ns_can_attach (nsproxy cgroup)

ns_can_attach (nsproxy cgroup)

[Grzegorz Nosek]

Hi all,

Is there a good reason for ns_can_attach to restrict moving tasks only
to direct descentants of the current cgroup? I.e. could the code:

        orig = task_cgroup(task, ns_subsys_id);
        if (orig && orig != new_cgroup->parent)
                return -EPERM;

be replaced with:

        orig = task_cgroup(task, ns_subsys_id);
        if (orig && !cgroup_is_descendant_of(new_cgroup, orig))
                return -EPERM;

(for a suitable definition of cgroup_is_descendant_of). It would allow
moving tasks down the cgroup hierarchy more than one level at a time and
as far as I can see, would pose no additional problems.

Please keep CC'd, I'm not subscribed.

Best regards,
 Grzegorz Nosek

Re: ns_can_attach (nsproxy cgroup)

[Serge E. Hallyn]

Quoting Grzegorz Nosek (root-AfQBxy1nhrQ00sYp1HPQUA@public.gmane.org):
> Hi all,
> 
> Is there a good reason for ns_can_attach to restrict moving tasks only
> to direct descentants of the current cgroup? I.e. could the code:
> 
>         orig = task_cgroup(task, ns_subsys_id);
>         if (orig && orig != new_cgroup->parent)
>                 return -EPERM;
> 
> be replaced with:
> 
>         orig = task_cgroup(task, ns_subsys_id);
>         if (orig && !cgroup_is_descendant_of(new_cgroup, orig))
>                 return -EPERM;
> 
> (for a suitable definition of cgroup_is_descendant_of). It would allow
> moving tasks down the cgroup hierarchy more than one level at a time and
> as far as I can see, would pose no additional problems.
> 
> Please keep CC'd, I'm not subscribed.

Well you can always move it down one level at a time, right? :)

But I can't think of any reason why it would be a problem.  So
pls feel free to send a patch.

thanks,
-serge

Re: ns_can_attach (nsproxy cgroup)

[Grzegorz Nosek]

On Fri, Dec 12, 2008 at 08:09:08AM -0600, Serge E. Hallyn wrote:
> Quoting Grzegorz Nosek (root-AfQBxy1nhrQ00sYp1HPQUA@public.gmane.org):
> > Hi all,
> > 
> > Is there a good reason for ns_can_attach to restrict moving tasks only
> > to direct descentants of the current cgroup? I.e. could the code:
> > 
> >         orig = task_cgroup(task, ns_subsys_id);
> >         if (orig && orig != new_cgroup->parent)
> >                 return -EPERM;
> > 
> > be replaced with:
> > 
> >         orig = task_cgroup(task, ns_subsys_id);
> >         if (orig && !cgroup_is_descendant_of(new_cgroup, orig))
> >                 return -EPERM;
> > 
> > (for a suitable definition of cgroup_is_descendant_of). It would allow
> > moving tasks down the cgroup hierarchy more than one level at a time and
> > as far as I can see, would pose no additional problems.
> > 
> > Please keep CC'd, I'm not subscribed.
> 
> Well you can always move it down one level at a time, right? :)

Yeah, but I found a patch by Andrea Righi which fits my use case almost
100% [1]. The tasks are moved between cgroups by the kernel, so it's
kernel hacking for me either way and I guess modifying ns_can_attach
will be cleaner.

> But I can't think of any reason why it would be a problem.  So
> pls feel free to send a patch.

Will do.

Best regards,
 Grzegorz Nosek

[1] http://lwn.net/Articles/294364/

Re: ns_can_attach (nsproxy cgroup)

[Grzegorz Nosek]

On pią, gru 12, 2008 at 08:09:08 -0600, Serge E. Hallyn wrote:
> Quoting Grzegorz Nosek (root@localdomain.pl):
> > Hi all,
> > 
> > Is there a good reason for ns_can_attach to restrict moving tasks only
> > to direct descentants of the current cgroup? I.e. could the code:
> > 
> >         orig = task_cgroup(task, ns_subsys_id);
> >         if (orig && orig != new_cgroup->parent)
> >                 return -EPERM;
> > 
> > be replaced with:
> > 
> >         orig = task_cgroup(task, ns_subsys_id);
> >         if (orig && !cgroup_is_descendant_of(new_cgroup, orig))
> >                 return -EPERM;
> > 
> > (for a suitable definition of cgroup_is_descendant_of). It would allow
> > moving tasks down the cgroup hierarchy more than one level at a time and
> > as far as I can see, would pose no additional problems.
> > 
> > Please keep CC'd, I'm not subscribed.
> 
> Well you can always move it down one level at a time, right? :)
> 
> But I can't think of any reason why it would be a problem.  So
> pls feel free to send a patch.

OK, here's the patch. After some basic testing looks like it's working
as advertised. Please have a look at the patch, esp. the subsys_id part,
I'm not sure I got the code/comments all right.

Best regards,
 Grzegorz Nosek

--------------------------------------
From 8750df0d341c3227a0ed33088602addec003b713 Mon Sep 17 00:00:00 2001
From: Grzegorz Nosek <root@localdomain.pl>
Date: Fri, 12 Dec 2008 21:48:09 +0100
Subject: [PATCH] Relax ns_can_attach checks to allow attaching to grandchild cgroups

The ns_proxy cgroup allows moving processes to child cgroups only one
level deep at a time. This commit relaxes this restriction and makes it
possible to attach tasks directly to grandchild cgroups, e.g.:

($pid is in the root cgroup)
echo $pid > /cgroup/CG1/CG2/tasks

Previously this operation would fail with -EPERM and would have to be
performed as two steps:
echo $pid > /cgroup/CG1/tasks
echo $pid > /cgroup/CG1/CG2/tasks

Signed-off-by: Grzegorz Nosek <root@localdomain.pl>
---
 include/linux/cgroup.h |    5 +++--
 kernel/cgroup.c        |   19 ++++++++++++-------
 kernel/ns_cgroup.c     |    9 +++------
 3 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 1ba3ded..ab8a5cd 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -301,8 +301,9 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
 
 int cgroup_task_count(const struct cgroup *cgrp);
 
-/* Return true if the cgroup is a descendant of the current cgroup */
-int cgroup_is_descendant(const struct cgroup *cgrp);
+/* Return true if cgrp is a descendant of the task's cgroup subsystem subsys_id */
+int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task,
+	int subsys_id);
 
 /* Control Group subsystem type. See Documentation/cgroups.txt for details */
 
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2ae040d..0002fa5 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3101,28 +3101,33 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
 }
 
 /**
- * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
+ * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
  * @cgrp: the cgroup in question
+ * @task: the task in question
+ * @subsys_id: cgroup subsystem id used to determine hierarchy; if negative,
+ * 		use get_first_subsys()
  *
- * See if @cgrp is a descendant of the current task's cgroup in
- * the appropriate hierarchy.
+ * See if @cgrp is a descendant of @task's cgroup in the appropriate
+ * hierarchy.
  *
  * If we are sending in dummytop, then presumably we are creating
  * the top cgroup in the subsystem.
  *
  * Called only by the ns (nsproxy) cgroup.
  */
-int cgroup_is_descendant(const struct cgroup *cgrp)
+int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task,
+	int subsys_id)
 {
 	int ret;
 	struct cgroup *target;
-	int subsys_id;
 
 	if (cgrp == dummytop)
 		return 1;
 
-	get_first_subsys(cgrp, NULL, &subsys_id);
-	target = task_cgroup(current, subsys_id);
+	if (subsys_id < 0)
+		get_first_subsys(cgrp, NULL, &subsys_id);
+
+	target = task_cgroup(task, subsys_id);
 	while (cgrp != target && cgrp!= cgrp->top_cgroup)
 		cgrp = cgrp->parent;
 	ret = (cgrp == target);
diff --git a/kernel/ns_cgroup.c b/kernel/ns_cgroup.c
index 43c2111..5247d84 100644
--- a/kernel/ns_cgroup.c
+++ b/kernel/ns_cgroup.c
@@ -46,21 +46,18 @@ int ns_cgroup_clone(struct task_struct *task, struct pid *pid)
 static int ns_can_attach(struct cgroup_subsys *ss,
 		struct cgroup *new_cgroup, struct task_struct *task)
 {
-	struct cgroup *orig;
-
 	if (current != task) {
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
 
-		if (!cgroup_is_descendant(new_cgroup))
+		if (!cgroup_is_descendant(new_cgroup, current, -1))
 			return -EPERM;
 	}
 
 	if (atomic_read(&new_cgroup->count) != 0)
 		return -EPERM;
 
-	orig = task_cgroup(task, ns_subsys_id);
-	if (orig && orig != new_cgroup->parent)
+	if (!cgroup_is_descendant(new_cgroup, task, ns_subsys_id))
 		return -EPERM;
 
 	return 0;
@@ -78,7 +75,7 @@ static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
 
 	if (!capable(CAP_SYS_ADMIN))
 		return ERR_PTR(-EPERM);
-	if (!cgroup_is_descendant(cgroup))
+	if (!cgroup_is_descendant(cgroup, current, -1))
 		return ERR_PTR(-EPERM);
 
 	ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
-- 
1.5.4.4

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Re: ns_can_attach (nsproxy cgroup)

[Li Zefan]

>  /**
> - * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
> + * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
>   * @cgrp: the cgroup in question
> + * @task: the task in question
> + * @subsys_id: cgroup subsystem id used to determine hierarchy; if negative,
> + * 		use get_first_subsys()

The last argument is redundant.

[...]

> -	orig = task_cgroup(task, ns_subsys_id);
> -	if (orig && orig != new_cgroup->parent)
> +	if (!cgroup_is_descendant(new_cgroup, task, ns_subsys_id))

It makes no difference with:
	if (!cgroup_is_descendant(new_cgroup, task, -1))

That's why we don't need argument 'subsys_id'.

>  		return -EPERM;
>  
>  	return 0;
> @@ -78,7 +75,7 @@ static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
>  
>  	if (!capable(CAP_SYS_ADMIN))
>  		return ERR_PTR(-EPERM);
> -	if (!cgroup_is_descendant(cgroup))
> +	if (!cgroup_is_descendant(cgroup, current, -1))
>  		return ERR_PTR(-EPERM);
>  
>  	ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);

Re: ns_can_attach (nsproxy cgroup)

[Grzegorz Nosek]

On sob, gru 13, 2008 at 03:03:52 +0800, Li Zefan wrote:
> >  /**
> > - * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
> > + * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
> >   * @cgrp: the cgroup in question
> > + * @task: the task in question
> > + * @subsys_id: cgroup subsystem id used to determine hierarchy; if negative,
> > + * 		use get_first_subsys()
> 
> The last argument is redundant.
> 
> [...]
> 
> It makes no difference with:
> 	if (!cgroup_is_descendant(new_cgroup, task, -1))
> 
> That's why we don't need argument 'subsys_id'.

Thanks, I thought so (the "first" subsys_id looked arbitrary to me) but not knowing
the cgroup internals I wanted to preserve the original code as much as possible.
Will update the patch.

Best regards,
 Grzegorz Nosek

Re: ns_can_attach (nsproxy cgroup)

[Grzegorz Nosek]

On nie, gru 14, 2008 at 03:06:04 +0100, Grzegorz Nosek wrote:
> On sob, gru 13, 2008 at 03:03:52 +0800, Li Zefan wrote:
> > >  /**
> > > - * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
> > > + * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
> > >   * @cgrp: the cgroup in question
> > > + * @task: the task in question
> > > + * @subsys_id: cgroup subsystem id used to determine hierarchy; if negative,
> > > + * 		use get_first_subsys()
> > 
> > The last argument is redundant.
> > 
> > [...]
> > 
> > It makes no difference with:
> > 	if (!cgroup_is_descendant(new_cgroup, task, -1))
> > 
> > That's why we don't need argument 'subsys_id'.
> 
> Thanks, I thought so (the "first" subsys_id looked arbitrary to me) but not knowing
> the cgroup internals I wanted to preserve the original code as much as possible.
> Will update the patch.

As promised, here's the updated patch.

From 2abb608222f3dfd1c5da3022a75c824f2b00b3f5 Mon Sep 17 00:00:00 2001
From: Grzegorz Nosek <root-AfQBxy1nhrQ00sYp1HPQUA@public.gmane.org>
Date: Fri, 12 Dec 2008 21:48:09 +0100
Subject: [PATCH] Relax ns_can_attach checks to allow attaching to grandchild cgroups

The ns_proxy cgroup allows moving processes to child cgroups only one
level deep at a time. This commit relaxes this restriction and makes it
possible to attach tasks directly to grandchild cgroups, e.g.:

($pid is in the root cgroup)
echo $pid > /cgroup/CG1/CG2/tasks

Previously this operation would fail with -EPERM and would have to be
performed as two steps:
echo $pid > /cgroup/CG1/tasks
echo $pid > /cgroup/CG1/CG2/tasks

Signed-off-by: Grzegorz Nosek <root-AfQBxy1nhrQ00sYp1HPQUA@public.gmane.org>
---
 include/linux/cgroup.h |    4 ++--
 kernel/cgroup.c        |   12 +++++++-----
 kernel/ns_cgroup.c     |    9 +++------
 3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 1ba3ded..53188f5 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -301,8 +301,8 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
 
 int cgroup_task_count(const struct cgroup *cgrp);
 
-/* Return true if the cgroup is a descendant of the current cgroup */
-int cgroup_is_descendant(const struct cgroup *cgrp);
+/* Return true if cgrp is a descendant of the task's cgroup */
+int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);
 
 /* Control Group subsystem type. See Documentation/cgroups.txt for details */
 
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2ae040d..5512d78 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3101,18 +3101,19 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
 }
 
 /**
- * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
+ * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
  * @cgrp: the cgroup in question
+ * @task: the task in question
  *
- * See if @cgrp is a descendant of the current task's cgroup in
- * the appropriate hierarchy.
+ * See if @cgrp is a descendant of @task's cgroup in the appropriate
+ * hierarchy.
  *
  * If we are sending in dummytop, then presumably we are creating
  * the top cgroup in the subsystem.
  *
  * Called only by the ns (nsproxy) cgroup.
  */
-int cgroup_is_descendant(const struct cgroup *cgrp)
+int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
 {
 	int ret;
 	struct cgroup *target;
@@ -3122,7 +3123,8 @@ int cgroup_is_descendant(const struct cgroup *cgrp)
 		return 1;
 
 	get_first_subsys(cgrp, NULL, &subsys_id);
-	target = task_cgroup(current, subsys_id);
+	target = task_cgroup(task, subsys_id);
+
 	while (cgrp != target && cgrp!= cgrp->top_cgroup)
 		cgrp = cgrp->parent;
 	ret = (cgrp == target);
diff --git a/kernel/ns_cgroup.c b/kernel/ns_cgroup.c
index 43c2111..d99b4cc 100644
--- a/kernel/ns_cgroup.c
+++ b/kernel/ns_cgroup.c
@@ -46,21 +46,18 @@ int ns_cgroup_clone(struct task_struct *task, struct pid *pid)
 static int ns_can_attach(struct cgroup_subsys *ss,
 		struct cgroup *new_cgroup, struct task_struct *task)
 {
-	struct cgroup *orig;
-
 	if (current != task) {
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
 
-		if (!cgroup_is_descendant(new_cgroup))
+		if (!cgroup_is_descendant(new_cgroup, current))
 			return -EPERM;
 	}
 
 	if (atomic_read(&new_cgroup->count) != 0)
 		return -EPERM;
 
-	orig = task_cgroup(task, ns_subsys_id);
-	if (orig && orig != new_cgroup->parent)
+	if (!cgroup_is_descendant(new_cgroup, task))
 		return -EPERM;
 
 	return 0;
@@ -78,7 +75,7 @@ static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
 
 	if (!capable(CAP_SYS_ADMIN))
 		return ERR_PTR(-EPERM);
-	if (!cgroup_is_descendant(cgroup))
+	if (!cgroup_is_descendant(cgroup, current))
 		return ERR_PTR(-EPERM);
 
 	ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
-- 
1.5.4.4

Re: ns_can_attach (nsproxy cgroup)

[Li Zefan]

>>From 2abb608222f3dfd1c5da3022a75c824f2b00b3f5 Mon Sep 17 00:00:00 2001
> From: Grzegorz Nosek <root-AfQBxy1nhrQ00sYp1HPQUA@public.gmane.org>
> Date: Fri, 12 Dec 2008 21:48:09 +0100
> Subject: [PATCH] Relax ns_can_attach checks to allow attaching to grandchild cgroups
> 
> The ns_proxy cgroup allows moving processes to child cgroups only one
> level deep at a time. This commit relaxes this restriction and makes it
> possible to attach tasks directly to grandchild cgroups, e.g.:
> 
> ($pid is in the root cgroup)
> echo $pid > /cgroup/CG1/CG2/tasks
> 
> Previously this operation would fail with -EPERM and would have to be
> performed as two steps:
> echo $pid > /cgroup/CG1/tasks
> echo $pid > /cgroup/CG1/CG2/tasks
> 

Now looks good to me. :)

Reviewed-by: Li Zefan <lizf-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>

> Signed-off-by: Grzegorz Nosek <root-AfQBxy1nhrQ00sYp1HPQUA@public.gmane.org>
> ---
>  include/linux/cgroup.h |    4 ++--
>  kernel/cgroup.c        |   12 +++++++-----
>  kernel/ns_cgroup.c     |    9 +++------
>  3 files changed, 12 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index 1ba3ded..53188f5 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -301,8 +301,8 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
>  
>  int cgroup_task_count(const struct cgroup *cgrp);
>  
> -/* Return true if the cgroup is a descendant of the current cgroup */
> -int cgroup_is_descendant(const struct cgroup *cgrp);
> +/* Return true if cgrp is a descendant of the task's cgroup */
> +int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);
>  
>  /* Control Group subsystem type. See Documentation/cgroups.txt for details */
>  
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 2ae040d..5512d78 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -3101,18 +3101,19 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
>  }
>  
>  /**
> - * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
> + * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
>   * @cgrp: the cgroup in question
> + * @task: the task in question
>   *
> - * See if @cgrp is a descendant of the current task's cgroup in
> - * the appropriate hierarchy.
> + * See if @cgrp is a descendant of @task's cgroup in the appropriate
> + * hierarchy.
>   *
>   * If we are sending in dummytop, then presumably we are creating
>   * the top cgroup in the subsystem.
>   *
>   * Called only by the ns (nsproxy) cgroup.
>   */
> -int cgroup_is_descendant(const struct cgroup *cgrp)
> +int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
>  {
>  	int ret;
>  	struct cgroup *target;
> @@ -3122,7 +3123,8 @@ int cgroup_is_descendant(const struct cgroup *cgrp)
>  		return 1;
>  
>  	get_first_subsys(cgrp, NULL, &subsys_id);
> -	target = task_cgroup(current, subsys_id);
> +	target = task_cgroup(task, subsys_id);
> +
>  	while (cgrp != target && cgrp!= cgrp->top_cgroup)
>  		cgrp = cgrp->parent;
>  	ret = (cgrp == target);
> diff --git a/kernel/ns_cgroup.c b/kernel/ns_cgroup.c
> index 43c2111..d99b4cc 100644
> --- a/kernel/ns_cgroup.c
> +++ b/kernel/ns_cgroup.c
> @@ -46,21 +46,18 @@ int ns_cgroup_clone(struct task_struct *task, struct pid *pid)
>  static int ns_can_attach(struct cgroup_subsys *ss,
>  		struct cgroup *new_cgroup, struct task_struct *task)
>  {
> -	struct cgroup *orig;
> -
>  	if (current != task) {
>  		if (!capable(CAP_SYS_ADMIN))
>  			return -EPERM;
>  
> -		if (!cgroup_is_descendant(new_cgroup))
> +		if (!cgroup_is_descendant(new_cgroup, current))
>  			return -EPERM;
>  	}
>  
>  	if (atomic_read(&new_cgroup->count) != 0)
>  		return -EPERM;
>  
> -	orig = task_cgroup(task, ns_subsys_id);
> -	if (orig && orig != new_cgroup->parent)
> +	if (!cgroup_is_descendant(new_cgroup, task))
>  		return -EPERM;
>  
>  	return 0;
> @@ -78,7 +75,7 @@ static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
>  
>  	if (!capable(CAP_SYS_ADMIN))
>  		return ERR_PTR(-EPERM);
> -	if (!cgroup_is_descendant(cgroup))
> +	if (!cgroup_is_descendant(cgroup, current))
>  		return ERR_PTR(-EPERM);
>  
>  	ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);

Re: ns_can_attach (nsproxy cgroup)

[Grzegorz Nosek]

On śro, gru 17, 2008 at 08:52:03 +0800, Li Zefan wrote:
> >>From 2abb608222f3dfd1c5da3022a75c824f2b00b3f5 Mon Sep 17 00:00:00 2001
> > From: Grzegorz Nosek <root@localdomain.pl>
> > Date: Fri, 12 Dec 2008 21:48:09 +0100
> > Subject: [PATCH] Relax ns_can_attach checks to allow attaching to grandchild cgroups
> > 
> > The ns_proxy cgroup allows moving processes to child cgroups only one
> > level deep at a time. This commit relaxes this restriction and makes it
> > possible to attach tasks directly to grandchild cgroups, e.g.:
> > 
> > ($pid is in the root cgroup)
> > echo $pid > /cgroup/CG1/CG2/tasks
> > 
> > Previously this operation would fail with -EPERM and would have to be
> > performed as two steps:
> > echo $pid > /cgroup/CG1/tasks
> > echo $pid > /cgroup/CG1/CG2/tasks
> > 
> 
> Now looks good to me. :)
> 
> Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>

Thanks, shall I send the patch somewhere else for some mainstream tree
inclusion or is somebody willing to pick it up from here?

Best regards,
 Grzegorz Nosek
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Re: ns_can_attach (nsproxy cgroup)

[Li Zefan]

>> Now looks good to me. :)
>>
>> Reviewed-by: Li Zefan <lizf-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> 
> Thanks, shall I send the patch somewhere else for some mainstream tree
> inclusion or is somebody willing to pick it up from here?
> 

You can resend this patch to Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
and CC Paul Menage <menage-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> since the patch touches cgroup.c,
and feel free to add my reviewed tag. :)

> Best regards,
>  Grzegorz Nosek
> 
>