Re: [PATCH v2 1/3] mm, swap: ratelimit bad swap entry reports

[Kairui Song <ryncsn@gmail.com>]

On Thu, Aug 13, 2026 at 03:02:20AM +0800, Breno Leitao wrote:
> A corrupt page table hands the same bogus entry to get_swap_device() on
> every access to the mapping, and every rejection is logged. One machine
> logged 6185620 copies of the same line in a few hours.
> 
> swap_dup_entry_direct() prints the same message from the fork path, once
> per call: the WARN_ON_ONCE() guarding it warns once, the pr_err() inside
> does not.
> 
> Rate limit all three prints.
> 
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---
>  mm/swapfile.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 4d4e3e3059f6b..31c8a340606bb 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1899,11 +1899,11 @@ struct swap_info_struct *get_swap_device(swp_entry_t entry)
>  
>  	return si;
>  bad_nofile:
> -	pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
> +	pr_err_ratelimited("%s: %s%08lx\n", __func__, Bad_file, entry.val);
>  out:
>  	return NULL;
>  put_out:
> -	pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
> +	pr_err_ratelimited("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
>  	percpu_ref_put(&si->users);
>  	return NULL;
>  }
> @@ -3876,7 +3876,7 @@ int swap_dup_entry_direct(swp_entry_t entry)
>  
>  	si = swap_entry_to_info(entry);
>  	if (WARN_ON_ONCE(!si)) {
> -		pr_err("%s%08lx\n", Bad_file, entry.val);
> +		pr_err_ratelimited("%s%08lx\n", Bad_file, entry.val);
>  		return -EINVAL;
>  	}
>  

Looks good to me, thanks!

Acked-by: Kairui Song <kasong@tencent.com>