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Subject: Re: [RFC PATCH 2/2] mm: readahead: handle LARGE input to
 get_init_ra_size()
From:   Randy Dunlap <rdunlap@infradead.org>
To:     =?UTF-8?Q?Toralf_F=c3=b6rster?= <toralf.foerster@gmx.de>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        linux-mm@kvack.org
References: <20201220211051.1416-1-rdunlap@infradead.org>
 <20201222173533.c9e28416835d7487b0e28cda@linux-foundation.org>
 <6a595671-20a8-e63f-f3ea-f4749a574efa@infradead.org>
 <d2edfb69-93b4-d938-faf0-5f7c0f1158b9@gmx.de>
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Message-ID: <bb5d8aee-96bf-4403-6a64-27f4c1159320@infradead.org>
Date:   Tue, 29 Dec 2020 12:00:36 -0800
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On 12/29/20 10:11 AM, Randy Dunlap wrote:
> On 12/29/20 10:01 AM, Toralf Förster wrote:
>> On 12/23/20 2:50 AM, Randy Dunlap wrote:
>>>> What motivates this change?  Is there any reason to think this can
>>>> happen?
>>> Spotted in the wild:
>> I run 2 hardened Gentoo systems, a server and a desktop.
>>
>> I patched the server with this:
>>
>> mr-fox ~ # cat ubsan.patch
>> --- linux-5.10.1.orig/mm/readahead.c
>> +++ linux-5.10.1/mm/readahead.c
>> @@ -310,7 +310,11 @@ void force_page_cache_ra(struct readahea
>>   */
>>  static unsigned long get_init_ra_size(unsigned long size, unsigned
>> long max)
>>  {
>> -       unsigned long newsize = roundup_pow_of_two(size);
>> +       unsigned long newsize;
>> +
>> +       if (!size)
>> +               size = 32;
>> +       newsize = roundup_pow_of_two(size);
>>
>>         if (newsize <= max / 32)
>>                 newsize = newsize * 4;
>>
>>
>>
>> and the issue did no longer occurred at the server (5.10.2).
>>
>> I did not patched the desktop system and the issue occurred still 3
>> times since 21th of december (5.10.2/3)
> 
> Yes, that's the patch that I posted on 2020-DEC-22.
> 
> Looks like I should submit a real patch for that.
> 
> thanks.
> 

Hi Toralf,

Do you want either or both of your
Reported-by: and Tested-by: on the patch?

thanks.
-- 
~Randy