> Because those architectures will draw their stacks directly from
> the page allocator, rather than the slab cache, we can directly
> pass __GFP_KMEMCG flag, and issue the corresponding free_pages.
>
> This code path is taken when the architecture doesn't define
> CONFIG_ARCH_THREAD_INFO_ALLOCATOR (only ia64 seems to), and has
> THREAD_SIZE >= PAGE_SIZE. Luckily, most - if not all - of the
> remaining architectures fall in this category.
>
> This will guarantee that every stack page is accounted to the memcg
> the process currently lives on, and will have the allocations to fail
> if they go over limit.
>
> For the time being, I am defining a new variant of THREADINFO_GFP, not
> to mess with the other path. Once the slab is also tracked by memcg,
> we can get rid of that flag.
>
> Tested to successfully protect against :(){ :|:& };:
>
> Signed-off-by: Glauber Costa <glommer@parallels.com>
> CC: Christoph Lameter <cl@linux.com>
> CC: Pekka Enberg <penberg@cs.helsinki.fi>
> CC: Michal Hocko <mhocko@suse.cz>
> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> CC: Johannes Weiner <hannes@cmpxchg.org>
> CC: Suleiman Souhlal <suleiman@google.com>
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