/*
   * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
   * Written by Alex Tomas <alex@clusterfs.com>
   *
   * Architecture independence:
   *   Copyright (c) 2005, Bull S.A.
   *   Written by Pierre Peiffer <pierre.peiffer@bull.net>
   *
   * 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 License

   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
   */
  
  /*
   * Extents support for EXT4
   *
   * TODO:
   *   - ext4*_error() should be used in some situations
   *   - analyze all BUG()/BUG_ON(), use -EIO where appropriate
   *   - smart tree reduction
   */

  #include <linux/fs.h>
  #include <linux/time.h>

  #include <linux/jbd2.h>

  #include <linux/highuid.h>
  #include <linux/pagemap.h>
  #include <linux/quotaops.h>
  #include <linux/string.h>
  #include <linux/slab.h>

  #include <asm/uaccess.h>

  #include <linux/fiemap.h>

  #include <linux/backing-dev.h>

  #include "ext4_jbd2.h"

  #include "ext4_extents.h"

  #include "xattr.h"

  #include <trace/events/ext4.h>

  /*
   * 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 */

  static __le32 ext4_extent_block_csum(struct inode *inode,
  				     struct ext4_extent_header *eh)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	__u32 csum;
  
  	csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)eh,
  			   EXT4_EXTENT_TAIL_OFFSET(eh));
  	return cpu_to_le32(csum);
  }
  
  static int ext4_extent_block_csum_verify(struct inode *inode,
  					 struct ext4_extent_header *eh)
  {
  	struct ext4_extent_tail *et;

  	if (!ext4_has_metadata_csum(inode->i_sb))

  		return 1;
  
  	et = find_ext4_extent_tail(eh);
  	if (et->et_checksum != ext4_extent_block_csum(inode, eh))
  		return 0;
  	return 1;
  }
  
  static void ext4_extent_block_csum_set(struct inode *inode,
  				       struct ext4_extent_header *eh)
  {
  	struct ext4_extent_tail *et;

  	if (!ext4_has_metadata_csum(inode->i_sb))

  		return;
  
  	et = find_ext4_extent_tail(eh);
  	et->et_checksum = ext4_extent_block_csum(inode, eh);
  }

  static int ext4_split_extent(handle_t *handle,
  				struct inode *inode,

  				struct ext4_ext_path **ppath,

  				struct ext4_map_blocks *map,
  				int split_flag,
  				int flags);

  static int ext4_split_extent_at(handle_t *handle,
  			     struct inode *inode,

  			     struct ext4_ext_path **ppath,

  			     ext4_lblk_t split,
  			     int split_flag,
  			     int flags);

  static int ext4_find_delayed_extent(struct inode *inode,

  				    struct extent_status *newes);

  static int ext4_ext_truncate_extend_restart(handle_t *handle,
  					    struct inode *inode,
  					    int needed)

  {
  	int err;

  	if (!ext4_handle_valid(handle))
  		return 0;

  	if (handle->h_buffer_credits >= needed)

  		return 0;

  	/*
  	 * If we need to extend the journal get a few extra blocks
  	 * while we're at it for efficiency's sake.
  	 */
  	needed += 3;
  	err = ext4_journal_extend(handle, needed - handle->h_buffer_credits);

  	if (err <= 0)

  		return err;

  	err = ext4_truncate_restart_trans(handle, inode, needed);

  	if (err == 0)
  		err = -EAGAIN;

  
  	return err;

  }
  
  /*
   * could return:
   *  - EROFS
   *  - ENOMEM
   */
  static int ext4_ext_get_access(handle_t *handle, struct inode *inode,
  				struct ext4_ext_path *path)
  {
  	if (path->p_bh) {
  		/* path points to block */

  		BUFFER_TRACE(path->p_bh, "get_write_access");

  		return ext4_journal_get_write_access(handle, path->p_bh);
  	}
  	/* path points to leaf/index in inode body */
  	/* we use in-core data, no need to protect them */
  	return 0;
  }
  
  /*
   * could return:
   *  - EROFS
   *  - ENOMEM
   *  - EIO
   */

  int __ext4_ext_dirty(const char *where, unsigned int line, handle_t *handle,
  		     struct inode *inode, struct ext4_ext_path *path)

  {
  	int err;

  
  	WARN_ON(!rwsem_is_locked(&EXT4_I(inode)->i_data_sem));

  	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, handle,
  						   inode, path->p_bh);

  	} else {
  		/* path points to leaf/index in inode body */
  		err = ext4_mark_inode_dirty(handle, inode);
  	}
  	return err;
  }

  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(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(handle, inode, goal, flags,
  					NULL, err);

  	return newblock;
  }

  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_data);
  	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_data);
  	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 inline int
  ext4_force_split_extent_at(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(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));
  }

  /*
   * Calculate the number of metadata blocks needed
   * to allocate @blocks
   * Worse case is one block per extent
   */

  int ext4_ext_calc_metadata_amount(struct inode *inode, ext4_lblk_t lblock)

  {

  	struct ext4_inode_info *ei = EXT4_I(inode);

  	int idxs;

  	idxs = ((inode->i_sb->s_blocksize - sizeof(struct ext4_extent_header))
  		/ sizeof(struct ext4_extent_idx));

  
  	/*

  	 * If the new delayed allocation block is contiguous with the
  	 * previous da block, it can share index blocks with the
  	 * previous block, so we only need to allocate a new index
  	 * block every idxs leaf blocks.  At ldxs**2 blocks, we need
  	 * an additional index block, and at ldxs**3 blocks, yet
  	 * another index blocks.

  	 */

  	if (ei->i_da_metadata_calc_len &&
  	    ei->i_da_metadata_calc_last_lblock+1 == lblock) {

  		int num = 0;

  		if ((ei->i_da_metadata_calc_len % idxs) == 0)
  			num++;
  		if ((ei->i_da_metadata_calc_len % (idxs*idxs)) == 0)
  			num++;
  		if ((ei->i_da_metadata_calc_len % (idxs*idxs*idxs)) == 0) {
  			num++;
  			ei->i_da_metadata_calc_len = 0;
  		} else
  			ei->i_da_metadata_calc_len++;
  		ei->i_da_metadata_calc_last_lblock++;
  		return num;
  	}

  	/*
  	 * In the worst case we need a new set of index blocks at
  	 * every level of the inode's extent tree.
  	 */
  	ei->i_da_metadata_calc_len = 1;
  	ei->i_da_metadata_calc_last_lblock = lblock;
  	return ext_depth(inode) + 1;

  }

  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_valid_extent(struct inode *inode, struct ext4_extent *ext)
  {

  	ext4_fsblk_t block = ext4_ext_pblock(ext);

  	int len = ext4_ext_get_actual_len(ext);

  	ext4_lblk_t lblock = le32_to_cpu(ext->ee_block);

  	/*
  	 * We allow neither:
  	 *  - zero length
  	 *  - overflow/wrap-around
  	 */
  	if (lblock + len <= lblock)

  		return 0;

  	return ext4_data_block_valid(EXT4_SB(inode->i_sb), block, len);

  }
  
  static int ext4_valid_extent_idx(struct inode *inode,
  				struct ext4_extent_idx *ext_idx)
  {

  	ext4_fsblk_t block = ext4_idx_pblock(ext_idx);

  	return ext4_data_block_valid(EXT4_SB(inode->i_sb), block, 1);

  }
  
  static int ext4_valid_extent_entries(struct inode *inode,
  				struct ext4_extent_header *eh,
  				int depth)
  {

  	unsigned short entries;
  	if (eh->eh_entries == 0)
  		return 1;
  
  	entries = le16_to_cpu(eh->eh_entries);
  
  	if (depth == 0) {
  		/* leaf entries */

  		struct ext4_extent *ext = EXT_FIRST_EXTENT(eh);

  		struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
  		ext4_fsblk_t pblock = 0;
  		ext4_lblk_t lblock = 0;
  		ext4_lblk_t prev = 0;
  		int len = 0;

  		while (entries) {
  			if (!ext4_valid_extent(inode, ext))
  				return 0;

  
  			/* Check for overlapping extents */
  			lblock = le32_to_cpu(ext->ee_block);
  			len = ext4_ext_get_actual_len(ext);
  			if ((lblock <= prev) && prev) {
  				pblock = ext4_ext_pblock(ext);
  				es->s_last_error_block = cpu_to_le64(pblock);
  				return 0;
  			}

  			ext++;
  			entries--;

  			prev = lblock + len - 1;

  		}
  	} else {

  		struct ext4_extent_idx *ext_idx = EXT_FIRST_INDEX(eh);

  		while (entries) {
  			if (!ext4_valid_extent_idx(inode, ext_idx))
  				return 0;
  			ext_idx++;
  			entries--;
  		}
  	}
  	return 1;
  }

  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)

  {
  	const char *error_msg;

  	int max = 0, err = -EFSCORRUPTED;

  
  	if (unlikely(eh->eh_magic != EXT4_EXT_MAGIC)) {
  		error_msg = "invalid magic";
  		goto corrupted;
  	}
  	if (unlikely(le16_to_cpu(eh->eh_depth) != depth)) {
  		error_msg = "unexpected eh_depth";
  		goto corrupted;
  	}
  	if (unlikely(eh->eh_max == 0)) {
  		error_msg = "invalid eh_max";
  		goto corrupted;
  	}
  	max = ext4_ext_max_entries(inode, depth);
  	if (unlikely(le16_to_cpu(eh->eh_max) > max)) {
  		error_msg = "too large eh_max";
  		goto corrupted;
  	}
  	if (unlikely(le16_to_cpu(eh->eh_entries) > le16_to_cpu(eh->eh_max))) {
  		error_msg = "invalid eh_entries";
  		goto corrupted;
  	}

  	if (!ext4_valid_extent_entries(inode, eh, depth)) {
  		error_msg = "invalid extent entries";
  		goto corrupted;
  	}

  	if (unlikely(depth > 32)) {
  		error_msg = "too large eh_depth";
  		goto corrupted;
  	}

  	/* Verify checksum on non-root extent tree nodes */
  	if (ext_depth(inode) != depth &&
  	    !ext4_extent_block_csum_verify(inode, eh)) {
  		error_msg = "extent tree corrupted";

  		err = -EFSBADCRC;

  		goto corrupted;
  	}

  	return 0;
  
  corrupted:

  	ext4_error_inode(inode, function, line, 0,

  			 "pblk %llu bad header/extent: %s - magic %x, "
  			 "entries %u, max %u(%u), depth %u(%u)",
  			 (unsigned long long) pblk, error_msg,
  			 le16_to_cpu(eh->eh_magic),
  			 le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max),
  			 max, le16_to_cpu(eh->eh_depth), depth);

  	return err;

  }

  #define ext4_ext_check(inode, eh, depth, pblk)			\
  	__ext4_ext_check(__func__, __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 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 = sb_getblk_gfp(inode->i_sb, pblk, __GFP_MOVABLE | GFP_NOFS);

  	if (unlikely(!bh))
  		return ERR_PTR(-ENOMEM);

  	if (!bh_uptodate_or_lock(bh)) {
  		trace_ext4_ext_load_extent(inode, pblk, _RET_IP_);
  		err = bh_submit_read(bh);
  		if (err < 0)
  			goto errout;
  	}

  	if (buffer_verified(bh) && !(flags & EXT4_EX_FORCE_CACHE))

  		return bh;
  	err = __ext4_ext_check(function, line, inode,

  			       ext_block_hdr(bh), depth, pblk);

  	if (err)
  		goto errout;

  	set_buffer_verified(bh);

  	/*
  	 * If this is a leaf block, cache all of its entries
  	 */
  	if (!(flags & EXT4_EX_NOCACHE) && depth == 0) {
  		struct ext4_extent_header *eh = ext_block_hdr(bh);
  		struct ext4_extent *ex = EXT_FIRST_EXTENT(eh);
  		ext4_lblk_t prev = 0;
  		int i;
  
  		for (i = le16_to_cpu(eh->eh_entries); i > 0; i--, ex++) {
  			unsigned int status = EXTENT_STATUS_WRITTEN;
  			ext4_lblk_t lblk = le32_to_cpu(ex->ee_block);
  			int len = ext4_ext_get_actual_len(ex);
  
  			if (prev && (prev != lblk))
  				ext4_es_cache_extent(inode, prev,
  						     lblk - prev, ~0,
  						     EXTENT_STATUS_HOLE);

  			if (ext4_ext_is_unwritten(ex))

  				status = EXTENT_STATUS_UNWRITTEN;
  			ext4_es_cache_extent(inode, lblk, len,
  					     ext4_ext_pblock(ex), status);
  			prev = lblk + len;
  		}
  	}

  	return bh;
  errout:
  	put_bh(bh);
  	return ERR_PTR(err);

  }

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

  /*
   * This function is called to cache a file's extent information in the
   * extent status tree
   */
  int ext4_ext_precache(struct inode *inode)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	struct ext4_ext_path *path = NULL;
  	struct buffer_head *bh;
  	int i = 0, depth, ret = 0;
  
  	if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
  		return 0;	/* not an extent-mapped inode */
  
  	down_read(&ei->i_data_sem);
  	depth = ext_depth(inode);
  
  	path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 1),
  		       GFP_NOFS);
  	if (path == NULL) {
  		up_read(&ei->i_data_sem);
  		return -ENOMEM;
  	}
  
  	/* Don't cache anything if there are no external extent blocks */
  	if (depth == 0)
  		goto out;
  	path[0].p_hdr = ext_inode_hdr(inode);
  	ret = ext4_ext_check(inode, path[0].p_hdr, depth, 0);
  	if (ret)
  		goto out;
  	path[0].p_idx = EXT_FIRST_INDEX(path[0].p_hdr);
  	while (i >= 0) {
  		/*
  		 * If this is a leaf block or we've reached the end of
  		 * the index block, go up
  		 */
  		if ((i == depth) ||
  		    path[i].p_idx > EXT_LAST_INDEX(path[i].p_hdr)) {
  			brelse(path[i].p_bh);
  			path[i].p_bh = NULL;
  			i--;
  			continue;
  		}
  		bh = read_extent_tree_block(inode,
  					    ext4_idx_pblock(path[i].p_idx++),
  					    depth - i - 1,
  					    EXT4_EX_FORCE_CACHE);
  		if (IS_ERR(bh)) {
  			ret = PTR_ERR(bh);
  			break;
  		}
  		i++;
  		path[i].p_bh = bh;
  		path[i].p_hdr = ext_block_hdr(bh);
  		path[i].p_idx = EXT_FIRST_INDEX(path[i].p_hdr);
  	}
  	ext4_set_inode_state(inode, EXT4_STATE_EXT_PRECACHED);
  out:
  	up_read(&ei->i_data_sem);
  	ext4_ext_drop_refs(path);
  	kfree(path);
  	return ret;
  }

  #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("
  ");
  }
  
  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
  ", 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("
  ");
  }

  
  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
  ", 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
  ",
  				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

  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) {
  			brelse(path->p_bh);
  			path->p_bh = NULL;
  		}
  }
  
  /*

   * 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 < le32_to_cpu(m->ei_block))
  			r = m - 1;
  		else
  			l = m + 1;

  		ext_debug("%p(%u):%p(%u):%p(%u) ", l, le32_to_cpu(l->ei_block),
  				m, le32_to_cpu(m->ei_block),
  				r, le32_to_cpu(r->ei_block));

  	}
  
  	path->p_idx = l - 1;

  	ext_debug("  -> %u->%lld ", le32_to_cpu(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 < le16_to_cpu(eh->eh_entries); k++, ix++) {
  		  if (k != 0 &&
  		      le32_to_cpu(ix->ei_block) <= le32_to_cpu(ix[-1].ei_block)) {

  				printk(KERN_DEBUG "k=%d, ix=0x%p, "
  				       "first=0x%p
  ", k,
  				       ix, EXT_FIRST_INDEX(eh));
  				printk(KERN_DEBUG "%u <= %u
  ",

  				       le32_to_cpu(ix->ei_block),
  				       le32_to_cpu(ix[-1].ei_block));
  			}
  			BUG_ON(k && le32_to_cpu(ix->ei_block)

  					   <= le32_to_cpu(ix[-1].ei_block));

  			if (block < le32_to_cpu(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 < le32_to_cpu(m->ee_block))
  			r = m - 1;
  		else
  			l = m + 1;

  		ext_debug("%p(%u):%p(%u):%p(%u) ", l, le32_to_cpu(l->ee_block),
  				m, le32_to_cpu(m->ee_block),
  				r, le32_to_cpu(r->ee_block));

  	}
  
  	path->p_ext = l - 1;

  	ext_debug("  -> %d:%llu:[%d]%d ",

  			le32_to_cpu(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 && le32_to_cpu(ex->ee_block)

  					  <= le32_to_cpu(ex[-1].ee_block));

  			if (block < le32_to_cpu(ex->ee_block))
  				break;
  			chex = ex;
  		}
  		BUG_ON(chex != path->p_ext);
  	}
  #endif
  
  }
  
  int ext4_ext_tree_init(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(handle, inode);

  	return 0;
  }
  
  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
  ",
  			  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 (IS_ERR(bh)) {

  			ret = PTR_ERR(bh);

  			goto err;

  		}

  		eh = ext_block_hdr(bh);
  		ppos++;

  		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);

  	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(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(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 -EFSCORRUPTED;

  	}

  
  	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 -EFSCORRUPTED;

  	}

  	if (logical > le32_to_cpu(curp->p_idx->ei_block)) {
  		/* insert after */

  		ext_debug("insert new index %d after: %llu
  ", logical, ptr);

  		ix = curp->p_idx + 1;
  	} else {
  		/* insert before */

  		ext_debug("insert new index %d before: %llu
  ", 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
  ",
  				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 -EFSCORRUPTED;

  	}

  	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 -EFSCORRUPTED;

  	}

  
  	err = ext4_ext_dirty(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(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 -EFSCORRUPTED;

  	}

  	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
  ",

  				  le32_to_cpu(border));

  	} else {
  		border = newext->ee_block;
  		ext_debug("leaf will be added."
  				" next leaf starts at %d
  ",

  				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
  ", depth - at);
  	for (a = 0; a < depth - at; a++) {

  		newblock = ext4_ext_new_meta_block(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 = -EFSCORRUPTED;

  		goto cleanup;
  	}

  	bh = sb_getblk_gfp(inode->i_sb, newblock, __GFP_MOVABLE | GFP_NOFS);

  	if (unlikely(!bh)) {

  		err = -ENOMEM;

  		goto cleanup;
  	}
  	lock_buffer(bh);

  	err = ext4_journal_get_create_access(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 = -EFSCORRUPTED;

  		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);
  	unlock_buffer(bh);

  	err = ext4_handle_dirty_metadata(handle, inode, bh);

  	if (err)

  		goto cleanup;
  	brelse(bh);
  	bh = NULL;
  
  	/* correct old leaf */
  	if (m) {

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

  			goto cleanup;

  		le16_add_cpu(&path[depth].p_hdr->eh_entries, -m);

  		err = ext4_ext_dirty(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 = -EFSCORRUPTED;

  		goto cleanup;
  	}

  	if (k)
  		ext_debug("create %d intermediate indices
  ", 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 = sb_getblk(inode->i_sb, newblock);

  		if (unlikely(!bh)) {

  			err = -ENOMEM;

  			goto cleanup;
  		}
  		lock_buffer(bh);

  		err = ext4_journal_get_create_access(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
  ",
  				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 = -EFSCORRUPTED;

  			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
  ", 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);
  		unlock_buffer(bh);

  		err = ext4_handle_dirty_metadata(handle, inode, bh);

  		if (err)

  			goto cleanup;
  		brelse(bh);
  		bh = NULL;
  
  		/* correct old index */
  		if (m) {
  			err = ext4_ext_get_access(handle, inode, path + i);
  			if (err)
  				goto cleanup;

  			le16_add_cpu(&path[i].p_hdr->eh_entries, -m);

  			err = ext4_ext_dirty(handle, inode, path + i);
  			if (err)
  				goto cleanup;
  		}
  
  		i--;
  	}
  
  	/* insert new index */

  	err = ext4_ext_insert_index(handle, inode, path + at,
  				    le32_to_cpu(border), newblock);
  
  cleanup:
  	if (bh) {
  		if (buffer_locked(bh))
  			unlock_buffer(bh);
  		brelse(bh);
  	}
  
  	if (err) {
  		/* free all allocated blocks in error case */
  		for (i = 0; i < depth; i++) {
  			if (!ablocks[i])
  				continue;

  			ext4_free_blocks(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(handle_t *handle, struct inode *inode,

  				 unsigned int flags)

  {

  	struct ext4_extent_header *neh;

  	struct buffer_head *bh;

  	ext4_fsblk_t newblock, goal = 0;
  	struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;

  	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)));
  	if (goal > le32_to_cpu(es->s_first_data_block)) {
  		flags |= EXT4_MB_HINT_TRY_GOAL;
  		goal--;
  	} else
  		goal = ext4_inode_to_goal_block(inode);
  	newblock = ext4_new_meta_blocks(handle, inode, goal, flags,
  					NULL, &err);

  	if (newblock == 0)
  		return err;

  	bh = sb_getblk_gfp(inode->i_sb, newblock, __GFP_MOVABLE | GFP_NOFS);

  	if (unlikely(!bh))

  		return -ENOMEM;

  	lock_buffer(bh);

  	err = ext4_journal_get_create_access(handle, bh);
  	if (err) {

  		unlock_buffer(bh);
  		goto out;
  	}
  
  	/* move top-level index/leaf into new block */

  	memmove(bh->b_data, EXT4_I(inode)->i_data,
  		sizeof(EXT4_I(inode)->i_data));

  
  	/* 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 = cpu_to_le16(ext4_ext_space_block_idx(inode, 0));

  	else

  		neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));

  	neh->eh_magic = EXT4_EXT_MAGIC;

  	ext4_extent_block_csum_set(inode, neh);

  	set_buffer_uptodate(bh);
  	unlock_buffer(bh);

  	err = ext4_handle_dirty_metadata(handle, inode, bh);

  	if (err)

  		goto out;

  	/* Update top-level index: num,max,pointer */

  	neh = ext_inode_hdr(inode);

  	neh->eh_entries = cpu_to_le16(1);
  	ext4_idx_store_pblock(EXT_FIRST_INDEX(neh), newblock);
  	if (neh->eh_depth == 0) {
  		/* Root extent block becomes index block */
  		neh->eh_max = cpu_to_le16(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
  ",

  		  le16_to_cpu(neh->eh_entries), le16_to_cpu(neh->eh_max),

  		  le32_to_cpu(EXT_FIRST_INDEX(neh)->ei_block),

  		  ext4_idx_pblock(EXT_FIRST_INDEX(neh)));

  	le16_add_cpu(&neh->eh_depth, 1);

  	ext4_mark_inode_dirty(handle, inode);

  out:
  	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(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(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(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 -EFSCORRUPTED;

  	}

  	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 -EFSCORRUPTED;

  		}

  		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 -EFSCORRUPTED;

  			}

  		}
  		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 -EFSCORRUPTED;

  	}

  	*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 (unlikely(path == NULL)) {
  		EXT4_ERROR_INODE(inode, "path == NULL *logical %d!", *logical);

  		return -EFSCORRUPTED;

  	}

  	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,
  					 "first_extent(path[%d].p_hdr) != ex",
  					 depth);

  			return -EFSCORRUPTED;

  		}

  		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 -EFSCORRUPTED;

  			}

  		}

  		goto found_extent;

  	}

  	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 -EFSCORRUPTED;

  	}

  
  	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);

  		put_bh(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);

  	*phys = ext4_ext_pblock(ex);

  	*ret_ex = ex;
  	if (bh)
  		put_bh(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;
  
  	BUG_ON(path == NULL);
  	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(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 -EFSCORRUPTED;

  	}

  
  	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(handle, inode, path + k);
  	if (err)

  		return err;
  	path[k].p_idx->ei_block = border;

  	err = ext4_ext_dirty(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(handle, inode, path + k);
  		if (err)

  			break;
  		path[k].p_idx->ei_block = border;

  		err = ext4_ext_dirty(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;

  	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;

  	/*
  	 * The check for IO to unwritten extent is somewhat racy as we
  	 * increment i_unwritten / set EXT4_STATE_DIO_UNWRITTEN only after
  	 * dropping i_data_sem. But reserved blocks should save us in that
  	 * case.
  	 */

  	if (ext4_ext_is_unwritten(ex1) &&

  	    (ext4_test_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN) ||
  	     atomic_read(&EXT4_I(inode)->i_unwritten) ||

  	     (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)