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Date: Thu, 18 Jul 2013 11:23:16 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 4/4] qemu-img: conditionally discard target
	on convert
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To: Peter Lieven <pl@kamp.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, ronnie sahlberg <ronniesahlberg@gmail.com>

Am 17.07.2013 um 19:48 hat Peter Lieven geschrieben:
> 
> Am 17.07.2013 um 19:04 schrieb Paolo Bonzini <pbonzini@redhat.com>:
> 
> > 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.

Kevin