On Mon, Feb 27, 2017 at 03:13:35PM -0500, Brian Foster wrote: > After playing around a bit, I don't think using i_size is the right > approach either. It just exacerbates the original problem on buffered > writes into sparse files. We can end up leaving around however many > delalloc blocks we've allocated. > > I think we need a way to differentiate preexisting (previously written) > delalloc blocks from those allocated and unused by the current write. We > might be able to do that by looking at the pagecache, but I think that > means looking at the buffer state to make sure we handle sub-page block > sizes correctly. I.e., make *_iomap_end_delalloc() punch out all > delalloc blocks in the non-written range that are either not page backed > or not dirty+delalloc buffer backed. Hm? That sounds ugly, but right off my mind I see no other way. I'll need to take a look at what the old pre-iomap code did there, as I think none of these issues happened there.
