[EXT2]

[reactos.git] / reactos / drivers / filesystems / ext2 / src / ext4 / ext4_extents.c

/*
 * 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.
 *
 * You should have received a copy of the GNU General Public Licens
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
 */

#include "ext2fs.h"
#include <linux/ext4.h>

#ifdef _MSC_VER
#pragma warning(push)
#pragma warning(disable: 4018)
#pragma warning(disable: 4242)
#pragma warning(disable: 4244)
#endif

/*
 * used by extent splitting.
 */
#define EXT4_EXT_MAY_ZEROOUT    0x1  /* safe to zeroout if split fails \
                                        due to ENOSPC */
#define EXT4_EXT_MARK_UNWRIT1   0x2  /* mark first half unwritten */
#define EXT4_EXT_MARK_UNWRIT2   0x4  /* mark second half unwritten */

#define EXT4_EXT_DATA_VALID1    0x8  /* first half contains valid data */
#define EXT4_EXT_DATA_VALID2    0x10 /* second half contains valid data */

#define CONFIG_EXTENT_TEST
#ifdef CONFIG_EXTENT_TEST

#define ext4_mark_inode_dirty(icb, handle, n) ext3_mark_inode_dirty(icb, n)
static inline ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
{
        PEXT2_VCB Vcb;
        Vcb = inode->i_sb->s_priv;
        return (inode->i_ino - 1) / BLOCKS_PER_GROUP;
}

static ext4_fsblk_t ext4_new_meta_blocks(void *icb, handle_t *handle, struct inode *inode,
                ext4_fsblk_t goal,
                unsigned int flags,
                unsigned long *count, int *errp)
{
        NTSTATUS status;
        ULONG blockcnt = (count)?*count:1;
        ULONG block = 0;

        status = Ext2NewBlock((PEXT2_IRP_CONTEXT)icb,
                        inode->i_sb->s_priv,
                        0, goal,
                        &block,
                        &blockcnt);
        if (count)
                *count = blockcnt;

        if (!NT_SUCCESS(status)) {
                *errp = Ext2LinuxError(status);
                return 0;
        }
        inode->i_blocks += (blockcnt * (inode->i_sb->s_blocksize >> 9));
        return block;
}

static void ext4_free_blocks(void *icb, handle_t *handle, struct inode *inode, void *fake,
                ext4_fsblk_t block, int count, int flags)
{
        Ext2FreeBlock((PEXT2_IRP_CONTEXT)icb, inode->i_sb->s_priv, block, count);
        inode->i_blocks -= count * (inode->i_sb->s_blocksize >> 9);
        return;
}

static inline void ext_debug(char *str, ...)
{
}
#if TRUE
#define EXT4_ERROR_INODE(inode, str, ...) do {                      \
            DbgPrint("inode[%p]: " str "\n", inode, ##__VA_ARGS__); \
        } while(0)
#else
#define EXT4_ERROR_INODE
#endif

#define ext4_std_error(s, err)
#define assert ASSERT

#endif

/*
 * Return the right sibling of a tree node(either leaf or indexes node)
 */

#define EXT_MAX_BLOCKS 0xffffffff


static inline int ext4_ext_space_block(struct inode *inode, int check)
{
        int size;

        size = (inode->i_sb->s_blocksize - sizeof(struct ext4_extent_header))
                / sizeof(struct ext4_extent);
#ifdef AGGRESSIVE_TEST
        if (!check && size > 6)
                size = 6;
#endif
        return size;
}

static inline int ext4_ext_space_block_idx(struct inode *inode, int check)
{
        int size;

        size = (inode->i_sb->s_blocksize - sizeof(struct ext4_extent_header))
                / sizeof(struct ext4_extent_idx);
#ifdef AGGRESSIVE_TEST
        if (!check && size > 5)
                size = 5;
#endif
        return size;
}

static inline int ext4_ext_space_root(struct inode *inode, int check)
{
        int size;

        size = sizeof(EXT4_I(inode)->i_block);
        size -= sizeof(struct ext4_extent_header);
        size /= sizeof(struct ext4_extent);
#ifdef AGGRESSIVE_TEST
        if (!check && size > 3)
                size = 3;
#endif
        return size;
}

static inline int ext4_ext_space_root_idx(struct inode *inode, int check)
{
        int size;

        size = sizeof(EXT4_I(inode)->i_block);
        size -= sizeof(struct ext4_extent_header);
        size /= sizeof(struct ext4_extent_idx);
#ifdef AGGRESSIVE_TEST
        if (!check && size > 4)
                size = 4;
#endif
        return size;
}

static int
ext4_ext_max_entries(struct inode *inode, int depth)
{
        int max;

        if (depth == ext_depth(inode)) {
                if (depth == 0)
                        max = ext4_ext_space_root(inode, 1);
                else
                        max = ext4_ext_space_root_idx(inode, 1);
        } else {
                if (depth == 0)
                        max = ext4_ext_space_block(inode, 1);
                else
                        max = ext4_ext_space_block_idx(inode, 1);
        }

        return max;
}

static int __ext4_ext_check(const char *function, unsigned int line,
                struct inode *inode,
                struct ext4_extent_header *eh, int depth,
                ext4_fsblk_t pblk);

/*
 * read_extent_tree_block:
 * Get a buffer_head by extents_bread, and read fresh data from the storage.
 */
static struct buffer_head *
__read_extent_tree_block(const char *function, unsigned int line,
                struct inode *inode, ext4_fsblk_t pblk, int depth,
                int flags)
{
        struct buffer_head              *bh;
        int                             err;

        bh = extents_bread(inode->i_sb, pblk);
        if (!bh)
                return ERR_PTR(-ENOMEM);

        if (!buffer_uptodate(bh)) {
                err = -EIO;
                goto errout;
        }
        if (buffer_verified(bh))
                return bh;
        err = __ext4_ext_check(function, line, inode,
                        ext_block_hdr(bh), depth, pblk);
        if (err)
                goto errout;
        set_buffer_verified(bh);
        return bh;
errout:
        extents_brelse(bh);
        return ERR_PTR(err);

}

#define read_extent_tree_block(inode, pblk, depth, flags)               \
        __read_extent_tree_block("", __LINE__, (inode), (pblk),   \
                        (depth), (flags))

#define ext4_ext_check(inode, eh, depth, pblk)                  \
        __ext4_ext_check("", __LINE__, (inode), (eh), (depth), (pblk))

int ext4_ext_check_inode(struct inode *inode)
{
        return ext4_ext_check(inode, ext_inode_hdr(inode), ext_depth(inode), 0);
}

static uint32_t ext4_ext_block_csum(struct inode *inode,
                struct ext4_extent_header *eh)
{
        /*return ext4_crc32c(inode->i_csum, eh, EXT4_EXTENT_TAIL_OFFSET(eh));*/
        return 0;
}

static void ext4_extent_block_csum_set(struct inode *inode,
                struct ext4_extent_header *eh)
{
        struct ext4_extent_tail *tail;

        tail = find_ext4_extent_tail(eh);
        tail->et_checksum = ext4_ext_block_csum(
                        inode, eh);
}

static int ext4_split_extent_at(void *icb,
                             handle_t *handle,
                             struct inode *inode,
                             struct ext4_ext_path **ppath,
                             ext4_lblk_t split,
                             int split_flag,
                             int flags);

static inline int
ext4_force_split_extent_at(void *icb, handle_t *handle, struct inode *inode,
                struct ext4_ext_path **ppath, ext4_lblk_t lblk,
                int nofail)
{
        struct ext4_ext_path *path = *ppath;
        int unwritten = ext4_ext_is_unwritten(path[path->p_depth].p_ext);

        return ext4_split_extent_at(icb, handle, inode, ppath, lblk, unwritten ?
                        EXT4_EXT_MARK_UNWRIT1|EXT4_EXT_MARK_UNWRIT2 : 0,
                        EXT4_EX_NOCACHE | EXT4_GET_BLOCKS_PRE_IO |
                        (nofail ? EXT4_GET_BLOCKS_METADATA_NOFAIL:0));
}

/*
 * could return:
 *  - EROFS
 *  - ENOMEM
 */

static int ext4_ext_get_access(void *icb, handle_t *handle, struct inode *inode,
                struct ext4_ext_path *path)
{
        if (path->p_bh) {
                /* path points to block */

                return ext4_journal_get_write_access(icb, handle, path->p_bh);

        }
        /* path points to leaf/index in inode body */
        /* we use in-core data, no need to protect them */
        return 0;
}


static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
                struct ext4_ext_path *path,
                ext4_lblk_t block)
{
        if (path) {
                int depth = path->p_depth;
                struct ext4_extent *ex;

                /*
                 * Try to predict block placement assuming that we are
                 * filling in a file which will eventually be
                 * non-sparse --- i.e., in the case of libbfd writing
                 * an ELF object sections out-of-order but in a way
                 * the eventually results in a contiguous object or
                 * executable file, or some database extending a table
                 * space file.  However, this is actually somewhat
                 * non-ideal if we are writing a sparse file such as
                 * qemu or KVM writing a raw image file that is going
                 * to stay fairly sparse, since it will end up
                 * fragmenting the file system's free space.  Maybe we
                 * should have some hueristics or some way to allow
                 * userspace to pass a hint to file system,
                 * especially if the latter case turns out to be
                 * common.
                 */
                ex = path[depth].p_ext;
                if (ex) {
                        ext4_fsblk_t ext_pblk = ext4_ext_pblock(ex);
                        ext4_lblk_t ext_block = le32_to_cpu(ex->ee_block);

                        if (block > ext_block)
                                return ext_pblk + (block - ext_block);
                        else
                                return ext_pblk - (ext_block - block);
                }

                /* it looks like index is empty;
                 * try to find starting block from index itself */
                if (path[depth].p_bh)
                        return path[depth].p_bh->b_blocknr;
        }

        /* OK. use inode's group */
        return ext4_inode_to_goal_block(inode);
}

/*
 * Allocation for a meta data block
 */
static ext4_fsblk_t
ext4_ext_new_meta_block(void *icb, handle_t *handle, struct inode *inode,
                struct ext4_ext_path *path,
                struct ext4_extent *ex, int *err, unsigned int flags)
{
        ext4_fsblk_t goal, newblock;

        goal = ext4_ext_find_goal(inode, path, le32_to_cpu(ex->ee_block));
        newblock = ext4_new_meta_blocks(icb, handle, inode, goal, flags,
                        NULL, err);
        return newblock;
}

int __ext4_ext_dirty(const char *where, unsigned int line,
                void *icb, handle_t *handle,
                struct inode *inode,
                struct ext4_ext_path *path)
{
        int err;

        if (path->p_bh) {
                ext4_extent_block_csum_set(inode, ext_block_hdr(path->p_bh));
                /* path points to block */
                err = __ext4_handle_dirty_metadata(where, line, icb, handle, inode, path->p_bh);
        } else {
                /* path points to leaf/index in inode body */
                err = ext4_mark_inode_dirty(icb, handle, inode);
        }
        return err;
}

void ext4_ext_drop_refs(struct ext4_ext_path *path)
{
        int depth, i;

        if (!path)
                return;
        depth = path->p_depth;
        for (i = 0; i <= depth; i++, path++)
                if (path->p_bh) {
                        extents_brelse(path->p_bh);
                        path->p_bh = NULL;
                }
}

/*
 * Check that whether the basic information inside the extent header
 * is correct or not.
 */
static int __ext4_ext_check(const char *function, unsigned int line,
                struct inode *inode,
                struct ext4_extent_header *eh, int depth,
                ext4_fsblk_t pblk)
{
        struct ext4_extent_tail *tail;
        const char *error_msg;
#ifndef __REACTOS__
        int max = 0;
#endif
        if (eh->eh_magic != EXT4_EXT_MAGIC) {
                error_msg = "invalid magic";
                goto corrupted;
        }
        if (le16_to_cpu(eh->eh_depth) != depth) {
                error_msg = "unexpected eh_depth";
                goto corrupted;
        }
        if (eh->eh_max == 0) {
                error_msg = "invalid eh_max";
                goto corrupted;
        }
        if (eh->eh_entries > eh->eh_max) {
                error_msg = "invalid eh_entries";
                goto corrupted;
        }

        tail = find_ext4_extent_tail(eh);
        if (tail->et_checksum != ext4_ext_block_csum(inode, eh)) {
                ext_debug("Warning: extent checksum damaged? tail->et_checksum = "
                                "%lu, ext4_ext_block_csum = %lu\n",
                                tail->et_checksum, ext4_ext_block_csum(inode, eh));
        }

        return 0;

corrupted:
        ext_debug("corrupted! %s\n", error_msg);
        return -EIO;
}

/*
 * ext4_ext_binsearch_idx:
 * binary search for the closest index of the given block
 * the header must be checked before calling this
 */
static void
ext4_ext_binsearch_idx(struct inode *inode,
                struct ext4_ext_path *path, ext4_lblk_t block)
{
        struct ext4_extent_header *eh = path->p_hdr;
        struct ext4_extent_idx *r, *l, *m;

        ext_debug("binsearch for %u(idx):  ", block);

        l = EXT_FIRST_INDEX(eh) + 1;
        r = EXT_LAST_INDEX(eh);
        while (l <= r) {
                m = l + (r - l) / 2;
                if (block < (m->ei_block))
                        r = m - 1;
                else
                        l = m + 1;
                ext_debug("%p(%u):%p(%u):%p(%u) ", l, (l->ei_block),
                                m, (m->ei_block),
                                r, (r->ei_block));
        }

        path->p_idx = l - 1;
        ext_debug("  -> %u->%lld ", (path->p_idx->ei_block),
                        ext4_idx_pblock(path->p_idx));

#ifdef CHECK_BINSEARCH
        {
                struct ext4_extent_idx *chix, *ix;
                int k;

                chix = ix = EXT_FIRST_INDEX(eh);
                for (k = 0; k < (eh->eh_entries); k++, ix++) {
                        if (k != 0 &&
                                        (ix->ei_block) <= (ix[-1].ei_block)) {
                                printk(KERN_DEBUG "k=%d, ix=0x%p, "
                                                "first=0x%p\n", k,
                                                ix, EXT_FIRST_INDEX(eh));
                                printk(KERN_DEBUG "%u <= %u\n",
                                                (ix->ei_block),
                                                (ix[-1].ei_block));
                        }
                        BUG_ON(k && (ix->ei_block)
                                        <= (ix[-1].ei_block));
                        if (block < (ix->ei_block))
                                break;
                        chix = ix;
                }
                BUG_ON(chix != path->p_idx);
        }
#endif

}

/*
 * ext4_ext_binsearch:
 * binary search for closest extent of the given block
 * the header must be checked before calling this
 */
static void
ext4_ext_binsearch(struct inode *inode,
                struct ext4_ext_path *path, ext4_lblk_t block)
{
        struct ext4_extent_header *eh = path->p_hdr;
        struct ext4_extent *r, *l, *m;

        if (eh->eh_entries == 0) {
                /*
                 * this leaf is empty:
                 * we get such a leaf in split/add case
                 */
                return;
        }

        ext_debug("binsearch for %u:  ", block);

        l = EXT_FIRST_EXTENT(eh) + 1;
        r = EXT_LAST_EXTENT(eh);

        while (l <= r) {
                m = l + (r - l) / 2;
                if (block < m->ee_block)
                        r = m - 1;
                else
                        l = m + 1;
                ext_debug("%p(%u):%p(%u):%p(%u) ", l, l->ee_block,
                                m, (m->ee_block),
                                r, (r->ee_block));
        }

        path->p_ext = l - 1;
        ext_debug("  -> %d:%llu:[%d]%d ",
                        (path->p_ext->ee_block),
                        ext4_ext_pblock(path->p_ext),
                        ext4_ext_is_unwritten(path->p_ext),
                        ext4_ext_get_actual_len(path->p_ext));

#ifdef CHECK_BINSEARCH
        {
                struct ext4_extent *chex, *ex;
                int k;

                chex = ex = EXT_FIRST_EXTENT(eh);
                for (k = 0; k < le16_to_cpu(eh->eh_entries); k++, ex++) {
                        BUG_ON(k && (ex->ee_block)
                                        <= (ex[-1].ee_block));
                        if (block < (ex->ee_block))
                                break;
                        chex = ex;
                }
                BUG_ON(chex != path->p_ext);
        }
#endif

}

#ifdef EXT_DEBUG
static void ext4_ext_show_path(struct inode *inode, struct ext4_ext_path *path)
{
        int k, l = path->p_depth;

        ext_debug("path:");
        for (k = 0; k <= l; k++, path++) {
                if (path->p_idx) {
                        ext_debug("  %d->%llu", le32_to_cpu(path->p_idx->ei_block),
                                        ext4_idx_pblock(path->p_idx));
                } else if (path->p_ext) {
                        ext_debug("  %d:[%d]%d:%llu ",
                                        le32_to_cpu(path->p_ext->ee_block),
                                        ext4_ext_is_unwritten(path->p_ext),
                                        ext4_ext_get_actual_len(path->p_ext),
                                        ext4_ext_pblock(path->p_ext));
                } else
                        ext_debug("  []");
        }
        ext_debug("\n");
}

static void ext4_ext_show_leaf(struct inode *inode, struct ext4_ext_path *path)
{
        int depth = ext_depth(inode);
        struct ext4_extent_header *eh;
        struct ext4_extent *ex;
        int i;

        if (!path)
                return;

        eh = path[depth].p_hdr;
        ex = EXT_FIRST_EXTENT(eh);

        ext_debug("Displaying leaf extents for inode %lu\n", inode->i_ino);

        for (i = 0; i < le16_to_cpu(eh->eh_entries); i++, ex++) {
                ext_debug("%d:[%d]%d:%llu ", le32_to_cpu(ex->ee_block),
                                ext4_ext_is_unwritten(ex),
                                ext4_ext_get_actual_len(ex), ext4_ext_pblock(ex));
        }
        ext_debug("\n");
}

static void ext4_ext_show_move(struct inode *inode, struct ext4_ext_path *path,
                ext4_fsblk_t newblock, int level)
{
        int depth = ext_depth(inode);
        struct ext4_extent *ex;

        if (depth != level) {
                struct ext4_extent_idx *idx;
                idx = path[level].p_idx;
                while (idx <= EXT_MAX_INDEX(path[level].p_hdr)) {
                        ext_debug("%d: move %d:%llu in new index %llu\n", level,
                                        le32_to_cpu(idx->ei_block),
                                        ext4_idx_pblock(idx),
                                        newblock);
                        idx++;
                }

                return;
        }

        ex = path[depth].p_ext;
        while (ex <= EXT_MAX_EXTENT(path[depth].p_hdr)) {
                ext_debug("move %d:%llu:[%d]%d in new leaf %llu\n",
                                le32_to_cpu(ex->ee_block),
                                ext4_ext_pblock(ex),
                                ext4_ext_is_unwritten(ex),
                                ext4_ext_get_actual_len(ex),
                                newblock);
                ex++;
        }
}

#else
#define ext4_ext_show_path(inode, path)
#define ext4_ext_show_leaf(inode, path)
#define ext4_ext_show_move(inode, path, newblock, level)
#endif

struct ext4_ext_path *
ext4_find_extent(struct inode *inode, ext4_lblk_t block,
                struct ext4_ext_path **orig_path, int flags)
{
        struct ext4_extent_header *eh;
        struct buffer_head *bh;
        struct ext4_ext_path *path = orig_path ? *orig_path : NULL;
        short int depth, i, ppos = 0;
        int ret;

        eh = ext_inode_hdr(inode);
        depth = ext_depth(inode);

        if (path) {
                ext4_ext_drop_refs(path);
                if (depth > path[0].p_maxdepth) {
                        kfree(path);
                        *orig_path = path = NULL;
                }
        }
        if (!path) {
                /* account possible depth increase */
                path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 2),
                                GFP_NOFS);
                if (unlikely(!path))
                        return ERR_PTR(-ENOMEM);
                path[0].p_maxdepth = depth + 1;
        }
        path[0].p_hdr = eh;
        path[0].p_bh = NULL;

        i = depth;
        /* walk through the tree */
        while (i) {
                ext_debug("depth %d: num %d, max %d\n",
                                ppos, le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));

                ext4_ext_binsearch_idx(inode, path + ppos, block);
                path[ppos].p_block = ext4_idx_pblock(path[ppos].p_idx);
                path[ppos].p_depth = i;
                path[ppos].p_ext = NULL;

                bh = read_extent_tree_block(inode, path[ppos].p_block, --i,
                                flags);
                if (unlikely(IS_ERR(bh))) {
                        ret = PTR_ERR(bh);
                        goto err;
                }

                eh = ext_block_hdr(bh);
                ppos++;
                if (unlikely(ppos > depth)) {
                        extents_brelse(bh);
                        EXT4_ERROR_INODE(inode,
                                        "ppos %d > depth %d", ppos, depth);
                        ret = -EIO;
                        goto err;
                }
                path[ppos].p_bh = bh;
                path[ppos].p_hdr = eh;
        }

        path[ppos].p_depth = i;
        path[ppos].p_ext = NULL;
        path[ppos].p_idx = NULL;

        /* find extent */
        ext4_ext_binsearch(inode, path + ppos, block);
        /* if not an empty leaf */
        if (path[ppos].p_ext)
                path[ppos].p_block = ext4_ext_pblock(path[ppos].p_ext);

        ext4_ext_show_path(inode, path);

        return path;

err:
        ext4_ext_drop_refs(path);
        if (path) {
                kfree(path);
                if (orig_path)
                        *orig_path = NULL;
        }
        return ERR_PTR(ret);
}

/*
 * ext4_ext_insert_index:
 * insert new index [@logical;@ptr] into the block at @curp;
 * check where to insert: before @curp or after @curp
 */
static int ext4_ext_insert_index(void *icb, handle_t *handle, struct inode *inode,
                struct ext4_ext_path *curp,
                int logical, ext4_fsblk_t ptr)
{
        struct ext4_extent_idx *ix;
        int len, err;

        err = ext4_ext_get_access(icb, handle, inode, curp);
        if (err)
                return err;

        if (unlikely(logical == le32_to_cpu(curp->p_idx->ei_block))) {
                EXT4_ERROR_INODE(inode,
                                "logical %d == ei_block %d!",
                                logical, le32_to_cpu(curp->p_idx->ei_block));
                return -EIO;
        }

        if (unlikely(le16_to_cpu(curp->p_hdr->eh_entries)
                                >= le16_to_cpu(curp->p_hdr->eh_max))) {
                EXT4_ERROR_INODE(inode,
                                "eh_entries %d >= eh_max %d!",
                                le16_to_cpu(curp->p_hdr->eh_entries),
                                le16_to_cpu(curp->p_hdr->eh_max));
                return -EIO;
        }

        if (logical > le32_to_cpu(curp->p_idx->ei_block)) {
                /* insert after */
                ext_debug("insert new index %d after: %llu\n", logical, ptr);
                ix = curp->p_idx + 1;
        } else {
                /* insert before */
                ext_debug("insert new index %d before: %llu\n", logical, ptr);
                ix = curp->p_idx;
        }

        len = EXT_LAST_INDEX(curp->p_hdr) - ix + 1;
        BUG_ON(len < 0);
        if (len > 0) {
                ext_debug("insert new index %d: "
                                "move %d indices from 0x%p to 0x%p\n",
                                logical, len, ix, ix + 1);
                memmove(ix + 1, ix, len * sizeof(struct ext4_extent_idx));
        }

        if (unlikely(ix > EXT_MAX_INDEX(curp->p_hdr))) {
                EXT4_ERROR_INODE(inode, "ix > EXT_MAX_INDEX!");
                return -EIO;
        }

        ix->ei_block = cpu_to_le32(logical);
        ext4_idx_store_pblock(ix, ptr);
        le16_add_cpu(&curp->p_hdr->eh_entries, 1);

        if (unlikely(ix > EXT_LAST_INDEX(curp->p_hdr))) {
                EXT4_ERROR_INODE(inode, "ix > EXT_LAST_INDEX!");
                return -EIO;
        }

        err = ext4_ext_dirty(icb, handle, inode, curp);
        ext4_std_error(inode->i_sb, err);

        return err;
}

/*
 * ext4_ext_split:
 * inserts new subtree into the path, using free index entry
 * at depth @at:
 * - allocates all needed blocks (new leaf and all intermediate index blocks)
 * - makes decision where to split
 * - moves remaining extents and index entries (right to the split point)
 *   into the newly allocated blocks
 * - initializes subtree
 */
static int ext4_ext_split(void *icb, handle_t *handle, struct inode *inode,
                unsigned int flags,
                struct ext4_ext_path *path,
                struct ext4_extent *newext, int at)
{
        struct buffer_head *bh = NULL;
        int depth = ext_depth(inode);
        struct ext4_extent_header *neh;
        struct ext4_extent_idx *fidx;
        int i = at, k, m, a;
        ext4_fsblk_t newblock, oldblock;
        __le32 border;
        ext4_fsblk_t *ablocks = NULL; /* array of allocated blocks */
        int err = 0;

        /* make decision: where to split? */
        /* FIXME: now decision is simplest: at current extent */

        /* if current leaf will be split, then we should use
         * border from split point */
        if (unlikely(path[depth].p_ext > EXT_MAX_EXTENT(path[depth].p_hdr))) {
                EXT4_ERROR_INODE(inode, "p_ext > EXT_MAX_EXTENT!");
                return -EIO;
        }
        if (path[depth].p_ext != EXT_MAX_EXTENT(path[depth].p_hdr)) {
                border = path[depth].p_ext[1].ee_block;
                ext_debug("leaf will be split."
                                " next leaf starts at %d\n",
                                le32_to_cpu(border));
        } else {
                border = newext->ee_block;
                ext_debug("leaf will be added."
                                " next leaf starts at %d\n",
                                le32_to_cpu(border));
        }

        /*
         * If error occurs, then we break processing
         * and mark filesystem read-only. index won't
         * be inserted and tree will be in consistent
         * state. Next mount will repair buffers too.
         */

        /*
         * Get array to track all allocated blocks.
         * We need this to handle errors and free blocks
         * upon them.
         */
        ablocks = kzalloc(sizeof(ext4_fsblk_t) * depth, GFP_NOFS);
        if (!ablocks)
                return -ENOMEM;

        /* allocate all needed blocks */
        ext_debug("allocate %d blocks for indexes/leaf\n", depth - at);
        for (a = 0; a < depth - at; a++) {
                newblock = ext4_ext_new_meta_block(icb, handle, inode, path,
                                newext, &err, flags);
                if (newblock == 0)
                        goto cleanup;
                ablocks[a] = newblock;
        }

        /* initialize new leaf */
        newblock = ablocks[--a];
        if (unlikely(newblock == 0)) {
                EXT4_ERROR_INODE(inode, "newblock == 0!");
                err = -EIO;
                goto cleanup;
        }
        bh = extents_bwrite(inode->i_sb, newblock);
        if (unlikely(!bh)) {
                err = -ENOMEM;
                goto cleanup;
        }

        err = ext4_journal_get_create_access(icb, handle, bh);
        if (err)
                goto cleanup;

        neh = ext_block_hdr(bh);
        neh->eh_entries = 0;
        neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));
        neh->eh_magic = EXT4_EXT_MAGIC;
        neh->eh_depth = 0;

        /* move remainder of path[depth] to the new leaf */
        if (unlikely(path[depth].p_hdr->eh_entries !=
                                path[depth].p_hdr->eh_max)) {
                EXT4_ERROR_INODE(inode, "eh_entries %d != eh_max %d!",
                                path[depth].p_hdr->eh_entries,
                                path[depth].p_hdr->eh_max);
                err = -EIO;
                goto cleanup;
        }
        /* start copy from next extent */
        m = EXT_MAX_EXTENT(path[depth].p_hdr) - path[depth].p_ext++;
        ext4_ext_show_move(inode, path, newblock, depth);
        if (m) {
                struct ext4_extent *ex;
                ex = EXT_FIRST_EXTENT(neh);
                memmove(ex, path[depth].p_ext, sizeof(struct ext4_extent) * m);
                le16_add_cpu(&neh->eh_entries, m);
        }

        ext4_extent_block_csum_set(inode, neh);
        set_buffer_uptodate(bh);

        err = ext4_handle_dirty_metadata(icb, handle, inode, bh);
        if (err)
                goto cleanup;
        extents_brelse(bh);
        bh = NULL;

        /* correct old leaf */
        if (m) {
                err = ext4_ext_get_access(icb, handle, inode, path + depth);
                if (err)
                        goto cleanup;
                le16_add_cpu(&path[depth].p_hdr->eh_entries, -m);
                err = ext4_ext_dirty(icb, handle, inode, path + depth);
                if (err)
                        goto cleanup;

        }

        /* create intermediate indexes */
        k = depth - at - 1;
        if (unlikely(k < 0)) {
                EXT4_ERROR_INODE(inode, "k %d < 0!", k);
                err = -EIO;
                goto cleanup;
        }
        if (k)
                ext_debug("create %d intermediate indices\n", k);
        /* insert new index into current index block */
        /* current depth stored in i var */
        i = depth - 1;
        while (k--) {
                oldblock = newblock;
                newblock = ablocks[--a];
                bh = extents_bwrite(inode->i_sb, newblock);
                if (unlikely(!bh)) {
                        err = -ENOMEM;
                        goto cleanup;
                }

                err = ext4_journal_get_create_access(icb, handle, bh);
                if (err)
                        goto cleanup;

                neh = ext_block_hdr(bh);
                neh->eh_entries = cpu_to_le16(1);
                neh->eh_magic = EXT4_EXT_MAGIC;
                neh->eh_max = cpu_to_le16(ext4_ext_space_block_idx(inode, 0));
                neh->eh_depth = cpu_to_le16(depth - i);
                fidx = EXT_FIRST_INDEX(neh);
                fidx->ei_block = border;
                ext4_idx_store_pblock(fidx, oldblock);

                ext_debug("int.index at %d (block %llu): %u -> %llu\n",
                                i, newblock, le32_to_cpu(border), oldblock);

                /* move remainder of path[i] to the new index block */
                if (unlikely(EXT_MAX_INDEX(path[i].p_hdr) !=
                                        EXT_LAST_INDEX(path[i].p_hdr))) {
                        EXT4_ERROR_INODE(inode,
                                        "EXT_MAX_INDEX != EXT_LAST_INDEX ee_block %d!",
                                        le32_to_cpu(path[i].p_ext->ee_block));
                        err = -EIO;
                        goto cleanup;
                }
                /* start copy indexes */
                m = EXT_MAX_INDEX(path[i].p_hdr) - path[i].p_idx++;
                ext_debug("cur 0x%p, last 0x%p\n", path[i].p_idx,
                                EXT_MAX_INDEX(path[i].p_hdr));
                ext4_ext_show_move(inode, path, newblock, i);
                if (m) {
                        memmove(++fidx, path[i].p_idx,
                                        sizeof(struct ext4_extent_idx) * m);
                        le16_add_cpu(&neh->eh_entries, m);
                }
                ext4_extent_block_csum_set(inode, neh);
                set_buffer_uptodate(bh);

                err = ext4_handle_dirty_metadata(icb, handle, inode, bh);
                if (err)
                        goto cleanup;
                extents_brelse(bh);
                bh = NULL;

                /* correct old index */
                if (m) {
                        err = ext4_ext_get_access(icb, handle, inode, path + i);
                        if (err)
                                goto cleanup;
                        le16_add_cpu(&path[i].p_hdr->eh_entries, -m);
                        err = ext4_ext_dirty(icb, handle, inode, path + i);
                        if (err)
                                goto cleanup;
                }

                i--;
        }

        /* insert new index */
        err = ext4_ext_insert_index(icb, handle, inode, path + at,
                        le32_to_cpu(border), newblock);

cleanup:
        if (bh)
                extents_brelse(bh);

        if (err) {
                /* free all allocated blocks in error case */
                for (i = 0; i < depth; i++) {
                        if (!ablocks[i])
                                continue;
                        ext4_free_blocks(icb, handle, inode, NULL, ablocks[i], 1,
                                        EXT4_FREE_BLOCKS_METADATA);
                }
        }
        kfree(ablocks);

        return err;
}

/*
 * ext4_ext_grow_indepth:
 * implements tree growing procedure:
 * - allocates new block
 * - moves top-level data (index block or leaf) into the new block
 * - initializes new top-level, creating index that points to the
 *   just created block
 */
static int ext4_ext_grow_indepth(void *icb, handle_t *handle, struct inode *inode,
                unsigned int flags)
{
        struct ext4_extent_header *neh;
        struct buffer_head *bh;
        ext4_fsblk_t newblock, goal = 0;
        int err = 0;

        /* Try to prepend new index to old one */
        if (ext_depth(inode))
                goal = ext4_idx_pblock(EXT_FIRST_INDEX(ext_inode_hdr(inode)));
        goal = ext4_inode_to_goal_block(inode);
        newblock = ext4_new_meta_blocks(icb, handle, inode, goal, flags,
                        NULL, &err);
        if (newblock == 0)
                return err;

        bh = extents_bwrite(inode->i_sb, newblock);
        if (!bh)
                return -ENOMEM;

        err = ext4_journal_get_create_access(icb, handle, bh);
        if (err)
                goto out;

        /* move top-level index/leaf into new block */
        memmove(bh->b_data, EXT4_I(inode)->i_block,
                        sizeof(EXT4_I(inode)->i_block));

        /* set size of new block */
        neh = ext_block_hdr(bh);
        /* old root could have indexes or leaves
         * so calculate e_max right way */
        if (ext_depth(inode))
                neh->eh_max = (ext4_ext_space_block_idx(inode, 0));
        else
                neh->eh_max = (ext4_ext_space_block(inode, 0));
        neh->eh_magic = EXT4_EXT_MAGIC;
        ext4_extent_block_csum_set(inode, neh);
        set_buffer_uptodate(bh);

        err = ext4_handle_dirty_metadata(icb, handle, inode, bh);
        if (err)
                goto out;

        /* Update top-level index: num,max,pointer */
        neh = ext_inode_hdr(inode);
        neh->eh_entries = (1);
        ext4_idx_store_pblock(EXT_FIRST_INDEX(neh), newblock);
        if (neh->eh_depth == 0) {
                /* Root extent block becomes index block */
                neh->eh_max = (ext4_ext_space_root_idx(inode, 0));
                EXT_FIRST_INDEX(neh)->ei_block =
                        EXT_FIRST_EXTENT(neh)->ee_block;
        }
        ext_debug("new root: num %d(%d), lblock %d, ptr %llu\n",
                        (neh->eh_entries), (neh->eh_max),
                        (EXT_FIRST_INDEX(neh)->ei_block),
                        ext4_idx_pblock(EXT_FIRST_INDEX(neh)));

        le16_add_cpu(&neh->eh_depth, 1);
        ext4_mark_inode_dirty(icb, handle, inode);
out:
        extents_brelse(bh);

        return err;
}

/*
 * ext4_ext_create_new_leaf:
 * finds empty index and adds new leaf.
 * if no free index is found, then it requests in-depth growing.
 */
static int ext4_ext_create_new_leaf(void *icb, handle_t *handle, struct inode *inode,
                unsigned int mb_flags,
                unsigned int gb_flags,
                struct ext4_ext_path **ppath,
                struct ext4_extent *newext)
{
        struct ext4_ext_path *path = *ppath;
        struct ext4_ext_path *curp;
        int depth, i, err = 0;

repeat:
        i = depth = ext_depth(inode);

        /* walk up to the tree and look for free index entry */
        curp = path + depth;
        while (i > 0 && !EXT_HAS_FREE_INDEX(curp)) {
                i--;
                curp--;
        }

        /* we use already allocated block for index block,
         * so subsequent data blocks should be contiguous */
        if (EXT_HAS_FREE_INDEX(curp)) {
                /* if we found index with free entry, then use that
                 * entry: create all needed subtree and add new leaf */
                err = ext4_ext_split(icb, handle, inode, mb_flags, path, newext, i);
                if (err)
                        goto out;

                /* refill path */
                path = ext4_find_extent(inode,
                                (ext4_lblk_t)le32_to_cpu(newext->ee_block),
                                ppath, gb_flags);
                if (IS_ERR(path))
                        err = PTR_ERR(path);
        } else {
                /* tree is full, time to grow in depth */
                err = ext4_ext_grow_indepth(icb, handle, inode, mb_flags);
                if (err)
                        goto out;

                /* refill path */
                path = ext4_find_extent(inode,
                                (ext4_lblk_t)le32_to_cpu(newext->ee_block),
                                ppath, gb_flags);
                if (IS_ERR(path)) {
                        err = PTR_ERR(path);
                        goto out;
                }

                /*
                 * only first (depth 0 -> 1) produces free space;
                 * in all other cases we have to split the grown tree
                 */
                depth = ext_depth(inode);
                if (path[depth].p_hdr->eh_entries == path[depth].p_hdr->eh_max) {
                        /* now we need to split */
                        goto repeat;
                }
        }

out:
        return err;
}

/*
 * search the closest allocated block to the left for *logical
 * and returns it at @logical + it's physical address at @phys
 * if *logical is the smallest allocated block, the function
 * returns 0 at @phys
 * return value contains 0 (success) or error code
 */
static int ext4_ext_search_left(struct inode *inode,
                struct ext4_ext_path *path,
                ext4_lblk_t *logical, ext4_fsblk_t *phys)
{
        struct ext4_extent_idx *ix;
        struct ext4_extent *ex;
        int depth, ee_len;

        if (unlikely(path == NULL)) {
                EXT4_ERROR_INODE(inode, "path == NULL *logical %d!", *logical);
                return -EIO;
        }
        depth = path->p_depth;
        *phys = 0;

        if (depth == 0 && path->p_ext == NULL)
                return 0;

        /* usually extent in the path covers blocks smaller
         * then *logical, but it can be that extent is the
         * first one in the file */

        ex = path[depth].p_ext;
        ee_len = ext4_ext_get_actual_len(ex);
        if (*logical < le32_to_cpu(ex->ee_block)) {
                if (unlikely(EXT_FIRST_EXTENT(path[depth].p_hdr) != ex)) {
                        EXT4_ERROR_INODE(inode,
                                        "EXT_FIRST_EXTENT != ex *logical %d ee_block %d!",
                                        *logical, le32_to_cpu(ex->ee_block));
                        return -EIO;
                }
                while (--depth >= 0) {
                        ix = path[depth].p_idx;
                        if (unlikely(ix != EXT_FIRST_INDEX(path[depth].p_hdr))) {
                                EXT4_ERROR_INODE(inode,
                                                "ix (%d) != EXT_FIRST_INDEX (%d) (depth %d)!",
                                                ix != NULL ? le32_to_cpu(ix->ei_block) : 0,
                                                EXT_FIRST_INDEX(path[depth].p_hdr) != NULL ?
                                                le32_to_cpu(EXT_FIRST_INDEX(path[depth].p_hdr)->ei_block) : 0,
                                                depth);
                                return -EIO;
                        }
                }
                return 0;
        }

        if (unlikely(*logical < (le32_to_cpu(ex->ee_block) + ee_len))) {
                EXT4_ERROR_INODE(inode,
                                "logical %d < ee_block %d + ee_len %d!",
                                *logical, le32_to_cpu(ex->ee_block), ee_len);
                return -EIO;
        }

        *logical = le32_to_cpu(ex->ee_block) + ee_len - 1;
        *phys = ext4_ext_pblock(ex) + ee_len - 1;
        return 0;
}

/*
 * search the closest allocated block to the right for *logical
 * and returns it at @logical + it's physical address at @phys
 * if *logical is the largest allocated block, the function
 * returns 0 at @phys
 * return value contains 0 (success) or error code
 */
static int ext4_ext_search_right(struct inode *inode,
                struct ext4_ext_path *path,
                ext4_lblk_t *logical, ext4_fsblk_t *phys,
                struct ext4_extent **ret_ex)
{
        struct buffer_head *bh = NULL;
        struct ext4_extent_header *eh;
        struct ext4_extent_idx *ix;
        struct ext4_extent *ex;
        ext4_fsblk_t block;
        int depth;      /* Note, NOT eh_depth; depth from top of tree */
        int ee_len;

        if ((path == NULL)) {
                EXT4_ERROR_INODE(inode, "path == NULL *logical %d!", *logical);
                return -EIO;
        }
        depth = path->p_depth;
        *phys = 0;

        if (depth == 0 && path->p_ext == NULL)
                return 0;

        /* usually extent in the path covers blocks smaller
         * then *logical, but it can be that extent is the
         * first one in the file */

        ex = path[depth].p_ext;
        ee_len = ext4_ext_get_actual_len(ex);
        /*if (*logical < le32_to_cpu(ex->ee_block)) {*/
        if (*logical < (ex->ee_block)) {
                if (unlikely(EXT_FIRST_EXTENT(path[depth].p_hdr) != ex)) {
                        EXT4_ERROR_INODE(inode,
                                        "first_extent(path[%d].p_hdr) != ex",
                                        depth);
                        return -EIO;
                }
                while (--depth >= 0) {
                        ix = path[depth].p_idx;
                        if (unlikely(ix != EXT_FIRST_INDEX(path[depth].p_hdr))) {
                                EXT4_ERROR_INODE(inode,
                                                "ix != EXT_FIRST_INDEX *logical %d!",
                                                *logical);
                                return -EIO;
                        }
                }
                goto found_extent;
        }

        /*if (unlikely(*logical < (le32_to_cpu(ex->ee_block) + ee_len))) {*/
        if (unlikely(*logical < ((ex->ee_block) + ee_len))) {
                EXT4_ERROR_INODE(inode,
                                "logical %d < ee_block %d + ee_len %d!",
                                /**logical, le32_to_cpu(ex->ee_block), ee_len);*/
                        *logical, (ex->ee_block), ee_len);
                return -EIO;
        }

        if (ex != EXT_LAST_EXTENT(path[depth].p_hdr)) {
                /* next allocated block in this leaf */
                ex++;
                goto found_extent;
        }

        /* go up and search for index to the right */
        while (--depth >= 0) {
                ix = path[depth].p_idx;
                if (ix != EXT_LAST_INDEX(path[depth].p_hdr))
                        goto got_index;
        }

        /* we've gone up to the root and found no index to the right */
        return 0;

got_index:
        /* we've found index to the right, let's
         * follow it and find the closest allocated
         * block to the right */
        ix++;
        block = ext4_idx_pblock(ix);
        while (++depth < path->p_depth) {
                /* subtract from p_depth to get proper eh_depth */
                bh = read_extent_tree_block(inode, block,
                                path->p_depth - depth, 0);
                if (IS_ERR(bh))
                        return PTR_ERR(bh);
                eh = ext_block_hdr(bh);
                ix = EXT_FIRST_INDEX(eh);
                block = ext4_idx_pblock(ix);
                extents_brelse(bh);
        }

        bh = read_extent_tree_block(inode, block, path->p_depth - depth, 0);
        if (IS_ERR(bh))
                return PTR_ERR(bh);
        eh = ext_block_hdr(bh);
        ex = EXT_FIRST_EXTENT(eh);
found_extent:
        /**logical = le32_to_cpu(ex->ee_block);*/
        *logical = (ex->ee_block);
        *phys = ext4_ext_pblock(ex);
        *ret_ex = ex;
        if (bh)
                extents_brelse(bh);
        return 0;
}

/*
 * ext4_ext_next_allocated_block:
 * returns allocated block in subsequent extent or EXT_MAX_BLOCKS.
 * NOTE: it considers block number from index entry as
 * allocated block. Thus, index entries have to be consistent
 * with leaves.
 */
ext4_lblk_t
ext4_ext_next_allocated_block(struct ext4_ext_path *path)
{
        int depth;

        depth = path->p_depth;

        if (depth == 0 && path->p_ext == NULL)
                return EXT_MAX_BLOCKS;

        while (depth >= 0) {
                if (depth == path->p_depth) {
                        /* leaf */
                        if (path[depth].p_ext &&
                                        path[depth].p_ext !=
                                        EXT_LAST_EXTENT(path[depth].p_hdr))
                                return le32_to_cpu(path[depth].p_ext[1].ee_block);
                } else {
                        /* index */
                        if (path[depth].p_idx !=
                                        EXT_LAST_INDEX(path[depth].p_hdr))
                                return le32_to_cpu(path[depth].p_idx[1].ei_block);
                }
                depth--;
        }

        return EXT_MAX_BLOCKS;
}

/*
 * ext4_ext_next_leaf_block:
 * returns first allocated block from next leaf or EXT_MAX_BLOCKS
 */
static ext4_lblk_t ext4_ext_next_leaf_block(struct ext4_ext_path *path)
{
        int depth;

        BUG_ON(path == NULL);
        depth = path->p_depth;

        /* zero-tree has no leaf blocks at all */
        if (depth == 0)
                return EXT_MAX_BLOCKS;

        /* go to index block */
        depth--;

        while (depth >= 0) {
                if (path[depth].p_idx !=
                                EXT_LAST_INDEX(path[depth].p_hdr))
                        return (ext4_lblk_t)
                                le32_to_cpu(path[depth].p_idx[1].ei_block);
                depth--;
        }

        return EXT_MAX_BLOCKS;
}

/*
 * ext4_ext_correct_indexes:
 * if leaf gets modified and modified extent is first in the leaf,
 * then we have to correct all indexes above.
 * TODO: do we need to correct tree in all cases?
 */
static int ext4_ext_correct_indexes(void *icb, handle_t *handle, struct inode *inode,
                struct ext4_ext_path *path)
{
        struct ext4_extent_header *eh;
        int depth = ext_depth(inode);
        struct ext4_extent *ex;
        __le32 border;
        int k, err = 0;

        eh = path[depth].p_hdr;
        ex = path[depth].p_ext;

        if (unlikely(ex == NULL || eh == NULL)) {
                EXT4_ERROR_INODE(inode,
                                "ex %p == NULL or eh %p == NULL", ex, eh);
                return -EIO;
        }

        if (depth == 0) {
                /* there is no tree at all */
                return 0;
        }

        if (ex != EXT_FIRST_EXTENT(eh)) {
                /* we correct tree if first leaf got modified only */
                return 0;
        }

        /*
         * TODO: we need correction if border is smaller than current one
         */
        k = depth - 1;
        border = path[depth].p_ext->ee_block;
        err = ext4_ext_get_access(icb, handle, inode, path + k);
        if (err)
                return err;
        path[k].p_idx->ei_block = border;
        err = ext4_ext_dirty(icb, handle, inode, path + k);
        if (err)
                return err;

        while (k--) {
                /* change all left-side indexes */
                if (path[k+1].p_idx != EXT_FIRST_INDEX(path[k+1].p_hdr))
                        break;
                err = ext4_ext_get_access(icb, handle, inode, path + k);
                if (err)
                        break;
                path[k].p_idx->ei_block = border;
                err = ext4_ext_dirty(icb, handle, inode, path + k);
                if (err)
                        break;
        }

        return err;
}

int
ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
                struct ext4_extent *ex2)
{
        unsigned short ext1_ee_len, ext2_ee_len;

        /*
         * Make sure that both extents are initialized. We don't merge
         * unwritten extents so that we can be sure that end_io code has
         * the extent that was written properly split out and conversion to
         * initialized is trivial.
         */
        if (ext4_ext_is_unwritten(ex1) != ext4_ext_is_unwritten(ex2))
                return 0;

        ext1_ee_len = ext4_ext_get_actual_len(ex1);
        ext2_ee_len = ext4_ext_get_actual_len(ex2);

        if (le32_to_cpu(ex1->ee_block) + ext1_ee_len !=
                        le32_to_cpu(ex2->ee_block))
                return 0;

        /*
         * To allow future support for preallocated extents to be added
         * as an RO_COMPAT feature, refuse to merge to extents if
         * this can result in the top bit of ee_len being set.
         */
        if (ext1_ee_len + ext2_ee_len > EXT_INIT_MAX_LEN)
                return 0;
        if (ext4_ext_is_unwritten(ex1) &&
                        (ext1_ee_len + ext2_ee_len > EXT_UNWRITTEN_MAX_LEN))
                return 0;
#ifdef AGGRESSIVE_TEST
        if (ext1_ee_len >= 4)
                return 0;
#endif

        if (ext4_ext_pblock(ex1) + ext1_ee_len == ext4_ext_pblock(ex2))
                return 1;
        return 0;
}

/*
 * This function tries to merge the "ex" extent to the next extent in the tree.
 * It always tries to merge towards right. If you want to merge towards
 * left, pass "ex - 1" as argument instead of "ex".
 * Returns 0 if the extents (ex and ex+1) were _not_ merged and returns
 * 1 if they got merged.
 */
static int ext4_ext_try_to_merge_right(struct inode *inode,
                struct ext4_ext_path *path,
                struct ext4_extent *ex)
{
        struct ext4_extent_header *eh;
        unsigned int depth, len;
        int merge_done = 0, unwritten;

        depth = ext_depth(inode);
        assert(path[depth].p_hdr != NULL);
        eh = path[depth].p_hdr;

        while (ex < EXT_LAST_EXTENT(eh)) {
                if (!ext4_can_extents_be_merged(inode, ex, ex + 1))
                        break;
                /* merge with next extent! */
                unwritten = ext4_ext_is_unwritten(ex);
                ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
                                + ext4_ext_get_actual_len(ex + 1));
                if (unwritten)
                        ext4_ext_mark_unwritten(ex);

                if (ex + 1 < EXT_LAST_EXTENT(eh)) {
                        len = (EXT_LAST_EXTENT(eh) - ex - 1)
                                * sizeof(struct ext4_extent);
                        memmove(ex + 1, ex + 2, len);
                }
                le16_add_cpu(&eh->eh_entries, -1);
                merge_done = 1;
                if (!eh->eh_entries)
                        EXT4_ERROR_INODE(inode, "eh->eh_entries = 0!");
        }

        return merge_done;
}

/*
 * This function does a very simple check to see if we can collapse
 * an extent tree with a single extent tree leaf block into the inode.
 */
static void ext4_ext_try_to_merge_up(void *icb, handle_t *handle,
                struct inode *inode,
                struct ext4_ext_path *path)
{
        size_t s;
        unsigned max_root = ext4_ext_space_root(inode, 0);
        ext4_fsblk_t blk;

        if ((path[0].p_depth != 1) ||
                        (le16_to_cpu(path[0].p_hdr->eh_entries) != 1) ||
                        (le16_to_cpu(path[1].p_hdr->eh_entries) > max_root))
                return;

        /*
         * We need to modify the block allocation bitmap and the block
         * group descriptor to release the extent tree block.  If we
         * can't get the journal credits, give up.
         */
        if (ext4_journal_extend(icb, handle, 2))
                return;

        /*
         * Copy the extent data up to the inode
         */
        blk = ext4_idx_pblock(path[0].p_idx);
        s = le16_to_cpu(path[1].p_hdr->eh_entries) *
                sizeof(struct ext4_extent_idx);
        s += sizeof(struct ext4_extent_header);

        path[1].p_maxdepth = path[0].p_maxdepth;
        memcpy(path[0].p_hdr, path[1].p_hdr, s);
        path[0].p_depth = 0;
        path[0].p_ext = EXT_FIRST_EXTENT(path[0].p_hdr) +
                (path[1].p_ext - EXT_FIRST_EXTENT(path[1].p_hdr));
        path[0].p_hdr->eh_max = cpu_to_le16(max_root);

        extents_brelse(path[1].p_bh);
        ext4_free_blocks(icb, handle, inode, NULL, blk, 1,
                        EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET);
}

/*
 * This function tries to merge the @ex extent to neighbours in the tree.
 * return 1 if merge left else 0.
 */
static void ext4_ext_try_to_merge(void *icb, handle_t *handle,
                struct inode *inode,
                struct ext4_ext_path *path,
                struct ext4_extent *ex) {
        struct ext4_extent_header *eh;
        unsigned int depth;
        int merge_done = 0;

        depth = ext_depth(inode);
        BUG_ON(path[depth].p_hdr == NULL);
        eh = path[depth].p_hdr;

        if (ex > EXT_FIRST_EXTENT(eh))
                merge_done = ext4_ext_try_to_merge_right(inode, path, ex - 1);

        if (!merge_done)
                (void) ext4_ext_try_to_merge_right(inode, path, ex);

        ext4_ext_try_to_merge_up(icb, handle, inode, path);
}

/*
 * ext4_ext_insert_extent:
 * tries to merge requsted extent into the existing extent or
 * inserts requested extent as new one into the tree,
 * creating new leaf in the no-space case.
 */
int ext4_ext_insert_extent(void *icb, handle_t *handle, struct inode *inode,
                struct ext4_ext_path **ppath,
                struct ext4_extent *newext,
                int gb_flags)
{
        struct ext4_ext_path *path = *ppath;
        struct ext4_extent_header *eh;
        struct ext4_extent *ex, *fex;
        struct ext4_extent *nearex; /* nearest extent */
        struct ext4_ext_path *npath = NULL;
        int depth, len, err;
        ext4_lblk_t next;
        int mb_flags = 0, unwritten;

        if (gb_flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
                mb_flags |= EXT4_MB_DELALLOC_RESERVED;
        if (unlikely(ext4_ext_get_actual_len(newext) == 0)) {
                EXT4_ERROR_INODE(inode, "ext4_ext_get_actual_len(newext) == 0");
                return -EIO;
        }
        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        eh = path[depth].p_hdr;
        if (unlikely(path[depth].p_hdr == NULL)) {
                EXT4_ERROR_INODE(inode, "path[%d].p_hdr == NULL", depth);
                return -EIO;
        }

        /* try to insert block into found extent and return */
        if (ex && !(gb_flags & EXT4_GET_BLOCKS_PRE_IO)) {

                /*
                 * Try to see whether we should rather test the extent on
                 * right from ex, or from the left of ex. This is because
                 * ext4_find_extent() can return either extent on the
                 * left, or on the right from the searched position. This
                 * will make merging more effective.
                 */
                if (ex < EXT_LAST_EXTENT(eh) &&
                                (le32_to_cpu(ex->ee_block) +
                                 ext4_ext_get_actual_len(ex) <
                                 le32_to_cpu(newext->ee_block))) {
                        ex += 1;
                        goto prepend;
                } else if ((ex > EXT_FIRST_EXTENT(eh)) &&
                                (le32_to_cpu(newext->ee_block) +
                                 ext4_ext_get_actual_len(newext) <
                                 le32_to_cpu(ex->ee_block)))
                        ex -= 1;

                /* Try to append newex to the ex */
                if (ext4_can_extents_be_merged(inode, ex, newext)) {
                        ext_debug("append [%d]%d block to %u:[%d]%d"
                                        "(from %llu)\n",
                                        ext4_ext_is_unwritten(newext),
                                        ext4_ext_get_actual_len(newext),
                                        le32_to_cpu(ex->ee_block),
                                        ext4_ext_is_unwritten(ex),
                                        ext4_ext_get_actual_len(ex),
                                        ext4_ext_pblock(ex));
                        err = ext4_ext_get_access(icb, handle, inode,
                                        path + depth);
                        if (err)
                                return err;
                        unwritten = ext4_ext_is_unwritten(ex);
                        ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
                                        + ext4_ext_get_actual_len(newext));
                        if (unwritten)
                                ext4_ext_mark_unwritten(ex);
                        eh = path[depth].p_hdr;
                        nearex = ex;
                        goto merge;
                }

prepend:
                /* Try to prepend newex to the ex */
                if (ext4_can_extents_be_merged(inode, newext, ex)) {
                        ext_debug("prepend %u[%d]%d block to %u:[%d]%d"
                                        "(from %llu)\n",
                                        le32_to_cpu(newext->ee_block),
                                        ext4_ext_is_unwritten(newext),
                                        ext4_ext_get_actual_len(newext),
                                        le32_to_cpu(ex->ee_block),
                                        ext4_ext_is_unwritten(ex),
                                        ext4_ext_get_actual_len(ex),
                                        ext4_ext_pblock(ex));
                        err = ext4_ext_get_access(icb, handle, inode,
                                        path + depth);
                        if (err)
                                return err;

                        unwritten = ext4_ext_is_unwritten(ex);
                        ex->ee_block = newext->ee_block;
                        ext4_ext_store_pblock(ex, ext4_ext_pblock(newext));
                        ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
                                        + ext4_ext_get_actual_len(newext));
                        if (unwritten)
                                ext4_ext_mark_unwritten(ex);
                        eh = path[depth].p_hdr;
                        nearex = ex;
                        goto merge;
                }
        }

        depth = ext_depth(inode);
        eh = path[depth].p_hdr;
        if (le16_to_cpu(eh->eh_entries) < le16_to_cpu(eh->eh_max))
                goto has_space;

        /* probably next leaf has space for us? */
        fex = EXT_LAST_EXTENT(eh);
        next = EXT_MAX_BLOCKS;
        if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block))
                next = ext4_ext_next_leaf_block(path);
        if (next != EXT_MAX_BLOCKS) {
                ext_debug("next leaf block - %u\n", next);
                BUG_ON(npath != NULL);
                npath = ext4_find_extent(inode, next, NULL, 0);
                if (IS_ERR(npath))
                        return PTR_ERR(npath);
                BUG_ON(npath->p_depth != path->p_depth);
                eh = npath[depth].p_hdr;
                if (le16_to_cpu(eh->eh_entries) < le16_to_cpu(eh->eh_max)) {
                        ext_debug("next leaf isn't full(%d)\n",
                                        le16_to_cpu(eh->eh_entries));
                        path = npath;
                        goto has_space;
                }
                ext_debug("next leaf has no free space(%d,%d)\n",
                                le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));
        }

        /*
         * There is no free space in the found leaf.
         * We're gonna add a new leaf in the tree.
         */
        if (gb_flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
                mb_flags |= EXT4_MB_USE_RESERVED;
        err = ext4_ext_create_new_leaf(icb, handle, inode, mb_flags, gb_flags,
                        ppath, newext);
        if (err)
                goto cleanup;
        depth = ext_depth(inode);
        eh = path[depth].p_hdr;

has_space:
        nearex = path[depth].p_ext;

        err = ext4_ext_get_access(icb, handle, inode, path + depth);
        if (err)
                goto cleanup;

        if (!nearex) {
                /* there is no extent in this leaf, create first one */
                ext_debug("first extent in the leaf: %u:%llu:[%d]%d\n",
                                le32_to_cpu(newext->ee_block),
                                ext4_ext_pblock(newext),
                                ext4_ext_is_unwritten(newext),
                                ext4_ext_get_actual_len(newext));
                nearex = EXT_FIRST_EXTENT(eh);
        } else {
                if (le32_to_cpu(newext->ee_block)
                                > le32_to_cpu(nearex->ee_block)) {
                        /* Insert after */
                        ext_debug("insert %u:%llu:[%d]%d before: "
                                        "nearest %p\n",
                                        le32_to_cpu(newext->ee_block),
                                        ext4_ext_pblock(newext),
                                        ext4_ext_is_unwritten(newext),
                                        ext4_ext_get_actual_len(newext),
                                        nearex);
                        nearex++;
                } else {
                        /* Insert before */
                        BUG_ON(newext->ee_block == nearex->ee_block);
                        ext_debug("insert %u:%llu:[%d]%d after: "
                                        "nearest %p\n",
                                        le32_to_cpu(newext->ee_block),
                                        ext4_ext_pblock(newext),
                                        ext4_ext_is_unwritten(newext),
                                        ext4_ext_get_actual_len(newext),
                                        nearex);
                }
                len = EXT_LAST_EXTENT(eh) - nearex + 1;
                if (len > 0) {
                        ext_debug("insert %u:%llu:[%d]%d: "
                                        "move %d extents from 0x%p to 0x%p\n",
                                        le32_to_cpu(newext->ee_block),
                                        ext4_ext_pblock(newext),
                                        ext4_ext_is_unwritten(newext),
                                        ext4_ext_get_actual_len(newext),
                                        len, nearex, nearex + 1);
                        memmove(nearex + 1, nearex,
                                        len * sizeof(struct ext4_extent));
                }
        }

        le16_add_cpu(&eh->eh_entries, 1);
        path[depth].p_ext = nearex;
        nearex->ee_block = newext->ee_block;
        ext4_ext_store_pblock(nearex, ext4_ext_pblock(newext));
        nearex->ee_len = newext->ee_len;

merge:
        /* try to merge extents */
        if (!(gb_flags & EXT4_GET_BLOCKS_PRE_IO))
                ext4_ext_try_to_merge(icb, handle, inode, path, nearex);


        /* time to correct all indexes above */
        err = ext4_ext_correct_indexes(icb, handle, inode, path);
        if (err)
                goto cleanup;

        err = ext4_ext_dirty(icb, handle, inode, path + path->p_depth);

cleanup:
        if (npath) {
                ext4_ext_drop_refs(npath);
                kfree(npath);
        }
        return err;
}

static inline int get_default_free_blocks_flags(struct inode *inode)
{
        return 0;
}

/* FIXME!! we need to try to merge to left or right after zero-out  */
static int ext4_ext_zeroout(struct inode *inode, struct ext4_extent *ex)
{
        ext4_fsblk_t ee_pblock;
        unsigned int ee_len;
        int ret;

        ee_len    = ext4_ext_get_actual_len(ex);
        ee_pblock = ext4_ext_pblock(ex);

        ret = 0;

        return ret;
}

static int ext4_remove_blocks(void *icb, handle_t *handle, struct inode *inode,
                struct ext4_extent *ex,
                unsigned long from, unsigned long to)
{
        struct buffer_head *bh;
        int i;

        if (from >= le32_to_cpu(ex->ee_block)
                        && to == le32_to_cpu(ex->ee_block) + ext4_ext_get_actual_len(ex) - 1) {
                /* tail removal */
                unsigned long num, start;
                num = le32_to_cpu(ex->ee_block) + ext4_ext_get_actual_len(ex) - from;
                start = ext4_ext_pblock(ex) + ext4_ext_get_actual_len(ex) - num;
                ext4_free_blocks(icb, handle, inode, NULL, start, num, 0);
        } else if (from == le32_to_cpu(ex->ee_block)
                        && to <= le32_to_cpu(ex->ee_block) + ext4_ext_get_actual_len(ex) - 1) {
        } else {
        }
        return 0;
}

/*
 * routine removes index from the index block
 * it's used in truncate case only. thus all requests are for
 * last index in the block only
 */
int ext4_ext_rm_idx(void *icb, handle_t *handle, struct inode *inode,
                struct ext4_ext_path *path)
{
        int err;
        ext4_fsblk_t leaf;

        /* free index block */
        path--;
        leaf = ext4_idx_pblock(path->p_idx);
        BUG_ON(path->p_hdr->eh_entries == 0);
        if ((err = ext4_ext_get_access(icb, handle, inode, path)))
                return err;
        path->p_hdr->eh_entries = cpu_to_le16(le16_to_cpu(path->p_hdr->eh_entries)-1);
        if ((err = ext4_ext_dirty(icb, handle, inode, path)))
                return err;
        ext4_free_blocks(icb, handle, inode, NULL, leaf, 1, 0);
        return err;
}

static int
ext4_ext_rm_leaf(void *icb, handle_t *handle, struct inode *inode,
                struct ext4_ext_path *path, unsigned long start)
{
        int err = 0, correct_index = 0;
        int depth = ext_depth(inode), credits;
        struct ext4_extent_header *eh;
        unsigned a, b, block, num;
        unsigned long ex_ee_block;
        unsigned short ex_ee_len;
        struct ext4_extent *ex;

        /* the header must be checked already in ext4_ext_remove_space() */
        if (!path[depth].p_hdr)
                path[depth].p_hdr = ext_block_hdr(path[depth].p_bh);
        eh = path[depth].p_hdr;
        BUG_ON(eh == NULL);

        /* find where to start removing */
        ex = EXT_LAST_EXTENT(eh);

        ex_ee_block = le32_to_cpu(ex->ee_block);
        ex_ee_len = ext4_ext_get_actual_len(ex);

        while (ex >= EXT_FIRST_EXTENT(eh) &&
                        ex_ee_block + ex_ee_len > start) {
                path[depth].p_ext = ex;

                a = ex_ee_block > start ? ex_ee_block : start;
                b = (unsigned long long)ex_ee_block + ex_ee_len - 1 < 
                        EXT_MAX_BLOCKS ? ex_ee_block + ex_ee_len - 1 : EXT_MAX_BLOCKS;


                if (a != ex_ee_block && b != ex_ee_block + ex_ee_len - 1) {
                        block = 0;
                        num = 0;
                        BUG();
                } else if (a != ex_ee_block) {
                        /* remove tail of the extent */
                        block = ex_ee_block;
                        num = a - block;
                } else if (b != ex_ee_block + ex_ee_len - 1) {
                        /* remove head of the extent */
                        block = a;
                        num = b - a;
                        /* there is no "make a hole" API yet */
                        BUG();
                } else {
                        /* remove whole extent: excellent! */
                        block = ex_ee_block;
                        num = 0;
                        BUG_ON(a != ex_ee_block);
                        BUG_ON(b != ex_ee_block + ex_ee_len - 1);
                }

                /* at present, extent can't cross block group */
                /* leaf + bitmap + group desc + sb + inode */
                credits = 5;
                if (ex == EXT_FIRST_EXTENT(eh)) {
                        correct_index = 1;
                        credits += (ext_depth(inode)) + 1;
                }

                /*handle = ext4_ext_journal_restart(icb, handle, credits);*/
                /*if (IS_ERR(icb, handle)) {*/
                /*err = PTR_ERR(icb, handle);*/
                /*goto out;*/
                /*}*/

                err = ext4_ext_get_access(icb, handle, inode, path + depth);
                if (err)
                        goto out;

                err = ext4_remove_blocks(icb, handle, inode, ex, a, b);
                if (err)
                        goto out;

                if (num == 0) {
                        /* this extent is removed entirely mark slot unused */
                        ext4_ext_store_pblock(ex, 0);
                        eh->eh_entries = cpu_to_le16(le16_to_cpu(eh->eh_entries)-1);
                }

                ex->ee_block = cpu_to_le32(block);
                ex->ee_len = cpu_to_le16(num);

                err = ext4_ext_dirty(icb, handle, inode, path + depth);
                if (err)
                        goto out;

                ex--;
                ex_ee_block = le32_to_cpu(ex->ee_block);
                ex_ee_len = ext4_ext_get_actual_len(ex);
        }

        if (correct_index && eh->eh_entries)
                err = ext4_ext_correct_indexes(icb, handle, inode, path);

        /* if this leaf is free, then we should
         * remove it from index block above */
        if (err == 0 && eh->eh_entries == 0 && path[depth].p_bh != NULL)
                err = ext4_ext_rm_idx(icb, handle, inode, path + depth);

out:
        return err;
}

/*
 * ext4_split_extent_at() splits an extent at given block.
 *
 * @handle: the journal handle
 * @inode: the file inode
 * @path: the path to the extent
 * @split: the logical block where the extent is splitted.
 * @split_flags: indicates if the extent could be zeroout if split fails, and
 *               the states(init or unwritten) of new extents.
 * @flags: flags used to insert new extent to extent tree.
 *
 *
 * Splits extent [a, b] into two extents [a, @split) and [@split, b], states
 * of which are deterimined by split_flag.
 *
 * There are two cases:
 *  a> the extent are splitted into two extent.
 *  b> split is not needed, and just mark the extent.
 *
 * return 0 on success.
 */
static int ext4_split_extent_at(void *icb, handle_t *handle,
                struct inode *inode,
                struct ext4_ext_path **ppath,
                ext4_lblk_t split,
                int split_flag,
                int flags)
{
        struct ext4_ext_path *path = *ppath;
        ext4_fsblk_t newblock;
        ext4_lblk_t ee_block;
        struct ext4_extent *ex, newex, orig_ex, zero_ex;
        struct ext4_extent *ex2 = NULL;
        unsigned int ee_len, depth;
        int err = 0;

        ext4_ext_show_leaf(inode, path);

        depth = ext_depth(inode);
        ex = path[depth].p_ext;
        ee_block = le32_to_cpu(ex->ee_block);
        ee_len = ext4_ext_get_actual_len(ex);
        newblock = split - ee_block + ext4_ext_pblock(ex);

        BUG_ON(split < ee_block || split >= (ee_block + ee_len));

        err = ext4_ext_get_access(icb, handle, inode, path + depth);
        if (err)
                goto out;

        if (split == ee_block) {
                /*
                 * case b: block @split is the block that the extent begins with
                 * then we just change the state of the extent, and splitting
                 * is not needed.
                 */
                if (split_flag & EXT4_EXT_MARK_UNWRIT2)
                        ext4_ext_mark_unwritten(ex);
                else
                        ext4_ext_mark_initialized(ex);

                if (!(flags & EXT4_GET_BLOCKS_PRE_IO))
                        ext4_ext_try_to_merge(icb, handle, inode, path, ex);

                err = ext4_ext_dirty(icb, handle, inode, path + path->p_depth);
                goto out;
        }

        /* case a */
        memcpy(&orig_ex, ex, sizeof(orig_ex));
        ex->ee_len = cpu_to_le16(split - ee_block);
        if (split_flag & EXT4_EXT_MARK_UNWRIT1)
                ext4_ext_mark_unwritten(ex);

        /*
         * path may lead to new leaf, not to original leaf any more
         * after ext4_ext_insert_extent() returns,
         */
        err = ext4_ext_dirty(icb, handle, inode, path + depth);
        if (err)
                goto fix_extent_len;

        ex2 = &newex;
        ex2->ee_block = cpu_to_le32(split);
        ex2->ee_len   = cpu_to_le16(ee_len - (split - ee_block));
        ext4_ext_store_pblock(ex2, newblock);
        if (split_flag & EXT4_EXT_MARK_UNWRIT2)
                ext4_ext_mark_unwritten(ex2);

        err = ext4_ext_insert_extent(icb, handle, inode, ppath, &newex, flags);
        if (err == -ENOSPC && (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
                if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) {
                        if (split_flag & EXT4_EXT_DATA_VALID1) {
                                err = ext4_ext_zeroout(inode, ex2);
                                zero_ex.ee_block = ex2->ee_block;
                                zero_ex.ee_len = cpu_to_le16(
                                                ext4_ext_get_actual_len(ex2));
                                ext4_ext_store_pblock(&zero_ex,
                                                ext4_ext_pblock(ex2));
                        } else {
                                err = ext4_ext_zeroout(inode, ex);
                                zero_ex.ee_block = ex->ee_block;
                                zero_ex.ee_len = cpu_to_le16(
                                                ext4_ext_get_actual_len(ex));
                                ext4_ext_store_pblock(&zero_ex,
                                                ext4_ext_pblock(ex));
                        }
                } else {
                        err = ext4_ext_zeroout(inode, &orig_ex);
                        zero_ex.ee_block = orig_ex.ee_block;
                        zero_ex.ee_len = cpu_to_le16(
                                        ext4_ext_get_actual_len(&orig_ex));
                        ext4_ext_store_pblock(&zero_ex,
                                        ext4_ext_pblock(&orig_ex));
                }

                if (err)
                        goto fix_extent_len;
                /* update the extent length and mark as initialized */
                ex->ee_len = cpu_to_le16(ee_len);
                ext4_ext_try_to_merge(icb, handle, inode, path, ex);
                err = ext4_ext_dirty(icb, handle, inode, path + path->p_depth);
                if (err)
                        goto fix_extent_len;

                goto out;
        } else if (err)
                goto fix_extent_len;

out:
        ext4_ext_show_leaf(inode, path);
        return err;

fix_extent_len:
        ex->ee_len = orig_ex.ee_len;
        ext4_ext_dirty(icb, handle, inode, path + path->p_depth);
        return err;
}

/*
 * returns 1 if current index have to be freed (even partial)
 */
static inline int
ext4_ext_more_to_rm(struct ext4_ext_path *path)
{
        BUG_ON(path->p_idx == NULL);

        if (path->p_idx < EXT_FIRST_INDEX(path->p_hdr))
                return 0;

        /*
         * if truncate on deeper level happened it it wasn't partial
         * so we have to consider current index for truncation
         */
        if (le16_to_cpu(path->p_hdr->eh_entries) == path->p_block)
                return 0;
        return 1;
}

int ext4_ext_remove_space(void *icb, struct inode *inode, unsigned long start)
{
#ifndef __REACTOS__
        struct super_block *sb = inode->i_sb;
#endif
        int depth = ext_depth(inode);
        struct ext4_ext_path *path;
        handle_t *handle = NULL;
        int i = 0, err = 0;

        /* probably first extent we're gonna free will be last in block */
        /*handle = ext4_journal_start(inode, depth + 1);*/
        /*if (IS_ERR(icb, handle))*/
        /*return PTR_ERR(icb, handle);*/

        /*
         * we start scanning from right side freeing all the blocks
         * after i_size and walking into the deep
         */
        path = kmalloc(sizeof(struct ext4_ext_path) * (depth + 1), GFP_KERNEL);
        if (path == NULL) {
                ext4_journal_stop(icb, handle);
                return -ENOMEM;
        }
        memset(path, 0, sizeof(struct ext4_ext_path) * (depth + 1));
        path[0].p_hdr = ext_inode_hdr(inode);
        if (ext4_ext_check_inode(inode)) {
                err = -EIO;
                goto out;
        }
        path[0].p_depth = depth;

        while (i >= 0 && err == 0) {
                if (i == depth) {
                        /* this is leaf block */
                        err = ext4_ext_rm_leaf(icb, handle, inode, path, start);
                        /* root level have p_bh == NULL, extents_brelse() eats this */
                        extents_brelse(path[i].p_bh);
                        path[i].p_bh = NULL;
                        i--;
                        continue;
                }

                /* this is index block */
                if (!path[i].p_hdr) {
                        path[i].p_hdr = ext_block_hdr(path[i].p_bh);
                }

                if (!path[i].p_idx) {
                        /* this level hasn't touched yet */
                        path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
                        path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries)+1;
                } else {
                        /* we've already was here, see at next index */
                        path[i].p_idx--;
                }

                if (ext4_ext_more_to_rm(path + i)) {
                        struct buffer_head *bh;
                        /* go to the next level */
                        memset(path + i + 1, 0, sizeof(*path));
                        bh = read_extent_tree_block(inode, ext4_idx_pblock(path[i].p_idx), path[0].p_depth - (i + 1), 0);
                        if (IS_ERR(bh)) {
                                /* should we reset i_size? */
                                err = -EIO;
                                break;
                        }
                        path[i+1].p_bh = bh;

                        /* put actual number of indexes to know is this
                         * number got changed at the next iteration */
                        path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries);
                        i++;
                } else {
                        /* we finish processing this index, go up */
                        if (path[i].p_hdr->eh_entries == 0 && i > 0) {
                                /* index is empty, remove it
                                 * handle must be already prepared by the
                                 * truncatei_leaf() */
                                err = ext4_ext_rm_idx(icb, handle, inode, path + i);
                        }
                        /* root level have p_bh == NULL, extents_brelse() eats this */
                        extents_brelse(path[i].p_bh);
                        path[i].p_bh = NULL;
                        i--;
                }
        }

        /* TODO: flexible tree reduction should be here */
        if (path->p_hdr->eh_entries == 0) {
                /*
                 * truncate to zero freed all the tree
                 * so, we need to correct eh_depth
                 */
                err = ext4_ext_get_access(icb, handle, inode, path);
                if (err == 0) {
                        ext_inode_hdr(inode)->eh_depth = 0;
                        ext_inode_hdr(inode)->eh_max =
                                cpu_to_le16(ext4_ext_space_root(inode, 0));
                        err = ext4_ext_dirty(icb, handle, inode, path);
                }
        }
out:
        if (path) {
                ext4_ext_drop_refs(path);
                kfree(path);
        }
        ext4_journal_stop(icb, handle);

        return err;
}

int ext4_ext_tree_init(void *icb, handle_t *handle, struct inode *inode)
{
        struct ext4_extent_header *eh;

        eh = ext_inode_hdr(inode);
        eh->eh_depth = 0;
        eh->eh_entries = 0;
        eh->eh_magic = EXT4_EXT_MAGIC;
        eh->eh_max = cpu_to_le16(ext4_ext_space_root(inode, 0));
        ext4_mark_inode_dirty(icb, handle, inode);
        return 0;
}

/*
 * called at mount time
 */
void ext4_ext_init(struct super_block *sb)
{
        /*
         * possible initialization would be here
         */
}

static int ext4_ext_convert_to_initialized (
                void *icb,
                handle_t *handle,
                struct inode *inode,
                struct ext4_ext_path **ppath,
                ext4_lblk_t split,
                unsigned long blocks,
                int flags)
{
        int depth = ext_depth(inode), err;
        struct ext4_extent *ex = (*ppath)[depth].p_ext;

        assert (le32_to_cpu(ex->ee_block) <= split);

        if (split + blocks == le32_to_cpu(ex->ee_block) + 
                                                  ext4_ext_get_actual_len(ex)) {

                /* split and initialize right part */
                err = ext4_split_extent_at(icb, handle, inode, ppath, split,
                                                                   EXT4_EXT_MARK_UNWRIT1, flags);

        } else if (le32_to_cpu(ex->ee_block) == split) {

                /* split and initialize left part */
                err = ext4_split_extent_at(icb, handle, inode, ppath, split + blocks,
                                                                   EXT4_EXT_MARK_UNWRIT2, flags);

        } else {

                /* split 1 extent to 3 and initialize the 2nd */
                err = ext4_split_extent_at(icb, handle, inode, ppath, split + blocks,
                                                                   EXT4_EXT_MARK_UNWRIT1 |
                                                                   EXT4_EXT_MARK_UNWRIT2, flags);
                if (0 == err) {
                        err = ext4_split_extent_at(icb, handle, inode, ppath, split,
                                                                           EXT4_EXT_MARK_UNWRIT1, flags);
                }
        }

        return err;
}

int ext4_ext_get_blocks(void *icb, handle_t *handle, struct inode *inode, ext4_fsblk_t iblock,
                unsigned long max_blocks, struct buffer_head *bh_result,
                int create, int flags)
{
        struct ext4_ext_path *path = NULL;
        struct ext4_extent newex, *ex;
        int goal, err = 0, depth;
        unsigned long allocated = 0;
        ext4_fsblk_t next, newblock;

        clear_buffer_new(bh_result);
        /*mutex_lock(&ext4_I(inode)->truncate_mutex);*/

        /* find extent for this block */
        path = ext4_find_extent(inode, iblock, NULL, 0);
        if (IS_ERR(path)) {
                err = PTR_ERR(path);
                path = NULL;
                goto out2;
        }

        depth = ext_depth(inode);

        /*
         * consistent leaf must not be empty
         * this situations is possible, though, _during_ tree modification
         * this is why assert can't be put in ext4_ext_find_extent()
         */
        BUG_ON(path[depth].p_ext == NULL && depth != 0);

        if ((ex = path[depth].p_ext)) {
                ext4_lblk_t ee_block = le32_to_cpu(ex->ee_block);
                ext4_fsblk_t ee_start = ext4_ext_pblock(ex);
                unsigned short ee_len  = ext4_ext_get_actual_len(ex);
                /* if found exent covers block, simple return it */
                if (iblock >= ee_block && iblock < ee_block + ee_len) {

                        /* number of remain blocks in the extent */
                        allocated = ee_len + ee_block - iblock;

                        if (ext4_ext_is_unwritten(ex)) {
                                if (create) {
                                        newblock = iblock - ee_block + ee_start;
                                        err = ext4_ext_convert_to_initialized (
                                                        icb, handle,
                                                        inode,
                                                        &path,
                                                        iblock,
                                                        allocated,
                                                        flags);
                                        if (err)
                                                goto out2;

                                } else {
                                        newblock = 0;
                                }
                        } else {
                                newblock = iblock - ee_block + ee_start;
                        }
                        goto out;
                }
        }

        /*
         * requested block isn't allocated yet
         * we couldn't try to create block if create flag is zero
         */
        if (!create) {
                goto out2;
        }

        /* find next allocated block so that we know how many
         * blocks we can allocate without ovelapping next extent */
        next = ext4_ext_next_allocated_block(path);
        BUG_ON(next <= iblock);
        allocated = next - iblock;
        if (flags & EXT4_GET_BLOCKS_PRE_IO && max_blocks > EXT_UNWRITTEN_MAX_LEN)
                max_blocks = EXT_UNWRITTEN_MAX_LEN;
        if (allocated > max_blocks)
                allocated = max_blocks;

        /* allocate new block */
        goal = ext4_ext_find_goal(inode, path, iblock);
        newblock = ext4_new_meta_blocks(icb, handle, inode, goal, 0,
                        &allocated, &err);
        if (!newblock)
                goto out2;

        /* try to insert new extent into found leaf and return */
        newex.ee_block = cpu_to_le32(iblock);
        ext4_ext_store_pblock(&newex, newblock);
        newex.ee_len = cpu_to_le16(allocated);
        /* if it's fallocate, mark ex as unwritten */
        if (flags & EXT4_GET_BLOCKS_PRE_IO) {
                ext4_ext_mark_unwritten(&newex);
        }
        err = ext4_ext_insert_extent(icb, handle, inode, &path, &newex,
                                 flags & EXT4_GET_BLOCKS_PRE_IO);

        if (err) {
                /* free data blocks we just allocated */
                ext4_free_blocks(icb, handle, inode, NULL, ext4_ext_pblock(&newex),
                                le16_to_cpu(newex.ee_len), get_default_free_blocks_flags(inode));
                goto out2;
        }
        
        ext4_mark_inode_dirty(icb, handle, inode);

        /* previous routine could use block we allocated */
        if (ext4_ext_is_unwritten(&newex))
                newblock = 0;
        else
                newblock = ext4_ext_pblock(&newex);

        set_buffer_new(bh_result);

out:
        if (allocated > max_blocks)
                allocated = max_blocks;

        ext4_ext_show_leaf(inode, path);
        set_buffer_mapped(bh_result);
        bh_result->b_bdev = inode->i_sb->s_bdev;
        bh_result->b_blocknr = newblock;
out2:
        if (path) {
                ext4_ext_drop_refs(path);
                kfree(path);
        }
        /*mutex_unlock(&ext4_I(inode)->truncate_mutex);*/

        return err ? err : allocated;
}

#ifdef _MSC_VER
#pragma warning(pop)
#endif