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

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Date:	Tue, 12 May 2009 19:58:23 +0900
From:	Daisuke Nishimura <d-nishimura@....biglobe.ne.jp>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	d-nishimura@....biglobe.ne.jp,
	Daisuke Nishimura <nishimura@....nes.nec.co.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 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.

===
 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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