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


From: Vladimir Sementsov-Ogievskiy
Subject: Re: [Qemu-devel] write_zeroes/trim on the whole disk
Date: Sat, 24 Sep 2016 16:42:04 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0

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.

which is not beautiful.. And splitting the request into two: (disk_size / X * X) and (disk_size % X) is not beautiful too. May be flag, that says 'whole disk request' is more appropriate? Nothing prevents adding then flag about X-shift.


--
Best regards,
Vladimir




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