From 5400ae2440229470362df374b440889ff0810e1b 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] 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.

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: I490740e1c9ee4f7bb5bb7afba721a083f952c8f2
Signed-off-by: Bart Van Assche <bvanassche@google.com>
---
 libprocessgroup/profiles/cgroups.json       | 12 +++++-------
 libprocessgroup/profiles/task_profiles.json | 12 ++++--------
 rootdir/init.rc                             | 20 --------------------
 3 files changed, 9 insertions(+), 35 deletions(-)

diff --git a/libprocessgroup/profiles/cgroups.json b/libprocessgroup/profiles/cgroups.json
index 3e4393df2..23d76ee15 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 +32,11 @@
       {
         "Controller": "freezer",
         "Path": "."
+      },
+      {
+        "Controller": "io",
+        "Path": ".",
+        "NeedsActivation": true
       }
     ]
   }
diff --git a/libprocessgroup/profiles/task_profiles.json b/libprocessgroup/profiles/task_profiles.json
index e44d3bf72..8e784aeb5 100644
--- a/libprocessgroup/profiles/task_profiles.json
+++ b/libprocessgroup/profiles/task_profiles.json
@@ -460,8 +460,7 @@
           "Name": "JoinCgroup",
           "Params":
           {
-            "Controller": "blkio",
-            "Path": "background"
+            "Controller": "io"
           }
         },
         {
@@ -500,8 +499,7 @@
           "Name": "JoinCgroup",
           "Params":
           {
-            "Controller": "blkio",
-            "Path": ""
+            "Controller": "io"
           }
         },
         {
@@ -540,8 +538,7 @@
           "Name": "JoinCgroup",
           "Params":
           {
-            "Controller": "blkio",
-            "Path": ""
+            "Controller": "io"
           }
         },
         {
@@ -580,8 +577,7 @@
           "Name": "JoinCgroup",
           "Params":
           {
-            "Controller": "blkio",
-            "Path": ""
+            "Controller": "io"
           }
         },
         {
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 323d9cb3c..408daff80 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -218,26 +218,6 @@ 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