[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH 3/3] nbd: Add 'qemu-nbd -A' to expose allocation depth
From: |
Richard W.M. Jones |
Subject: |
Re: [PATCH 3/3] nbd: Add 'qemu-nbd -A' to expose allocation depth |
Date: |
Sat, 26 Sep 2020 08:34:57 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, Sep 25, 2020 at 03:32:49PM -0500, Eric Blake wrote:
> Allow the server to expose an additional metacontext to be requested
> by savvy clients. qemu-nbd adds a new option -A to expose the
> qemu:allocation-depth metacontext through NBD_CMD_BLOCK_STATUS; this
> can also be set via QMP when using nbd-server-add.
>
> qemu as client can be hacked into viewing this new context by using
> the now-misnamed x-dirty-bitmap option when creating an NBD blockdev;
> although it is worth noting the decoding of how such context
> information will appear in 'qemu-img map --output=json':
>
> NBD_STATE_DEPTH_UNALLOC => "zero":false, "data":true
> NBD_STATE_DEPTH_LOCAL => "zero":false, "data":false
> NBD_STATE_DEPTH_BACKING => "zero":true, "data":true
>
> libnbd as client is probably a nicer way to get at the information
> without having to decipher such hacks in qemu as client. ;)
I've been meaning to add extents information to nbdinfo, or
perhaps a new tool ("nbdmap").
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html