On Tue, Apr 21, 2020 at 06:29:10PM +0200, Jan Kara wrote: > Well, there are two problems with this - firstly, ocfs2 is also using jbd2 > and it knows nothing about iomap. So that would have to be implemented. > Secondly, you have to somehow pass iomap ops to jbd2 so it all boils down > to passing some callback to jbd2 during journal init to map blocks anyway > as Dave said. And then it is upto filesystem to do the mapping - usually > directly using its internal block mapping function - so no need for iomap > AFAICT. You'll need to describe the mapping some how. So why not reuse an existing mechanism instead of creating a new ad-hoc one?