Re: [PATCH 0/2] arm64/hotplug: Process MEM_OFFLINE and MEM_CANCEL_OFFLINE events

[David Hildenbrand]

On 15.04.20 08:39, Anshuman Khandual wrote:
> This series improves arm64 memory event notifier (hot remove) robustness by
> enabling it to detect potential problems (if any) in the future. But first
> it enumerates memory isolation failure reasons that can be sent across a
> notifier. This series does not go beyond arm64 to explore if these failure
> reason codes could be used in other existing registered memory notifiers.
> Please do let me know if there is any other potential use cases, will be
> happy to incorporate next time around. Also should we add similar failure
> reasons for online_pages() as well ?
> 
> This series has been tested on arm64, boot tested on x86 and build tested
> on multiple other platforms.
> 

I'm sorry, but I have to nack this series. Why?

1. A hotplug notifier should not have to bother why offlining failed. He
received a MEM_GOING_OFFLINE, followed by a MEM_CANCEL_OFFLINE. That's
all he really has to know. Undo what you've done, end of story.

2. Patch 2 just introduces dead code that should never happen unless
something is horribly broken in the core (memory offlined although
nacked from notifier). And, it (for *whatever reason*) thinks it's okay
to bail out if another notifier canceled offlining hotplugged memory.

I fail to see the benefit for core changes and

 4 files changed, 99 insertions(+), 13 deletions(-)

-- 
Thanks,

David / dhildenb