_dirty(handle, right_path->p_node[i].bh);

                /*
                 * 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;

        ocfs2_adjust_root_records(el, left_el, right_el,
                                  left_path->p_node[subtree_index + 1].bh->b_blocknr);

        root_bh = left_path->p_node[subtree_index].bh;

        ocfs2_journal_dirty(handle, root_bh);
}

static int ocfs2_rotate_subtree_right(handle_t *handle,
                                      struct ocfs2_extent_tree *et,
                                      struct ocfs2_path *left_path,
                                      struct ocfs2_path *right_path,
                                      int subtree_index)
{
        int ret, i;
        struct buffer_head *right_leaf_bh;
        struct buffer_head *left_leaf_bh = NULL;
        struct buffer_head *root_bh;
        struct ocfs2_extent_list *right_el, *left_el;
        struct ocfs2_extent_rec move_rec;

        left_leaf_bh = path_leaf_bh(left_path);
        left_el = path_leaf_el(left_path);

        if (left_el->l_next_free_rec != left_el->l_count) {
                ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                            "Inode %llu has non-full interior leaf node %llu (next free = %u)\n",
                            (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                            (unsigned long long)left_leaf_bh->b_blocknr,
                            le16_to_cpu(left_el->l_next_free_rec));
                return -EROFS;
        }

        /*
         * 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;

        root_bh = left_path->p_node[subtree_index].bh;
        BUG_ON(root_bh != right_path->p_node[subtree_index].bh);

        ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                                           subtree_index);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        for(i = subtree_index + 1; i < path_num_items(right_path); i++) {
                ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                                                   right_path, i);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                                                   left_path, i);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        }

        right_leaf_bh = path_leaf_bh(right_path);
        right_el = path_leaf_el(right_path);

        /* This is a code error, not a disk corruption. */
        mlog_bug_on_msg(!right_el->l_next_free_rec, "Inode %llu: Rotate fails "
                        "because rightmost leaf block %llu is empty\n",
                        (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                        (unsigned long long)right_leaf_bh->b_blocknr);

        ocfs2_create_empty_extent(right_el);

        ocfs2_journal_dirty(handle, right_leaf_bh);

        /* Do the copy now. */
        i = le16_to_cpu(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).
         */
        le16_add_cpu(&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));
        le16_add_cpu(&left_el->l_next_free_rec, 1);

        ocfs2_journal_dirty(handle, left_leaf_bh);

        ocfs2_complete_edge_insert(handle, left_path, right_path,
                                   subtree_index);

out:
        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.
 */
int ocfs2_find_cpos_for_left_leaf(struct super_block *sb,
                                  struct ocfs2_path *path, u32 *cpos)
{
        int i, j, ret = 0;
        u64 blkno;
        struct ocfs2_extent_list *el;

        BUG_ON(path->p_tree_depth == 0);

        *cpos = 0;

        blkno = path_leaf_bh(path)->b_blocknr;

        /* 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 < le16_to_cpu(el->l_next_free_rec); j++) {
                        if (le64_to_cpu(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 = le32_to_cpu(el->l_recs[j - 1].e_cpos);
                                *cpos = *cpos + ocfs2_rec_clusters(el,
                                                           &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.
                 */
                ocfs2_error(sb, "Invalid extent tree at extent block %llu\n",
                            (unsigned long long)blkno);
                ret = -EROFS;
                goto out;

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

out:
        return ret;
}

/*
 * Extend the transaction by enough credits to complete the rotation,
 * and still leave at least the original number of credits allocated
 * to this transaction.
 */
static int ocfs2_extend_rotate_transaction(handle_t *handle, int subtree_depth,
                                           int op_credits,
                                           struct ocfs2_path *path)
{
        int ret = 0;
        int credits = (path->p_tree_depth - subtree_depth) * 2 + 1 + op_credits;

        if (handle->h_buffer_credits < credits)
                ret = ocfs2_extend_trans(handle,
                                         credits - handle->h_buffer_credits);

        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,
                                                 u32 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 = le16_to_cpu(left_el->l_next_free_rec);
        rec = &left_el->l_recs[next_free - 1];

        if (insert_cpos > le32_to_cpu(rec->e_cpos))
                return 1;
        return 0;
}

static int ocfs2_leftmost_rec_contains(struct ocfs2_extent_list *el, u32 cpos)
{
        int next_free = le16_to_cpu(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 = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
        if (cpos >= le32_to_cpu(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 successful 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(handle_t *handle,
                                   struct ocfs2_extent_tree *et,
                                   enum ocfs2_split_type split,
                                   u32 insert_cpos,
                                   struct ocfs2_path *right_path,
                                   struct ocfs2_path **ret_left_path)
{
        int ret, start, orig_credits = handle->h_buffer_credits;
        u32 cpos;
        struct ocfs2_path *left_path = NULL;
        struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);

        *ret_left_path = NULL;

        left_path = ocfs2_new_path_from_path(right_path);
        if (!left_path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

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

        trace_ocfs2_rotate_tree_right(
                (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                insert_cpos, cpos);

        /*
         * 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) {
                trace_ocfs2_rotate_tree_right(
                        (unsigned long long)
                        ocfs2_metadata_cache_owner(et->et_ci),
                        insert_cpos, cpos);

                ret = ocfs2_find_path(et->et_ci, left_path, cpos);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                mlog_bug_on_msg(path_leaf_bh(left_path) ==
                                path_leaf_bh(right_path),
                                "Owner %llu: error during insert of %u "
                                "(left path cpos %u) results in two identical "
                                "paths ending at %llu\n",
                                (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                                insert_cpos, cpos,
                                (unsigned long long)
                                path_leaf_bh(left_path)->b_blocknr);

                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(et, left_path, right_path);

                trace_ocfs2_rotate_subtree(start,
                        (unsigned long long)
                        right_path->p_node[start].bh->b_blocknr,
                        right_path->p_tree_depth);

                ret = ocfs2_extend_rotate_transaction(handle, start,
                                                      orig_credits, right_path);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_rotate_subtree_right(handle, et, left_path,
                                                 right_path, start);
                if (ret) {
                        mlog_errno(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(sb, right_path, &cpos);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        }

out:
        ocfs2_free_path(left_path);

out_ret_path:
        return ret;
}

static int ocfs2_update_edge_lengths(handle_t *handle,
                                     struct ocfs2_extent_tree *et,
                                     int subtree_index, struct ocfs2_path *path)
{
        int i, idx, ret;
        struct ocfs2_extent_rec *rec;
        struct ocfs2_extent_list *el;
        struct ocfs2_extent_block *eb;
        u32 range;

        /*
         * In normal tree rotation process, we will never touch the
         * tree branch above subtree_index and ocfs2_extend_rotate_transaction
         * doesn't reserve the credits for them either.
         *
         * But we do have a special case here which will update the rightmost
         * records for all the bh in the path.
         * So we have to allocate extra credits and access them.
         */
        ret = ocfs2_extend_trans(handle, subtree_index);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_journal_access_path(et->et_ci, handle, path);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /* Path should always be rightmost. */
        eb = (struct ocfs2_extent_block *)path_leaf_bh(path)->b_data;
        BUG_ON(eb->h_next_leaf_blk != 0ULL);

        el = &eb->h_list;
        BUG_ON(le16_to_cpu(el->l_next_free_rec) == 0);
        idx = le16_to_cpu(el->l_next_free_rec) - 1;
        rec = &el->l_recs[idx];
        range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);

        for (i = 0; i < path->p_tree_depth; i++) {
                el = path->p_node[i].el;
                idx = le16_to_cpu(el->l_next_free_rec) - 1;
                rec = &el->l_recs[idx];

                rec->e_int_clusters = cpu_to_le32(range);
                le32_add_cpu(&rec->e_int_clusters, -le32_to_cpu(rec->e_cpos));

                ocfs2_journal_dirty(handle, path->p_node[i].bh);
        }
out:
        return ret;
}

static void ocfs2_unlink_path(handle_t *handle,
                              struct ocfs2_extent_tree *et,
                              struct ocfs2_cached_dealloc_ctxt *dealloc,
                              struct ocfs2_path *path, int unlink_start)
{
        int ret, i;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list *el;
        struct buffer_head *bh;

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

                eb = (struct ocfs2_extent_block *)bh->b_data;
                /*
                 * Not all nodes might have had their final count
                 * decremented by the caller - handle this here.
                 */
                el = &eb->h_list;
                if (le16_to_cpu(el->l_next_free_rec) > 1) {
                        mlog(ML_ERROR,
                             "Inode %llu, attempted to remove extent block "
                             "%llu with %u records\n",
                             (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                             (unsigned long long)le64_to_cpu(eb->h_blkno),
                             le16_to_cpu(el->l_next_free_rec));

                        ocfs2_journal_dirty(handle, bh);
                        ocfs2_remove_from_cache(et->et_ci, bh);
                        continue;
                }

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

                ocfs2_journal_dirty(handle, bh);

                ret = ocfs2_cache_extent_block_free(dealloc, eb);
                if (ret)
                        mlog_errno(ret);

                ocfs2_remove_from_cache(et->et_ci, bh);
        }
}

static void ocfs2_unlink_subtree(handle_t *handle,
                                 struct ocfs2_extent_tree *et,
                                 struct ocfs2_path *left_path,
                                 struct ocfs2_path *right_path,
                                 int subtree_index,
                                 struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        int i;
        struct buffer_head *root_bh = left_path->p_node[subtree_index].bh;
        struct ocfs2_extent_list *root_el = left_path->p_node[subtree_index].el;
        struct ocfs2_extent_list *el;
        struct ocfs2_extent_block *eb;

        el = path_leaf_el(left_path);

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

        for(i = 1; i < le16_to_cpu(root_el->l_next_free_rec); i++)
                if (root_el->l_recs[i].e_blkno == eb->h_blkno)
                        break;

        BUG_ON(i >= le16_to_cpu(root_el->l_next_free_rec));

        memset(&root_el->l_recs[i], 0, sizeof(struct ocfs2_extent_rec));
        le16_add_cpu(&root_el->l_next_free_rec, -1);

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

        ocfs2_journal_dirty(handle, root_bh);
        ocfs2_journal_dirty(handle, path_leaf_bh(left_path));

        ocfs2_unlink_path(handle, et, dealloc, right_path,
                          subtree_index + 1);
}

static int ocfs2_rotate_subtree_left(handle_t *handle,
                                     struct ocfs2_extent_tree *et,
                                     struct ocfs2_path *left_path,
                                     struct ocfs2_path *right_path,
                                     int subtree_index,
                                     struct ocfs2_cached_dealloc_ctxt *dealloc,
                                     int *deleted)
{
        int ret, i, del_right_subtree = 0, right_has_empty = 0;
        struct buffer_head *root_bh, *et_root_bh = path_root_bh(right_path);
        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);
        root_bh = left_path->p_node[subtree_index].bh;
        BUG_ON(root_bh != right_path->p_node[subtree_index].bh);

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

        eb = (struct ocfs2_extent_block *)path_leaf_bh(right_path)->b_data;
        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 (le16_to_cpu(right_leaf_el->l_next_free_rec) > 1) {
                        ret = ocfs2_journal_access_eb(handle, et->et_ci,
                                                      path_leaf_bh(right_path),
                                                      OCFS2_JOURNAL_ACCESS_WRITE);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }

                        ocfs2_remove_empty_extent(right_leaf_el);
                } else
                        right_has_empty = 1;
        }

        if (eb->h_next_leaf_blk == 0ULL &&
            le16_to_cpu(right_leaf_el->l_next_free_rec) == 1) {
                /*
                 * We have to update i_last_eb_blk during the meta
                 * data delete.
                 */
                ret = ocfs2_et_root_journal_access(handle, et,
                                                   OCFS2_JOURNAL_ACCESS_WRITE);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                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.
         */
        BUG_ON(right_has_empty && !del_right_subtree);

        ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                                           subtree_index);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        for(i = subtree_index + 1; i < path_num_items(right_path); i++) {
                ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                                                   right_path, i);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                                                   left_path, i);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        }

        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);
        }

        ocfs2_journal_dirty(handle, path_leaf_bh(left_path));
        ocfs2_journal_dirty(handle, path_leaf_bh(right_path));

        if (del_right_subtree) {
                ocfs2_unlink_subtree(handle, et, left_path, right_path,
                                     subtree_index, dealloc);
                ret = ocfs2_update_edge_lengths(handle, et, subtree_index,
                                                left_path);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                eb = (struct ocfs2_extent_block *)path_leaf_bh(left_path)->b_data;
                ocfs2_et_set_last_eb_blk(et, le64_to_cpu(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);

                ocfs2_journal_dirty(handle, et_root_bh);

                *deleted = 1;
        } else
                ocfs2_complete_edge_insert(handle, left_path, right_path,
                                           subtree_index);

out:
        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().
 */
int ocfs2_find_cpos_for_right_leaf(struct super_block *sb,
                                   struct ocfs2_path *path, u32 *cpos)
{
        int i, j, ret = 0;
        u64 blkno;
        struct ocfs2_extent_list *el;

        *cpos = 0;

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

        blkno = path_leaf_bh(path)->b_blocknr;

        /* 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 = le16_to_cpu(el->l_next_free_rec);
                for(j = 0; j < le16_to_cpu(el->l_next_free_rec); j++) {
                        if (le64_to_cpu(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 = le32_to_cpu(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.
                 */
                ocfs2_error(sb, "Invalid extent tree at extent block %llu\n",
                            (unsigned long long)blkno);
                ret = -EROFS;
                goto out;

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

out:
        return ret;
}

static int ocfs2_rotate_rightmost_leaf_left(handle_t *handle,
                                            struct ocfs2_extent_tree *et,
                                            struct ocfs2_path *path)
{
        int ret;
        struct buffer_head *bh = path_leaf_bh(path);
        struct ocfs2_extent_list *el = path_leaf_el(path);

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

        ret = ocfs2_path_bh_journal_access(handle, et->et_ci, path,
                                           path_num_items(path) - 1);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ocfs2_remove_empty_extent(el);
        ocfs2_journal_dirty(handle, bh);

out:
        return ret;
}

static int __ocfs2_rotate_tree_left(handle_t *handle,
                                    struct ocfs2_extent_tree *et,
                                    int orig_credits,
                                    struct ocfs2_path *path,
                                    struct ocfs2_cached_dealloc_ctxt *dealloc,
                                    struct ocfs2_path **empty_extent_path)
{
        int ret, subtree_root, deleted;
        u32 right_cpos;
        struct ocfs2_path *left_path = NULL;
        struct ocfs2_path *right_path = NULL;
        struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);

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

        *empty_extent_path = NULL;

        ret = ocfs2_find_cpos_for_right_leaf(sb, path, &right_cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        left_path = ocfs2_new_path_from_path(path);
        if (!left_path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        ocfs2_cp_path(left_path, path);

        right_path = ocfs2_new_path_from_path(path);
        if (!right_path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        while (right_cpos) {
                ret = ocfs2_find_path(et->et_ci, right_path, right_cpos);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                subtree_root = ocfs2_find_subtree_root(et, left_path,
                                                       right_path);

                trace_ocfs2_rotate_subtree(subtree_root,
                     (unsigned long long)
                     right_path->p_node[subtree_root].bh->b_blocknr,
                     right_path->p_tree_depth);

                ret = ocfs2_extend_rotate_transaction(handle, subtree_root,
                                                      orig_credits, left_path);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                /*
                 * Caller might still want to make changes to the
                 * tree root, so re-add it to the journal here.
                 */
                ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                                                   left_path, 0);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_rotate_subtree_left(handle, et, left_path,
                                                right_path, subtree_root,
                                                dealloc, &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) {
                        mlog_errno(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(sb, left_path,
                                                     &right_cpos);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        }

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

        return ret;
}

static int ocfs2_remove_rightmost_path(handle_t *handle,
                                struct ocfs2_extent_tree *et,
                                struct ocfs2_path *path,
                                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        int ret, subtree_index;
        u32 cpos;
        struct ocfs2_path *left_path = NULL;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list *el;


        ret = ocfs2_et_sanity_check(et);
        if (ret)
                goto out;
        /*
         * There's two ways we handle this depending on
         * whether path is the only existing one.
         */
        ret = ocfs2_extend_rotate_transaction(handle, 0,
                                              handle->h_buffer_credits,
                                              path);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_journal_access_path(et->et_ci, handle, path);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_find_cpos_for_left_leaf(ocfs2_metadata_cache_get_super(et->et_ci),
                                            path, &cpos);
        if (ret) {
                mlog_errno(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 = -ENOMEM;
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_find_path(et->et_ci, left_path, cpos);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_journal_access_path(et->et_ci, handle, left_path);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                subtree_index = ocfs2_find_subtree_root(et, left_path, path);

                ocfs2_unlink_subtree(handle, et, left_path, path,
                                     subtree_index, dealloc);
                ret = ocfs2_update_edge_lengths(handle, et, subtree_index,
                                                left_path);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                eb = (struct ocfs2_extent_block *)path_leaf_bh(left_path)->b_data;
                ocfs2_et_set_last_eb_blk(et, le64_to_cpu(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 root back to having extents
                 * in-line.
                 */
                ocfs2_unlink_path(handle, et, dealloc, 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);
        }

        ocfs2_journal_dirty(handle, path_root_bh(path));

out:
        ocfs2_free_path(left_path);
        return ret;
}

static int ocfs2_remove_rightmost_empty_extent(struct ocfs2_super *osb,
                                struct ocfs2_extent_tree *et,
                                struct ocfs2_path *path,
                                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        handle_t *handle;
        int ret;
        int credits = path->p_tree_depth * 2 + 1;

        handle = ocfs2_start_trans(osb, credits);
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
                mlog_errno(ret);
                return ret;
        }

        ret = ocfs2_remove_rightmost_path(handle, et, path, dealloc);
        if (ret)
                mlog_errno(ret);

        ocfs2_commit_trans(osb, handle);
        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(handle_t *handle,
                                  struct ocfs2_extent_tree *et,
                                  struct ocfs2_path *path,
                                  struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        int ret, orig_credits = handle->h_buffer_credits;
        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:
                /*
                 * Inline extents. This is trivially handled, so do
                 * it up front.
                 */
                ret = ocfs2_rotate_rightmost_leaf_left(handle, et, path);
                if (ret)
                        mlog_errno(ret);
                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 root back to inline extents.
         */

        eb = (struct ocfs2_extent_block *)path_leaf_bh(path)->b_data;
        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 (le16_to_cpu(el->l_next_free_rec) > 1)
                        goto rightmost_no_delete;

                if (le16_to_cpu(el->l_next_free_rec) == 0) {
                        ret = -EIO;
                        ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                                    "Owner %llu has empty extent block at %llu\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci),
                                    (unsigned long long)le64_to_cpu(eb->h_blkno));
                        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(handle, et, path,
                                                  dealloc);
                if (ret)
                        mlog_errno(ret);
                goto out;
        }

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

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

                ret = __ocfs2_rotate_tree_left(handle, et, orig_credits,
                                               tmp_path, dealloc,
                                               &restart_path);
                if (ret && ret != -EAGAIN) {
                        mlog_errno(ret);
                        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) {
                        BUG_ON(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));
        }
}

static int ocfs2_get_right_path(struct ocfs2_extent_tree *et,
                                struct ocfs2_path *left_path,
                                struct ocfs2_path **ret_right_path)
{
        int ret;
        u32 right_cpos;
        struct ocfs2_path *right_path = NULL;
        struct ocfs2_extent_list *left_el;

        *ret_right_path = NULL;

        /* This function shouldn't be called for non-trees. */
        BUG_ON(left_path->p_tree_depth == 0);

        left_el = path_leaf_el(left_path);
        BUG_ON(left_el->l_next_free_rec != left_el->l_count);

        ret = ocfs2_find_cpos_for_right_leaf(ocfs2_metadata_cache_get_super(et->et_ci),
                                             left_path, &right_cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /* This function shouldn't be called for the rightmost leaf. */
        BUG_ON(right_cpos == 0);

        right_path = ocfs2_new_path_from_path(left_path);
        if (!right_path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_find_path(et->et_ci, right_path, right_cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        *ret_right_path = right_path;
out:
        if (ret)
                ocfs2_free_path(right_path);
        return ret;
}

/*
 * Remove split_rec clusters from the record at index and merge them
 * onto the beginning of the record "next" to it.
 * For index < l_count - 1, the next means the extent rec at index + 1.
 * For index == l_count - 1, the "next" means the 1st extent rec of the
 * next extent block.
 */
static int ocfs2_merge_rec_right(struct ocfs2_path *left_path,
                                 handle_t *handle,
                                 struct ocfs2_extent_tree *et,
                                 struct ocfs2_extent_rec *split_rec,
                                 int index)
{
        int ret, next_free, i;
        unsigned int split_clusters = le16_to_cpu(split_rec->e_leaf_clusters);
        struct ocfs2_extent_rec *left_rec;
        struct ocfs2_extent_rec *right_rec;
        struct ocfs2_extent_list *right_el;
        struct ocfs2_path *right_path = NULL;
        int subtree_index = 0;
        struct ocfs2_extent_list *el = path_leaf_el(left_path);
        struct buffer_head *bh = path_leaf_bh(left_path);
        struct buffer_head *root_bh = NULL;

        BUG_ON(index >= le16_to_cpu(el->l_next_free_rec));
        left_rec = &el->l_recs[index];

        if (index == le16_to_cpu(el->l_next_free_rec) - 1 &&
            le16_to_cpu(el->l_next_free_rec) == le16_to_cpu(el->l_count)) {
                /* we meet with a cross extent block merge. */
                ret = ocfs2_get_right_path(et, left_path, &right_path);
                if (ret) {
                        mlog_errno(ret);
                        return ret;
                }

                right_el = path_leaf_el(right_path);
                next_free = le16_to_cpu(right_el->l_next_free_rec);
                BUG_ON(next_free <= 0);
                right_rec = &right_el->l_recs[0];
                if (ocfs2_is_empty_extent(right_rec)) {
                        BUG_ON(next_free <= 1);
                        right_rec = &right_el->l_recs[1];
                }

                BUG_ON(le32_to_cpu(left_rec->e_cpos) +
                       le16_to_cpu(left_rec->e_leaf_clusters) !=
                       le32_to_cpu(right_rec->e_cpos));

                subtree_index = ocfs2_find_subtree_root(et, left_path,
                                                        right_path);

                ret = ocfs2_extend_rotate_transaction(handle, subtree_index,
                                                      handle->h_buffer_credits,
                                                      right_path);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                root_bh = left_path->p_node[subtree_index].bh;
                BUG_ON(root_bh != right_path->p_node[subtree_index].bh);

                ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                                                   subtree_index);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                for (i = subtree_index + 1;
                     i < path_num_items(right_path); i++) {
                        ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                                                           right_path, i);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }

                        ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                                                           left_path, i);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }
                }

        } else {
                BUG_ON(index == le16_to_cpu(el->l_next_free_rec) - 1);
                right_rec = &el->l_recs[index + 1];
        }

        ret = ocfs2_path_bh_journal_access(handle, et->et_ci, left_path,
                                           path_num_items(left_path) - 1);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        le16_add_cpu(&left_rec->e_leaf_clusters, -split_clusters);

        le32_add_cpu(&right_rec->e_cpos, -split_clusters);
        le64_add_cpu(&right_rec->e_blkno,
                     -ocfs2_clusters_to_blocks(ocfs2_metadata_cache_get_super(et->et_ci),
                                               split_clusters));
        le16_add_cpu(&right_rec->e_leaf_clusters, split_clusters);

        ocfs2_cleanup_merge(el, index);

        ocfs2_journal_dirty(handle, bh);
        if (right_path) {
                ocfs2_journal_dirty(handle, path_leaf_bh(right_path));
                ocfs2_complete_edge_insert(handle, left_path, right_path,
                                           subtree_index);
        }
out:
        ocfs2_free_path(right_path);
        return ret;
}

static int ocfs2_get_left_path(struct ocfs2_extent_tree *et,
                               struct ocfs2_path *right_path,
                               struct ocfs2_path **ret_left_path)
{
        int ret;
        u32 left_cpos;
        struct ocfs2_path *left_path = NULL;

        *ret_left_path = NULL;

        /* This function shouldn't be called for non-trees. */
        BUG_ON(right_path->p_tree_depth == 0);

        ret = ocfs2_find_cpos_for_left_leaf(ocfs2_metadata_cache_get_super(et->et_ci),
                                            right_path, &left_cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /* This function shouldn't be called for the leftmost leaf. */
        BUG_ON(left_cpos == 0);

        left_path = ocfs2_new_path_from_path(right_path);
        if (!left_path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_find_path(et->et_ci, left_path, left_cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

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

/*
 * Remove split_rec clusters from the record at index and merge them
 * onto the tail of the record "before" it.
 * For index > 0, the "before" means the extent rec at index - 1.
 *
 * For index == 0, the "before" means the last record of the previous
 * extent block. And there is also a situation that we may need to
 * remove the rightmost leaf extent block in the right_path and change
 * the right path to indicate the new rightmost path.
 */
static int ocfs2_merge_rec_left(struct ocfs2_path *right_path,
                                handle_t *handle,
                                struct ocfs2_extent_tree *et,
                                struct ocfs2_extent_rec *split_rec,
                                struct ocfs2_cached_dealloc_ctxt *dealloc,
                                int index)
{
        int ret, i, subtree_index = 0, has_empty_extent = 0;
        unsigned int split_clusters = le16_to_cpu(split_rec->e_leaf_clusters);
        struct ocfs2_extent_rec *left_rec;
        struct ocfs2_extent_rec *right_rec;
        struct ocfs2_extent_list *el = path_leaf_el(right_path);
        struct buffer_head *bh = path_leaf_bh(right_path);
        struct buffer_head *root_bh = NULL;
        struct ocfs2_path *left_path = NULL;
        struct ocfs2_extent_list *left_el;

        BUG_ON(index < 0);

        right_rec = &el->l_recs[index];
        if (index == 0) {
                /* we meet with a cross extent block merge. */
                ret = ocfs2_get_left_path(et, right_path, &left_path);
                if (ret) {
                        mlog_errno(ret);
                        return ret;
                }

                left_el = path_leaf_el(left_path);
                BUG_ON(le16_to_cpu(left_el->l_next_free_rec) !=
                       le16_to_cpu(left_el->l_count));

                left_rec = &left_el->l_recs[
                                le16_to_cpu(left_el->l_next_free_rec) - 1];
                BUG_ON(le32_to_cpu(left_rec->e_cpos) +
                       le16_to_cpu(left_rec->e_leaf_clusters) !=
                       le32_to_cpu(split_rec->e_cpos));

                subtree_index = ocfs2_find_subtree_root(et, left_path,
                                                        right_path);

                ret = ocfs2_extend_rotate_transaction(handle, subtree_index,
                                                      handle->h_buffer_credits,
                                                      left_path);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                root_bh = left_path->p_node[subtree_index].bh;
                BUG_ON(root_bh != right_path->p_node[subtree_index].bh);

                ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                                                   subtree_index);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                for (i = subtree_index + 1;
                     i < path_num_items(right_path); i++) {
                        ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                                                           right_path, i);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }

                        ret = ocfs2_path_bh_journal_access(handle, et->et_ci,
                                                           left_path, i);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }
                }
        } else {
                left_rec = &el->l_recs[index - 1];
                if (ocfs2_is_empty_extent(&el->l_recs[0]))
                        has_empty_extent = 1;
        }

        ret = ocfs2_path_bh_journal_access(handle, et->et_ci, right_path,
                                           path_num_items(right_path) - 1);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        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
                le16_add_cpu(&left_rec->e_leaf_clusters, split_clusters);

        le32_add_cpu(&right_rec->e_cpos, split_clusters);
        le64_add_cpu(&right_rec->e_blkno,
                     ocfs2_clusters_to_blocks(ocfs2_metadata_cache_get_super(et->et_ci),
                                              split_clusters));
        le16_add_cpu(&right_rec->e_leaf_clusters, -split_clusters);

        ocfs2_cleanup_merge(el, index);

        ocfs2_journal_dirty(handle, bh);
        if (left_path) {
                ocfs2_journal_dirty(handle, path_leaf_bh(left_path));

                /*
                 * In the situation that the right_rec is empty and the extent
                 * block is empty also,  ocfs2_complete_edge_insert can't handle
                 * it and we need to delete the right extent block.
                 */
                if (le16_to_cpu(right_rec->e_leaf_clusters) == 0 &&
                    le16_to_cpu(el->l_next_free_rec) == 1) {

                        ret = ocfs2_remove_rightmost_path(handle, et,
                                                          right_path,
                                                          dealloc);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }

                        /* Now the rightmost extent block has been deleted.
                         * So we use the new rightmost path.
                         */
                        ocfs2_mv_path(right_path, left_path);
                        left_path = NULL;
                } else
                        ocfs2_complete_edge_insert(handle, left_path,
                                                   right_path, subtree_index);
        }
out:
        ocfs2_free_path(left_path);
        return ret;
}

static int ocfs2_try_to_merge_extent(handle_t *handle,
                                     struct ocfs2_extent_tree *et,
                                     struct ocfs2_path *path,
                                     int split_index,
                                     struct ocfs2_extent_rec *split_rec,
                                     struct ocfs2_cached_dealloc_ctxt *dealloc,
                                     struct ocfs2_merge_ctxt *ctxt)
{
        int ret = 0;
        struct ocfs2_extent_list *el = path_leaf_el(path);
        struct ocfs2_extent_rec *rec = &el->l_recs[split_index];

        BUG_ON(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(handle, et, path, dealloc);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
                split_index--;
                rec = &el->l_recs[split_index];
        }

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

                /*
                 * 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.
                 *
                 * When the split_index is zero, we need to merge it to the
                 * prevoius extent block. It is more efficient and easier
                 * if we do merge_right first and merge_left later.
                 */
                ret = ocfs2_merge_rec_right(path, handle, et, split_rec,
                                            split_index);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

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

                /* The merge left us with an empty extent, remove it. */
                ret = ocfs2_rotate_tree_left(handle, et, path, dealloc);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                rec = &el->l_recs[split_index];

                /*
                 * Note that we don't pass split_rec here on purpose -
                 * we've merged it into the rec already.
                 */
                ret = ocfs2_merge_rec_left(path, handle, et, rec,
                                           dealloc, split_index);

                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_rotate_tree_left(handle, et, path, dealloc);
                /*
                 * Error from this last rotate is not critical, so
                 * print but don't bubble it up.
                 */
                if (ret)
                        mlog_errno(ret);
                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(path, handle, et,
                                                   split_rec, dealloc,
                                                   split_index);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }
                } else {
                        ret = ocfs2_merge_rec_right(path, handle,
                                                    et, split_rec,
                                                    split_index);
                        if (ret) {
                                mlog_errno(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(handle, et, path,
                                                     dealloc);
                        if (ret)
                                mlog_errno(ret);
                        ret = 0;
                }
        }

out:
        return ret;
}

static void ocfs2_subtract_from_rec(struct super_block *sb,
                                    enum ocfs2_split_type split,
                                    struct ocfs2_extent_rec *rec,
                                    struct ocfs2_extent_rec *split_rec)
{
        u64 len_blocks;

        len_blocks = ocfs2_clusters_to_blocks(sb,
                                le16_to_cpu(split_rec->e_leaf_clusters));

        if (split == SPLIT_LEFT) {
                /*
                 * Region is on the left edge of the existing
                 * record.
                 */
                le32_add_cpu(&rec->e_cpos,
                             le16_to_cpu(split_rec->e_leaf_clusters));
                le64_add_cpu(&rec->e_blkno, len_blocks);
                le16_add_cpu(&rec->e_leaf_clusters,
                             -le16_to_cpu(split_rec->e_leaf_clusters));
        } else {
                /*
                 * Region is on the right edge of the existing
                 * record.
                 */
                le16_add_cpu(&rec->e_leaf_clusters,
                             -le16_to_cpu(split_rec->e_leaf_clusters));
        }
}

/*
 * 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(struct ocfs2_extent_tree *et,
                                 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;

        BUG_ON(le16_to_cpu(el->l_tree_depth) != 0);

        if (insert->ins_split != SPLIT_NONE) {
                i = ocfs2_search_extent_list(el, le32_to_cpu(insert_rec->e_cpos));
                BUG_ON(i == -1);
                rec = &el->l_recs[i];
                ocfs2_subtract_from_rec(ocfs2_metadata_cache_get_super(et->et_ci),
                                        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;
                }
                le16_add_cpu(&rec->e_leaf_clusters,
                             le16_to_cpu(insert_rec->e_leaf_clusters));
                return;
        }

        /*
         * Handle insert into an empty leaf.
         */
        if (le16_to_cpu(el->l_next_free_rec) == 0 ||
            ((le16_to_cpu(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 = cpu_to_le16(1);
                return;
        }

        /*
         * Appending insert.
         */
        if (insert->ins_appending == APPEND_TAIL) {
                i = le16_to_cpu(el->l_next_free_rec) - 1;
                rec = &el->l_recs[i];
                range = le32_to_cpu(rec->e_cpos)
                        + le16_to_cpu(rec->e_leaf_clusters);
                BUG_ON(le32_to_cpu(insert_rec->e_cpos) < range);

                mlog_bug_on_msg(le16_to_cpu(el->l_next_free_rec) >=
                                le16_to_cpu(el->l_count),
                                "owner %llu, depth %u, count %u, next free %u, "
                                "rec.cpos %u, rec.clusters %u, "
                                "insert.cpos %u, insert.clusters %u\n",
                                ocfs2_metadata_cache_owner(et->et_ci),
                                le16_to_cpu(el->l_tree_depth),
                                le16_to_cpu(el->l_count),
                                le16_to_cpu(el->l_next_free_rec),
                                le32_to_cpu(el->l_recs[i].e_cpos),
                                le16_to_cpu(el->l_recs[i].e_leaf_clusters),
                                le32_to_cpu(insert_rec->e_cpos),
                                le16_to_cpu(insert_rec->e_leaf_clusters));
                i++;
                el->l_recs[i] = *insert_rec;
                le16_add_cpu(&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 void ocfs2_adjust_rightmost_records(handle_t *handle,
                                           struct ocfs2_extent_tree *et,
                                           struct ocfs2_path *path,
                                           struct ocfs2_extent_rec *insert_rec)
{
        int ret, i, next_free;
        struct buffer_head *bh;
        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++) {
                bh = path->p_node[i].bh;
                el = path->p_node[i].el;

                next_free = le16_to_cpu(el->l_next_free_rec);
                if (next_free == 0) {
                        ocfs2_error(ocfs2_metadata_cache_get_super(et->et_ci),
                                    "Owner %llu has a bad extent list\n",
                                    (unsigned long long)ocfs2_metadata_cache_owner(et->et_ci));
                        ret = -EIO;
                        return;
                }

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

                rec->e_int_clusters = insert_rec->e_cpos;
                le32_add_cpu(&rec->e_int_clusters,
                             le16_to_cpu(insert_rec->e_leaf_clusters));
                le32_add_cpu(&rec->e_int_clusters,
                             -le32_to_cpu(rec->e_cpos));

                ocfs2_journal_dirty(handle, bh);
        }
}

static int ocfs2_append_rec_to_path(handle_t *handle,
                                    struct ocfs2_extent_tree *et,
                                    struct ocfs2_extent_rec *insert_rec,
                                    struct ocfs2_path *right_path,
                                    struct ocfs2_path **ret_left_path)
{
        int ret, next_free;
        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.
         */
        BUG_ON(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 = le16_to_cpu(el->l_next_free_rec);
        if (next_free == 0 ||
            (next_free == 1 && ocfs2_is_empty_extent(&el->l_recs[0]))) {
                u32 left_cpos;

                ret = ocfs2_find_cpos_for_left_leaf(ocfs2_metadata_cache_get_super(et->et_ci),
                                                    right_path, &left_cpos);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                trace_ocfs2_append_rec_to_path(