Re: [Qemu-devel] [PATCHv2 07/11] iscsi: let bdrv_create conditionally zero out the device

[Peter Lieven]

Am 02.07.2013 um 13:04 schrieb Paolo Bonzini <address@hidden>:

> Il 02/07/2013 12:56, Peter Lieven ha scritto:
>> 
>> Am 02.07.2013 um 12:49 schrieb Paolo Bonzini <address@hidden>:
>> 
>>> Il 02/07/2013 12:36, Peter Lieven ha scritto:
>>>>>>> Perhaps we can have a new "discard_zeroes" field in bdrv_get_info, and
>>>>>>> the unmap functionality can be moved up to qemu-img convert?
>>>>>> 
>>>>>> Is there any other storage protocol out there that could benefit from it?
>>>>> 
>>>>> Definitely LVM.  Perhaps in the future gluster too, though right now it
>>>>> only supports discard on files, not block devices.
>>>> 
>>>> Is discards on LVM sth that is already implemented in qemu?
>>> 
>>> Yes, it supports BLKDISCARD (see handle_aiocb_discard in
>>> block/raw-posix.c).  Of course there is no way to query the host
>>> discard_zeroes setting yet.
>> 
>> No way in qemu or no way at all?
> 
> No way in QEMU.  Linux has the BLKDISCARDZEROES ioctl, it takes an int*
> as the third argument and puts 0/1 in it.

okay, thanks for the pointer.

if you all don't mind I would split up my series and first send a v3 which adds 
the unproblematic stuff and
leave 

iscsi: let bdrv_create conditionally zero out the device
block-migration: efficiently encode zero blocks

out. both seem to need more time and cycles to follow the better approaches.

Peter