Re: [PATCH v3 10/11] mm/memory_hotplug: Make unregister_memory_block_under_nodes() never fail

[David Hildenbrand <david@xxxxxxxxxx>]

On 01.07.19 12:27, Michal Hocko wrote:
> On Mon 01-07-19 11:36:44, Oscar Salvador wrote:
>> On Mon, Jul 01, 2019 at 10:51:44AM +0200, Michal Hocko wrote:
>>> Yeah, we do not allow to offline multi zone (node) ranges so the current
>>> code seems to be over engineered.
>>>
>>> Anyway, I am wondering why do we have to strictly check for already
>>> removed nodes links. Is the sysfs code going to complain we we try to
>>> remove again?
>>
>> No, sysfs will silently "fail" if the symlink has already been removed.
>> At least that is what I saw last time I played with it.
>>
>> I guess the question is what if sysfs handling changes in the future
>> and starts dropping warnings when trying to remove a symlink is not there.
>> Maybe that is unlikely to happen?
> 
> And maybe we handle it then rather than have a static allocation that
> everybody with hotremove configured has to pay for.
> 

So what's the suggestion? Dropping the nodemask_t completely and calling
sysfs_remove_link() on already potentially removed links?

Of course, we can also just use mem_blk->nid and rest assured that it
will never be called for memory blocks belonging to multiple nodes.

-- 

Thanks,

David / dhildenb