Each caller of ext4_ext_dirty must hold i_data_sem,
The only exception is migration code, let's make it convenient.
Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NJan Kara <jack@suse.cz>