[dm-devel] Possible data corruption with dm-thin

[Edward Thornber]

Hi Dennis,

On Tue, Jun 21, 2016 at 03:56:26PM +0800, Dennis Yang wrote:
> So my question is, does dm-thin have any mechanism to eliminate the race
> when
> discarded block is reused right away by another device?

I'll try and recreate your scenario.  The transaction-manager will not
reallocate a block that's been freed within a transaction so that we
can always rollback.  So as long as there hasn't been a commit,
reallocation shouldn't be possible.  This is what normally guards
allocation, but in your case I think you may be onto something and we
may have to hold onto the data cell until the passdown discards are
complete.

- Joe