memcg: fix deadlock between lock_page_cgroup and mapping tree_lock

mapping->tree_lock can be acquired from interrupt context.  Then,
following dead lock can occur.

Assume "A" as a page.

 CPU0:
       lock_page_cgroup(A)
		interrupted
			-> take mapping->tree_lock.
 CPU1:
       take mapping->tree_lock
		-> lock_page_cgroup(A)

This patch tries to fix above deadlock by moving memcg's hook to out of
mapping->tree_lock.  charge/uncharge of pagecache/swapcache is protected
by page lock, not tree_lock.

After this patch, lock_page_cgroup() is not called under mapping->tree_lock.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5fa3eda1f03f..d254306562cd 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -470,10 +470,12 @@ 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, swap);
                 swap_free(swap);
         } else {
                 __remove_from_page_cache(page);
                 spin_unlock_irq(&mapping->tree_lock);
+                mem_cgroup_uncharge_cache_page(page);
         }
 
         return 1;