Change list_add_tail to list_add. It gives advantages to ldiskfs
in tgt_cb_last_committed. In the beginning of list will be placed
thandles with the highest transaction numbers. So at the first
iterations we will have the highest transno. It will save from
extra call of ptlrpc_commit_replies.

Index: linux-3.10.0-229.1.2.fc21.x86_64/fs/ext4/ext4_jbd2.c
===================================================================
--- linux-3.10.0-229.1.2.fc21.x86_64.orig/fs/ext4/ext4_jbd2.h
+++ linux-3.10.0-229.1.2.fc21.x86_64/fs/ext4/ext4_jbd2.h
@@ -3644,7 +3644,7 @@ void ext4_truncate(struct inode *inode)
 	/* Add the jce to transaction's private list */
 	jce->jce_func = func;
 	spin_lock(&sbi->s_md_lock);
-	list_add_tail(&jce->jce_list, &handle->h_transaction->t_private_list);
+	list_add(&jce->jce_list, &handle->h_transaction->t_private_list);
	spin_unlock(&sbi->s_md_lock);
 }