Am 04.07.2013 um 14:37 schrieb Paolo Bonzini <pbonz...@redhat.com>: > Il 03/07/2013 23:23, Peter Lieven ha scritto: >> BDC is not used. I had an implementation that sent multiple descriptors out, >> but >> at least for my storage the maximum unmap counts not for each descriptors, >> but for all >> together. So in this case we do not need the field at all. I forgot to >> remove it. >> >> discard and write_zeroes will both only send one request up to max_unmap in >> size. >> >> apropos write_zeroes: do you know if UNMAP is guaranteed to unmap data if >> lbprz == 1? > > Yes. On the other hand note that WRITE_SAME should be guaranteed _not_ > to unmap if lbprz == 0 and you do WRITE_SAME with UNMAP and a zero > payload, but I suspect there may be buggy targets here. > >> I have read in the specs something that the target might unmap the blocks or >> not touch them at all. >> Maybe you have more information. > > That's even true of UNMAP itself, actually. :) > > The storage can always "upgrade" a block from unmapped to anchored and > from anchored to allocated, so UNMAP can be a no-op and still comply > with the standard.
My concern was, if I UNMAP a block and lbprz == 1 is it guaranteed that it reads as zero afterwards? Regardless if the target decides to "upgrade" the block or do not unmap the block? Peter
