linux-kernel - Re: memcg uncharge page counter mismatch

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 4 Dec 2015 14:35:15 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: memcg uncharge page counter mismatch

On Thu, Dec 03, 2015 at 04:47:29PM +0100, Michal Hocko wrote:
> On Thu 03-12-15 15:58:50, Michal Hocko wrote:
> [....]
> > Warning, this looks ugly as hell.
> 
> I was thinking about it some more and it seems that we should rather not
> bother with partial thp at all and keep it in the original memcg
> instead. It is way much less code and I do not think this will be too
> disruptive. Somebody should be holding the thp head, right?
> 
> Minchan, does this fix the issue you are seeing.

This patch solves the issue but not sure it's right approach.
I think it could make regression that in old, we could charge
a THP page but we can't now. Whether it's trivial or not, it depends
on memcg guys.

Thanks.


> ---
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 79a29d564bff..143c933f0b81 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4895,6 +4895,14 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
>  		switch (get_mctgt_type(vma, addr, ptent, &target)) {
>  		case MC_TARGET_PAGE:
>  			page = target.page;
> +			/*
> +			 * We can have a part of the split pmd here. Moving it
> +			 * can be done but it would be too convoluted so simply
> +			 * ignore such a partial THP and keep it in original
> +			 * memcg. There should be somebody mapping the head.
> +			 */
> +			if (PageCompound(page))
> +				goto put;
>  			if (isolate_lru_page(page))
>  				goto put;
>  			if (!mem_cgroup_move_account(page, false,
> -- 
> Michal Hocko
> SUSE Labs

-- 
Kind regards,
Minchan Kim
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/