Messages in this thread | | | Date | Thu, 19 Jun 2008 09:17:14 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH] cgroup: support checking of subsystem dependencies |
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On Wed, 18 Jun 2008 16:01:49 +0800 Li Zefan <lizf@cn.fujitsu.com> wrote:
> This allows one subsystem to require that it only be mounted when some > other subsystems are also present in the proposed hierarchy. > > For example if subsystem foo depends on bar, the following will fail: > # mount -t cgroup -ofoo xxx /dev/cgroup > > You should mount with both subsystems: > # mount -t cgroup -ofoo,bar xxx /dev/cgroup > I'm just curious. May I ask "Is there such cgroup subsystem now ?"
Thanks, -Kame
> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> > --- > Documentation/cgroups.txt | 6 ++++++ > include/linux/cgroup.h | 2 ++ > kernel/cgroup.c | 30 ++++++++++++++++++++++++++++++ > 3 files changed, 38 insertions(+), 0 deletions(-) > > diff --git a/Documentation/cgroups.txt b/Documentation/cgroups.txt > index 824fc02..8252f5b 100644 > --- a/Documentation/cgroups.txt > +++ b/Documentation/cgroups.txt > @@ -530,6 +530,12 @@ and root cgroup. Currently this will only involve movement between > the default hierarchy (which never has sub-cgroups) and a hierarchy > that is being created/destroyed (and hence has no sub-cgroups). > > +int subsys_depend(struct cgroup_subsys *ss, unsigned long subsys_bits) > + > +Called when a cgroup subsystem wants to check if some other subsystems > +are also present in the proposed hierarchy. If this method returns error, > +the mount of the cgroup filesystem will fail. > + > 4. Questions > ============ > > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index e155aa7..fc99ba4 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -305,6 +305,8 @@ struct cgroup_subsys { > struct cgroup *cgrp); > void (*post_clone)(struct cgroup_subsys *ss, struct cgroup *cgrp); > void (*bind)(struct cgroup_subsys *ss, struct cgroup *root); > + int (*subsys_depend)(struct cgroup_subsys *ss, > + unsigned long subsys_bits); > /* > * This routine is called with the task_lock of mm->owner held > */ > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index 15ac0e1..a4c8671 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c > @@ -837,6 +837,25 @@ static int parse_cgroupfs_options(char *data, > return 0; > } > > +static int check_subsys_dependency(unsigned long subsys_bits) > +{ > + int i; > + int ret; > + struct cgroup_subsys *ss; > + > + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { > + ss = subsys[i]; > + > + if (test_bit(i, &subsys_bits) && ss->subsys_depend) { > + ret = ss->subsys_depend(ss, subsys_bits); > + if (ret) > + return ret; > + } > + } > + > + return 0; > +} > + > static int cgroup_remount(struct super_block *sb, int *flags, char *data) > { > int ret = 0; > @@ -852,6 +871,10 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data) > if (ret) > goto out_unlock; > > + ret = check_subsys_dependency(opts.subsys_bits); > + if (ret) > + goto out_unlock; > + > /* Don't allow flags to change at remount */ > if (opts.flags != root->flags) { > ret = -EINVAL; > @@ -972,6 +995,13 @@ static int cgroup_get_sb(struct file_system_type *fs_type, > return ret; > } > > + ret = check_subsys_dependency(opts.subsys_bits); > + if (ret) { > + if (opts.release_agent) > + kfree(opts.release_agent); > + return ret; > + } > + > root = kzalloc(sizeof(*root), GFP_KERNEL); > if (!root) { > if (opts.release_agent) > -- > 1.5.4.rc3 > > >
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