[PATCH] Add cgroup support for enabling controllers at boot time (v2)

Balbir Singh
2008-03-07T08:59:43Z

From: Paul Menage <menage@google.com>

Changelog v2

1. Add enabled support in /proc/cgroups
2. Add support for parsing of several controller names

The effects of cgroup_disable=foo are:

- foo isn't auto-mounted if you mount all cgroups in a single hierarchy
- foo isn't visible as an individually mountable subsystem

As a result there will only ever be one call to foo->create(), at init
time; all processes will stay in this group, and the group will never
be mounted on a visible hierarchy. Any additional effects (e.g. not
allocating metadata) are up to the foo subsystem.

This doesn't handle early_init subsystems (their "disabled" bit isn't
set be, but it could easily be extended to do so if any of the early_init
systems wanted it - I think it would just involve some nastier parameter
processing since it would occur before the command-line argument parser
had been run.

Signed-off-by: Paul Menage <menage@google.com>
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---

Documentation/kernel-parameters.txt | 4 +++
include/linux/cgroup.h | 1
kernel/cgroup.c | 45 ++++++++++++++++++++++++++++++++----
3 files changed, 45 insertions(+), 5 deletions(-)

diff -puN include/linux/cgroup.h~cgroup_disable include/linux/cgroup.h
--- linux-2.6.25-rc4/include/linux/cgroup.h~cgroup_disable 2008-03-07 14:26:16.000000000 +0530
+++ linux-2.6.25-rc4-balbir/include/linux/cgroup.h 2008-03-07 14:26:16.000000000 +0530
@@ -256,6 +256,7 @@ struct cgroup_subsys {
void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);
int subsys_id;
int active;
+ int disabled;
int early_init;
#define MAX_CGROUP_TYPE_NAMELEN 32
const char *name;
diff -puN kernel/cgroup.c~cgroup_disable kernel/cgroup.c
--- linux-2.6.25-rc4/kernel/cgroup.c~cgroup_disable 2008-03-07 14:26:16.000000000 +0530
+++ linux-2.6.25-rc4-balbir/kernel/cgroup.c 2008-03-07 14:26:16.000000000 +0530
@@ -782,7 +782,14 @@ static int parse_cgroupfs_options(char *
if (!*token)
return -EINVAL;
if (!strcmp(token, "all")) {
- opts->subsys_bits = (1 << CGROUP_SUBSYS_COUNT) - 1;
+ /* Add all non-disabled subsystems */
+ int i;
+ opts->subsys_bits = 0;
+ for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
+ struct cgroup_subsys *ss = subsys[i];
+ if (!ss->disabled)
+ opts->subsys_bits |= 1ul << i;
+ }
} else if (!strcmp(token, "noprefix")) {
set_bit(ROOT_NOPREFIX, &opts->flags);
} else if (!strncmp(token, "release_agent=", 14)) {
@@ -800,7 +807,8 @@ static int parse_cgroupfs_options(char *
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
ss = subsys[i];
if (!strcmp(token, ss->name)) {
- set_bit(i, &opts->subsys_bits);
+ if (!ss->disabled)
+ set_bit(i, &opts->subsys_bits);
break;
}
}
@@ -2600,13 +2608,13 @@ static int proc_cgroupstats_show(struct
{
int i;

- seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\n");
+ seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
mutex_lock(&cgroup_mutex);
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
- seq_printf(m, "%s\t%lu\t%d\n",
+ seq_printf(m, "%s\t%lu\t%d\t%d\n",
ss->name, ss->root->subsys_bits,
- ss->root->number_of_cgroups);
+ ss->root->number_of_cgroups, !ss->disabled);
}
mutex_unlock(&cgroup_mutex);
return 0;
@@ -3010,3 +3018,30 @@ static void cgroup_release_agent(struct
spin_unlock(&release_list_lock);
mutex_unlock(&cgroup_mutex);
}
+
+static int __init cgroup_disable(char *str)
+{
+ int i;
+
+ while (*str) {
+ for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
+ struct cgroup_subsys *ss = subsys[i];
+
+ if (!strncmp(str, ss->name, strlen(ss->name))) {
+ ss->disabled = 1;
+ printk(KERN_INFO "Disabling %s control group"
+ " subsystem\n", ss->name);
+ break;
+ }
+ }
+ /*
+ * Find the next option if any
+ */
+ while (*str && (*str != ','))
+ str++;
+ if (*str == ',')
+ str++;
+ }
+ return 1;
+}
+__setup("cgroup_disable=", cgroup_disable);
diff -puN Documentation/kernel-parameters.txt~cgroup_disable Documentation/kernel-parameters.txt
--- linux-2.6.25-rc4/Documentation/kernel-parameters.txt~cgroup_disable 2008-03-07 14:26:16.000000000 +0530
+++ linux-2.6.25-rc4-balbir/Documentation/kernel-parameters.txt 2008-03-07 14:26:16.000000000 +0530
@@ -383,6 +383,10 @@ and is between 256 and 4096 characters.
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}
+ {Currently supported controllers - "memory"}
+
checkreqprot [SELINUX] Set initial checkreqprot flag value.
Format: { "0" | "1" }
See security/selinux/Kconfig help text.
_

--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL