Re: [pve-devel] [PATCH qemu-server 01/13] blockdev: cmdline: add blockdev syntax support - DERUMIER, Alexandre via pve-devel

From: "DERUMIER, Alexandre via pve-devel" <pve-devel@lists.proxmox.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>,
	"f.ebner@proxmox.com" <f.ebner@proxmox.com>
Cc: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
Subject: Re: [pve-devel] [PATCH qemu-server 01/13] blockdev: cmdline: add blockdev syntax support
Date: Thu, 5 Jun 2025 14:39:48 +0000	[thread overview]
Message-ID: <mailman.267.1749134399.395.pve-devel@lists.proxmox.com> (raw)
In-Reply-To: <3ae9921d-cc0a-460b-a560-b5edd97c1556@proxmox.com>

[-- Attachment #1: Type: message/rfc822, Size: 17299 bytes --]

From: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>, "f.ebner@proxmox.com" <f.ebner@proxmox.com>
Subject: Re: [pve-devel] [PATCH qemu-server 01/13] blockdev: cmdline: add blockdev syntax support
Date: Thu, 5 Jun 2025 14:39:48 +0000
Message-ID: <ee4940c99e9866910405b492dad15c68718c49ea.camel@groupe-cyllene.com>

Am 03.06.25 um 09:55 schrieb Alexandre Derumier via pve-devel:
> +sub encode_nodename {
> +    my ($type, $volid, $snap) = @_;
> +
> +    my $nodename = "$volid";
> +    $nodename .= "-$snap" if $snap;

This will lead to clashes in some cases:
>>1. Currently, we allow attaching the same volume multiple times to a
>>single guest.
do you mean, manually with editing the vm configuration ?  What is the
usecase ? (I mean, without breaking the fs because the drive could be
mounted twice )
(the vm will not start if node-name is duplicated, so it's look more
secure now ^_^)

>>2. You can end up with the same name for
>>volname = vm-1234-disk-0-foo
>>and for
>>volname = vm-1234-disk-0, snap = foo
>>
>>The latter can be rather easily fixed by just using a character we
>>don't
>>usually support for volume names, but not the former.
we could also generate the full path= , and encode it

>> So I'd like to do
>>the switch to -blockdev without support for "looking up which node a
>>certain volume is" at first. 
yes, if you find a way to do it , could be better !

>>In general, I feel like mixing the switch
>>to -blockdev with your larger series is too much at once.
>>We should
>>first get the switch to -blockdev completely and cleanly sorted out,
>>then we can add your external qcow2 support on top.

yes sure. (the qcow2 snap are only the last 2 patches anyway,  and they
still are a lot of work on the backup side, but I really don't known
how the specific proxmox patches are working , so help is welcome ;)

>>I think we can even rely on auto-generated-by-QEMU node names at
>>first.

The main blocking problem is that auto-generated #block name are not
working with some block action. (if I remember, the drive-reopen wasn't
working correctly, so this was a blocker for snapshots).
I need to retest because in early patches, I was reopening the file
node, and now the format-node, so maybe the behaviour is different now

They are also different behaviour is node-name are defined or notto the
command-line on blockdev-remove.  (for example, sometime you remove the
top-node, the format+file node can be autoremove or not, also the
backing chain)

I really don't known if it's qemu bug or not. (I don't have digged the
qemu code)

>>We can later switch to a variant where node names encode additional
>>information. Or we could also think about patching QEMU to better fit
>>the need for the "looking up which node a certain volume is" feature.
>>But I don't think figuring this out should block us right now for the
>>switch to "-blockdev".

you are better than me for this, my C skill is pretty poor ^_^

>>I'll try to work out a series that focuses just on the switch to
>>"-blockdev" based on your patches during the next week or so. Maybe
>>not
>>much else needs to be changed :) The work is certainly greatly
>>appreciated!

Great! Tell me if it needed testing. (my patches should cover all basic
actions excluding backup)

I'm currently working to add tests for all live action
(hotplug/unplug,cdeject,mirror,snap,...but until it's done, I can help
with manually testing.

I'll be on holiday from arund 15th July (for 3 weeks),but until that
I'm also full-time free to work on it and help.

Alexandre

[-- Attachment #2: Type: text/plain, Size: 160 bytes --]

_______________________________________________
pve-devel mailing list
pve-devel@lists.proxmox.com
https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel