Re: [PATCH v1] drivers/base/node.c: Simplify unregister_memory_block_under_nodes()

[Michal Hocko]

On Fri 19-07-19 11:05:51, David Hildenbrand wrote:
> On 19.07.19 10:42, Michal Hocko wrote:
> > On Thu 18-07-19 16:22:39, David Hildenbrand wrote:
> >> We don't allow to offline memory block devices that belong to multiple
> >> numa nodes. Therefore, such devices can never get removed. It is
> >> sufficient to process a single node when removing the memory block.
> >>
> >> Remember for each memory block if it belongs to no, a single, or mixed
> >> nodes, so we can use that information to skip unregistering or print a
> >> warning (essentially a safety net to catch BUGs).
> > 
> > I do not really like NUMA_NO_NODE - 1 thing. This is yet another invalid
> > node that is magic. Why should we even care? In other words why is this
> > patch an improvement?
> 
> Oh, and to answer that part of the question:
> 
> We no longer have to iterate over each pfn of a memory block to be removed.

Is it possible that we are overzealous when unregistering syfs files and
we should simply skip the pfn walk even without this change?

-- 
Michal Hocko
SUSE Labs