[Devel] [PATCH RHEL7 COMMIT] memcg: add function to get container's ram size

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-123.1.2-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-123.1.2.vz7.5.7
------>
commit a67159e9a53cc3328df60c472c3cbb850c6a5fbb
Author: Vladimir Davydov <vdavydov at parallels.com>
Date:   Fri May 29 12:35:45 2015 +0400

    memcg: add function to get container's ram size
    
    Sometimes we need to get the ram size of the container the current
    process belongs to and we cannot open the memory cgroup by name as we
    usually do (e.g. see ub_dirty_limits). This patch adds a function for
    this purpose, mem_cgroup_ram_pages.
    
    In this function we implicitly assume that each container lives in its
    own top level memory cgroup. If it is changed (e.g. we move all
    containers to /machine.slice), then we must rework this function (as
    well as all the code in beancounters that gets stats from memcg). One
    way to do that is allow the userspace assign a memory cgroup to a ve or
    beancounter cgroup and get the memory cgroup of a container from
    get_exec_env() or get_exec_ub().
    
    Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
    Reviewed-by: Kirill Tkhai <ktkhai at odin.com>
---
 include/linux/memcontrol.h |  6 ++++++
 mm/memcontrol.c            | 31 +++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 661e60c..d434d6c 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -127,6 +127,7 @@ extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
 					struct task_struct *p);
 extern void mem_cgroup_replace_page_cache(struct page *oldpage,
 					struct page *newpage);
+unsigned long mem_cgroup_ram_pages(void);
 
 #ifdef CONFIG_MEMCG_SWAP
 extern int do_swap_account;
@@ -400,6 +401,11 @@ static inline void mem_cgroup_replace_page_cache(struct page *oldpage,
 				struct page *newpage)
 {
 }
+
+static inline unsigned long mem_cgroup_ram_pages(void)
+{
+	return ULONG_MAX;
+}
 #endif /* CONFIG_MEMCG */
 
 #if !defined(CONFIG_MEMCG) || !defined(CONFIG_DEBUG_VM)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ed76b71..6409fb2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1630,6 +1630,37 @@ void mem_cgroup_note_oom_kill(struct mem_cgroup *root_memcg,
 		css_put(&memcg_to_put->css);
 }
 
+/*
+ * XXX: This function returns the limit of the topmost memory cgroup the
+ * current process belongs to (ULONG_MAX if unlimited). It is used to get the
+ * number of memory pages available to a Virtuozzo container. Here we
+ * implicitly assume that each container lives in its own top level memory
+ * cgroup. If it is changed, this function must be reworked. E.g. we could
+ * assign a memory cgroup to each ve or beancounter cgroup and get the memory
+ * cgroup of a container from get_exec_env() or get_exec_ub().
+ */
+unsigned long mem_cgroup_ram_pages(void)
+{
+	struct mem_cgroup *memcg_to_put, *memcg, *parent;
+	unsigned long long limit = RESOURCE_MAX;
+
+	memcg_to_put = memcg = try_get_mem_cgroup_from_mm(current->mm);
+	if (!memcg || memcg == root_mem_cgroup)
+		goto out;
+
+	while ((parent = parent_mem_cgroup(memcg)) &&
+	       parent != root_mem_cgroup)
+		memcg = parent;
+
+	limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
+out:
+	if (memcg_to_put)
+		css_put(&memcg_to_put->css);
+	if (limit == RESOURCE_MAX)
+		return ULONG_MAX;
+	return min_t(unsigned long long, ULONG_MAX, limit >> PAGE_SHIFT);
+}
+
 #define mem_cgroup_from_res_counter(counter, member)	\
 	container_of(counter, struct mem_cgroup, member)