linux-kernel - Re: [PATCH][BUGFIX] memcg: fix for deadlock between lock_page_cgroup and mapping tree

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Date:	Wed, 13 May 2009 08:59:49 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	nishimura@....nes.nec.co.jp
Cc:	Daisuke Nishimura <d-nishimura@....biglobe.ne.jp>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	mingo@...e.hu,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][BUGFIX] memcg: fix for deadlock between
 lock_page_cgroup and mapping tree_lock

On Tue, 12 May 2009 19:58:23 +0900
Daisuke Nishimura <d-nishimura@....biglobe.ne.jp> wrote:

> On Tue, 12 May 2009 17:13:56 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
> > On Tue, 12 May 2009 17:00:07 +0900
> > Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:
> > > hmm, I see.
> > > cache_charge is outside of tree_lock, so moving uncharge would make sense.
> > > IMHO, we should make the period of spinlock as small as possible,
> > > and charge/uncharge of pagecache/swapcache is protected by page lock, not tree_lock.
> > > 
> > How about this ?
> Looks good conceptually, but it cannot be built :)
> 
> It needs a fix like this.
> Passed build test with enabling/disabling both CONFIG_MEM_RES_CTLR
> and CONFIG_SWAP.
> 
ok, will update. can I add you Signed-off-by on the patch ?

Thanks,
-Kame
> ===
>  include/linux/swap.h |    5 +++++
>  mm/memcontrol.c      |    4 +++-
>  mm/swap_state.c      |    4 +---
>  mm/vmscan.c          |    2 +-
>  4 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index caf0767..6ea541d 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -431,6 +431,11 @@ static inline swp_entry_t get_swap_page(void)
>  #define has_swap_token(x) 0
>  #define disable_swap_token() do { } while(0)
>  
> +static inline void
> +mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
> +{
> +}
> +
>  #endif /* CONFIG_SWAP */
>  #endif /* __KERNEL__*/
>  #endif /* _LINUX_SWAP_H */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 0c9c1ad..89523cf 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1488,8 +1488,9 @@ void mem_cgroup_uncharge_cache_page(struct page *page)
>  	__mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE);
>  }
>  
> +#ifdef CONFIG_SWAP
>  /*
> - * called from __delete_from_swap_cache() and drop "page" account.
> + * called after __delete_from_swap_cache() and drop "page" account.
>   * memcg information is recorded to swap_cgroup of "ent"
>   */
>  void mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
> @@ -1506,6 +1507,7 @@ void mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
>  	if (memcg)
>  		css_put(&memcg->css);
>  }
> +#endif
>  
>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
>  /*
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 87f10d4..7624c89 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -109,8 +109,6 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
>   */
>  void __delete_from_swap_cache(struct page *page)
>  {
> -	swp_entry_t ent = {.val = page_private(page)};
> -
>  	VM_BUG_ON(!PageLocked(page));
>  	VM_BUG_ON(!PageSwapCache(page));
>  	VM_BUG_ON(PageWriteback(page));
> @@ -190,7 +188,7 @@ void delete_from_swap_cache(struct page *page)
>  	__delete_from_swap_cache(page);
>  	spin_unlock_irq(&swapper_space.tree_lock);
>  
> -	mem_cgroup_uncharge_swapcache(page, ent);
> +	mem_cgroup_uncharge_swapcache(page, entry);
>  	swap_free(entry);
>  	page_cache_release(page);
>  }
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 6c5988d..a7d7a06 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -470,7 +470,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page)
>  		swp_entry_t swap = { .val = page_private(page) };
>  		__delete_from_swap_cache(page);
>  		spin_unlock_irq(&mapping->tree_lock);
> -		mem_cgroup_uncharge_swapcache(page);
> +		mem_cgroup_uncharge_swapcache(page, swap);
>  		swap_free(swap);
>  	} else {
>  		__remove_from_page_cache(page);
> ===
> --
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