Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6

[linux-2.6] / fs / ocfs2 / alloc.c

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * alloc.c
 *
 * Extent allocs and frees
 *
 * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

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

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

#include "ocfs2.h"

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

#include "buffer_head_io.h"

static void ocfs2_free_truncate_context(struct ocfs2_truncate_context *tc);

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

#define OCFS2_MAX_PATH_DEPTH    5

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

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

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

        if (keep_root)
                start = 1;

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

                brelse(node->bh);
                node->bh = NULL;
                node->el = NULL;
        }

        /*
         * Tree depth may change during truncate, or insert. If we're
         * keeping the root extent list, then make sure that our path
         * structure reflects the proper depth.
         */
        if (keep_root)
                depth = le16_to_cpu(path_root_el(path)->l_tree_depth);

        path->p_tree_depth = depth;
}

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

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

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

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

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

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

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

        /*
         * Right now, no root bh is an extent block, so this helps
         * catch code errors with dinode trees. The assertion can be
         * safely removed if we ever need to insert extent block
         * structures at the root.
         */
        BUG_ON(index == 0);

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

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

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

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

        return path;
}

/*
 * Allocate and initialize a new path based on a disk inode tree.
 */
static struct ocfs2_path *ocfs2_new_inode_path(struct buffer_head *di_bh)
{
        struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
        struct ocfs2_extent_list *el = &di->id2.i_list;

        return ocfs2_new_path(di_bh, el);
}

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

        if (!path)
                goto out;

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

out:
        return ret;
}

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


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

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

        return blkno == blk_end;
}

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

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

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

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

        if (ocfs2_extents_adjacent(ext, insert_rec) &&
            ocfs2_block_extent_contig(inode->i_sb, ext, blkno))
                        return CONTIG_RIGHT;

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

        return CONTIG_NONE;
}

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

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

/*
 * How many free extents have we got before we need more meta data?
 */
int ocfs2_num_free_extents(struct ocfs2_super *osb,
                           struct inode *inode,
                           struct ocfs2_dinode *fe)
{
        int retval;
        struct ocfs2_extent_list *el;
        struct ocfs2_extent_block *eb;
        struct buffer_head *eb_bh = NULL;

        mlog_entry_void();

        if (!OCFS2_IS_VALID_DINODE(fe)) {
                OCFS2_RO_ON_INVALID_DINODE(inode->i_sb, fe);
                retval = -EIO;
                goto bail;
        }

        if (fe->i_last_eb_blk) {
                retval = ocfs2_read_block(osb, le64_to_cpu(fe->i_last_eb_blk),
                                          &eb_bh, OCFS2_BH_CACHED, inode);
                if (retval < 0) {
                        mlog_errno(retval);
                        goto bail;
                }
                eb = (struct ocfs2_extent_block *) eb_bh->b_data;
                el = &eb->h_list;
        } else
                el = &fe->id2.i_list;

        BUG_ON(el->l_tree_depth != 0);

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

        mlog_exit(retval);
        return retval;
}

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

        mlog_entry_void();

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

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

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

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

#ifndef OCFS2_USE_ALL_METADATA_SUBALLOCATORS
                        /* we always use slot zero's suballocator */
                        eb->h_suballoc_slot = 0;
#else
                        eb->h_suballoc_slot = cpu_to_le16(osb->slot_num);
#endif
                        eb->h_suballoc_bit = cpu_to_le16(suballoc_bit_start);
                        eb->h_list.l_count =
                                cpu_to_le16(ocfs2_extent_recs_per_eb(osb->sb));

                        suballoc_bit_start++;
                        first_blkno++;

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

                count += num_got;
        }

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

/*
 * Helper function for ocfs2_add_branch() and ocfs2_shift_tree_depth().
 *
 * Returns the sum of the rightmost extent rec logical offset and
 * cluster count.
 *
 * ocfs2_add_branch() uses this to determine what logical cluster
 * value should be populated into the leftmost new branch records.
 *
 * ocfs2_shift_tree_depth() uses this to determine the # clusters
 * value for the new topmost tree record.
 */
static inline u32 ocfs2_sum_rightmost_rec(struct ocfs2_extent_list  *el)
{
        int i;

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

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

/*
 * Add an entire tree branch to our inode. eb_bh is the extent block
 * to start at, if we don't want to start the branch at the dinode
 * structure.
 *
 * last_eb_bh is required as we have to update it's next_leaf pointer
 * for the new last extent block.
 *
 * the new branch will be 'empty' in the sense that every block will
 * contain a single record with cluster count == 0.
 */
static int ocfs2_add_branch(struct ocfs2_super *osb,
                            handle_t *handle,
                            struct inode *inode,
                            struct buffer_head *fe_bh,
                            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_dinode *fe;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list  *eb_el;
        struct ocfs2_extent_list  *el;
        u32 new_cpos;

        mlog_entry_void();

        BUG_ON(!last_eb_bh);

        fe = (struct ocfs2_dinode *) fe_bh->b_data;

        if (eb_bh) {
                eb = (struct ocfs2_extent_block *) eb_bh->b_data;
                el = &eb->h_list;
        } else
                el = &fe->id2.i_list;

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

        new_blocks = le16_to_cpu(el->l_tree_depth);

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

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

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

        /* Note: new_eb_bhs[new_blocks - 1] is the guy which will be
         * linked with the rest of the tree.
         * conversly, new_eb_bhs[0] is the new bottommost leaf.
         *
         * when we leave the loop, new_last_eb_blk will point to the
         * newest leaf, and next_blkno will point to the topmost extent
         * block. */
        next_blkno = new_last_eb_blk = 0;
        for(i = 0; i < new_blocks; i++) {
                bh = new_eb_bhs[i];
                eb = (struct ocfs2_extent_block *) bh->b_data;
                if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
                        OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
                        status = -EIO;
                        goto bail;
                }
                eb_el = &eb->h_list;

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

                eb->h_next_leaf_blk = 0;
                eb_el->l_tree_depth = cpu_to_le16(i);
                eb_el->l_next_free_rec = cpu_to_le16(1);
                /*
                 * This actually counts as an empty extent as
                 * c_clusters == 0
                 */
                eb_el->l_recs[0].e_cpos = cpu_to_le32(new_cpos);
                eb_el->l_recs[0].e_blkno = cpu_to_le64(next_blkno);
                /*
                 * eb_el isn't always an interior node, but even leaf
                 * nodes want a zero'd flags and reserved field so
                 * this gets the whole 32 bits regardless of use.
                 */
                eb_el->l_recs[0].e_int_clusters = cpu_to_le32(0);
                if (!eb_el->l_tree_depth)
                        new_last_eb_blk = le64_to_cpu(eb->h_blkno);

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

                next_blkno = le64_to_cpu(eb->h_blkno);
        }

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

        /* Link the new branch into the rest of the tree (el will
         * either be on the fe, 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. */
        fe->i_last_eb_blk = cpu_to_le64(new_last_eb_blk);

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

        status = ocfs2_journal_dirty(handle, last_eb_bh);
        if (status < 0)
                mlog_errno(status);
        status = ocfs2_journal_dirty(handle, fe_bh);
        if (status < 0)
                mlog_errno(status);
        if (eb_bh) {
                status = ocfs2_journal_dirty(handle, eb_bh);
                if (status < 0)
                        mlog_errno(status);
        }

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

        mlog_exit(status);
        return status;
}

/*
 * adds another level to the allocation tree.
 * returns back the new extent block so you can add a branch to it
 * after this call.
 */
static int ocfs2_shift_tree_depth(struct ocfs2_super *osb,
                                  handle_t *handle,
                                  struct inode *inode,
                                  struct buffer_head *fe_bh,
                                  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_dinode *fe;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list  *fe_el;
        struct ocfs2_extent_list  *eb_el;

        mlog_entry_void();

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

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

        eb_el = &eb->h_list;
        fe = (struct ocfs2_dinode *) fe_bh->b_data;
        fe_el = &fe->id2.i_list;

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

        /* copy the fe data into the new extent block */
        eb_el->l_tree_depth = fe_el->l_tree_depth;
        eb_el->l_next_free_rec = fe_el->l_next_free_rec;
        for(i = 0; i < le16_to_cpu(fe_el->l_next_free_rec); i++)
                eb_el->l_recs[i] = fe_el->l_recs[i];

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

        status = ocfs2_journal_access(handle, inode, fe_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        new_clusters = ocfs2_sum_rightmost_rec(eb_el);

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

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

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

        mlog_exit(status);
        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 dinode has room. We
 *    pass NULL back in *lowest_eb_bh, but still return '0'
 *
 * 3) the search fails to find anything AND the dinode is full, in
 *    which case we return > 0
 *
 * return status < 0 indicates an error.
 */
static int ocfs2_find_branch_target(struct ocfs2_super *osb,
                                    struct inode *inode,
                                    struct buffer_head *fe_bh,
                                    struct buffer_head **target_bh)
{
        int status = 0, i;
        u64 blkno;
        struct ocfs2_dinode *fe;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list  *el;
        struct buffer_head *bh = NULL;
        struct buffer_head *lowest_bh = NULL;

        mlog_entry_void();

        *target_bh = NULL;

        fe = (struct ocfs2_dinode *) fe_bh->b_data;
        el = &fe->id2.i_list;

        while(le16_to_cpu(el->l_tree_depth) > 1) {
                if (le16_to_cpu(el->l_next_free_rec) == 0) {
                        ocfs2_error(inode->i_sb, "Dinode %llu has empty "
                                    "extent list (next_free_rec == 0)",
                                    (unsigned long long)OCFS2_I(inode)->ip_blkno);
                        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(inode->i_sb, "Dinode %llu has extent "
                                    "list where extent # %d has no physical "
                                    "block start",
                                    (unsigned long long)OCFS2_I(inode)->ip_blkno, i);
                        status = -EIO;
                        goto bail;
                }

                if (bh) {
                        brelse(bh);
                        bh = NULL;
                }

                status = ocfs2_read_block(osb, blkno, &bh, OCFS2_BH_CACHED,
                                          inode);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }

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

                if (le16_to_cpu(el->l_next_free_rec) <
                    le16_to_cpu(el->l_count)) {
                        if (lowest_bh)
                                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' */
        if (!lowest_bh
            && (fe->id2.i_list.l_next_free_rec == fe->id2.i_list.l_count))
                status = 1;

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

        mlog_exit(status);
        return status;
}

/*
 * This is only valid for leaf nodes, which are the only ones that can
 * have empty extents anyway.
 */
static inline int ocfs2_is_empty_extent(struct ocfs2_extent_rec *rec)
{
        return !rec->e_leaf_clusters;
}

/*
 * 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. */
        if (el->l_next_free_rec == el->l_count && !has_empty)
                BUG();

        /*
         * 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;

        mlog(0, "ins %u: index %d, has_empty %d, next_free %d, count %d\n",
             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;

}

/*
 * 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.
 */
static int ocfs2_find_subtree_root(struct inode *inode,
                                   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,
                                "Inode %lu, left depth %u, right depth %u\n"
                                "left leaf blk %llu, right leaf blk %llu\n",
                                inode->i_ino, 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 inode *inode,
                             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;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);

        el = root_el;
        while (el->l_tree_depth) {
                if (le16_to_cpu(el->l_next_free_rec) == 0) {
                        ocfs2_error(inode->i_sb,
                                    "Inode %llu has empty extent list at "
                                    "depth %u\n",
                                    (unsigned long long)oi->ip_blkno,
                                    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(inode->i_sb,
                                    "Inode %llu has bad blkno in extent list "
                                    "at depth %u (index %d)\n",
                                    (unsigned long long)oi->ip_blkno,
                                    le16_to_cpu(el->l_tree_depth), i);
                        ret = -EROFS;
                        goto out;
                }

                brelse(bh);
                bh = NULL;
                ret = ocfs2_read_block(OCFS2_SB(inode->i_sb), blkno,
                                       &bh, OCFS2_BH_CACHED, inode);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                eb = (struct ocfs2_extent_block *) bh->b_data;
                el = &eb->h_list;
                if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
                        OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
                        ret = -EIO;
                        goto out;
                }

                if (le16_to_cpu(el->l_next_free_rec) >
                    le16_to_cpu(el->l_count)) {
                        ocfs2_error(inode->i_sb,
                                    "Inode %llu has bad count in extent list "
                                    "at block %llu (next free=%u, count=%u)\n",
                                    (unsigned long long)oi->ip_blkno,
                                    (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++;
}
static int ocfs2_find_path(struct inode *inode, struct ocfs2_path *path,
                           u32 cpos)
{
        struct find_path_data data;

        data.index = 1;
        data.path = path;
        return __ocfs2_find_path(inode, 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 inode *inode, struct ocfs2_extent_list *root_el,
                    u32 cpos, struct buffer_head **leaf_bh)
{
        int ret;
        struct buffer_head *bh = NULL;

        ret = __ocfs2_find_path(inode, 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);
        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.
 */
static void ocfs2_complete_edge_insert(struct inode *inode, handle_t *handle,
                                       struct ocfs2_path *left_path,
                                       struct ocfs2_path *right_path,
                                       int subtree_index)
{
        int ret, 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--) {
                mlog(0, "Adjust records at index %u\n", 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);

                ret = ocfs2_journal_dirty(handle, left_path->p_node[i].bh);
                if (ret)
                        mlog_errno(ret);

                ret = ocfs2_journal_dirty(handle, right_path->p_node[i].bh);
                if (ret)
                        mlog_errno(ret);

                /*
                 * 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;

        ret = ocfs2_journal_dirty(handle, root_bh);
        if (ret)
                mlog_errno(ret);
}

static int ocfs2_rotate_subtree_right(struct inode *inode,
                                      handle_t *handle,
                                      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(inode->i_sb,
                            "Inode %llu has non-full interior leaf node %llu"
                            "(next free = %u)",
                            (unsigned long long)OCFS2_I(inode)->ip_blkno,
                            (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_journal_access(handle, inode, root_bh,
                                   OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        for(i = subtree_index + 1; i < path_num_items(right_path); i++) {
                ret = ocfs2_journal_access(handle, inode,
                                           right_path->p_node[i].bh,
                                           OCFS2_JOURNAL_ACCESS_WRITE);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_journal_access(handle, inode,
                                           left_path->p_node[i].bh,
                                           OCFS2_JOURNAL_ACCESS_WRITE);
                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_I(inode)->ip_blkno,
                        (unsigned long long)right_leaf_bh->b_blocknr);

        ocfs2_create_empty_extent(right_el);

        ret = ocfs2_journal_dirty(handle, right_leaf_bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /* 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);

        ret = ocfs2_journal_dirty(handle, left_leaf_bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ocfs2_complete_edge_insert(inode, 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.
 */
static 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;
}

static int ocfs2_extend_rotate_transaction(handle_t *handle, int subtree_depth,
                                           struct ocfs2_path *path)
{
        int credits = (path->p_tree_depth - subtree_depth) * 2 + 1;

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

        return 0;
}

/*
 * 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;
}

/*
 * Rotate all the records in a btree right one record, starting at insert_cpos.
 *
 * The path to the rightmost leaf should be passed in.
 *
 * The array is assumed to be large enough to hold an entire path (tree depth).
 *
 * Upon succesful return from this function:
 *
 * - The 'right_path' array will contain a path to the leaf block
 *   whose range contains e_cpos.
 * - That leaf block will have a single empty extent in list index 0.
 * - In the case that the rotation requires a post-insert update,
 *   *ret_left_path will contain a valid path which can be passed to
 *   ocfs2_insert_path().
 */
static int ocfs2_rotate_tree_right(struct inode *inode,
                                   handle_t *handle,
                                   u32 insert_cpos,
                                   struct ocfs2_path *right_path,
                                   struct ocfs2_path **ret_left_path)
{
        int ret, start;
        u32 cpos;
        struct ocfs2_path *left_path = NULL;

        *ret_left_path = NULL;

        left_path = ocfs2_new_path(path_root_bh(right_path),
                                   path_root_el(right_path));
        if (!left_path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_find_cpos_for_left_leaf(inode->i_sb, right_path, &cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        mlog(0, "Insert: %u, first left path cpos: %u\n", 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) {
                mlog(0, "Rotating a tree: ins. cpos: %u, left path cpos: %u\n",
                     insert_cpos, cpos);

                ret = ocfs2_find_path(inode, left_path, cpos);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

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

                if (ocfs2_rotate_requires_path_adjustment(left_path,
                                                          insert_cpos)) {
                        mlog(0, "Path adjustment required\n");

                        /*
                         * 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(inode, left_path, right_path);

                mlog(0, "Subtree root at index %d (blk %llu, depth %d)\n",
                     start,
                     (unsigned long long) right_path->p_node[start].bh->b_blocknr,
                     right_path->p_tree_depth);

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

                ret = ocfs2_rotate_subtree_right(inode, handle, left_path,
                                                 right_path, start);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                /*
                 * 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(inode->i_sb, right_path,
                                                    &cpos);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        }

out:
        ocfs2_free_path(left_path);

out_ret_path:
        return ret;
}

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

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

        /*
         * 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),
                                "inode %lu, depth %u, count %u, next free %u, "
                                "rec.cpos %u, rec.clusters %u, "
                                "insert.cpos %u, insert.clusters %u\n",
                                inode->i_ino,
                                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;
        }

        /*
         * 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 inline void ocfs2_update_dinode_clusters(struct inode *inode,
                                                struct ocfs2_dinode *di,
                                                u32 clusters)
{
        le32_add_cpu(&di->i_clusters, clusters);
        spin_lock(&OCFS2_I(inode)->ip_lock);
        OCFS2_I(inode)->ip_clusters = le32_to_cpu(di->i_clusters);
        spin_unlock(&OCFS2_I(inode)->ip_lock);
}

static int ocfs2_append_rec_to_path(struct inode *inode, handle_t *handle,
                                    struct ocfs2_extent_rec *insert_rec,
                                    struct ocfs2_path *right_path,
                                    struct ocfs2_path **ret_left_path)
{
        int ret, i, next_free;
        struct buffer_head *bh;
        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(inode->i_sb, right_path,
                                                    &left_cpos);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                mlog(0, "Append may need a left path update. cpos: %u, "
                     "left_cpos: %u\n", le32_to_cpu(insert_rec->e_cpos),
                     left_cpos);

                /*
                 * No need to worry if the append is already in the
                 * leftmost leaf.
                 */
                if (left_cpos) {
                        left_path = ocfs2_new_path(path_root_bh(right_path),
                                                   path_root_el(right_path));
                        if (!left_path) {
                                ret = -ENOMEM;
                                mlog_errno(ret);
                                goto out;
                        }

                        ret = ocfs2_find_path(inode, left_path, left_cpos);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }

                        /*
                         * ocfs2_insert_path() will pass the left_path to the
                         * journal for us.
                         */
                }
        }

        ret = ocfs2_journal_access_path(inode, handle, right_path);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        el = path_root_el(right_path);
        bh = path_root_bh(right_path);
        i = 0;
        while (1) {
                struct ocfs2_extent_rec *rec;

                next_free = le16_to_cpu(el->l_next_free_rec);
                if (next_free == 0) {
                        ocfs2_error(inode->i_sb,
                                    "Dinode %llu has a bad extent list",
                                    (unsigned long long)OCFS2_I(inode)->ip_blkno);
                        ret = -EIO;
                        goto out;
                }

                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));

                ret = ocfs2_journal_dirty(handle, bh);
                if (ret)
                        mlog_errno(ret);

                /* Don't touch the leaf node */
                if (++i >= right_path->p_tree_depth)
                        break;

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

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

        return ret;
}

/*
 * This function only does inserts on an allocation b-tree. For dinode
 * lists, ocfs2_insert_at_leaf() is called directly.
 *
 * right_path is the path we want to do the actual insert
 * in. left_path should only be passed in if we need to update that
 * portion of the tree after an edge insert.
 */
static int ocfs2_insert_path(struct inode *inode,
                             handle_t *handle,
                             struct ocfs2_path *left_path,
                             struct ocfs2_path *right_path,
                             struct ocfs2_extent_rec *insert_rec,
                             struct ocfs2_insert_type *insert)
{
        int ret, subtree_index;
        struct buffer_head *leaf_bh = path_leaf_bh(right_path);
        struct ocfs2_extent_list *el;

        /*
         * Pass both paths to the journal. The majority of inserts
         * will be touching all components anyway.
         */
        ret = ocfs2_journal_access_path(inode, handle, right_path);
        if (ret < 0) {
                mlog_errno(ret);
                goto out;
        }

        if (left_path) {
                int credits = handle->h_buffer_credits;

                /*
                 * There's a chance that left_path got passed back to
                 * us without being accounted for in the
                 * journal. Extend our transaction here to be sure we
                 * can change those blocks.
                 */
                credits += left_path->p_tree_depth;

                ret = ocfs2_extend_trans(handle, credits);
                if (ret < 0) {
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_journal_access_path(inode, handle, left_path);
                if (ret < 0) {
                        mlog_errno(ret);
                        goto out;
                }
        }

        el = path_leaf_el(right_path);

        ocfs2_insert_at_leaf(insert_rec, el, insert, inode);
        ret = ocfs2_journal_dirty(handle, leaf_bh);
        if (ret)
                mlog_errno(ret);

        if (left_path) {
                /*
                 * The rotate code has indicated that we need to fix
                 * up portions of the tree after the insert.
                 *
                 * XXX: Should we extend the transaction here?
                 */
                subtree_index = ocfs2_find_subtree_root(inode, left_path,
                                                        right_path);
                ocfs2_complete_edge_insert(inode, handle, left_path,
                                           right_path, subtree_index);
        }

        ret = 0;
out:
        return ret;
}

static int ocfs2_do_insert_extent(struct inode *inode,
                                  handle_t *handle,
                                  struct buffer_head *di_bh,
                                  struct ocfs2_extent_rec *insert_rec,
                                  struct ocfs2_insert_type *type)
{
        int ret, rotate = 0;
        u32 cpos;
        struct ocfs2_path *right_path = NULL;
        struct ocfs2_path *left_path = NULL;
        struct ocfs2_dinode *di;
        struct ocfs2_extent_list *el;

        di = (struct ocfs2_dinode *) di_bh->b_data;
        el = &di->id2.i_list;

        ret = ocfs2_journal_access(handle, inode, di_bh,
                                   OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        if (le16_to_cpu(el->l_tree_depth) == 0) {
                ocfs2_insert_at_leaf(insert_rec, el, type, inode);
                goto out_update_clusters;
        }

        right_path = ocfs2_new_inode_path(di_bh);
        if (!right_path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        /*
         * Determine the path to start with. Rotations need the
         * rightmost path, everything else can go directly to the
         * target leaf.
         */
        cpos = le32_to_cpu(insert_rec->e_cpos);
        if (type->ins_appending == APPEND_NONE &&
            type->ins_contig == CONTIG_NONE) {
                rotate = 1;
                cpos = UINT_MAX;
        }

        ret = ocfs2_find_path(inode, right_path, cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /*
         * Rotations and appends need special treatment - they modify
         * parts of the tree's above them.
         *
         * Both might pass back a path immediate to the left of the
         * one being inserted to. This will be cause
         * ocfs2_insert_path() to modify the rightmost records of
         * left_path to account for an edge insert.
         *
         * XXX: When modifying this code, keep in mind that an insert
         * can wind up skipping both of these two special cases...
         */
        if (rotate) {
                ret = ocfs2_rotate_tree_right(inode, handle,
                                              le32_to_cpu(insert_rec->e_cpos),
                                              right_path, &left_path);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        } else if (type->ins_appending == APPEND_TAIL
                   && type->ins_contig != CONTIG_LEFT) {
                ret = ocfs2_append_rec_to_path(inode, handle, insert_rec,
                                               right_path, &left_path);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        }

        ret = ocfs2_insert_path(inode, handle, left_path, right_path,
                                insert_rec, type);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

out_update_clusters:
        ocfs2_update_dinode_clusters(inode, di,
                                     le16_to_cpu(insert_rec->e_leaf_clusters));

        ret = ocfs2_journal_dirty(handle, di_bh);
        if (ret)
                mlog_errno(ret);

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

        return ret;
}

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

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

        for(i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
                contig_type = ocfs2_extent_contig(inode, &el->l_recs[i],
                                                  insert_rec);
                if (contig_type != CONTIG_NONE) {
                        insert->ins_contig_index = i;
                        break;
                }
        }
        insert->ins_contig = contig_type;
}

/*
 * This should only be called against the righmost leaf extent list.
 *
 * ocfs2_figure_appending_type() will figure out whether we'll have to
 * insert at the tail of the rightmost leaf.
 *
 * This should also work against the dinode list for tree's with 0
 * depth. If we consider the dinode list to be the rightmost leaf node
 * then the logic here makes sense.
 */
static void ocfs2_figure_appending_type(struct ocfs2_insert_type *insert,
                                        struct ocfs2_extent_list *el,
                                        struct ocfs2_extent_rec *insert_rec)
{
        int i;
        u32 cpos = le32_to_cpu(insert_rec->e_cpos);
        struct ocfs2_extent_rec *rec;

        insert->ins_appending = APPEND_NONE;

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

        if (!el->l_next_free_rec)
                goto set_tail_append;

        if (ocfs2_is_empty_extent(&el->l_recs[0])) {
                /* Were all records empty? */
                if (le16_to_cpu(el->l_next_free_rec) == 1)
                        goto set_tail_append;
        }

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

        if (cpos >=
            (le32_to_cpu(rec->e_cpos) + le16_to_cpu(rec->e_leaf_clusters)))
                goto set_tail_append;

        return;

set_tail_append:
        insert->ins_appending = APPEND_TAIL;
}

/*
 * Helper function called at the begining of an insert.
 *
 * This computes a few things that are commonly used in the process of
 * inserting into the btree:
 *   - Whether the new extent is contiguous with an existing one.
 *   - The current tree depth.
 *   - Whether the insert is an appending one.
 *   - The total # of free records in the tree.
 *
 * All of the information is stored on the ocfs2_insert_type
 * structure.
 */
static int ocfs2_figure_insert_type(struct inode *inode,
                                    struct buffer_head *di_bh,
                                    struct buffer_head **last_eb_bh,
                                    struct ocfs2_extent_rec *insert_rec,
                                    struct ocfs2_insert_type *insert)
{
        int ret;
        struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list *el;
        struct ocfs2_path *path = NULL;
        struct buffer_head *bh = NULL;

        el = &di->id2.i_list;
        insert->ins_tree_depth = le16_to_cpu(el->l_tree_depth);

        if (el->l_tree_depth) {
                /*
                 * If we have tree depth, we read in the
                 * rightmost extent block ahead of time as
                 * ocfs2_figure_insert_type() and ocfs2_add_branch()
                 * may want it later.
                 */
                ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
                                       le64_to_cpu(di->i_last_eb_blk), &bh,
                                       OCFS2_BH_CACHED, inode);
                if (ret) {
                        mlog_exit(ret);
                        goto out;
                }
                eb = (struct ocfs2_extent_block *) bh->b_data;
                el = &eb->h_list;
        }

        /*
         * Unless we have a contiguous insert, we'll need to know if
         * there is room left in our allocation tree for another
         * extent record.
         *
         * XXX: This test is simplistic, we can search for empty
         * extent records too.
         */
        insert->ins_free_records = le16_to_cpu(el->l_count) -
                le16_to_cpu(el->l_next_free_rec);

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

        path = ocfs2_new_inode_path(di_bh);
        if (!path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        /*
         * In the case that we're inserting past what the tree
         * currently accounts for, ocfs2_find_path() will return for
         * us the rightmost tree path. This is accounted for below in
         * the appending code.
         */
        ret = ocfs2_find_path(inode, path, le32_to_cpu(insert_rec->e_cpos));
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        el = path_leaf_el(path);

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

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

        /*
         * Ok, so we can simply compare against last_eb to figure out
         * whether the path doesn't exist. This will only happen in
         * the case that we're doing a tail append, so maybe we can
         * take advantage of that information somehow.
         */
        if (le64_to_cpu(di->i_last_eb_blk) == path_leaf_bh(path)->b_blocknr) {
                /*
                 * Ok, ocfs2_find_path() returned us the rightmost
                 * tree path. This might be an appending insert. There are
                 * two cases:
                 *    1) We're doing a true append at the tail:
                 *      -This might even be off the end of the leaf
                 *    2) We're "appending" by rotating in the tail
                 */
                ocfs2_figure_appending_type(insert, el, insert_rec);
        }

out:
        ocfs2_free_path(path);

        if (ret == 0)
                *last_eb_bh = bh;
        else
                brelse(bh);
        return ret;
}

/*
 * Insert an extent into an inode btree.
 *
 * The caller needs to update fe->i_clusters
 */
int ocfs2_insert_extent(struct ocfs2_super *osb,
                        handle_t *handle,
                        struct inode *inode,
                        struct buffer_head *fe_bh,
                        u32 cpos,
                        u64 start_blk,
                        u32 new_clusters,
                        struct ocfs2_alloc_context *meta_ac)
{
        int status, shift;
        struct buffer_head *last_eb_bh = NULL;
        struct buffer_head *bh = NULL;
        struct ocfs2_insert_type insert = {0, };
        struct ocfs2_extent_rec rec;

        mlog(0, "add %u clusters at position %u to inode %llu\n",
             new_clusters, cpos, (unsigned long long)OCFS2_I(inode)->ip_blkno);

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

        memset(&rec, 0, sizeof(rec));
        rec.e_cpos = cpu_to_le32(cpos);
        rec.e_blkno = cpu_to_le64(start_blk);
        rec.e_leaf_clusters = cpu_to_le16(new_clusters);

        status = ocfs2_figure_insert_type(inode, fe_bh, &last_eb_bh, &rec,
                                          &insert);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        mlog(0, "Insert.appending: %u, Insert.Contig: %u, "
             "Insert.contig_index: %d, Insert.free_records: %d, "
             "Insert.tree_depth: %d\n",
             insert.ins_appending, insert.ins_contig, insert.ins_contig_index,
             insert.ins_free_records, insert.ins_tree_depth);

        /*
         * Avoid growing the tree unless we're out of records and the
         * insert type requres one.
         */
        if (insert.ins_contig != CONTIG_NONE || insert.ins_free_records)
                goto out_add;

        shift = ocfs2_find_branch_target(osb, inode, fe_bh, &bh);
        if (shift < 0) {
                status = shift;
                mlog_errno(status);
                goto bail;
        }

        /* 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);
                mlog(0, "need to shift tree depth "
                     "(current = %d)\n", insert.ins_tree_depth);

                /* ocfs2_shift_tree_depth will return us a buffer with
                 * the new extent block (so we can pass that to
                 * ocfs2_add_branch). */
                status = ocfs2_shift_tree_depth(osb, handle, inode, fe_bh,
                                                meta_ac, &bh);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
                insert.ins_tree_depth++;
                /* Special case: we have room now if we shifted from
                 * tree_depth 0 */
                if (insert.ins_tree_depth == 1)
                        goto out_add;
        }

        /* call ocfs2_add_branch to add the final part of the tree with
         * the new data. */
        mlog(0, "add branch. bh = %p\n", bh);
        status = ocfs2_add_branch(osb, handle, inode, fe_bh, bh, last_eb_bh,
                                  meta_ac);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

out_add:
        /* Finally, we can add clusters. This might rotate the tree for us. */
        status = ocfs2_do_insert_extent(inode, handle, fe_bh, &rec, &insert);
        if (status < 0)
                mlog_errno(status);
        else
                ocfs2_extent_map_insert_rec(inode, &rec);

bail:
        if (bh)
                brelse(bh);

        if (last_eb_bh)
                brelse(last_eb_bh);

        mlog_exit(status);
        return status;
}

static inline int ocfs2_truncate_log_needs_flush(struct ocfs2_super *osb)
{
        struct buffer_head *tl_bh = osb->osb_tl_bh;
        struct ocfs2_dinode *di;
        struct ocfs2_truncate_log *tl;

        di = (struct ocfs2_dinode *) tl_bh->b_data;
        tl = &di->id2.i_dealloc;

        mlog_bug_on_msg(le16_to_cpu(tl->tl_used) > le16_to_cpu(tl->tl_count),
                        "slot %d, invalid truncate log parameters: used = "
                        "%u, count = %u\n", osb->slot_num,
                        le16_to_cpu(tl->tl_used), le16_to_cpu(tl->tl_count));
        return le16_to_cpu(tl->tl_used) == le16_to_cpu(tl->tl_count);
}

static int ocfs2_truncate_log_can_coalesce(struct ocfs2_truncate_log *tl,
                                           unsigned int new_start)
{
        unsigned int tail_index;
        unsigned int current_tail;

        /* No records, nothing to coalesce */
        if (!le16_to_cpu(tl->tl_used))
                return 0;

        tail_index = le16_to_cpu(tl->tl_used) - 1;
        current_tail = le32_to_cpu(tl->tl_recs[tail_index].t_start);
        current_tail += le32_to_cpu(tl->tl_recs[tail_index].t_clusters);

        return current_tail == new_start;
}

static int ocfs2_truncate_log_append(struct ocfs2_super *osb,
                                     handle_t *handle,
                                     u64 start_blk,
                                     unsigned int num_clusters)
{
        int status, index;
        unsigned int start_cluster, tl_count;
        struct inode *tl_inode = osb->osb_tl_inode;
        struct buffer_head *tl_bh = osb->osb_tl_bh;
        struct ocfs2_dinode *di;
        struct ocfs2_truncate_log *tl;

        mlog_entry("start_blk = %llu, num_clusters = %u\n",
                   (unsigned long long)start_blk, num_clusters);

        BUG_ON(mutex_trylock(&tl_inode->i_mutex));

        start_cluster = ocfs2_blocks_to_clusters(osb->sb, start_blk);

        di = (struct ocfs2_dinode *) tl_bh->b_data;
        tl = &di->id2.i_dealloc;
        if (!OCFS2_IS_VALID_DINODE(di)) {
                OCFS2_RO_ON_INVALID_DINODE(osb->sb, di);
                status = -EIO;
                goto bail;
        }

        tl_count = le16_to_cpu(tl->tl_count);
        mlog_bug_on_msg(tl_count > ocfs2_truncate_recs_per_inode(osb->sb) ||
                        tl_count == 0,
                        "Truncate record count on #%llu invalid "
                        "wanted %u, actual %u\n",
                        (unsigned long long)OCFS2_I(tl_inode)->ip_blkno,
                        ocfs2_truncate_recs_per_inode(osb->sb),
                        le16_to_cpu(tl->tl_count));

        /* Caller should have known to flush before calling us. */
        index = le16_to_cpu(tl->tl_used);
        if (index >= tl_count) {
                status = -ENOSPC;
                mlog_errno(status);
                goto bail;
        }

        status = ocfs2_journal_access(handle, tl_inode, tl_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        mlog(0, "Log truncate of %u clusters starting at cluster %u to "
             "%llu (index = %d)\n", num_clusters, start_cluster,
             (unsigned long long)OCFS2_I(tl_inode)->ip_blkno, index);

        if (ocfs2_truncate_log_can_coalesce(tl, start_cluster)) {
                /*
                 * Move index back to the record we are coalescing with.
                 * ocfs2_truncate_log_can_coalesce() guarantees nonzero
                 */
                index--;

                num_clusters += le32_to_cpu(tl->tl_recs[index].t_clusters);
                mlog(0, "Coalesce with index %u (start = %u, clusters = %u)\n",
                     index, le32_to_cpu(tl->tl_recs[index].t_start),
                     num_clusters);
        } else {
                tl->tl_recs[index].t_start = cpu_to_le32(start_cluster);
                tl->tl_used = cpu_to_le16(index + 1);
        }
        tl->tl_recs[index].t_clusters = cpu_to_le32(num_clusters);

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

bail:
        mlog_exit(status);
        return status;
}

static int ocfs2_replay_truncate_records(struct ocfs2_super *osb,
                                         handle_t *handle,
                                         struct inode *data_alloc_inode,
                                         struct buffer_head *data_alloc_bh)
{
        int status = 0;
        int i;
        unsigned int num_clusters;
        u64 start_blk;
        struct ocfs2_truncate_rec rec;
        struct ocfs2_dinode *di;
        struct ocfs2_truncate_log *tl;
        struct inode *tl_inode = osb->osb_tl_inode;
        struct buffer_head *tl_bh = osb->osb_tl_bh;

        mlog_entry_void();

        di = (struct ocfs2_dinode *) tl_bh->b_data;
        tl = &di->id2.i_dealloc;
        i = le16_to_cpu(tl->tl_used) - 1;
        while (i >= 0) {
                /* Caller has given us at least enough credits to
                 * update the truncate log dinode */
                status = ocfs2_journal_access(handle, tl_inode, tl_bh,
                                              OCFS2_JOURNAL_ACCESS_WRITE);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }

                tl->tl_used = cpu_to_le16(i);

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

                /* TODO: Perhaps we can calculate the bulk of the
                 * credits up front rather than extending like
                 * this. */
                status = ocfs2_extend_trans(handle,
                                            OCFS2_TRUNCATE_LOG_FLUSH_ONE_REC);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }

                rec = tl->tl_recs[i];
                start_blk = ocfs2_clusters_to_blocks(data_alloc_inode->i_sb,
                                                    le32_to_cpu(rec.t_start));
                num_clusters = le32_to_cpu(rec.t_clusters);

                /* if start_blk is not set, we ignore the record as
                 * invalid. */
                if (start_blk) {
                        mlog(0, "free record %d, start = %u, clusters = %u\n",
                             i, le32_to_cpu(rec.t_start), num_clusters);

                        status = ocfs2_free_clusters(handle, data_alloc_inode,
                                                     data_alloc_bh, start_blk,
                                                     num_clusters);
                        if (status < 0) {
                                mlog_errno(status);
                                goto bail;
                        }
                }
                i--;
        }

bail:
        mlog_exit(status);
        return status;
}

/* Expects you to already be holding tl_inode->i_mutex */
static int __ocfs2_flush_truncate_log(struct ocfs2_super *osb)
{
        int status;
        unsigned int num_to_flush;
        handle_t *handle;
        struct inode *tl_inode = osb->osb_tl_inode;
        struct inode *data_alloc_inode = NULL;
        struct buffer_head *tl_bh = osb->osb_tl_bh;
        struct buffer_head *data_alloc_bh = NULL;
        struct ocfs2_dinode *di;
        struct ocfs2_truncate_log *tl;

        mlog_entry_void();

        BUG_ON(mutex_trylock(&tl_inode->i_mutex));

        di = (struct ocfs2_dinode *) tl_bh->b_data;
        tl = &di->id2.i_dealloc;
        if (!OCFS2_IS_VALID_DINODE(di)) {
                OCFS2_RO_ON_INVALID_DINODE(osb->sb, di);
                status = -EIO;
                goto out;
        }

        num_to_flush = le16_to_cpu(tl->tl_used);
        mlog(0, "Flush %u records from truncate log #%llu\n",
             num_to_flush, (unsigned long long)OCFS2_I(tl_inode)->ip_blkno);
        if (!num_to_flush) {
                status = 0;
                goto out;
        }

        data_alloc_inode = ocfs2_get_system_file_inode(osb,
                                                       GLOBAL_BITMAP_SYSTEM_INODE,
                                                       OCFS2_INVALID_SLOT);
        if (!data_alloc_inode) {
                status = -EINVAL;
                mlog(ML_ERROR, "Could not get bitmap inode!\n");
                goto out;
        }

        mutex_lock(&data_alloc_inode->i_mutex);

        status = ocfs2_meta_lock(data_alloc_inode, &data_alloc_bh, 1);
        if (status < 0) {
                mlog_errno(status);
                goto out_mutex;
        }

        handle = ocfs2_start_trans(osb, OCFS2_TRUNCATE_LOG_UPDATE);
        if (IS_ERR(handle)) {
                status = PTR_ERR(handle);
                mlog_errno(status);
                goto out_unlock;
        }

        status = ocfs2_replay_truncate_records(osb, handle, data_alloc_inode,
                                               data_alloc_bh);
        if (status < 0)
                mlog_errno(status);

        ocfs2_commit_trans(osb, handle);

out_unlock:
        brelse(data_alloc_bh);
        ocfs2_meta_unlock(data_alloc_inode, 1);

out_mutex:
        mutex_unlock(&data_alloc_inode->i_mutex);
        iput(data_alloc_inode);

out:
        mlog_exit(status);
        return status;
}

int ocfs2_flush_truncate_log(struct ocfs2_super *osb)
{
        int status;
        struct inode *tl_inode = osb->osb_tl_inode;

        mutex_lock(&tl_inode->i_mutex);
        status = __ocfs2_flush_truncate_log(osb);
        mutex_unlock(&tl_inode->i_mutex);

        return status;
}

static void ocfs2_truncate_log_worker(struct work_struct *work)
{
        int status;
        struct ocfs2_super *osb =
                container_of(work, struct ocfs2_super,
                             osb_truncate_log_wq.work);

        mlog_entry_void();

        status = ocfs2_flush_truncate_log(osb);
        if (status < 0)
                mlog_errno(status);

        mlog_exit(status);
}

#define OCFS2_TRUNCATE_LOG_FLUSH_INTERVAL (2 * HZ)
void ocfs2_schedule_truncate_log_flush(struct ocfs2_super *osb,
                                       int cancel)
{
        if (osb->osb_tl_inode) {
                /* We want to push off log flushes while truncates are
                 * still running. */
                if (cancel)
                        cancel_delayed_work(&osb->osb_truncate_log_wq);

                queue_delayed_work(ocfs2_wq, &osb->osb_truncate_log_wq,
                                   OCFS2_TRUNCATE_LOG_FLUSH_INTERVAL);
        }
}

static int ocfs2_get_truncate_log_info(struct ocfs2_super *osb,
                                       int slot_num,
                                       struct inode **tl_inode,
                                       struct buffer_head **tl_bh)
{
        int status;
        struct inode *inode = NULL;
        struct buffer_head *bh = NULL;

        inode = ocfs2_get_system_file_inode(osb,
                                           TRUNCATE_LOG_SYSTEM_INODE,
                                           slot_num);
        if (!inode) {
                status = -EINVAL;
                mlog(ML_ERROR, "Could not get load truncate log inode!\n");
                goto bail;
        }

        status = ocfs2_read_block(osb, OCFS2_I(inode)->ip_blkno, &bh,
                                  OCFS2_BH_CACHED, inode);
        if (status < 0) {
                iput(inode);
                mlog_errno(status);
                goto bail;
        }

        *tl_inode = inode;
        *tl_bh    = bh;
bail:
        mlog_exit(status);
        return status;
}

/* called during the 1st stage of node recovery. we stamp a clean
 * truncate log and pass back a copy for processing later. if the
 * truncate log does not require processing, a *tl_copy is set to
 * NULL. */
int ocfs2_begin_truncate_log_recovery(struct ocfs2_super *osb,
                                      int slot_num,
                                      struct ocfs2_dinode **tl_copy)
{
        int status;
        struct inode *tl_inode = NULL;
        struct buffer_head *tl_bh = NULL;
        struct ocfs2_dinode *di;
        struct ocfs2_truncate_log *tl;

        *tl_copy = NULL;

        mlog(0, "recover truncate log from slot %d\n", slot_num);

        status = ocfs2_get_truncate_log_info(osb, slot_num, &tl_inode, &tl_bh);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        di = (struct ocfs2_dinode *) tl_bh->b_data;
        tl = &di->id2.i_dealloc;
        if (!OCFS2_IS_VALID_DINODE(di)) {
                OCFS2_RO_ON_INVALID_DINODE(tl_inode->i_sb, di);
                status = -EIO;
                goto bail;
        }

        if (le16_to_cpu(tl->tl_used)) {
                mlog(0, "We'll have %u logs to recover\n",
                     le16_to_cpu(tl->tl_used));

                *tl_copy = kmalloc(tl_bh->b_size, GFP_KERNEL);
                if (!(*tl_copy)) {
                        status = -ENOMEM;
                        mlog_errno(status);
                        goto bail;
                }

                /* Assuming the write-out below goes well, this copy
                 * will be passed back to recovery for processing. */
                memcpy(*tl_copy, tl_bh->b_data, tl_bh->b_size);

                /* All we need to do to clear the truncate log is set
                 * tl_used. */
                tl->tl_used = 0;

                status = ocfs2_write_block(osb, tl_bh, tl_inode);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
        }

bail:
        if (tl_inode)
                iput(tl_inode);
        if (tl_bh)
                brelse(tl_bh);

        if (status < 0 && (*tl_copy)) {
                kfree(*tl_copy);
                *tl_copy = NULL;
        }

        mlog_exit(status);
        return status;
}

int ocfs2_complete_truncate_log_recovery(struct ocfs2_super *osb,
                                         struct ocfs2_dinode *tl_copy)
{
        int status = 0;
        int i;
        unsigned int clusters, num_recs, start_cluster;
        u64 start_blk;
        handle_t *handle;
        struct inode *tl_inode = osb->osb_tl_inode;
        struct ocfs2_truncate_log *tl;

        mlog_entry_void();

        if (OCFS2_I(tl_inode)->ip_blkno == le64_to_cpu(tl_copy->i_blkno)) {
                mlog(ML_ERROR, "Asked to recover my own truncate log!\n");
                return -EINVAL;
        }

        tl = &tl_copy->id2.i_dealloc;
        num_recs = le16_to_cpu(tl->tl_used);
        mlog(0, "cleanup %u records from %llu\n", num_recs,
             (unsigned long long)le64_to_cpu(tl_copy->i_blkno));

        mutex_lock(&tl_inode->i_mutex);
        for(i = 0; i < num_recs; i++) {
                if (ocfs2_truncate_log_needs_flush(osb)) {
                        status = __ocfs2_flush_truncate_log(osb);
                        if (status < 0) {
                                mlog_errno(status);
                                goto bail_up;
                        }
                }

                handle = ocfs2_start_trans(osb, OCFS2_TRUNCATE_LOG_UPDATE);
                if (IS_ERR(handle)) {
                        status = PTR_ERR(handle);
                        mlog_errno(status);
                        goto bail_up;
                }

                clusters = le32_to_cpu(tl->tl_recs[i].t_clusters);
                start_cluster = le32_to_cpu(tl->tl_recs[i].t_start);
                start_blk = ocfs2_clusters_to_blocks(osb->sb, start_cluster);

                status = ocfs2_truncate_log_append(osb, handle,
                                                   start_blk, clusters);
                ocfs2_commit_trans(osb, handle);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail_up;
                }
        }

bail_up:
        mutex_unlock(&tl_inode->i_mutex);

        mlog_exit(status);
        return status;
}

void ocfs2_truncate_log_shutdown(struct ocfs2_super *osb)
{
        int status;
        struct inode *tl_inode = osb->osb_tl_inode;

        mlog_entry_void();

        if (tl_inode) {
                cancel_delayed_work(&osb->osb_truncate_log_wq);
                flush_workqueue(ocfs2_wq);

                status = ocfs2_flush_truncate_log(osb);
                if (status < 0)
                        mlog_errno(status);

                brelse(osb->osb_tl_bh);
                iput(osb->osb_tl_inode);
        }

        mlog_exit_void();
}

int ocfs2_truncate_log_init(struct ocfs2_super *osb)
{
        int status;
        struct inode *tl_inode = NULL;
        struct buffer_head *tl_bh = NULL;

        mlog_entry_void();

        status = ocfs2_get_truncate_log_info(osb,
                                             osb->slot_num,
                                             &tl_inode,
                                             &tl_bh);
        if (status < 0)
                mlog_errno(status);

        /* ocfs2_truncate_log_shutdown keys on the existence of
         * osb->osb_tl_inode so we don't set any of the osb variables
         * until we're sure all is well. */
        INIT_DELAYED_WORK(&osb->osb_truncate_log_wq,
                          ocfs2_truncate_log_worker);
        osb->osb_tl_bh    = tl_bh;
        osb->osb_tl_inode = tl_inode;

        mlog_exit(status);
        return status;
}

/* This function will figure out whether the currently last extent
 * block will be deleted, and if it will, what the new last extent
 * block will be so we can update his h_next_leaf_blk field, as well
 * as the dinodes i_last_eb_blk */
static int ocfs2_find_new_last_ext_blk(struct inode *inode,
                                       unsigned int clusters_to_del,
                                       struct ocfs2_path *path,
                                       struct buffer_head **new_last_eb)
{
        int next_free, ret = 0;
        u32 cpos;
        struct ocfs2_extent_rec *rec;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list *el;
        struct buffer_head *bh = NULL;

        *new_last_eb = NULL;

        /* we have no tree, so of course, no last_eb. */
        if (!path->p_tree_depth)
                goto out;

        /* trunc to zero special case - this makes tree_depth = 0
         * regardless of what it is.  */
        if (OCFS2_I(inode)->ip_clusters == clusters_to_del)
                goto out;

        el = path_leaf_el(path);
        BUG_ON(!el->l_next_free_rec);

        /*
         * Make sure that this extent list will actually be empty
         * after we clear away the data. We can shortcut out if
         * there's more than one non-empty extent in the
         * list. Otherwise, a check of the remaining extent is
         * necessary.
         */
        next_free = le16_to_cpu(el->l_next_free_rec);
        rec = NULL;
        if (ocfs2_is_empty_extent(&el->l_recs[0])) {
                if (next_free > 2)
                        goto out;

                /* We may have a valid extent in index 1, check it. */
                if (next_free == 2)
                        rec = &el->l_recs[1];

                /*
                 * Fall through - no more nonempty extents, so we want
                 * to delete this leaf.
                 */
        } else {
                if (next_free > 1)
                        goto out;

                rec = &el->l_recs[0];
        }

        if (rec) {
                /*
                 * Check it we'll only be trimming off the end of this
                 * cluster.
                 */
                if (le16_to_cpu(rec->e_leaf_clusters) > clusters_to_del)
                        goto out;
        }

        ret = ocfs2_find_cpos_for_left_leaf(inode->i_sb, path, &cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_find_leaf(inode, path_root_el(path), cpos, &bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        eb = (struct ocfs2_extent_block *) bh->b_data;
        el = &eb->h_list;
        if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
                OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
                ret = -EROFS;
                goto out;
        }

        *new_last_eb = bh;
        get_bh(*new_last_eb);
        mlog(0, "returning block %llu, (cpos: %u)\n",
             (unsigned long long)le64_to_cpu(eb->h_blkno), cpos);
out:
        brelse(bh);

        return ret;
}

/*
 * Trim some clusters off the rightmost edge of a tree. Only called
 * during truncate.
 *
 * The caller needs to:
 *   - start journaling of each path component.
 *   - compute and fully set up any new last ext block
 */
static int ocfs2_trim_tree(struct inode *inode, struct ocfs2_path *path,
                           handle_t *handle, struct ocfs2_truncate_context *tc,
                           u32 clusters_to_del, u64 *delete_start)
{
        int ret, i, index = path->p_tree_depth;
        u32 new_edge = 0;
        u64 deleted_eb = 0;
        struct buffer_head *bh;
        struct ocfs2_extent_list *el;
        struct ocfs2_extent_rec *rec;

        *delete_start = 0;

        while (index >= 0) {
                bh = path->p_node[index].bh;
                el = path->p_node[index].el;

                mlog(0, "traveling tree (index = %d, block = %llu)\n",
                     index,  (unsigned long long)bh->b_blocknr);

                BUG_ON(le16_to_cpu(el->l_next_free_rec) == 0);

                if (index !=
                    (path->p_tree_depth - le16_to_cpu(el->l_tree_depth))) {
                        ocfs2_error(inode->i_sb,
                                    "Inode %lu has invalid ext. block %llu",
                                    inode->i_ino,
                                    (unsigned long long)bh->b_blocknr);
                        ret = -EROFS;
                        goto out;
                }

find_tail_record:
                i = le16_to_cpu(el->l_next_free_rec) - 1;
                rec = &el->l_recs[i];

                mlog(0, "Extent list before: record %d: (%u, %u, %llu), "
                     "next = %u\n", i, le32_to_cpu(rec->e_cpos),
                     ocfs2_rec_clusters(el, rec),
                     (unsigned long long)le64_to_cpu(rec->e_blkno),
                     le16_to_cpu(el->l_next_free_rec));

                BUG_ON(ocfs2_rec_clusters(el, rec) < clusters_to_del);

                if (le16_to_cpu(el->l_tree_depth) == 0) {
                        /*
                         * If the leaf block contains a single empty
                         * extent and no records, we can just remove
                         * the block.
                         */
                        if (i == 0 && ocfs2_is_empty_extent(rec)) {
                                memset(rec, 0,
                                       sizeof(struct ocfs2_extent_rec));
                                el->l_next_free_rec = cpu_to_le16(0);

                                goto delete;
                        }

                        /*
                         * Remove any empty extents by shifting things
                         * left. That should make life much easier on
                         * the code below. This condition is rare
                         * enough that we shouldn't see a performance
                         * hit.
                         */
                        if (ocfs2_is_empty_extent(&el->l_recs[0])) {
                                le16_add_cpu(&el->l_next_free_rec, -1);

                                for(i = 0;
                                    i < le16_to_cpu(el->l_next_free_rec); i++)
                                        el->l_recs[i] = el->l_recs[i + 1];

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

                                /*
                                 * We've modified our extent list. The
                                 * simplest way to handle this change
                                 * is to being the search from the
                                 * start again.
                                 */
                                goto find_tail_record;
                        }

                        le16_add_cpu(&rec->e_leaf_clusters, -clusters_to_del);

                        /*
                         * We'll use "new_edge" on our way back up the
                         * tree to know what our rightmost cpos is.
                         */
                        new_edge = le16_to_cpu(rec->e_leaf_clusters);
                        new_edge += le32_to_cpu(rec->e_cpos);

                        /*
                         * The caller will use this to delete data blocks.
                         */
                        *delete_start = le64_to_cpu(rec->e_blkno)
                                + ocfs2_clusters_to_blocks(inode->i_sb,
                                        le16_to_cpu(rec->e_leaf_clusters));

                        /*
                         * If it's now empty, remove this record.
                         */
                        if (le16_to_cpu(rec->e_leaf_clusters) == 0) {
                                memset(rec, 0,
                                       sizeof(struct ocfs2_extent_rec));
                                le16_add_cpu(&el->l_next_free_rec, -1);
                        }
                } else {
                        if (le64_to_cpu(rec->e_blkno) == deleted_eb) {
                                memset(rec, 0,
                                       sizeof(struct ocfs2_extent_rec));
                                le16_add_cpu(&el->l_next_free_rec, -1);

                                goto delete;
                        }

                        /* Can this actually happen? */
                        if (le16_to_cpu(el->l_next_free_rec) == 0)
                                goto delete;

                        /*
                         * We never actually deleted any clusters
                         * because our leaf was empty. There's no
                         * reason to adjust the rightmost edge then.
                         */
                        if (new_edge == 0)
                                goto delete;

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

                         /*
                          * A deleted child record should have been
                          * caught above.
                          */
                         BUG_ON(le32_to_cpu(rec->e_int_clusters) == 0);
                }

delete:
                ret = ocfs2_journal_dirty(handle, bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                mlog(0, "extent list container %llu, after: record %d: "
                     "(%u, %u, %llu), next = %u.\n",
                     (unsigned long long)bh->b_blocknr, i,
                     le32_to_cpu(rec->e_cpos), ocfs2_rec_clusters(el, rec),
                     (unsigned long long)le64_to_cpu(rec->e_blkno),
                     le16_to_cpu(el->l_next_free_rec));

                /*
                 * We must be careful to only attempt delete of an
                 * extent block (and not the root inode block).
                 */
                if (index > 0 && le16_to_cpu(el->l_next_free_rec) == 0) {
                        struct ocfs2_extent_block *eb =
                                (struct ocfs2_extent_block *)bh->b_data;

                        /*
                         * Save this for use when processing the
                         * parent block.
                         */
                        deleted_eb = le64_to_cpu(eb->h_blkno);

                        mlog(0, "deleting this extent block.\n");

                        ocfs2_remove_from_cache(inode, bh);

                        BUG_ON(ocfs2_rec_clusters(el, &el->l_recs[0]));
                        BUG_ON(le32_to_cpu(el->l_recs[0].e_cpos));
                        BUG_ON(le64_to_cpu(el->l_recs[0].e_blkno));

                        if (le16_to_cpu(eb->h_suballoc_slot) == 0) {
                                /*
                                 * This code only understands how to
                                 * lock the suballocator in slot 0,
                                 * which is fine because allocation is
                                 * only ever done out of that
                                 * suballocator too. A future version
                                 * might change that however, so avoid
                                 * a free if we don't know how to
                                 * handle it. This way an fs incompat
                                 * bit will not be necessary.
                                 */
                                ret = ocfs2_free_extent_block(handle,
                                                              tc->tc_ext_alloc_inode,
                                                              tc->tc_ext_alloc_bh,
                                                              eb);

                                /* An error here is not fatal. */
                                if (ret < 0)
                                        mlog_errno(ret);
                        }
                } else {
                        deleted_eb = 0;
                }

                index--;
        }

        ret = 0;
out:
        return ret;
}

static int ocfs2_do_truncate(struct ocfs2_super *osb,
                             unsigned int clusters_to_del,
                             struct inode *inode,
                             struct buffer_head *fe_bh,
                             handle_t *handle,
                             struct ocfs2_truncate_context *tc,
                             struct ocfs2_path *path)
{
        int status;
        struct ocfs2_dinode *fe;
        struct ocfs2_extent_block *last_eb = NULL;
        struct ocfs2_extent_list *el;
        struct buffer_head *last_eb_bh = NULL;
        u64 delete_blk = 0;

        fe = (struct ocfs2_dinode *) fe_bh->b_data;

        status = ocfs2_find_new_last_ext_blk(inode, clusters_to_del,
                                             path, &last_eb_bh);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        /*
         * Each component will be touched, so we might as well journal
         * here to avoid having to handle errors later.
         */
        status = ocfs2_journal_access_path(inode, handle, path);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        if (last_eb_bh) {
                status = ocfs2_journal_access(handle, inode, last_eb_bh,
                                              OCFS2_JOURNAL_ACCESS_WRITE);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }

                last_eb = (struct ocfs2_extent_block *) last_eb_bh->b_data;
        }

        el = &(fe->id2.i_list);

        /*
         * Lower levels depend on this never happening, but it's best
         * to check it up here before changing the tree.
         */
        if (el->l_tree_depth && el->l_recs[0].e_int_clusters == 0) {
                ocfs2_error(inode->i_sb,
                            "Inode %lu has an empty extent record, depth %u\n",
                            inode->i_ino, le16_to_cpu(el->l_tree_depth));
                status = -EROFS;
                goto bail;
        }

        spin_lock(&OCFS2_I(inode)->ip_lock);
        OCFS2_I(inode)->ip_clusters = le32_to_cpu(fe->i_clusters) -
                                      clusters_to_del;
        spin_unlock(&OCFS2_I(inode)->ip_lock);
        le32_add_cpu(&fe->i_clusters, -clusters_to_del);

        status = ocfs2_trim_tree(inode, path, handle, tc,
                                 clusters_to_del, &delete_blk);
        if (status) {
                mlog_errno(status);
                goto bail;
        }

        if (le32_to_cpu(fe->i_clusters) == 0) {
                /* trunc to zero is a special case. */
                el->l_tree_depth = 0;
                fe->i_last_eb_blk = 0;
        } else if (last_eb)
                fe->i_last_eb_blk = last_eb->h_blkno;

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

        if (last_eb) {
                /* If there will be a new last extent block, then by
                 * definition, there cannot be any leaves to the right of
                 * him. */
                last_eb->h_next_leaf_blk = 0;
                status = ocfs2_journal_dirty(handle, last_eb_bh);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
        }

        if (delete_blk) {
                status = ocfs2_truncate_log_append(osb, handle, delete_blk,
                                                   clusters_to_del);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
        }
        status = 0;
bail:

        mlog_exit(status);
        return status;
}

static int ocfs2_writeback_zero_func(handle_t *handle, struct buffer_head *bh)
{
        set_buffer_uptodate(bh);
        mark_buffer_dirty(bh);
        return 0;
}

static int ocfs2_ordered_zero_func(handle_t *handle, struct buffer_head *bh)
{
        set_buffer_uptodate(bh);
        mark_buffer_dirty(bh);
        return ocfs2_journal_dirty_data(handle, bh);
}

static void ocfs2_zero_cluster_pages(struct inode *inode, loff_t isize,
                                     struct page **pages, int numpages,
                                     u64 phys, handle_t *handle)
{
        int i, ret, partial = 0;
        void *kaddr;
        struct page *page;
        unsigned int from, to = PAGE_CACHE_SIZE;
        struct super_block *sb = inode->i_sb;

        BUG_ON(!ocfs2_sparse_alloc(OCFS2_SB(sb)));

        if (numpages == 0)
                goto out;

        from = isize & (PAGE_CACHE_SIZE - 1); /* 1st page offset */
        if (PAGE_CACHE_SHIFT > OCFS2_SB(sb)->s_clustersize_bits) {
                /*
                 * Since 'from' has been capped to a value below page
                 * size, this calculation won't be able to overflow
                 * 'to'
                 */
                to = ocfs2_align_bytes_to_clusters(sb, from);

                /*
                 * The truncate tail in this case should never contain
                 * more than one page at maximum. The loop below also
                 * assumes this.
                 */
                BUG_ON(numpages != 1);
        }

        for(i = 0; i < numpages; i++) {
                page = pages[i];

                BUG_ON(from > PAGE_CACHE_SIZE);
                BUG_ON(to > PAGE_CACHE_SIZE);

                ret = ocfs2_map_page_blocks(page, &phys, inode, from, to, 0);
                if (ret)
                        mlog_errno(ret);

                kaddr = kmap_atomic(page, KM_USER0);
                memset(kaddr + from, 0, to - from);
                kunmap_atomic(kaddr, KM_USER0);

                /*
                 * Need to set the buffers we zero'd into uptodate
                 * here if they aren't - ocfs2_map_page_blocks()
                 * might've skipped some
                 */
                if (ocfs2_should_order_data(inode)) {
                        ret = walk_page_buffers(handle,
                                                page_buffers(page),
                                                from, to, &partial,
                                                ocfs2_ordered_zero_func);
                        if (ret < 0)
                                mlog_errno(ret);
                } else {
                        ret = walk_page_buffers(handle, page_buffers(page),
                                                from, to, &partial,
                                                ocfs2_writeback_zero_func);
                        if (ret < 0)
                                mlog_errno(ret);
                }

                if (!partial)
                        SetPageUptodate(page);

                flush_dcache_page(page);

                /*
                 * Every page after the 1st one should be completely zero'd.
                 */
                from = 0;
        }
out:
        if (pages) {
                for (i = 0; i < numpages; i++) {
                        page = pages[i];
                        unlock_page(page);
                        mark_page_accessed(page);
                        page_cache_release(page);
                }
        }
}

static int ocfs2_grab_eof_pages(struct inode *inode, loff_t isize, struct page **pages,
                                int *num, u64 *phys)
{
        int i, numpages = 0, ret = 0;
        unsigned int csize = OCFS2_SB(inode->i_sb)->s_clustersize;
        unsigned int ext_flags;
        struct super_block *sb = inode->i_sb;
        struct address_space *mapping = inode->i_mapping;
        unsigned long index;
        u64 next_cluster_bytes;

        BUG_ON(!ocfs2_sparse_alloc(OCFS2_SB(sb)));

        /* Cluster boundary, so we don't need to grab any pages. */
        if ((isize & (csize - 1)) == 0)
                goto out;

        ret = ocfs2_extent_map_get_blocks(inode, isize >> sb->s_blocksize_bits,
                                          phys, NULL, &ext_flags);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /* Tail is a hole. */
        if (*phys == 0)
                goto out;

        /* Tail is marked as unwritten, we can count on write to zero
         * in that case. */
        if (ext_flags & OCFS2_EXT_UNWRITTEN)
                goto out;

        next_cluster_bytes = ocfs2_align_bytes_to_clusters(inode->i_sb, isize);
        index = isize >> PAGE_CACHE_SHIFT;
        do {
                pages[numpages] = grab_cache_page(mapping, index);
                if (!pages[numpages]) {
                        ret = -ENOMEM;
                        mlog_errno(ret);
                        goto out;
                }

                numpages++;
                index++;
        } while (index < (next_cluster_bytes >> PAGE_CACHE_SHIFT));

out:
        if (ret != 0) {
                if (pages) {
                        for (i = 0; i < numpages; i++) {
                                if (pages[i]) {
                                        unlock_page(pages[i]);
                                        page_cache_release(pages[i]);
                                }
                        }
                }
                numpages = 0;
        }

        *num = numpages;

        return ret;
}

/*
 * Zero the area past i_size but still within an allocated
 * cluster. This avoids exposing nonzero data on subsequent file
 * extends.
 *
 * We need to call this before i_size is updated on the inode because
 * otherwise block_write_full_page() will skip writeout of pages past
 * i_size. The new_i_size parameter is passed for this reason.
 */
int ocfs2_zero_tail_for_truncate(struct inode *inode, handle_t *handle,
                                 u64 new_i_size)
{
        int ret, numpages;
        loff_t endbyte;
        struct page **pages = NULL;
        u64 phys;

        /*
         * File systems which don't support sparse files zero on every
         * extend.
         */
        if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
                return 0;

        pages = kcalloc(ocfs2_pages_per_cluster(inode->i_sb),
                        sizeof(struct page *), GFP_NOFS);
        if (pages == NULL) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_grab_eof_pages(inode, new_i_size, pages, &numpages, &phys);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        if (numpages == 0)
                goto out;

        ocfs2_zero_cluster_pages(inode, new_i_size, pages, numpages, phys,
                                 handle);

        /*
         * Initiate writeout of the pages we zero'd here. We don't
         * wait on them - the truncate_inode_pages() call later will
         * do that for us.
         */
        endbyte = ocfs2_align_bytes_to_clusters(inode->i_sb, new_i_size);
        ret = do_sync_mapping_range(inode->i_mapping, new_i_size,
                                    endbyte - 1, SYNC_FILE_RANGE_WRITE);
        if (ret)
                mlog_errno(ret);

out:
        if (pages)
                kfree(pages);

        return ret;
}

/*
 * It is expected, that by the time you call this function,
 * inode->i_size and fe->i_size have been adjusted.
 *
 * WARNING: This will kfree the truncate context
 */
int ocfs2_commit_truncate(struct ocfs2_super *osb,
                          struct inode *inode,
                          struct buffer_head *fe_bh,
                          struct ocfs2_truncate_context *tc)
{
        int status, i, credits, tl_sem = 0;
        u32 clusters_to_del, new_highest_cpos, range;
        struct ocfs2_extent_list *el;
        handle_t *handle = NULL;
        struct inode *tl_inode = osb->osb_tl_inode;
        struct ocfs2_path *path = NULL;

        mlog_entry_void();

        down_write(&OCFS2_I(inode)->ip_alloc_sem);

        new_highest_cpos = ocfs2_clusters_for_bytes(osb->sb,
                                                     i_size_read(inode));

        path = ocfs2_new_inode_path(fe_bh);
        if (!path) {
                status = -ENOMEM;
                mlog_errno(status);
                goto bail;
        }

        ocfs2_extent_map_trunc(inode, new_highest_cpos);

start:
        /*
         * Check that we still have allocation to delete.
         */
        if (OCFS2_I(inode)->ip_clusters == 0) {
                status = 0;
                goto bail;
        }

        /*
         * Truncate always works against the rightmost tree branch.
         */
        status = ocfs2_find_path(inode, path, UINT_MAX);
        if (status) {
                mlog_errno(status);
                goto bail;
        }

        mlog(0, "inode->ip_clusters = %u, tree_depth = %u\n",
             OCFS2_I(inode)->ip_clusters, path->p_tree_depth);

        /*
         * By now, el will point to the extent list on the bottom most
         * portion of this tree. Only the tail record is considered in
         * each pass.
         *
         * We handle the following cases, in order:
         * - empty extent: delete the remaining branch
         * - remove the entire record
         * - remove a partial record
         * - no record needs to be removed (truncate has completed)
         */
        el = path_leaf_el(path);
        if (le16_to_cpu(el->l_next_free_rec) == 0) {
                ocfs2_error(inode->i_sb,
                            "Inode %llu has empty extent block at %llu\n",
                            (unsigned long long)OCFS2_I(inode)->ip_blkno,
                            (unsigned long long)path_leaf_bh(path)->b_blocknr);
                status = -EROFS;
                goto bail;
        }

        i = le16_to_cpu(el->l_next_free_rec) - 1;
        range = le32_to_cpu(el->l_recs[i].e_cpos) +
                ocfs2_rec_clusters(el, &el->l_recs[i]);
        if (i == 0 && ocfs2_is_empty_extent(&el->l_recs[i])) {
                clusters_to_del = 0;
        } else if (le32_to_cpu(el->l_recs[i].e_cpos) >= new_highest_cpos) {
                clusters_to_del = ocfs2_rec_clusters(el, &el->l_recs[i]);
        } else if (range > new_highest_cpos) {
                clusters_to_del = (ocfs2_rec_clusters(el, &el->l_recs[i]) +
                                   le32_to_cpu(el->l_recs[i].e_cpos)) -
                                  new_highest_cpos;
        } else {
                status = 0;
                goto bail;
        }

        mlog(0, "clusters_to_del = %u in this pass, tail blk=%llu\n",
             clusters_to_del, (unsigned long long)path_leaf_bh(path)->b_blocknr);

        BUG_ON(clusters_to_del == 0);

        mutex_lock(&tl_inode->i_mutex);
        tl_sem = 1;
        /* ocfs2_truncate_log_needs_flush guarantees us at least one
         * record is free for use. If there isn't any, we flush to get
         * an empty truncate log.  */
        if (ocfs2_truncate_log_needs_flush(osb)) {
                status = __ocfs2_flush_truncate_log(osb);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
        }

        credits = ocfs2_calc_tree_trunc_credits(osb->sb, clusters_to_del,
                                                (struct ocfs2_dinode *)fe_bh->b_data,
                                                el);
        handle = ocfs2_start_trans(osb, credits);
        if (IS_ERR(handle)) {
                status = PTR_ERR(handle);
                handle = NULL;
                mlog_errno(status);
                goto bail;
        }

        status = ocfs2_do_truncate(osb, clusters_to_del, inode, fe_bh, handle,
                                   tc, path);
        if (status < 0) {
                mlog_errno(status);
                goto bail;
        }

        mutex_unlock(&tl_inode->i_mutex);
        tl_sem = 0;

        ocfs2_commit_trans(osb, handle);
        handle = NULL;

        ocfs2_reinit_path(path, 1);

        /*
         * The check above will catch the case where we've truncated
         * away all allocation.
         */
        goto start;

bail:
        up_write(&OCFS2_I(inode)->ip_alloc_sem);

        ocfs2_schedule_truncate_log_flush(osb, 1);

        if (tl_sem)
                mutex_unlock(&tl_inode->i_mutex);

        if (handle)
                ocfs2_commit_trans(osb, handle);

        ocfs2_free_path(path);

        /* This will drop the ext_alloc cluster lock for us */
        ocfs2_free_truncate_context(tc);

        mlog_exit(status);
        return status;
}

/*
 * Expects the inode to already be locked. This will figure out which
 * inodes need to be locked and will put them on the returned truncate
 * context.
 */
int ocfs2_prepare_truncate(struct ocfs2_super *osb,
                           struct inode *inode,
                           struct buffer_head *fe_bh,
                           struct ocfs2_truncate_context **tc)
{
        int status, metadata_delete, i;
        unsigned int new_i_clusters;
        struct ocfs2_dinode *fe;
        struct ocfs2_extent_block *eb;
        struct ocfs2_extent_list *el;
        struct buffer_head *last_eb_bh = NULL;
        struct inode *ext_alloc_inode = NULL;
        struct buffer_head *ext_alloc_bh = NULL;

        mlog_entry_void();

        *tc = NULL;

        new_i_clusters = ocfs2_clusters_for_bytes(osb->sb,
                                                  i_size_read(inode));
        fe = (struct ocfs2_dinode *) fe_bh->b_data;

        mlog(0, "fe->i_clusters = %u, new_i_clusters = %u, fe->i_size ="
             "%llu\n", le32_to_cpu(fe->i_clusters), new_i_clusters,
             (unsigned long long)le64_to_cpu(fe->i_size));

        *tc = kzalloc(sizeof(struct ocfs2_truncate_context), GFP_KERNEL);
        if (!(*tc)) {
                status = -ENOMEM;
                mlog_errno(status);
                goto bail;
        }

        metadata_delete = 0;
        if (fe->id2.i_list.l_tree_depth) {
                /* If we have a tree, then the truncate may result in
                 * metadata deletes. Figure this out from the
                 * rightmost leaf block.*/
                status = ocfs2_read_block(osb, le64_to_cpu(fe->i_last_eb_blk),
                                          &last_eb_bh, OCFS2_BH_CACHED, inode);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
                eb = (struct ocfs2_extent_block *) last_eb_bh->b_data;
                if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
                        OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);

                        brelse(last_eb_bh);
                        status = -EIO;
                        goto bail;
                }
                el = &(eb->h_list);

                i = 0;
                if (ocfs2_is_empty_extent(&el->l_recs[0]))
                        i = 1;
                /*
                 * XXX: Should we check that next_free_rec contains
                 * the extent?
                 */
                if (le32_to_cpu(el->l_recs[i].e_cpos) >= new_i_clusters)
                        metadata_delete = 1;
        }

        (*tc)->tc_last_eb_bh = last_eb_bh;

        if (metadata_delete) {
                mlog(0, "Will have to delete metadata for this trunc. "
                     "locking allocator.\n");
                ext_alloc_inode = ocfs2_get_system_file_inode(osb, EXTENT_ALLOC_SYSTEM_INODE, 0);
                if (!ext_alloc_inode) {
                        status = -ENOMEM;
                        mlog_errno(status);
                        goto bail;
                }

                mutex_lock(&ext_alloc_inode->i_mutex);
                (*tc)->tc_ext_alloc_inode = ext_alloc_inode;

                status = ocfs2_meta_lock(ext_alloc_inode, &ext_alloc_bh, 1);
                if (status < 0) {
                        mlog_errno(status);
                        goto bail;
                }
                (*tc)->tc_ext_alloc_bh = ext_alloc_bh;
                (*tc)->tc_ext_alloc_locked = 1;
        }

        status = 0;
bail:
        if (status < 0) {
                if (*tc)
                        ocfs2_free_truncate_context(*tc);
                *tc = NULL;
        }
        mlog_exit_void();
        return status;
}

static void ocfs2_free_truncate_context(struct ocfs2_truncate_context *tc)
{
        if (tc->tc_ext_alloc_inode) {
                if (tc->tc_ext_alloc_locked)
                        ocfs2_meta_unlock(tc->tc_ext_alloc_inode, 1);

                mutex_unlock(&tc->tc_ext_alloc_inode->i_mutex);
                iput(tc->tc_ext_alloc_inode);
        }

        if (tc->tc_ext_alloc_bh)
                brelse(tc->tc_ext_alloc_bh);

        if (tc->tc_last_eb_bh)
                brelse(tc->tc_last_eb_bh);

        kfree(tc);
}