From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH 11/11] protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs Date: Tue, 26 Jun 2012 12:44:13 +0400 Message-ID: <4FE9765D.2050301@parallels.com> References: <1340633728-12785-1-git-send-email-glommer@parallels.com> <1340633728-12785-12-git-send-email-glommer@parallels.com> <4FE96358.6080601@parallels.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: David Rientjes Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Andrew Morton , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Frederic Weisbecker , Pekka Enberg , Michal Hocko , Johannes Weiner , Christoph Lameter , devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, Tejun Heo , Pekka Enberg , Suleiman Souhlal , Frederic Weisbecker On 06/26/2012 12:45 PM, David Rientjes wrote: > On Tue, 26 Jun 2012, Glauber Costa wrote: > >>>> diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h >>>> index ccc1899..914ec07 100644 >>>> --- a/include/linux/thread_info.h >>>> +++ b/include/linux/thread_info.h >>>> @@ -61,6 +61,12 @@ extern long do_no_restart_syscall(struct restart_block >>>> *parm); >>>> # define THREADINFO_GFP (GFP_KERNEL | __GFP_NOTRACK) >>>> #endif >>>> >>>> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM >>>> +# define THREADINFO_GFP_ACCOUNTED (THREADINFO_GFP | __GFP_KMEMCG) >>>> +#else >>>> +# define THREADINFO_GFP_ACCOUNTED (THREADINFO_GFP) >>>> +#endif >>>> + >>> >>> This type of requirement is going to become nasty very quickly if nobody >>> can use __GFP_KMEMCG without testing for CONFIG_CGROUP_MEM_RES_CTLR_KMEM. >>> Perhaps define __GFP_KMEMCG to be 0x0 if it's not enabled, similar to how >>> kmemcheck does? >>> >> That is what I've done in my first version of this patch. At that time, >> Christoph wanted it to be this way so we would make sure it would never be >> used with #CONFIG_CGROUP_MEM_RES_CTLR_KMEM defined. A value of zero will >> generate no errors. Undefined value will. >> >> Now, if you ask me, I personally prefer following what kmemcheck does here... >> > > Right, because I'm sure that __GFP_KMEMCG will be used in additional > places outside of this patchset and it will be a shame if we have to > always add #ifdef's. I see no reason why we would care if __GFP_KMEMCG > was used when CONFIG_CGROUP_MEM_RES_CTLR_KMEM=n with the semantics that it > as in this patchset. It's much cleaner by making it 0x0 when disabled. > What I can do, instead, is to WARN_ON conditionally to the config option in the page allocator, and make sure no one is actually passing the flag in that case.