linux-kernel - Re: [PATCH -V8 12/16] hugetlb/cgroup: Add support for cgroup removal

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]

Message-ID: <20120611131411.GN12402@tiehlicka.suse.cz>
Date:	Mon, 11 Jun 2012 15:14:11 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	linux-mm@...ck.org, kamezawa.hiroyu@...fujitsu.com,
	dhillf@...il.com, rientjes@...gle.com, akpm@...ux-foundation.org,
	hannes@...xchg.org, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org
Subject: Re: [PATCH -V8 12/16] hugetlb/cgroup: Add support for cgroup removal

On Mon 11-06-12 15:10:20, Aneesh Kumar K.V wrote:
> Michal Hocko <mhocko@...e.cz> writes:
[...]
> >> +static int hugetlb_cgroup_move_parent(int idx, struct cgroup *cgroup,
> >> +				      struct page *page)
> >
> > deserves a comment about the locking (needs to be called with
> > hugetlb_lock).
> 
> will do
> 
> >
> >> +{
> >> +	int csize;
> >> +	struct res_counter *counter;
> >> +	struct res_counter *fail_res;
> >> +	struct hugetlb_cgroup *page_hcg;
> >> +	struct hugetlb_cgroup *h_cg   = hugetlb_cgroup_from_cgroup(cgroup);
> >> +	struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(cgroup);
> >> +
> >> +	if (!get_page_unless_zero(page))
> >> +		goto out;
> >> +
> >> +	page_hcg = hugetlb_cgroup_from_page(page);
> >> +	/*
> >> +	 * We can have pages in active list without any cgroup
> >> +	 * ie, hugepage with less than 3 pages. We can safely
> >> +	 * ignore those pages.
> >> +	 */
> >> +	if (!page_hcg || page_hcg != h_cg)
> >> +		goto err_out;
> >
> > How can we have page_hcg != NULL && page_hcg != h_cg?
> 
> pages belonging to other cgroup ?

OK, I've forgot that you are iterating over all active huge pages in
hugetlb_cgroup_pre_destroy. What prevents you from doing the filtering
in the caller? 
I am also wondering why you need to play with the page reference
counting here. You are under hugetlb_lock so the page cannot disappear
in the meantime or am I missing something?
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
--
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/