Re: [Qemu-devel] write_zeroes/trim on the whole disk

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

On 24.09.2016 15:06, Vladimir Sementsov-Ogievskiy wrote:
> On 24.09.2016 00:21, Wouter Verhelst wrote:
>> On Fri, Sep 23, 2016 at 02:00:06PM -0500, Eric Blake wrote:
>>> My preference would be a new flag to the existing commands, with
>>> explicit documentation that 0 offset and 0 length must be used with 
>>> that
>>> flag, when requesting a full-device wipe.
>> Alternatively, what about a flag that says "if you use this flag, the
>> size should be left-shifted by X bits before processing"? That allows
>> you to do TRIM or WRITE_ZEROES on much larger chunks, without being
>> limited to "whole disk" commands. We should probably make it an illegal
>> flag for any command that actually sends data over the wire, though.
>>
>
>
> Note: if disk size is not aligned to X we will have to send request 
> larger than the disk size to clear the whole disk.
>

Also, in this case, which realization of bdrv interface in qemu would be 
most appropriate? Similar flag (in this case X must be defined in some 
very transparent way, as a constant of 64k for example), or flag 
BDRV_REQ_WHOLE_DISK, or separate .bdrv_zero_all and .bdrv_discard_all ?

-- 
Best regards,
Vladimir