linux-kernel - Re: [PATCH 04/13] mm: Track NR_KERNEL_STACK in pages instead of number of stacks

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Message-ID: <CALCETrU4bcLyBJDVOPCW_MobQVGPiHRP+KfZMGu8YQJHnmjYeQ@mail.gmail.com>
Date:	Thu, 16 Jun 2016 10:21:26 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Andy Lutomirski <luto@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 04/13] mm: Track NR_KERNEL_STACK in pages instead of
 number of stacks

On Thu, Jun 16, 2016 at 4:10 AM, Vladimir Davydov
<vdavydov@...tuozzo.com> wrote:
> On Wed, Jun 15, 2016 at 05:28:26PM -0700, Andy Lutomirski wrote:
> ...
>> @@ -225,7 +225,8 @@ static void account_kernel_stack(struct thread_info *ti, int account)
>>  {
>>       struct zone *zone = page_zone(virt_to_page(ti));
>>
>> -     mod_zone_page_state(zone, NR_KERNEL_STACK, account);
>> +     mod_zone_page_state(zone, NR_KERNEL_STACK,
>> +                         THREAD_SIZE / PAGE_SIZE * account);
>
> It won't work if THREAD_SIZE < PAGE_SIZE. Is there an arch with such a
> thread size, anyway? If no, we should probably drop thread_info_cache.

On a quick grep, I can't find any.  I'll add a BUILD_BUG_ON for now.

--Andy