On 25/03/2020 11:01, hch@infradead.org wrote:

I thought of recording the location in ->iomap_end (and in fact
had a prototype for that), but that is not going to work for AIO of
course.  So yes, we'll need some way to have per-extent completion
callbacks.

OK let's postpone iomap then and handle zone-append directly in zonefs 
for now.