Re: [PATCH v3 15/18] mm/huge_memory: lift order-0 restriction for swapcache split

[David Hildenbrand (Arm)]

On 8/20/26 20:55, Kairui Song via B4 Relay wrote:
> From: Kairui Song <kasong@xxxxxxxxxxx>
> 
> The restriction that swapcache folios can only be uniformly split to
> order 0 dates back to when the swap cache was managed via address_space
> mapping (swap_address_space).  The old split loop only created order-0
> sub-folios with a fixed stride, so non-uniform split and non-zero order
> were rightfully blocked.
> 
> After the swap cache switched to swap table under a cluster lock,
> __swap_cache_replace_folio already gained the ability to replace any
> number of entries for any sub-folio size in one cluster, and the old
> swap_address_space locking and limit was removed. The restriction
> became obsolete but persisted through multiple refactorings.
> 
> Drop it now: swapcache folios can be split to any supported order with
> either uniform or non-uniform split, except order-1 which is not
> supported for anon folios. Mappingless swap cache folios could be either
> anon or shmem, so for now we just simply forbid order-1 for all swapcache.
> 
> Acked-by: Zi Yan <ziy@xxxxxxxxxx>
> Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
> ---

In contrast to the other cleanup patches, this patch changes behavior.

I would suggest to send all cleanups first, and send this out separately, such
that it gets proper attention and doesn't get buried in a sequence of
harmlessly-looking cleanups :)

-- 
Cheers,

David