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From: Randy Dunlap <rdunlap@infradead.org>
To: "Toralf Förster" <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
Subject: Re: [RFC PATCH 2/2] mm: readahead: handle LARGE input to get_init_ra_size()
Date: Tue, 29 Dec 2020 10:11:11 -0800	[thread overview]
Message-ID: <1f5a6e7b-c779-861e-fde8-409ca8e2541b@infradead.org> (raw)
In-Reply-To: <d2edfb69-93b4-d938-faf0-5f7c0f1158b9@gmx.de>

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.
-- 
~Randy


  reply	other threads:[~2020-12-29 18:14 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-20 21:10 Randy Dunlap
2020-12-23  1:35 ` Andrew Morton
2020-12-23  1:50   ` Randy Dunlap
2020-12-29 18:01     ` Toralf Förster
2020-12-29 18:11       ` Randy Dunlap [this message]
2020-12-29 20:00         ` Randy Dunlap
2020-12-29 20:46           ` Toralf Förster

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