From 45c7f7e1ef17f09fe70bad4b705ce43772153fd7 Mon Sep 17 00:00:00 2001 From: Chris Down Date: Thu, 6 Aug 2020 23:22:05 -0700 Subject: mm, memcg: decouple e{low,min} state mutations from protection checks mem_cgroup_protected currently is both used to set effective low and min and return a mem_cgroup_protection based on the result. As a user, this can be a little unexpected: it appears to be a simple predicate function, if not for the big warning in the comment above about the order in which it must be executed. This change makes it so that we separate the state mutations from the actual protection checks, which makes it more obvious where we need to be careful mutating internal state, and where we are simply checking and don't need to worry about that. [mhocko@suse.com - don't check protection on root memcgs] Suggested-by: Johannes Weiner Signed-off-by: Chris Down Signed-off-by: Andrew Morton Acked-by: Johannes Weiner Acked-by: Michal Hocko Cc: Roman Gushchin Cc: Yafang Shao Link: http://lkml.kernel.org/r/ff3f915097fcee9f6d7041c084ef92d16aaeb56a.1594638158.git.chris@chrisdown.name Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 28 +++++++--------------------- 1 file changed, 7 insertions(+), 21 deletions(-) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index c610617bb19a..b30a52db6b2d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6587,21 +6587,15 @@ static unsigned long effective_protection(unsigned long usage, * * WARNING: This function is not stateless! It can only be used as part * of a top-down tree iteration, not for isolated queries. - * - * Returns one of the following: - * MEMCG_PROT_NONE: cgroup memory is not protected - * MEMCG_PROT_LOW: cgroup memory is protected as long there is - * an unprotected supply of reclaimable memory from other cgroups. - * MEMCG_PROT_MIN: cgroup memory is protected */ -enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, - struct mem_cgroup *memcg) +void mem_cgroup_calculate_protection(struct mem_cgroup *root, + struct mem_cgroup *memcg) { unsigned long usage, parent_usage; struct mem_cgroup *parent; if (mem_cgroup_disabled()) - return MEMCG_PROT_NONE; + return; if (!root) root = root_mem_cgroup; @@ -6614,21 +6608,21 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, * that special casing. */ if (memcg == root) - return MEMCG_PROT_NONE; + return; usage = page_counter_read(&memcg->memory); if (!usage) - return MEMCG_PROT_NONE; + return; parent = parent_mem_cgroup(memcg); /* No parent means a non-hierarchical mode on v1 memcg */ if (!parent) - return MEMCG_PROT_NONE; + return; if (parent == root) { memcg->memory.emin = READ_ONCE(memcg->memory.min); memcg->memory.elow = READ_ONCE(memcg->memory.low); - goto out; + return; } parent_usage = page_counter_read(&parent->memory); @@ -6642,14 +6636,6 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, READ_ONCE(memcg->memory.low), READ_ONCE(parent->memory.elow), atomic_long_read(&parent->memory.children_low_usage))); - -out: - if (usage <= memcg->memory.emin) - return MEMCG_PROT_MIN; - else if (usage <= memcg->memory.elow) - return MEMCG_PROT_LOW; - else - return MEMCG_PROT_NONE; } /** -- cgit v1.2.3-59-g8ed1b