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Date: Thu, 18 Jul 2013 12:24:32 +0200
From: Paolo Bonzini <pbonzini@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: Kevin Wolf <kwolf@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>, Peter Lieven <pl@kamp.de>, qemu-devel <qemu-devel@nongnu.org>, ronnie sahlberg <ronniesahlberg@gmail.com>

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 <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.

A BDRV_MAY_UNMAP flag for bdrv_write_zeroes?

Paolo