From: Ben Hutchings <ben@decadent.org.uk>
Date: Thu, 10 Dec 2015 18:02:48 +0000 (+0000)
Subject: cgroups: Allow memory cgroup support to be included but disabled
X-Git-Tag: archive/raspbian/4.9.13-1+rpi1~117
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/%22mailto:kde%40ewsoftware.de//%22style.css/%22/%22http:/www.example.com/%22mailto:kde%40ewsoftware.de/%22style.css/%22?a=commitdiff_plain;h=0a175472568946052ed16468e8b1261d0b731b8c;p=linux-4.9.git

cgroups: Allow memory cgroup support to be included but disabled

Memory cgroup support has some run-time overhead, so it's useful to
include it in a distribution kernel without enabling it by default.
Add a kernel config option to disable it by default and a kernel
parameter 'cgroup_enable' as the opposite to 'cgroup_disable'.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[Bastian Blank: Rename CGROUP_MEM_RES_CTLR_DISABLED to MEMCG_DISABLED]

Gbp-Pq: Topic features/all
Gbp-Pq: Name cgroups-Allow-memory-cgroup-support-to-be-included-b.patch
---

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 742f69d18fc8..30690908c6c8 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -588,8 +588,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	ccw_timeout_log [S390]
 			See Documentation/s390/CommonIO for details.
 
-	cgroup_disable= [KNL] Disable a particular controller
-			Format: {name of the controller(s) to disable}
+	cgroup_disable= [KNL] Disable/enable a particular controller
+	cgroup_enable=	Format: {name of the controller(s) to disable/enable}
 			The effects of cgroup_disable=foo are:
 			- foo isn't auto-mounted if you mount all cgroups in
 			  a single hierarchy
diff --git a/init/Kconfig b/init/Kconfig
index 235c7a2c0d20..d3999071dd4b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1010,6 +1010,14 @@ config MEMCG
 	  Provides a memory resource controller that manages both anonymous
 	  memory and page cache. (See Documentation/cgroups/memory.txt)
 
+config MEMCG_DISABLED
+	bool "Memory Resource Controller disabled by default"
+	depends on MEMCG
+	default n
+	help
+	  Disable the memory group resource controller unless explicitly
+	  enabled using the kernel parameter "cgroup_enable=memory".
+
 config MEMCG_SWAP
 	bool "Memory Resource Controller Swap Extension"
 	depends on MEMCG && SWAP
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index fb1ecfd2decd..8ffdbc1d94e8 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5286,7 +5286,11 @@ int __init cgroup_init_early(void)
 	return 0;
 }
 
+#ifdef CONFIG_MEMCG_DISABLED
+static unsigned long cgroup_disable_mask __initdata = 1 << memory_cgrp_id;
+#else
 static unsigned long cgroup_disable_mask __initdata;
+#endif
 
 /**
  * cgroup_init - cgroup initialization
@@ -5761,7 +5765,7 @@ out_free:
 	kfree(pathbuf);
 }
 
-static int __init cgroup_disable(char *str)
+static int __init cgroup_set_disabled(char *str, int value)
 {
 	struct cgroup_subsys *ss;
 	char *token;
@@ -5775,13 +5779,27 @@ static int __init cgroup_disable(char *str)
 			if (strcmp(token, ss->name) &&
 			    strcmp(token, ss->legacy_name))
 				continue;
-			cgroup_disable_mask |= 1 << i;
+			if (value)
+				cgroup_disable_mask |= 1 << i;
+			else
+				cgroup_disable_mask &= ~(1 << i);
 		}
 	}
 	return 1;
 }
+
+static int __init cgroup_disable(char *str)
+{
+	return cgroup_set_disabled(str, 1);
+}
 __setup("cgroup_disable=", cgroup_disable);
 
+static int __init cgroup_enable(char *str)
+{
+	return cgroup_set_disabled(str, 0);
+}
+__setup("cgroup_enable=", cgroup_enable);
+
 /**
  * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
  * @dentry: directory dentry of interest