Re: [PATCH v4 2/7] mm: allow shared folios to be promoted to a fast tier

[David Hildenbrand (Arm)]

On 9/30/26 13:22, Gregory Price wrote:
> From: "Gregory Price (Meta)" <gourry@xxxxxxxxxx>
> 
> NUMA balancing rejects shared copy-on-write folios and executable
> file folios mapped by multiple processes to avoid east-west
> migration bouncing. These checks break promotion from slow memory.
> 
> Allow such folios to participate when the folio being migrated is
> a low-tier folio and the destination is top-tier (south->north).
> This allows promotion, but prevents east-west or north->south
> migrations (north->south is handled by reclaim demotion).
> 
> Keep the existing restrictions for ordinary placement and for
> migrations that are not slow-to-top-tier promotions.
> 
> Rename folio_use_access_time() to folio_numab_promotable() so the name
> captures the combined memory-tiering and source-tier test. The helper
> retains its existing behavior.
> 
> Fixes: c574bbe91703 ("NUMA balancing: optimize page placement for memory tiering system")
> Cc: stable@xxxxxxxxxxxxxxx
> Suggested-by: Zi Yan <ziy@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/DLHS4KFPQ86I.1J4LN3352RI71@xxxxxxxxxx
> Assisted-by: LLM
> Signed-off-by: Gregory Price (Meta) <gourry@xxxxxxxxxx>
> ---

Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David