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Date: Fri, 07 Mar 2008 09:13:46 +0900
From: Li Zefan <lizf@...fujitsu.com>
To: Balbir Singh <balbir@...ux.vnet.ibm.com>
CC: Paul Menage <menage@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Pavel Emelianov <xemul@...nvz.org>,
Hugh Dickins <hugh@...itas.com>,
Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
YAMAMOTO Takashi <yamamoto@...inux.co.jp>,
linux-kernel@...r.kernel.org, taka@...inux.co.jp,
linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] Add cgroup support for enabling controllers at boot time
Balbir Singh wrote:
> From: Paul Menage <menage@...gle.com>
>
> The effects of cgroup_disable=foo are:
>
> - foo doesn't show up in /proc/cgroups
> - 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.
>
> [Balbir added Documentation/kernel-parameters updates]
>
> Signed-off-by: Paul Menage <menage@...gle.com>
> Signed-off-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
> ---
>
> Documentation/kernel-parameters.txt | 4 ++++
> include/linux/cgroup.h | 1 +
> kernel/cgroup.c | 27 +++++++++++++++++++++++++--
> 3 files changed, 30 insertions(+), 2 deletions(-)
>
> diff -puN include/linux/cgroup.h~cgroup_disable include/linux/cgroup.h
> --- linux-2.6.25-rc4/include/linux/cgroup.h~cgroup_disable 2008-03-06 12:19:38.000000000 +0530
> +++ linux-2.6.25-rc4-balbir/include/linux/cgroup.h 2008-03-06 12:19:38.000000000 +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 2008-03-06 12:19:38.000000000 +0530
> +++ linux-2.6.25-rc4-balbir/kernel/cgroup.c 2008-03-06 12:19:38.000000000 +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;
> }
> }
> @@ -2604,6 +2612,8 @@ static int proc_cgroupstats_show(struct
> mutex_lock(&cgroup_mutex);
> for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
> struct cgroup_subsys *ss = subsys[i];
> + if (ss->disabled)
> + continue;
> seq_printf(m, "%s\t%lu\t%d\n",
> ss->name, ss->root->subsys_bits,
> ss->root->number_of_cgroups);
> @@ -3010,3 +3020,16 @@ static void cgroup_release_agent(struct
> spin_unlock(&release_list_lock);
> mutex_unlock(&cgroup_mutex);
> }
> +
> +static int __init cgroup_disable(char *str)
> +{
> + int i;
> + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
> + struct cgroup_subsys *ss = subsys[i];
> + if (!strcmp(str, ss->name)) {
> + ss->disabled = 1;
> + break;
> + }
> + }
> +}
> +__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 2008-03-06 17:57:32.000000000 +0530
> +++ linux-2.6.25-rc4-balbir/Documentation/kernel-parameters.txt 2008-03-06 18:00:32.000000000 +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] Enable disable a particular controller
> + Format: {name of the controller}
> + See /proc/cgroups for a list of compiled controllers
> +
The changelog of this patch:
- foo doesn't show up in /proc/cgroups
So a disabled subsystem won't show up in /proc/cgroups. In a previous
mail, I asked whether it will be useful to print out the disable bit
in /proc/cgroups, so we can distinguish a subsystem from disaled and
not-compiled.
> checkreqprot [SELINUX] Set initial checkreqprot flag value.
> Format: { "0" | "1" }
> See security/selinux/Kconfig help text.
> _
>
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