ocfs2: CoW refcount tree improvement.

[safe/jmp/linux-2.6] / fs / ocfs2 / refcounttree.c

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

#include <linux/sort.h>
#define MLOG_MASK_PREFIX ML_REFCOUNT
#include <cluster/masklog.h>
#include "ocfs2.h"
#include "inode.h"
#include "alloc.h"
#include "suballoc.h"
#include "journal.h"
#include "uptodate.h"
#include "super.h"
#include "buffer_head_io.h"
#include "blockcheck.h"
#include "refcounttree.h"
#include "sysfile.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "aops.h"

#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/swap.h>

struct ocfs2_cow_context {
        struct inode *inode;
        u32 cow_start;
        u32 cow_len;
        struct ocfs2_extent_tree di_et;
        struct ocfs2_caching_info *ref_ci;
        struct buffer_head *ref_root_bh;
        struct ocfs2_alloc_context *meta_ac;
        struct ocfs2_alloc_context *data_ac;
        struct ocfs2_cached_dealloc_ctxt dealloc;
};

static inline struct ocfs2_refcount_tree *
cache_info_to_refcount(struct ocfs2_caching_info *ci)
{
        return container_of(ci, struct ocfs2_refcount_tree, rf_ci);
}

static int ocfs2_validate_refcount_block(struct super_block *sb,
                                         struct buffer_head *bh)
{
        int rc;
        struct ocfs2_refcount_block *rb =
                (struct ocfs2_refcount_block *)bh->b_data;

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

        BUG_ON(!buffer_uptodate(bh));

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


        if (!OCFS2_IS_VALID_REFCOUNT_BLOCK(rb)) {
                ocfs2_error(sb,
                            "Refcount block #%llu has bad signature %.*s",
                            (unsigned long long)bh->b_blocknr, 7,
                            rb->rf_signature);
                return -EINVAL;
        }

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

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

        return 0;
}

static int ocfs2_read_refcount_block(struct ocfs2_caching_info *ci,
                                     u64 rb_blkno,
                                     struct buffer_head **bh)
{
        int rc;
        struct buffer_head *tmp = *bh;

        rc = ocfs2_read_block(ci, rb_blkno, &tmp,
                              ocfs2_validate_refcount_block);

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

        return rc;
}

static u64 ocfs2_refcount_cache_owner(struct ocfs2_caching_info *ci)
{
        struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

        return rf->rf_blkno;
}

static struct super_block *
ocfs2_refcount_cache_get_super(struct ocfs2_caching_info *ci)
{
        struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

        return rf->rf_sb;
}

static void ocfs2_refcount_cache_lock(struct ocfs2_caching_info *ci)
{
        struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

        spin_lock(&rf->rf_lock);
}

static void ocfs2_refcount_cache_unlock(struct ocfs2_caching_info *ci)
{
        struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

        spin_unlock(&rf->rf_lock);
}

static void ocfs2_refcount_cache_io_lock(struct ocfs2_caching_info *ci)
{
        struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

        mutex_lock(&rf->rf_io_mutex);
}

static void ocfs2_refcount_cache_io_unlock(struct ocfs2_caching_info *ci)
{
        struct ocfs2_refcount_tree *rf = cache_info_to_refcount(ci);

        mutex_unlock(&rf->rf_io_mutex);
}

static const struct ocfs2_caching_operations ocfs2_refcount_caching_ops = {
        .co_owner               = ocfs2_refcount_cache_owner,
        .co_get_super           = ocfs2_refcount_cache_get_super,
        .co_cache_lock          = ocfs2_refcount_cache_lock,
        .co_cache_unlock        = ocfs2_refcount_cache_unlock,
        .co_io_lock             = ocfs2_refcount_cache_io_lock,
        .co_io_unlock           = ocfs2_refcount_cache_io_unlock,
};

static struct ocfs2_refcount_tree *
ocfs2_find_refcount_tree(struct ocfs2_super *osb, u64 blkno)
{
        struct rb_node *n = osb->osb_rf_lock_tree.rb_node;
        struct ocfs2_refcount_tree *tree = NULL;

        while (n) {
                tree = rb_entry(n, struct ocfs2_refcount_tree, rf_node);

                if (blkno < tree->rf_blkno)
                        n = n->rb_left;
                else if (blkno > tree->rf_blkno)
                        n = n->rb_right;
                else
                        return tree;
        }

        return NULL;
}

/* osb_lock is already locked. */
static void ocfs2_insert_refcount_tree(struct ocfs2_super *osb,
                                       struct ocfs2_refcount_tree *new)
{
        u64 rf_blkno = new->rf_blkno;
        struct rb_node *parent = NULL;
        struct rb_node **p = &osb->osb_rf_lock_tree.rb_node;
        struct ocfs2_refcount_tree *tmp;

        while (*p) {
                parent = *p;

                tmp = rb_entry(parent, struct ocfs2_refcount_tree,
                               rf_node);

                if (rf_blkno < tmp->rf_blkno)
                        p = &(*p)->rb_left;
                else if (rf_blkno > tmp->rf_blkno)
                        p = &(*p)->rb_right;
                else {
                        /* This should never happen! */
                        mlog(ML_ERROR, "Duplicate refcount block %llu found!\n",
                             (unsigned long long)rf_blkno);
                        BUG();
                }
        }

        rb_link_node(&new->rf_node, parent, p);
        rb_insert_color(&new->rf_node, &osb->osb_rf_lock_tree);
}

static void ocfs2_free_refcount_tree(struct ocfs2_refcount_tree *tree)
{
        ocfs2_metadata_cache_exit(&tree->rf_ci);
        ocfs2_simple_drop_lockres(OCFS2_SB(tree->rf_sb), &tree->rf_lockres);
        ocfs2_lock_res_free(&tree->rf_lockres);
        kfree(tree);
}

static inline void
ocfs2_erase_refcount_tree_from_list_no_lock(struct ocfs2_super *osb,
                                        struct ocfs2_refcount_tree *tree)
{
        rb_erase(&tree->rf_node, &osb->osb_rf_lock_tree);
        if (osb->osb_ref_tree_lru && osb->osb_ref_tree_lru == tree)
                osb->osb_ref_tree_lru = NULL;
}

static void ocfs2_erase_refcount_tree_from_list(struct ocfs2_super *osb,
                                        struct ocfs2_refcount_tree *tree)
{
        spin_lock(&osb->osb_lock);
        ocfs2_erase_refcount_tree_from_list_no_lock(osb, tree);
        spin_unlock(&osb->osb_lock);
}

void ocfs2_kref_remove_refcount_tree(struct kref *kref)
{
        struct ocfs2_refcount_tree *tree =
                container_of(kref, struct ocfs2_refcount_tree, rf_getcnt);

        ocfs2_free_refcount_tree(tree);
}

static inline void
ocfs2_refcount_tree_get(struct ocfs2_refcount_tree *tree)
{
        kref_get(&tree->rf_getcnt);
}

static inline void
ocfs2_refcount_tree_put(struct ocfs2_refcount_tree *tree)
{
        kref_put(&tree->rf_getcnt, ocfs2_kref_remove_refcount_tree);
}

static inline void ocfs2_init_refcount_tree_ci(struct ocfs2_refcount_tree *new,
                                               struct super_block *sb)
{
        ocfs2_metadata_cache_init(&new->rf_ci, &ocfs2_refcount_caching_ops);
        mutex_init(&new->rf_io_mutex);
        new->rf_sb = sb;
        spin_lock_init(&new->rf_lock);
}

static inline void ocfs2_init_refcount_tree_lock(struct ocfs2_super *osb,
                                        struct ocfs2_refcount_tree *new,
                                        u64 rf_blkno, u32 generation)
{
        init_rwsem(&new->rf_sem);
        ocfs2_refcount_lock_res_init(&new->rf_lockres, osb,
                                     rf_blkno, generation);
}

static struct ocfs2_refcount_tree*
ocfs2_allocate_refcount_tree(struct ocfs2_super *osb, u64 rf_blkno)
{
        struct ocfs2_refcount_tree *new;

        new = kzalloc(sizeof(struct ocfs2_refcount_tree), GFP_NOFS);
        if (!new)
                return NULL;

        new->rf_blkno = rf_blkno;
        kref_init(&new->rf_getcnt);
        ocfs2_init_refcount_tree_ci(new, osb->sb);

        return new;
}

static int ocfs2_get_refcount_tree(struct ocfs2_super *osb, u64 rf_blkno,
                                   struct ocfs2_refcount_tree **ret_tree)
{
        int ret = 0;
        struct ocfs2_refcount_tree *tree, *new = NULL;
        struct buffer_head *ref_root_bh = NULL;
        struct ocfs2_refcount_block *ref_rb;

        spin_lock(&osb->osb_lock);
        if (osb->osb_ref_tree_lru &&
            osb->osb_ref_tree_lru->rf_blkno == rf_blkno)
                tree = osb->osb_ref_tree_lru;
        else
                tree = ocfs2_find_refcount_tree(osb, rf_blkno);
        if (tree)
                goto out;

        spin_unlock(&osb->osb_lock);

        new = ocfs2_allocate_refcount_tree(osb, rf_blkno);
        if (!new) {
                ret = -ENOMEM;
                mlog_errno(ret);
                return ret;
        }
        /*
         * We need the generation to create the refcount tree lock and since
         * it isn't changed during the tree modification, we are safe here to
         * read without protection.
         * We also have to purge the cache after we create the lock since the
         * refcount block may have the stale data. It can only be trusted when
         * we hold the refcount lock.
         */
        ret = ocfs2_read_refcount_block(&new->rf_ci, rf_blkno, &ref_root_bh);
        if (ret) {
                mlog_errno(ret);
                ocfs2_metadata_cache_exit(&new->rf_ci);
                kfree(new);
                return ret;
        }

        ref_rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
        new->rf_generation = le32_to_cpu(ref_rb->rf_generation);
        ocfs2_init_refcount_tree_lock(osb, new, rf_blkno,
                                      new->rf_generation);
        ocfs2_metadata_cache_purge(&new->rf_ci);

        spin_lock(&osb->osb_lock);
        tree = ocfs2_find_refcount_tree(osb, rf_blkno);
        if (tree)
                goto out;

        ocfs2_insert_refcount_tree(osb, new);

        tree = new;
        new = NULL;

out:
        *ret_tree = tree;

        osb->osb_ref_tree_lru = tree;

        spin_unlock(&osb->osb_lock);

        if (new)
                ocfs2_free_refcount_tree(new);

        brelse(ref_root_bh);
        return ret;
}

static int ocfs2_get_refcount_block(struct inode *inode, u64 *ref_blkno)
{
        int ret;
        struct buffer_head *di_bh = NULL;
        struct ocfs2_dinode *di;

        ret = ocfs2_read_inode_block(inode, &di_bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        BUG_ON(!(OCFS2_I(inode)->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));

        di = (struct ocfs2_dinode *)di_bh->b_data;
        *ref_blkno = le64_to_cpu(di->i_refcount_loc);
        brelse(di_bh);
out:
        return ret;
}

static int __ocfs2_lock_refcount_tree(struct ocfs2_super *osb,
                                      struct ocfs2_refcount_tree *tree, int rw)
{
        int ret;

        ret = ocfs2_refcount_lock(tree, rw);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        if (rw)
                down_write(&tree->rf_sem);
        else
                down_read(&tree->rf_sem);

out:
        return ret;
}

/*
 * Lock the refcount tree pointed by ref_blkno and return the tree.
 * In most case, we lock the tree and read the refcount block.
 * So read it here if the caller really needs it.
 *
 * If the tree has been re-created by other node, it will free the
 * old one and re-create it.
 */
int ocfs2_lock_refcount_tree(struct ocfs2_super *osb,
                             u64 ref_blkno, int rw,
                             struct ocfs2_refcount_tree **ret_tree,
                             struct buffer_head **ref_bh)
{
        int ret, delete_tree = 0;
        struct ocfs2_refcount_tree *tree = NULL;
        struct buffer_head *ref_root_bh = NULL;
        struct ocfs2_refcount_block *rb;

again:
        ret = ocfs2_get_refcount_tree(osb, ref_blkno, &tree);
        if (ret) {
                mlog_errno(ret);
                return ret;
        }

        ocfs2_refcount_tree_get(tree);

        ret = __ocfs2_lock_refcount_tree(osb, tree, rw);
        if (ret) {
                mlog_errno(ret);
                ocfs2_refcount_tree_put(tree);
                goto out;
        }

        ret = ocfs2_read_refcount_block(&tree->rf_ci, tree->rf_blkno,
                                        &ref_root_bh);
        if (ret) {
                mlog_errno(ret);
                ocfs2_unlock_refcount_tree(osb, tree, rw);
                ocfs2_refcount_tree_put(tree);
                goto out;
        }

        rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
        /*
         * If the refcount block has been freed and re-created, we may need
         * to recreate the refcount tree also.
         *
         * Here we just remove the tree from the rb-tree, and the last
         * kref holder will unlock and delete this refcount_tree.
         * Then we goto "again" and ocfs2_get_refcount_tree will create
         * the new refcount tree for us.
         */
        if (tree->rf_generation != le32_to_cpu(rb->rf_generation)) {
                if (!tree->rf_removed) {
                        ocfs2_erase_refcount_tree_from_list(osb, tree);
                        tree->rf_removed = 1;
                        delete_tree = 1;
                }

                ocfs2_unlock_refcount_tree(osb, tree, rw);
                /*
                 * We get an extra reference when we create the refcount
                 * tree, so another put will destroy it.
                 */
                if (delete_tree)
                        ocfs2_refcount_tree_put(tree);
                brelse(ref_root_bh);
                ref_root_bh = NULL;
                goto again;
        }

        *ret_tree = tree;
        if (ref_bh) {
                *ref_bh = ref_root_bh;
                ref_root_bh = NULL;
        }
out:
        brelse(ref_root_bh);
        return ret;
}

int ocfs2_lock_refcount_tree_by_inode(struct inode *inode, int rw,
                                      struct ocfs2_refcount_tree **ret_tree,
                                      struct buffer_head **ref_bh)
{
        int ret;
        u64 ref_blkno;

        ret = ocfs2_get_refcount_block(inode, &ref_blkno);
        if (ret) {
                mlog_errno(ret);
                return ret;
        }

        return ocfs2_lock_refcount_tree(OCFS2_SB(inode->i_sb), ref_blkno,
                                        rw, ret_tree, ref_bh);
}

void ocfs2_unlock_refcount_tree(struct ocfs2_super *osb,
                                struct ocfs2_refcount_tree *tree, int rw)
{
        if (rw)
                up_write(&tree->rf_sem);
        else
                up_read(&tree->rf_sem);

        ocfs2_refcount_unlock(tree, rw);
        ocfs2_refcount_tree_put(tree);
}

void ocfs2_purge_refcount_trees(struct ocfs2_super *osb)
{
        struct rb_node *node;
        struct ocfs2_refcount_tree *tree;
        struct rb_root *root = &osb->osb_rf_lock_tree;

        while ((node = rb_last(root)) != NULL) {
                tree = rb_entry(node, struct ocfs2_refcount_tree, rf_node);

                mlog(0, "Purge tree %llu\n",
                     (unsigned long long) tree->rf_blkno);

                rb_erase(&tree->rf_node, root);
                ocfs2_free_refcount_tree(tree);
        }
}

/*
 * Create a refcount tree for an inode.
 * We take for granted that the inode is already locked.
 */
static int ocfs2_create_refcount_tree(struct inode *inode,
                                      struct buffer_head *di_bh)
{
        int ret;
        handle_t *handle = NULL;
        struct ocfs2_alloc_context *meta_ac = NULL;
        struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
        struct buffer_head *new_bh = NULL;
        struct ocfs2_refcount_block *rb;
        struct ocfs2_refcount_tree *new_tree = NULL, *tree = NULL;
        u16 suballoc_bit_start;
        u32 num_got;
        u64 first_blkno;

        BUG_ON(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL);

        mlog(0, "create tree for inode %lu\n", inode->i_ino);

        ret = ocfs2_reserve_new_metadata_blocks(osb, 1, &meta_ac);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        handle = ocfs2_start_trans(osb, OCFS2_REFCOUNT_TREE_CREATE_CREDITS);
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out_commit;
        }

        ret = ocfs2_claim_metadata(osb, handle, meta_ac, 1,
                                   &suballoc_bit_start, &num_got,
                                   &first_blkno);
        if (ret) {
                mlog_errno(ret);
                goto out_commit;
        }

        new_tree = ocfs2_allocate_refcount_tree(osb, first_blkno);
        if (!new_tree) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out_commit;
        }

        new_bh = sb_getblk(inode->i_sb, first_blkno);
        ocfs2_set_new_buffer_uptodate(&new_tree->rf_ci, new_bh);

        ret = ocfs2_journal_access_rb(handle, &new_tree->rf_ci, new_bh,
                                      OCFS2_JOURNAL_ACCESS_CREATE);
        if (ret) {
                mlog_errno(ret);
                goto out_commit;
        }

        /* Initialize ocfs2_refcount_block. */
        rb = (struct ocfs2_refcount_block *)new_bh->b_data;
        memset(rb, 0, inode->i_sb->s_blocksize);
        strcpy((void *)rb, OCFS2_REFCOUNT_BLOCK_SIGNATURE);
        rb->rf_suballoc_slot = cpu_to_le16(osb->slot_num);
        rb->rf_suballoc_bit = cpu_to_le16(suballoc_bit_start);
        rb->rf_fs_generation = cpu_to_le32(osb->fs_generation);
        rb->rf_blkno = cpu_to_le64(first_blkno);
        rb->rf_count = cpu_to_le32(1);
        rb->rf_records.rl_count =
                        cpu_to_le16(ocfs2_refcount_recs_per_rb(osb->sb));
        spin_lock(&osb->osb_lock);
        rb->rf_generation = osb->s_next_generation++;
        spin_unlock(&osb->osb_lock);

        ocfs2_journal_dirty(handle, new_bh);

        spin_lock(&oi->ip_lock);
        oi->ip_dyn_features |= OCFS2_HAS_REFCOUNT_FL;
        di->i_dyn_features = cpu_to_le16(oi->ip_dyn_features);
        di->i_refcount_loc = cpu_to_le64(first_blkno);
        spin_unlock(&oi->ip_lock);

        mlog(0, "created tree for inode %lu, refblock %llu\n",
             inode->i_ino, (unsigned long long)first_blkno);

        ocfs2_journal_dirty(handle, di_bh);

        /*
         * We have to init the tree lock here since it will use
         * the generation number to create it.
         */
        new_tree->rf_generation = le32_to_cpu(rb->rf_generation);
        ocfs2_init_refcount_tree_lock(osb, new_tree, first_blkno,
                                      new_tree->rf_generation);

        spin_lock(&osb->osb_lock);
        tree = ocfs2_find_refcount_tree(osb, first_blkno);

        /*
         * We've just created a new refcount tree in this block.  If
         * we found a refcount tree on the ocfs2_super, it must be
         * one we just deleted.  We free the old tree before
         * inserting the new tree.
         */
        BUG_ON(tree && tree->rf_generation == new_tree->rf_generation);
        if (tree)
                ocfs2_erase_refcount_tree_from_list_no_lock(osb, tree);
        ocfs2_insert_refcount_tree(osb, new_tree);
        spin_unlock(&osb->osb_lock);
        new_tree = NULL;
        if (tree)
                ocfs2_refcount_tree_put(tree);

out_commit:
        ocfs2_commit_trans(osb, handle);

out:
        if (new_tree) {
                ocfs2_metadata_cache_exit(&new_tree->rf_ci);
                kfree(new_tree);
        }

        brelse(new_bh);
        if (meta_ac)
                ocfs2_free_alloc_context(meta_ac);

        return ret;
}

static int ocfs2_set_refcount_tree(struct inode *inode,
                                   struct buffer_head *di_bh,
                                   u64 refcount_loc)
{
        int ret;
        handle_t *handle = NULL;
        struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
        struct buffer_head *ref_root_bh = NULL;
        struct ocfs2_refcount_block *rb;
        struct ocfs2_refcount_tree *ref_tree;

        BUG_ON(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL);

        ret = ocfs2_lock_refcount_tree(osb, refcount_loc, 1,
                                       &ref_tree, &ref_root_bh);
        if (ret) {
                mlog_errno(ret);
                return ret;
        }

        handle = ocfs2_start_trans(osb, OCFS2_REFCOUNT_TREE_SET_CREDITS);
        if (IS_ERR(handle)) {
                ret = PTR_ERR(handle);
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out_commit;
        }

        ret = ocfs2_journal_access_rb(handle, &ref_tree->rf_ci, ref_root_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out_commit;
        }

        rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
        le32_add_cpu(&rb->rf_count, 1);

        ocfs2_journal_dirty(handle, ref_root_bh);

        spin_lock(&oi->ip_lock);
        oi->ip_dyn_features |= OCFS2_HAS_REFCOUNT_FL;
        di->i_dyn_features = cpu_to_le16(oi->ip_dyn_features);
        di->i_refcount_loc = cpu_to_le64(refcount_loc);
        spin_unlock(&oi->ip_lock);
        ocfs2_journal_dirty(handle, di_bh);

out_commit:
        ocfs2_commit_trans(osb, handle);
out:
        ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
        brelse(ref_root_bh);

        return ret;
}

int ocfs2_remove_refcount_tree(struct inode *inode, struct buffer_head *di_bh)
{
        int ret, delete_tree = 0;
        handle_t *handle = NULL;
        struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
        struct ocfs2_refcount_block *rb;
        struct inode *alloc_inode = NULL;
        struct buffer_head *alloc_bh = NULL;
        struct buffer_head *blk_bh = NULL;
        struct ocfs2_refcount_tree *ref_tree;
        int credits = OCFS2_REFCOUNT_TREE_REMOVE_CREDITS;
        u64 blk = 0, bg_blkno = 0, ref_blkno = le64_to_cpu(di->i_refcount_loc);
        u16 bit = 0;

        if (!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL))
                return 0;

        BUG_ON(!ref_blkno);
        ret = ocfs2_lock_refcount_tree(osb, ref_blkno, 1, &ref_tree, &blk_bh);
        if (ret) {
                mlog_errno(ret);
                return ret;
        }

        rb = (struct ocfs2_refcount_block *)blk_bh->b_data;

        /*
         * If we are the last user, we need to free the block.
         * So lock the allocator ahead.
         */
        if (le32_to_cpu(rb->rf_count) == 1) {
                blk = le64_to_cpu(rb->rf_blkno);
                bit = le16_to_cpu(rb->rf_suballoc_bit);
                bg_blkno = ocfs2_which_suballoc_group(blk, bit);

                alloc_inode = ocfs2_get_system_file_inode(osb,
                                        EXTENT_ALLOC_SYSTEM_INODE,
                                        le16_to_cpu(rb->rf_suballoc_slot));
                if (!alloc_inode) {
                        ret = -ENOMEM;
                        mlog_errno(ret);
                        goto out;
                }
                mutex_lock(&alloc_inode->i_mutex);

                ret = ocfs2_inode_lock(alloc_inode, &alloc_bh, 1);
                if (ret) {
                        mlog_errno(ret);
                        goto out_mutex;
                }

                credits += OCFS2_SUBALLOC_FREE;
        }

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

        ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out_commit;
        }

        ret = ocfs2_journal_access_rb(handle, &ref_tree->rf_ci, blk_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out_commit;
        }

        spin_lock(&oi->ip_lock);
        oi->ip_dyn_features &= ~OCFS2_HAS_REFCOUNT_FL;
        di->i_dyn_features = cpu_to_le16(oi->ip_dyn_features);
        di->i_refcount_loc = 0;
        spin_unlock(&oi->ip_lock);
        ocfs2_journal_dirty(handle, di_bh);

        le32_add_cpu(&rb->rf_count , -1);
        ocfs2_journal_dirty(handle, blk_bh);

        if (!rb->rf_count) {
                delete_tree = 1;
                ocfs2_erase_refcount_tree_from_list(osb, ref_tree);
                ret = ocfs2_free_suballoc_bits(handle, alloc_inode,
                                               alloc_bh, bit, bg_blkno, 1);
                if (ret)
                        mlog_errno(ret);
        }

out_commit:
        ocfs2_commit_trans(osb, handle);
out_unlock:
        if (alloc_inode) {
                ocfs2_inode_unlock(alloc_inode, 1);
                brelse(alloc_bh);
        }
out_mutex:
        if (alloc_inode) {
                mutex_unlock(&alloc_inode->i_mutex);
                iput(alloc_inode);
        }
out:
        ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
        if (delete_tree)
                ocfs2_refcount_tree_put(ref_tree);
        brelse(blk_bh);

        return ret;
}

static void ocfs2_find_refcount_rec_in_rl(struct ocfs2_caching_info *ci,
                                          struct buffer_head *ref_leaf_bh,
                                          u64 cpos, unsigned int len,
                                          struct ocfs2_refcount_rec *ret_rec,
                                          int *index)
{
        int i = 0;
        struct ocfs2_refcount_block *rb =
                (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        struct ocfs2_refcount_rec *rec = NULL;

        for (; i < le16_to_cpu(rb->rf_records.rl_used); i++) {
                rec = &rb->rf_records.rl_recs[i];

                if (le64_to_cpu(rec->r_cpos) +
                    le32_to_cpu(rec->r_clusters) <= cpos)
                        continue;
                else if (le64_to_cpu(rec->r_cpos) > cpos)
                        break;

                /* ok, cpos fail in this rec. Just return. */
                if (ret_rec)
                        *ret_rec = *rec;
                goto out;
        }

        if (ret_rec) {
                /* We meet with a hole here, so fake the rec. */
                ret_rec->r_cpos = cpu_to_le64(cpos);
                ret_rec->r_refcount = 0;
                if (i < le16_to_cpu(rb->rf_records.rl_used) &&
                    le64_to_cpu(rec->r_cpos) < cpos + len)
                        ret_rec->r_clusters =
                                cpu_to_le32(le64_to_cpu(rec->r_cpos) - cpos);
                else
                        ret_rec->r_clusters = cpu_to_le32(len);
        }

out:
        *index = i;
}

/*
 * Given a cpos and len, try to find the refcount record which contains cpos.
 * 1. If cpos can be found in one refcount record, return the record.
 * 2. If cpos can't be found, return a fake record which start from cpos
 *    and end at a small value between cpos+len and start of the next record.
 *    This fake record has r_refcount = 0.
 */
static int ocfs2_get_refcount_rec(struct ocfs2_caching_info *ci,
                                  struct buffer_head *ref_root_bh,
                                  u64 cpos, unsigned int len,
                                  struct ocfs2_refcount_rec *ret_rec,
                                  int *index,
                                  struct buffer_head **ret_bh)
{
        int ret = 0, i, found;
        u32 low_cpos;
        struct ocfs2_extent_list *el;
        struct ocfs2_extent_rec *tmp, *rec = NULL;
        struct ocfs2_extent_block *eb;
        struct buffer_head *eb_bh = NULL, *ref_leaf_bh = NULL;
        struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
        struct ocfs2_refcount_block *rb =
                        (struct ocfs2_refcount_block *)ref_root_bh->b_data;

        if (!(le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL)) {
                ocfs2_find_refcount_rec_in_rl(ci, ref_root_bh, cpos, len,
                                              ret_rec, index);
                *ret_bh = ref_root_bh;
                get_bh(ref_root_bh);
                return 0;
        }

        el = &rb->rf_list;
        low_cpos = cpos & OCFS2_32BIT_POS_MASK;

        if (el->l_tree_depth) {
                ret = ocfs2_find_leaf(ci, el, low_cpos, &eb_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

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

                if (el->l_tree_depth) {
                        ocfs2_error(sb,
                        "refcount tree %llu has non zero tree "
                        "depth in leaf btree tree block %llu\n",
                        (unsigned long long)ocfs2_metadata_cache_owner(ci),
                        (unsigned long long)eb_bh->b_blocknr);
                        ret = -EROFS;
                        goto out;
                }
        }

        found = 0;
        for (i = le16_to_cpu(el->l_next_free_rec) - 1; i >= 0; i--) {
                rec = &el->l_recs[i];

                if (le32_to_cpu(rec->e_cpos) <= low_cpos) {
                        found = 1;
                        break;
                }
        }

        /* adjust len when we have ocfs2_extent_rec after it. */
        if (found && i < le16_to_cpu(el->l_next_free_rec) - 1) {
                tmp = &el->l_recs[i+1];

                if (le32_to_cpu(tmp->e_cpos) < cpos + len)
                        len = le32_to_cpu(tmp->e_cpos) - cpos;
        }

        ret = ocfs2_read_refcount_block(ci, le64_to_cpu(rec->e_blkno),
                                        &ref_leaf_bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ocfs2_find_refcount_rec_in_rl(ci, ref_leaf_bh, cpos, len,
                                      ret_rec, index);
        *ret_bh = ref_leaf_bh;
out:
        brelse(eb_bh);
        return ret;
}

enum ocfs2_ref_rec_contig {
        REF_CONTIG_NONE = 0,
        REF_CONTIG_LEFT,
        REF_CONTIG_RIGHT,
        REF_CONTIG_LEFTRIGHT,
};

static enum ocfs2_ref_rec_contig
        ocfs2_refcount_rec_adjacent(struct ocfs2_refcount_block *rb,
                                    int index)
{
        if ((rb->rf_records.rl_recs[index].r_refcount ==
            rb->rf_records.rl_recs[index + 1].r_refcount) &&
            (le64_to_cpu(rb->rf_records.rl_recs[index].r_cpos) +
            le32_to_cpu(rb->rf_records.rl_recs[index].r_clusters) ==
            le64_to_cpu(rb->rf_records.rl_recs[index + 1].r_cpos)))
                return REF_CONTIG_RIGHT;

        return REF_CONTIG_NONE;
}

static enum ocfs2_ref_rec_contig
        ocfs2_refcount_rec_contig(struct ocfs2_refcount_block *rb,
                                  int index)
{
        enum ocfs2_ref_rec_contig ret = REF_CONTIG_NONE;

        if (index < le16_to_cpu(rb->rf_records.rl_used) - 1)
                ret = ocfs2_refcount_rec_adjacent(rb, index);

        if (index > 0) {
                enum ocfs2_ref_rec_contig tmp;

                tmp = ocfs2_refcount_rec_adjacent(rb, index - 1);

                if (tmp == REF_CONTIG_RIGHT) {
                        if (ret == REF_CONTIG_RIGHT)
                                ret = REF_CONTIG_LEFTRIGHT;
                        else
                                ret = REF_CONTIG_LEFT;
                }
        }

        return ret;
}

static void ocfs2_rotate_refcount_rec_left(struct ocfs2_refcount_block *rb,
                                           int index)
{
        BUG_ON(rb->rf_records.rl_recs[index].r_refcount !=
               rb->rf_records.rl_recs[index+1].r_refcount);

        le32_add_cpu(&rb->rf_records.rl_recs[index].r_clusters,
                     le32_to_cpu(rb->rf_records.rl_recs[index+1].r_clusters));

        if (index < le16_to_cpu(rb->rf_records.rl_used) - 2)
                memmove(&rb->rf_records.rl_recs[index + 1],
                        &rb->rf_records.rl_recs[index + 2],
                        sizeof(struct ocfs2_refcount_rec) *
                        (le16_to_cpu(rb->rf_records.rl_used) - index - 2));

        memset(&rb->rf_records.rl_recs[le16_to_cpu(rb->rf_records.rl_used) - 1],
               0, sizeof(struct ocfs2_refcount_rec));
        le16_add_cpu(&rb->rf_records.rl_used, -1);
}

/*
 * Merge the refcount rec if we are contiguous with the adjacent recs.
 */
static void ocfs2_refcount_rec_merge(struct ocfs2_refcount_block *rb,
                                     int index)
{
        enum ocfs2_ref_rec_contig contig =
                                ocfs2_refcount_rec_contig(rb, index);

        if (contig == REF_CONTIG_NONE)
                return;

        if (contig == REF_CONTIG_LEFT || contig == REF_CONTIG_LEFTRIGHT) {
                BUG_ON(index == 0);
                index--;
        }

        ocfs2_rotate_refcount_rec_left(rb, index);

        if (contig == REF_CONTIG_LEFTRIGHT)
                ocfs2_rotate_refcount_rec_left(rb, index);
}

/*
 * Change the refcount indexed by "index" in ref_bh.
 * If refcount reaches 0, remove it.
 */
static int ocfs2_change_refcount_rec(handle_t *handle,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *ref_leaf_bh,
                                     int index, int change)
{
        int ret;
        struct ocfs2_refcount_block *rb =
                        (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        struct ocfs2_refcount_list *rl = &rb->rf_records;
        struct ocfs2_refcount_rec *rec = &rl->rl_recs[index];

        ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        mlog(0, "change index %d, old count %u, change %d\n", index,
             le32_to_cpu(rec->r_refcount), change);
        le32_add_cpu(&rec->r_refcount, change);

        if (!rec->r_refcount) {
                if (index != le16_to_cpu(rl->rl_used) - 1) {
                        memmove(rec, rec + 1,
                                (le16_to_cpu(rl->rl_used) - index - 1) *
                                sizeof(struct ocfs2_refcount_rec));
                        memset(&rl->rl_recs[le16_to_cpu(rl->rl_used) - 1],
                               0, sizeof(struct ocfs2_refcount_rec));
                }

                le16_add_cpu(&rl->rl_used, -1);
        } else
                ocfs2_refcount_rec_merge(rb, index);

        ret = ocfs2_journal_dirty(handle, ref_leaf_bh);
        if (ret)
                mlog_errno(ret);
out:
        return ret;
}

static int ocfs2_expand_inline_ref_root(handle_t *handle,
                                        struct ocfs2_caching_info *ci,
                                        struct buffer_head *ref_root_bh,
                                        struct buffer_head **ref_leaf_bh,
                                        struct ocfs2_alloc_context *meta_ac)
{
        int ret;
        u16 suballoc_bit_start;
        u32 num_got;
        u64 blkno;
        struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
        struct buffer_head *new_bh = NULL;
        struct ocfs2_refcount_block *new_rb;
        struct ocfs2_refcount_block *root_rb =
                        (struct ocfs2_refcount_block *)ref_root_bh->b_data;

        ret = ocfs2_journal_access_rb(handle, ci, ref_root_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_claim_metadata(OCFS2_SB(sb), handle, meta_ac, 1,
                                   &suballoc_bit_start, &num_got,
                                   &blkno);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        new_bh = sb_getblk(sb, blkno);
        if (new_bh == NULL) {
                ret = -EIO;
                mlog_errno(ret);
                goto out;
        }
        ocfs2_set_new_buffer_uptodate(ci, new_bh);

        ret = ocfs2_journal_access_rb(handle, ci, new_bh,
                                      OCFS2_JOURNAL_ACCESS_CREATE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /*
         * Initialize ocfs2_refcount_block.
         * It should contain the same information as the old root.
         * so just memcpy it and change the corresponding field.
         */
        memcpy(new_bh->b_data, ref_root_bh->b_data, sb->s_blocksize);

        new_rb = (struct ocfs2_refcount_block *)new_bh->b_data;
        new_rb->rf_suballoc_slot = cpu_to_le16(OCFS2_SB(sb)->slot_num);
        new_rb->rf_suballoc_bit = cpu_to_le16(suballoc_bit_start);
        new_rb->rf_blkno = cpu_to_le64(blkno);
        new_rb->rf_cpos = cpu_to_le32(0);
        new_rb->rf_parent = cpu_to_le64(ref_root_bh->b_blocknr);
        new_rb->rf_flags = cpu_to_le32(OCFS2_REFCOUNT_LEAF_FL);
        ocfs2_journal_dirty(handle, new_bh);

        /* Now change the root. */
        memset(&root_rb->rf_list, 0, sb->s_blocksize -
               offsetof(struct ocfs2_refcount_block, rf_list));
        root_rb->rf_list.l_count = cpu_to_le16(ocfs2_extent_recs_per_rb(sb));
        root_rb->rf_clusters = cpu_to_le32(1);
        root_rb->rf_list.l_next_free_rec = cpu_to_le16(1);
        root_rb->rf_list.l_recs[0].e_blkno = cpu_to_le64(blkno);
        root_rb->rf_list.l_recs[0].e_leaf_clusters = cpu_to_le16(1);
        root_rb->rf_flags = cpu_to_le32(OCFS2_REFCOUNT_TREE_FL);

        ocfs2_journal_dirty(handle, ref_root_bh);

        mlog(0, "new leaf block %llu, used %u\n", (unsigned long long)blkno,
             le16_to_cpu(new_rb->rf_records.rl_used));

        *ref_leaf_bh = new_bh;
        new_bh = NULL;
out:
        brelse(new_bh);
        return ret;
}

static int ocfs2_refcount_rec_no_intersect(struct ocfs2_refcount_rec *prev,
                                           struct ocfs2_refcount_rec *next)
{
        if (ocfs2_get_ref_rec_low_cpos(prev) + le32_to_cpu(prev->r_clusters) <=
                ocfs2_get_ref_rec_low_cpos(next))
                return 1;

        return 0;
}

static int cmp_refcount_rec_by_low_cpos(const void *a, const void *b)
{
        const struct ocfs2_refcount_rec *l = a, *r = b;
        u32 l_cpos = ocfs2_get_ref_rec_low_cpos(l);
        u32 r_cpos = ocfs2_get_ref_rec_low_cpos(r);

        if (l_cpos > r_cpos)
                return 1;
        if (l_cpos < r_cpos)
                return -1;
        return 0;
}

static int cmp_refcount_rec_by_cpos(const void *a, const void *b)
{
        const struct ocfs2_refcount_rec *l = a, *r = b;
        u64 l_cpos = le64_to_cpu(l->r_cpos);
        u64 r_cpos = le64_to_cpu(r->r_cpos);

        if (l_cpos > r_cpos)
                return 1;
        if (l_cpos < r_cpos)
                return -1;
        return 0;
}

static void swap_refcount_rec(void *a, void *b, int size)
{
        struct ocfs2_refcount_rec *l = a, *r = b, tmp;

        tmp = *(struct ocfs2_refcount_rec *)l;
        *(struct ocfs2_refcount_rec *)l =
                        *(struct ocfs2_refcount_rec *)r;
        *(struct ocfs2_refcount_rec *)r = tmp;
}

/*
 * The refcount cpos are ordered by their 64bit cpos,
 * But we will use the low 32 bit to be the e_cpos in the b-tree.
 * So we need to make sure that this pos isn't intersected with others.
 *
 * Note: The refcount block is already sorted by their low 32 bit cpos,
 *       So just try the middle pos first, and we will exit when we find
 *       the good position.
 */
static int ocfs2_find_refcount_split_pos(struct ocfs2_refcount_list *rl,
                                         u32 *split_pos, int *split_index)
{
        int num_used = le16_to_cpu(rl->rl_used);
        int delta, middle = num_used / 2;

        for (delta = 0; delta < middle; delta++) {
                /* Let's check delta earlier than middle */
                if (ocfs2_refcount_rec_no_intersect(
                                        &rl->rl_recs[middle - delta - 1],
                                        &rl->rl_recs[middle - delta])) {
                        *split_index = middle - delta;
                        break;
                }

                /* For even counts, don't walk off the end */
                if ((middle + delta + 1) == num_used)
                        continue;

                /* Now try delta past middle */
                if (ocfs2_refcount_rec_no_intersect(
                                        &rl->rl_recs[middle + delta],
                                        &rl->rl_recs[middle + delta + 1])) {
                        *split_index = middle + delta + 1;
                        break;
                }
        }

        if (delta >= middle)
                return -ENOSPC;

        *split_pos = ocfs2_get_ref_rec_low_cpos(&rl->rl_recs[*split_index]);
        return 0;
}

static int ocfs2_divide_leaf_refcount_block(struct buffer_head *ref_leaf_bh,
                                            struct buffer_head *new_bh,
                                            u32 *split_cpos)
{
        int split_index = 0, num_moved, ret;
        u32 cpos = 0;
        struct ocfs2_refcount_block *rb =
                        (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        struct ocfs2_refcount_list *rl = &rb->rf_records;
        struct ocfs2_refcount_block *new_rb =
                        (struct ocfs2_refcount_block *)new_bh->b_data;
        struct ocfs2_refcount_list *new_rl = &new_rb->rf_records;

        mlog(0, "split old leaf refcount block %llu, count = %u, used = %u\n",
             (unsigned long long)ref_leaf_bh->b_blocknr,
             le32_to_cpu(rl->rl_count), le32_to_cpu(rl->rl_used));

        /*
         * XXX: Improvement later.
         * If we know all the high 32 bit cpos is the same, no need to sort.
         *
         * In order to make the whole process safe, we do:
         * 1. sort the entries by their low 32 bit cpos first so that we can
         *    find the split cpos easily.
         * 2. call ocfs2_insert_extent to insert the new refcount block.
         * 3. move the refcount rec to the new block.
         * 4. sort the entries by their 64 bit cpos.
         * 5. dirty the new_rb and rb.
         */
        sort(&rl->rl_recs, le16_to_cpu(rl->rl_used),
             sizeof(struct ocfs2_refcount_rec),
             cmp_refcount_rec_by_low_cpos, swap_refcount_rec);

        ret = ocfs2_find_refcount_split_pos(rl, &cpos, &split_index);
        if (ret) {
                mlog_errno(ret);
                return ret;
        }

        new_rb->rf_cpos = cpu_to_le32(cpos);

        /* move refcount records starting from split_index to the new block. */
        num_moved = le16_to_cpu(rl->rl_used) - split_index;
        memcpy(new_rl->rl_recs, &rl->rl_recs[split_index],
               num_moved * sizeof(struct ocfs2_refcount_rec));

        /*ok, remove the entries we just moved over to the other block. */
        memset(&rl->rl_recs[split_index], 0,
               num_moved * sizeof(struct ocfs2_refcount_rec));

        /* change old and new rl_used accordingly. */
        le16_add_cpu(&rl->rl_used, -num_moved);
        new_rl->rl_used = cpu_to_le32(num_moved);

        sort(&rl->rl_recs, le16_to_cpu(rl->rl_used),
             sizeof(struct ocfs2_refcount_rec),
             cmp_refcount_rec_by_cpos, swap_refcount_rec);

        sort(&new_rl->rl_recs, le16_to_cpu(new_rl->rl_used),
             sizeof(struct ocfs2_refcount_rec),
             cmp_refcount_rec_by_cpos, swap_refcount_rec);

        *split_cpos = cpos;
        return 0;
}

static int ocfs2_new_leaf_refcount_block(handle_t *handle,
                                         struct ocfs2_caching_info *ci,
                                         struct buffer_head *ref_root_bh,
                                         struct buffer_head *ref_leaf_bh,
                                         struct ocfs2_alloc_context *meta_ac)
{
        int ret;
        u16 suballoc_bit_start;
        u32 num_got, new_cpos;
        u64 blkno;
        struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
        struct ocfs2_refcount_block *root_rb =
                        (struct ocfs2_refcount_block *)ref_root_bh->b_data;
        struct buffer_head *new_bh = NULL;
        struct ocfs2_refcount_block *new_rb;
        struct ocfs2_extent_tree ref_et;

        BUG_ON(!(le32_to_cpu(root_rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL));

        ret = ocfs2_journal_access_rb(handle, ci, ref_root_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_claim_metadata(OCFS2_SB(sb), handle, meta_ac, 1,
                                   &suballoc_bit_start, &num_got,
                                   &blkno);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        new_bh = sb_getblk(sb, blkno);
        if (new_bh == NULL) {
                ret = -EIO;
                mlog_errno(ret);
                goto out;
        }
        ocfs2_set_new_buffer_uptodate(ci, new_bh);

        ret = ocfs2_journal_access_rb(handle, ci, new_bh,
                                      OCFS2_JOURNAL_ACCESS_CREATE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /* Initialize ocfs2_refcount_block. */
        new_rb = (struct ocfs2_refcount_block *)new_bh->b_data;
        memset(new_rb, 0, sb->s_blocksize);
        strcpy((void *)new_rb, OCFS2_REFCOUNT_BLOCK_SIGNATURE);
        new_rb->rf_suballoc_slot = cpu_to_le16(OCFS2_SB(sb)->slot_num);
        new_rb->rf_suballoc_bit = cpu_to_le16(suballoc_bit_start);
        new_rb->rf_fs_generation = cpu_to_le32(OCFS2_SB(sb)->fs_generation);
        new_rb->rf_blkno = cpu_to_le64(blkno);
        new_rb->rf_parent = cpu_to_le64(ref_root_bh->b_blocknr);
        new_rb->rf_flags = cpu_to_le32(OCFS2_REFCOUNT_LEAF_FL);
        new_rb->rf_records.rl_count =
                                cpu_to_le16(ocfs2_refcount_recs_per_rb(sb));
        new_rb->rf_generation = root_rb->rf_generation;

        ret = ocfs2_divide_leaf_refcount_block(ref_leaf_bh, new_bh, &new_cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ocfs2_journal_dirty(handle, ref_leaf_bh);
        ocfs2_journal_dirty(handle, new_bh);

        ocfs2_init_refcount_extent_tree(&ref_et, ci, ref_root_bh);

        mlog(0, "insert new leaf block %llu at %u\n",
             (unsigned long long)new_bh->b_blocknr, new_cpos);

        /* Insert the new leaf block with the specific offset cpos. */
        ret = ocfs2_insert_extent(handle, &ref_et, new_cpos, new_bh->b_blocknr,
                                  1, 0, meta_ac);
        if (ret)
                mlog_errno(ret);

out:
        brelse(new_bh);
        return ret;
}

static int ocfs2_expand_refcount_tree(handle_t *handle,
                                      struct ocfs2_caching_info *ci,
                                      struct buffer_head *ref_root_bh,
                                      struct buffer_head *ref_leaf_bh,
                                      struct ocfs2_alloc_context *meta_ac)
{
        int ret;
        struct buffer_head *expand_bh = NULL;

        if (ref_root_bh == ref_leaf_bh) {
                /*
                 * the old root bh hasn't been expanded to a b-tree,
                 * so expand it first.
                 */
                ret = ocfs2_expand_inline_ref_root(handle, ci, ref_root_bh,
                                                   &expand_bh, meta_ac);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        } else {
                expand_bh = ref_leaf_bh;
                get_bh(expand_bh);
        }


        /* Now add a new refcount block into the tree.*/
        ret = ocfs2_new_leaf_refcount_block(handle, ci, ref_root_bh,
                                            expand_bh, meta_ac);
        if (ret)
                mlog_errno(ret);
out:
        brelse(expand_bh);
        return ret;
}

/*
 * Adjust the extent rec in b-tree representing ref_leaf_bh.
 *
 * Only called when we have inserted a new refcount rec at index 0
 * which means ocfs2_extent_rec.e_cpos may need some change.
 */
static int ocfs2_adjust_refcount_rec(handle_t *handle,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *ref_root_bh,
                                     struct buffer_head *ref_leaf_bh,
                                     struct ocfs2_refcount_rec *rec)
{
        int ret = 0, i;
        u32 new_cpos, old_cpos;
        struct ocfs2_path *path = NULL;
        struct ocfs2_extent_tree et;
        struct ocfs2_refcount_block *rb =
                (struct ocfs2_refcount_block *)ref_root_bh->b_data;
        struct ocfs2_extent_list *el;

        if (!(le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL))
                goto out;

        rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        old_cpos = le32_to_cpu(rb->rf_cpos);
        new_cpos = le64_to_cpu(rec->r_cpos) & OCFS2_32BIT_POS_MASK;
        if (old_cpos <= new_cpos)
                goto out;

        ocfs2_init_refcount_extent_tree(&et, ci, ref_root_bh);

        path = ocfs2_new_path_from_et(&et);
        if (!path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_find_path(ci, path, old_cpos);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /*
         * 2 more credits, one for the leaf refcount block, one for
         * the extent block contains the extent rec.
         */
        ret = ocfs2_extend_trans(handle, handle->h_buffer_credits + 2);
        if (ret < 0) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret < 0) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_journal_access_eb(handle, ci, path_leaf_bh(path),
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret < 0) {
                mlog_errno(ret);
                goto out;
        }

        /* change the leaf extent block first. */
        el = path_leaf_el(path);

        for (i = 0; i < le16_to_cpu(el->l_next_free_rec); i++)
                if (le32_to_cpu(el->l_recs[i].e_cpos) == old_cpos)
                        break;

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

        el->l_recs[i].e_cpos = cpu_to_le32(new_cpos);

        /* change the r_cpos in the leaf block. */
        rb->rf_cpos = cpu_to_le32(new_cpos);

        ocfs2_journal_dirty(handle, path_leaf_bh(path));
        ocfs2_journal_dirty(handle, ref_leaf_bh);

out:
        ocfs2_free_path(path);
        return ret;
}

static int ocfs2_insert_refcount_rec(handle_t *handle,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *ref_root_bh,
                                     struct buffer_head *ref_leaf_bh,
                                     struct ocfs2_refcount_rec *rec,
                                     int index,
                                     struct ocfs2_alloc_context *meta_ac)
{
        int ret;
        struct ocfs2_refcount_block *rb =
                        (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        struct ocfs2_refcount_list *rf_list = &rb->rf_records;
        struct buffer_head *new_bh = NULL;

        BUG_ON(le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL);

        if (rf_list->rl_used == rf_list->rl_count) {
                u64 cpos = le64_to_cpu(rec->r_cpos);
                u32 len = le32_to_cpu(rec->r_clusters);

                ret = ocfs2_expand_refcount_tree(handle, ci, ref_root_bh,
                                                 ref_leaf_bh, meta_ac);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                                             cpos, len, NULL, &index,
                                             &new_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ref_leaf_bh = new_bh;
                rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
                rf_list = &rb->rf_records;
        }

        ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        if (index < le16_to_cpu(rf_list->rl_used))
                memmove(&rf_list->rl_recs[index + 1],
                        &rf_list->rl_recs[index],
                        (le16_to_cpu(rf_list->rl_used) - index) *
                         sizeof(struct ocfs2_refcount_rec));

        mlog(0, "insert refcount record start %llu, len %u, count %u "
             "to leaf block %llu at index %d\n",
             (unsigned long long)le64_to_cpu(rec->r_cpos),
             le32_to_cpu(rec->r_clusters), le32_to_cpu(rec->r_refcount),
             (unsigned long long)ref_leaf_bh->b_blocknr, index);

        rf_list->rl_recs[index] = *rec;

        le16_add_cpu(&rf_list->rl_used, 1);

        ocfs2_refcount_rec_merge(rb, index);

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

        if (index == 0) {
                ret = ocfs2_adjust_refcount_rec(handle, ci,
                                                ref_root_bh,
                                                ref_leaf_bh, rec);
                if (ret)
                        mlog_errno(ret);
        }
out:
        brelse(new_bh);
        return ret;
}

/*
 * Split the refcount_rec indexed by "index" in ref_leaf_bh.
 * This is much simple than our b-tree code.
 * split_rec is the new refcount rec we want to insert.
 * If split_rec->r_refcount > 0, we are changing the refcount(in case we
 * increase refcount or decrease a refcount to non-zero).
 * If split_rec->r_refcount == 0, we are punching a hole in current refcount
 * rec( in case we decrease a refcount to zero).
 */
static int ocfs2_split_refcount_rec(handle_t *handle,
                                    struct ocfs2_caching_info *ci,
                                    struct buffer_head *ref_root_bh,
                                    struct buffer_head *ref_leaf_bh,
                                    struct ocfs2_refcount_rec *split_rec,
                                    int index,
                                    struct ocfs2_alloc_context *meta_ac,
                                    struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        int ret, recs_need;
        u32 len;
        struct ocfs2_refcount_block *rb =
                        (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        struct ocfs2_refcount_list *rf_list = &rb->rf_records;
        struct ocfs2_refcount_rec *orig_rec = &rf_list->rl_recs[index];
        struct ocfs2_refcount_rec *tail_rec = NULL;
        struct buffer_head *new_bh = NULL;

        BUG_ON(le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL);

        mlog(0, "original r_pos %llu, cluster %u, split %llu, cluster %u\n",
             le64_to_cpu(orig_rec->r_cpos), le32_to_cpu(orig_rec->r_clusters),
             le64_to_cpu(split_rec->r_cpos),
             le32_to_cpu(split_rec->r_clusters));

        /*
         * If we just need to split the header or tail clusters,
         * no more recs are needed, just split is OK.
         * Otherwise we at least need one new recs.
         */
        if (!split_rec->r_refcount &&
            (split_rec->r_cpos == orig_rec->r_cpos ||
             le64_to_cpu(split_rec->r_cpos) +
             le32_to_cpu(split_rec->r_clusters) ==
             le64_to_cpu(orig_rec->r_cpos) + le32_to_cpu(orig_rec->r_clusters)))
                recs_need = 0;
        else
                recs_need = 1;

        /*
         * We need one more rec if we split in the middle and the new rec have
         * some refcount in it.
         */
        if (split_rec->r_refcount &&
            (split_rec->r_cpos != orig_rec->r_cpos &&
             le64_to_cpu(split_rec->r_cpos) +
             le32_to_cpu(split_rec->r_clusters) !=
             le64_to_cpu(orig_rec->r_cpos) + le32_to_cpu(orig_rec->r_clusters)))
                recs_need++;

        /* If the leaf block don't have enough record, expand it. */
        if (le16_to_cpu(rf_list->rl_used) + recs_need > rf_list->rl_count) {
                struct ocfs2_refcount_rec tmp_rec;
                u64 cpos = le64_to_cpu(orig_rec->r_cpos);
                len = le32_to_cpu(orig_rec->r_clusters);
                ret = ocfs2_expand_refcount_tree(handle, ci, ref_root_bh,
                                                 ref_leaf_bh, meta_ac);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                /*
                 * We have to re-get it since now cpos may be moved to
                 * another leaf block.
                 */
                ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                                             cpos, len, &tmp_rec, &index,
                                             &new_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                ref_leaf_bh = new_bh;
                rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
                rf_list = &rb->rf_records;
                orig_rec = &rf_list->rl_recs[index];
        }

        ret = ocfs2_journal_access_rb(handle, ci, ref_leaf_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        /*
         * We have calculated out how many new records we need and store
         * in recs_need, so spare enough space first by moving the records
         * after "index" to the end.
         */
        if (index != le16_to_cpu(rf_list->rl_used) - 1)
                memmove(&rf_list->rl_recs[index + 1 + recs_need],
                        &rf_list->rl_recs[index + 1],
                        (le16_to_cpu(rf_list->rl_used) - index - 1) *
                         sizeof(struct ocfs2_refcount_rec));

        len = (le64_to_cpu(orig_rec->r_cpos) +
              le32_to_cpu(orig_rec->r_clusters)) -
              (le64_to_cpu(split_rec->r_cpos) +
              le32_to_cpu(split_rec->r_clusters));

        /*
         * If we have "len", the we will split in the tail and move it
         * to the end of the space we have just spared.
         */
        if (len) {
                tail_rec = &rf_list->rl_recs[index + recs_need];

                memcpy(tail_rec, orig_rec, sizeof(struct ocfs2_refcount_rec));
                le64_add_cpu(&tail_rec->r_cpos,
                             le32_to_cpu(tail_rec->r_clusters) - len);
                tail_rec->r_clusters = le32_to_cpu(len);
        }

        /*
         * If the split pos isn't the same as the original one, we need to
         * split in the head.
         *
         * Note: We have the chance that split_rec.r_refcount = 0,
         * recs_need = 0 and len > 0, which means we just cut the head from
         * the orig_rec and in that case we have done some modification in
         * orig_rec above, so the check for r_cpos is faked.
         */
        if (split_rec->r_cpos != orig_rec->r_cpos && tail_rec != orig_rec) {
                len = le64_to_cpu(split_rec->r_cpos) -
                      le64_to_cpu(orig_rec->r_cpos);
                orig_rec->r_clusters = cpu_to_le32(len);
                index++;
        }

        le16_add_cpu(&rf_list->rl_used, recs_need);

        if (split_rec->r_refcount) {
                rf_list->rl_recs[index] = *split_rec;
                mlog(0, "insert refcount record start %llu, len %u, count %u "
                     "to leaf block %llu at index %d\n",
                     (unsigned long long)le64_to_cpu(split_rec->r_cpos),
                     le32_to_cpu(split_rec->r_clusters),
                     le32_to_cpu(split_rec->r_refcount),
                     (unsigned long long)ref_leaf_bh->b_blocknr, index);

                ocfs2_refcount_rec_merge(rb, index);
        }

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

out:
        brelse(new_bh);
        return ret;
}

static int __ocfs2_increase_refcount(handle_t *handle,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *ref_root_bh,
                                     u64 cpos, u32 len,
                                     struct ocfs2_alloc_context *meta_ac,
                                     struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        int ret = 0, index;
        struct buffer_head *ref_leaf_bh = NULL;
        struct ocfs2_refcount_rec rec;
        unsigned int set_len = 0;

        mlog(0, "Tree owner %llu, add refcount start %llu, len %u\n",
             (unsigned long long)ocfs2_metadata_cache_owner(ci),
             (unsigned long long)cpos, len);

        while (len) {
                ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                                             cpos, len, &rec, &index,
                                             &ref_leaf_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                set_len = le32_to_cpu(rec.r_clusters);

                /*
                 * Here we may meet with 3 situations:
                 *
                 * 1. If we find an already existing record, and the length
                 *    is the same, cool, we just need to increase the r_refcount
                 *    and it is OK.
                 * 2. If we find a hole, just insert it with r_refcount = 1.
                 * 3. If we are in the middle of one extent record, split
                 *    it.
                 */
                if (rec.r_refcount && le64_to_cpu(rec.r_cpos) == cpos &&
                    set_len <= len) {
                        mlog(0, "increase refcount rec, start %llu, len %u, "
                             "count %u\n", (unsigned long long)cpos, set_len,
                             le32_to_cpu(rec.r_refcount));
                        ret = ocfs2_change_refcount_rec(handle, ci,
                                                        ref_leaf_bh, index, 1);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }
                } else if (!rec.r_refcount) {
                        rec.r_refcount = cpu_to_le32(1);

                        mlog(0, "insert refcount rec, start %llu, len %u\n",
                             (unsigned long long)le64_to_cpu(rec.r_cpos),
                             set_len);
                        ret = ocfs2_insert_refcount_rec(handle, ci, ref_root_bh,
                                                        ref_leaf_bh,
                                                        &rec, index, meta_ac);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }
                } else  {
                        set_len = min((u64)(cpos + len),
                                      le64_to_cpu(rec.r_cpos) + set_len) - cpos;
                        rec.r_cpos = cpu_to_le64(cpos);
                        rec.r_clusters = cpu_to_le32(set_len);
                        le32_add_cpu(&rec.r_refcount, 1);

                        mlog(0, "split refcount rec, start %llu, "
                             "len %u, count %u\n",
                             (unsigned long long)le64_to_cpu(rec.r_cpos),
                             set_len, le32_to_cpu(rec.r_refcount));
                        ret = ocfs2_split_refcount_rec(handle, ci,
                                                       ref_root_bh, ref_leaf_bh,
                                                       &rec, index,
                                                       meta_ac, dealloc);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }
                }

                cpos += set_len;
                len -= set_len;
                brelse(ref_leaf_bh);
                ref_leaf_bh = NULL;
        }

out:
        brelse(ref_leaf_bh);
        return ret;
}

static int ocfs2_remove_refcount_extent(handle_t *handle,
                                struct ocfs2_caching_info *ci,
                                struct buffer_head *ref_root_bh,
                                struct buffer_head *ref_leaf_bh,
                                struct ocfs2_alloc_context *meta_ac,
                                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        int ret;
        struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
        struct ocfs2_refcount_block *rb =
                        (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        struct ocfs2_extent_tree et;

        BUG_ON(rb->rf_records.rl_used);

        ocfs2_init_refcount_extent_tree(&et, ci, ref_root_bh);
        ret = ocfs2_remove_extent(handle, &et, le32_to_cpu(rb->rf_cpos),
                                  1, meta_ac, dealloc);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ocfs2_remove_from_cache(ci, ref_leaf_bh);

        /*
         * add the freed block to the dealloc so that it will be freed
         * when we run dealloc.
         */
        ret = ocfs2_cache_block_dealloc(dealloc, EXTENT_ALLOC_SYSTEM_INODE,
                                        le16_to_cpu(rb->rf_suballoc_slot),
                                        le64_to_cpu(rb->rf_blkno),
                                        le16_to_cpu(rb->rf_suballoc_bit));
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_journal_access_rb(handle, ci, ref_root_bh,
                                      OCFS2_JOURNAL_ACCESS_WRITE);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;

        le32_add_cpu(&rb->rf_clusters, -1);

        /*
         * check whether we need to restore the root refcount block if
         * there is no leaf extent block at atll.
         */
        if (!rb->rf_list.l_next_free_rec) {
                BUG_ON(rb->rf_clusters);

                mlog(0, "reset refcount tree root %llu to be a record block.\n",
                     (unsigned long long)ref_root_bh->b_blocknr);

                rb->rf_flags = 0;
                rb->rf_parent = 0;
                rb->rf_cpos = 0;
                memset(&rb->rf_records, 0, sb->s_blocksize -
                       offsetof(struct ocfs2_refcount_block, rf_records));
                rb->rf_records.rl_count =
                                cpu_to_le16(ocfs2_refcount_recs_per_rb(sb));
        }

        ocfs2_journal_dirty(handle, ref_root_bh);

out:
        return ret;
}

static int ocfs2_decrease_refcount_rec(handle_t *handle,
                                struct ocfs2_caching_info *ci,
                                struct buffer_head *ref_root_bh,
                                struct buffer_head *ref_leaf_bh,
                                int index, u64 cpos, unsigned int len,
                                struct ocfs2_alloc_context *meta_ac,
                                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        int ret;
        struct ocfs2_refcount_block *rb =
                        (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;
        struct ocfs2_refcount_rec *rec = &rb->rf_records.rl_recs[index];

        BUG_ON(cpos < le64_to_cpu(rec->r_cpos));
        BUG_ON(cpos + len >
               le64_to_cpu(rec->r_cpos) + le32_to_cpu(rec->r_clusters));

        if (cpos == le64_to_cpu(rec->r_cpos) &&
            len == le32_to_cpu(rec->r_clusters))
                ret = ocfs2_change_refcount_rec(handle, ci,
                                                ref_leaf_bh, index, -1);
        else {
                struct ocfs2_refcount_rec split = *rec;
                split.r_cpos = cpu_to_le64(cpos);
                split.r_clusters = cpu_to_le32(len);

                le32_add_cpu(&split.r_refcount, -1);

                mlog(0, "split refcount rec, start %llu, "
                     "len %u, count %u, original start %llu, len %u\n",
                     (unsigned long long)le64_to_cpu(split.r_cpos),
                     len, le32_to_cpu(split.r_refcount),
                     (unsigned long long)le64_to_cpu(rec->r_cpos),
                     le32_to_cpu(rec->r_clusters));
                ret = ocfs2_split_refcount_rec(handle, ci,
                                               ref_root_bh, ref_leaf_bh,
                                               &split, index,
                                               meta_ac, dealloc);
        }

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

        /* Remove the leaf refcount block if it contains no refcount record. */
        if (!rb->rf_records.rl_used && ref_leaf_bh != ref_root_bh) {
                ret = ocfs2_remove_refcount_extent(handle, ci, ref_root_bh,
                                                   ref_leaf_bh, meta_ac,
                                                   dealloc);
                if (ret)
                        mlog_errno(ret);
        }

out:
        return ret;
}

static int __ocfs2_decrease_refcount(handle_t *handle,
                                     struct ocfs2_caching_info *ci,
                                     struct buffer_head *ref_root_bh,
                                     u64 cpos, u32 len,
                                     struct ocfs2_alloc_context *meta_ac,
                                     struct ocfs2_cached_dealloc_ctxt *dealloc,
                                     int delete)
{
        int ret = 0, index = 0;
        struct ocfs2_refcount_rec rec;
        unsigned int r_count = 0, r_len;
        struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
        struct buffer_head *ref_leaf_bh = NULL;

        mlog(0, "Tree owner %llu, decrease refcount start %llu, "
             "len %u, delete %u\n",
             (unsigned long long)ocfs2_metadata_cache_owner(ci),
             (unsigned long long)cpos, len, delete);

        while (len) {
                ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                                             cpos, len, &rec, &index,
                                             &ref_leaf_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                r_count = le32_to_cpu(rec.r_refcount);
                BUG_ON(r_count == 0);
                if (!delete)
                        BUG_ON(r_count > 1);

                r_len = min((u64)(cpos + len), le64_to_cpu(rec.r_cpos) +
                              le32_to_cpu(rec.r_clusters)) - cpos;

                ret = ocfs2_decrease_refcount_rec(handle, ci, ref_root_bh,
                                                  ref_leaf_bh, index,
                                                  cpos, r_len,
                                                  meta_ac, dealloc);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                if (le32_to_cpu(rec.r_refcount) == 1 && delete) {
                        ret = ocfs2_cache_cluster_dealloc(dealloc,
                                          ocfs2_clusters_to_blocks(sb, cpos),
                                                          r_len);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }
                }

                cpos += r_len;
                len -= r_len;
                brelse(ref_leaf_bh);
                ref_leaf_bh = NULL;
        }

out:
        brelse(ref_leaf_bh);
        return ret;
}

/* Caller must hold refcount tree lock. */
int ocfs2_decrease_refcount(struct inode *inode,
                            handle_t *handle, u32 cpos, u32 len,
                            struct ocfs2_alloc_context *meta_ac,
                            struct ocfs2_cached_dealloc_ctxt *dealloc,
                            int delete)
{
        int ret;
        u64 ref_blkno;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        struct buffer_head *ref_root_bh = NULL;
        struct ocfs2_refcount_tree *tree;

        BUG_ON(!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));

        ret = ocfs2_get_refcount_block(inode, &ref_blkno);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_get_refcount_tree(OCFS2_SB(inode->i_sb), ref_blkno, &tree);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_read_refcount_block(&tree->rf_ci, tree->rf_blkno,
                                        &ref_root_bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = __ocfs2_decrease_refcount(handle, &tree->rf_ci, ref_root_bh,
                                        cpos, len, meta_ac, dealloc, delete);
        if (ret)
                mlog_errno(ret);
out:
        brelse(ref_root_bh);
        return ret;
}

/*
 * Mark the already-existing extent at cpos as refcounted for len clusters.
 * This adds the refcount extent flag.
 *
 * If the existing extent is larger than the request, initiate a
 * split. An attempt will be made at merging with adjacent extents.
 *
 * The caller is responsible for passing down meta_ac if we'll need it.
 */
static int ocfs2_mark_extent_refcounted(struct inode *inode,
                                struct ocfs2_extent_tree *et,
                                handle_t *handle, u32 cpos,
                                u32 len, u32 phys,
                                struct ocfs2_alloc_context *meta_ac,
                                struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        int ret;

        mlog(0, "Inode %lu refcount tree cpos %u, len %u, phys cluster %u\n",
             inode->i_ino, cpos, len, phys);

        if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb))) {
                ocfs2_error(inode->i_sb, "Inode %lu want to use refcount "
                            "tree, but the feature bit is not set in the "
                            "super block.", inode->i_ino);
                ret = -EROFS;
                goto out;
        }

        ret = ocfs2_change_extent_flag(handle, et, cpos,
                                       len, phys, meta_ac, dealloc,
                                       OCFS2_EXT_REFCOUNTED, 0);
        if (ret)
                mlog_errno(ret);

out:
        return ret;
}

/*
 * Given some contiguous physical clusters, calculate what we need
 * for modifying their refcount.
 */
static int ocfs2_calc_refcount_meta_credits(struct super_block *sb,
                                            struct ocfs2_caching_info *ci,
                                            struct buffer_head *ref_root_bh,
                                            u64 start_cpos,
                                            u32 clusters,
                                            int *meta_add,
                                            int *credits)
{
        int ret = 0, index, ref_blocks = 0, recs_add = 0;
        u64 cpos = start_cpos;
        struct ocfs2_refcount_block *rb;
        struct ocfs2_refcount_rec rec;
        struct buffer_head *ref_leaf_bh = NULL, *prev_bh = NULL;
        u32 len;

        mlog(0, "start_cpos %llu, clusters %u\n",
             (unsigned long long)start_cpos, clusters);
        while (clusters) {
                ret = ocfs2_get_refcount_rec(ci, ref_root_bh,
                                             cpos, clusters, &rec,
                                             &index, &ref_leaf_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

                if (ref_leaf_bh != prev_bh) {
                        /*
                         * Now we encounter a new leaf block, so calculate
                         * whether we need to extend the old leaf.
                         */
                        if (prev_bh) {
                                rb = (struct ocfs2_refcount_block *)
                                                        prev_bh->b_data;

                                if (le64_to_cpu(rb->rf_records.rl_used) +
                                    recs_add >
                                    le16_to_cpu(rb->rf_records.rl_count))
                                        ref_blocks++;
                        }

                        recs_add = 0;
                        *credits += 1;
                        brelse(prev_bh);
                        prev_bh = ref_leaf_bh;
                        get_bh(prev_bh);
                }

                rb = (struct ocfs2_refcount_block *)ref_leaf_bh->b_data;

                mlog(0, "recs_add %d,cpos %llu, clusters %u, rec->r_cpos %llu,"
                     "rec->r_clusters %u, rec->r_refcount %u, index %d\n",
                     recs_add, (unsigned long long)cpos, clusters,
                     (unsigned long long)le64_to_cpu(rec.r_cpos),
                     le32_to_cpu(rec.r_clusters),
                     le32_to_cpu(rec.r_refcount), index);

                len = min((u64)cpos + clusters, le64_to_cpu(rec.r_cpos) +
                          le32_to_cpu(rec.r_clusters)) - cpos;
                /*
                 * If the refcount rec already exist, cool. We just need
                 * to check whether there is a split. Otherwise we just need
                 * to increase the refcount.
                 * If we will insert one, increases recs_add.
                 *
                 * We record all the records which will be inserted to the
                 * same refcount block, so that we can tell exactly whether
                 * we need a new refcount block or not.
                 */
                if (rec.r_refcount) {
                        /* Check whether we need a split at the beginning. */
                        if (cpos == start_cpos &&
                            cpos != le64_to_cpu(rec.r_cpos))
                                recs_add++;

                        /* Check whether we need a split in the end. */
                        if (cpos + clusters < le64_to_cpu(rec.r_cpos) +
                            le32_to_cpu(rec.r_clusters))
                                recs_add++;
                } else
                        recs_add++;

                brelse(ref_leaf_bh);
                ref_leaf_bh = NULL;
                clusters -= len;
                cpos += len;
        }

        if (prev_bh) {
                rb = (struct ocfs2_refcount_block *)prev_bh->b_data;

                if (le64_to_cpu(rb->rf_records.rl_used) + recs_add >
                    le16_to_cpu(rb->rf_records.rl_count))
                        ref_blocks++;

                *credits += 1;
        }

        if (!ref_blocks)
                goto out;

        mlog(0, "we need ref_blocks %d\n", ref_blocks);
        *meta_add += ref_blocks;
        *credits += ref_blocks;

        /*
         * So we may need ref_blocks to insert into the tree.
         * That also means we need to change the b-tree and add that number
         * of records since we never merge them.
         * We need one more block for expansion since the new created leaf
         * block is also full and needs split.
         */
        rb = (struct ocfs2_refcount_block *)ref_root_bh->b_data;
        if (le32_to_cpu(rb->rf_flags) & OCFS2_REFCOUNT_TREE_FL) {
                struct ocfs2_extent_tree et;

                ocfs2_init_refcount_extent_tree(&et, ci, ref_root_bh);
                *meta_add += ocfs2_extend_meta_needed(et.et_root_el);
                *credits += ocfs2_calc_extend_credits(sb,
                                                      et.et_root_el,
                                                      ref_blocks);
        } else {
                *credits += OCFS2_EXPAND_REFCOUNT_TREE_CREDITS;
                *meta_add += 1;
        }

out:
        brelse(ref_leaf_bh);
        brelse(prev_bh);
        return ret;
}

/*
 * For refcount tree, we will decrease some contiguous clusters
 * refcount count, so just go through it to see how many blocks
 * we gonna touch and whether we need to create new blocks.
 *
 * Normally the refcount blocks store these refcount should be
 * continguous also, so that we can get the number easily.
 * As for meta_ac, we will at most add split 2 refcount record and
 * 2 more refcount block, so just check it in a rough way.
 *
 * Caller must hold refcount tree lock.
 */
int ocfs2_prepare_refcount_change_for_del(struct inode *inode,
                                          struct buffer_head *di_bh,
                                          u64 phys_blkno,
                                          u32 clusters,
                                          int *credits,
                                          struct ocfs2_alloc_context **meta_ac)
{
        int ret, ref_blocks = 0;
        struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        struct buffer_head *ref_root_bh = NULL;
        struct ocfs2_refcount_tree *tree;
        u64 start_cpos = ocfs2_blocks_to_clusters(inode->i_sb, phys_blkno);

        if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb))) {
                ocfs2_error(inode->i_sb, "Inode %lu want to use refcount "
                            "tree, but the feature bit is not set in the "
                            "super block.", inode->i_ino);
                ret = -EROFS;
                goto out;
        }

        BUG_ON(!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));

        ret = ocfs2_get_refcount_tree(OCFS2_SB(inode->i_sb),
                                      le64_to_cpu(di->i_refcount_loc), &tree);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_read_refcount_block(&tree->rf_ci,
                                        le64_to_cpu(di->i_refcount_loc),
                                        &ref_root_bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_calc_refcount_meta_credits(inode->i_sb,
                                               &tree->rf_ci,
                                               ref_root_bh,
                                               start_cpos, clusters,
                                               &ref_blocks, credits);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        mlog(0, "reserve new metadata %d, credits = %d\n",
             ref_blocks, *credits);

        if (ref_blocks) {
                ret = ocfs2_reserve_new_metadata_blocks(OCFS2_SB(inode->i_sb),
                                                        ref_blocks, meta_ac);
                if (ret)
                        mlog_errno(ret);
        }

out:
        brelse(ref_root_bh);
        return ret;
}

#define MAX_CONTIG_BYTES        1048576

static inline unsigned int ocfs2_cow_contig_clusters(struct super_block *sb)
{
        return ocfs2_clusters_for_bytes(sb, MAX_CONTIG_BYTES);
}

static inline unsigned int ocfs2_cow_contig_mask(struct super_block *sb)
{
        return ~(ocfs2_cow_contig_clusters(sb) - 1);
}

/*
 * Given an extent that starts at 'start' and an I/O that starts at 'cpos',
 * find an offset (start + (n * contig_clusters)) that is closest to cpos
 * while still being less than or equal to it.
 *
 * The goal is to break the extent at a multiple of contig_clusters.
 */
static inline unsigned int ocfs2_cow_align_start(struct super_block *sb,
                                                 unsigned int start,
                                                 unsigned int cpos)
{
        BUG_ON(start > cpos);

        return start + ((cpos - start) & ocfs2_cow_contig_mask(sb));
}

/*
 * Given a cluster count of len, pad it out so that it is a multiple
 * of contig_clusters.
 */
static inline unsigned int ocfs2_cow_align_length(struct super_block *sb,
                                                  unsigned int len)
{
        unsigned int padded =
                (len + (ocfs2_cow_contig_clusters(sb) - 1)) &
                ocfs2_cow_contig_mask(sb);

        /* Did we wrap? */
        if (padded < len)
                padded = UINT_MAX;

        return padded;
}

/*
 * Calculate out the start and number of virtual clusters we need to to CoW.
 *
 * cpos is vitual start cluster position we want to do CoW in a
 * file and write_len is the cluster length.
 *
 * Normal we will start CoW from the beginning of extent record cotaining cpos.
 * We try to break up extents on boundaries of MAX_CONTIG_BYTES so that we
 * get good I/O from the resulting extent tree.
 */
static int ocfs2_refcount_cal_cow_clusters(struct inode *inode,
                                           struct buffer_head *di_bh,
                                           u32 cpos,
                                           u32 write_len,
                                           u32 *cow_start,
                                           u32 *cow_len)
{
        int ret = 0;
        struct ocfs2_dinode *di = (struct ocfs2_dinode *) di_bh->b_data;
        struct ocfs2_extent_list *el = &di->id2.i_list;
        int tree_height = le16_to_cpu(el->l_tree_depth), i;
        struct buffer_head *eb_bh = NULL;
        struct ocfs2_extent_block *eb = NULL;
        struct ocfs2_extent_rec *rec;
        unsigned int want_clusters, rec_end = 0;
        int contig_clusters = ocfs2_cow_contig_clusters(inode->i_sb);
        int leaf_clusters;

        if (tree_height > 0) {
                ret = ocfs2_find_leaf(INODE_CACHE(inode), el, cpos, &eb_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }

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

                if (el->l_tree_depth) {
                        ocfs2_error(inode->i_sb,
                                    "Inode %lu has non zero tree depth in "
                                    "leaf block %llu\n", inode->i_ino,
                                    (unsigned long long)eb_bh->b_blocknr);
                        ret = -EROFS;
                        goto out;
                }
        }

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

                if (ocfs2_is_empty_extent(rec)) {
                        mlog_bug_on_msg(i != 0, "Inode %lu has empty record in "
                                        "index %d\n", inode->i_ino, i);
                        continue;
                }

                if (le32_to_cpu(rec->e_cpos) +
                    le16_to_cpu(rec->e_leaf_clusters) <= cpos)
                        continue;

                if (*cow_len == 0) {
                        /*
                         * We should find a refcounted record in the
                         * first pass.
                         */
                        BUG_ON(!(rec->e_flags & OCFS2_EXT_REFCOUNTED));
                        *cow_start = le32_to_cpu(rec->e_cpos);
                }

                /*
                 * If we encounter a hole or a non-refcounted record,
                 * stop the search.
                 */
                if ((!(rec->e_flags & OCFS2_EXT_REFCOUNTED)) ||
                    (*cow_len && rec_end != le32_to_cpu(rec->e_cpos)))
                        break;

                leaf_clusters = le16_to_cpu(rec->e_leaf_clusters);
                rec_end = le32_to_cpu(rec->e_cpos) + leaf_clusters;

                /*
                 * How many clusters do we actually need from
                 * this extent?  First we see how many we actually
                 * need to complete the write.  If that's smaller
                 * than contig_clusters, we try for contig_clusters.
                 */
                if (!*cow_len)
                        want_clusters = write_len;
                else
                        want_clusters = (cpos + write_len) -
                                (*cow_start + *cow_len);
                if (want_clusters < contig_clusters)
                        want_clusters = contig_clusters;

                /*
                 * If the write does not cover the whole extent, we
                 * need to calculate how we're going to split the extent.
                 * We try to do it on contig_clusters boundaries.
                 *
                 * Any extent smaller than contig_clusters will be
                 * CoWed in its entirety.
                 */
                if (leaf_clusters <= contig_clusters)
                        *cow_len += leaf_clusters;
                else if (*cow_len || (*cow_start == cpos)) {
                        /*
                         * This extent needs to be CoW'd from its
                         * beginning, so all we have to do is compute
                         * how many clusters to grab.  We align
                         * want_clusters to the edge of contig_clusters
                         * to get better I/O.
                         */
                        want_clusters = ocfs2_cow_align_length(inode->i_sb,
                                                               want_clusters);

                        if (leaf_clusters < want_clusters)
                                *cow_len += leaf_clusters;
                        else
                                *cow_len += want_clusters;
                } else if ((*cow_start + contig_clusters) >=
                           (cpos + write_len)) {
                        /*
                         * Breaking off contig_clusters at the front
                         * of the extent will cover our write.  That's
                         * easy.
                         */
                        *cow_len = contig_clusters;
                } else if ((rec_end - cpos) <= contig_clusters) {
                        /*
                         * Breaking off contig_clusters at the tail of
                         * this extent will cover cpos.
                         */
                        *cow_start = rec_end - contig_clusters;
                        *cow_len = contig_clusters;
                } else if ((rec_end - cpos) <= want_clusters) {
                        /*
                         * While we can't fit the entire write in this
                         * extent, we know that the write goes from cpos
                         * to the end of the extent.  Break that off.
                         * We try to break it at some multiple of
                         * contig_clusters from the front of the extent.
                         * Failing that (ie, cpos is within
                         * contig_clusters of the front), we'll CoW the
                         * entire extent.
                         */
                        *cow_start = ocfs2_cow_align_start(inode->i_sb,
                                                           *cow_start, cpos);
                        *cow_len = rec_end - *cow_start;
                } else {
                        /*
                         * Ok, the entire write lives in the middle of
                         * this extent.  Let's try to slice the extent up
                         * nicely.  Optimally, our CoW region starts at
                         * m*contig_clusters from the beginning of the
                         * extent and goes for n*contig_clusters,
                         * covering the entire write.
                         */
                        *cow_start = ocfs2_cow_align_start(inode->i_sb,
                                                           *cow_start, cpos);

                        want_clusters = (cpos + write_len) - *cow_start;
                        want_clusters = ocfs2_cow_align_length(inode->i_sb,
                                                               want_clusters);
                        if (*cow_start + want_clusters <= rec_end)
                                *cow_len = want_clusters;
                        else
                                *cow_len = rec_end - *cow_start;
                }

                /* Have we covered our entire write yet? */
                if ((*cow_start + *cow_len) >= (cpos + write_len))
                        break;

                /*
                 * If we reach the end of the extent block and don't get enough
                 * clusters, continue with the next extent block if possible.
                 */
                if (i + 1 == le16_to_cpu(el->l_next_free_rec) &&
                    eb && eb->h_next_leaf_blk) {
                        brelse(eb_bh);
                        eb_bh = NULL;

                        ret = ocfs2_read_extent_block(INODE_CACHE(inode),
                                               le64_to_cpu(eb->h_next_leaf_blk),
                                               &eb_bh);
                        if (ret) {
                                mlog_errno(ret);
                                goto out;
                        }

                        eb = (struct ocfs2_extent_block *) eb_bh->b_data;
                        el = &eb->h_list;
                        i = -1;
                }
        }

out:
        brelse(eb_bh);
        return ret;
}

/*
 * Prepare meta_ac, data_ac and calculate credits when we want to add some
 * num_clusters in data_tree "et" and change the refcount for the old
 * clusters(starting form p_cluster) in the refcount tree.
 *
 * Note:
 * 1. since we may split the old tree, so we at most will need num_clusters + 2
 *    more new leaf records.
 * 2. In some case, we may not need to reserve new clusters(e.g, reflink), so
 *    just give data_ac = NULL.
 */
static int ocfs2_lock_refcount_allocators(struct super_block *sb,
                                        u32 p_cluster, u32 num_clusters,
                                        struct ocfs2_extent_tree *et,
                                        struct ocfs2_caching_info *ref_ci,
                                        struct buffer_head *ref_root_bh,
                                        struct ocfs2_alloc_context **meta_ac,
                                        struct ocfs2_alloc_context **data_ac,
                                        int *credits)
{
        int ret = 0, meta_add = 0;
        int num_free_extents = ocfs2_num_free_extents(OCFS2_SB(sb), et);

        if (num_free_extents < 0) {
                ret = num_free_extents;
                mlog_errno(ret);
                goto out;
        }

        if (num_free_extents < num_clusters + 2)
                meta_add =
                        ocfs2_extend_meta_needed(et->et_root_el);

        *credits += ocfs2_calc_extend_credits(sb, et->et_root_el,
                                              num_clusters + 2);

        ret = ocfs2_calc_refcount_meta_credits(sb, ref_ci, ref_root_bh,
                                               p_cluster, num_clusters,
                                               &meta_add, credits);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        mlog(0, "reserve new metadata %d, clusters %u, credits = %d\n",
             meta_add, num_clusters, *credits);
        ret = ocfs2_reserve_new_metadata_blocks(OCFS2_SB(sb), meta_add,
                                                meta_ac);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        if (data_ac) {
                ret = ocfs2_reserve_clusters(OCFS2_SB(sb), num_clusters,
                                             data_ac);
                if (ret)
                        mlog_errno(ret);
        }

out:
        if (ret) {
                if (*meta_ac) {
                        ocfs2_free_alloc_context(*meta_ac);
                        *meta_ac = NULL;
                }
        }

        return ret;
}

static int ocfs2_clear_cow_buffer(handle_t *handle, struct buffer_head *bh)
{
        BUG_ON(buffer_dirty(bh));

        clear_buffer_mapped(bh);

        return 0;
}

static int ocfs2_duplicate_clusters(handle_t *handle,
                                    struct ocfs2_cow_context *context,
                                    u32 cpos, u32 old_cluster,
                                    u32 new_cluster, u32 new_len)
{
        int ret = 0, partial;
        struct ocfs2_caching_info *ci = context->di_et.et_ci;
        struct super_block *sb = ocfs2_metadata_cache_get_super(ci);
        u64 new_block = ocfs2_clusters_to_blocks(sb, new_cluster);
        struct page *page;
        pgoff_t page_index;
        unsigned int from, to;
        loff_t offset, end, map_end;
        struct address_space *mapping = context->inode->i_mapping;

        mlog(0, "old_cluster %u, new %u, len %u at offset %u\n", old_cluster,
             new_cluster, new_len, cpos);

        offset = ((loff_t)cpos) << OCFS2_SB(sb)->s_clustersize_bits;
        end = offset + (new_len << OCFS2_SB(sb)->s_clustersize_bits);

        while (offset < end) {
                page_index = offset >> PAGE_CACHE_SHIFT;
                map_end = (page_index + 1) << PAGE_CACHE_SHIFT;
                if (map_end > end)
                        map_end = end;

                /* from, to is the offset within the page. */
                from = offset & (PAGE_CACHE_SIZE - 1);
                to = PAGE_CACHE_SIZE;
                if (map_end & (PAGE_CACHE_SIZE - 1))
                        to = map_end & (PAGE_CACHE_SIZE - 1);

                page = grab_cache_page(mapping, page_index);

                /* This page can't be dirtied before we CoW it out. */
                BUG_ON(PageDirty(page));

                if (!PageUptodate(page)) {
                        ret = block_read_full_page(page, ocfs2_get_block);
                        if (ret) {
                                mlog_errno(ret);
                                goto unlock;
                        }
                        lock_page(page);
                }

                if (page_has_buffers(page)) {
                        ret = walk_page_buffers(handle, page_buffers(page),
                                                from, to, &partial,
                                                ocfs2_clear_cow_buffer);
                        if (ret) {
                                mlog_errno(ret);
                                goto unlock;
                        }
                }

                ocfs2_map_and_dirty_page(context->inode,
                                         handle, from, to,
                                         page, 0, &new_block);
                mark_page_accessed(page);
unlock:
                unlock_page(page);
                page_cache_release(page);
                page = NULL;
                offset = map_end;
                if (ret)
                        break;
        }

        return ret;
}

static int ocfs2_clear_ext_refcount(handle_t *handle,
                                    struct ocfs2_extent_tree *et,
                                    u32 cpos, u32 p_cluster, u32 len,
                                    unsigned int ext_flags,
                                    struct ocfs2_alloc_context *meta_ac,
                                    struct ocfs2_cached_dealloc_ctxt *dealloc)
{
        int ret, index;
        struct ocfs2_extent_rec replace_rec;
        struct ocfs2_path *path = NULL;
        struct ocfs2_extent_list *el;
        struct super_block *sb = ocfs2_metadata_cache_get_super(et->et_ci);
        u64 ino = ocfs2_metadata_cache_owner(et->et_ci);

        mlog(0, "inode %llu cpos %u, len %u, p_cluster %u, ext_flags %u\n",
             (unsigned long long)ino, cpos, len, p_cluster, ext_flags);

        memset(&replace_rec, 0, sizeof(replace_rec));
        replace_rec.e_cpos = cpu_to_le32(cpos);
        replace_rec.e_leaf_clusters = cpu_to_le16(len);
        replace_rec.e_blkno = cpu_to_le64(ocfs2_clusters_to_blocks(sb,
                                                                   p_cluster));
        replace_rec.e_flags = ext_flags;
        replace_rec.e_flags &= ~OCFS2_EXT_REFCOUNTED;

        path = ocfs2_new_path_from_et(et);
        if (!path) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
        }

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

        el = path_leaf_el(path);

        index = ocfs2_search_extent_list(el, cpos);
        if (index == -1 || index >= le16_to_cpu(el->l_next_free_rec)) {
                ocfs2_error(sb,
                            "Inode %llu has an extent at cpos %u which can no "
                            "longer be found.\n",
                            (unsigned long long)ino, cpos);
                ret = -EROFS;
                goto out;
        }

        ret = ocfs2_split_extent(handle, et, path, index,
                                 &replace_rec, meta_ac, dealloc);
        if (ret)
                mlog_errno(ret);

out:
        ocfs2_free_path(path);
        return ret;
}

static int ocfs2_replace_clusters(handle_t *handle,
                                  struct ocfs2_cow_context *context,
                                  u32 cpos, u32 old,
                                  u32 new, u32 len,
                                  unsigned int ext_flags)
{
        int ret;
        struct ocfs2_caching_info *ci = context->di_et.et_ci;
        u64 ino = ocfs2_metadata_cache_owner(ci);

        mlog(0, "inode %llu, cpos %u, old %u, new %u, len %u, ext_flags %u\n",
             (unsigned long long)ino, cpos, old, new, len, ext_flags);

        /*If the old clusters is unwritten, no need to duplicate. */
        if (!(ext_flags & OCFS2_EXT_UNWRITTEN)) {
                ret = ocfs2_duplicate_clusters(handle, context, cpos,
                                               old, new, len);
                if (ret) {
                        mlog_errno(ret);
                        goto out;
                }
        }

        ret = ocfs2_clear_ext_refcount(handle, &context->di_et,
                                       cpos, new, len, ext_flags,
                                       context->meta_ac, &context->dealloc);
        if (ret)
                mlog_errno(ret);
out:
        return ret;
}

static int ocfs2_cow_sync_writeback(struct super_block *sb,
                                    struct ocfs2_cow_context *context,
                                    u32 cpos, u32 num_clusters)
{
        int ret = 0;
        loff_t offset, end, map_end;
        pgoff_t page_index;
        struct page *page;

        if (ocfs2_should_order_data(context->inode))
                return 0;

        offset = ((loff_t)cpos) << OCFS2_SB(sb)->s_clustersize_bits;
        end = offset + (num_clusters << OCFS2_SB(sb)->s_clustersize_bits);

        ret = filemap_fdatawrite_range(context->inode->i_mapping,
                                       offset, end - 1);
        if (ret < 0) {
                mlog_errno(ret);
                return ret;
        }

        while (offset < end) {
                page_index = offset >> PAGE_CACHE_SHIFT;
                map_end = (page_index + 1) << PAGE_CACHE_SHIFT;
                if (map_end > end)
                        map_end = end;

                page = grab_cache_page(context->inode->i_mapping, page_index);
                BUG_ON(!page);

                wait_on_page_writeback(page);
                if (PageError(page)) {
                        ret = -EIO;
                        mlog_errno(ret);
                } else
                        mark_page_accessed(page);

                unlock_page(page);
                page_cache_release(page);
                page = NULL;
                offset = map_end;
                if (ret)
                        break;
        }

        return ret;
}

static int ocfs2_make_clusters_writable(struct super_block *sb,
                                        struct ocfs2_cow_context *context,
                                        u32 cpos, u32 p_cluster,
                                        u32 num_clusters, unsigned int e_flags)
{
        int ret, delete, index, credits =  0;
        u32 new_bit, new_len;
        unsigned int set_len;
        struct ocfs2_super *osb = OCFS2_SB(sb);
        handle_t *handle;
        struct buffer_head *ref_leaf_bh = NULL;
        struct ocfs2_refcount_rec rec;

        mlog(0, "cpos %u, p_cluster %u, num_clusters %u, e_flags %u\n",
             cpos, p_cluster, num_clusters, e_flags);

        ret = ocfs2_lock_refcount_allocators(sb, p_cluster, num_clusters,
                                             &context->di_et,
                                             context->ref_ci,
                                             context->ref_root_bh,
                                             &context->meta_ac,
                                             &context->data_ac, &credits);
        if (ret) {
                mlog_errno(ret);
                return ret;
        }

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

        while (num_clusters) {
                ret = ocfs2_get_refcount_rec(context->ref_ci,
                                             context->ref_root_bh,
                                             p_cluster, num_clusters,
                                             &rec, &index, &ref_leaf_bh);
                if (ret) {
                        mlog_errno(ret);
                        goto out_commit;
                }

                BUG_ON(!rec.r_refcount);
                set_len = min((u64)p_cluster + num_clusters,
                              le64_to_cpu(rec.r_cpos) +
                              le32_to_cpu(rec.r_clusters)) - p_cluster;

                /*
                 * There are many different situation here.
                 * 1. If refcount == 1, remove the flag and don't COW.
                 * 2. If refcount > 1, allocate clusters.
                 *    Here we may not allocate r_len once at a time, so continue
                 *    until we reach num_clusters.
                 */
                if (le32_to_cpu(rec.r_refcount) == 1) {
                        delete = 0;
                        ret = ocfs2_clear_ext_refcount(handle, &context->di_et,
                                                       cpos, p_cluster,
                                                       set_len, e_flags,
                                                       context->meta_ac,
                                                       &context->dealloc);
                        if (ret) {
                                mlog_errno(ret);
                                goto out_commit;
                        }
                } else {
                        delete = 1;

                        ret = __ocfs2_claim_clusters(osb, handle,
                                                     context->data_ac,
                                                     1, set_len,
                                                     &new_bit, &new_len);
                        if (ret) {
                                mlog_errno(ret);
                                goto out_commit;
                        }

                        ret = ocfs2_replace_clusters(handle, context,
                                                     cpos, p_cluster, new_bit,
                                                     new_len, e_flags);
                        if (ret) {
                                mlog_errno(ret);
                                goto out_commit;
                        }
                        set_len = new_len;
                }

                ret = __ocfs2_decrease_refcount(handle, context->ref_ci,
                                                context->ref_root_bh,
                                                p_cluster, set_len,
                                                context->meta_ac,
                                                &context->dealloc, delete);
                if (ret) {
                        mlog_errno(ret);
                        goto out_commit;
                }

                cpos += set_len;
                p_cluster += set_len;
                num_clusters -= set_len;
                brelse(ref_leaf_bh);
                ref_leaf_bh = NULL;
        }

        /*
         * Here we should write the new page out first if we are
         * in write-back mode.
         */
        ret = ocfs2_cow_sync_writeback(sb, context, cpos, num_clusters);
        if (ret)
                mlog_errno(ret);

out_commit:
        ocfs2_commit_trans(osb, handle);

out:
        if (context->data_ac) {
                ocfs2_free_alloc_context(context->data_ac);
                context->data_ac = NULL;
        }
        if (context->meta_ac) {
                ocfs2_free_alloc_context(context->meta_ac);
                context->meta_ac = NULL;
        }
        brelse(ref_leaf_bh);

        return ret;
}

static int ocfs2_replace_cow(struct inode *inode,
                             struct buffer_head *di_bh,
                             struct buffer_head *ref_root_bh,
                             struct ocfs2_caching_info *ref_ci,
                             u32 cow_start, u32 cow_len)
{
        int ret = 0;
        u32 p_cluster, num_clusters, start = cow_start;
        unsigned int ext_flags;
        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
        struct ocfs2_cow_context *context;

        if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb))) {
                ocfs2_error(inode->i_sb, "Inode %lu want to use refcount "
                            "tree, but the feature bit is not set in the "
                            "super block.", inode->i_ino);
                return -EROFS;
        }

        context = kzalloc(sizeof(struct ocfs2_cow_context), GFP_NOFS);
        if (!context) {
                ret = -ENOMEM;
                mlog_errno(ret);
                return ret;
        }

        context->inode = inode;
        context->cow_start = cow_start;
        context->cow_len = cow_len;
        context->ref_ci = ref_ci;
        context->ref_root_bh = ref_root_bh;

        ocfs2_init_dealloc_ctxt(&context->dealloc);
        ocfs2_init_dinode_extent_tree(&context->di_et,
                                      INODE_CACHE(inode), di_bh);

        while (cow_len) {
                ret = ocfs2_get_clusters(inode, cow_start, &p_cluster,
                                         &num_clusters, &ext_flags);
                if (ret) {
                        mlog_errno(ret);
                        break;
                }

                BUG_ON(!(ext_flags & OCFS2_EXT_REFCOUNTED));

                if (cow_len < num_clusters)
                        num_clusters = cow_len;

                ret = ocfs2_make_clusters_writable(inode->i_sb, context,
                                                   cow_start, p_cluster,
                                                   num_clusters, ext_flags);
                if (ret) {
                        mlog_errno(ret);
                        break;
                }

                cow_len -= num_clusters;
                cow_start += num_clusters;
        }


        /*
         * truncate the extent map here since no matter whether we meet with
         * any error during the action, we shouldn't trust cached extent map
         * any more.
         */
        ocfs2_extent_map_trunc(inode, start);

        if (ocfs2_dealloc_has_cluster(&context->dealloc)) {
                ocfs2_schedule_truncate_log_flush(osb, 1);
                ocfs2_run_deallocs(osb, &context->dealloc);
        }

        kfree(context);
        return ret;
}

/*
 * Starting at cpos, try to CoW write_len clusters.
 * This will stop when it runs into a hole or an unrefcounted extent.
 */
static int ocfs2_refcount_cow_hunk(struct inode *inode,
                                   struct buffer_head *di_bh,
                                   u32 cpos, u32 write_len)
{
        int ret;
        u32 cow_start = 0, cow_len = 0;
        struct ocfs2_inode_info *oi = OCFS2_I(inode);
        struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
        struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
        struct buffer_head *ref_root_bh = NULL;
        struct ocfs2_refcount_tree *ref_tree;

        BUG_ON(!(oi->ip_dyn_features & OCFS2_HAS_REFCOUNT_FL));

        ret = ocfs2_refcount_cal_cow_clusters(inode, di_bh, cpos, write_len,
                                              &cow_start, &cow_len);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }
        mlog(0, "CoW inode %lu, cpos %u, write_len %u, cow_start %u, "
             "cow_len %u\n", inode->i_ino,
             cpos, write_len, cow_start, cow_len);

        BUG_ON(cow_len == 0);

        ret = ocfs2_lock_refcount_tree(osb, le64_to_cpu(di->i_refcount_loc),
                                       1, &ref_tree, &ref_root_bh);
        if (ret) {
                mlog_errno(ret);
                goto out;
        }

        ret = ocfs2_replace_cow(inode, di_bh, ref_root_bh, &ref_tree->rf_ci,
                                cow_start, cow_len);
        if (ret)
                mlog_errno(ret);

        ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
        brelse(ref_root_bh);
out:
        return ret;
}

/*
 * CoW any and all clusters between cpos and cpos+write_len.
 * If this returns successfully, all clusters between cpos and
 * cpos+write_len are safe to modify.
 */
int ocfs2_refcount_cow(struct inode *inode,
                       struct buffer_head *di_bh,
                       u32 cpos, u32 write_len)
{
        int ret = 0;
        u32 p_cluster, num_clusters;
        unsigned int ext_flags;

        while (write_len) {
                ret = ocfs2_get_clusters(inode, cpos, &p_cluster,
                                         &num_clusters, &ext_flags);
                if (ret) {
                        mlog_errno(ret);
                        break;
                }

                if (write_len < num_clusters)
                        num_clusters = write_len;

                if (ext_flags & OCFS2_EXT_REFCOUNTED) {
                        ret = ocfs2_refcount_cow_hunk(inode, di_bh, cpos,
                                                      num_clusters);
                        if (ret) {
                                mlog_errno(ret);
                                break;
                        }
                }

                write_len -= num_clusters;
                cpos += num_clusters;
        }

        return ret;
}