From fdf1cdb91b6ab7a8a91df68c384f36b8a0909cab Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Tue, 15 Mar 2016 14:57:25 -0700 Subject: mm: remove unnecessary uses of lock_page_memcg() There are several users that nest lock_page_memcg() inside lock_page() to prevent page->mem_cgroup from changing. But the page lock prevents pages from moving between cgroups, so that is unnecessary overhead. Remove lock_page_memcg() in contexts with locked contexts and fix the debug code in the page stat functions to be okay with the page lock. Signed-off-by: Johannes Weiner Acked-by: Vladimir Davydov Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memcontrol.h | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'include/linux/memcontrol.h') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index d560c9a3cadf..f0c4bec6565b 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -28,6 +28,7 @@ #include #include #include +#include struct mem_cgroup; struct page; @@ -464,18 +465,19 @@ void unlock_page_memcg(struct page *page); * @idx: page state item to account * @val: number of pages (positive or negative) * - * Callers must use lock_page_memcg() to prevent double accounting - * when the page is concurrently being moved to another memcg: + * The @page must be locked or the caller must use lock_page_memcg() + * to prevent double accounting when the page is concurrently being + * moved to another memcg: * - * lock_page_memcg(page); + * lock_page(page) or lock_page_memcg(page) * if (TestClearPageState(page)) * mem_cgroup_update_page_stat(page, state, -1); - * unlock_page_memcg(page); + * unlock_page(page) or unlock_page_memcg(page) */ static inline void mem_cgroup_update_page_stat(struct page *page, enum mem_cgroup_stat_index idx, int val) { - VM_BUG_ON(!rcu_read_lock_held()); + VM_BUG_ON(!(rcu_read_lock_held() || PageLocked(page))); if (page->mem_cgroup) this_cpu_add(page->mem_cgroup->stat->count[idx], val); -- cgit v1.2.3