> I don't see much difference with zero/punch on dm-thinp. An
> fallocate(FL_PUNCH_HOLE|FL_KEEP_SIZE) doesn't work because it explicitly
> requests hardware zeroing, which I don't have.
> fallocate(FL_ZERO_RANGE|FL_KEEP_SIZE) works, but takes a minute or two
> on my 10G device because it falls back to manual zeroing. There is a
> NO_HIDE_STALE variant of PUNCH_HOLE, but I don't seem to have any
> userspace tools that define NO_HIDE_STALE and it looks like it just
> sends discards anyways. Of course, a 'blkdiscard -o 0 -l 10g <thindev>'
> unmaps nearly the entire device in ~1s, but then we're back to the
> argument of using discard for zeroing. :P
>
I don't think that is a problem if we build the test around thinp and its
well defined behavior on discard. This is what I was getting at:
1. Move dm-thinp setup inside the dm-logwrite helpers, so dm-logwrites
tests cannot be written without dm-thinp by mistake.
2. Use explicit discard in start of replay helper to zap everything before
replay
I'll add to my TODO list.
Thanks,
Amir.
