diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 56f9271..af7b626 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -699,6 +699,8 @@ struct ext4_inode_info {
 	unsigned int i_reserved_meta_blocks;
 	unsigned int i_allocated_meta_blocks;
 	unsigned short i_delalloc_reserved_flag;
+	sector_t i_da_metadata_calc_last_lblock;
+	int i_da_metadata_calc_len;
 
 	/* on-disk additional length */
 	__u16 i_extra_isize;
diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
index 2ca6864..bdb6ce7 100644
--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -225,7 +225,8 @@ static inline void ext4_ext_mark_initialized(struct ext4_extent *ext)
 	ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext));
 }
 
-extern int ext4_ext_calc_metadata_amount(struct inode *inode, int blocks);
+extern int ext4_ext_calc_metadata_amount(struct inode *inode,
+					 sector_t lblocks);
 extern ext4_fsblk_t ext_pblock(struct ext4_extent *ex);
 extern ext4_fsblk_t idx_pblock(struct ext4_extent_idx *);
 extern void ext4_ext_store_pblock(struct ext4_extent *, ext4_fsblk_t);
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 91ae460..7d7b74e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -296,29 +296,44 @@ static inline int ext4_ext_space_root_idx(struct inode *inode, int check)
  * to allocate @blocks
  * Worse case is one block per extent
  */
-int ext4_ext_calc_metadata_amount(struct inode *inode, int blocks)
+int ext4_ext_calc_metadata_amount(struct inode *inode, sector_t lblock)
 {
-	int lcap, icap, rcap, leafs, idxs, num;
-	int newextents = blocks;
-
-	rcap = ext4_ext_space_root_idx(inode, 0);
-	lcap = ext4_ext_space_block(inode, 0);
-	icap = ext4_ext_space_block_idx(inode, 0);
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	int idxs, num = 0;
 
-	/* number of new leaf blocks needed */
-	num = leafs = (newextents + lcap - 1) / lcap;
+	idxs = ((inode->i_sb->s_blocksize - sizeof(struct ext4_extent_header))
+		/ sizeof(struct ext4_extent_idx));
 
 	/*
-	 * Worse case, we need separate index block(s)
-	 * to link all new leaf blocks
+	 * 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.
 	 */
-	idxs = (leafs + icap - 1) / icap;
-	do {
-		num += idxs;
-		idxs = (idxs + icap - 1) / icap;
-	} while (idxs > rcap);
+	if (ei->i_da_metadata_calc_len &&
+	    ei->i_da_metadata_calc_last_lblock+1 == lblock) {
+		if ((ei->i_da_metadata_calc_len % idxs) == 0)
+			num++;
+		if ((ei->i_da_metadata_calc_len % (idxs*idxs)) == 0)
+			num++;
+		if ((ei->i_da_metadata_calc_len % (idxs*idxs*idxs)) == 0) {
+			num++;
+			ei->i_da_metadata_calc_len = 0;
+		} else
+			ei->i_da_metadata_calc_len++;
+		ei->i_da_metadata_calc_last_lblock++;
+		return num;
+	}
 
-	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
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a26a0b4..cc6e717 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1009,38 +1009,44 @@ qsize_t *ext4_get_reserved_space(struct inode *inode)
 	return &EXT4_I(inode)->i_reserved_quota;
 }
 #endif
+
 /*
  * Calculate the number of metadata blocks need to reserve
- * to allocate @blocks for non extent file based file
+ * to allocate a new block at @lblocks for non extent file based file
  */
-static int ext4_indirect_calc_metadata_amount(struct inode *inode, int blocks)
+static int ext4_indirect_calc_metadata_amount(struct inode *inode,
+					      sector_t lblock)
 {
-	int icap = EXT4_ADDR_PER_BLOCK(inode->i_sb);
-	int ind_blks, dind_blks, tind_blks;
-
-	/* number of new indirect blocks needed */
-	ind_blks = (blocks + icap - 1) / icap;
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	int dind_mask = EXT4_ADDR_PER_BLOCK(inode->i_sb) - 1;
+	int blk_bits;
 
-	dind_blks = (ind_blks + icap - 1) / icap;
+	if (lblock < EXT4_NDIR_BLOCKS)
+		return 0;
 
-	tind_blks = 1;
+	lblock -= EXT4_NDIR_BLOCKS;
 
-	return ind_blks + dind_blks + tind_blks;
+	if (ei->i_da_metadata_calc_len &&
+	    (lblock & dind_mask) == ei->i_da_metadata_calc_last_lblock) {
+		ei->i_da_metadata_calc_len++;
+		return 0;
+	}
+	ei->i_da_metadata_calc_last_lblock = lblock & dind_mask;
+	ei->i_da_metadata_calc_len = 1;
+	blk_bits = roundup_pow_of_two(lblock + 1);
+	return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
 }
 
 /*
  * Calculate the number of metadata blocks need to reserve
- * to allocate given number of blocks
+ * to allocate a block located at @lblock
  */
-static int ext4_calc_metadata_amount(struct inode *inode, int blocks)
+static int ext4_calc_metadata_amount(struct inode *inode, sector_t lblock)
 {
-	if (!blocks)
-		return 0;
-
 	if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
-		return ext4_ext_calc_metadata_amount(inode, blocks);
+		return ext4_ext_calc_metadata_amount(inode, lblock);
 
-	return ext4_indirect_calc_metadata_amount(inode, blocks);
+	return ext4_indirect_calc_metadata_amount(inode, lblock);
 }
 
 /*
@@ -1078,6 +1084,7 @@ static void ext4_da_update_reserve_space(struct inode *inode, int used)
 		 */
 		mdb_free = ei->i_reserved_meta_blocks;
 		ei->i_reserved_meta_blocks = 0;
+		ei->i_da_metadata_calc_len = 0;
 	}
 	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 
@@ -1801,12 +1808,15 @@ static int ext4_journalled_write_end(struct file *file,
 	return ret ? ret : copied;
 }
 
-static int ext4_da_reserve_space(struct inode *inode, int nrblocks)
+/*
+ * Reserve a single block located at lblock
+ */
+static int ext4_da_reserve_space(struct inode *inode, sector_t lblock)
 {
 	int retries = 0;
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	struct ext4_inode_info *ei = EXT4_I(inode);
-	unsigned long md_needed, md_reserved, total = 0;
+	unsigned long md_needed, md_reserved;
 
 	/*
 	 * recalculate the amount of metadata blocks to reserve
@@ -1816,8 +1826,7 @@ static int ext4_da_reserve_space(struct inode *inode, int nrblocks)
 repeat:
 	spin_lock(&ei->i_block_reservation_lock);
 	md_reserved = ei->i_reserved_meta_blocks;
-	md_needed = ext4_calc_metadata_amount(inode, nrblocks);
-	total = md_needed + nrblocks;
+	md_needed = ext4_calc_metadata_amount(inode, lblock);
 	spin_unlock(&ei->i_block_reservation_lock);
 
 	/*
@@ -1825,7 +1834,7 @@ repeat:
 	 * later. Real quota accounting is done at pages writeout
 	 * time.
 	 */
-	if (vfs_dq_reserve_block(inode, total)) {
+	if (vfs_dq_reserve_block(inode, md_needed + 1)) {
 		/* 
 		 * We tend to badly over-estimate the amount of
 		 * metadata blocks which are needed, so if we have
@@ -1837,8 +1846,8 @@ repeat:
 		return -EDQUOT;
 	}
 
-	if (ext4_claim_free_blocks(sbi, total)) {
-		vfs_dq_release_reservation_block(inode, total);
+	if (ext4_claim_free_blocks(sbi, md_needed + 1)) {
+		vfs_dq_release_reservation_block(inode, md_needed + 1);
 		if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
 		retry:
 			if (md_reserved)
@@ -1849,7 +1858,7 @@ repeat:
 		return -ENOSPC;
 	}
 	spin_lock(&ei->i_block_reservation_lock);
-	ei->i_reserved_data_blocks += nrblocks;
+	ei->i_reserved_data_blocks++;
 	ei->i_reserved_meta_blocks += md_needed;
 	spin_unlock(&ei->i_block_reservation_lock);
 
@@ -1890,6 +1899,7 @@ static void ext4_da_release_space(struct inode *inode, int to_free)
 		 */
 		to_free += ei->i_reserved_meta_blocks;
 		ei->i_reserved_meta_blocks = 0;
+		ei->i_da_metadata_calc_len = 0;
 	}
 
 	/* update fs dirty blocks counter */
@@ -2503,7 +2513,7 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 		 * XXX: __block_prepare_write() unmaps passed block,
 		 * is it OK?
 		 */
-		ret = ext4_da_reserve_space(inode, 1);
+		ret = ext4_da_reserve_space(inode, iblock);
 		if (ret)
 			/* not enough space to reserve */
 			return ret;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7cccb35..735c20d 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -702,6 +702,7 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
 	ei->i_reserved_data_blocks = 0;
 	ei->i_reserved_meta_blocks = 0;
 	ei->i_allocated_meta_blocks = 0;
+	ei->i_da_metadata_calc_len = 0;
 	ei->i_delalloc_reserved_flag = 0;
 	spin_lock_init(&(ei->i_block_reservation_lock));
 #ifdef CONFIG_QUOTA
