Re: [PATCH v3 1/3] mm/swap: move LRU insertion out of the swap cache allocator

[Usama Arif]

On Tue, 25 Aug 2026 19:24:51 +0200 Alexandre Ghiti <alex@xxxxxxxx> wrote:

> This is a preparatory patch.
> 
> __swap_cache_alloc_folio() adds the new folio to the LRU itself, which
> leaves its callers no way to act on the folio before it becomes visible
> to reclaim.  Two users need exactly that:
> 
>  - the next patch moves the refault evaluation out of the swap cache
>    folio allocation, and it has to happen before folio_add_lru(): that
>    consumes PG_active to file the folio on the inactive or the active
>    list, and under MGLRU it also reads PG_workingset to pick the
>    generation.  Setting either flag afterwards does not move the folio;
> 
>  - the upcoming zswap writeback dropbehind implementation needs the
>    buffer folio to stay off the LRU entirely, as the per-CPU LRU batch
>    would hold a reference on it and keep remove_mapping() from freeing
>    it once writeback completes.
> 

I think the kernel convention is to not say "next patch" and "upcoming.."

Especially as this patch is in 2 series, so you don't know where it will land.

> Defer the LRU insertion to the callers of __swap_cache_alloc_folio():
> each of them adds the folio right after the allocation, so there is no
> functional change intended.
> 
> Suggested-by: Kairui Song <kasong@xxxxxxxxxxx>
> Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>


The code change itself looks good to me, so once the commit message is fixed:
Acked-by: Usama Arif <usama.arif@xxxxxxxxx>