mm/memory_hotplug: split memmap_on_memory requests across memblocks

The MHP_MEMMAP_ON_MEMORY flag for hotplugged memory is restricted to
'memblock_size' chunks of memory being added.  Adding a larger span of
memory precludes memmap_on_memory semantics.

For users of hotplug such as kmem, large amounts of memory might get added
from the CXL subsystem.  In some cases, this amount may exceed the
available 'main memory' to store the memmap for the memory being added. 
In this case, it is useful to have a way to place the memmap on the memory
being added, even if it means splitting the addition into memblock-sized
chunks.

Change add_memory_resource() to loop over memblock-sized chunks of memory
if caller requested memmap_on_memory, and if other conditions for it are
met.  Teach try_remove_memory() to also expect that a memory range being
removed might have been split up into memblock sized chunks, and to loop
through those as needed.

This does preclude being able to use PUD mappings in the direct map; a
proposal to how this could be optimized in the future is laid out here[1].

[1]: https://lore.kernel.org/linux-mm/[email protected]/

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Vishal Verma <[email protected]>
Suggested-by: David Hildenbrand <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Reviewed-by: "Huang, Ying" <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Cc: Fan Ni <[email protected]>
Cc: Jeff Moyer <[email protected]>
Cc: Jonathan Cameron <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions