ext4: ext4_inode_info diet

Generic inode has unused i_private pointer which may be used as cur_aio_dio
storage.

TODO: If cur_aio_dio will be passed as an argument to get_block_t this allow
      to have concurent AIO_DIO requests.

Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -912,8 +912,6 @@ struct ext4_inode_info {
 	struct list_head i_completed_io_list;
 	spinlock_t i_completed_io_lock;
 	atomic_t i_ioend_count;	/* Number of outstanding io_end structs */
-	/* current io_end structure for async DIO write*/
-	ext4_io_end_t *cur_aio_dio;
 	atomic_t i_aiodio_unwritten; /* Nr. of inflight conversions pending */
 
 	spinlock_t i_block_reservation_lock;
@@ -1338,6 +1336,16 @@ static inline void ext4_set_io_unwritten_flag(struct inode *inode,
 	}
 }
 
+static inline ext4_io_end_t *ext4_inode_aio(struct inode *inode)
+{
+	return inode->i_private;
+}
+
+static inline void ext4_inode_aio_set(struct inode *inode, ext4_io_end_t *io)
+{
+	inode->i_private = io;
+}
+
 /*
  * Inode dynamic state flags
  */