fs/ext4/extents.c

/*
 * 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/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 <trace/events/ext4.h>

static int ext4_split_extent(handle_t *handle,
				struct inode *inode,
				struct ext4_ext_path *path,
				struct ext4_map_blocks *map,
				int split_flag,
				int flags);

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
 */
#define ext4_ext_dirty(handle, inode, path) \
		__ext4_ext_dirty(__func__, __LINE__, (handle), (inode), (path))
static int __ext4_ext_dirty(const char *where, unsigned int line,
			    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(where, line, handle,
						   inode, path->p_bh);
	} else {
		/* path points to leaf/index in inode body */
		err = ext4_mark_inode_dirty(handle, inode);
	}
	return err;
}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

/*
 * Calculate the number of metadata blocks needed
 * to allocate @blocks
 * Worse case is one block per extent
 */
int ext4_ext_calc_metadata_amount(struct inode *inode, ext4_lblk_t lblock)
{
	struct ext4_inode_info *ei = EXT4_I(inode);
	int idxs;

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

	/*
	 * If the new delayed allocation block is contiguous with the
	 * previous da block, it can share index blocks with the
	 * previous block, so we only need to allocate a new index
	 * block every idxs leaf blocks.  At ldxs**2 blocks, we need
	 * an additional index block, and at ldxs**3 blocks, yet
	 * another index blocks.
	 */
	if (ei->i_da_metadata_calc_len &&
	    ei->i_da_metadata_calc_last_lblock+1 == lblock) {
		int num = 0;

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

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

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

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

	return max;
}

static int ext4_valid_extent(struct inode *inode, struct ext4_extent *ext)
{
	ext4_fsblk_t block = ext4_ext_pblock(ext);
	int len = ext4_ext_get_actual_len(ext);

	if (len == 0)
		return 0;
	return ext4_data_block_valid(EXT4_SB(inode->i_sb), block, len);
}

static int ext4_valid_extent_idx(struct inode *inode,
				struct ext4_extent_idx *ext_idx)
{
	ext4_fsblk_t block = ext4_idx_pblock(ext_idx);

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

static int ext4_valid_extent_entries(struct inode *inode,
				struct ext4_extent_header *eh,
				int depth)
{
	unsigned short entries;
	if (eh->eh_entries == 0)
		return 1;

	entries = le16_to_cpu(eh->eh_entries);

	if (depth == 0) {
		/* leaf entries */
		struct ext4_extent *ext = EXT_FIRST_EXTENT(eh);
		while (entries) {
			if (!ext4_valid_extent(inode, ext))
				return 0;
			ext++;
			entries--;
		}
	} else {
		struct ext4_extent_idx *ext_idx = EXT_FIRST_INDEX(eh);
		while (entries) {
			if (!ext4_valid_extent_idx(inode, ext_idx))
				return 0;
			ext_idx++;
			entries--;
		}
	}
	return 1;
}

static int __ext4_ext_check(const char *function, unsigned int line,
			    struct inode *inode, struct ext4_extent_header *eh,
			    int depth)
{
	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),
			    ext4_idx_pblock(path->p_idx));
		} else if (path->p_ext) {
			ext_debug("  %d:[%d]%d:%llu ",
				  le32_to_cpu(path->p_ext->ee_block),
				  ext4_ext_is_uninitialized(path->p_ext),
				  ext4_ext_get_actual_len(path->p_ext),
				  ext4_ext_pblock(path->p_ext));
		} else
			ext_debug("  []");
	}
	ext_debug("\n");
}

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

	if (!path)
		return;

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

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

	for (i = 0; i < le16_to_cpu(eh->eh_entries); i++, ex++) {
		ext_debug("%d:[%d]%d:%llu ", le32_to_cpu(ex->ee_block),
			  ext4_ext_is_uninitialized(ex),
			  ext4_ext_get_actual_len(ex), ext4_ext_pblock(ex));
	}
	ext_debug("\n");
}

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

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

		return;
	}

	ex = path[depth].p_ext;
	while (ex <= EXT_MAX_EXTENT(path[depth].p_hdr)) {
		ext_debug("move %d:%llu:[%d]%d in new leaf %llu\n",
				le32_to_cpu(ex->ee_block),
				ext4_ext_pblock(ex),
				ext4_ext_is_uninitialized(ex),
				ext4_ext_get_actual_len(ex),
				newblock);
		ex++;
	}
}

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

void ext4_ext_drop_refs(struct ext4_ext_path *path)
{
	int depth = 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),
		  ext4_idx_pblock(path->p_idx));

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

		chix = ix = EXT_FIRST_INDEX(eh);
		for (k = 0; k < le16_to_cpu(eh->eh_entries); k++, ix++) {
		  if (k != 0 &&
		      le32_to_cpu(ix->ei_block) <= le32_to_cpu(ix[-1].ei_block)) {
				printk(KERN_DEBUG "k=%d, ix=0x%p, "
				       "first=0x%p\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),
			ext4_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 = ext4_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)) {
			trace_ext4_ext_load_extent(inode, block,
						path[ppos].p_block);
			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 = ext4_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
 */
static int ext4_ext_insert_index(handle_t *handle, struct inode *inode,
				 struct ext4_ext_path *curp,
				 int logical, ext4_fsblk_t ptr)
{
	struct ext4_extent_idx *ix;
	int len, err;

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

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

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

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

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

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

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

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

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

	return err;
}

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

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

	/* if current leaf will be split, then we should use
	 * border from split point */
	if (unlikely(path[depth].p_ext > EXT_MAX_EXTENT(path[depth].p_hdr))) {
		EXT4_ERROR_INODE(inode, "p_ext > EXT_MAX_EXTENT!");
		return -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, flags);
		if (newblock == 0)
			goto cleanup;
		ablocks[a] = newblock;
	}

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

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

	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);

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

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

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

		i--;
	}

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

cleanup:
	if (bh) {
		if (buffer_locked(bh))
			unlock_buffer(bh);
		brelse(bh);
	}

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

	return err;
}

/*
 * ext4_ext_grow_indepth:
 * implements tree growing procedure:
 * - allocates new block
 * - moves top-level data (index block or leaf) into the new block
 * - initializes new top-level, creating index that points to the
 *   just created block
 */
static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
				 unsigned int flags,
				 struct ext4_extent *newext)
{
	struct ext4_extent_header *neh;
	struct buffer_head *bh;
	ext4_fsblk_t newblock;
	int err = 0;

	newblock = ext4_ext_new_meta_block(handle, inode, NULL,
		newext, &err, flags);
	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, EXT4_I(inode)->i_data,
		sizeof(EXT4_I(inode)->i_data));

	/* set size of new block */
	neh = ext_block_hdr(bh);
	/* old root could have indexes or leaves
	 * so calculate e_max right way */
	if (ext_depth(inode))
		neh->eh_max = cpu_to_le16(ext4_ext_space_block_idx(inode, 0));
	else
		neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));
	neh->eh_magic = EXT4_EXT_MAGIC;
	set_buffer_uptodate(bh);
	unlock_buffer(bh);

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

	/* Update top-level index: num,max,pointer */
	neh = ext_inode_hdr(inode);
	neh->eh_entries = cpu_to_le16(1);
	ext4_idx_store_pblock(EXT_FIRST_INDEX(neh), newblock);
	if (neh->eh_depth == 0) {
		/* Root extent block becomes index block */
		neh->eh_max = cpu_to_le16(ext4_ext_space_root_idx(inode, 0));
		EXT_FIRST_INDEX(neh)->ei_block =
			EXT_FIRST_EXTENT(neh)->ee_block;
	}
	ext_debug("new root: num %d(%d), lblock %d, ptr %llu\n",
		  le16_to_cpu(neh->eh_entries), le16_to_cpu(neh->eh_max),
		  le32_to_cpu(EXT_FIRST_INDEX(neh)->ei_block),
		  ext4_idx_pblock(EXT_FIRST_INDEX(neh)));

	neh->eh_depth = cpu_to_le16(le16_to_cpu(neh->eh_depth) + 1);
	ext4_mark_inode_dirty(handle, inode);
out:
	brelse(bh);

	return err;
}

/*
 * ext4_ext_create_new_leaf:
 * finds empty index and adds new leaf.
 * if no free index is found, then it requests in-depth growing.
 */
static int ext4_ext_create_new_leaf(handle_t *handle, struct inode *inode,
				    unsigned int flags,
				    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, flags, 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, flags, 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
 */
static int ext4_ext_search_left(struct inode *inode,
				struct ext4_ext_path *path,
				ext4_lblk_t *logical, ext4_fsblk_t *phys)
{
	struct ext4_extent_idx *ix;
	struct ext4_extent *ex;
	int depth, ee_len;

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

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

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

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

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

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

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

	if (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;
			}
		}
		goto found_extent;
	}

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

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

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

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

got_index:
	/* we've found index to the right, let's
	 * follow it and find the closest allocated
	 * block to the right */
	ix++;
	block = ext4_idx_pblock(ix);
	while (++depth < path->p_depth) {
		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 = ext4_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);
found_extent:
	*logical = le32_to_cpu(ex->ee_block);
	*phys = ext4_ext_pblock(ex);
	*ret_ex = ex;
	if (bh)
		put_bh(bh);
	return 0;
}

/*
 * ext4_ext_next_allocated_block:
 * returns allocated block in subsequent extent or EXT_MAX_BLOCKS.
 * NOTE: it considers block number from index entry as
 * allocated block. Thus, index entries have to be consistent
 * with leaves.
 */
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_BLOCKS;

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

	return EXT_MAX_BLOCKS;
}

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

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

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

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

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

	return EXT_MAX_BLOCKS;
}

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

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

	if (unlikely(ex == NULL || eh == NULL)) {
		EXT4_ERROR_INODE(inode,
				 "ex %p == NULL or eh %p == NULL", ex, eh);
		return -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 (ext4_ext_pblock(ex1) + ext1_ee_len == ext4_ext_pblock(ex2))
		return 1;
	return 0;
}

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

/*
 * This function tries to merge the @ex extent to neighbours in the tree.
 * return 1 if merge left else 0.
 */
static 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;
	int merge_done = 0;
	int ret = 0;

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

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

	if (!merge_done)
		ret = ext4_ext_try_to_merge_right(inode, path, ex);

	return ret;
}

/*
 * 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.
 */
static unsigned int ext4_ext_check_overlap(struct ext4_sb_info *sbi,
					   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);
	b2 &= ~(sbi->s_cluster_ratio - 1);

	/*
	 * 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_BLOCKS)
			goto out;
		b2 &= ~(sbi->s_cluster_ratio - 1);
	}

	/* check for wrap through zero on extent logical start block*/
	if (b1 + len1 < b1) {
		len1 = EXT_MAX_BLOCKS - 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;
	int flags = 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 %u:[%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),
			  ext4_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;
	}

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

	/* probably next leaf has space for us? */
	fex = EXT_LAST_EXTENT(eh);
	next = EXT_MAX_BLOCKS;
	if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block))
		next = ext4_ext_next_leaf_block(path);
	if (next != EXT_MAX_BLOCKS) {
		ext_debug("next leaf block - %u\n", next);
		BUG_ON(npath != NULL);
		npath = ext4_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 isn't full(%d)\n",
				  le16_to_cpu(eh->eh_entries));
			path = npath;
			goto has_space;
		}
		ext_debug("next leaf has no free space(%d,%d)\n",
			  le16_to_cpu(eh->eh_entries), le16_to_cpu(eh->eh_max));
	}

	/*
	 * There is no free space in the found leaf.
	 * We're gonna add a new leaf in the tree.
	 */
	if (flag & EXT4_GET_BLOCKS_PUNCH_OUT_EXT)
		flags = EXT4_MB_USE_ROOT_BLOCKS;
	err = ext4_ext_create_new_leaf(handle, inode, flags, 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: %u:%llu:[%d]%d\n",
				le32_to_cpu(newext->ee_block),
				ext4_ext_pblock(newext),
				ext4_ext_is_uninitialized(newext),
				ext4_ext_get_actual_len(newext));
		nearex = EXT_FIRST_EXTENT(eh);
	} else {
		if (le32_to_cpu(newext->ee_block)
			   > le32_to_cpu(nearex->ee_block)) {
			/* Insert after */
			ext_debug("insert %u:%llu:[%d]%d before: "
					"nearest %p\n",
					le32_to_cpu(newext->ee_block),
					ext4_ext_pblock(newext),
					ext4_ext_is_uninitialized(newext),
					ext4_ext_get_actual_len(newext),
					nearex);
			nearex++;
		} else {
			/* Insert before */
			BUG_ON(newext->ee_block == nearex->ee_block);
			ext_debug("insert %u:%llu:[%d]%d after: "
					"nearest %p\n",
					le32_to_cpu(newext->ee_block),
					ext4_ext_pblock(newext),
					ext4_ext_is_uninitialized(newext),
					ext4_ext_get_actual_len(newext),
					nearex);
		}
		len = EXT_LAST_EXTENT(eh) - nearex + 1;
		if (len > 0) {
			ext_debug("insert %u:%llu:[%d]%d: "
					"move %d extents from 0x%p to 0x%p\n",
					le32_to_cpu(newext->ee_block),
					ext4_ext_pblock(newext),
					ext4_ext_is_uninitialized(newext),
					ext4_ext_get_actual_len(newext),
					len, nearex, nearex + 1);
			memmove(nearex + 1, nearex,
				len * sizeof(struct ext4_extent));
		}
	}

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

merge:
	/* try to merge extents 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;
}

static 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_BLOCKS) {
		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;
		} else {
			cbex.ec_block = le32_to_cpu(ex->ee_block);
			cbex.ec_len = ext4_ext_get_actual_len(ex);
			cbex.ec_start = ext4_ext_pblock(ex);
		}

		if (unlikely(cbex.ec_len == 0)) {
			EXT4_ERROR_INODE(inode, "cbex.ec_len == 0");
			err = -EIO;
			break;
		}
		err = func(inode, next, &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)
{
	struct ext4_ext_cache *cex;
	BUG_ON(len == 0);
	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
	trace_ext4_ext_put_in_cache(inode, block, len, start);
	cex = &EXT4_I(inode)->i_cached_extent;
	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_BLOCKS;
		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_check_cache()
 * Checks to see if the given block is in the cache.
 * If it is, the cached extent is stored in the given
 * cache extent pointer.  If the cached extent is a hole,
 * this routine should be used instead of
 * ext4_ext_in_cache if the calling function needs to
 * know the size of the hole.
 *
 * @inode: The files inode
 * @block: The block to look for in the cache
 * @ex:    Pointer where the cached extent will be stored
 *         if it contains block
 *
 * Return 0 if cache is invalid; 1 if the cache is valid
 */
static int ext4_ext_check_cache(struct inode *inode, ext4_lblk_t block,
	struct ext4_ext_cache *ex){
	struct ext4_ext_cache *cex;
	struct ext4_sb_info *sbi;
	int ret = 0;

	/*
	 * 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;
	sbi = EXT4_SB(inode->i_sb);

	/* has cache valid data? */
	if (cex->ec_len == 0)
		goto errout;

	if (in_range(block, cex->ec_block, cex->ec_len)) {
		memcpy(ex, cex, sizeof(struct ext4_ext_cache));
		ext_debug("%u cached by %u:%u:%llu\n",
				block,
				cex->ec_block, cex->ec_len, cex->ec_start);
		ret = 1;
	}
errout:
	trace_ext4_ext_in_cache(inode, block, ret);
	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
	return ret;
}

/*
 * ext4_ext_in_cache()
 * Checks to see if the given block is in the cache.
 * If it is, the cached extent is stored in the given
 * extent pointer.
 *
 * @inode: The files inode
 * @block: The block to look for in the cache
 * @ex:    Pointer where the cached extent will be stored
 *         if it contains block
 *
 * Return 0 if cache is invalid; 1 if the cache is valid
 */
static int
ext4_ext_in_cache(struct inode *inode, ext4_lblk_t block,
			struct ext4_extent *ex)
{
	struct ext4_ext_cache cex;
	int ret = 0;

	if (ext4_ext_check_cache(inode, block, &cex)) {
		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);
		ret = 1;
	}

	return ret;
}


/*
 * ext4_ext_rm_idx:
 * removes index from the index block.
 */
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 = ext4_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;

	if (path->p_idx != EXT_LAST_INDEX(path->p_hdr)) {
		int len = EXT_LAST_INDEX(path->p_hdr) - path->p_idx;
		len *= sizeof(struct ext4_extent_idx);
		memmove(path->p_idx, path->p_idx + 1, len);
	}

	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);
	trace_ext4_ext_rm_idx(inode, leaf);

	ext4_free_blocks(handle, inode, NULL, 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 metadata 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_fsblk_t *partial_cluster,
			      ext4_lblk_t from, ext4_lblk_t to)
{
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	unsigned short ee_len =  ext4_ext_get_actual_len(ex);
	ext4_fsblk_t pblk;
	int flags = EXT4_FREE_BLOCKS_FORGET;

	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
		flags |= EXT4_FREE_BLOCKS_METADATA;
	/*
	 * For bigalloc file systems, we never free a partial cluster
	 * at the beginning of the extent.  Instead, we make a note
	 * that we tried freeing the cluster, and check to see if we
	 * need to free it on a subsequent call to ext4_remove_blocks,
	 * or at the end of the ext4_truncate() operation.
	 */
	flags |= EXT4_FREE_BLOCKS_NOFREE_FIRST_CLUSTER;

	trace_ext4_remove_blocks(inode, ex, from, to, *partial_cluster);
	/*
	 * If we have a partial cluster, and it's different from the
	 * cluster of the last block, we need to explicitly free the
	 * partial cluster here.
	 */
	pblk = ext4_ext_pblock(ex) + ee_len - 1;
	if (*partial_cluster && (EXT4_B2C(sbi, pblk) != *partial_cluster)) {
		ext4_free_blocks(handle, inode, NULL,
				 EXT4_C2B(sbi, *partial_cluster),
				 sbi->s_cluster_ratio, flags);
		*partial_cluster = 0;
	}

#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;

		num = le32_to_cpu(ex->ee_block) + ee_len - from;
		pblk = ext4_ext_pblock(ex) + ee_len - num;
		ext_debug("free last %u blocks starting %llu\n", num, pblk);
		ext4_free_blocks(handle, inode, NULL, pblk, num, flags);
		/*
		 * If the block range to be freed didn't start at the
		 * beginning of a cluster, and we removed the entire
		 * extent, save the partial cluster here, since we
		 * might need to delete if we determine that the
		 * truncate operation has removed all of the blocks in
		 * the cluster.
		 */
		if (pblk & (sbi->s_cluster_ratio - 1) &&
		    (ee_len == num))
			*partial_cluster = EXT4_B2C(sbi, pblk);
		else
			*partial_cluster = 0;
	} else if (from == le32_to_cpu(ex->ee_block)
		   && to <= le32_to_cpu(ex->ee_block) + ee_len - 1) {
		/* head removal */
		ext4_lblk_t num;
		ext4_fsblk_t start;

		num = to - from;
		start = ext4_ext_pblock(ex);

		ext_debug("free first %u blocks starting %llu\n", num, start);
		ext4_free_blocks(handle, inode, NULL, start, num, flags);

	} 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;
}


/*
 * ext4_ext_rm_leaf() Removes the extents associated with the
 * blocks appearing between "start" and "end", and splits the extents
 * if "start" and "end" appear in the same extent
 *
 * @handle: The journal handle
 * @inode:  The files inode
 * @path:   The path to the leaf
 * @start:  The first block to remove
 * @end:   The last block to remove
 */
static int
ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
		 struct ext4_ext_path *path, ext4_fsblk_t *partial_cluster,
		 ext4_lblk_t start, ext4_lblk_t end)
{
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	int err = 0, correct_index = 0;
	int depth = ext_depth(inode), credits;
	struct ext4_extent_header *eh;
	ext4_lblk_t a, b;
	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);

	trace_ext4_ext_rm_leaf(inode, start, ex, *partial_cluster);

	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 < end ?
			ex_ee_block+ex_ee_len - 1 : end;

		ext_debug("  border %u:%u\n", a, b);

		/* If this extent is beyond the end of the hole, skip it */
		if (end <= ex_ee_block) {
			ex--;
			ex_ee_block = le32_to_cpu(ex->ee_block);
			ex_ee_len = ext4_ext_get_actual_len(ex);
			continue;
		} else if (b != ex_ee_block + ex_ee_len - 1) {
			EXT4_ERROR_INODE(inode,"  bad truncate %u:%u\n",
					 start, end);
			err = -EIO;
			goto out;
		} else if (a != ex_ee_block) {
			/* remove tail of the extent */
			num = a - ex_ee_block;
		} else {
			/* remove whole extent: excellent! */
			num = 0;
		}
		/*
		 * 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, partial_cluster,
					 a, b);
		if (err)
			goto out;

		if (num == 0)
			/* this extent is removed; mark slot entirely unused */
			ext4_ext_store_pblock(ex, 0);

		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);
		/*
		 * If the extent was completely released,
		 * we need to remove it from the leaf
		 */
		if (num == 0) {
			if (end != EXT_MAX_BLOCKS - 1) {
				/*
				 * For hole punching, we need to scoot all the
				 * extents up when an extent is removed so that
				 * we dont have blank extents in the middle
				 */
				memmove(ex, ex+1, (EXT_LAST_EXTENT(eh) - ex) *
					sizeof(struct ext4_extent));

				/* Now get rid of the one at the end */
				memset(EXT_LAST_EXTENT(eh), 0,
					sizeof(struct ext4_extent));
			}
			le16_add_cpu(&eh->eh_entries, -1);
		} else
			*partial_cluster = 0;

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

		ext_debug("new extent: %u:%u:%llu\n", ex_ee_block, num,
				ext4_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 there is still a entry in the leaf node, check to see if
	 * it references the partial cluster.  This is the only place
	 * where it could; if it doesn't, we can free the cluster.
	 */
	if (*partial_cluster && ex >= EXT_FIRST_EXTENT(eh) &&
	    (EXT4_B2C(sbi, ext4_ext_pblock(ex) + ex_ee_len - 1) !=
	     *partial_cluster)) {
		int flags = EXT4_FREE_BLOCKS_FORGET;

		if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
			flags |= EXT4_FREE_BLOCKS_METADATA;

		ext4_free_blocks(handle, inode, NULL,
				 EXT4_C2B(sbi, *partial_cluster),
				 sbi->s_cluster_ratio, flags);
		*partial_cluster = 0;
	}

	/* 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;
	ext4_fsblk_t partial_cluster = 0;
	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);

	trace_ext4_ext_remove_space(inode, start, depth);

	/*
	 * 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,
					       &partial_cluster, start,
					       EXT_MAX_BLOCKS - 1);
			/* 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, ext4_idx_pblock(path[i].p_idx));
			memset(path + i + 1, 0, sizeof(*path));
			bh = sb_bread(sb, ext4_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);
		}
	}

	trace_ext4_ext_remove_space_done(inode, start, depth, partial_cluster,
			path->p_hdr->eh_entries);

	/* If we still have something in the partial cluster and we have removed
	 * even the first extent, then we should free the blocks in the partial
	 * cluster as well. */
	if (partial_cluster && path->p_hdr->eh_entries == 0) {
		int flags = EXT4_FREE_BLOCKS_FORGET;

		if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
			flags |= EXT4_FREE_BLOCKS_METADATA;

		ext4_free_blocks(handle, inode, NULL,
				 EXT4_C2B(EXT4_SB(sb), partial_cluster),
				 EXT4_SB(sb)->s_cluster_ratio, flags);
		partial_cluster = 0;
	}

	/* 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
}

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

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

	ret = sb_issue_zeroout(inode->i_sb, ee_pblock, ee_len, GFP_NOFS);
	if (ret > 0)
		ret = 0;

	return ret;
}

/*
 * used by extent splitting.
 */
#define EXT4_EXT_MAY_ZEROOUT	0x1  /* safe to zeroout if split fails \
					due to ENOSPC */
#define EXT4_EXT_MARK_UNINIT1	0x2  /* mark first half uninitialized */
#define EXT4_EXT_MARK_UNINIT2	0x4  /* mark second half uninitialized */

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

	ext_debug("ext4_split_extents_at: inode %lu, logical"
		"block %llu\n", inode->i_ino, (unsigned long long)split);

	ext4_ext_show_leaf(inode, path);

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

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

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

	if (split == ee_block) {
		/*
		 * case b: block @split is the block that the extent begins with
		 * then we just change the state of the extent, and splitting
		 * is not needed.
		 */
		if (split_flag & EXT4_EXT_MARK_UNINIT2)
			ext4_ext_mark_uninitialized(ex);
		else
			ext4_ext_mark_initialized(ex);

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

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

	/* case a */
	memcpy(&orig_ex, ex, sizeof(orig_ex));
	ex->ee_len = cpu_to_le16(split - ee_block);
	if (split_flag & EXT4_EXT_MARK_UNINIT1)
		ext4_ext_mark_uninitialized(ex);

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

	ex2 = &newex;
	ex2->ee_block = cpu_to_le32(split);
	ex2->ee_len   = cpu_to_le16(ee_len - (split - ee_block));
	ext4_ext_store_pblock(ex2, newblock);
	if (split_flag & EXT4_EXT_MARK_UNINIT2)
		ext4_ext_mark_uninitialized(ex2);

	err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
	if (err == -ENOSPC && (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
		err = ext4_ext_zeroout(inode, &orig_ex);
		if (err)
			goto fix_extent_len;
		/* update the extent length and mark as initialized */
		ex->ee_len = cpu_to_le16(ee_len);
		ext4_ext_try_to_merge(inode, path, ex);
		err = ext4_ext_dirty(handle, inode, path + depth);
		goto out;
	} else if (err)
		goto fix_extent_len;

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

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

/*
 * ext4_split_extents() splits an extent and mark extent which is covered
 * by @map as split_flags indicates
 *
 * It may result in splitting the extent into multiple extents (upto three)
 * There are three possibilities:
 *   a> There is no split required
 *   b> Splits in two extents: Split is happening at either end of the extent
 *   c> Splits in three extents: Somone is splitting in middle of the extent
 *
 */
static int ext4_split_extent(handle_t *handle,
			      struct inode *inode,
			      struct ext4_ext_path *path,
			      struct ext4_map_blocks *map,
			      int split_flag,
			      int flags)
{
	ext4_lblk_t ee_block;
	struct ext4_extent *ex;
	unsigned int ee_len, depth;
	int err = 0;
	int uninitialized;
	int split_flag1, flags1;

	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);
	uninitialized = ext4_ext_is_uninitialized(ex);

	if (map->m_lblk + map->m_len < ee_block + ee_len) {
		split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT ?
			      EXT4_EXT_MAY_ZEROOUT : 0;
		flags1 = flags | EXT4_GET_BLOCKS_PRE_IO;
		if (uninitialized)
			split_flag1 |= EXT4_EXT_MARK_UNINIT1 |
				       EXT4_EXT_MARK_UNINIT2;
		err = ext4_split_extent_at(handle, inode, path,
				map->m_lblk + map->m_len, split_flag1, flags1);
		if (err)
			goto out;
	}

	ext4_ext_drop_refs(path);
	path = ext4_ext_find_extent(inode, map->m_lblk, path);
	if (IS_ERR(path))
		return PTR_ERR(path);

	if (map->m_lblk >= ee_block) {
		split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT ?
			      EXT4_EXT_MAY_ZEROOUT : 0;
		if (uninitialized)
			split_flag1 |= EXT4_EXT_MARK_UNINIT1;
		if (split_flag & EXT4_EXT_MARK_UNINIT2)
			split_flag1 |= EXT4_EXT_MARK_UNINIT2;
		err = ext4_split_extent_at(handle, inode, path,
				map->m_lblk, split_flag1, flags);
		if (err)
			goto out;
	}

	ext4_ext_show_leaf(inode, path);
out:
	return err ? err : map->m_len;
}

#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 (up to 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
 *
 * Pre-conditions:
 *  - The extent pointed to by 'path' is uninitialized.
 *  - The extent pointed to by 'path' contains a superset
 *    of the logical span [map->m_lblk, map->m_lblk + map->m_len).
 *
 * Post-conditions on success:
 *  - the returned value is the number of blocks beyond map->l_lblk
 *    that are allocated and initialized.
 *    It is guaranteed to be >= map->m_len.
 */
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_header *eh;
	struct ext4_map_blocks split_map;
	struct ext4_extent zero_ex;
	struct ext4_extent *ex;
	ext4_lblk_t ee_block, eof_block;
	unsigned int ee_len, depth;
	int allocated;
	int err = 0;
	int split_flag = 0;

	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);

	trace_ext4_ext_convert_to_initialized_enter(inode, map, ex);

	/* Pre-conditions */
	BUG_ON(!ext4_ext_is_uninitialized(ex));
	BUG_ON(!in_range(map->m_lblk, ee_block, ee_len));

	/*
	 * Attempt to transfer newly initialized blocks from the currently
	 * uninitialized extent to its left neighbor. This is much cheaper
	 * than an insertion followed by a merge as those involve costly
	 * memmove() calls. This is the common case in steady state for
	 * workloads doing fallocate(FALLOC_FL_KEEP_SIZE) followed by append
	 * writes.
	 *
	 * Limitations of the current logic:
	 *  - L1: we only deal with writes at the start of the extent.
	 *    The approach could be extended to writes at the end
	 *    of the extent but this scenario was deemed less common.
	 *  - L2: we do not deal with writes covering the whole extent.
	 *    This would require removing the extent if the transfer
	 *    is possible.
	 *  - L3: we only attempt to merge with an extent stored in the
	 *    same extent tree node.
	 */
	if ((map->m_lblk == ee_block) &&	/*L1*/
		(map->m_len < ee_len) &&	/*L2*/
		(ex > EXT_FIRST_EXTENT(eh))) {	/*L3*/
		struct ext4_extent *prev_ex;
		ext4_lblk_t prev_lblk;
		ext4_fsblk_t prev_pblk, ee_pblk;
		unsigned int prev_len, write_len;

		prev_ex = ex - 1;
		prev_lblk = le32_to_cpu(prev_ex->ee_block);
		prev_len = ext4_ext_get_actual_len(prev_ex);
		prev_pblk = ext4_ext_pblock(prev_ex);
		ee_pblk = ext4_ext_pblock(ex);
		write_len = map->m_len;

		/*
		 * A transfer of blocks from 'ex' to 'prev_ex' is allowed
		 * upon those conditions:
		 * - C1: prev_ex is initialized,
		 * - C2: prev_ex is logically abutting ex,
		 * - C3: prev_ex is physically abutting ex,
		 * - C4: prev_ex can receive the additional blocks without
		 *   overflowing the (initialized) length limit.
		 */
		if ((!ext4_ext_is_uninitialized(prev_ex)) &&		/*C1*/
			((prev_lblk + prev_len) == ee_block) &&		/*C2*/
			((prev_pblk + prev_len) == ee_pblk) &&		/*C3*/
			(prev_len < (EXT_INIT_MAX_LEN - write_len))) {	/*C4*/
			err = ext4_ext_get_access(handle, inode, path + depth);
			if (err)
				goto out;

			trace_ext4_ext_convert_to_initialized_fastpath(inode,
				map, ex, prev_ex);

			/* Shift the start of ex by 'write_len' blocks */
			ex->ee_block = cpu_to_le32(ee_block + write_len);
			ext4_ext_store_pblock(ex, ee_pblk + write_len);
			ex->ee_len = cpu_to_le16(ee_len - write_len);
			ext4_ext_mark_uninitialized(ex); /* Restore the flag */

			/* Extend prev_ex by 'write_len' blocks */
			prev_ex->ee_len = cpu_to_le16(prev_len + write_len);

			/* Mark the block containing both extents as dirty */
			ext4_ext_dirty(handle, inode, path + depth);

			/* Update path to point to the right extent */
			path[depth].p_ext = prev_ex;

			/* Result: number of initialized blocks past m_lblk */
			allocated = write_len;
			goto out;
		}
	}

	WARN_ON(map->m_lblk < ee_block);
	/*
	 * It is safe to convert extent to initialized via explicit
	 * zeroout only if extent is fully insde i_size or new_size.
	 */
	split_flag |= ee_block + ee_len <= eof_block ? EXT4_EXT_MAY_ZEROOUT : 0;

	/* If extent has less than 2*EXT4_EXT_ZERO_LEN zerout directly */
	if (ee_len <= 2*EXT4_EXT_ZERO_LEN &&
	    (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
		err = ext4_ext_zeroout(inode, ex);
		if (err)
			goto out;

		err = ext4_ext_get_access(handle, inode, path + depth);
		if (err)
			goto out;
		ext4_ext_mark_initialized(ex);
		ext4_ext_try_to_merge(inode, path, ex);
		err = ext4_ext_dirty(handle, inode, path + depth);
		goto out;
	}

	/*
	 * four cases:
	 * 1. split the extent into three extents.
	 * 2. split the extent into two extents, zeroout the first half.
	 * 3. split the extent into two extents, zeroout the second half.
	 * 4. split the extent into two extents with out zeroout.
	 */
	split_map.m_lblk = map->m_lblk;
	split_map.m_len = map->m_len;

	if (allocated > map->m_len) {
		if (allocated <= EXT4_EXT_ZERO_LEN &&
		    (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
			/* case 3 */
			zero_ex.ee_block =
					 cpu_to_le32(map->m_lblk);
			zero_ex.ee_len = cpu_to_le16(allocated);
			ext4_ext_store_pblock(&zero_ex,
				ext4_ext_pblock(ex) + map->m_lblk - ee_block);
			err = ext4_ext_zeroout(inode, &zero_ex);
			if (err)
				goto out;
			split_map.m_lblk = map->m_lblk;
			split_map.m_len = allocated;
		} else if ((map->m_lblk - ee_block + map->m_len <
			   EXT4_EXT_ZERO_LEN) &&
			   (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
			/* case 2 */
			if (map->m_lblk != ee_bloc