> Am 13.11.2013 um 15:39 schrieb Paolo Bonzini <pbonz...@redhat.com>: > > Il 13/11/2013 15:14, Peter Lieven ha scritto: >>>>>> does BLKDISCARDZEROES ioctl guarantee that a device is >>>>>> zero initialized or does it just guarantee that a discard may not >>>>>> fail and that it reads as zeroes afterwards? >>>> >>>> Only the latter. ".bdrv_has_zero_init" is only present in the bdrv_file >>>> BlockDriver. >> Then bdi->unallocated_blocks_are_zero must stay 0. .bdrv_has_zero_init's >> semantic is to reflect the zero status of all blocks of the device right >> after bdrv_create >> independently of their allocation status. bdi->unallocated_blocks_are_zero >> reflects the zero status of every unallocated block regardless if it was >> unallocated right from the beginning or became unallocated through a discard. > > What we have is: > > * bdi->unallocated_blocks_are_zero returns true > > * bdrv_create doesn't ensure that every block starts unallocated > > * hence bdrv_has_zero_init returns false > > Blocks that (for any reason) are unallocated after bdrv_create *will* be > zero if BLKDISCARDZEROES returns true.
Ok, then i misunderstood your comment. If BLKDISCARDZEROES means lbprz == 1 SCSI speaking then you are right. Peter > > Paolo
