Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target on convert

[Kevin Wolf]

Am 18.07.2013 um 12:24 hat Paolo Bonzini geschrieben:
> Il 18/07/2013 11:23, Kevin Wolf ha scritto:
> > Am 17.07.2013 um 19:48 hat Peter Lieven geschrieben:
> >>
> >> Am 17.07.2013 um 19:04 schrieb Paolo Bonzini <address@hidden>:
> >>
> >>> Il 17/07/2013 19:02, Peter Lieven ha scritto:
> >>>> For Disks we always use read/write16 so i think we Should also use 
> >>>> writesame16. Or not?
> >>>
> >>> Yes.
> >>>
> >>> Remember you can still use UNMAP if LBPRZ=0.
> >>
> >> I can always use it if writesame is not available, but in this case 
> >> bdi->discard_zeroes must be 0.
> >>
> >> Maybe we should call it discard_writes_zeroes or similar.
> >>
> >> Discard_zeroes is sth that should only indicate if lbprz == 1. At least if 
> >> we refer to the Linux ioctl. We could include both in BDI.
> > 
> > Maybe what we really should do is to define different operations (with
> > an exact behaviour) instead of having one bdrv_discard() and then adding
> > flags everywhere to tell what the operation is doing exactly.
> 
> A BDRV_MAY_UNMAP flag for bdrv_write_zeroes?

Something like that, yes.

Kevin