Hi,
On 21.10.22 16:28, Kui Liu wrote:
-----Original Message-----
From: Alexander Atanasov <alexander.atana...@virtuozzo.com>
Date: Friday, 21 October 2022 at 7:35 PM
To: Kui Liu <kui....@acronis.com>, Konstantin Khorenko <khore...@virtuozzo.com>,
Alexey Kuznetsov <kuz...@acronis.com>
Cc: Devel <devel@openvz.org>
Subject: Re: [Devel] [PATCH RH9] dm-ploop: port the standby mode feature.
On 21.10.22 14:28, Kui Liu wrote:
> > > Ok - for the user space there are two options:
> > > 1. add an argument to enable at creation time
> > > 2. command standby_enable /if using the enable it
is possible to
> > > implement a disable command too/.
> > >
> > > I prefer the second approach but let's hear other
opinions too.
> > > And yes we can possibly do both but is there a use
case ?
> > >
> > > [LIU]: Since the static key is a global option, I also
think the second approach is better.
> > > In case of nodes with vStorage + ploop + iSCSI setup, we
just need to enable the static
> > > key early in system init or iSCSI service init. I don't
think it is necessary to implement both.
> >
> > You are right. It will need at least one ploop device
created to issue a
> > device mapper command to enable standby. Would a module
parameter work?
> >
> > [LIU] Yes, I think it is better to make the static key a module
parameter.
>
> This rised a question - how and who will pass the module parameter
when
> required ? How we will handle the existin users ? What do you think
?
>
> [LIU]: Like add a conf file ploop.conf in /etc/modprobe.d or
lib/modeprobe.d? This conf file can be shipped with the release image, or
installed later. Are you referring to VZ7 as existing users? I saw you also made
the changes to VZ7, but I'm not sure whether it is necessary to backport these
changes to VZ7.
Yes, VZ7 users - there are issues related to it so trying to fix them.
the modprobe.d would do but do you have a package that can install the
conf tied to the iSCSI target, so it gets installed only if the iSCSI is
used ?
[LIU]: Yes, we do build the our own SCST package, so we can install the conf
from there.
After discussion turns out module_param is not an option - package is
always installed so it will enable the key always which is not what we want.
To solve this we can
struct static_key ploop_standby_check = STATIC_KEY_INIT_FALSE;
+EXPORT_SYMBOL(ploop_standby_check)
and the module can enable it at use or init time.
static int scst_vstor_pr_init(struct scst_device *dev, const char
*cl_dev_id)
looks like the place to enable the static key and set the _en flag on
the queue.
_en flag is a MUST static key is a SHOULD - where do you think is the
best place to implement them in the scst code?
--
Regards,
Alexander Atanasov
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