Re: [PATCH 1/3] mm, swap: ratelimit bad swap entry reports in get_swap_device()

["David Hildenbrand (Arm)" <david@kernel.org>]

On 8/11/26 18:48, Pedro Falcato wrote:
> On Tue, Aug 11, 2026 at 05:33:54PM +0200, David Hildenbrand (Arm) wrote:
>> On 8/10/26 18:26, 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.
>>>
>>> Rate limit both prints.
>>>
>>> Signed-off-by: Breno Leitao <leitao@debian.org>
>>> ---
>>>  mm/swapfile.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/mm/swapfile.c b/mm/swapfile.c
>>> index 4d4e3e3059f6b..9ab11dc24e4f1 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;
>>>  }
>>>
>>
>> In print_bad_page_map() we use something more advanced
>> (is_bad_page_map_ratelimited): essentially a burst of 60 followed by 1minute of
>> silence.
> 
> Is it more advanced? It just looks like a handcoded version of __ratelimit.
> 
> ... I hate it now. I'll send a patch I guess.

Thanks for cleaning that up!

-- 
Cheers,

David