Re: [PATCH v2 2/5] mm, swap: Use SWP_SOLIDSTATE to determine if swap is rotational

[Chris Li <chrisl@kernel.org>]

Acked-by: Chris Li <chrisl@kernel.org>

Chris

On Thu, Oct 30, 2025 at 11:54 PM Youngjun Park <youngjun.park@lge.com> wrote:
>
> The current non rotational check is unreliable
> as the device's rotational status can be changed by a user via sysfs.
>
> Use the more reliable SWP_SOLIDSTATE flag which is set at swapon time,
> to ensure the nr_rotate_swap count remains consistent.
> Plus, it is easy to read and simple.
>
> Fixes: 81a0298bdfab ("mm, swap: don't use VMA based swap readahead if HDD is used as swap")
> Signed-off-by: Youngjun Park <youngjun.park@lge.com>
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index ed2c8e4edb71..b7cde8ef6742 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -2913,7 +2913,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
>         if (p->flags & SWP_CONTINUED)
>                 free_swap_count_continuations(p);
>
> -       if (!p->bdev || !bdev_nonrot(p->bdev))
> +       if (!(p->flags & SWP_SOLIDSTATE))
>                 atomic_dec(&nr_rotate_swap);
>
>         mutex_lock(&swapon_mutex);
> --
> 2.34.1
>