diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index 579659b..cacfc11 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -4293,6 +4293,116 @@
 	return status;
 }
 
+/*
+ * Allcate and add clusters into the extent b-tree.
+ * The new clusters(clusters_to_add) will be inserted at logical_offset.
+ * The extent b-tree's root is root_el and it should be in root_bh, and
+ * it is not limited to the file storage. Any extent tree can use this
+ * function if it implements the proper ocfs2_extent_tree.
+ */
+int ocfs2_add_clusters_in_btree(struct ocfs2_super *osb,
+				struct inode *inode,
+				u32 *logical_offset,
+				u32 clusters_to_add,
+				int mark_unwritten,
+				struct buffer_head *root_bh,
+				struct ocfs2_extent_list *root_el,
+				handle_t *handle,
+				struct ocfs2_alloc_context *data_ac,
+				struct ocfs2_alloc_context *meta_ac,
+				enum ocfs2_alloc_restarted *reason_ret,
+				enum ocfs2_extent_tree_type type)
+{
+	int status = 0;
+	int free_extents;
+	enum ocfs2_alloc_restarted reason = RESTART_NONE;
+	u32 bit_off, num_bits;
+	u64 block;
+	u8 flags = 0;
+
+	BUG_ON(!clusters_to_add);
+
+	if (mark_unwritten)
+		flags = OCFS2_EXT_UNWRITTEN;
+
+	free_extents = ocfs2_num_free_extents(osb, inode, root_bh, type);
+	if (free_extents < 0) {
+		status = free_extents;
+		mlog_errno(status);
+		goto leave;
+	}
+
+	/* there are two cases which could cause us to EAGAIN in the
+	 * we-need-more-metadata case:
+	 * 1) we haven't reserved *any*
+	 * 2) we are so fragmented, we've needed to add metadata too
+	 *    many times. */
+	if (!free_extents && !meta_ac) {
+		mlog(0, "we haven't reserved any metadata!\n");
+		status = -EAGAIN;
+		reason = RESTART_META;
+		goto leave;
+	} else if ((!free_extents)
+		   && (ocfs2_alloc_context_bits_left(meta_ac)
+		       < ocfs2_extend_meta_needed(root_el))) {
+		mlog(0, "filesystem is really fragmented...\n");
+		status = -EAGAIN;
+		reason = RESTART_META;
+		goto leave;
+	}
+
+	status = __ocfs2_claim_clusters(osb, handle, data_ac, 1,
+					clusters_to_add, &bit_off, &num_bits);
+	if (status < 0) {
+		if (status != -ENOSPC)
+			mlog_errno(status);
+		goto leave;
+	}
+
+	BUG_ON(num_bits > clusters_to_add);
+
+	/* reserve our write early -- insert_extent may update the inode */
+	status = ocfs2_journal_access(handle, inode, root_bh,
+				      OCFS2_JOURNAL_ACCESS_WRITE);
+	if (status < 0) {
+		mlog_errno(status);
+		goto leave;
+	}
+
+	block = ocfs2_clusters_to_blocks(osb->sb, bit_off);
+	mlog(0, "Allocating %u clusters at block %u for inode %llu\n",
+	     num_bits, bit_off, (unsigned long long)OCFS2_I(inode)->ip_blkno);
+	status = ocfs2_insert_extent(osb, handle, inode, root_bh,
+				     *logical_offset, block, num_bits,
+				     flags, meta_ac, type);
+	if (status < 0) {
+		mlog_errno(status);
+		goto leave;
+	}
+
+	status = ocfs2_journal_dirty(handle, root_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto leave;
+	}
+
+	clusters_to_add -= num_bits;
+	*logical_offset += num_bits;
+
+	if (clusters_to_add) {
+		mlog(0, "need to alloc once more, wanted = %u\n",
+		     clusters_to_add);
+		status = -EAGAIN;
+		reason = RESTART_TRANS;
+	}
+
+leave:
+	mlog_exit(status);
+	if (reason_ret)
+		*reason_ret = reason;
+	return status;
+}
+
 static void ocfs2_make_right_split_rec(struct super_block *sb,
 				       struct ocfs2_extent_rec *split_rec,
 				       u32 cpos,
diff --git a/fs/ocfs2/alloc.h b/fs/ocfs2/alloc.h
index 473c8bc..5e090c5 100644
--- a/fs/ocfs2/alloc.h
+++ b/fs/ocfs2/alloc.h
@@ -41,6 +41,23 @@
 			u8 flags,
 			struct ocfs2_alloc_context *meta_ac,
 			enum ocfs2_extent_tree_type et_type);
+enum ocfs2_alloc_restarted {
+	RESTART_NONE = 0,
+	RESTART_TRANS,
+	RESTART_META
+};
+int ocfs2_add_clusters_in_btree(struct ocfs2_super *osb,
+				struct inode *inode,
+				u32 *logical_offset,
+				u32 clusters_to_add,
+				int mark_unwritten,
+				struct buffer_head *root_bh,
+				struct ocfs2_extent_list *root_el,
+				handle_t *handle,
+				struct ocfs2_alloc_context *data_ac,
+				struct ocfs2_alloc_context *meta_ac,
+				enum ocfs2_alloc_restarted *reason_ret,
+				enum ocfs2_extent_tree_type type);
 struct ocfs2_cached_dealloc_ctxt;
 int ocfs2_mark_extent_written(struct inode *inode, struct buffer_head *root_bh,
 			      handle_t *handle, u32 cpos, u32 len, u32 phys,
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 44ea5eb..e7acd28 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1255,10 +1255,10 @@
 		 * any additional semaphores or cluster locks.
 		 */
 		tmp_pos = cpos;
-		ret = ocfs2_do_extend_allocation(OCFS2_SB(inode->i_sb), inode,
-						 &tmp_pos, 1, 0, wc->w_di_bh,
-						 wc->w_handle, data_ac,
-						 meta_ac, NULL);
+		ret = ocfs2_add_inode_data(OCFS2_SB(inode->i_sb), inode,
+					   &tmp_pos, 1, 0, wc->w_di_bh,
+					   wc->w_handle, data_ac,
+					   meta_ac, NULL);
 		/*
 		 * This shouldn't happen because we must have already
 		 * calculated the correct meta data allocation required. The
diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
index ba0fb9e..d17c34b 100644
--- a/fs/ocfs2/dir.c
+++ b/fs/ocfs2/dir.c
@@ -1383,9 +1383,9 @@
 	if (extend) {
 		u32 offset = OCFS2_I(dir)->ip_clusters;
 
-		status = ocfs2_do_extend_allocation(OCFS2_SB(sb), dir, &offset,
-						    1, 0, parent_fe_bh, handle,
-						    data_ac, meta_ac, NULL);
+		status = ocfs2_add_inode_data(OCFS2_SB(sb), dir, &offset,
+					      1, 0, parent_fe_bh, handle,
+					      data_ac, meta_ac, NULL);
 		BUG_ON(status == -EAGAIN);
 		if (status < 0) {
 			mlog_errno(status);
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index f567cc5..7bb4fde 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -488,7 +488,7 @@
 }
 
 /*
- * extend allocation only here.
+ * extend file allocation only here.
  * we'll update all the disk stuff, and oip->alloc_size
  *
  * expect stuff to be locked, a transaction started and enough data /
@@ -497,107 +497,25 @@
  * Will return -EAGAIN, and a reason if a restart is needed.
  * If passed in, *reason will always be set, even in error.
  */
-int ocfs2_do_extend_allocation(struct ocfs2_super *osb,
-			       struct inode *inode,
-			       u32 *logical_offset,
-			       u32 clusters_to_add,
-			       int mark_unwritten,
-			       struct buffer_head *fe_bh,
-			       handle_t *handle,
-			       struct ocfs2_alloc_context *data_ac,
-			       struct ocfs2_alloc_context *meta_ac,
-			       enum ocfs2_alloc_restarted *reason_ret)
+int ocfs2_add_inode_data(struct ocfs2_super *osb,
+			 struct inode *inode,
+			 u32 *logical_offset,
+			 u32 clusters_to_add,
+			 int mark_unwritten,
+			 struct buffer_head *fe_bh,
+			 handle_t *handle,
+			 struct ocfs2_alloc_context *data_ac,
+			 struct ocfs2_alloc_context *meta_ac,
+			 enum ocfs2_alloc_restarted *reason_ret)
 {
-	int status = 0;
-	int free_extents;
 	struct ocfs2_dinode *fe = (struct ocfs2_dinode *) fe_bh->b_data;
-	enum ocfs2_alloc_restarted reason = RESTART_NONE;
-	u32 bit_off, num_bits;
-	u64 block;
-	u8 flags = 0;
+	struct ocfs2_extent_list *el = &fe->id2.i_list;
 
-	BUG_ON(!clusters_to_add);
-
-	if (mark_unwritten)
-		flags = OCFS2_EXT_UNWRITTEN;
-
-	free_extents = ocfs2_num_free_extents(osb, inode, fe_bh,
-					      OCFS2_DINODE_EXTENT);
-	if (free_extents < 0) {
-		status = free_extents;
-		mlog_errno(status);
-		goto leave;
-	}
-
-	/* there are two cases which could cause us to EAGAIN in the
-	 * we-need-more-metadata case:
-	 * 1) we haven't reserved *any*
-	 * 2) we are so fragmented, we've needed to add metadata too
-	 *    many times. */
-	if (!free_extents && !meta_ac) {
-		mlog(0, "we haven't reserved any metadata!\n");
-		status = -EAGAIN;
-		reason = RESTART_META;
-		goto leave;
-	} else if ((!free_extents)
-		   && (ocfs2_alloc_context_bits_left(meta_ac)
-		       < ocfs2_extend_meta_needed(&fe->id2.i_list))) {
-		mlog(0, "filesystem is really fragmented...\n");
-		status = -EAGAIN;
-		reason = RESTART_META;
-		goto leave;
-	}
-
-	status = __ocfs2_claim_clusters(osb, handle, data_ac, 1,
-					clusters_to_add, &bit_off, &num_bits);
-	if (status < 0) {
-		if (status != -ENOSPC)
-			mlog_errno(status);
-		goto leave;
-	}
-
-	BUG_ON(num_bits > clusters_to_add);
-
-	/* reserve our write early -- insert_extent may update the inode */
-	status = ocfs2_journal_access(handle, inode, fe_bh,
-				      OCFS2_JOURNAL_ACCESS_WRITE);
-	if (status < 0) {
-		mlog_errno(status);
-		goto leave;
-	}
-
-	block = ocfs2_clusters_to_blocks(osb->sb, bit_off);
-	mlog(0, "Allocating %u clusters at block %u for inode %llu\n",
-	     num_bits, bit_off, (unsigned long long)OCFS2_I(inode)->ip_blkno);
-	status = ocfs2_insert_extent(osb, handle, inode, fe_bh,
-				     *logical_offset, block, num_bits,
-				     flags, meta_ac, OCFS2_DINODE_EXTENT);
-	if (status < 0) {
-		mlog_errno(status);
-		goto leave;
-	}
-
-	status = ocfs2_journal_dirty(handle, fe_bh);
-	if (status < 0) {
-		mlog_errno(status);
-		goto leave;
-	}
-
-	clusters_to_add -= num_bits;
-	*logical_offset += num_bits;
-
-	if (clusters_to_add) {
-		mlog(0, "need to alloc once more, clusters = %u, wanted = "
-		     "%u\n", fe->i_clusters, clusters_to_add);
-		status = -EAGAIN;
-		reason = RESTART_TRANS;
-	}
-
-leave:
-	mlog_exit(status);
-	if (reason_ret)
-		*reason_ret = reason;
-	return status;
+	return ocfs2_add_clusters_in_btree(osb, inode, logical_offset,
+					   clusters_to_add, mark_unwritten,
+					   fe_bh, el, handle,
+					   data_ac, meta_ac, reason_ret,
+					   OCFS2_DINODE_EXTENT);
 }
 
 static int __ocfs2_extend_allocation(struct inode *inode, u32 logical_start,
@@ -676,16 +594,16 @@
 
 	prev_clusters = OCFS2_I(inode)->ip_clusters;
 
-	status = ocfs2_do_extend_allocation(osb,
-					    inode,
-					    &logical_start,
-					    clusters_to_add,
-					    mark_unwritten,
-					    bh,
-					    handle,
-					    data_ac,
-					    meta_ac,
-					    &why);
+	status = ocfs2_add_inode_data(osb,
+				      inode,
+				      &logical_start,
+				      clusters_to_add,
+				      mark_unwritten,
+				      bh,
+				      handle,
+				      data_ac,
+				      meta_ac,
+				      &why);
 	if ((status < 0) && (status != -EAGAIN)) {
 		if (status != -ENOSPC)
 			mlog_errno(status);
diff --git a/fs/ocfs2/file.h b/fs/ocfs2/file.h
index 18e5c80..e92382c 100644
--- a/fs/ocfs2/file.h
+++ b/fs/ocfs2/file.h
@@ -33,6 +33,7 @@
 extern const struct inode_operations ocfs2_file_iops;
 extern const struct inode_operations ocfs2_special_file_iops;
 struct ocfs2_alloc_context;
+enum ocfs2_alloc_restarted;
 
 struct ocfs2_file_private {
 	struct file		*fp_file;
@@ -40,21 +41,16 @@
 	struct ocfs2_lock_res	fp_flock;
 };
 
-enum ocfs2_alloc_restarted {
-	RESTART_NONE = 0,
-	RESTART_TRANS,
-	RESTART_META
-};
-int ocfs2_do_extend_allocation(struct ocfs2_super *osb,
-			       struct inode *inode,
-			       u32 *logical_offset,
-			       u32 clusters_to_add,
-			       int mark_unwritten,
-			       struct buffer_head *fe_bh,
-			       handle_t *handle,
-			       struct ocfs2_alloc_context *data_ac,
-			       struct ocfs2_alloc_context *meta_ac,
-			       enum ocfs2_alloc_restarted *reason_ret);
+int ocfs2_add_inode_data(struct ocfs2_super *osb,
+			 struct inode *inode,
+			 u32 *logical_offset,
+			 u32 clusters_to_add,
+			 int mark_unwritten,
+			 struct buffer_head *fe_bh,
+			 handle_t *handle,
+			 struct ocfs2_alloc_context *data_ac,
+			 struct ocfs2_alloc_context *meta_ac,
+			 enum ocfs2_alloc_restarted *reason_ret);
 int ocfs2_extend_no_holes(struct inode *inode, u64 new_i_size,
 			  u64 zero_to);
 int ocfs2_setattr(struct dentry *dentry, struct iattr *attr);
diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index d5d808f..2cd6f50 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -1598,10 +1598,10 @@
 		u32 offset = 0;
 
 		inode->i_op = &ocfs2_symlink_inode_operations;
-		status = ocfs2_do_extend_allocation(osb, inode, &offset, 1, 0,
-						    new_fe_bh,
-						    handle, data_ac, NULL,
-						    NULL);
+		status = ocfs2_add_inode_data(osb, inode, &offset, 1, 0,
+					      new_fe_bh,
+					      handle, data_ac, NULL,
+					      NULL);
 		if (status < 0) {
 			if (status != -ENOSPC && status != -EINTR) {
 				mlog(ML_ERROR,