linux-kernel - Re: [PATCH -V8 15/16] hugetlb/cgroup: migrate hugetlb cgroup info from oldpage to new page during migration

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Message-ID: <20120611092424.GJ12402@tiehlicka.suse.cz>
Date:	Mon, 11 Jun 2012 11:24:24 +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 15/16] hugetlb/cgroup: migrate hugetlb cgroup info
 from oldpage to new page during migration

On Sat 09-06-12 14:30:00, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
> 
> With HugeTLB pages, hugetlb cgroup is uncharged in compound page
> destructor.  Since we are holding a hugepage reference,

Who is holding that reference? I do not see anybody calling get_page in
this patch...

> we can be sure that old page won't get uncharged till the last
> put_page().
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> ---
>  include/linux/hugetlb_cgroup.h |    8 ++++++++
>  mm/hugetlb_cgroup.c            |   21 +++++++++++++++++++++
>  mm/migrate.c                   |    5 +++++
>  3 files changed, 34 insertions(+)
> 
> diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
> index ba4836f..b64d067 100644
> --- a/include/linux/hugetlb_cgroup.h
> +++ b/include/linux/hugetlb_cgroup.h
> @@ -63,6 +63,8 @@ extern void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
>  extern void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
>  					   struct hugetlb_cgroup *h_cg);
>  extern int hugetlb_cgroup_file_init(int idx) __init;
> +extern void hugetlb_cgroup_migrate(struct page *oldhpage,
> +				   struct page *newhpage);
>  #else
>  static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page)
>  {
> @@ -112,5 +114,11 @@ static inline int __init hugetlb_cgroup_file_init(int idx)
>  {
>  	return 0;
>  }
> +
> +static inline void hugetlb_cgroup_migrate(struct page *oldhpage,
> +					  struct page *newhpage)
> +{
> +	return;
> +}
>  #endif  /* CONFIG_MEM_RES_CTLR_HUGETLB */
>  #endif
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
> index c2b7b8e..2d384fe 100644
> --- a/mm/hugetlb_cgroup.c
> +++ b/mm/hugetlb_cgroup.c
> @@ -394,6 +394,27 @@ int __init hugetlb_cgroup_file_init(int idx)
>  	return 0;
>  }
>  
> +void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage)
> +{
> +	struct hugetlb_cgroup *h_cg;
> +
> +	VM_BUG_ON(!PageHuge(oldhpage));
> +
> +	if (hugetlb_cgroup_disabled())
> +		return;
> +
> +	spin_lock(&hugetlb_lock);
> +	h_cg = hugetlb_cgroup_from_page(oldhpage);
> +	set_hugetlb_cgroup(oldhpage, NULL);
> +	cgroup_exclude_rmdir(&h_cg->css);
> +
> +	/* move the h_cg details to new cgroup */
> +	set_hugetlb_cgroup(newhpage, h_cg);
> +	spin_unlock(&hugetlb_lock);
> +	cgroup_release_and_wakeup_rmdir(&h_cg->css);
> +	return;
> +}
> +
>  struct cgroup_subsys hugetlb_subsys = {
>  	.name = "hugetlb",
>  	.create     = hugetlb_cgroup_create,
> diff --git a/mm/migrate.c b/mm/migrate.c
> index fdce3a2..6c37c51 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -33,6 +33,7 @@
>  #include <linux/memcontrol.h>
>  #include <linux/syscalls.h>
>  #include <linux/hugetlb.h>
> +#include <linux/hugetlb_cgroup.h>
>  #include <linux/gfp.h>
>  
>  #include <asm/tlbflush.h>
> @@ -931,6 +932,10 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>  
>  	if (anon_vma)
>  		put_anon_vma(anon_vma);
> +
> +	if (!rc)
> +		hugetlb_cgroup_migrate(hpage, new_hpage);
> +
>  	unlock_page(hpage);
>  out:
>  	put_page(new_hpage);
> -- 
> 1.7.10
> 

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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