[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH 4/4] scsi: add persistent reservation manager us

From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH 4/4] scsi: add persistent reservation manager using qemu-pr-helper
Date: Tue, 19 Sep 2017 15:23:09 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

On 19/09/2017 15:12, Daniel P. Berrange wrote:
> On Tue, Sep 19, 2017 at 02:57:00PM +0200, Paolo Bonzini wrote:
>> On 19/09/2017 14:53, Daniel P. Berrange wrote:
>>>> +    /* Try to reconnect while sending the CDB.  */
>>>> +    for (attempts = 0; attempts < PR_MAX_RECONNECT_ATTEMPTS; attempts++) {
>>> I'm curious why you need to loop here. The helper daemon should be running
>>> already, as you're not spawning it on demand IIUC. So it shoudl either
>>> succeed first time, or fail every time.
>> You're focusing on the usecase where the helper daemon is spawned per-VM
>> by the system libvirtd, which I agree is the most important one.
>> However, the other usecase is the one with a global daemon, access to
>> which is controlled via Unix permissions.  This is not SELinux-friendly,
>> but it is nicer for testing and it is also the only possibility for user
>> libvirtd.
>> In that case, upgrading QEMU on the host could result in a "systemctl
>> restart qemu-pr-helper.service" (or, hopefully unlikely, a crash could
>> result in systemd respawning the daemon).  Reconnect is useful in that case.
> If using systemd socket activation and you restart the daemon, the listening
> socket should be preserved, so you shouldn't need to reconnect - the client
> should get queued until it has started again (likewise on crash).

Oh, that's cool.  I didn't know that.  However, systemd socket
activation is optional, and it's only a handful of lines so I think it's
a bit nicer behavior (chardevs for example have options to reconnect).


reply via email to

[Prev in Thread] Current Thread [Next in Thread]