linux-kernel - Re: [RFC PATCH] mm/damon/core: avoid overflow in damon_feed_loop_next

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Message-ID: <47fae3a3-3597-43ef-961b-c47558a779ab@roeck-us.net>
Date: Fri, 1 Nov 2024 07:16:57 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: SeongJae Park <sj@...nel.org>
Cc: damon@...ts.linux.dev, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] mm/damon/core: avoid overflow in
 damon_feed_loop_next_input()

Hi,

On 10/30/24 22:21, SeongJae Park wrote:
> Hi Guenter,
> 
> On Wed, 30 Oct 2024 21:18:51 -0700 Guenter Roeck <linux@...ck-us.net> wrote:
> 
>> On Thu, Sep 05, 2024 at 10:24:05AM -0700, SeongJae Park wrote:
>>> damon_feed_loop_next_input() is fragile to overflows.  Rewrite code to
>>> avoid overflows.  This is not yet well tested on 32bit archs.
>>>
>>> Reported-by: Guenter Roeck <linux@...ck-us.net>
>>> Closes: https://lore.kernel.org/944f3d5b-9177-48e7-8ec9-7f1331a3fea3@roeck-us.net
>>> Fixes: 9294a037c015 ("mm/damon/core: implement goal-oriented feedback-driven quota auto-tuning")
>>> Signed-off-by: SeongJae Park <sj@...nel.org>
>>> ---
>>> As mentioned on the commit message, this is not yet sufficiently tested
>>> on 32bit machines.  That's why this is RFC.
>>
>> Is that patch going anywhere ? I have been testing it on a lot of 32-bit architectures,
>> and I do not see any failures.
> 
> Thank you for this nice reminder with the grateful test results, Guenter!
> 
> I was recently cleaning up the code and commit message, and testing on my own
> with test setup.  I should confess that it took more than I expected in the
> last RFC posting.  Sorry for the delay, and thank you for your patience.
> 
No worries; I just didn't want it to get lost.

> I believe the patch is now in good form, but I was waiting just a couple of
> more days before posting it, for a case that I find any mistake on it.  So
> unless I find something wrong on the patch by Tomorrow morning (Pacific Time),
> I will post it after dropping the RFC tag.
> 
> The current version of the patch to be posted is available at my patches
> queue[1].  Please let me know if you find anything suspicious on it.
> 
> Thank you again for your patience and nice reminder!
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/sj/damon-hack.git/tree/patches/next/mm-damon-core-avoid-overflow-in-damon_feed_loop_next.patch?id=fb13d053bfdd5249bebdd1c253417f97cd41471e
> 

I already got that version of the patch per e-mail yesterday. I re-tested it
in my testbed last night, and it (still) works as expected. So, again, for
the record:

Tested-by: Guenter Roeck <linux@...ck-us.net>

Thanks,
Guenter