Re: [PATCH 1/2] kdump/fadump: fix network interface name when switching from fadump to kdump

[Dave Young]

Hi, Hari

On 09/14/16 at 02:29pm, Hari Bathini wrote:
> Hi Dave,
>
> On Wednesday 14 September 2016 02:13 PM, Dave Young wrote:
> > On 09/14/16 at 02:02pm, Hari Bathini wrote:
> > > Hi Dave,
> > >
> > > On Wednesday 14 September 2016 01:22 PM, Dave Young wrote:
> > > > Hi, Hari
> > > >
> > > > On 09/14/16 at 12:57pm, Hari Bathini wrote:
> > > > > On Monday 12 September 2016 10:18 PM, Hari Bathini wrote:
> > > > > > On Monday 12 September 2016 10:08 PM, Hari Bathini wrote:
> > > > > > > Hi Dave,
> > > > > > > 
> > > > > > > 
> > > > > > > On Monday 12 September 2016 07:35 AM, Dave Young wrote:
> > > > > > > > Hi, Hari
> > > > > > > > 
> > > > > > > > Thanks for sending the patches.
> > > > > > > > 
> > > > > > > > The issue will not happen if we restore default initrd in patch 2/2,
> > > > > > > > right? So patch 1/2 is not necessary?
> > > > > > > Actually, the first reboot after switching over from fadump to kdump
> > > > > > > still holds the interface name with "kdump-" prefix as we haven't
> > > > > > > restored
> > > > > > > the default initrd yet. This patch intents to cover that and also,
> > > > > > > to restore
> > > > > > > the original interface name for subsequent reboots..
> > > > > > >
> > > > >
> > > > > Hi Dave,
> > > > >
> > > > > Another possible case is rebuild may not happen on switching from fadump to
> > > > > kdump,
> > > > > if config files are not changed. I could restore as part of start_dump() but
> > > > > that doesn't
> > > > > sound right to me. Posted v2 with this patch intact. Please review..
> > > >
> > > > I got the problem, do you have any method to know the fadump mode
> > > > changing?  Ideally we should check and rebuild when the mode changes.
> > >
> > > If /sys/kernel/fadump_registered node is not available and default initrd is
> > > built with kdump module, it signifies that we switched from fadump to
> > > kdump. That is after a reboot though where we already have the ifname
> > > with "kdump-" prefix..
> >
> > Hari, if so how about fix it to let check_rebuild to detect the mode
> > change so that we can use patch 2 to restore original initramfs?
>
> Just mentioned the same on a previous mail..

Sorry, I may not understand your points, you are thinking that rebuild
sounds bad without kdump.conf changes? Actually we have added more logic
to rebuild checking not limited to the config file only now.
> > I worry about avoiding multi kdump- prefix cause issues though in real
> > life usually maybe nobody will name a nic as kdump-eth*
>
> The hunk in this patch adds kdump- prefix only if the interface name
> doesn't have it already. If it already has such prefix, we don't have to
> worry about the name as it is not default name.. So, I think it serves
> the purpose you are mentioning?

I see it, but one can rename it to kdump-eth0 in udev, it is a valid name, no?
I know it is not a usual case, but I still feel check_rebuild sounds
better approach.
> Thanks
> Hari
> > > Thanks
> > > Hari
> > > > Thanks
> > > > Dave
> >
> > Thanks
> > Dave

Thanks
Dave