Re: [PATCH 2/2] mm/memory_hotplug: activate node before adding new memory blocks

[Hannes Reinecke <hare@suse.de>]

On 7/2/25 08:36, David Hildenbrand wrote:
> On 02.07.25 08:25, Donet Tom wrote:
>> Hi Hannes Reinecke
>>
>> On 7/1/25 5:11 PM, Hannes Reinecke wrote:
>>> The sysfs attributes for memory blocks require the node ID to be
>>> set and initialized, so move the node activation before adding
>>> new memory blocks. This also has the nice side effect that the
>>> BUG_ON() can be converted into a WARN_ON() as we now can handle
>>> registration errors.
>>
>> Since this fixes the issue, should we consider adding a Fixes: tag?
> 
> Yeah (I mentioned this to patch #1 only). And we should probably CC stable.
> 
> I would assume the issue is fairly old.
> 
And indeed, as old as to be basically meaningless.
The most likely candidate I've found is
b9ff036082cd ("mm/memory_hotplug.c: make add_memory_resource use 
__try_online_node")
(Sorry, Oscar, for picking on you :-)
Before that the history got obscured by later changes.
Problem is that we have two different issues here; the one
is the mis-order of uevents vs sysfs attributes, which, from
what I can see, is a day-one issue.
The other is a crash when accessing sysfs attributes, which I guess
crept in with
d84f2f5a7552 ("drivers/base/node.c: simplify 
unregister_memory_block_under_nodes()")
but it's hard to be sure.
And in either case, any of these is soo old as would affect pretty
much everyone.
(Oh fsck. _Someone_ will have to do the backports ...)

Anyway.

Cheers,

Hannes

-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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