Re: [PATCH v3 11/14] mm, swap: require zswap for xswap devices

[Chris Li]

On Wed, Sep 16, 2026 at 12:21 AM Baoquan He <hebaoquan@xxxxxxxxxx> wrote:
>
> xswap pages live only in zswap. Without zswap, swapout cannot free the page,
> but still takes a swap entry. So the device consumes swap entries without
> freeing memory. Fail to create a device when zswap is unavailable.
>
> Signed-off-by: Baoquan He <hebaoquan@xxxxxxxxxx>

Acked-by: Chris Li <chrisl@xxxxxxxxxx>

Chris

> ---
>  mm/swapfile.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index cdcbcbaa6d87..cac084bc72d6 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -4439,6 +4439,10 @@ static int xswap_create(int prio)
>         if (prio != DEF_SWAP_PRIO && (prio < 0 || prio > SWAP_FLAG_PRIO_MASK))
>                 return -EINVAL;
>
> +       /* xswap has no backing store, it relies on zswap. */
> +       if (!zswap_is_enabled())
> +               return -EOPNOTSUPP;
> +
>         si = alloc_swap_info();
>         if (IS_ERR(si))
>                 return PTR_ERR(si);
> --
> 2.54.0
>