Add support for memcg v2 attributes

Some but not all memcg v1 attributes exist in the v2 hierarchy. The
following information comes from Shakeel Butt and Kamil Yurtsever,
"cgroup v2 migration at Google", Linux Plumbers Conference 2018
( https://lpc.events/event/2/contributions/204/attachments/143/378/LPC2018-cgroup-v2.pdf ):

         v1                    v2
-------------------------- ----------
memory.limit_in_bytes      memory.max
memory.soft_limit_in_bytes memory.low

Add support for cgroup attributes that have different names in the v1
and v2 hierarchies. Also add those memcg attributes that are used in
lmkd.

Bug: 213617178
Test: Tested lmkd with v1 and v2 memcg.
Change-Id: Ia5c5f02974f3b783d5cdaad85b33169ced8db55f
Signed-off-by: Bart Van Assche <bvanassche@google.com>

libprocessgroup/profiles/task_profiles.json

@@ -15,21 +15,48 @@
       "Controller": "cpuset",
       "File": "top-app/cpus"
     },
+    {
+      "Name": "MemStats",
+      "Controller": "memory",
+      "File": "memory.stat"
+    },
     {
       "Name": "MemLimit",
       "Controller": "memory",
-      "File": "memory.limit_in_bytes"
+      "File": "memory.limit_in_bytes",
+      "FileV2": "memory.max"
     },
     {
       "Name": "MemSoftLimit",
       "Controller": "memory",
-      "File": "memory.soft_limit_in_bytes"
+      "File": "memory.soft_limit_in_bytes",
+      "FileV2": "memory.low"
     },
     {
       "Name": "MemSwappiness",
       "Controller": "memory",
       "File": "memory.swappiness"
     },
+    {
+      "Name": "MemUsage",
+      "Controller": "memory",
+      "File": "memory.usage_in_bytes"
+    },
+    {
+      "Name": "MemAndSwapUsage",
+      "Controller": "memory",
+      "File": "memory.memsw.usage_in_bytes"
+    },
+    {
+      "Name": "MemPressureLevel",
+      "Controller": "memory",
+      "File": "memory.pressure_level"
+    },
+    {
+      "Name": "MemCgroupEventControl",
+      "Controller": "memory",
+      "File": "cgroup.event_control"
+    },
     {
       "Name": "UClampMin",
       "Controller": "cpu",

libprocessgroup/profiles/task_profiles.proto

@@ -25,12 +25,13 @@ message TaskProfiles {
     repeated AggregateProfiles aggregateprofiles = 3 [json_name = "AggregateProfiles"];
 }
 
-// Next: 5
+// Next: 6
 message Attribute {
     string name = 1 [json_name = "Name"];
     string controller = 2 [json_name = "Controller"];
     string file = 3 [json_name = "File"];
-    string optional = 4 [json_name = "Optional"];
+    string filev2 = 4 [json_name = "FileV2"];
+    string optional = 5 [json_name = "Optional"];
 }
 
 // Next: 3

libprocessgroup/task_profiles.cpp

@@ -129,11 +129,12 @@ bool ProfileAttribute::GetPathForTask(int tid, std::string* path) const {
         return true;
     }
 
+    const std::string& file_name =
+            controller()->version() == 2 && !file_v2_name_.empty() ? file_v2_name_ : file_name_;
     if (subgroup.empty()) {
-        *path = StringPrintf("%s/%s", controller()->path(), file_name_.c_str());
+        *path = StringPrintf("%s/%s", controller()->path(), file_name.c_str());
     } else {
-        *path = StringPrintf("%s/%s/%s", controller()->path(), subgroup.c_str(),
-                             file_name_.c_str());
+        *path = StringPrintf("%s/%s/%s", controller()->path(), subgroup.c_str(), file_name.c_str());
     }
     return true;
 }
@@ -633,12 +634,19 @@ bool TaskProfiles::Load(const CgroupMap& cg_map, const std::string& file_name) {
         std::string name = attr[i]["Name"].asString();
         std::string controller_name = attr[i]["Controller"].asString();
         std::string file_attr = attr[i]["File"].asString();
+        std::string file_v2_attr = attr[i]["FileV2"].asString();
+
+        if (!file_v2_attr.empty() && file_attr.empty()) {
+            LOG(ERROR) << "Attribute " << name << " has FileV2 but no File property";
+            return false;
+        }
 
         auto controller = cg_map.FindController(controller_name);
         if (controller.HasValue()) {
             auto iter = attributes_.find(name);
             if (iter == attributes_.end()) {
-                attributes_[name] = std::make_unique<ProfileAttribute>(controller, file_attr);
+                attributes_[name] =
+                        std::make_unique<ProfileAttribute>(controller, file_attr, file_v2_attr);
             } else {
                 iter->second->Reset(controller, file_attr);
             }

libprocessgroup/task_profiles.h

@@ -37,8 +37,12 @@ class IProfileAttribute {
 
 class ProfileAttribute : public IProfileAttribute {
   public:
-    ProfileAttribute(const CgroupController& controller, const std::string& file_name)
-        : controller_(controller), file_name_(file_name) {}
+    // Cgroup attributes may have different names in the v1 and v2 hierarchies. If `file_v2_name` is
+    // not empty, `file_name` is the name for the v1 hierarchy and `file_v2_name` is the name for
+    // the v2 hierarchy. If `file_v2_name` is empty, `file_name` is used for both hierarchies.
+    ProfileAttribute(const CgroupController& controller, const std::string& file_name,
+                     const std::string& file_v2_name)
+        : controller_(controller), file_name_(file_name), file_v2_name_(file_v2_name) {}
     ~ProfileAttribute() = default;
 
     const CgroupController* controller() const override { return &controller_; }
@@ -50,6 +54,7 @@ class ProfileAttribute : public IProfileAttribute {
   private:
     CgroupController controller_;
     std::string file_name_;
+    std::string file_v2_name_;
 };
 
 // Abstract profile element