text: /*
   * 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 Licens
   * 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/module.h>
  #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 <linux/falloc.h>
  #include <asm/uaccess.h>
  #include <linux/fiemap.h>
  #include "ext4_jbd2.h"
  #include "ext4_extents.h"
  
  
  /*
   * ext_pblock:
   * combine low and high parts of physical block number into ext4_fsblk_t
   */
  ext4_fsblk_t ext_pblock(struct ext4_extent *ex)
  {
  	ext4_fsblk_t block;
  
  	block = le32_to_cpu(ex->ee_start_lo);
  	block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1;
  	return block;
  }
  
  /*
   * idx_pblock:
   * combine low and high parts of a leaf physical block number into ext4_fsblk_t
   */
  ext4_fsblk_t idx_pblock(struct ext4_extent_idx *ix)
  {
  	ext4_fsblk_t block;
  
  	block = le32_to_cpu(ix->ei_leaf_lo);
  	block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1;
  	return block;
  }
  
  /*
   * ext4_ext_store_pblock:
   * stores a large physical block number into an extent struct,
   * breaking it into parts
   */
  void ext4_ext_store_pblock(struct ext4_extent *ex, ext4_fsblk_t pb)
  {
  	ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
  	ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 0xffff);
  }
  
  /*
   * ext4_idx_store_pblock:
   * stores a large physical block number into an index struct,
   * breaking it into parts
   */
  static void ext4_idx_store_pblock(struct ext4_extent_idx *ix, ext4_fsblk_t pb)
  {
  	ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
  	ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) & 0xffff);
  }
  
  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;
  	err = ext4_journal_extend(handle, needed);
  	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 */
  		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
   */
  static int ext4_ext_dirty(handle_t *handle, struct inode *inode,
  				struct ext4_ext_path *path)
  {
  	int err;
  	if (path->p_bh) {
  		/* path points to block */
  		err = ext4_handle_dirty_metadata(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)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	ext4_fsblk_t bg_start;
  	ext4_fsblk_t last_block;
  	ext4_grpblk_t colour;
  	ext4_group_t block_group;
  	int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
  	int depth;
  
  	if (path) {
  		struct ext4_extent *ex;
  		depth = path->p_depth;
  
  		/* try to predict block placement */
  		ex = path[depth].p_ext;
  		if (ex)
  			return ext_pblock(ex)+(block-le32_to_cpu(ex->ee_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 */
  	block_group = ei->i_block_group;
  	if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
  		/*
  		 * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
  		 * block groups per flexgroup, reserve the first block
  		 * group for directories and special files.  Regular
  		 * files will start at the second block group.  This
  		 * tends to speed up directory access and improves
  		 * fsck times.
  		 */
  		block_group &= ~(flex_size-1);
  		if (S_ISREG(inode->i_mode))
  			block_group++;
  	}
  	bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
  	last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
  
  	/*
  	 * If we are doing delayed allocation, we don't need take
  	 * colour into account.
  	 */
  	if (test_opt(inode->i_sb, DELALLOC))
  		return bg_start;
  
  	if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
  		colour = (current->pid % 16) *
  			(EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
  	else
  		colour = (current->pid % 16) * ((last_block - bg_start) / 16);
  	return bg_start + colour + block;
  }
  
  /*
   * 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)
  {
  	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, 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);
  	if (!check) {
  #ifdef AGGRESSIVE_TEST
  		if (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);
  	if (!check) {
  #ifdef AGGRESSIVE_TEST
  		if (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);
  	if (!check) {
  #ifdef AGGRESSIVE_TEST
  		if (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);
  	if (!check) {
  #ifdef AGGRESSIVE_TEST
  		if (size > 4)
  			size = 4;
  #endif
  	}
  	return size;
  }
  
  /*
   * 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, sector_t lblock)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	int idxs, num = 0;
  
  	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) {
  		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 = ext_pblock(ext);
  	int len = ext4_ext_get_actual_len(ext);
  
  	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 = 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)
  {
  	struct ext4_extent *ext;
  	struct ext4_extent_idx *ext_idx;
  	unsigned short entries;
  	if (eh->eh_entries == 0)
  		return 1;
  
  	entries = le16_to_cpu(eh->eh_entries);
  
  	if (depth == 0) {
  		/* leaf entries */
  		ext = EXT_FIRST_EXTENT(eh);
  		while (entries) {
  			if (!ext4_valid_extent(inode, ext))
  				return 0;
  			ext++;
  			entries--;
  		}
  	} else {
  		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)
  {
  	const char *error_msg;
  	int max = 0;
  
  	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;
  	}
  	return 0;
  
  corrupted:
  	ext4_error_inode(inode, function, line, 0,
  			"bad header/extent: %s - magic %x, "
  			"entries %u, max %u(%u), depth %u(%u)",
  			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 -EIO;
  }
  
  #define ext4_ext_check(inode, eh, depth)	\
  	__ext4_ext_check(__func__, __LINE__, inode, eh, depth)
  
  int ext4_ext_check_inode(struct inode *inode)
  {
  	return ext4_ext_check(inode, ext_inode_hdr(inode), ext_depth(inode));
  }
  
  #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),
  			    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_uninitialized(path->p_ext),
  				  ext4_ext_get_actual_len(path->p_ext),
  				  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_uninitialized(ex),
  			  ext4_ext_get_actual_len(ex), ext_pblock(ex));
  	}
  	ext_debug("\n");
  }
  #else
  #define ext4_ext_show_path(inode, path)
  #define ext4_ext_show_leaf(inode, path)
  #endif
  
  void ext4_ext_drop_refs(struct ext4_ext_path *path)
  {
  	int depth = path->p_depth;
  	int i;
  
  	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("  -> %d->%lld ", le32_to_cpu(path->p_idx->ei_block),
  		  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\n", k,
  				       ix, EXT_FIRST_INDEX(eh));
  				printk(KERN_DEBUG "%u <= %u\n",
  				       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),
  			ext_pblock(path->p_ext),
  			ext4_ext_is_uninitialized(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);
  	ext4_ext_invalidate_cache(inode);
  	return 0;
  }
  
  struct ext4_ext_path *
  ext4_ext_find_extent(struct inode *inode, ext4_lblk_t block,
  					struct ext4_ext_path *path)
  {
  	struct ext4_extent_header *eh;
  	struct buffer_head *bh;
  	short int depth, i, ppos = 0, alloc = 0;
  
  	eh = ext_inode_hdr(inode);
  	depth = ext_depth(inode);
  
  	/* account possible depth increase */
  	if (!path) {
  		path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 2),
  				GFP_NOFS);
  		if (!path)
  			return ERR_PTR(-ENOMEM);
  		alloc = 1;
  	}
  	path[0].p_hdr = eh;
  	path[0].p_bh = NULL;
  
  	i = depth;
  	/* walk through the tree */
  	while (i) {
  		int need_to_validate = 0;
  
  		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 = idx_pblock(path[ppos].p_idx);
  		path[ppos].p_depth = i;
  		path[ppos].p_ext = NULL;
  
  		bh = sb_getblk(inode->i_sb, path[ppos].p_block);
  		if (unlikely(!bh))
  			goto err;
  		if (!bh_uptodate_or_lock(bh)) {
  			if (bh_submit_read(bh) < 0) {
  				put_bh(bh);
  				goto err;
  			}
  			/* validate the extent entries */
  			need_to_validate = 1;
  		}
  		eh = ext_block_hdr(bh);
  		ppos++;
  		if (unlikely(ppos > depth)) {
  			put_bh(bh);
  			EXT4_ERROR_INODE(inode,
  					 "ppos %d > depth %d", ppos, depth);
  			goto err;
  		}
  		path[ppos].p_bh = bh;
  		path[ppos].p_hdr = eh;
  		i--;
  
  		if (need_to_validate && ext4_ext_check(inode, eh, i))
  			goto err;
  	}
  
  	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 = ext_pblock(path[ppos].p_ext);
  
  	ext4_ext_show_path(inode, path);
  
  	return path;
  
  err:
  	ext4_ext_drop_refs(path);
  	if (alloc)
  		kfree(path);
  	return ERR_PTR(-EIO);
  }
  
  /*
   * ext4_ext_insert_index:
   * insert new index [@logical;@ptr] into the block at @curp;
   * check where to insert: before @curp or after @curp
   */
  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 -EIO;
  	}
  	len = EXT_MAX_INDEX(curp->p_hdr) - curp->p_idx;
  	if (logical > le32_to_cpu(curp->p_idx->ei_block)) {
  		/* insert after */
  		if (curp->p_idx != EXT_LAST_INDEX(curp->p_hdr)) {
  			len = (len - 1) * sizeof(struct ext4_extent_idx);
  			len = len < 0 ? 0 : len;
  			ext_debug("insert new index %d after: %llu. "
  					"move %d from 0x%p to 0x%p\n",
  					logical, ptr, len,
  					(curp->p_idx + 1), (curp->p_idx + 2));
  			memmove(curp->p_idx + 2, curp->p_idx + 1, len);
  		}
  		ix = curp->p_idx + 1;
  	} else {
  		/* insert before */
  		len = len * sizeof(struct ext4_extent_idx);
  		len = len < 0 ? 0 : len;
  		ext_debug("insert new index %d before: %llu. "
  				"move %d from 0x%p to 0x%p\n",
  				logical, ptr, len,
  				curp->p_idx, (curp->p_idx + 1));
  		memmove(curp->p_idx + 1, curp->p_idx, len);
  		ix = curp->p_idx;
  	}
  
  	ix->ei_block = cpu_to_le32(logical);
  	ext4_idx_store_pblock(ix, ptr);
  	le16_add_cpu(&curp->p_hdr->eh_entries, 1);
  
  	if (unlikely(le16_to_cpu(curp->p_hdr->eh_entries)
  			     > le16_to_cpu(curp->p_hdr->eh_max))) {
  		EXT4_ERROR_INODE(inode,
  				 "logical %d == ei_block %d!",
  				 logical, le32_to_cpu(curp->p_idx->ei_block));
  		return -EIO;
  	}
  	if (unlikely(ix > EXT_LAST_INDEX(curp->p_hdr))) {
  		EXT4_ERROR_INODE(inode, "ix > EXT_LAST_INDEX!");
  		return -EIO;
  	}
  
  	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,
  				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;
  	struct ext4_extent *ex;
  	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(handle, inode, path,
  						   newext, &err);
  		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 = sb_getblk(inode->i_sb, newblock);
  	if (!bh) {
  		err = -EIO;
  		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;
  	ex = EXT_FIRST_EXTENT(neh);
  
  	/* 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 */
  	/* TODO: we could do it by single memmove */
  	m = 0;
  	path[depth].p_ext++;
  	while (path[depth].p_ext <=
  			EXT_MAX_EXTENT(path[depth].p_hdr)) {
  		ext_debug("move %d:%llu:[%d]%d in new leaf %llu\n",
  				le32_to_cpu(path[depth].p_ext->ee_block),
  				ext_pblock(path[depth].p_ext),
  				ext4_ext_is_uninitialized(path[depth].p_ext),
  				ext4_ext_get_actual_len(path[depth].p_ext),
  				newblock);
  		/*memmove(ex++, path[depth].p_ext++,
  				sizeof(struct ext4_extent));
  		neh->eh_entries++;*/
  		path[depth].p_ext++;
  		m++;
  	}
  	if (m) {
  		memmove(ex, path[depth].p_ext-m, sizeof(struct ext4_extent)*m);
  		le16_add_cpu(&neh->eh_entries, m);
  	}
  
  	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 = -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 = sb_getblk(inode->i_sb, newblock);
  		if (!bh) {
  			err = -EIO;
  			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\n",
  				i, newblock, le32_to_cpu(border), oldblock);
  		/* copy indexes */
  		m = 0;
  		path[i].p_idx++;
  
  		ext_debug("cur 0x%p, last 0x%p\n", path[i].p_idx,
  				EXT_MAX_INDEX(path[i].p_hdr));
  		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;
  		}
  		while (path[i].p_idx <= EXT_MAX_INDEX(path[i].p_hdr)) {
  			ext_debug("%d: move %d:%llu in new index %llu\n", i,
  					le32_to_cpu(path[i].p_idx->ei_block),
  					idx_pblock(path[i].p_idx),
  					newblock);
  			/*memmove(++fidx, path[i].p_idx++,
  					sizeof(struct ext4_extent_idx));
  			neh->eh_entries++;
  			BUG_ON(neh->eh_entries > neh->eh_max);*/
  			path[i].p_idx++;
  			m++;
  		}
  		if (m) {
  			memmove(++fidx, path[i].p_idx - m,
  				sizeof(struct ext4_extent_idx) * m);
  			le16_add_cpu(&neh->eh_entries, m);
  		}
  		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, 0, 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,
  					struct ext4_ext_path *path,
  					struct ext4_extent *newext)
  {
  	struct ext4_ext_path *curp = path;
  	struct ext4_extent_header *neh;
  	struct buffer_head *bh;
  	ext4_fsblk_t newblock;
  	int err = 0;
  
  	newblock = ext4_ext_new_meta_block(handle, inode, path, newext, &err);
  	if (newblock == 0)
  		return err;
  
  	bh = sb_getblk(inode->i_sb, newblock);
  	if (!bh) {
  		err = -EIO;
  		ext4_std_error(inode->i_sb, err);
  		return err;
  	}
  	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, curp->p_hdr, 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;
  	set_buffer_uptodate(bh);
  	unlock_buffer(bh);
  
  	err = ext4_handle_dirty_metadata(handle, inode, bh);
  	if (err)
  		goto out;
  
  	/* create index in new top-level index: num,max,pointer */
  	err = ext4_ext_get_access(handle, inode, curp);
  	if (err)
  		goto out;
  
  	curp->p_hdr->eh_magic = EXT4_EXT_MAGIC;
  	curp->p_hdr->eh_max = cpu_to_le16(ext4_ext_space_root_idx(inode, 0));
  	curp->p_hdr->eh_entries = cpu_to_le16(1);
  	curp->p_idx = EXT_FIRST_INDEX(curp->p_hdr);
  
  	if (path[0].p_hdr->eh_depth)
  		curp->p_idx->ei_block =
  			EXT_FIRST_INDEX(path[0].p_hdr)->ei_block;
  	else
  		curp->p_idx->ei_block =
  			EXT_FIRST_EXTENT(path[0].p_hdr)->ee_block;
  	ext4_idx_store_pblock(curp->p_idx, newblock);
  
  	neh = ext_inode_hdr(inode);
  	ext_debug("new root: num %d(%d), lblock %d, ptr %llu\n",
  		  le16_to_cpu(neh->eh_entries), le16_to_cpu(neh->eh_max),
  		  le32_to_cpu(EXT_FIRST_INDEX(neh)->ei_block),
  		  idx_pblock(EXT_FIRST_INDEX(neh)));
  
  	neh->eh_depth = cpu_to_le16(path->p_depth + 1);
  	err = ext4_ext_dirty(handle, inode, curp);
  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,
  					struct ext4_ext_path *path,
  					struct ext4_extent *newext)
  {
  	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, path, newext, i);
  		if (err)
  			goto out;
  
  		/* refill path */
  		ext4_ext_drop_refs(path);
  		path = ext4_ext_find_extent(inode,
  				    (ext4_lblk_t)le32_to_cpu(newext->ee_block),
  				    path);
  		if (IS_ERR(path))
  			err = PTR_ERR(path);
  	} else {
  		/* tree is full, time to grow in depth */
  		err = ext4_ext_grow_indepth(handle, inode, path, newext);
  		if (err)
  			goto out;
  
  		/* refill path */
  		ext4_ext_drop_refs(path);
  		path = ext4_ext_find_extent(inode,
  				   (ext4_lblk_t)le32_to_cpu(newext->ee_block),
  				    path);
  		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
   */
  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 ? ix->ei_block : 0,
  				  EXT_FIRST_INDEX(path[depth].p_hdr) != NULL ?
  				    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 = 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 smallest allocated block, the function
   * returns 0 at @phys
   * return value contains 0 (success) or error code
   */
  int
  ext4_ext_search_right(struct inode *inode, struct ext4_ext_path *path,
  			ext4_lblk_t *logical, ext4_fsblk_t *phys)
  {
  	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 -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,
  					 "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;
  			}
  		}
  		*logical = le32_to_cpu(ex->ee_block);
  		*phys = ext_pblock(ex);
  		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;
  	}
  
  	if (ex != EXT_LAST_EXTENT(path[depth].p_hdr)) {
  		/* next allocated block in this leaf */
  		ex++;
  		*logical = le32_to_cpu(ex->ee_block);
  		*phys = ext_pblock(ex);
  		return 0;
  	}
  
  	/* 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 = idx_pblock(ix);
  	while (++depth < path->p_depth) {
  		bh = sb_bread(inode->i_sb, block);
  		if (bh == NULL)
  			return -EIO;
  		eh = ext_block_hdr(bh);
  		/* subtract from p_depth to get proper eh_depth */
  		if (ext4_ext_check(inode, eh, path->p_depth - depth)) {
  			put_bh(bh);
  			return -EIO;
  		}
  		ix = EXT_FIRST_INDEX(eh);
  		block = idx_pblock(ix);
  		put_bh(bh);
  	}
  
  	bh = sb_bread(inode->i_sb, block);
  	if (bh == NULL)
  		return -EIO;
  	eh = ext_block_hdr(bh);
  	if (ext4_ext_check(inode, eh, path->p_depth - depth)) {
  		put_bh(bh);
  		return -EIO;
  	}
  	ex = EXT_FIRST_EXTENT(eh);
  	*logical = le32_to_cpu(ex->ee_block);
  	*phys = ext_pblock(ex);
  	put_bh(bh);
  	return 0;
  }
  
  /*
   * ext4_ext_next_allocated_block:
   * returns allocated block in subsequent extent or EXT_MAX_BLOCK.
   * NOTE: it considers block number from index entry as
   * allocated block. Thus, index entries have to be consistent
   * with leaves.
   */
  static 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_BLOCK;
  
  	while (depth >= 0) {
  		if (depth == path->p_depth) {
  			/* leaf */
  			if (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_BLOCK;
  }
  
  /*
   * ext4_ext_next_leaf_block:
   * returns first allocated block from next leaf or EXT_MAX_BLOCK
   */
  static ext4_lblk_t ext4_ext_next_leaf_block(struct inode *inode,
  					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_BLOCK;
  
  	/* 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_BLOCK;
  }
  
  /*
   * 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 -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(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, max_len;
  
  	/*
  	 * Make sure that either both extents are uninitialized, or
  	 * both are _not_.
  	 */
  	if (ext4_ext_is_uninitialized(ex1) ^ ext4_ext_is_uninitialized(ex2))
  		return 0;
  
  	if (ext4_ext_is_uninitialized(ex1))
  		max_len = EXT_UNINIT_MAX_LEN;
  	else
  		max_len = EXT_INIT_MAX_LEN;
  
  	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 > max_len)
  		return 0;
  #ifdef AGGRESSIVE_TEST
  	if (ext1_ee_len >= 4)
  		return 0;
  #endif
  
  	if (ext_pblock(ex1) + ext1_ee_len == 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.
   */
  int ext4_ext_try_to_merge(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;
  	int uninitialized = 0;
  
  	depth = ext_depth(inode);
  	BUG_ON(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! */
  		if (ext4_ext_is_uninitialized(ex))
  			uninitialized = 1;
  		ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
  				+ ext4_ext_get_actual_len(ex + 1));
  		if (uninitialized)
  			ext4_ext_mark_uninitialized(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;
  		WARN_ON(eh->eh_entries == 0);
  		if (!eh->eh_entries)
  			EXT4_ERROR_INODE(inode, "eh->eh_entries = 0!");
  	}
  
  	return merge_done;
  }
  
  /*
   * check if a portion of the "newext" extent overlaps with an
   * existing extent.
   *
   * If there is an overlap discovered, it updates the length of the newext
   * such that there will be no overlap, and then returns 1.
   * If there is no overlap found, it returns 0.
   */
  unsigned int ext4_ext_check_overlap(struct inode *inode,
  				    struct ext4_extent *newext,
  				    struct ext4_ext_path *path)
  {
  	ext4_lblk_t b1, b2;
  	unsigned int depth, len1;
  	unsigned int ret = 0;
  
  	b1 = le32_to_cpu(newext->ee_block);
  	len1 = ext4_ext_get_actual_len(newext);
  	depth = ext_depth(inode);
  	if (!path[depth].p_ext)
  		goto out;
  	b2 = le32_to_cpu(path[depth].p_ext->ee_block);
  
  	/*
  	 * get the next allocated block if the extent in the path
  	 * is before the requested block(s)
  	 */
  	if (b2 < b1) {
  		b2 = ext4_ext_next_allocated_block(path);
  		if (b2 == EXT_MAX_BLOCK)
  			goto out;
  	}
  
  	/* check for wrap through zero on extent logical start block*/
  	if (b1 + len1 < b1) {
  		len1 = EXT_MAX_BLOCK - b1;
  		newext->ee_len = cpu_to_le16(len1);
  		ret = 1;
  	}
  
  	/* check for overlap */
  	if (b1 + len1 > b2) {
  		newext->ee_len = cpu_to_le16(b2 - b1);
  		ret = 1;
  	}
  out:
  	return ret;
  }
  
  /*
   * 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(handle_t *handle, struct inode *inode,
  				struct ext4_ext_path *path,
  				struct ext4_extent *newext, int flag)
  {
  	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;
  	unsigned uninitialized = 0;
  
  	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;
  	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 && !(flag & EXT4_GET_BLOCKS_PRE_IO)
  		&& ext4_can_extents_be_merged(inode, ex, newext)) {
  		ext_debug("append [%d]%d block to %d:[%d]%d (from %llu)\n",
  				ext4_ext_is_uninitialized(newext),
  				ext4_ext_get_actual_len(newext),
  				le32_to_cpu(ex->ee_block),
  				ext4_ext_is_uninitialized(ex),
  				ext4_ext_get_actual_len(ex), ext_pblock(ex));
  		err = ext4_ext_get_access(handle, inode, path + depth);
  		if (err)
  			return err;
  
  		/*
  		 * ext4_can_extents_be_merged should have checked that either
  		 * both extents are uninitialized, or both aren't. Thus we
  		 * need to check only one of them here.
  		 */
  		if (ext4_ext_is_uninitialized(ex))
  			uninitialized = 1;
  		ex->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ex)
  					+ ext4_ext_get_actual_len(newext));
  		if (uninitialized)
  			ext4_ext_mark_uninitialized(ex);
  		eh = path[depth].p_hdr;
  		nearex = ex;
  		goto merge;
  	}
  
  repeat:
  	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 = ext4_ext_next_leaf_block(inode, path);
  	if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block)
  	    && next != EXT_MAX_BLOCK) {
  		ext_debug("next leaf block - %d\n", next);
  		BUG_ON(npath != NULL);
  		npath = ext4_ext_find_extent(inode, next, NULL);
  		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 isnt full(%d)\n",
  				  le16_to_cpu(eh->eh_entries));
  			path = npath;
  			goto repeat;
  		}
  		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.
  	 */
  	err = ext4_ext_create_new_leaf(handle, inode, path, 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(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: %d:%llu:[%d]%d\n",
  				le32_to_cpu(newext->ee_block),
  				ext_pblock(newext),
  				ext4_ext_is_uninitialized(newext),
  				ext4_ext_get_actual_len(newext));
  		path[depth].p_ext = EXT_FIRST_EXTENT(eh);
  	} else if (le32_to_cpu(newext->ee_block)
  			   > le32_to_cpu(nearex->ee_block)) {
  /*		BUG_ON(newext->ee_block == nearex->ee_block); */
  		if (nearex != EXT_LAST_EXTENT(eh)) {
  			len = EXT_MAX_EXTENT(eh) - nearex;
  			len = (len - 1) * sizeof(struct ext4_extent);
  			len = len < 0 ? 0 : len;
  			ext_debug("insert %d:%llu:[%d]%d after: nearest 0x%p, "
  					"move %d from 0x%p to 0x%p\n",
  					le32_to_cpu(newext->ee_block),
  					ext_pblock(newext),
  					ext4_ext_is_uninitialized(newext),
  					ext4_ext_get_actual_len(newext),
  					nearex, len, nearex + 1, nearex + 2);
  			memmove(nearex + 2, nearex + 1, len);
  		}
  		path[depth].p_ext = nearex + 1;
  	} else {
  		BUG_ON(newext->ee_block == nearex->ee_block);
  		len = (EXT_MAX_EXTENT(eh) - nearex) * sizeof(struct ext4_extent);
  		len = len < 0 ? 0 : len;
  		ext_debug("insert %d:%llu:[%d]%d before: nearest 0x%p, "
  				"move %d from 0x%p to 0x%p\n",
  				le32_to_cpu(newext->ee_block),
  				ext_pblock(newext),
  				ext4_ext_is_uninitialized(newext),
  				ext4_ext_get_actual_len(newext),
  				nearex, len, nearex + 1, nearex + 2);
  		memmove(nearex + 1, nearex, len);
  		path[depth].p_ext = nearex;
  	}
  
  	le16_add_cpu(&eh->eh_entries, 1);
  	nearex = path[depth].p_ext;
  	nearex->ee_block = newext->ee_block;
  	ext4_ext_store_pblock(nearex, ext_pblock(newext));
  	nearex->ee_len = newext->ee_len;
  
  merge:
  	/* try to merge extents to the right */
  	if (!(flag & EXT4_GET_BLOCKS_PRE_IO))
  		ext4_ext_try_to_merge(inode, path, nearex);
  
  	/* try to merge extents to the left */
  
  	/* time to correct all indexes above */
  	err = ext4_ext_correct_indexes(handle, inode, path);
  	if (err)
  		goto cleanup;
  
  	err = ext4_ext_dirty(handle, inode, path + depth);
  
  cleanup:
  	if (npath) {
  		ext4_ext_drop_refs(npath);
  		kfree(npath);
  	}
  	ext4_ext_invalidate_cache(inode);
  	return err;
  }
  
  int ext4_ext_walk_space(struct inode *inode, ext4_lblk_t block,
  			ext4_lblk_t num, ext_prepare_callback func,
  			void *cbdata)
  {
  	struct ext4_ext_path *path = NULL;
  	struct ext4_ext_cache cbex;
  	struct ext4_extent *ex;
  	ext4_lblk_t next, start = 0, end = 0;
  	ext4_lblk_t last = block + num;
  	int depth, exists, err = 0;
  
  	BUG_ON(func == NULL);
  	BUG_ON(inode == NULL);
  
  	while (block < last && block != EXT_MAX_BLOCK) {
  		num = last - block;
  		/* find extent for this block */
  		down_read(&EXT4_I(inode)->i_data_sem);
  		path = ext4_ext_find_extent(inode, block, path);
  		up_read(&EXT4_I(inode)->i_data_sem);
  		if (IS_ERR(path)) {
  			err = PTR_ERR(path);
  			path = NULL;
  			break;
  		}
  
  		depth = ext_depth(inode);
  		if (unlikely(path[depth].p_hdr == NULL)) {
  			EXT4_ERROR_INODE(inode, "path[%d].p_hdr == NULL", depth);
  			err = -EIO;
  			break;
  		}
  		ex = path[depth].p_ext;
  		next = ext4_ext_next_allocated_block(path);
  
  		exists = 0;
  		if (!ex) {
  			/* there is no extent yet, so try to allocate
  			 * all requested space */
  			start = block;
  			end = block + num;
  		} else if (le32_to_cpu(ex->ee_block) > block) {
  			/* need to allocate space before found extent */
  			start = block;
  			end = le32_to_cpu(ex->ee_block);
  			if (block + num < end)
  				end = block + num;
  		} else if (block >= le32_to_cpu(ex->ee_block)
  					+ ext4_ext_get_actual_len(ex)) {
  			/* need to allocate space after found extent */
  			start = block;
  			end = block + num;
  			if (end >= next)
  				end = next;
  		} else if (block >= le32_to_cpu(ex->ee_block)) {
  			/*
  			 * some part of requested space is covered
  			 * by found extent
  			 */
  			start = block;
  			end = le32_to_cpu(ex->ee_block)
  				+ ext4_ext_get_actual_len(ex);
  			if (block + num < end)
  				end = block + num;
  			exists = 1;
  		} else {
  			BUG();
  		}
  		BUG_ON(end <= start);
  
  		if (!exists) {
  			cbex.ec_block = start;
  			cbex.ec_len = end - start;
  			cbex.ec_start = 0;
  			cbex.ec_type = EXT4_EXT_CACHE_GAP;
  		} else {
  			cbex.ec_block = le32_to_cpu(ex->ee_block);
  			cbex.ec_len = ext4_ext_get_actual_len(ex);
  			cbex.ec_start = ext_pblock(ex);
  			cbex.ec_type = EXT4_EXT_CACHE_EXTENT;
  		}
  
  		if (unlikely(cbex.ec_len == 0)) {
  			EXT4_ERROR_INODE(inode, "cbex.ec_len == 0");
  			err = -EIO;
  			break;
  		}
  		err = func(inode, path, &cbex, ex, cbdata);
  		ext4_ext_drop_refs(path);
  
  		if (err < 0)
  			break;
  
  		if (err == EXT_REPEAT)
  			continue;
  		else if (err == EXT_BREAK) {
  			err = 0;
  			break;
  		}
  
  		if (ext_depth(inode) != depth) {
  			/* depth was changed. we have to realloc path */
  			kfree(path);
  			path = NULL;
  		}
  
  		block = cbex.ec_block + cbex.ec_len;
  	}
  
  	if (path) {
  		ext4_ext_drop_refs(path);
  		kfree(path);
  	}
  
  	return err;
  }
  
  static void
  ext4_ext_put_in_cache(struct inode *inode, ext4_lblk_t block,
  			__u32 len, ext4_fsblk_t start, int type)
  {
  	struct ext4_ext_cache *cex;
  	BUG_ON(len == 0);
  	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
  	cex = &EXT4_I(inode)->i_cached_extent;
  	cex->ec_type = type;
  	cex->ec_block = block;
  	cex->ec_len = len;
  	cex->ec_start = start;
  	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
  }
  
  /*
   * ext4_ext_put_gap_in_cache:
   * calculate boundaries of the gap that the requested block fits into
   * and cache this gap
   */
  static void
  ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
  				ext4_lblk_t block)
  {
  	int depth = ext_depth(inode);
  	unsigned long len;
  	ext4_lblk_t lblock;
  	struct ext4_extent *ex;
  
  	ex = path[depth].p_ext;
  	if (ex == NULL) {
  		/* there is no extent yet, so gap is [0;-] */
  		lblock = 0;
  		len = EXT_MAX_BLOCK;
  		ext_debug("cache gap(whole file):");
  	} else if (block < le32_to_cpu(ex->ee_block)) {
  		lblock = block;
  		len = le32_to_cpu(ex->ee_block) - block;
  		ext_debug("cache gap(before): %u [%u:%u]",
  				block,
  				le32_to_cpu(ex->ee_block),
  				 ext4_ext_get_actual_len(ex));
  	} else if (block >= le32_to_cpu(ex->ee_block)
  			+ ext4_ext_get_actual_len(ex)) {
  		ext4_lblk_t next;
  		lblock = le32_to_cpu(ex->ee_block)
  			+ ext4_ext_get_actual_len(ex);
  
  		next = ext4_ext_next_allocated_block(path);
  		ext_debug("cache gap(after): [%u:%u] %u",
  				le32_to_cpu(ex->ee_block),
  				ext4_ext_get_actual_len(ex),
  				block);
  		BUG_ON(next == lblock);
  		len = next - lblock;
  	} else {
  		lblock = len = 0;
  		BUG();
  	}
  
  	ext_debug(" -> %u:%lu\n", lblock, len);
  	ext4_ext_put_in_cache(inode, lblock, len, 0, EXT4_EXT_CACHE_GAP);
  }
  
  static int
  ext4_ext_in_cache(struct inode *inode, ext4_lblk_t block,
  			struct ext4_extent *ex)
  {
  	struct ext4_ext_cache *cex;
  	int ret = EXT4_EXT_CACHE_NO;
  
  	/*
  	 * We borrow i_block_reservation_lock to protect i_cached_extent
  	 */
  	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
  	cex = &EXT4_I(inode)->i_cached_extent;
  
  	/* has cache valid data? */
  	if (cex->ec_type == EXT4_EXT_CACHE_NO)
  		goto errout;
  
  	BUG_ON(cex->ec_type != EXT4_EXT_CACHE_GAP &&
  			cex->ec_type != EXT4_EXT_CACHE_EXTENT);
  	if (in_range(block, cex->ec_block, cex->ec_len)) {
  		ex->ee_block = cpu_to_le32(cex->ec_block);
  		ext4_ext_store_pblock(ex, cex->ec_start);
  		ex->ee_len = cpu_to_le16(cex->ec_len);
  		ext_debug("%u cached by %u:%u:%llu\n",
  				block,
  				cex->ec_block, cex->ec_len, cex->ec_start);
  		ret = cex->ec_type;
  	}
  errout:
  	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
  	return ret;
  }
  
  /*
   * ext4_ext_rm_idx:
   * removes index from the index block.
   * It's used in truncate case only, thus all requests are for
   * last index in the block only.
   */
  static int ext4_ext_rm_idx(handle_t *handle, struct inode *inode,
  			struct ext4_ext_path *path)
  {
  	int err;
  	ext4_fsblk_t leaf;
  
  	/* free index block */
  	path--;
  	leaf = idx_pblock(path->p_idx);
  	if (unlikely(path->p_hdr->eh_entries == 0)) {
  		EXT4_ERROR_INODE(inode, "path->p_hdr->eh_entries == 0");
  		return -EIO;
  	}
  	err = ext4_ext_get_access(handle, inode, path);
  	if (err)
  		return err;
  	le16_add_cpu(&path->p_hdr->eh_entries, -1);
  	err = ext4_ext_dirty(handle, inode, path);
  	if (err)
  		return err;
  	ext_debug("index is empty, remove it, free block %llu\n", leaf);
  	ext4_free_blocks(handle, inode, 0, leaf, 1,
  			 EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET);
  	return err;
  }
  
  /*
   * ext4_ext_calc_credits_for_single_extent:
   * This routine returns max. credits that needed to insert an extent
   * to the extent tree.
   * When pass the actual path, the caller should calculate credits
   * under i_data_sem.
   */
  int ext4_ext_calc_credits_for_single_extent(struct inode *inode, int nrblocks,
  						struct ext4_ext_path *path)
  {
  	if (path) {
  		int depth = ext_depth(inode);
  		int ret = 0;
  
  		/* probably there is space in leaf? */
  		if (le16_to_cpu(path[depth].p_hdr->eh_entries)
  				< le16_to_cpu(path[depth].p_hdr->eh_max)) {
  
  			/*
  			 *  There are some space in the leaf tree, no
  			 *  need to account for leaf block credit
  			 *
  			 *  bitmaps and block group descriptor blocks
  			 *  and other metadat blocks still need to be
  			 *  accounted.
  			 */
  			/* 1 bitmap, 1 block group descriptor */
  			ret = 2 + EXT4_META_TRANS_BLOCKS(inode->i_sb);
  			return ret;
  		}
  	}
  
  	return ext4_chunk_trans_blocks(inode, nrblocks);
  }
  
  /*
   * How many index/leaf blocks need to change/allocate to modify nrblocks?
   *
   * if nrblocks are fit in a single extent (chunk flag is 1), then
   * in the worse case, each tree level index/leaf need to be changed
   * if the tree split due to insert a new extent, then the old tree
   * index/leaf need to be updated too
   *
   * If the nrblocks are discontiguous, they could cause
   * the whole tree split more than once, but this is really rare.
   */
  int ext4_ext_index_trans_blocks(struct inode *inode, int nrblocks, int chunk)
  {
  	int index;
  	int depth = ext_depth(inode);
  
  	if (chunk)
  		index = depth * 2;
  	else
  		index = depth * 3;
  
  	return index;
  }
  
  static int ext4_remove_blocks(handle_t *handle, struct inode *inode,
  				struct ext4_extent *ex,
  				ext4_lblk_t from, ext4_lblk_t to)
  {
  	unsigned short ee_len =  ext4_ext_get_actual_len(ex);
  	int flags = EXT4_FREE_BLOCKS_FORGET;
  
  	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
  		flags |= EXT4_FREE_BLOCKS_METADATA;
  #ifdef EXTENTS_STATS
  	{
  		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  		spin_lock(&sbi->s_ext_stats_lock);
  		sbi->s_ext_blocks += ee_len;
  		sbi->s_ext_extents++;
  		if (ee_len < sbi->s_ext_min)
  			sbi->s_ext_min = ee_len;
  		if (ee_len > sbi->s_ext_max)
  			sbi->s_ext_max = ee_len;
  		if (ext_depth(inode) > sbi->s_depth_max)
  			sbi->s_depth_max = ext_depth(inode);
  		spin_unlock(&sbi->s_ext_stats_lock);
  	}
  #endif
  	if (from >= le32_to_cpu(ex->ee_block)
  	    && to == le32_to_cpu(ex->ee_block) + ee_len - 1) {
  		/* tail removal */
  		ext4_lblk_t num;
  		ext4_fsblk_t start;
  
  		num = le32_to_cpu(ex->ee_block) + ee_len - from;
  		start = ext_pblock(ex) + ee_len - num;
  		ext_debug("free last %u blocks starting %llu\n", num, start);
  		ext4_free_blocks(handle, inode, 0, start, num, flags);
  	} else if (from == le32_to_cpu(ex->ee_block)
  		   && to <= le32_to_cpu(ex->ee_block) + ee_len - 1) {
  		printk(KERN_INFO "strange request: removal %u-%u from %u:%u\n",
  			from, to, le32_to_cpu(ex->ee_block), ee_len);
  	} else {
  		printk(KERN_INFO "strange request: removal(2) "
  				"%u-%u from %u:%u\n",
  				from, to, le32_to_cpu(ex->ee_block), ee_len);
  	}
  	return 0;
  }
  
  static int
  ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
  		struct ext4_ext_path *path, ext4_lblk_t start)
  {
  	int err = 0, correct_index = 0;
  	int depth = ext_depth(inode), credits;
  	struct ext4_extent_header *eh;
  	ext4_lblk_t a, b, block;
  	unsigned num;
  	ext4_lblk_t ex_ee_block;
  	unsigned short ex_ee_len;
  	unsigned uninitialized = 0;
  	struct ext4_extent *ex;
  
  	/* the header must be checked already in ext4_ext_remove_space() */
  	ext_debug("truncate since %u in leaf\n", start);
  	if (!path[depth].p_hdr)
  		path[depth].p_hdr = ext_block_hdr(path[depth].p_bh);
  	eh = path[depth].p_hdr;
  	if (unlikely(path[depth].p_hdr == NULL)) {
  		EXT4_ERROR_INODE(inode, "path[%d].p_hdr == NULL", depth);
  		return -EIO;
  	}
  	/* 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) {
  
  		if (ext4_ext_is_uninitialized(ex))
  			uninitialized = 1;
  		else
  			uninitialized = 0;
  
  		ext_debug("remove ext %u:[%d]%d\n", ex_ee_block,
  			 uninitialized, ex_ee_len);
  		path[depth].p_ext = ex;
  
  		a = ex_ee_block > start ? ex_ee_block : start;
  		b = ex_ee_block + ex_ee_len - 1 < EXT_MAX_BLOCK ?
  			ex_ee_block + ex_ee_len - 1 : EXT_MAX_BLOCK;
  
  		ext_debug("  border %u:%u\n", a, b);
  
  		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);
  		}
  
  		/*
  		 * 3 for leaf, sb, and inode plus 2 (bmap and group
  		 * descriptor) for each block group; assume two block
  		 * groups plus ex_ee_len/blocks_per_block_group for
  		 * the worst case
  		 */
  		credits = 7 + 2*(ex_ee_len/EXT4_BLOCKS_PER_GROUP(inode->i_sb));
  		if (ex == EXT_FIRST_EXTENT(eh)) {
  			correct_index = 1;
  			credits += (ext_depth(inode)) + 1;
  		}
  		credits += EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb);
  
  		err = ext4_ext_truncate_extend_restart(handle, inode, credits);
  		if (err)
  			goto out;
  
  		err = ext4_ext_get_access(handle, inode, path + depth);
  		if (err)
  			goto out;
  
  		err = ext4_remove_blocks(handle, inode, ex, a, b);
  		if (err)
  			goto out;
  
  		if (num == 0) {
  			/* this extent is removed; mark slot entirely unused */
  			ext4_ext_store_pblock(ex, 0);
  			le16_add_cpu(&eh->eh_entries, -1);
  		}
  
  		ex->ee_block = cpu_to_le32(block);
  		ex->ee_len = cpu_to_le16(num);
  		/*
  		 * Do not mark uninitialized if all the blocks in the
  		 * extent have been removed.
  		 */
  		if (uninitialized && num)
  			ext4_ext_mark_uninitialized(ex);
  
  		err = ext4_ext_dirty(handle, inode, path + depth);
  		if (err)
  			goto out;
  
  		ext_debug("new extent: %u:%u:%llu\n", block, num,
  				ext_pblock(ex));
  		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(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(handle, inode, path + depth);
  
  out:
  	return err;
  }
  
  /*
   * ext4_ext_more_to_rm:
   * returns 1 if current index has to be freed (even partial)
   */
  static 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 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;
  }
  
  static int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start)
  {
  	struct super_block *sb = inode->i_sb;
  	int depth = ext_depth(inode);
  	struct ext4_ext_path *path;
  	handle_t *handle;
  	int i, err;
  
  	ext_debug("truncate since %u\n", start);
  
  	/* probably first extent we're gonna free will be last in block */
  	handle = ext4_journal_start(inode, depth + 1);
  	if (IS_ERR(handle))
  		return PTR_ERR(handle);
  
  again:
  	ext4_ext_invalidate_cache(inode);
  
  	/*
  	 * We start scanning from right side, freeing all the blocks
  	 * after i_size and walking into the tree depth-wise.
  	 */
  	depth = ext_depth(inode);
  	path = kzalloc(sizeof(struct ext4_ext_path) * (depth + 1), GFP_NOFS);
  	if (path == NULL) {
  		ext4_journal_stop(handle);
  		return -ENOMEM;
  	}
  	path[0].p_depth = depth;
  	path[0].p_hdr = ext_inode_hdr(inode);
  	if (ext4_ext_check(inode, path[0].p_hdr, depth)) {
  		err = -EIO;
  		goto out;
  	}
  	i = err = 0;
  
  	while (i >= 0 && err == 0) {
  		if (i == depth) {
  			/* this is leaf block */
  			err = ext4_ext_rm_leaf(handle, inode, path, start);
  			/* root level has p_bh == NULL, brelse() eats this */
  			brelse(path[i].p_bh);
  			path[i].p_bh = NULL;
  			i--;
  			continue;
  		}
  
  		/* this is index block */
  		if (!path[i].p_hdr) {
  			ext_debug("initialize header\n");
  			path[i].p_hdr = ext_block_hdr(path[i].p_bh);
  		}
  
  		if (!path[i].p_idx) {
  			/* this level hasn't been 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;
  			ext_debug("init index ptr: hdr 0x%p, num %d\n",
  				  path[i].p_hdr,
  				  le16_to_cpu(path[i].p_hdr->eh_entries));
  		} else {
  			/* we were already here, see at next index */
  			path[i].p_idx--;
  		}
  
  		ext_debug("level %d - index, first 0x%p, cur 0x%p\n",
  				i, EXT_FIRST_INDEX(path[i].p_hdr),
  				path[i].p_idx);
  		if (ext4_ext_more_to_rm(path + i)) {
  			struct buffer_head *bh;
  			/* go to the next level */
  			ext_debug("move to level %d (block %llu)\n",
  				  i + 1, idx_pblock(path[i].p_idx));
  			memset(path + i + 1, 0, sizeof(*path));
  			bh = sb_bread(sb, idx_pblock(path[i].p_idx));
  			if (!bh) {
  				/* should we reset i_size? */
  				err = -EIO;
  				break;
  			}
  			if (WARN_ON(i + 1 > depth)) {
  				err = -EIO;
  				break;
  			}
  			if (ext4_ext_check(inode, ext_block_hdr(bh),
  							depth - i - 1)) {
  				err = -EIO;
  				break;
  			}
  			path[i + 1].p_bh = bh;
  
  			/* save actual number of indexes since this
  			 * number is changed at the next iteration */
  			path[i].p_block = le16_to_cpu(path[i].p_hdr->eh_entries);
  			i++;
  		} else {
  			/* we finished 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(handle, inode, path + i);
  			}
  			/* root level has p_bh == NULL, brelse() eats this */
  			brelse(path[i].p_bh);
  			path[i].p_bh = NULL;
  			i--;
  			ext_debug("return to level %d\n", 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(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(handle, inode, path);
  		}
  	}
  out:
  	ext4_ext_drop_refs(path);
  	kfree(path);
  	if (err == -EAGAIN)
  		goto again;
  	ext4_journal_stop(handle);
  
  	return err;
  }
  
  /*
   * called at mount time
   */
  void ext4_ext_init(struct super_block *sb)
  {
  	/*
  	 * possible initialization would be here
  	 */
  
  	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS)) {
  #if defined(AGGRESSIVE_TEST) || defined(CHECK_BINSEARCH) || defined(EXTENTS_STATS)
  		printk(KERN_INFO "EXT4-fs: file extents enabled");
  #ifdef AGGRESSIVE_TEST
  		printk(", aggressive tests");
  #endif
  #ifdef CHECK_BINSEARCH
  		printk(", check binsearch");
  #endif
  #ifdef EXTENTS_STATS
  		printk(", stats");
  #endif
  		printk("\n");
  #endif
  #ifdef EXTENTS_STATS
  		spin_lock_init(&EXT4_SB(sb)->s_ext_stats_lock);
  		EXT4_SB(sb)->s_ext_min = 1 << 30;
  		EXT4_SB(sb)->s_ext_max = 0;
  #endif
  	}
  }
  
  /*
   * called at umount time
   */
  void ext4_ext_release(struct super_block *sb)
  {
  	if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS))
  		return;
  
  #ifdef EXTENTS_STATS
  	if (EXT4_SB(sb)->s_ext_blocks && EXT4_SB(sb)->s_ext_extents) {
  		struct ext4_sb_info *sbi = EXT4_SB(sb);
  		printk(KERN_ERR "EXT4-fs: %lu blocks in %lu extents (%lu ave)\n",
  			sbi->s_ext_blocks, sbi->s_ext_extents,
  			sbi->s_ext_blocks / sbi->s_ext_extents);
  		printk(KERN_ERR "EXT4-fs: extents: %lu min, %lu max, max depth %lu\n",
  			sbi->s_ext_min, sbi->s_ext_max, sbi->s_depth_max);
  	}
  #endif
  }
  
  static void bi_complete(struct bio *bio, int error)
  {
  	complete((struct completion *)bio->bi_private);
  }
  
  /* 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)
  {
  	int ret;
  	struct bio *bio;
  	int blkbits, blocksize;
  	sector_t ee_pblock;
  	struct completion event;
  	unsigned int ee_len, len, done, offset;
  
  
  	blkbits   = inode->i_blkbits;
  	blocksize = inode->i_sb->s_blocksize;
  	ee_len    = ext4_ext_get_actual_len(ex);
  	ee_pblock = ext_pblock(ex);
  
  	/* convert ee_pblock to 512 byte sectors */
  	ee_pblock = ee_pblock << (blkbits - 9);
  
  	while (ee_len > 0) {
  
  		if (ee_len > BIO_MAX_PAGES)
  			len = BIO_MAX_PAGES;
  		else
  			len = ee_len;
  
  		bio = bio_alloc(GFP_NOIO, len);
  		if (!bio)
  			return -ENOMEM;
  
  		bio->bi_sector = ee_pblock;
  		bio->bi_bdev   = inode->i_sb->s_bdev;
  
  		done = 0;
  		offset = 0;
  		while (done < len) {
  			ret = bio_add_page(bio, ZERO_PAGE(0),
  							blocksize, offset);
  			if (ret != blocksize) {
  				/*
  				 * We can't add any more pages because of
  				 * hardware limitations.  Start a new bio.
  				 */
  				break;
  			}
  			done++;
  			offset += blocksize;
  			if (offset >= PAGE_CACHE_SIZE)
  				offset = 0;
  		}
  
  		init_completion(&event);
  		bio->bi_private = &event;
  		bio->bi_end_io = bi_complete;
  		submit_bio(WRITE, bio);
  		wait_for_completion(&event);
  
  		if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) {
  			bio_put(bio);
  			return -EIO;
  		}
  		bio_put(bio);
  		ee_len    -= done;
  		ee_pblock += done  << (blkbits - 9);
  	}
  	return 0;
  }
  
  #define EXT4_EXT_ZERO_LEN 7
  /*
   * This function is called by ext4_ext_map_blocks() if someone tries to write
   * to an uninitialized extent. It may result in splitting the uninitialized
   * extent into multiple extents (upto three - one initialized and two
   * uninitialized).
   * There are three possibilities:
   *   a> There is no split required: Entire extent should be initialized
   *   b> Splits in two extents: Write is happening at either end of the extent
   *   c> Splits in three extents: Somone is writing in middle of the extent
   */
  static int ext4_ext_convert_to_initialized(handle_t *handle,
  					   struct inode *inode,
  					   struct ext4_map_blocks *map,
  					   struct ext4_ext_path *path)
  {
  	struct ext4_extent *ex, newex, orig_ex;
  	struct ext4_extent *ex1 = NULL;
  	struct ext4_extent *ex2 = NULL;
  	struct ext4_extent *ex3 = NULL;
  	struct ext4_extent_header *eh;
  	ext4_lblk_t ee_block, eof_block;
  	unsigned int allocated, ee_len, depth;
  	ext4_fsblk_t newblock;
  	int err = 0;
  	int ret = 0;
  	int may_zeroout;
  
  	ext_debug("ext4_ext_convert_to_initialized: inode %lu, logical"
  		"block %llu, max_blocks %u\n", inode->i_ino,
  		(unsigned long long)map->m_lblk, map->m_len);
  
  	eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
  		inode->i_sb->s_blocksize_bits;
  	if (eof_block < map->m_lblk + map->m_len)
  		eof_block = map->m_lblk + map->m_len;
  
  	depth = ext_depth(inode);
  	eh = path[depth].p_hdr;
  	ex = path[depth].p_ext;
  	ee_block = le32_to_cpu(ex->ee_block);
  	ee_len = ext4_ext_get_actual_len(ex);
  	allocated = ee_len - (map->m_lblk - ee_block);
  	newblock = map->m_lblk - ee_block + ext_pblock(ex);
  
  	ex2 = ex;
  	orig_ex.ee_block = ex->ee_block;
  	orig_ex.ee_len   = cpu_to_le16(ee_len);
  	ext4_ext_store_pblock(&orig_ex, ext_pblock(ex));
  
  	/*
  	 * It is safe to convert extent to initialized via explicit
  	 * zeroout only if extent is fully insde i_size or new_size.
  	 */
  	may_zeroout = ee_block + ee_len <= eof_block;
  
  	err = ext4_ext_get_access(handle, inode, path + depth);
  	if (err)
  		goto out;
  	/* If extent has less than 2*EXT4_EXT_ZERO_LEN zerout directly */
  	if (ee_len <= 2*EXT4_EXT_ZERO_LEN && may_zeroout) {
  		err =  ext4_ext_zeroout(inode, &orig_ex);
  		if (err)
  			goto fix_extent_len;
  		/* update the extent length and mark as initialized */
  		ex->ee_block = orig_ex.ee_block;
  		ex->ee_len   = orig_ex.ee_len;
  		ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  		ext4_ext_dirty(handle, inode, path + depth);
  		/* zeroed the full extent */
  		return allocated;
  	}
  
  	/* ex1: ee_block to map->m_lblk - 1 : uninitialized */
  	if (map->m_lblk > ee_block) {
  		ex1 = ex;
  		ex1->ee_len = cpu_to_le16(map->m_lblk - ee_block);
  		ext4_ext_mark_uninitialized(ex1);
  		ex2 = &newex;
  	}
  	/*
  	 * for sanity, update the length of the ex2 extent before
  	 * we insert ex3, if ex1 is NULL. This is to avoid temporary
  	 * overlap of blocks.
  	 */
  	if (!ex1 && allocated > map->m_len)
  		ex2->ee_len = cpu_to_le16(map->m_len);
  	/* ex3: to ee_block + ee_len : uninitialised */
  	if (allocated > map->m_len) {
  		unsigned int newdepth;
  		/* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */
  		if (allocated <= EXT4_EXT_ZERO_LEN && may_zeroout) {
  			/*
  			 * map->m_lblk == ee_block is handled by the zerouout
  			 * at the beginning.
  			 * Mark first half uninitialized.
  			 * Mark second half initialized and zero out the
  			 * initialized extent
  			 */
  			ex->ee_block = orig_ex.ee_block;
  			ex->ee_len   = cpu_to_le16(ee_len - allocated);
  			ext4_ext_mark_uninitialized(ex);
  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  			ext4_ext_dirty(handle, inode, path + depth);
  
  			ex3 = &newex;
  			ex3->ee_block = cpu_to_le32(map->m_lblk);
  			ext4_ext_store_pblock(ex3, newblock);
  			ex3->ee_len = cpu_to_le16(allocated);
  			err = ext4_ext_insert_extent(handle, inode, path,
  							ex3, 0);
  			if (err == -ENOSPC) {
  				err =  ext4_ext_zeroout(inode, &orig_ex);
  				if (err)
  					goto fix_extent_len;
  				ex->ee_block = orig_ex.ee_block;
  				ex->ee_len   = orig_ex.ee_len;
  				ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  				ext4_ext_dirty(handle, inode, path + depth);
  				/* blocks available from map->m_lblk */
  				return allocated;
  
  			} else if (err)
  				goto fix_extent_len;
  
  			/*
  			 * We need to zero out the second half because
  			 * an fallocate request can update file size and
  			 * converting the second half to initialized extent
  			 * implies that we can leak some junk data to user
  			 * space.
  			 */
  			err =  ext4_ext_zeroout(inode, ex3);
  			if (err) {
  				/*
  				 * We should actually mark the
  				 * second half as uninit and return error
  				 * Insert would have changed the extent
  				 */
  				depth = ext_depth(inode);
  				ext4_ext_drop_refs(path);
  				path = ext4_ext_find_extent(inode, map->m_lblk,
  							    path);
  				if (IS_ERR(path)) {
  					err = PTR_ERR(path);
  					return err;
  				}
  				/* get the second half extent details */
  				ex = path[depth].p_ext;
  				err = ext4_ext_get_access(handle, inode,
  								path + depth);
  				if (err)
  					return err;
  				ext4_ext_mark_uninitialized(ex);
  				ext4_ext_dirty(handle, inode, path + depth);
  				return err;
  			}
  
  			/* zeroed the second half */
  			return allocated;
  		}
  		ex3 = &newex;
  		ex3->ee_block = cpu_to_le32(map->m_lblk + map->m_len);
  		ext4_ext_store_pblock(ex3, newblock + map->m_len);
  		ex3->ee_len = cpu_to_le16(allocated - map->m_len);
  		ext4_ext_mark_uninitialized(ex3);
  		err = ext4_ext_insert_extent(handle, inode, path, ex3, 0);
  		if (err == -ENOSPC && may_zeroout) {
  			err =  ext4_ext_zeroout(inode, &orig_ex);
  			if (err)
  				goto fix_extent_len;
  			/* update the extent length and mark as initialized */
  			ex->ee_block = orig_ex.ee_block;
  			ex->ee_len   = orig_ex.ee_len;
  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  			ext4_ext_dirty(handle, inode, path + depth);
  			/* zeroed the full extent */
  			/* blocks available from map->m_lblk */
  			return allocated;
  
  		} else if (err)
  			goto fix_extent_len;
  		/*
  		 * The depth, and hence eh & ex might change
  		 * as part of the insert above.
  		 */
  		newdepth = ext_depth(inode);
  		/*
  		 * update the extent length after successful insert of the
  		 * split extent
  		 */
  		ee_len -= ext4_ext_get_actual_len(ex3);
  		orig_ex.ee_len = cpu_to_le16(ee_len);
  		may_zeroout = ee_block + ee_len <= eof_block;
  
  		depth = newdepth;
  		ext4_ext_drop_refs(path);
  		path = ext4_ext_find_extent(inode, map->m_lblk, path);
  		if (IS_ERR(path)) {
  			err = PTR_ERR(path);
  			goto out;
  		}
  		eh = path[depth].p_hdr;
  		ex = path[depth].p_ext;
  		if (ex2 != &newex)
  			ex2 = ex;
  
  		err = ext4_ext_get_access(handle, inode, path + depth);
  		if (err)
  			goto out;
  
  		allocated = map->m_len;
  
  		/* If extent has less than EXT4_EXT_ZERO_LEN and we are trying
  		 * to insert a extent in the middle zerout directly
  		 * otherwise give the extent a chance to merge to left
  		 */
  		if (le16_to_cpu(orig_ex.ee_len) <= EXT4_EXT_ZERO_LEN &&
  			map->m_lblk != ee_block && may_zeroout) {
  			err =  ext4_ext_zeroout(inode, &orig_ex);
  			if (err)
  				goto fix_extent_len;
  			/* update the extent length and mark as initialized */
  			ex->ee_block = orig_ex.ee_block;
  			ex->ee_len   = orig_ex.ee_len;
  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  			ext4_ext_dirty(handle, inode, path + depth);
  			/* zero out the first half */
  			/* blocks available from map->m_lblk */
  			return allocated;
  		}
  	}
  	/*
  	 * If there was a change of depth as part of the
  	 * insertion of ex3 above, we need to update the length
  	 * of the ex1 extent again here
  	 */
  	if (ex1 && ex1 != ex) {
  		ex1 = ex;
  		ex1->ee_len = cpu_to_le16(map->m_lblk - ee_block);
  		ext4_ext_mark_uninitialized(ex1);
  		ex2 = &newex;
  	}
  	/* ex2: map->m_lblk to map->m_lblk + maxblocks-1 : initialised */
  	ex2->ee_block = cpu_to_le32(map->m_lblk);
  	ext4_ext_store_pblock(ex2, newblock);
  	ex2->ee_len = cpu_to_le16(allocated);
  	if (ex2 != ex)
  		goto insert;
  	/*
  	 * New (initialized) extent starts from the first block
  	 * in the current extent. i.e., ex2 == ex
  	 * We have to see if it can be merged with the extent
  	 * on the left.
  	 */
  	if (ex2 > EXT_FIRST_EXTENT(eh)) {
  		/*
  		 * To merge left, pass "ex2 - 1" to try_to_merge(),
  		 * since it merges towards right _only_.
  		 */
  		ret = ext4_ext_try_to_merge(inode, path, ex2 - 1);
  		if (ret) {
  			err = ext4_ext_correct_indexes(handle, inode, path);
  			if (err)
  				goto out;
  			depth = ext_depth(inode);
  			ex2--;
  		}
  	}
  	/*
  	 * Try to Merge towards right. This might be required
  	 * only when the whole extent is being written to.
  	 * i.e. ex2 == ex and ex3 == NULL.
  	 */
  	if (!ex3) {
  		ret = ext4_ext_try_to_merge(inode, path, ex2);
  		if (ret) {
  			err = ext4_ext_correct_indexes(handle, inode, path);
  			if (err)
  				goto out;
  		}
  	}
  	/* Mark modified extent as dirty */
  	err = ext4_ext_dirty(handle, inode, path + depth);
  	goto out;
  insert:
  	err = ext4_ext_insert_extent(handle, inode, path, &newex, 0);
  	if (err == -ENOSPC && may_zeroout) {
  		err =  ext4_ext_zeroout(inode, &orig_ex);
  		if (err)
  			goto fix_extent_len;
  		/* update the extent length and mark as initialized */
  		ex->ee_block = orig_ex.ee_block;
  		ex->ee_len   = orig_ex.ee_len;
  		ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  		ext4_ext_dirty(handle, inode, path + depth);
  		/* zero out the first half */
  		return allocated;
  	} else if (err)
  		goto fix_extent_len;
  out:
  	ext4_ext_show_leaf(inode, path);
  	return err ? err : allocated;
  
  fix_extent_len:
  	ex->ee_block = orig_ex.ee_block;
  	ex->ee_len   = orig_ex.ee_len;
  	ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  	ext4_ext_mark_uninitialized(ex);
  	ext4_ext_dirty(handle, inode, path + depth);
  	return err;
  }
  
  /*
   * This function is called by ext4_ext_map_blocks() from
   * ext4_get_blocks_dio_write() when DIO to write
   * to an uninitialized extent.
   *
   * Writing to an uninitized extent may result in splitting the uninitialized
   * extent into multiple /intialized unintialized extents (up to three)
   * There are three possibilities:
   *   a> There is no split required: Entire extent should be uninitialized
   *   b> Splits in two extents: Write is happening at either end of the extent
   *   c> Splits in three extents: Somone is writing in middle of the extent
   *
   * One of more index blocks maybe needed if the extent tree grow after
   * the unintialized extent split. To prevent ENOSPC occur at the IO
   * complete, we need to split the uninitialized extent before DIO submit
   * the IO. The uninitialized extent called at this time will be split
   * into three uninitialized extent(at most). After IO complete, the part
   * being filled will be convert to initialized by the end_io callback function
   * via ext4_convert_unwritten_extents().
   *
   * Returns the size of uninitialized extent to be written on success.
   */
  static int ext4_split_unwritten_extents(handle_t *handle,
  					struct inode *inode,
  					struct ext4_map_blocks *map,
  					struct ext4_ext_path *path,
  					int flags)
  {
  	struct ext4_extent *ex, newex, orig_ex;
  	struct ext4_extent *ex1 = NULL;
  	struct ext4_extent *ex2 = NULL;
  	struct ext4_extent *ex3 = NULL;
  	ext4_lblk_t ee_block, eof_block;
  	unsigned int allocated, ee_len, depth;
  	ext4_fsblk_t newblock;
  	int err = 0;
  	int may_zeroout;
  
  	ext_debug("ext4_split_unwritten_extents: inode %lu, logical"
  		"block %llu, max_blocks %u\n", inode->i_ino,
  		(unsigned long long)map->m_lblk, map->m_len);
  
  	eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
  		inode->i_sb->s_blocksize_bits;
  	if (eof_block < map->m_lblk + map->m_len)
  		eof_block = map->m_lblk + map->m_len;
  
  	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);
  	allocated = ee_len - (map->m_lblk - ee_block);
  	newblock = map->m_lblk - ee_block + ext_pblock(ex);
  
  	ex2 = ex;
  	orig_ex.ee_block = ex->ee_block;
  	orig_ex.ee_len   = cpu_to_le16(ee_len);
  	ext4_ext_store_pblock(&orig_ex, ext_pblock(ex));
  
  	/*
  	 * It is safe to convert extent to initialized via explicit
  	 * zeroout only if extent is fully insde i_size or new_size.
  	 */
  	may_zeroout = ee_block + ee_len <= eof_block;
  
  	/*
   	 * If the uninitialized extent begins at the same logical
   	 * block where the write begins, and the write completely
   	 * covers the extent, then we don't need to split it.
   	 */
  	if ((map->m_lblk == ee_block) && (allocated <= map->m_len))
  		return allocated;
  
  	err = ext4_ext_get_access(handle, inode, path + depth);
  	if (err)
  		goto out;
  	/* ex1: ee_block to map->m_lblk - 1 : uninitialized */
  	if (map->m_lblk > ee_block) {
  		ex1 = ex;
  		ex1->ee_len = cpu_to_le16(map->m_lblk - ee_block);
  		ext4_ext_mark_uninitialized(ex1);
  		ex2 = &newex;
  	}
  	/*
  	 * for sanity, update the length of the ex2 extent before
  	 * we insert ex3, if ex1 is NULL. This is to avoid temporary
  	 * overlap of blocks.
  	 */
  	if (!ex1 && allocated > map->m_len)
  		ex2->ee_len = cpu_to_le16(map->m_len);
  	/* ex3: to ee_block + ee_len : uninitialised */
  	if (allocated > map->m_len) {
  		unsigned int newdepth;
  		ex3 = &newex;
  		ex3->ee_block = cpu_to_le32(map->m_lblk + map->m_len);
  		ext4_ext_store_pblock(ex3, newblock + map->m_len);
  		ex3->ee_len = cpu_to_le16(allocated - map->m_len);
  		ext4_ext_mark_uninitialized(ex3);
  		err = ext4_ext_insert_extent(handle, inode, path, ex3, flags);
  		if (err == -ENOSPC && may_zeroout) {
  			err =  ext4_ext_zeroout(inode, &orig_ex);
  			if (err)
  				goto fix_extent_len;
  			/* update the extent length and mark as initialized */
  			ex->ee_block = orig_ex.ee_block;
  			ex->ee_len   = orig_ex.ee_len;
  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  			ext4_ext_dirty(handle, inode, path + depth);
  			/* zeroed the full extent */
  			/* blocks available from map->m_lblk */
  			return allocated;
  
  		} else if (err)
  			goto fix_extent_len;
  		/*
  		 * The depth, and hence eh & ex might change
  		 * as part of the insert above.
  		 */
  		newdepth = ext_depth(inode);
  		/*
  		 * update the extent length after successful insert of the
  		 * split extent
  		 */
  		ee_len -= ext4_ext_get_actual_len(ex3);
  		orig_ex.ee_len = cpu_to_le16(ee_len);
  		may_zeroout = ee_block + ee_len <= eof_block;
  
  		depth = newdepth;
  		ext4_ext_drop_refs(path);
  		path = ext4_ext_find_extent(inode, map->m_lblk, path);
  		if (IS_ERR(path)) {
  			err = PTR_ERR(path);
  			goto out;
  		}
  		ex = path[depth].p_ext;
  		if (ex2 != &newex)
  			ex2 = ex;
  
  		err = ext4_ext_get_access(handle, inode, path + depth);
  		if (err)
  			goto out;
  
  		allocated = map->m_len;
  	}
  	/*
  	 * If there was a change of depth as part of the
  	 * insertion of ex3 above, we need to update the length
  	 * of the ex1 extent again here
  	 */
  	if (ex1 && ex1 != ex) {
  		ex1 = ex;
  		ex1->ee_len = cpu_to_le16(map->m_lblk - ee_block);
  		ext4_ext_mark_uninitialized(ex1);
  		ex2 = &newex;
  	}
  	/*
  	 * ex2: map->m_lblk to map->m_lblk + map->m_len-1 : to be written
  	 * using direct I/O, uninitialised still.
  	 */
  	ex2->ee_block = cpu_to_le32(map->m_lblk);
  	ext4_ext_store_pblock(ex2, newblock);
  	ex2->ee_len = cpu_to_le16(allocated);
  	ext4_ext_mark_uninitialized(ex2);
  	if (ex2 != ex)
  		goto insert;
  	/* Mark modified extent as dirty */
  	err = ext4_ext_dirty(handle, inode, path + depth);
  	ext_debug("out here\n");
  	goto out;
  insert:
  	err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
  	if (err == -ENOSPC && may_zeroout) {
  		err =  ext4_ext_zeroout(inode, &orig_ex);
  		if (err)
  			goto fix_extent_len;
  		/* update the extent length and mark as initialized */
  		ex->ee_block = orig_ex.ee_block;
  		ex->ee_len   = orig_ex.ee_len;
  		ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  		ext4_ext_dirty(handle, inode, path + depth);
  		/* zero out the first half */
  		return allocated;
  	} else if (err)
  		goto fix_extent_len;
  out:
  	ext4_ext_show_leaf(inode, path);
  	return err ? err : allocated;
  
  fix_extent_len:
  	ex->ee_block = orig_ex.ee_block;
  	ex->ee_len   = orig_ex.ee_len;
  	ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
  	ext4_ext_mark_uninitialized(ex);
  	ext4_ext_dirty(handle, inode, path + depth);
  	return err;
  }
  static int ext4_convert_unwritten_extents_endio(handle_t *handle,
  					      struct inode *inode,
  					      struct ext4_ext_path *path)
  {
  	struct ext4_extent *ex;
  	struct ext4_extent_header *eh;
  	int depth;
  	int err = 0;
  	int ret = 0;
  
  	depth = ext_depth(inode);
  	eh = path[depth].p_hdr;
  	ex = path[depth].p_ext;
  
  	err = ext4_ext_get_access(handle, inode, path + depth);
  	if (err)
  		goto out;
  	/* first mark the extent as initialized */
  	ext4_ext_mark_initialized(ex);
  
  	/*
  	 * We have to see if it can be merged with the extent
  	 * on the left.
  	 */
  	if (ex > EXT_FIRST_EXTENT(eh)) {
  		/*
  		 * To merge left, pass "ex - 1" to try_to_merge(),
  		 * since it merges towards right _only_.
  		 */
  		ret = ext4_ext_try_to_merge(inode, path, ex - 1);
  		if (ret) {
  			err = ext4_ext_correct_indexes(handle, inode, path);
  			if (err)
  				goto out;
  			depth = ext_depth(inode);
  			ex--;
  		}
  	}
  	/*
  	 * Try to Merge towards right.
  	 */
  	ret = ext4_ext_try_to_merge(inode, path, ex);
  	if (ret) {
  		err = ext4_ext_correct_indexes(handle, inode, path);
  		if (err)
  			goto out;
  		depth = ext_depth(inode);
  	}
  	/* Mark modified extent as dirty */
  	err = ext4_ext_dirty(handle, inode, path + depth);
  out:
  	ext4_ext_show_leaf(inode, path);
  	return err;
  }
  
  static void unmap_underlying_metadata_blocks(struct block_device *bdev,
  			sector_t block, int count)
  {
  	int i;
  	for (i = 0; i < count; i++)
                  unmap_underlying_metadata(bdev, block + i);
  }
  
  static int
  ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
  			struct ext4_map_blocks *map,
  			struct ext4_ext_path *path, int flags,
  			unsigned int allocated, ext4_fsblk_t newblock)
  {
  	int ret = 0;
  	int err = 0;
  	ext4_io_end_t *io = EXT4_I(inode)->cur_aio_dio;
  
  	ext_debug("ext4_ext_handle_uninitialized_extents: inode %lu, logical"
  		  "block %llu, max_blocks %u, flags %d, allocated %u",
  		  inode->i_ino, (unsigned long long)map->m_lblk, map->m_len,
  		  flags, allocated);
  	ext4_ext_show_leaf(inode, path);
  
  	/* get_block() before submit the IO, split the extent */
  	if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
  		ret = ext4_split_unwritten_extents(handle, inode, map,
  						   path, flags);
  		/*
  		 * Flag the inode(non aio case) or end_io struct (aio case)
  		 * that this IO needs to convertion to written when IO is
  		 * completed
  		 */
  		if (io)
  			io->flag = EXT4_IO_UNWRITTEN;
  		else
  			ext4_set_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN);
  		if (ext4_should_dioread_nolock(inode))
  			map->m_flags |= EXT4_MAP_UNINIT;
  		goto out;
  	}
  	/* IO end_io complete, convert the filled extent to written */
  	if ((flags & EXT4_GET_BLOCKS_CONVERT)) {
  		ret = ext4_convert_unwritten_extents_endio(handle, inode,
  							path);
  		if (ret >= 0)
  			ext4_update_inode_fsync_trans(handle, inode, 1);
  		goto out2;
  	}
  	/* buffered IO case */
  	/*
  	 * repeat fallocate creation request
  	 * we already have an unwritten extent
  	 */
  	if (flags & EXT4_GET_BLOCKS_UNINIT_EXT)
  		goto map_out;
  
  	/* buffered READ or buffered write_begin() lookup */
  	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
  		/*
  		 * We have blocks reserved already.  We
  		 * return allocated blocks so that delalloc
  		 * won't do block reservation for us.  But
  		 * the buffer head will be unmapped so that
  		 * a read from the block returns 0s.
  		 */
  		map->m_flags |= EXT4_MAP_UNWRITTEN;
  		goto out1;
  	}
  
  	/* buffered write, writepage time, convert*/
  	ret = ext4_ext_convert_to_initialized(handle, inode, map, path);
  	if (ret >= 0)
  		ext4_update_inode_fsync_trans(handle, inode, 1);
  out:
  	if (ret <= 0) {
  		err = ret;
  		goto out2;
  	} else
  		allocated = ret;
  	map->m_flags |= EXT4_MAP_NEW;
  	/*
  	 * if we allocated more blocks than requested
  	 * we need to make sure we unmap the extra block
  	 * allocated. The actual needed block will get
  	 * unmapped later when we find the buffer_head marked
  	 * new.
  	 */
  	if (allocated > map->m_len) {
  		unmap_underlying_metadata_blocks(inode->i_sb->s_bdev,
  					newblock + map->m_len,
  					allocated - map->m_len);
  		allocated = map->m_len;
  	}
  
  	/*
  	 * If we have done fallocate with the offset that is already
  	 * delayed allocated, we would have block reservation
  	 * and quota reservation done in the delayed write path.
  	 * But fallocate would have already updated quota and block
  	 * count for this offset. So cancel these reservation
  	 */
  	if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
  		ext4_da_update_reserve_space(inode, allocated, 0);
  
  map_out:
  	map->m_flags |= EXT4_MAP_MAPPED;
  out1:
  	if (allocated > map->m_len)
  		allocated = map->m_len;
  	ext4_ext_show_leaf(inode, path);
  	map->m_pblk = newblock;
  	map->m_len = allocated;
  out2:
  	if (path) {
  		ext4_ext_drop_refs(path);
  		kfree(path);
  	}
  	return err ? err : allocated;
  }
  /*
   * Block allocation/map/preallocation routine for extents based files
   *
   *
   * Need to be called with
   * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system block
   * (ie, create is zero). Otherwise down_write(&EXT4_I(inode)->i_data_sem)
   *
   * return > 0, number of of blocks already mapped/allocated
   *          if create == 0 and these are pre-allocated blocks
   *          	buffer head is unmapped
   *          otherwise blocks are mapped
   *
   * return = 0, if plain look up failed (blocks have not been allocated)
   *          buffer head is unmapped
   *
   * return < 0, error case.
   */
  int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
  			struct ext4_map_blocks *map, int flags)
  {
  	struct ext4_ext_path *path = NULL;
  	struct ext4_extent_header *eh;
  	struct ext4_extent newex, *ex, *last_ex;
  	ext4_fsblk_t newblock;
  	int i, err = 0, depth, ret, cache_type;
  	unsigned int allocated = 0;
  	struct ext4_allocation_request ar;
  	ext4_io_end_t *io = EXT4_I(inode)->cur_aio_dio;
  
  	ext_debug("blocks %u/%u requested for inode %lu\n",
  		  map->m_lblk, map->m_len, inode->i_ino);
  
  	/* check in cache */
  	cache_type = ext4_ext_in_cache(inode, map->m_lblk, &newex);
  	if (cache_type) {
  		if (cache_type == EXT4_EXT_CACHE_GAP) {
  			if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
  				/*
  				 * block isn't allocated yet and
  				 * user doesn't want to allocate it
  				 */
  				goto out2;
  			}
  			/* we should allocate requested block */
  		} else if (cache_type == EXT4_EXT_CACHE_EXTENT) {
  			/* block is already allocated */
  			newblock = map->m_lblk
  				   - le32_to_cpu(newex.ee_block)
  				   + ext_pblock(&newex);
  			/* number of remaining blocks in the extent */
  			allocated = ext4_ext_get_actual_len(&newex) -
  				(map->m_lblk - le32_to_cpu(newex.ee_block));
  			goto out;
  		} else {
  			BUG();
  		}
  	}
  
  	/* find extent for this block */
  	path = ext4_ext_find_extent(inode, map->m_lblk, NULL);
  	if (IS_ERR(path)) {
  		err = PTR_ERR(path);
  		path = NULL;
  		goto out2;
  	}
  
  	depth = ext_depth(inode);
  
  	/*
  	 * consistent leaf must not be empty;
  	 * this situation is possible, though, _during_ tree modification;
  	 * this is why assert can't be put in ext4_ext_find_extent()
  	 */
  	if (unlikely(path[depth].p_ext == NULL && depth != 0)) {
  		EXT4_ERROR_INODE(inode, "bad extent address "
  				 "lblock: %lu, depth: %d pblock %lld",
  				 (unsigned long) map->m_lblk, depth,
  				 path[depth].p_block);
  		err = -EIO;
  		goto out2;
  	}
  	eh = path[depth].p_hdr;
  
  	ex = path[depth].p_ext;
  	if (ex) {
  		ext4_lblk_t ee_block = le32_to_cpu(ex->ee_block);
  		ext4_fsblk_t ee_start = ext_pblock(ex);
  		unsigned short ee_len;
  
  		/*
  		 * Uninitialized extents are treated as holes, except that
  		 * we split out initialized portions during a write.
  		 */
  		ee_len = ext4_ext_get_actual_len(ex);
  		/* if found extent covers block, simply return it */
  		if (in_range(map->m_lblk, ee_block, ee_len)) {
  			newblock = map->m_lblk - ee_block + ee_start;
  			/* number of remaining blocks in the extent */
  			allocated = ee_len - (map->m_lblk - ee_block);
  			ext_debug("%u fit into %u:%d -> %llu\n", map->m_lblk,
  				  ee_block, ee_len, newblock);
  
  			/* Do not put uninitialized extent in the cache */
  			if (!ext4_ext_is_uninitialized(ex)) {
  				ext4_ext_put_in_cache(inode, ee_block,
  							ee_len, ee_start,
  							EXT4_EXT_CACHE_EXTENT);
  				goto out;
  			}
  			ret = ext4_ext_handle_uninitialized_extents(handle,
  					inode, map, path, flags, allocated,
  					newblock);
  			return ret;
  		}
  	}
  
  	/*
  	 * requested block isn't allocated yet;
  	 * we couldn't try to create block if create flag is zero
  	 */
  	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
  		/*
  		 * put just found gap into cache to speed up
  		 * subsequent requests
  		 */
  		ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
  		goto out2;
  	}
  	/*
  	 * Okay, we need to do block allocation.
  	 */
  
  	/* find neighbour allocated blocks */
  	ar.lleft = map->m_lblk;
  	err = ext4_ext_search_left(inode, path, &ar.lleft, &ar.pleft);
  	if (err)
  		goto out2;
  	ar.lright = map->m_lblk;
  	err = ext4_ext_search_right(inode, path, &ar.lright, &ar.pright);
  	if (err)
  		goto out2;
  
  	/*
  	 * See if request is beyond maximum number of blocks we can have in
  	 * a single extent. For an initialized extent this limit is
  	 * EXT_INIT_MAX_LEN and for an uninitialized extent this limit is
  	 * EXT_UNINIT_MAX_LEN.
  	 */
  	if (map->m_len > EXT_INIT_MAX_LEN &&
  	    !(flags & EXT4_GET_BLOCKS_UNINIT_EXT))
  		map->m_len = EXT_INIT_MAX_LEN;
  	else if (map->m_len > EXT_UNINIT_MAX_LEN &&
  		 (flags & EXT4_GET_BLOCKS_UNINIT_EXT))
  		map->m_len = EXT_UNINIT_MAX_LEN;
  
  	/* Check if we can really insert (m_lblk)::(m_lblk + m_len) extent */
  	newex.ee_block = cpu_to_le32(map->m_lblk);
  	newex.ee_len = cpu_to_le16(map->m_len);
  	err = ext4_ext_check_overlap(inode, &newex, path);
  	if (err)
  		allocated = ext4_ext_get_actual_len(&newex);
  	else
  		allocated = map->m_len;
  
  	/* allocate new block */
  	ar.inode = inode;
  	ar.goal = ext4_ext_find_goal(inode, path, map->m_lblk);
  	ar.logical = map->m_lblk;
  	ar.len = allocated;
  	if (S_ISREG(inode->i_mode))
  		ar.flags = EXT4_MB_HINT_DATA;
  	else
  		/* disable in-core preallocation for non-regular files */
  		ar.flags = 0;
  	newblock = ext4_mb_new_blocks(handle, &ar, &err);
  	if (!newblock)
  		goto out2;
  	ext_debug("allocate new block: goal %llu, found %llu/%u\n",
  		  ar.goal, newblock, allocated);
  
  	/* try to insert new extent into found leaf and return */
  	ext4_ext_store_pblock(&newex, newblock);
  	newex.ee_len = cpu_to_le16(ar.len);
  	/* Mark uninitialized */
  	if (flags & EXT4_GET_BLOCKS_UNINIT_EXT){
  		ext4_ext_mark_uninitialized(&newex);
  		/*
  		 * io_end structure was created for every IO write to an
  		 * uninitialized extent. To avoid unecessary conversion,
  		 * here we flag the IO that really needs the conversion.
  		 * For non asycn direct IO case, flag the inode state
  		 * that we need to perform convertion when IO is done.
  		 */
  		if ((flags & EXT4_GET_BLOCKS_PRE_IO)) {
  			if (io)
  				io->flag = EXT4_IO_UNWRITTEN;
  			else
  				ext4_set_inode_state(inode,
  						     EXT4_STATE_DIO_UNWRITTEN);
  		}
  		if (ext4_should_dioread_nolock(inode))
  			map->m_flags |= EXT4_MAP_UNINIT;
  	}
  
  	if (unlikely(ext4_test_inode_flag(inode, EXT4_INODE_EOFBLOCKS))) {
  		if (unlikely(!eh->eh_entries)) {
  			EXT4_ERROR_INODE(inode,
  					 "eh->eh_entries == 0 and "
  					 "EOFBLOCKS_FL set");
  			err = -EIO;
  			goto out2;
  		}
  		last_ex = EXT_LAST_EXTENT(eh);
  		/*
  		 * If the current leaf block was reached by looking at
  		 * the last index block all the way down the tree, and
  		 * we are extending the inode beyond the last extent
  		 * in the current leaf block, then clear the
  		 * EOFBLOCKS_FL flag.
  		 */
  		for (i = depth-1; i >= 0; i--) {
  			if (path[i].p_idx != EXT_LAST_INDEX(path[i].p_hdr))
  				break;
  		}
  		if ((i < 0) &&
  		    (map->m_lblk + ar.len > le32_to_cpu(last_ex->ee_block) +
  		     ext4_ext_get_actual_len(last_ex)))
  			ext4_clear_inode_flag(inode, EXT4_INODE_EOFBLOCKS);
  	}
  	err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
  	if (err) {
  		/* free data blocks we just allocated */
  		/* not a good idea to call discard here directly,
  		 * but otherwise we'd need to call it every free() */
  		ext4_discard_preallocations(inode);
  		ext4_free_blocks(handle, inode, 0, ext_pblock(&newex),
  				 ext4_ext_get_actual_len(&newex), 0);
  		goto out2;
  	}
  
  	/* previous routine could use block we allocated */
  	newblock = ext_pblock(&newex);
  	allocated = ext4_ext_get_actual_len(&newex);
  	if (allocated > map->m_len)
  		allocated = map->m_len;
  	map->m_flags |= EXT4_MAP_NEW;
  
  	/*
  	 * Update reserved blocks/metadata blocks after successful
  	 * block allocation which had been deferred till now.
  	 */
  	if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
  		ext4_da_update_reserve_space(inode, allocated, 1);
  
  	/*
  	 * Cache the extent and update transaction to commit on fdatasync only
  	 * when it is _not_ an uninitialized extent.
  	 */
  	if ((flags & EXT4_GET_BLOCKS_UNINIT_EXT) == 0) {
  		ext4_ext_put_in_cache(inode, map->m_lblk, allocated, newblock,
  						EXT4_EXT_CACHE_EXTENT);
  		ext4_update_inode_fsync_trans(handle, inode, 1);
  	} else
  		ext4_update_inode_fsync_trans(handle, inode, 0);
  out:
  	if (allocated > map->m_len)
  		allocated = map->m_len;
  	ext4_ext_show_leaf(inode, path);
  	map->m_flags |= EXT4_MAP_MAPPED;
  	map->m_pblk = newblock;
  	map->m_len = allocated;
  out2:
  	if (path) {
  		ext4_ext_drop_refs(path);
  		kfree(path);
  	}
  	return err ? err : allocated;
  }
  
  void ext4_ext_truncate(struct inode *inode)
  {
  	struct address_space *mapping = inode->i_mapping;
  	struct super_block *sb = inode->i_sb;
  	ext4_lblk_t last_block;
  	handle_t *handle;
  	int err = 0;
  
  	/*
  	 * probably first extent we're gonna free will be last in block
  	 */
  	err = ext4_writepage_trans_blocks(inode);
  	handle = ext4_journal_start(inode, err);
  	if (IS_ERR(handle))
  		return;
  
  	if (inode->i_size & (sb->s_blocksize - 1))
  		ext4_block_truncate_page(handle, mapping, inode->i_size);
  
  	if (ext4_orphan_add(handle, inode))
  		goto out_stop;
  
  	down_write(&EXT4_I(inode)->i_data_sem);
  	ext4_ext_invalidate_cache(inode);
  
  	ext4_discard_preallocations(inode);
  
  	/*
  	 * TODO: optimization is possible here.
  	 * Probably we need not scan at all,
  	 * because page truncation is enough.
  	 */
  
  	/* we have to know where to truncate from in crash case */
  	EXT4_I(inode)->i_disksize = inode->i_size;
  	ext4_mark_inode_dirty(handle, inode);
  
  	last_block = (inode->i_size + sb->s_blocksize - 1)
  			>> EXT4_BLOCK_SIZE_BITS(sb);
  	err = ext4_ext_remove_space(inode, last_block);
  
  	/* In a multi-transaction truncate, we only make the final
  	 * transaction synchronous.
  	 */
  	if (IS_SYNC(inode))
  		ext4_handle_sync(handle);
  
  out_stop:
  	up_write(&EXT4_I(inode)->i_data_sem);
  	/*
  	 * If this was a simple ftruncate() and the file will remain alive,
  	 * then we need to clear up the orphan record which we created above.
  	 * However, if this was a real unlink then we were called by
  	 * ext4_delete_inode(), and we allow that function to clean up the
  	 * orphan info for us.
  	 */
  	if (inode->i_nlink)
  		ext4_orphan_del(handle, inode);
  
  	inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
  	ext4_mark_inode_dirty(handle, inode);
  	ext4_journal_stop(handle);
  }
  
  static void ext4_falloc_update_inode(struct inode *inode,
  				int mode, loff_t new_size, int update_ctime)
  {
  	struct timespec now;
  
  	if (update_ctime) {
  		now = current_fs_time(inode->i_sb);
  		if (!timespec_equal(&inode->i_ctime, &now))
  			inode->i_ctime = now;
  	}
  	/*
  	 * Update only when preallocation was requested beyond
  	 * the file size.
  	 */
  	if (!(mode & FALLOC_FL_KEEP_SIZE)) {
  		if (new_size > i_size_read(inode))
  			i_size_write(inode, new_size);
  		if (new_size > EXT4_I(inode)->i_disksize)
  			ext4_update_i_disksize(inode, new_size);
  	} else {
  		/*
  		 * Mark that we allocate beyond EOF so the subsequent truncate
  		 * can proceed even if the new size is the same as i_size.
  		 */
  		if (new_size > i_size_read(inode))
  			ext4_set_inode_flag(inode, EXT4_INODE_EOFBLOCKS);
  	}
  
  }
  
  /*
   * preallocate space for a file. This implements ext4's fallocate inode
   * operation, which gets called from sys_fallocate system call.
   * For block-mapped files, posix_fallocate should fall back to the method
   * of writing zeroes to the required new blocks (the same behavior which is
   * expected for file systems which do not support fallocate() system call).
   */
  long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
  {
  	handle_t *handle;
  	loff_t new_size;
  	unsigned int max_blocks;
  	int ret = 0;
  	int ret2 = 0;
  	int retries = 0;
  	struct ext4_map_blocks map;
  	unsigned int credits, blkbits = inode->i_blkbits;
  
  	/*
  	 * currently supporting (pre)allocate mode for extent-based
  	 * files _only_
  	 */
  	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
  		return -EOPNOTSUPP;
  
  	/* preallocation to directories is currently not supported */
  	if (S_ISDIR(inode->i_mode))
  		return -ENODEV;
  
  	map.m_lblk = offset >> blkbits;
  	/*
  	 * We can't just convert len to max_blocks because
  	 * If blocksize = 4096 offset = 3072 and len = 2048
  	 */
  	max_blocks = (EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits)
  		- map.m_lblk;
  	/*
  	 * credits to insert 1 extent into extent tree
  	 */
  	credits = ext4_chunk_trans_blocks(inode, max_blocks);
  	mutex_lock(&inode->i_mutex);
  	ret = inode_newsize_ok(inode, (len + offset));
  	if (ret) {
  		mutex_unlock(&inode->i_mutex);
  		return ret;
  	}
  retry:
  	while (ret >= 0 && ret < max_blocks) {
  		map.m_lblk = map.m_lblk + ret;
  		map.m_len = max_blocks = max_blocks - ret;
  		handle = ext4_journal_start(inode, credits);
  		if (IS_ERR(handle)) {
  			ret = PTR_ERR(handle);
  			break;
  		}
  		ret = ext4_map_blocks(handle, inode, &map,
  				      EXT4_GET_BLOCKS_CREATE_UNINIT_EXT);
  		if (ret <= 0) {
  #ifdef EXT4FS_DEBUG
  			WARN_ON(ret <= 0);
  			printk(KERN_ERR "%s: ext4_ext_map_blocks "
  				    "returned error inode#%lu, block=%u, "
  				    "max_blocks=%u", __func__,
  				    inode->i_ino, block, max_blocks);
  #endif
  			ext4_mark_inode_dirty(handle, inode);
  			ret2 = ext4_journal_stop(handle);
  			break;
  		}
  		if ((map.m_lblk + ret) >= (EXT4_BLOCK_ALIGN(offset + len,
  						blkbits) >> blkbits))
  			new_size = offset + len;
  		else
  			new_size = (map.m_lblk + ret) << blkbits;
  
  		ext4_falloc_update_inode(inode, mode, new_size,
  					 (map.m_flags & EXT4_MAP_NEW));
  		ext4_mark_inode_dirty(handle, inode);
  		ret2 = ext4_journal_stop(handle);
  		if (ret2)
  			break;
  	}
  	if (ret == -ENOSPC &&
  			ext4_should_retry_alloc(inode->i_sb, &retries)) {
  		ret = 0;
  		goto retry;
  	}
  	mutex_unlock(&inode->i_mutex);
  	return ret > 0 ? ret2 : ret;
  }
  
  /*
   * This function convert a range of blocks to written extents
   * The caller of this function will pass the start offset and the size.
   * all unwritten extents within this range will be converted to
   * written extents.
   *
   * This function is called from the direct IO end io call back
   * function, to convert the fallocated extents after IO is completed.
   * Returns 0 on success.
   */
  int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
  				    ssize_t len)
  {
  	handle_t *handle;
  	unsigned int max_blocks;
  	int ret = 0;
  	int ret2 = 0;
  	struct ext4_map_blocks map;
  	unsigned int credits, blkbits = inode->i_blkbits;
  
  	map.m_lblk = offset >> blkbits;
  	/*
  	 * We can't just convert len to max_blocks because
  	 * If blocksize = 4096 offset = 3072 and len = 2048
  	 */
  	max_blocks = ((EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits) -
  		      map.m_lblk);
  	/*
  	 * credits to insert 1 extent into extent tree
  	 */
  	credits = ext4_chunk_trans_blocks(inode, max_blocks);
  	while (ret >= 0 && ret < max_blocks) {
  		map.m_lblk += ret;
  		map.m_len = (max_blocks -= ret);
  		handle = ext4_journal_start(inode, credits);
  		if (IS_ERR(handle)) {
  			ret = PTR_ERR(handle);
  			break;
  		}
  		ret = ext4_map_blocks(handle, inode, &map,
  				      EXT4_GET_BLOCKS_IO_CONVERT_EXT);
  		if (ret <= 0) {
  			WARN_ON(ret <= 0);
  			printk(KERN_ERR "%s: ext4_ext_map_blocks "
  				    "returned error inode#%lu, block=%u, "
  				    "max_blocks=%u", __func__,
  				    inode->i_ino, map.m_lblk, map.m_len);
  		}
  		ext4_mark_inode_dirty(handle, inode);
  		ret2 = ext4_journal_stop(handle);
  		if (ret <= 0 || ret2 )
  			break;
  	}
  	return ret > 0 ? ret2 : ret;
  }
  /*
   * Callback function called for each extent to gather FIEMAP information.
   */
  static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path,
  		       struct ext4_ext_cache *newex, struct ext4_extent *ex,
  		       void *data)
  {
  	struct fiemap_extent_info *fieinfo = data;
  	unsigned char blksize_bits = inode->i_sb->s_blocksize_bits;
  	__u64	logical;
  	__u64	physical;
  	__u64	length;
  	__u32	flags = 0;
  	int	error;
  
  	logical =  (__u64)newex->ec_block << blksize_bits;
  
  	if (newex->ec_type == EXT4_EXT_CACHE_GAP) {
  		pgoff_t offset;
  		struct page *page;
  		struct buffer_head *bh = NULL;
  
  		offset = logical >> PAGE_SHIFT;
  		page = find_get_page(inode->i_mapping, offset);
  		if (!page || !page_has_buffers(page))
  			return EXT_CONTINUE;
  
  		bh = page_buffers(page);
  
  		if (!bh)
  			return EXT_CONTINUE;
  
  		if (buffer_delay(bh)) {
  			flags |= FIEMAP_EXTENT_DELALLOC;
  			page_cache_release(page);
  		} else {
  			page_cache_release(page);
  			return EXT_CONTINUE;
  		}
  	}
  
  	physical = (__u64)newex->ec_start << blksize_bits;
  	length =   (__u64)newex->ec_len << blksize_bits;
  
  	if (ex && ext4_ext_is_uninitialized(ex))
  		flags |= FIEMAP_EXTENT_UNWRITTEN;
  
  	/*
  	 * If this extent reaches EXT_MAX_BLOCK, it must be last.
  	 *
  	 * Or if ext4_ext_next_allocated_block is EXT_MAX_BLOCK,
  	 * this also indicates no more allocated blocks.
  	 *
  	 * XXX this might miss a single-block extent at EXT_MAX_BLOCK
  	 */
  	if (ext4_ext_next_allocated_block(path) == EXT_MAX_BLOCK ||
  	    newex->ec_block + newex->ec_len - 1 == EXT_MAX_BLOCK) {
  		loff_t size = i_size_read(inode);
  		loff_t bs = EXT4_BLOCK_SIZE(inode->i_sb);
  
  		flags |= FIEMAP_EXTENT_LAST;
  		if ((flags & FIEMAP_EXTENT_DELALLOC) &&
  		    logical+length > size)
  			length = (size - logical + bs - 1) & ~(bs-1);
  	}
  
  	error = fiemap_fill_next_extent(fieinfo, logical, physical,
  					length, flags);
  	if (error < 0)
  		return error;
  	if (error == 1)
  		return EXT_BREAK;
  
  	return EXT_CONTINUE;
  }
  
  /* fiemap flags we can handle specified here */
  #define EXT4_FIEMAP_FLAGS	(FIEMAP_FLAG_SYNC|FIEMAP_FLAG_XATTR)
  
  static int ext4_xattr_fiemap(struct inode *inode,
  				struct fiemap_extent_info *fieinfo)
  {
  	__u64 physical = 0;
  	__u64 length;
  	__u32 flags = FIEMAP_EXTENT_LAST;
  	int blockbits = inode->i_sb->s_blocksize_bits;
  	int error = 0;
  
  	/* in-inode? */
  	if (ext4_test_inode_state(inode, EXT4_STATE_XATTR)) {
  		struct ext4_iloc iloc;
  		int offset;	/* offset of xattr in inode */
  
  		error = ext4_get_inode_loc(inode, &iloc);
  		if (error)
  			return error;
  		physical = iloc.bh->b_blocknr << blockbits;
  		offset = EXT4_GOOD_OLD_INODE_SIZE +
  				EXT4_I(inode)->i_extra_isize;
  		physical += offset;
  		length = EXT4_SB(inode->i_sb)->s_inode_size - offset;
  		flags |= FIEMAP_EXTENT_DATA_INLINE;
  		brelse(iloc.bh);
  	} else { /* external block */
  		physical = EXT4_I(inode)->i_file_acl << blockbits;
  		length = inode->i_sb->s_blocksize;
  	}
  
  	if (physical)
  		error = fiemap_fill_next_extent(fieinfo, 0, physical,
  						length, flags);
  	return (error < 0 ? error : 0);
  }
  
  int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
  		__u64 start, __u64 len)
  {
  	ext4_lblk_t start_blk;
  	int error = 0;
  
  	/* fallback to generic here if not in extents fmt */
  	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
  		return generic_block_fiemap(inode, fieinfo, start, len,
  			ext4_get_block);
  
  	if (fiemap_check_flags(fieinfo, EXT4_FIEMAP_FLAGS))
  		return -EBADR;
  
  	if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR) {
  		error = ext4_xattr_fiemap(inode, fieinfo);
  	} else {
  		ext4_lblk_t len_blks;
  		__u64 last_blk;
  
  		start_blk = start >> inode->i_sb->s_blocksize_bits;
  		last_blk = (start + len - 1) >> inode->i_sb->s_blocksize_bits;
  		if (last_blk >= EXT_MAX_BLOCK)
  			last_blk = EXT_MAX_BLOCK-1;
  		len_blks = ((ext4_lblk_t) last_blk) - start_blk + 1;
  
  		/*
  		 * Walk the extent tree gathering extent information.
  		 * ext4_ext_fiemap_cb will push extents back to user.
  		 */
  		error = ext4_ext_walk_space(inode, start_blk, len_blks,
  					  ext4_ext_fiemap_cb, fieinfo);
  	}
  
  	return error;
  }
  
  