Re: [PATCH v3 08/19] mm/shmem, swap: remove SWAP_MAP_SHMEM

[Baolin Wang]

On 2025/11/25 03:13, Kairui Song wrote:
> From: Nhat Pham <nphamcs@xxxxxxxxx>
>
> The SWAP_MAP_SHMEM state was introduced in the commit aaa468653b4a
> ("swap_info: note SWAP_MAP_SHMEM"), to quickly determine if a swap entry
> belongs to shmem during swapoff.
>
> However, swapoff has since been rewritten in the commit b56a2d8af914
> ("mm: rid swapoff of quadratic complexity"). Now having swap count ==
> SWAP_MAP_SHMEM value is basically the same as having swap count == 1,
> and swap_shmem_alloc() behaves analogously to swap_duplicate(). The only
> difference of note is that swap_shmem_alloc() does not check for
> -ENOMEM returned from __swap_duplicate(), but it is OK because shmem
> never re-duplicates any swap entry it owns. This will stil be safe if we
> use (batched) swap_duplicate() instead.
>
> This commit adds swap_duplicate_nr(), the batched variant of
> swap_duplicate(), and removes the SWAP_MAP_SHMEM state and the
> associated swap_shmem_alloc() helper to simplify the state machine (both
> mentally and in terms of actual code). We will also have an extra
> state/special value that can be repurposed (for swap entries that never
> gets re-duplicated).
>
> Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
> Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
> ---

LGTM. Thanks.
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Tested-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>