From eef0f563fd2d16343aa1ac01eebe98126f26e352 Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bvanassche@google.com>
Date: Fri, 29 Jul 2022 12:40:02 -0700
Subject: [PATCH] [DO NOT MERGE] Migrate the blkio controller to the v2 cgroup
 hierarchy

There are multiple use cases in Android for which background writes need
to be controlled via the cgroup mechanism. The cgroup mechanism can only
control background writes if both the blkio and memcg controllers are
mounted in the v2 cgroup hierarchy. Hence this patch that migrates the
blkio controller from the v1 to the v2 cgroup hierarchy.

The blkio controller has been marked as optional since not all Android
kernels enable this controller (CONFIG_BLK_CGROUP).

This patch increases the TOTAL_BOOT_TIME for devices with a 4.19 kernel
(redfin) from 18.9 s to 20 s. This patch does not affect the boot time
for devices with a 5.10 or 5.15 kernel.

This patch increases the time spent in CgroupMap::ActivateControllers()
by 25 microseconds in Cuttlefish on an x86-64 CPU.
CgroupMap::ActivateControllers() is called by Service::Start().

Bug: 213617178
Test: Cuttlefish and various phones
Change-Id: I3c07c1be84c3feb277b7d7003652d5d3b57c6541
Signed-off-by: Bart Van Assche <bvanassche@google.com>
---
 libprocessgroup/profiles/cgroups.json       | 13 ++++-----
 libprocessgroup/profiles/task_profiles.json | 32 ---------------------
 rootdir/init.rc                             | 20 -------------
 3 files changed, 6 insertions(+), 59 deletions(-)

diff --git a/libprocessgroup/profiles/cgroups.json b/libprocessgroup/profiles/cgroups.json
index 3e4393df2..d013ec858 100644
--- a/libprocessgroup/profiles/cgroups.json
+++ b/libprocessgroup/profiles/cgroups.json
@@ -1,12 +1,5 @@
 {
   "Cgroups": [
-    {
-      "Controller": "blkio",
-      "Path": "/dev/blkio",
-      "Mode": "0775",
-      "UID": "system",
-      "GID": "system"
-    },
     {
       "Controller": "cpu",
       "Path": "/dev/cpuctl",
@@ -39,6 +32,12 @@
       {
         "Controller": "freezer",
         "Path": "."
+      },
+      {
+        "Controller": "io",
+        "Path": ".",
+        "NeedsActivation": true,
+        "Optional": true
       }
     ]
   }
diff --git a/libprocessgroup/profiles/task_profiles.json b/libprocessgroup/profiles/task_profiles.json
index e44d3bf72..12f7b4406 100644
--- a/libprocessgroup/profiles/task_profiles.json
+++ b/libprocessgroup/profiles/task_profiles.json
@@ -456,14 +456,6 @@
     {
       "Name": "LowIoPriority",
       "Actions": [
-        {
-          "Name": "JoinCgroup",
-          "Params":
-          {
-            "Controller": "blkio",
-            "Path": "background"
-          }
-        },
         {
           "Name": "SetAttribute",
           "Params":
@@ -496,14 +488,6 @@
     {
       "Name": "NormalIoPriority",
       "Actions": [
-        {
-          "Name": "JoinCgroup",
-          "Params":
-          {
-            "Controller": "blkio",
-            "Path": ""
-          }
-        },
         {
           "Name": "SetAttribute",
           "Params":
@@ -536,14 +520,6 @@
     {
       "Name": "HighIoPriority",
       "Actions": [
-        {
-          "Name": "JoinCgroup",
-          "Params":
-          {
-            "Controller": "blkio",
-            "Path": ""
-          }
-        },
         {
           "Name": "SetAttribute",
           "Params":
@@ -576,14 +552,6 @@
     {
       "Name": "MaxIoPriority",
       "Actions": [
-        {
-          "Name": "JoinCgroup",
-          "Params":
-          {
-            "Controller": "blkio",
-            "Path": ""
-          }
-        },
         {
           "Name": "SetAttribute",
           "Params":
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 68191bb8f..b165778b6 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -221,26 +221,6 @@ on init
     write /dev/stune/nnapi-hal/schedtune.boost 1
     write /dev/stune/nnapi-hal/schedtune.prefer_idle 1
 
-    # Create blkio group and apply initial settings.
-    # This feature needs kernel to support it, and the
-    # device's init.rc must actually set the correct values.
-    mkdir /dev/blkio/background
-    chown system system /dev/blkio
-    chown system system /dev/blkio/background
-    chown system system /dev/blkio/tasks
-    chown system system /dev/blkio/background/tasks
-    chown system system /dev/blkio/cgroup.procs
-    chown system system /dev/blkio/background/cgroup.procs
-    chmod 0664 /dev/blkio/tasks
-    chmod 0664 /dev/blkio/background/tasks
-    chmod 0664 /dev/blkio/cgroup.procs
-    chmod 0664 /dev/blkio/background/cgroup.procs
-    write /dev/blkio/blkio.weight 1000
-    write /dev/blkio/background/blkio.weight 200
-    write /dev/blkio/background/blkio.bfq.weight 10
-    write /dev/blkio/blkio.group_idle 0
-    write /dev/blkio/background/blkio.group_idle 0
-
     restorecon_recursive /mnt
 
     mount configfs none /config nodev noexec nosuid