[RFC] extents support for EXT3

[Alex Tomas <bzzz@tmi.comex.ru>]

this is 2nd version of the patch. changes:
  - error handling seems completed
  - lots of cleanups and comments
  - few minor bug fixed

this version of the patch tries to solve couple
of corner cases:
  - very long truncate
  - rewrite 

it survived dbench, bonnie++ and fsx tests.

take a look at numbers I've just got, please.

                      before      after
5GB file, creation:   2m31.197s   2m21.933s
5GB file, read:       2m25.439s   2m24.833s
5GB file, rewrite:    2m48.434s   2m20.958s
5GB file, removal:    0m8.760s    0m0.858s

             before           after
dbench 16:   99.9868 MB/sec   179.243 MB/sec 16 procs
dbench 16:   89.9919 MB/sec   203.119 MB/sec 16 procs
dbench 16:   73.5519 MB/sec   185.815 MB/sec 16 procs
dbench 16:   94.6312 MB/sec   188.519 MB/sec 16 procs


to use extents you have to use 'extents' mount option

Alex

 fs/ext3/Makefile           |    2 
 fs/ext3/extents.c          | 1571 +++++++++++++++++++++++++++++++++++++++++++++
 fs/ext3/ialloc.c           |    2 
 fs/ext3/inode.c            |   25 
 fs/ext3/super.c            |   11 
 include/linux/ext3_fs.h    |   17 
 include/linux/ext3_fs_i.h  |    4 
 include/linux/ext3_fs_sb.h |   10 
 8 files changed, 1636 insertions(+), 6 deletions(-)

diff -puN /dev/null fs/ext3/extents.c
--- /dev/null	2003-01-30 13:24:37.000000000 +0300
+++ linux-2.6.0-test2-uml-alexey/fs/ext3/extents.c	2003-08-25 21:12:35.000000000 +0400
@@ -0,0 +1,1571 @@
+/*
+ *
+ * linux/fs/ext3/extents.c
+ *
+ * Extents support for EXT3
+ *
+ * 07/08/2003    Alex Tomas <bzzz@tmi.comex.ru>
+ * 
+ * TODO:
+ *   - ext3*_error() should be used in some situations
+ *   - find_goal() [to be tested and improved]
+ *   - quick search for index/leaf in ext3_ext_find_extent()
+ *   - tree reduction
+ *   - cache last found extent
+ *   - arch-independent
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/time.h>
+#include <linux/ext3_jbd.h>
+#include <linux/jbd.h>
+#include <linux/smp_lock.h>
+#include <linux/highuid.h>
+#include <linux/pagemap.h>
+#include <linux/quotaops.h>
+#include <linux/string.h>
+#include <linux/buffer_head.h>
+#include <linux/writeback.h>
+#include <linux/mpage.h>
+
+/*
+ * with AGRESSIVE_TEST defined capacity of index/leaf blocks
+ * become very little, so index split, in-depth growing and
+ * other hard changes happens much more often
+ * this is for debug purposes only
+ */
+#define AGRESSIVE_TEST_
+
+/*
+ * if EXT_DEBUG defined you can use 'extdebug' mount option
+ * to get lots of info what's going on
+ */
+#define EXT_DEBUG
+#ifdef EXT_DEBUG
+#define ext_debug(inode,fmt,a...) 		\
+do {						\
+	if (test_opt((inode)->i_sb, EXTDEBUG))	\
+		printk(fmt, ##a);		\
+} while (0);
+#else
+#define ext_debug(inode,fmt,a...)
+#endif
+
+#define EXT3_ALLOC_NEEDED	2	/* block bitmap + group descriptor */
+
+/*
+ * ext3_inode has i_block array (total 60 bytes)
+ * first 4 bytes are used to store:
+ *  - tree depth (0 mean there is no tree yet. all extents in the inode)
+ *  - number of alive extents in the inode
+ */
+
+/*
+ * this is extent on-disk structure
+ * it's used at the bottom of the tree
+ */
+struct ext3_extent {
+	__u32	e_block;	/* first logical block extent covers */
+	__u32	e_start;	/* first physical block extents lives */
+	__u32	e_num;		/* number of blocks covered by extent */
+};
+
+/*
+ * this is index on-disk structure
+ * it's used at all the levels, but the bottom
+ */
+struct ext3_extent_idx {
+	__u32	e_block;	/* index covers logical blocks from 'block' */
+	__u32	e_leaf;		/* pointer to the physical block of the next *
+				 * level. leaf or next index could bet here */
+};
+
+/*
+ * each block (leaves and indexes), even inode-stored has header
+ */
+struct ext3_extent_header {	
+	__u16	e_num;		/* number of valid entries */
+	__u16	e_max;		/* capacity of store in entries */
+};
+
+/*
+ * array of ext3_ext_path contains path to some extent
+ * creation/lookup routines use it for traversal/splitting/etc
+ * truncate uses it to simulate recursive walking
+ */
+struct ext3_ext_path {
+	__u32				p_block;
+	__u16				p_depth;
+	struct ext3_extent		*p_ext;
+	struct ext3_extent_idx		*p_idx;
+	struct ext3_extent_header	*p_hdr;
+	struct buffer_head		*p_bh;
+};
+
+#define EXT_FIRST_EXTENT(__hdr__) \
+	((struct ext3_extent *) (((char *) (__hdr__)) +		\
+				 sizeof(struct ext3_extent_header)))
+#define EXT_FIRST_INDEX(__hdr__) \
+	((struct ext3_extent_idx *) (((char *) (__hdr__)) +	\
+				     sizeof(struct ext3_extent_header)))
+#define EXT_HAS_FREE_INDEX(__path__) \
+	((__path__)->p_hdr->e_num < (__path__)->p_hdr->e_max)
+#define EXT_LAST_EXTENT(__hdr__) \
+	(EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->e_num - 1)
+#define EXT_LAST_INDEX(__hdr__) \
+	(EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->e_num - 1)
+#define EXT_MAX_EXTENT(__hdr__) \
+	(EXT_FIRST_EXTENT((__hdr__)) + (__hdr__)->e_max - 1)
+#define EXT_MAX_INDEX(__hdr__) \
+	(EXT_FIRST_INDEX((__hdr__)) + (__hdr__)->e_max - 1)
+
+
+#define EXT_ASSERT(__x__) if (!(__x__)) BUG();
+
+/*
+ * could return:
+ *  - EROFS
+ *  - ENOMEM
+ */
+static int ext3_ext_get_access(handle_t *handle, struct inode *inode,
+				struct ext3_ext_path *path)
+{
+	if (path->p_bh) {
+		/* path points to block */
+		return ext3_journal_get_write_access(handle, path->p_bh);
+	}
+
+	/* path points to leaf/index in inode body */
+	return 0;
+}
+
+/*
+ * could return:
+ *  - EROFS
+ *  - ENOMEM
+ *  - EIO
+ */
+static int ext3_ext_dirty(handle_t *handle, struct inode *inode,
+				struct ext3_ext_path *path)
+{
+	if (path->p_bh) {
+		/* path points to block */
+		return ext3_journal_dirty_metadata(handle, path->p_bh);
+	}
+
+	/* path points to leaf/index in inode body */
+	return ext3_mark_inode_dirty(handle, inode);
+}
+
+static inline int ext3_ext_space_block(struct inode *inode)
+{
+	int size;
+
+	size = (inode->i_sb->s_blocksize - sizeof(struct ext3_extent_header))
+		/ sizeof(struct ext3_extent);
+#ifdef AGRESSIVE_TEST
+	size = 6; /* FIXME: for debug, remove this line */
+#endif
+	return size;
+}
+
+static inline int ext3_ext_space_inode(struct inode *inode)
+{
+	int size;
+
+	size = (sizeof(EXT3_I(inode)->i_data) -
+			sizeof(struct ext3_extent_header))
+			/ sizeof(struct ext3_extent);
+#ifdef AGRESSIVE_TEST
+	size = 3; /* FIXME: for debug, remove this line */
+#endif
+	return size;
+}
+
+static inline int ext3_ext_space_inode_idx(struct inode *inode)
+{
+	int size;
+
+	size = (sizeof(EXT3_I(inode)->i_data) -
+			sizeof(struct ext3_extent_header))
+			/ sizeof(struct ext3_extent_idx);
+#ifdef AGRESSIVE_TEST
+	size = 4; /* FIXME: for debug, remove this line */
+#endif
+	return size;
+}
+
+static void ext3_ext_show_path(struct inode *inode, struct ext3_ext_path *path)
+{
+	int k, l = path->p_depth;
+
+	ext_debug(inode, "path:");
+	for (k = 0; k <= l; k++, path++) {
+		if (path->p_idx) {
+			ext_debug(inode, "  %d->%d", path->p_idx->e_block,
+					path->p_idx->e_leaf);
+		} else if (path->p_ext) {
+			ext_debug(inode, "  %d:%d:%d",
+					path->p_ext->e_block,
+					path->p_ext->e_start,
+					path->p_ext->e_num);
+		} else
+			ext_debug(inode, "  []");
+	}
+	ext_debug(inode, "\n");
+}
+
+static void ext3_ext_show_leaf(struct inode *inode, struct ext3_ext_path *path)
+{
+	int depth = EXT3_I(inode)->i_depth;
+	struct ext3_extent_header *eh = path[depth].p_hdr;
+	struct ext3_extent *ex = EXT_FIRST_EXTENT(eh);
+	int i;
+
+	for (i = 0; i < eh->e_num; i++, ex++) {
+		ext_debug(inode, "%d:%d:%d ",
+				ex->e_block, ex->e_start, ex->e_num);
+	}
+	ext_debug(inode, "\n");
+}
+
+static void ext3_ext_drop_refs(struct inode *inode, struct ext3_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;
+		}
+}
+
+static int ext3_ext_find_goal(struct inode *inode, struct ext3_ext_path *path)
+{
+	struct ext3_inode_info *ei = EXT3_I(inode);
+	unsigned long bg_start;
+	unsigned long colour;
+	int depth;
+	
+	if (path) {
+		depth = path->p_depth;
+		/* try to find previous block */
+		if (path[depth].p_ext)
+			return path[depth].p_ext->e_start +
+				path[depth].p_ext->e_num - 1;
+		
+		/* it looks index is empty
+		 * try to find starting from index itself */
+		if (path[depth].p_bh)
+			return path[depth].p_bh->b_blocknr;
+	}
+
+	/* OK. use inode's group */
+	bg_start = (ei->i_block_group * EXT3_BLOCKS_PER_GROUP(inode->i_sb)) +
+		le32_to_cpu(EXT3_SB(inode->i_sb)->s_es->s_first_data_block);
+	colour = (current->pid % 16) *
+			(EXT3_BLOCKS_PER_GROUP(inode->i_sb) / 16);
+	return bg_start + colour;
+}
+
+static struct ext3_ext_path *
+ext3_ext_find_extent(struct inode *inode, int block, struct ext3_ext_path *path)
+{
+	struct ext3_inode_info *ei = EXT3_I(inode);
+	struct ext3_extent_header *eh = (void *) ei->i_data;
+	struct ext3_extent_idx *ix;
+	struct buffer_head *bh;
+	struct ext3_extent *ex;
+	int depth, i, k, ppos = 0;
+	
+	eh = (struct ext3_extent_header *) ei->i_data;
+
+	/* initialize capacity of leaf in inode for first time */
+	if (eh->e_max == 0)
+		eh->e_max = ext3_ext_space_inode(inode);
+	i = depth = ei->i_depth;
+	EXT_ASSERT(i == 0 || eh->e_num > 0);
+	
+	/* account possible depth increase */
+	if (!path) {
+		path = kmalloc(sizeof(struct ext3_ext_path) * (depth + 2),
+				GFP_NOFS);
+		if (!path)
+			return ERR_PTR(-ENOMEM);
+	}
+	memset(path, 0, sizeof(struct ext3_ext_path) * (depth + 1));
+
+	/* walk through the tree */
+	while (i) {
+		ext_debug(inode, "depth %d: num %d, max %d\n",
+				ppos, eh->e_num, eh->e_max);
+		ix = EXT_FIRST_INDEX(eh);
+		if (eh->e_num)
+			path[ppos].p_idx = ix;
+		EXT_ASSERT(eh->e_num <= eh->e_max);
+		for (k = 0; k < eh->e_num; k++, ix++) {
+			ext_debug(inode, "index: %d -> %d\n",
+					ix->e_block, ix->e_leaf);
+			if (block < ix->e_block)
+				break;
+			path[ppos].p_idx = ix;
+		}
+		path[ppos].p_block = path[ppos].p_idx->e_leaf;
+		path[ppos].p_depth = i;
+		path[ppos].p_hdr = eh;
+		path[ppos].p_ext = NULL;
+
+		bh = sb_bread(inode->i_sb, path[ppos].p_block);
+		if (!bh) {
+			ext3_ext_drop_refs(inode, path);
+			kfree(path);
+			return ERR_PTR(-EIO);
+		}
+		eh = (struct ext3_extent_header *) bh->b_data;
+		ppos++;
+		EXT_ASSERT(ppos <= depth);
+		path[ppos].p_bh = bh;
+		i--;
+	}
+
+	path[ppos].p_depth = i;
+	path[ppos].p_hdr = eh;
+	path[ppos].p_ext = NULL;
+	
+	/* find extent */
+	ex = EXT_FIRST_EXTENT(eh);
+	if (eh->e_num)
+		path[ppos].p_ext = ex;
+	EXT_ASSERT(eh->e_num <= eh->e_max);
+	for (k = 0; k < eh->e_num; k++, ex++) {
+		if (block < ex->e_block) 
+			break;
+		path[ppos].p_ext = ex;
+	}
+
+	ext3_ext_show_path(inode, path);
+
+	return path;
+}
+
+static void ext3_ext_check_boundary(struct inode *inode,
+					struct ext3_ext_path *curp,
+					void *addr, int len)
+{
+	void *end;
+
+	if (!len)
+		return;
+	if (curp->p_bh)
+		end = (void *) curp->p_hdr + inode->i_sb->s_blocksize;
+	else
+		end = (void *) curp->p_hdr + sizeof(EXT3_I(inode)->i_data);
+	if (((unsigned long) addr) + len > (unsigned long) end) {
+		printk("overflow! 0x%p > 0x%p\n", addr + len, end);
+		BUG();
+	}
+	if ((unsigned long) addr < (unsigned long) curp->p_hdr) {
+		printk("underflow! 0x%p < 0x%p\n", addr, curp->p_hdr);
+		BUG();
+	}
+}
+
+/*
+ * insert new index [logical;ptr] into the block at cupr
+ * it check where to insert: before curp or after curp
+ */
+static int ext3_ext_insert_index(handle_t *handle, struct inode *inode,
+				struct ext3_ext_path *curp, int logical,
+				int ptr)
+{
+	struct ext3_extent_idx *ix;
+	int len, err;
+
+	if ((err = ext3_ext_get_access(handle, inode, curp)))
+		return err;
+
+	EXT_ASSERT(logical != curp->p_idx->e_block);
+	len = EXT_MAX_INDEX(curp->p_hdr) - curp->p_idx;
+	if (logical > curp->p_idx->e_block) {
+		/* insert after */
+		len = (len - 1) * sizeof(struct ext3_extent_idx);
+		len = len < 0 ? 0 : len;
+		ext_debug(inode, "insert new index %d after: %d. "
+				"move %d from 0x%p to 0x%p\n",
+				logical, ptr, len,
+				(curp->p_idx + 1), (curp->p_idx + 2));
+
+		ext3_ext_check_boundary(inode, curp, curp->p_idx + 2, len);
+		memmove(curp->p_idx + 2, curp->p_idx + 1, len);
+		ix = curp->p_idx + 1;
+	} else {
+		/* insert before */
+		len = len * sizeof(struct ext3_extent_idx);
+		len = len < 0 ? 0 : len;
+		ext_debug(inode, "insert new index %d before: %d. "
+				"move %d from 0x%p to 0x%p\n",
+				logical, ptr, len,
+				curp->p_idx, (curp->p_idx + 1));
+
+		ext3_ext_check_boundary(inode, curp, curp->p_idx + 1, len);
+		memmove(curp->p_idx + 1, curp->p_idx, len);
+		ix = curp->p_idx;
+	}
+
+	ix->e_block = logical;
+	ix->e_leaf = ptr;
+	curp->p_hdr->e_num++;
+
+	err = ext3_ext_dirty(handle, inode, curp);
+	ext3_std_error(inode->i_sb, err);
+
+	return err;
+}
+
+/*
+ * routine 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 extens and index entries (right to the split point)
+ *    into the newly allocated blocks
+ *  - initialize subtree
+ */
+static int ext3_ext_split(handle_t *handle, struct inode *inode,
+				struct ext3_ext_path *path,
+				struct ext3_extent *newext, int at)
+{
+	struct buffer_head *bh = NULL;
+	int depth = EXT3_I(inode)->i_depth;
+	struct ext3_extent_header *neh;
+	struct ext3_extent_idx *fidx;
+	struct ext3_extent *ex;
+	int i = at, k, m, a;
+	sector_t newblock, oldblock, border;
+	int *ablocks = NULL; /* array of allocated blocks */
+	int err = 0;
+
+	/* make decision: where to split? */
+	/* FIXME: now desicion is simplest: at current extent */
+
+	/* if current leaf will be splitted, then we should use 
+	 * border from split point */
+	if (path[depth].p_ext != EXT_MAX_EXTENT(path[depth].p_hdr)) {
+		border = path[depth].p_ext[1].e_block;
+		ext_debug(inode, "leaf will be splitted."
+				" next leaf starts at %d\n",
+				(int)border);
+	} else {
+		border = newext->e_block;
+		ext_debug(inode, "leaf will be added."
+				" next leaf starts at %d\n",
+				(int)border);
+	}
+
+	/* 
+	 * if error occurs, then we break processing
+	 * and turn filesystem read-only. so, 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 = kmalloc(sizeof(sector_t) * depth, GFP_NOFS);
+	if (!ablocks)
+		return -ENOMEM;
+	memset(ablocks, 0, sizeof(sector_t) * depth);
+
+	/* allocate all needed blocks */
+	ext_debug(inode, "allocate %d blocks for indexes and leaf\n",
+			depth - at);
+	ablocks[0] = newext->e_start++;
+	newext->e_num--;
+	for (a = 1; a < depth - at; a++) {
+		newblock = ext3_new_block(handle, inode, newext->e_start,
+						0, 0, &err);
+		if (newblock == 0)
+			goto cleanup;
+		ablocks[a] = newblock;
+	}
+
+	/* initialize new leaf */
+	newblock = ablocks[--a];
+	EXT_ASSERT(newblock);
+	bh = sb_getblk(inode->i_sb, newblock);
+	if (!bh) {
+		err = -EIO;
+		goto cleanup;
+	}
+	lock_buffer(bh);
+
+	if ((err = ext3_journal_get_create_access(handle, bh)))
+		goto cleanup;
+
+	neh = (struct ext3_extent_header *) bh->b_data;
+	neh->e_num = 0;
+	neh->e_max = ext3_ext_space_block(inode);
+	ex = EXT_FIRST_EXTENT(neh);
+
+	/* move remain of path[depth] to the new leaf */
+	EXT_ASSERT(path[depth].p_hdr->e_num ==
+			path[depth].p_hdr->e_max);
+	/* 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(inode, "move %d:%d:%d in new leaf\n",
+				path[depth].p_ext->e_block,
+				path[depth].p_ext->e_start,
+				path[depth].p_ext->e_num);
+		memmove(ex++, path[depth].p_ext++,
+				sizeof(struct ext3_extent));
+		neh->e_num++;
+		m++;
+	}
+	set_buffer_uptodate(bh);
+	unlock_buffer(bh);
+
+	if ((err = ext3_journal_dirty_metadata(handle, bh)))
+		goto cleanup;	
+	brelse(bh);
+	bh = NULL;
+
+	/* correct old leaf */
+	if (m) {
+		if ((err = ext3_ext_get_access(handle, inode, path)))
+			goto cleanup;
+		path[depth].p_hdr->e_num -= m;
+		if ((err = ext3_ext_dirty(handle, inode, path)))
+			goto cleanup;
+		
+	}
+
+	/* create intermediate indexes */
+	k = depth - at - 1;
+	EXT_ASSERT(k >= 0);
+	if (k)
+		ext_debug(inode,
+				"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);
+
+		if ((err = ext3_journal_get_create_access(handle, bh)))
+			goto cleanup;
+
+		neh = (struct ext3_extent_header *) bh->b_data;
+		neh->e_num = 1;
+		neh->e_max = ext3_ext_space_block(inode);
+		fidx = EXT_FIRST_INDEX(neh);
+		fidx->e_block = border;
+		fidx->e_leaf = oldblock;
+
+		ext_debug(inode,
+				"int.index at %d (block %u): %d -> %d\n",
+				i, (unsigned) newblock,
+				(int) border,
+				(int) oldblock);
+		/* copy indexes */
+		m = 0;
+		path[i].p_idx++;
+		EXT_ASSERT(EXT_MAX_INDEX(path[i].p_hdr) ==
+				EXT_LAST_INDEX(path[i].p_hdr));
+		ext_debug(inode, "cur 0x%p, last 0x%p\n", path[i].p_idx,
+				EXT_MAX_INDEX(path[i].p_hdr));
+		while (path[i].p_idx <=
+				EXT_MAX_INDEX(path[i].p_hdr)) {
+			ext_debug(inode, "%d: move %d:%d in new index\n",
+					i, path[i].p_idx->e_block,
+					path[i].p_idx->e_leaf);
+			memmove(++fidx, path[i].p_idx++,
+					sizeof(struct ext3_extent_idx));
+			neh->e_num++;
+			m++;
+		}
+
+		set_buffer_uptodate(bh);
+		unlock_buffer(bh);
+
+		if ((err = ext3_journal_dirty_metadata(handle, bh)))
+			goto cleanup;
+		brelse(bh);
+		bh = NULL;
+
+		/* correct old index */
+		if (m) {
+			err = ext3_ext_get_access(handle,inode,path+i);
+			if (err)
+				goto cleanup;
+			path[i].p_hdr->e_num -= m;
+			err = ext3_ext_dirty(handle, inode, path + i);
+			if (err)
+				goto cleanup;
+		}
+
+		i--;
+	}
+
+	/* insert new index */
+	if (!err) 
+		err = ext3_ext_insert_index(handle, inode, path + at,
+						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;
+			ext3_free_blocks(handle, inode, ablocks[i], 1);
+	}
+	kfree(ablocks);
+
+	return err;
+}
+
+/*
+ * routine implements tree growing procedure:
+ *  - allocates new block
+ *  - moves top-level data (index block or leaf) into the new block
+ *  - initialize new top-level, creating index that points to the
+ *    just created block
+ */
+static int ext3_ext_grow_indepth(handle_t *handle, struct inode *inode,
+					struct ext3_ext_path *path,
+					struct ext3_extent *newext)
+{
+	struct buffer_head *bh;
+	struct ext3_ext_path *curp = path;
+	struct ext3_extent_header *neh;
+	struct ext3_extent_idx *fidx;
+	int len, err = 0;
+	sector_t newblock;
+
+	/*
+	 * use already allocated by the called block for new root block
+	 */
+	newblock = newext->e_start++;
+	newext->e_num--;
+	
+	bh = sb_getblk(inode->i_sb, newblock);
+	if (!bh) {
+		err = -EIO;
+		ext3_std_error(inode->i_sb, err);
+		return err;
+	}
+	lock_buffer(bh);
+
+	if ((err = ext3_journal_get_create_access(handle, bh))) {
+		unlock_buffer(bh);
+		goto out;	
+	}
+
+	/* move top-level index/leaf into new block */
+	len = sizeof(struct ext3_extent_header) +
+		sizeof(struct ext3_extent) * curp->p_hdr->e_max;
+	EXT_ASSERT(len >= 0 && len < 4096);
+	memmove(bh->b_data, curp->p_hdr, len);
+
+	/* set size of new block */
+	neh = (struct ext3_extent_header *) bh->b_data;
+	neh->e_max = ext3_ext_space_block(inode);
+	set_buffer_uptodate(bh);
+	unlock_buffer(bh);
+
+	if ((err = ext3_journal_dirty_metadata(handle, bh)))
+		goto out;
+
+	/* create index in new top-level index: num,max,pointer */
+	if ((err = ext3_ext_get_access(handle, inode, curp)))
+		goto out;
+
+	curp->p_hdr->e_max = ext3_ext_space_inode_idx(inode);
+	curp->p_hdr->e_num = 1;
+	curp->p_idx = EXT_FIRST_INDEX(curp->p_hdr);
+	curp->p_idx->e_block = EXT_FIRST_EXTENT(path[0].p_hdr)->e_block;
+	curp->p_idx->e_leaf = newblock;
+
+	neh = (struct ext3_extent_header *) EXT3_I(inode)->i_data;
+	fidx = EXT_FIRST_INDEX(neh);
+	ext_debug(inode, "new root: num %d(%d), lblock %d, ptr %d\n",
+			neh->e_num, neh->e_max, fidx->e_block, fidx->e_leaf); 
+
+	EXT3_I(inode)->i_depth++;
+	err = ext3_ext_dirty(handle, inode, curp);
+out:
+	brelse(bh);
+
+	return err;
+}
+
+/*
+ * routine finds empty index and adds new leaf. if no free index found
+ * then it requests in-depth growing
+ */
+static int ext3_ext_create_new_leaf(handle_t *handle, struct inode *inode,
+					struct ext3_ext_path *path,
+					struct ext3_extent *newext)
+{
+	int depth = EXT3_I(inode)->i_depth;
+	struct ext3_ext_path *curp;
+	int i = depth, err = 0;
+	sector_t newblock = newext->e_start;
+
+	/* 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 contigoues */
+	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 = ext3_ext_split(handle, inode, path, newext, i);
+	} else {
+		/* tree is full, time to grow in depth */
+		err = ext3_ext_grow_indepth(handle, inode, path, newext);
+	}
+
+	if (!err) {
+		/* refill path */
+		ext3_ext_drop_refs(inode, path);
+		path = ext3_ext_find_extent(inode, newext->e_block, path);
+		if (IS_ERR(path))
+			err = PTR_ERR(path);
+
+		/*
+		 * probably we've used some blocks from extent
+		 * let's allocate new block for it
+		 */
+		if (newext->e_num == 0 && !err) {
+			newext->e_start =
+				ext3_new_block(handle, inode, newblock,
+						0, 0, &err);
+			newext->e_num = 1;
+		}
+	}
+
+	return err;
+}
+
+/*
+ * returns next allocated block or 0xffffffff
+ * NOTE: it consider block number from index entry as
+ * allocated block. thus, index entries have to be consistent
+ * with leafs
+ */
+static inline unsigned ext3_ext_next_allocated_block(struct inode *inode,
+                                               struct ext3_ext_path *path)
+{
+	int depth;
+
+	EXT_ASSERT(path != NULL);
+	depth = path->p_depth;
+
+	if (depth == 0 && path->p_ext == NULL)
+		return 0xffffffff;
+
+	/* FIXME: what if index isn't full ?! */
+	while (depth >= 0) {
+		if (depth == path->p_depth) {
+			/* leaf */
+			if (path[depth].p_ext !=
+					EXT_LAST_EXTENT(path[depth].p_hdr))
+				return path[depth].p_ext[1].e_block;
+		} else {
+			/* index */
+			if (path[depth].p_idx !=
+					EXT_LAST_INDEX(path[depth].p_hdr))
+				return path[depth].p_idx[1].e_block;
+		}
+		depth--;        
+	}
+
+	return 0xffffffff;
+}
+
+/*
+ * returns first allocated block from next leaf or 0xffffffff
+ */
+static unsigned ext3_ext_next_leaf_block(struct inode *inode,
+                                               struct ext3_ext_path *path)
+{
+	int depth;
+
+	EXT_ASSERT(path != NULL);
+	depth = path->p_depth;
+
+	/* zero-tree has no leaf blocks at all */
+	if (depth == 0)
+		return 0xffffffff;
+
+	/* go to index block */
+	depth--;
+	
+	while (depth >= 0) {
+		if (path[depth].p_idx !=
+				EXT_LAST_INDEX(path[depth].p_hdr))
+			return path[depth].p_idx[1].e_block;
+		depth--;        
+	}
+
+	return 0xffffffff;
+}
+
+/*
+ * 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?
+ */
+int ext3_ext_correct_indexes(handle_t *handle, struct inode *inode,
+				struct ext3_ext_path *path)
+{
+	int depth = EXT3_I(inode)->i_depth;	
+	struct ext3_extent_header *eh;
+	struct ext3_extent *ex;
+	sector_t border;
+	int k, err = 0;
+	
+	eh = path[depth].p_hdr;
+	ex = path[depth].p_ext;
+
+	EXT_ASSERT(ex);
+	EXT_ASSERT(eh);
+	
+	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;
+	}
+	
+	k = depth - 1;
+	border = path[depth].p_ext->e_block;
+	if ((err = ext3_ext_get_access(handle, inode, path + k)))
+		return err;
+	path[k].p_idx->e_block = border;
+	if ((err = ext3_ext_dirty(handle, inode, path + k)))
+		return err;
+
+	while (k--) {
+		/* change all left-side indexes */
+		if (path[k].p_idx != EXT_FIRST_INDEX(path[k].p_hdr)
+				&& k != 0)
+			break;
+		if ((err = ext3_ext_get_access(handle, inode, path + k)))
+			break;
+		path[k].p_idx->e_block = border;
+		if ((err = ext3_ext_dirty(handle, inode, path + k)))
+			break;
+	}
+
+	return err;
+}
+
+/*
+ * this routine tries to merge requsted extent into the existing
+ * extent or inserts requested extent as new one into the tree,
+ * creating new leaf in no-space case
+ */
+int ext3_ext_insert_extent(handle_t *handle, struct inode *inode,
+				struct ext3_ext_path *path,
+				struct ext3_extent *newext)
+{
+	int depth, len;
+	struct ext3_extent_header * eh;
+	struct ext3_extent *ex;
+	struct ext3_extent *nearex; /* nearest extent */
+	struct ext3_ext_path *npath = NULL;
+	int err;
+
+	depth = EXT3_I(inode)->i_depth;	
+	if ((ex = path[depth].p_ext)) {
+		/* try to insert block into found extent and return */
+		if (ex->e_block + ex->e_num == newext->e_block &&
+				ex->e_start + ex->e_num == newext->e_start) {
+#ifdef AGRESSIVE_TEST
+			if (ex->e_num >= 2)
+				goto repeat;
+#endif
+			if ((err = ext3_ext_get_access(handle, inode,
+							path + depth)))
+				return err;
+			ext_debug(inode, "append %d block to %d:%d (from %d)\n",
+					newext->e_num, ex->e_block, ex->e_num,
+					ex->e_start);
+			ex->e_num += newext->e_num;
+			err = ext3_ext_dirty(handle, inode, path + depth);
+			return err;
+		}
+	}
+
+repeat:
+	depth = EXT3_I(inode)->i_depth;	
+	eh = path[depth].p_hdr;
+	if (eh->e_num == eh->e_max) {
+		/* probably next leaf has space for us? */
+		int next = ext3_ext_next_leaf_block(inode, path);
+		if (next != 0xffffffff) {
+			ext_debug(inode, "next leaf block - %d\n", next);
+			EXT_ASSERT(!npath);
+			npath = ext3_ext_find_extent(inode, next, NULL);
+			if (IS_ERR(npath))
+				return PTR_ERR(npath);
+			EXT_ASSERT(npath->p_depth == path->p_depth);
+			eh = npath[depth].p_hdr;
+			if (eh->e_num < eh->e_max) {
+				ext_debug(inode,
+						"next leaf has free ext(%d)\n",
+						eh->e_num);
+				path = npath;
+				goto repeat;
+			}
+			ext_debug(inode, "next leaf hasno free space(%d,%d)\n",
+					eh->e_num, eh->e_max);
+		}
+		/*
+		 * there is no free space in found leaf
+		 * we're gonna add new leaf in the tree
+		 */
+		err = ext3_ext_create_new_leaf(handle, inode, path, newext);
+		if (err)
+			goto cleanup;
+		goto repeat;
+	}
+
+	nearex = path[depth].p_ext;
+
+	if ((err = ext3_ext_get_access(handle, inode, path + depth)))
+		goto cleanup;
+
+	if (!nearex) {
+		/* there is no extent in this leaf, create first one */
+		ext_debug(inode, "first extent in the leaf: %d:%d:%d\n",
+				newext->e_block, newext->e_start,
+				newext->e_num);
+		eh->e_num++;
+		path[depth].p_ext = EXT_FIRST_EXTENT(eh);
+
+	} else if (newext->e_block > nearex->e_block) {
+		EXT_ASSERT(newext->e_block != nearex->e_block);
+		len = EXT_MAX_EXTENT(eh) - nearex;
+		len = (len - 1) * sizeof(struct ext3_extent);
+		len = len < 0 ? 0 : len;
+		ext_debug(inode, "insert %d:%d:%d after: nearest 0x%p, "
+				"move %d from 0x%p to 0x%p\n",
+				newext->e_block, newext->e_start, newext->e_num,
+				nearex, len, nearex + 1, nearex + 2);
+		ext3_ext_check_boundary(inode, path + depth, nearex + 2, len);
+		memmove(nearex + 2, nearex + 1, len);
+		path[depth].p_ext = nearex + 1;
+		eh->e_num++;
+	} else {
+		EXT_ASSERT(newext->e_block != nearex->e_block);
+		len = (EXT_MAX_EXTENT(eh) - nearex) * sizeof(struct ext3_extent);
+		len = len < 0 ? 0 : len;
+		ext_debug(inode, "insert %d:%d:%d before: nearest 0x%p, "
+				"move %d from 0x%p to 0x%p\n",
+				newext->e_block, newext->e_start, newext->e_num,
+				nearex, len, nearex + 1, nearex + 2);
+		memmove(nearex + 1, nearex, len);
+		path[depth].p_ext = nearex;
+		eh->e_num++;
+
+		/* time to correct all indexes above */
+		err = ext3_ext_correct_indexes(handle, inode, path);
+	}
+
+	if (!err) {
+		nearex = path[depth].p_ext;
+		nearex->e_block = newext->e_block;
+		nearex->e_start = newext->e_start;
+		nearex->e_num = newext->e_num;
+	}
+
+	err = ext3_ext_dirty(handle, inode, path + depth);
+
+cleanup:
+	if (npath) {
+		ext3_ext_drop_refs(inode, npath);
+		kfree(npath);
+	}
+		
+	return err;
+}
+
+int ext3_ext_get_block(handle_t *handle, struct inode *inode, sector_t iblock,
+			struct buffer_head *bh_result, int create,
+			int extend_disksize)
+{
+	struct ext3_ext_path *path;
+	int depth = EXT3_I(inode)->i_depth;
+	struct ext3_extent newex;
+	struct ext3_extent *ex;
+	int goal, newblock, err = 0;
+
+	ext_debug(inode, "block %d requested for inode %u, bh_result 0x%p\n",
+			(int) iblock, (unsigned) inode->i_ino, bh_result);
+	clear_buffer_new(bh_result);
+
+	down(&EXT3_I(inode)->i_ext_sem);
+
+	/* find extent for this block */
+	path = ext3_ext_find_extent(inode, iblock, NULL);
+	if (IS_ERR(path)) {
+		err = PTR_ERR(path);
+		goto out2;
+	}
+
+	if ((ex = path[depth].p_ext)) {
+		/* if found exent covers block, simple return it */
+		if (iblock >= ex->e_block && iblock < ex->e_block + ex->e_num) {
+			newblock = iblock - ex->e_block + ex->e_start;
+			ext_debug(inode, "%d fit into %d:%d -> %d\n",
+					(int) iblock, ex->e_block, ex->e_num,
+					newblock);
+			goto out;
+		}
+	}
+
+	/*
+	 * we couldn't try to create block if create flag is zero 
+	 */
+	if (!create) 
+		goto out2;
+
+	/* allocate new block */
+	goal = ext3_ext_find_goal(inode, path);
+	newblock = ext3_new_block(handle, inode, goal, 0, 0, &err);
+	if (!newblock)
+		goto out2;
+	ext_debug(inode, "allocate new block: goal %d, found %d\n",
+			goal, newblock);
+
+	/* try to insert new extent into found leaf and return */
+	newex.e_block = iblock;
+	newex.e_start = newblock;
+	newex.e_num = 1;
+	err = ext3_ext_insert_extent(handle, inode, path, &newex);
+	if (err)
+		goto out2;
+	
+	/* previous routine could use block we allocated */
+	newblock = newex.e_start;
+	set_buffer_new(bh_result);
+
+out:
+	ext3_ext_show_leaf(inode, path);
+	map_bh(bh_result, inode->i_sb, newblock);
+out2:
+	ext3_ext_drop_refs(inode, path);
+	kfree(path);
+	up(&EXT3_I(inode)->i_ext_sem);
+
+	return err;	
+}
+
+/*
+ * returns 1 if current index have to be freed (even partial)
+ */
+static int ext3_ext_more_to_truncate(struct inode *inode,
+				struct ext3_ext_path *path)
+{
+	EXT_ASSERT(path->p_idx);
+
+	if (path->p_idx < EXT_FIRST_INDEX(path->p_hdr))
+		return 0;
+
+	/*
+	 * if truncate on deeper level happened it it wasn't partial
+	 * so we have to consider current index for truncation
+	 */
+	if (path->p_hdr->e_num == path->p_block)
+		return 0;
+
+	/*
+	 * put actual number of indexes to know is this number got
+	 * changed at the next iteration
+	 */
+	path->p_block = path->p_hdr->e_num;
+	
+	return 1;
+}
+
+/*
+ * routine removes index from the index block
+ * it's used in truncate case only. thus all requests are for
+ * last index in the block only
+ */
+int ext3_ext_remove_index(handle_t *handle, struct inode *inode,
+					struct ext3_ext_path *path)
+{
+	struct buffer_head *bh;
+	int err;
+	
+	/* free index block */
+	path--;
+	EXT_ASSERT(path->p_hdr->e_num);
+	if ((err = ext3_ext_get_access(handle, inode, path)))
+		return err;
+	path->p_hdr->e_num--;
+	if ((err = ext3_ext_dirty(handle, inode, path)))
+		return err;
+	bh = sb_find_get_block(inode->i_sb, path->p_idx->e_leaf);
+	ext3_forget(handle, 0, inode, bh, path->p_idx->e_leaf);
+	ext3_free_blocks(handle, inode, path->p_idx->e_leaf, 1);
+
+	ext_debug(inode, "index is empty, remove it, free block %d\n",
+			path->p_idx->e_leaf);
+	return err;
+}
+
+/*
+ * returns 1 if current extent needs to be freed (even partial)
+ * instead, returns 0
+ */
+int ext3_ext_more_leaves_to_truncate(struct inode *inode,
+					struct ext3_ext_path *path)
+{
+	unsigned blocksize = inode->i_sb->s_blocksize;
+	struct ext3_extent *ex = path->p_ext;
+	int last_block; 
+
+	EXT_ASSERT(ex);
+
+	/* is there leave in the current leaf? */
+	if (ex < EXT_FIRST_EXTENT(path->p_hdr))
+		return 0;
+	
+	last_block = (inode->i_size + blocksize-1)
+			>> EXT3_BLOCK_SIZE_BITS(inode->i_sb);
+
+	if (last_block >= ex->e_block + ex->e_num)
+		return 0;
+
+	/* seems it extent have to be freed */
+	return 1;
+}
+
+handle_t *ext3_ext_journal_restart(handle_t *handle, int needed)
+{
+	int err;
+
+	if (handle->h_buffer_credits > needed)
+		return handle;
+	if (!ext3_journal_extend(handle, needed))
+		return handle;
+	err = ext3_journal_restart(handle, needed);
+	
+	return handle;
+}
+
+/*
+ * this routine calculate max number of blocks to be modified
+ * while freeing extent and is intended to be used in truncate path
+ */
+static int ext3_ext_calc_credits(struct inode *inode,
+					struct ext3_ext_path *path,
+					int num)
+{
+	int depth = EXT3_I(inode)->i_depth;
+	int needed;
+	
+	/*
+	 * extent couldn't cross group, so we will modify
+	 * single bitmap block and single group descriptor
+	 */
+	needed = 2;
+
+	/*
+	 * if this is last extent in a leaf, then we have to
+	 * free leaf block and remove pointer from index above.
+	 * that pointer could be last in index block, so we'll
+	 * have to remove it too. this way we could modify/free
+	 * the whole path + root index (inode stored) will be
+	 * modified
+	 */
+	if (!path || (num == path->p_ext->e_num &&
+				path->p_ext == EXT_FIRST_EXTENT(path->p_hdr)))
+		needed += (depth * EXT3_ALLOC_NEEDED) + 1;
+
+	return needed;
+}
+
+/*
+ * core of the truncate procedure:
+ * - calculated what part of each extent in the requested leaf
+ *   need to be freed
+ * - frees and forgets these blocks
+ *
+ * TODO: we could optimize and free several extents during
+ *       single journal_restart()-journal_restart() cycle
+ */
+static int ext3_ext_truncate_leaf(handle_t *handle,
+					struct inode *inode,
+					struct ext3_ext_path *path,
+					int depth)
+{
+	unsigned blocksize = inode->i_sb->s_blocksize;
+	int last_block; 
+	int i, err = 0, sf, num;
+
+	ext_debug(inode, "level %d - leaf\n", depth);
+	if (!path->p_hdr)
+		path->p_hdr =
+			(struct ext3_extent_header *) path->p_bh->b_data;
+
+	EXT_ASSERT(path->p_hdr->e_num <= path->p_hdr->e_max);
+	
+	last_block = (inode->i_size + blocksize-1)
+					>> EXT3_BLOCK_SIZE_BITS(inode->i_sb);
+	path->p_ext = EXT_LAST_EXTENT(path->p_hdr);
+	while (ext3_ext_more_leaves_to_truncate(inode, path)) {
+
+		/* what part of extent have to be freed? */
+		sf = last_block > path->p_ext->e_block ?
+			last_block : path->p_ext->e_block;
+
+		/* number of blocks from extent to be freed */
+		num = path->p_ext->e_block + path->p_ext->e_num - sf;
+
+		/* calc physical first physical block to be freed */
+		sf = path->p_ext->e_start + (sf - path->p_ext->e_block);
+
+		i = ext3_ext_calc_credits(inode, path, num);
+		handle = ext3_ext_journal_restart(handle, i);
+		if (IS_ERR(handle))
+			return PTR_ERR(handle);
+		
+		ext_debug(inode, "free extent %d:%d:%d -> free %d:%d\n",
+				path->p_ext->e_block, path->p_ext->e_start,
+				path->p_ext->e_num, sf, num);
+		for (i = 0; i < num; i++) {
+			struct buffer_head *bh =
+				sb_find_get_block(inode->i_sb, sf + i);
+			ext3_forget(handle, 0, inode, bh, sf + i);
+		}
+		ext3_free_blocks(handle, inode, sf, num);
+
+		/* collect extents usage stats */
+		spin_lock(&EXT3_SB(inode->i_sb)->s_ext_lock);
+		EXT3_SB(inode->i_sb)->s_ext_extents++;
+		EXT3_SB(inode->i_sb)->s_ext_blocks += num;
+		spin_unlock(&EXT3_SB(inode->i_sb)->s_ext_lock);
+
+		/* reduce extent */
+		if ((err = ext3_ext_get_access(handle, inode, path)))
+			return err;
+		path->p_ext->e_num -= num;
+		if (path->p_ext->e_num == 0)
+			path->p_hdr->e_num--;
+		if ((err = ext3_ext_dirty(handle, inode, path)))
+			return err;
+
+		path->p_ext--;
+	}
+	
+	/* if this leaf is free, then we should
+	 * remove it from index block above */
+	if (path->p_hdr->e_num == 0 && depth > 0) 
+		err = ext3_ext_remove_index(handle, inode, path);
+
+	return err;
+}
+
+static void ext3_ext_collect_stats(struct inode *inode)
+{
+	int depth;
+	
+	/* skip inodes with old good bitmap */
+	if (!(EXT3_I(inode)->i_flags & EXT3_EXTENTS_FL))
+		return;
+	
+	/* collect on full truncate only */
+	if (inode->i_size)
+		return;
+
+	depth = EXT3_I(inode)->i_depth;
+	if (depth < EXT3_SB(inode->i_sb)->s_ext_mindepth)
+		 EXT3_SB(inode->i_sb)->s_ext_mindepth = depth;
+	if (depth > EXT3_SB(inode->i_sb)->s_ext_maxdepth)
+		 EXT3_SB(inode->i_sb)->s_ext_maxdepth = depth;
+	EXT3_SB(inode->i_sb)->s_ext_sum += depth;
+	EXT3_SB(inode->i_sb)->s_ext_count++;
+	
+}
+
+void ext3_ext_truncate(struct inode * inode)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct ext3_ext_path *path;
+	struct page * page;
+	handle_t *handle;
+	int i, depth, err = 0;
+
+	down(&EXT3_I(inode)->i_ext_sem);
+
+	ext3_ext_collect_stats(inode);
+
+	/*
+	 * We have to lock the EOF page here, because lock_page() nests
+	 * outside journal_start().
+	 */
+	if ((inode->i_size & (inode->i_sb->s_blocksize - 1)) == 0) {
+		/* Block boundary? Nothing to do */
+		page = NULL;
+	} else {
+		page = grab_cache_page(mapping,
+				inode->i_size >> PAGE_CACHE_SHIFT);
+		if (!page) {
+			up(&EXT3_I(inode)->i_ext_sem);
+			return;
+		}
+	}
+
+	/*
+	 * probably first extent we're gonna free will be last in block
+	 */
+	i = ext3_ext_calc_credits(inode, NULL, 0);
+	handle = ext3_journal_start(inode, i);
+	if (IS_ERR(handle)) {
+		if (page) {
+			clear_highpage(page);
+			flush_dcache_page(page);
+			unlock_page(page);
+			page_cache_release(page);
+		}
+		up(&EXT3_I(inode)->i_ext_sem);
+		return;
+	}
+
+	if (page)
+		ext3_block_truncate_page(handle, page, mapping, inode->i_size);
+
+	/* 
+	 * TODO: optimization is possible here
+	 * probably we need not scaning at all,
+	 * because page truncation is enough
+	 */
+	if (ext3_orphan_add(handle, inode))
+		goto out_stop;
+
+	/* we have to know where to truncate from in crash case */
+	EXT3_I(inode)->i_disksize = inode->i_size;
+	ext3_mark_inode_dirty(handle, inode);
+
+	/*
+	 * we start scanning from right side freeing all the blocks
+	 * after i_size and walking into the deep
+	 */
+	i = 0;
+	depth = EXT3_I(inode)->i_depth;
+	path = kmalloc(sizeof(struct ext3_ext_path) * (depth + 1), GFP_KERNEL);
+	if (IS_ERR(path)) {
+		ext3_error(inode->i_sb, "ext3_ext_truncate",
+				"Can't allocate path array");
+		goto out_stop;
+	}
+	memset(path, 0, sizeof(struct ext3_ext_path) * (depth + 1));
+
+	path[i].p_hdr = (struct ext3_extent_header *) EXT3_I(inode)->i_data;
+	while (i >= 0 && err == 0) {
+		if (i == depth) {
+			/* this is leaf block */
+			err = ext3_ext_truncate_leaf(handle, inode,
+							path + i, i);
+			/* root level have p_bh == NULL, brelse() eats this */
+			brelse(path[i].p_bh);
+			i--;
+			continue;
+		}
+		
+		/* this is index block */
+		if (!path[i].p_hdr) {
+			path[i].p_hdr =
+				(struct ext3_extent_header *) path[i].p_bh->b_data;
+			ext_debug(inode, "initialize header\n");
+		}
+
+		EXT_ASSERT(path[i].p_hdr->e_num <= path[i].p_hdr->e_max);
+		
+		if (!path[i].p_idx) {
+			/* this level hasn't touched yet */
+			path[i].p_idx = EXT_LAST_INDEX(path[i].p_hdr);
+			path[i].p_block = path[i].p_hdr->e_num + 1;
+			ext_debug(inode, "init index ptr: hdr 0x%p, num %d\n",
+					path[i].p_hdr, path[i].p_hdr->e_num);
+		} else {
+			/* we've already was here, see at next index */
+			path[i].p_idx--;
+		}
+
+		ext_debug(inode, "level %d - index, first 0x%p, cur 0x%p\n",
+				i, EXT_FIRST_INDEX(path[i].p_hdr),
+				path[i].p_idx);
+		if (ext3_ext_more_to_truncate(inode, path + i)) {
+			/* go to the next level */
+			ext_debug(inode, "move to level %d (block %d)\n", i+1,
+					path[i].p_idx->e_leaf);
+			memset(path + i + 1, 0, sizeof(*path));
+			path[i+1].p_bh = sb_bread(inode->i_sb,
+							path[i].p_idx->e_leaf);
+			if (!path[i+1].p_bh) {
+				/* should we reset i_size? */
+				err = -EIO;
+				break;
+			}
+			i++;
+		} else {
+			/* we finish processing this index, go up */
+			if (path[i].p_hdr->e_num == 0 && i > 0) {
+				/* index is empty, remove it
+				 * handle must be already prepared by the
+				 * truncate_leaf()
+				 */
+				err = ext3_ext_remove_index(handle, inode,
+								path + i);
+			}
+			/* root level have p_bh == NULL, brelse() eats this */
+			brelse(path[i].p_bh);
+			i--;
+			ext_debug(inode, "return to level %d\n", i);
+		}
+	}
+
+	/* TODO: flexible tree reduction should be here */
+	if (path->p_hdr->e_num == 0) {
+		/*
+		 * truncate to zero freed all the tree
+		 * so, we need to correct i_depth
+		 */
+		EXT3_I(inode)->i_depth = 0;
+		path->p_hdr->e_max = 0;
+		ext3_mark_inode_dirty(handle, inode);
+	}
+
+	kfree(path);
+
+	/* In a multi-transaction truncate, we only make the final
+	 * transaction synchronous */
+	if (IS_SYNC(inode))
+		handle->h_sync = 1;
+
+out_stop:
+	/*
+	 * 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
+	 * ext3_delete_inode(), and we allow that function to clean up the
+	 * orphan info for us.
+	 */
+	if (inode->i_nlink)
+		ext3_orphan_del(handle, inode);
+
+	up(&EXT3_I(inode)->i_ext_sem);
+	ext3_journal_stop(handle);
+}
+
+/*
+ * this routine calculate max number of blocks we could modify
+ * in order to allocate new block for an inode
+ */
+int ext3_ext_writepage_trans_blocks(struct inode *inode, int num)
+{
+	struct ext3_inode_info *ei = EXT3_I(inode);
+	int depth = ei->i_depth + 1;
+	int needed;
+	
+	/*
+	 * the worste case we're expecting is creation of the
+	 * new root (growing in depth) with index splitting
+	 * for splitting we have to consider depth + 1 because
+	 * previous growing could increase it
+	 */
+
+	/* 
+	 * growing in depth:
+	 * block allocation + new root + old root
+	 */
+	needed = EXT3_ALLOC_NEEDED + 2;
+
+	/* index split. we may need:
+	 *   allocate intermediate indexes and new leaf
+	 *   change two blocks at each level, but root
+	 *   modify root block (inode)
+	 */
+	needed += (depth * EXT3_ALLOC_NEEDED) + (2 * depth) + 1;
+
+	/* caller want to allocate num blocks */
+	needed *= num;
+	
+#ifdef CONFIG_QUOTA
+	/* 
+	 * FIXME: real calculation should be here
+	 * it depends on blockmap format of qouta file
+	 */
+	needed += 2 * EXT3_SINGLEDATA_TRANS_BLOCKS;
+#endif
+
+	return needed;
+}
+
+/*
+ * called at mount time
+ */
+void ext3_ext_init(struct super_block *sb)
+{
+	/*
+	 * possible initialization would be here
+	 */
+
+	if (test_opt(sb, EXTENTS))
+		printk("EXT3-fs: file extents enabled\n");
+	spin_lock_init(&EXT3_SB(sb)->s_ext_lock);
+}
+
+/*
+ * called at umount time
+ */
+void ext3_ext_release(struct super_block *sb)
+{
+	struct ext3_sb_info *sbi = EXT3_SB(sb);
+
+	/* show collected stats */
+	if (sbi->s_ext_count && sbi->s_ext_extents)
+		printk("EXT3-fs: min depth - %d, max depth - %d, "
+				"ave. depth - %d, ave. blocks/extent - %d\n",
+				sbi->s_ext_mindepth,
+				sbi->s_ext_maxdepth,
+				sbi->s_ext_sum / sbi->s_ext_count,
+				sbi->s_ext_blocks / sbi->s_ext_extents);
+}
+
diff -puN fs/ext3/ialloc.c~ext3-extents fs/ext3/ialloc.c
--- linux-2.6.0-test2-uml/fs/ext3/ialloc.c~ext3-extents	2003-08-19 08:53:27.000000000 +0400
+++ linux-2.6.0-test2-uml-alexey/fs/ext3/ialloc.c	2003-08-19 08:53:27.000000000 +0400
@@ -600,6 +600,8 @@ got:
 		DQUOT_FREE_INODE(inode);
 		goto fail2;
   	}
+	if (test_opt(sb, EXTENTS))
+		EXT3_I(inode)->i_flags |= EXT3_EXTENTS_FL;
 	err = ext3_mark_inode_dirty(handle, inode);
 	if (err) {
 		ext3_std_error(sb, err);
diff -puN fs/ext3/inode.c~ext3-extents fs/ext3/inode.c
--- linux-2.6.0-test2-uml/fs/ext3/inode.c~ext3-extents	2003-08-19 08:53:27.000000000 +0400
+++ linux-2.6.0-test2-uml-alexey/fs/ext3/inode.c	2003-08-19 08:53:27.000000000 +0400
@@ -862,6 +862,15 @@ changed:
 	goto reread;
 }
 
+static inline int
+ext3_get_block_wrap(handle_t *handle, struct inode *inode, sector_t block,
+		struct buffer_head *bh, int create, int extend_disksize)
+{
+	if (EXT3_I(inode)->i_flags & EXT3_EXTENTS_FL)
+		return ext3_ext_get_block(handle, inode, block, bh, create, 1);
+	return ext3_get_block_handle(handle, inode, block, bh, create, 1);
+}
+
 static int ext3_get_block(struct inode *inode, sector_t iblock,
 			struct buffer_head *bh_result, int create)
 {
@@ -872,7 +881,7 @@ static int ext3_get_block(struct inode *
 		handle = ext3_journal_current_handle();
 		J_ASSERT(handle != 0);
 	}
-	ret = ext3_get_block_handle(handle, inode, iblock,
+	ret = ext3_get_block_wrap(handle, inode, iblock,
 				bh_result, create, 1);
 	return ret;
 }
@@ -899,7 +908,7 @@ ext3_direct_io_get_blocks(struct inode *
 		}
 	}
 	if (ret == 0)
-		ret = ext3_get_block_handle(handle, inode, iblock,
+		ret = ext3_get_block_wrap(handle, inode, iblock,
 					bh_result, create, 0);
 	if (ret == 0)
 		bh_result->b_size = (1 << inode->i_blkbits);
@@ -921,7 +930,7 @@ struct buffer_head *ext3_getblk(handle_t
 	dummy.b_state = 0;
 	dummy.b_blocknr = -1000;
 	buffer_trace_init(&dummy.b_history);
-	*errp = ext3_get_block_handle(handle, inode, block, &dummy, create, 1);
+	*errp = ext3_get_block_wrap(handle, inode, block, &dummy, create, 1);
 	if (!*errp && buffer_mapped(&dummy)) {
 		struct buffer_head *bh;
 		bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
@@ -1663,7 +1672,7 @@ void ext3_set_aops(struct inode *inode)
  * This required during truncate. We need to physically zero the tail end
  * of that block so it doesn't yield old data if the file is later grown.
  */
-static int ext3_block_truncate_page(handle_t *handle, struct page *page,
+int ext3_block_truncate_page(handle_t *handle, struct page *page,
 		struct address_space *mapping, loff_t from)
 {
 	unsigned long index = from >> PAGE_CACHE_SHIFT;
@@ -2145,6 +2154,9 @@ void ext3_truncate(struct inode * inode)
 
 	ext3_discard_prealloc(inode);
 
+	if (EXT3_I(inode)->i_flags & EXT3_EXTENTS_FL)
+		return ext3_ext_truncate(inode);
+
 	/*
 	 * We have to lock the EOF page here, because lock_page() nests
 	 * outside journal_start().
@@ -2540,6 +2552,7 @@ void ext3_read_inode(struct inode * inod
 	ei->i_prealloc_count = 0;
 #endif
 	ei->i_block_group = iloc.block_group;
+	ei->i_depth = raw_inode->osd2.linux2.l_i_depth;
 
 	/*
 	 * NOTE! The in-memory inode i_data array is in little-endian order
@@ -2636,6 +2649,7 @@ static int ext3_do_update_inode(handle_t
 	raw_inode->i_frag = ei->i_frag_no;
 	raw_inode->i_fsize = ei->i_frag_size;
 #endif
+ 	raw_inode->osd2.linux2.l_i_depth = ei->i_depth;
 	raw_inode->i_file_acl = cpu_to_le32(ei->i_file_acl);
 	if (!S_ISREG(inode->i_mode)) {
 		raw_inode->i_dir_acl = cpu_to_le32(ei->i_dir_acl);
@@ -2840,6 +2854,9 @@ int ext3_writepage_trans_blocks(struct i
 	int indirects = (EXT3_NDIR_BLOCKS % bpp) ? 5 : 3;
 	int ret;
 
+	if (EXT3_I(inode)->i_flags & EXT3_EXTENTS_FL)
+		return ext3_ext_writepage_trans_blocks(inode, bpp);
+
 	if (ext3_should_journal_data(inode))
 		ret = 3 * (bpp + indirects) + 2;
 	else
diff -puN fs/ext3/Makefile~ext3-extents fs/ext3/Makefile
--- linux-2.6.0-test2-uml/fs/ext3/Makefile~ext3-extents	2003-08-19 08:53:27.000000000 +0400
+++ linux-2.6.0-test2-uml-alexey/fs/ext3/Makefile	2003-08-19 08:53:27.000000000 +0400
@@ -5,7 +5,7 @@
 obj-$(CONFIG_EXT3_FS) += ext3.o
 
 ext3-y	:= balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o \
-	   ioctl.o namei.o super.o symlink.o hash.o
+	   ioctl.o namei.o super.o symlink.o hash.o extents.o
 
 ext3-$(CONFIG_EXT3_FS_XATTR)	 += xattr.o xattr_user.o xattr_trusted.o
 ext3-$(CONFIG_EXT3_FS_POSIX_ACL) += acl.o
diff -puN fs/ext3/super.c~ext3-extents fs/ext3/super.c
--- linux-2.6.0-test2-uml/fs/ext3/super.c~ext3-extents	2003-08-19 08:53:27.000000000 +0400
+++ linux-2.6.0-test2-uml-alexey/fs/ext3/super.c	2003-08-25 21:08:33.000000000 +0400
@@ -446,6 +446,7 @@ void ext3_put_super (struct super_block 
 	struct ext3_super_block *es = sbi->s_es;
 	int i;
 
+	ext3_ext_release(sb);
 	ext3_xattr_put_super(sb);
 	journal_destroy(sbi->s_journal);
 	if (!(sb->s_flags & MS_RDONLY)) {
@@ -504,6 +505,8 @@ static struct inode *ext3_alloc_inode(st
 	ei->i_default_acl = EXT3_ACL_NOT_CACHED;
 #endif
 	ei->vfs_inode.i_version = 1;
+	ei->i_depth = 0;
+	sema_init(&ei->i_ext_sem, 1);
 	return &ei->vfs_inode;
 }
 
@@ -656,6 +659,12 @@ static int parse_options (char * options
 			continue;
 		if ((value = strchr (this_char, '=')) != NULL)
 			*value++ = 0;
+		if (!strcmp (this_char, "extents"))
+			set_opt (sbi->s_mount_opt, EXTENTS);
+		else
+		if (!strcmp (this_char, "extdebug"))
+			set_opt (sbi->s_mount_opt, EXTDEBUG);
+		else
 #ifdef CONFIG_EXT3_FS_XATTR
 		if (!strcmp (this_char, "user_xattr"))
 			set_opt (sbi->s_mount_opt, XATTR_USER);
@@ -1442,6 +1451,8 @@ static int ext3_fill_super (struct super
 	percpu_counter_mod(&sbi->s_dirs_counter,
 		ext3_count_dirs(sb));
 
+	ext3_ext_init(sb);
+
 	return 0;
 
 failed_mount3:
diff -puN include/linux/ext3_fs.h~ext3-extents include/linux/ext3_fs.h
--- linux-2.6.0-test2-uml/include/linux/ext3_fs.h~ext3-extents	2003-08-19 08:53:27.000000000 +0400
+++ linux-2.6.0-test2-uml-alexey/include/linux/ext3_fs.h	2003-08-19 08:53:27.000000000 +0400
@@ -186,6 +186,7 @@ struct ext3_group_desc
 #define EXT3_DIRSYNC_FL			0x00010000 /* dirsync behaviour (directories only) */
 #define EXT3_TOPDIR_FL			0x00020000 /* Top of directory hierarchies*/
 #define EXT3_RESERVED_FL		0x80000000 /* reserved for ext3 lib */
+#define EXT3_EXTENTS_FL			0x00080000 /* Inode uses extents */
 
 #define EXT3_FL_USER_VISIBLE		0x0003DFFF /* User visible flags */
 #define EXT3_FL_USER_MODIFIABLE		0x000380FF /* User modifiable flags */
@@ -244,7 +245,7 @@ struct ext3_inode {
 		struct {
 			__u8	l_i_frag;	/* Fragment number */
 			__u8	l_i_fsize;	/* Fragment size */
-			__u16	i_pad1;
+			__u16	l_i_depth;
 			__u16	l_i_uid_high;	/* these 2 fields    */
 			__u16	l_i_gid_high;	/* were reserved2[0] */
 			__u32	l_i_reserved2;
@@ -324,6 +325,8 @@ struct ext3_inode {
 #define EXT3_MOUNT_NO_UID32		0x2000  /* Disable 32-bit UIDs */
 #define EXT3_MOUNT_XATTR_USER		0x4000	/* Extended user attributes */
 #define EXT3_MOUNT_POSIX_ACL		0x8000	/* POSIX Access Control Lists */
+#define EXT3_MOUNT_EXTENTS		0x10000	/* Extents support */
+#define EXT3_MOUNT_EXTDEBUG		0x20000	/* Extents debug */
 
 /* Compatibility, for having both ext2_fs.h and ext3_fs.h included at once */
 #ifndef _LINUX_EXT2_FS_H
@@ -733,6 +736,11 @@ extern int ext3_change_inode_journal_fla
 extern void ext3_truncate (struct inode *);
 extern void ext3_set_inode_flags(struct inode *);
 extern void ext3_set_aops(struct inode *inode);
+extern int ext3_block_truncate_page(handle_t *handle, struct page *page,
+					struct address_space *mapping, loff_t from);
+extern int ext3_forget(handle_t *handle, int is_metadata,
+		       struct inode *inode, struct buffer_head *bh,
+		       int blocknr);
 
 /* ioctl.c */
 extern int ext3_ioctl (struct inode *, struct file *, unsigned int,
@@ -789,6 +797,13 @@ extern struct inode_operations ext3_spec
 extern struct inode_operations ext3_symlink_inode_operations;
 extern struct inode_operations ext3_fast_symlink_inode_operations;
 
+/* extents.c */
+extern int ext3_ext_writepage_trans_blocks(struct inode *, int);
+extern int ext3_ext_get_block(handle_t *, struct inode *, sector_t,
+				struct buffer_head *, int, int);
+extern void ext3_ext_truncate(struct inode *);
+extern void ext3_ext_init(struct super_block *);
+extern void ext3_ext_release(struct super_block *);
 
 #endif	/* __KERNEL__ */
 
diff -puN include/linux/ext3_fs_i.h~ext3-extents include/linux/ext3_fs_i.h
--- linux-2.6.0-test2-uml/include/linux/ext3_fs_i.h~ext3-extents	2003-08-19 08:53:27.000000000 +0400
+++ linux-2.6.0-test2-uml-alexey/include/linux/ext3_fs_i.h	2003-08-25 21:08:33.000000000 +0400
@@ -108,6 +108,10 @@ struct ext3_inode_info {
 	 */
 	struct rw_semaphore truncate_sem;
 	struct inode vfs_inode;
+
+	/* extents-related data */
+	struct semaphore i_ext_sem;
+	__u16 i_depth;
 };
 
 #endif	/* _LINUX_EXT3_FS_I */
diff -puN include/linux/ext3_fs_sb.h~ext3-extents include/linux/ext3_fs_sb.h
--- linux-2.6.0-test2-uml/include/linux/ext3_fs_sb.h~ext3-extents	2003-08-19 08:53:27.000000000 +0400
+++ linux-2.6.0-test2-uml-alexey/include/linux/ext3_fs_sb.h	2003-08-19 08:53:27.000000000 +0400
@@ -68,6 +68,16 @@ struct ext3_sb_info {
 	struct timer_list turn_ro_timer;	/* For turning read-only (crash simulation) */
 	wait_queue_head_t ro_wait_queue;	/* For people waiting for the fs to go read-only */
 #endif
+
+	/* extents */
+	int s_ext_debug;
+	int s_ext_mindepth;
+	int s_ext_maxdepth;
+	int s_ext_sum;
+	int s_ext_count;
+	spinlock_t s_ext_lock;
+	int s_ext_extents;
+	int s_ext_blocks;
 };
 
 #endif	/* _LINUX_EXT3_FS_SB */

_