From ebe945c27628fca03723582eba138acc2e2f3d15 Mon Sep 17 00:00:00 2001 From: Glauber Costa Date: Tue, 18 Dec 2012 14:23:10 -0800 Subject: memcg: add comments clarifying aspects of cache attribute propagation This patch clarifies two aspects of cache attribute propagation. First, the expected context for the for_each_memcg_cache macro in memcontrol.h. The usages already in the codebase are safe. In mm/slub.c, it is trivially safe because the lock is acquired right before the loop. In mm/slab.c, it is less so: the lock is acquired by an outer function a few steps back in the stack, so a VM_BUG_ON() is added to make sure it is indeed safe. A comment is also added to detail why we are returning the value of the parent cache and ignoring the children's when we propagate the attributes. Signed-off-by: Glauber Costa Cc: Michal Hocko Cc: Kamezawa Hiroyuki Cc: Johannes Weiner Acked-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memcontrol.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index ea02ff97083..0108a56f814 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -422,6 +422,12 @@ static inline void sock_release_memcg(struct sock *sk) extern struct static_key memcg_kmem_enabled_key; extern int memcg_limited_groups_array_size; + +/* + * Helper macro to loop through all memcg-specific caches. Callers must still + * check if the cache is valid (it is either valid or NULL). + * the slab_mutex must be held when looping through those caches + */ #define for_each_memcg_cache_index(_idx) \ for ((_idx) = 0; i < memcg_limited_groups_array_size; (_idx)++) -- cgit v1.2.3-18-g5258