krpc: unbootable ZFS-on-root after major upgrade to 11.2

[Glen Barber]

On Mon, Oct 22, 2018 at 09:09:14PM +0700, Eugene Grosbein wrote:
> 22.10.2018 21:03, Glen Barber wrote:
> 
> t's strange that this is a 10.x vs 11.x issue.
> >>> I see that zfs has the krpc dependency since r193128.
> >>> And the call to xdrmem_create is there since r168404.
> >>
> >> You are right. I was mis-informed and have not verified enough a report from local user.
> >>
> >> Glen, maybe that errata record should be deleted. The problem is real but it is long-standing
> >> and present in 10.x too.
> >>
> > 
> > Could you elaborate more on the failure case you originally reported
> > first?  If the problem is real, my feeling is that the errata entry
> > should stay, just worded differently to reflect the failure case here.
> 
> zfs.ko depends on krpc.ko. The KRPC code in compiled in GENERIC kernel as dependency
> of NFS client/server code. The problem arises if all of these are true:
> 
> 1) a system uses custom kernel with NFS options removed;
> 2) there is no krpc.ko available due to MODULES_OVERRIDE excluding it;
> 3) the system boots off ZFS pool.
> 
> In such case, loader cannot resolve dependency and fails to load zfs.ko
> and kernel fails to mount root breaking boot sequence.
> 
> 

So, if I understand correctly (and please correct me if I am wrong), the
majority of the text in the errata note is correct, however needs to be
tweaked to remove "upgrading from 10.x...".  Is this generally correct?

Glen

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