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

[Kairui Song <ryncsn@gmail.com>]

On Wed, Oct 29, 2025 at 05:56:56PM +0800, Youngjun Park 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.
> 
> Signed-off-by: Youngjun Park <youngjun.park@lge.com>
> ---
>  mm/swapfile.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 6dc0e7a738bc..b5d42918c01b 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);

Good catch.

Is this introduced by 81a0298bdfab? So we need a Fixes: and backport to stable I think?

>  
>  	mutex_lock(&swapon_mutex);
> -- 
> 2.34.1
> 
>