ext3: Wait for proper transaction commit on fsync

We cannot rely on buffer dirty bits during fsync because pdflush can come
before fsync is called and clear dirty bits without forcing a transaction
commit. What we do is that we track which transaction has last changed
the inode and which transaction last changed allocation and force it to
disk on fsync.

Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

include/linux/ext3_fs_i.h

@@ -137,6 +137,14 @@ struct ext3_inode_info {
 	 * by other means, so we have truncate_mutex.
 	 */
 	struct mutex truncate_mutex;
+
+	/*
+	 * Transactions that contain inode's metadata needed to complete
+	 * fsync and fdatasync, respectively.
+	 */
+	atomic_t i_sync_tid;
+	atomic_t i_datasync_tid;
+
 	struct inode vfs_inode;
 };