Merge "libprocessgroup: Remove PRODUCT_MEMCG_V2_FORCE_ENABLED" into main
diff --git a/libprocessgroup/Android.bp b/libprocessgroup/Android.bp
index 1e76e76..6725acc 100644
--- a/libprocessgroup/Android.bp
+++ b/libprocessgroup/Android.bp
@@ -7,7 +7,6 @@
     module_type: "cc_defaults",
     config_namespace: "ANDROID",
     bool_variables: [
-        "memcg_v2_force_enabled",
         "cgroup_v2_sys_app_isolation",
     ],
     properties: [
@@ -19,11 +18,6 @@
     name: "libprocessgroup_build_flags_cc",
     cpp_std: "gnu++23",
     soong_config_variables: {
-        memcg_v2_force_enabled: {
-            cflags: [
-                "-DMEMCG_V2_FORCE_ENABLED=true",
-            ],
-        },
         cgroup_v2_sys_app_isolation: {
             cflags: [
                 "-DCGROUP_V2_SYS_APP_ISOLATION=true",
diff --git a/libprocessgroup/build_flags.h b/libprocessgroup/build_flags.h
index bc3e7df..d0948c3 100644
--- a/libprocessgroup/build_flags.h
+++ b/libprocessgroup/build_flags.h
@@ -16,20 +16,12 @@
 
 #pragma once
 
-#ifndef MEMCG_V2_FORCE_ENABLED
-#define MEMCG_V2_FORCE_ENABLED false
-#endif
-
 #ifndef CGROUP_V2_SYS_APP_ISOLATION
 #define CGROUP_V2_SYS_APP_ISOLATION false
 #endif
 
 namespace android::libprocessgroup_flags {
 
-inline consteval bool force_memcg_v2() {
-    return MEMCG_V2_FORCE_ENABLED;
-}
-
 inline consteval bool cgroup_v2_sys_app_isolation() {
     return CGROUP_V2_SYS_APP_ISOLATION;
 }
diff --git a/libprocessgroup/setup/cgroup_map_write.cpp b/libprocessgroup/setup/cgroup_map_write.cpp
index c4e1fb6..0d1739e 100644
--- a/libprocessgroup/setup/cgroup_map_write.cpp
+++ b/libprocessgroup/setup/cgroup_map_write.cpp
@@ -27,9 +27,6 @@
 #include <sys/types.h>
 #include <unistd.h>
 
-#include <optional>
-
-#include <android-base/file.h>
 #include <android-base/logging.h>
 #include <processgroup/cgroup_descriptor.h>
 #include <processgroup/processgroup.h>
@@ -260,39 +257,6 @@
     controller_.set_flags(flags);
 }
 
-static std::optional<bool> MGLRUDisabled() {
-    const std::string file_name = "/sys/kernel/mm/lru_gen/enabled";
-    std::string content;
-    if (!android::base::ReadFileToString(file_name, &content)) {
-        PLOG(ERROR) << "Failed to read MGLRU state from " << file_name;
-        return {};
-    }
-
-    return content == "0x0000";
-}
-
-static std::optional<bool> MEMCGDisabled(const CgroupDescriptorMap& descriptors) {
-    std::string cgroup_v2_root = CGROUP_V2_ROOT_DEFAULT;
-    const auto it = descriptors.find(CGROUPV2_HIERARCHY_NAME);
-    if (it == descriptors.end()) {
-        LOG(WARNING) << "No Cgroups2 path found in cgroups.json. Vendor has modified Android, and "
-                     << "kernel memory use will be higher than intended.";
-    } else if (it->second.controller()->path() != cgroup_v2_root) {
-        cgroup_v2_root = it->second.controller()->path();
-    }
-
-    const std::string file_name = cgroup_v2_root + "/cgroup.controllers";
-    std::string content;
-    if (!android::base::ReadFileToString(file_name, &content)) {
-        PLOG(ERROR) << "Failed to read cgroup controllers from " << file_name;
-        return {};
-    }
-
-    // If we've forced memcg to v2 and it's not available, then it could only have been disabled
-    // on the kernel command line (GKI sets CONFIG_MEMCG).
-    return content.find("memory") == std::string::npos;
-}
-
 static bool CreateV2SubHierarchy(const std::string& path, const CgroupDescriptorMap& descriptors) {
     const auto cgv2_iter = descriptors.find(CGROUPV2_HIERARCHY_NAME);
     if (cgv2_iter == descriptors.end()) return false;
@@ -335,17 +299,6 @@
         }
     }
 
-    if (android::libprocessgroup_flags::force_memcg_v2()) {
-        if (MGLRUDisabled().value_or(false)) {
-            LOG(WARNING) << "Memcg forced to v2 hierarchy with MGLRU disabled! "
-                         << "Global reclaim performance will suffer.";
-        }
-        if (MEMCGDisabled(descriptors).value_or(false)) {
-            LOG(WARNING) << "Memcg forced to v2 hierarchy while memcg is disabled by kernel "
-                         << "command line!";
-        }
-    }
-
     // System / app isolation.
     // This really belongs in early-init in init.rc, but we cannot use the flag there.
     if (android::libprocessgroup_flags::cgroup_v2_sys_app_isolation()) {
diff --git a/libprocessgroup/util/Android.bp b/libprocessgroup/util/Android.bp
index 1c74d4e..266a53f 100644
--- a/libprocessgroup/util/Android.bp
+++ b/libprocessgroup/util/Android.bp
@@ -21,6 +21,7 @@
 
 cc_library_static {
     name: "libprocessgroup_util",
+    cpp_std: "gnu++23",
     vendor_available: true,
     product_available: true,
     ramdisk_available: true,
@@ -47,7 +48,6 @@
     static_libs: [
         "libjsoncpp",
     ],
-    defaults: ["libprocessgroup_build_flags_cc"],
 }
 
 cc_test {
diff --git a/libprocessgroup/util/util.cpp b/libprocessgroup/util/util.cpp
index 1401675..c772bc5 100644
--- a/libprocessgroup/util/util.cpp
+++ b/libprocessgroup/util/util.cpp
@@ -111,7 +111,6 @@
 }
 
 bool ReadDescriptorsFromFile(const std::string& file_name, CgroupDescriptorMap* descriptors) {
-    static constexpr bool force_memcg_v2 = android::libprocessgroup_flags::force_memcg_v2();
     std::vector<CgroupDescriptor> result;
     std::string json_doc;
 
@@ -133,14 +132,10 @@
         const Json::Value& cgroups = root["Cgroups"];
         for (Json::Value::ArrayIndex i = 0; i < cgroups.size(); ++i) {
             std::string name = cgroups[i]["Controller"].asString();
-
-            if (force_memcg_v2 && name == "memory") continue;
-
             MergeCgroupToDescriptors(descriptors, cgroups[i], name, "", 1);
         }
     }
 
-    bool memcgv2_present = false;
     std::string root_path;
     if (root.isMember("Cgroups2")) {
         const Json::Value& cgroups2 = root["Cgroups2"];
@@ -150,24 +145,10 @@
         const Json::Value& childGroups = cgroups2["Controllers"];
         for (Json::Value::ArrayIndex i = 0; i < childGroups.size(); ++i) {
             std::string name = childGroups[i]["Controller"].asString();
-
-            if (force_memcg_v2 && name == "memory") memcgv2_present = true;
-
             MergeCgroupToDescriptors(descriptors, childGroups[i], name, root_path, 2);
         }
     }
 
-    if (force_memcg_v2 && !memcgv2_present) {
-        LOG(INFO) << "Forcing memcg to v2 hierarchy";
-        Json::Value memcgv2;
-        memcgv2["Controller"] = "memory";
-        memcgv2["NeedsActivation"] = true;
-        memcgv2["Path"] = ".";
-        memcgv2["Optional"] = true;  // In case of cgroup_disabled=memory, so we can still boot
-        MergeCgroupToDescriptors(descriptors, memcgv2, "memory",
-                                 root_path.empty() ? CGROUP_V2_ROOT_DEFAULT : root_path, 2);
-    }
-
     return true;
 }