On Thu, Aug 27, 2020 at 11:57:03AM -0400, Josef Bacik wrote: > This sort of brings up a good point, the whole point of DISCARD support in > log-writes was to expose problems where we may have been discarding real > data we cared about, hence adding the forced zero'ing stuff for devices that > didn't support discard. But that made the incorrect assumption that a drive > with actual discard support would actually return 0's for discarded data. > That assumption was based on hardware that did actually do that, but now we > live in the brave new world of significantly shittier drives. Does dm-thinp > reliably unmap the ranges we discard, and thus give us this zero'ing > behavior? Because we might as well just use that for everything so > log-writes doesn't have to resort to pwrite()'ing zeros everywhere. Thanks, We have a write zeroes operation in the block layer. For some devices this is as efficient as discard, and that should (I think) dm.
