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 742f69d18fc8989ae28d9c0662d6bf334109dddd..30690908c6c8d6707c6f918f5d1797da096c3ef0 100644 (file)
--- 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 235c7a2c0d2004f1121b7d98f4140683ab45ef53..d3999071dd4be413b2b8dd9d29e34b972c7b13e2 100644 (file)
--- 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 fb1ecfd2decd907e907d1d68d74792cb6d07714e..8ffdbc1d94e8fa08975ff3c4b8872ccd210a18b5 100644 (file)
--- 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