[RFC PATCH 8/8] HACK: mm: memory_hotplug: Drop memblock_phys_free() call in try_remove_memory()

[Oscar Salvador]

On Wed, May 29, 2024 at 06:12:36PM +0100, Jonathan Cameron wrote:
> I'm not sure what this is balancing, but it if is necessary then the reserved
> memblock approach can't be used to stash NUMA node assignments as after the
> first add / remove cycle the entry is dropped so not available if memory is
> re-added at the same HPA.

It is balancing previously allocated memory which was allocated via
memblock_phys_alloc{_range,try_nid}.
memblock_phys_alloc_try_nid() is who does the heavy-lifting, and also calls
kmemleak_alloc_phys() to make kmemleak aware of that memory.

A quick idea that came to me is:
I think that it should be possible 1) create a new memory_block flag
(check 'enum memblock_flags') and 2) flag the range you want with this
range (check memblock_setclr_flag()) with a function like
memblock_reserved_mark_{yourflag}.

Then, in memblock_phys_free() (or down the path) we could check for that flag,
and refuse to proceed if it is set.

Would that work?
I am not sure, but you might need to 


-- 
Oscar Salvador
SUSE Labs