[PATCH 1/7] netcls_cgroup: move config inheritance to ->css_online() and remove .broken_hierarchy marking

[PATCH 1/7] netcls_cgroup: move config inheritance to ->css_online() and remove .broken_hierarchy marking

[Tejun Heo]

It turns out that we'll have to live with attributes which are
inherited at cgroup creation time but not affected by further updates
to the parent afterwards - such attributes are already in wide use
e.g. for cpuset.

So, there's nothing to do for netcls_cgroup for hierarchy support.
Its current behavior - inherit only during creation - is good enough.

Move config inheriting from ->css_alloc() to ->css_online() for
consistency, which doesn't change behavior at all, and remove
.broken_hierarchy marking.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 net/sched/cls_cgroup.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index 8cdc18e..31f06b6 100644
--- a/net/sched/cls_cgroup.c
+++ b/net/sched/cls_cgroup.c
@@ -41,11 +41,15 @@ static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
 	cs = kzalloc(sizeof(*cs), GFP_KERNEL);
 	if (!cs)
 		return ERR_PTR(-ENOMEM);
+	return &cs->css;
+}
 
+static int cgrp_css_online(struct cgroup *cgrp)
+{
 	if (cgrp->parent)
-		cs->classid = cgrp_cls_state(cgrp->parent)->classid;
-
-	return &cs->css;
+		cgrp_cls_state(cgrp)->classid =
+			cgrp_cls_state(cgrp->parent)->classid;
+	return 0;
 }
 
 static void cgrp_css_free(struct cgroup *cgrp)
@@ -76,19 +80,11 @@ static struct cftype ss_files[] = {
 struct cgroup_subsys net_cls_subsys = {
 	.name		= "net_cls",
 	.css_alloc	= cgrp_css_alloc,
+	.css_online	= cgrp_css_online,
 	.css_free	= cgrp_css_free,
 	.subsys_id	= net_cls_subsys_id,
 	.base_cftypes	= ss_files,
 	.module		= THIS_MODULE,
-
-	/*
-	 * While net_cls cgroup has the rudimentary hierarchy support of
-	 * inheriting the parent's classid on cgroup creation, it doesn't
-	 * properly propagates config changes in ancestors to their
-	 * descendents.  A child should follow the parent's configuration
-	 * but be allowed to override it.  Fix it and remove the following.
-	 */
-	.broken_hierarchy = true,
 };
 
 struct cls_cgroup_head {
-- 
1.7.11.7

Re: [PATCH 1/7] netcls_cgroup: move config inheritance to ->css_online() and remove .broken_hierarchy marking

[Daniel Wagner]

On 20.11.2012 09:30, Tejun Heo wrote:
> It turns out that we'll have to live with attributes which are
> inherited at cgroup creation time but not affected by further updates
> to the parent afterwards - such attributes are already in wide use
> e.g. for cpuset.
>
> So, there's nothing to do for netcls_cgroup for hierarchy support.
> Its current behavior - inherit only during creation - is good enough.
>
> Move config inheriting from ->css_alloc() to ->css_online() for
> consistency, which doesn't change behavior at all, and remove
> .broken_hierarchy marking.
>
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

Not introducing the 'is_local' is a good thing.

Tested and Acked-by: Daniel Wagner <daniel.wagner-98C5kh4wR6ohFhg+JK9F0w@public.gmane.org>

[PATCH 2/7] netprio_cgroup: simplify write_priomap()

[Tejun Heo]

sscanf() doesn't bite.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>
---
 net/core/netprio_cgroup.c | 56 ++++++++++-------------------------------------
 1 file changed, 11 insertions(+), 45 deletions(-)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index f0b6b0d..66d98da 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -176,66 +176,32 @@ static int read_priomap(struct cgroup *cont, struct cftype *cft,
 static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
 			 const char *buffer)
 {
-	char *devname = kstrdup(buffer, GFP_KERNEL);
-	int ret = -EINVAL;
 	u32 prioidx = cgrp_netprio_state(cgrp)->prioidx;
-	unsigned long priority;
-	char *priostr;
+	char devname[IFNAMSIZ + 1];
 	struct net_device *dev;
 	struct netprio_map *map;
+	u32 prio;
+	int ret;
 
-	if (!devname)
-		return -ENOMEM;
-
-	/*
-	 * Minimally sized valid priomap string
-	 */
-	if (strlen(devname) < 3)
-		goto out_free_devname;
-
-	priostr = strstr(devname, " ");
-	if (!priostr)
-		goto out_free_devname;
-
-	/*
-	 *Separate the devname from the associated priority
-	 *and advance the priostr pointer to the priority value
-	 */
-	*priostr = '\0';
-	priostr++;
-
-	/*
-	 * If the priostr points to NULL, we're at the end of the passed
-	 * in string, and its not a valid write
-	 */
-	if (*priostr == '\0')
-		goto out_free_devname;
-
-	ret = kstrtoul(priostr, 10, &priority);
-	if (ret < 0)
-		goto out_free_devname;
-
-	ret = -ENODEV;
+	if (sscanf(buffer, "%"__stringify(IFNAMSIZ)"s %u", devname, &prio) != 2)
+		return -EINVAL;
 
 	dev = dev_get_by_name(&init_net, devname);
 	if (!dev)
-		goto out_free_devname;
+		return -ENODEV;
 
 	rtnl_lock();
+
 	ret = write_update_netdev_table(dev);
-	if (ret < 0)
-		goto out_put_dev;
+	if (ret)
+		goto out_unlock;
 
 	map = rtnl_dereference(dev->priomap);
 	if (map)
-		map->priomap[prioidx] = priority;
-
-out_put_dev:
+		map->priomap[prioidx] = prio;
+out_unlock:
 	rtnl_unlock();
 	dev_put(dev);
-
-out_free_devname:
-	kfree(devname);
 	return ret;
 }
 
-- 
1.7.11.7

Re: [PATCH 2/7] netprio_cgroup: simplify write_priomap()

[Daniel Wagner]

On 20.11.2012 09:30, Tejun Heo wrote:
> sscanf() doesn't bite.
>
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>

Tested and Acked-by: Daniel Wagner <daniel.wagner-98C5kh4wR6ohFhg+JK9F0w@public.gmane.org>

[PATCH 3/7] netprio_cgroup: shorten variable names in extend_netdev_table()

[Tejun Heo]

The function is about to go through a rewrite.  In preparation,
shorten the variable names so that we don't repeat "priomap" so often.

This patch is cosmetic.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>
---
 net/core/netprio_cgroup.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 66d98da..92cc54c 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -71,26 +71,25 @@ static int extend_netdev_table(struct net_device *dev, u32 new_len)
 {
 	size_t new_size = sizeof(struct netprio_map) +
 			   ((sizeof(u32) * new_len));
-	struct netprio_map *new_priomap = kzalloc(new_size, GFP_KERNEL);
-	struct netprio_map *old_priomap;
+	struct netprio_map *new = kzalloc(new_size, GFP_KERNEL);
+	struct netprio_map *old;
 
-	old_priomap  = rtnl_dereference(dev->priomap);
+	old = rtnl_dereference(dev->priomap);
 
-	if (!new_priomap) {
+	if (!new) {
 		pr_warn("Unable to alloc new priomap!\n");
 		return -ENOMEM;
 	}
 
-	if (old_priomap)
-		memcpy(new_priomap->priomap, old_priomap->priomap,
-		       old_priomap->priomap_len *
-		       sizeof(old_priomap->priomap[0]));
+	if (old)
+		memcpy(new->priomap, old->priomap,
+		       old->priomap_len * sizeof(old->priomap[0]));
 
-	new_priomap->priomap_len = new_len;
+	new->priomap_len = new_len;
 
-	rcu_assign_pointer(dev->priomap, new_priomap);
-	if (old_priomap)
-		kfree_rcu(old_priomap, rcu);
+	rcu_assign_pointer(dev->priomap, new);
+	if (old)
+		kfree_rcu(old, rcu);
 	return 0;
 }
 
-- 
1.7.11.7

Re: [PATCH 3/7] netprio_cgroup: shorten variable names in extend_netdev_table()

[Daniel Wagner]

On 20.11.2012 09:30, Tejun Heo wrote:
> The function is about to go through a rewrite.  In preparation,
> shorten the variable names so that we don't repeat "priomap" so often.
>
> This patch is cosmetic.
>
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>

Tested and Acked-by: Daniel Wagner <daniel.wagner-98C5kh4wR6ohFhg+JK9F0w@public.gmane.org>

[PATCH 4/7] netprio_cgroup: reimplement priomap expansion

[Tejun Heo]

netprio kept track of the highest prioidx allocated and resized
priomaps accordingly when necessary.  This makes it necessary to keep
track of prioidx allocation and may end up resizing on every new
prioidx.

Update extend_netdev_table() such that it takes @target_idx which the
priomap should be able to accomodate.  If the priomap is large enough,
nothing happens; otherwise, the size is doubled until @target_idx can
be accomodated.

This makes max_prioidx and write_update_netdev_table() unnecessary.
write_priomap() now calls extend_netdev_table() directly.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>
---
 net/core/netprio_cgroup.c | 56 ++++++++++++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 23 deletions(-)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 92cc54c..569d83d 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -27,11 +27,11 @@
 
 #include <linux/fdtable.h>
 
+#define PRIOMAP_MIN_SZ		128
 #define PRIOIDX_SZ 128
 
 static unsigned long prioidx_map[PRIOIDX_SZ];
 static DEFINE_SPINLOCK(prioidx_map_lock);
-static atomic_t max_prioidx = ATOMIC_INIT(0);
 
 static inline struct cgroup_netprio_state *cgrp_netprio_state(struct cgroup *cgrp)
 {
@@ -51,8 +51,6 @@ static int get_prioidx(u32 *prio)
 		return -ENOSPC;
 	}
 	set_bit(prioidx, prioidx_map);
-	if (atomic_read(&max_prioidx) < prioidx)
-		atomic_set(&max_prioidx, prioidx);
 	spin_unlock_irqrestore(&prioidx_map_lock, flags);
 	*prio = prioidx;
 	return 0;
@@ -67,15 +65,40 @@ static void put_prioidx(u32 idx)
 	spin_unlock_irqrestore(&prioidx_map_lock, flags);
 }
 
-static int extend_netdev_table(struct net_device *dev, u32 new_len)
+/*
+ * Extend @dev->priomap so that it's large enough to accomodate
+ * @target_idx.  @dev->priomap.priomap_len > @target_idx after successful
+ * return.  Must be called under rtnl lock.
+ */
+static int extend_netdev_table(struct net_device *dev, u32 target_idx)
 {
-	size_t new_size = sizeof(struct netprio_map) +
-			   ((sizeof(u32) * new_len));
-	struct netprio_map *new = kzalloc(new_size, GFP_KERNEL);
-	struct netprio_map *old;
+	struct netprio_map *old, *new;
+	size_t new_sz, new_len;
 
+	/* is the existing priomap large enough? */
 	old = rtnl_dereference(dev->priomap);
+	if (old && old->priomap_len > target_idx)
+		return 0;
+
+	/*
+	 * Determine the new size.  Let's keep it power-of-two.  We start
+	 * from PRIOMAP_MIN_SZ and double it until it's large enough to
+	 * accommodate @target_idx.
+	 */
+	new_sz = PRIOMAP_MIN_SZ;
+	while (true) {
+		new_len = (new_sz - offsetof(struct netprio_map, priomap)) /
+			sizeof(new->priomap[0]);
+		if (new_len > target_idx)
+			break;
+		new_sz *= 2;
+		/* overflowed? */
+		if (WARN_ON(new_sz < PRIOMAP_MIN_SZ))
+			return -ENOSPC;
+	}
 
+	/* allocate & copy */
+	new = kzalloc(new_sz, GFP_KERNEL);
 	if (!new) {
 		pr_warn("Unable to alloc new priomap!\n");
 		return -ENOMEM;
@@ -87,26 +110,13 @@ static int extend_netdev_table(struct net_device *dev, u32 new_len)
 
 	new->priomap_len = new_len;
 
+	/* install the new priomap */
 	rcu_assign_pointer(dev->priomap, new);
 	if (old)
 		kfree_rcu(old, rcu);
 	return 0;
 }
 
-static int write_update_netdev_table(struct net_device *dev)
-{
-	int ret = 0;
-	u32 max_len;
-	struct netprio_map *map;
-
-	max_len = atomic_read(&max_prioidx) + 1;
-	map = rtnl_dereference(dev->priomap);
-	if (!map || map->priomap_len < max_len)
-		ret = extend_netdev_table(dev, max_len);
-
-	return ret;
-}
-
 static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
 {
 	struct cgroup_netprio_state *cs;
@@ -191,7 +201,7 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
 
 	rtnl_lock();
 
-	ret = write_update_netdev_table(dev);
+	ret = extend_netdev_table(dev, prioidx);
 	if (ret)
 		goto out_unlock;
 
-- 
1.7.11.7

Re: [PATCH 4/7] netprio_cgroup: reimplement priomap expansion

[Daniel Wagner]

Hi Tejun,

On 20.11.2012 09:30, Tejun Heo wrote:
> netprio kept track of the highest prioidx allocated and resized
> priomaps accordingly when necessary.  This makes it necessary to keep
> track of prioidx allocation and may end up resizing on every new
> prioidx.
> 
> Update extend_netdev_table() such that it takes @target_idx which the
> priomap should be able to accomodate.  If the priomap is large enough,
> nothing happens; otherwise, the size is doubled until @target_idx can
> be accomodated.
> 
> This makes max_prioidx and write_update_netdev_table() unnecessary.
> write_priomap() now calls extend_netdev_table() directly.
> 
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>
> ---
>   net/core/netprio_cgroup.c | 56 ++++++++++++++++++++++++++++-------------------
>   1 file changed, 33 insertions(+), 23 deletions(-)
> 
> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> index 92cc54c..569d83d 100644
> --- a/net/core/netprio_cgroup.c
> +++ b/net/core/netprio_cgroup.c
> @@ -27,11 +27,11 @@
>   
>   #include <linux/fdtable.h>
>   
> +#define PRIOMAP_MIN_SZ		128
>   #define PRIOIDX_SZ 128
>   
>   static unsigned long prioidx_map[PRIOIDX_SZ];
>   static DEFINE_SPINLOCK(prioidx_map_lock);
> -static atomic_t max_prioidx = ATOMIC_INIT(0);
>   
>   static inline struct cgroup_netprio_state *cgrp_netprio_state(struct cgroup *cgrp)
>   {
> @@ -51,8 +51,6 @@ static int get_prioidx(u32 *prio)
>   		return -ENOSPC;
>   	}
>   	set_bit(prioidx, prioidx_map);
> -	if (atomic_read(&max_prioidx) < prioidx)
> -		atomic_set(&max_prioidx, prioidx);
>   	spin_unlock_irqrestore(&prioidx_map_lock, flags);
>   	*prio = prioidx;
>   	return 0;
> @@ -67,15 +65,40 @@ static void put_prioidx(u32 idx)
>   	spin_unlock_irqrestore(&prioidx_map_lock, flags);
>   }
>   
> -static int extend_netdev_table(struct net_device *dev, u32 new_len)
> +/*
> + * Extend @dev->priomap so that it's large enough to accomodate
> + * @target_idx.  @dev->priomap.priomap_len > @target_idx after successful
> + * return.  Must be called under rtnl lock.
> + */
> +static int extend_netdev_table(struct net_device *dev, u32 target_idx)
>   {
> -	size_t new_size = sizeof(struct netprio_map) +
> -			   ((sizeof(u32) * new_len));
> -	struct netprio_map *new = kzalloc(new_size, GFP_KERNEL);
> -	struct netprio_map *old;
> +	struct netprio_map *old, *new;
> +	size_t new_sz, new_len;
>   
> +	/* is the existing priomap large enough? */
>   	old = rtnl_dereference(dev->priomap);
> +	if (old && old->priomap_len > target_idx)
> +		return 0;
> +
> +	/*
> +	 * Determine the new size.  Let's keep it power-of-two.  We start
> +	 * from PRIOMAP_MIN_SZ and double it until it's large enough to
> +	 * accommodate @target_idx.
> +	 */
> +	new_sz = PRIOMAP_MIN_SZ;
> +	while (true) {
> +		new_len = (new_sz - offsetof(struct netprio_map, priomap)) /
> +			sizeof(new->priomap[0]);
> +		if (new_len > target_idx)
> +			break;
> +		new_sz *= 2;
> +		/* overflowed? */
> +		if (WARN_ON(new_sz < PRIOMAP_MIN_SZ))
> +			return -ENOSPC;
> +	}
>   
> +	/* allocate & copy */
> +	new = kzalloc(new_sz, GFP_KERNEL);
>   	if (!new) {
>   		pr_warn("Unable to alloc new priomap!\n");
>   		return -ENOMEM;
> @@ -87,26 +110,13 @@ static int extend_netdev_table(struct net_device *dev, u32 new_len)
>   
>   	new->priomap_len = new_len;
>   
> +	/* install the new priomap */
>   	rcu_assign_pointer(dev->priomap, new);
>   	if (old)
>   		kfree_rcu(old, rcu);
>   	return 0;
>   }

Okay, I might be just to stupid to see the beauty in what you are doing. So
please bear with me when I ask these question.

struct netprio_map {
	struct rcu_head rcu;
	struct netprio_aux *aux;	/* auxiliary config array */
	u32 priomap_len;
	u32 priomap[];
};

Is there a specific reason why aux and priomap is handled differently? Couldn't you 
just use same approach for both variables, e.g. re/allocating only them here and
leave the allocation struct netprio_map in cgrp_css_alloc()?

Also the algorithm to figure out the size of the array might be a bit too aggressive
in my opinion. So you always start at PRIOMAP_MIN_SIZE and then try to double
the size until target_idx fits. Wouldn't it make sense to start to look
for the new size beginning at old->priomap_len and then do the power-of-two
increase?

cheers,
daniel

Re: [PATCH 4/7] netprio_cgroup: reimplement priomap expansion

[Tejun Heo]

Hello, Daniel.

On Tue, Nov 20, 2012 at 09:46:22AM +0100, Daniel Wagner wrote:
> struct netprio_map {
> 	struct rcu_head rcu;
> 	struct netprio_aux *aux;	/* auxiliary config array */
> 	u32 priomap_len;
> 	u32 priomap[];
> };
> 
> Is there a specific reason why aux and priomap is handled
> differently? Couldn't you just use same approach for both variables,
> e.g. re/allocating only them here and leave the allocation struct
> netprio_map in cgrp_css_alloc()?

->aux is no longer added, so the consistency issue doesn't exist
anymore.  The reason why they were handled differently before (or
rather why I didn't change priomap[] to be allocated separately) was
that pointer chasing tends to be more expensive than offsetting.  I
don't know how much effect it would have in this case but things
sitting in packet in/out paths can be very hot so didn't wanna disturb
it.

> Also the algorithm to figure out the size of the array might be a
> bit too aggressive in my opinion. So you always start at
> PRIOMAP_MIN_SIZE and then try to double the size until target_idx
> fits. Wouldn't it make sense to start to look for the new size
> beginning at old->priomap_len and then do the power-of-two increase?

The only downside of always starting from PRIOMAP_MIN_SIZE is
iterating several more times in the sizing loop which isn't really
anything to worry about.  The loop is structured that way because I
wanted to keep the size of the whole thing power-of-two.  Due to the
fields before priomap[], if we size priomap_len power-of-two, we'll
always end up with something slightly over power-of-two, which is
usually the worst size to allocate.

Thanks.

-- 
tejun

Re: [PATCH 4/7] netprio_cgroup: reimplement priomap expansion

[Daniel Wagner]

On 20.11.2012 15:38, Tejun Heo wrote:
> Hello, Daniel.
>
> On Tue, Nov 20, 2012 at 09:46:22AM +0100, Daniel Wagner wrote:
>> struct netprio_map {
>> 	struct rcu_head rcu;
>> 	struct netprio_aux *aux;	/* auxiliary config array */
>> 	u32 priomap_len;
>> 	u32 priomap[];
>> };
>>
>> Is there a specific reason why aux and priomap is handled
>> differently? Couldn't you just use same approach for both variables,
>> e.g. re/allocating only them here and leave the allocation struct
>> netprio_map in cgrp_css_alloc()?
>
> ->aux is no longer added, so the consistency issue doesn't exist
> anymore.

Right, I got confused looking at v1 and v2.

> The reason why they were handled differently before (or
> rather why I didn't change priomap[] to be allocated separately) was
> that pointer chasing tends to be more expensive than offsetting.  I
> don't know how much effect it would have in this case but things
> sitting in packet in/out paths can be very hot so didn't wanna disturb
> it.

I see.

>> Also the algorithm to figure out the size of the array might be a
>> bit too aggressive in my opinion. So you always start at
>> PRIOMAP_MIN_SIZE and then try to double the size until target_idx
>> fits. Wouldn't it make sense to start to look for the new size
>> beginning at old->priomap_len and then do the power-of-two increase?
>
> The only downside of always starting from PRIOMAP_MIN_SIZE is
> iterating several more times in the sizing loop which isn't really
> anything to worry about.  The loop is structured that way because I
> wanted to keep the size of the whole thing power-of-two.  Due to the
> fields before priomap[], if we size priomap_len power-of-two, we'll
> always end up with something slightly over power-of-two, which is
> usually the worst size to allocate.

Thanks for the explanation. I was pondering if the new size in power of 
two could be a bit too excessive and the allocation step could be 
linear, e.g. stick at 4096. target_id will increase linear, therefore 
linear increase might also be enough, no?

cheers,
daniel

Re: [PATCH 4/7] netprio_cgroup: reimplement priomap expansion

[Tejun Heo]

Hello,

On Tue, Nov 20, 2012 at 04:09:22PM +0100, Daniel Wagner wrote:
> Thanks for the explanation. I was pondering if the new size in power
> of two could be a bit too excessive and the allocation step could be
> linear, e.g. stick at 4096. target_id will increase linear,
> therefore linear increase might also be enough, no?

Well, power-of-two resizing tends to behave relatively well under most
cases and slab allocations are binned by power-of-two sizes, so
linearly growing it doesn't really buy anything.

Thanks.

-- 
tejun

Re: [PATCH 4/7] netprio_cgroup: reimplement priomap expansion

[Daniel Wagner]

On 20.11.2012 16:13, Tejun Heo wrote:
> Hello,
>
> On Tue, Nov 20, 2012 at 04:09:22PM +0100, Daniel Wagner wrote:
>> Thanks for the explanation. I was pondering if the new size in power
>> of two could be a bit too excessive and the allocation step could be
>> linear, e.g. stick at 4096. target_id will increase linear,
>> therefore linear increase might also be enough, no?
>
> Well, power-of-two resizing tends to behave relatively well under most
> cases and slab allocations are binned by power-of-two sizes, so
> linearly growing it doesn't really buy anything.

Convinced :)

Tested and Acked-by: Daniel Wagner <daniel.wagner-98C5kh4wR6ohFhg+JK9F0w@public.gmane.org>

thanks,
daniel

[PATCH 5/7] netprio_cgroup: use cgroup->id instead of cgroup_netprio_state->prioidx

[Tejun Heo]

With priomap expansion no longer depending on knowing max id
allocated, netprio_cgroup can use cgroup->id insted of cs->prioidx.
Drop prioidx alloc/free logic and convert all uses to cgroup->id.

* In cgrp_css_alloc(), parent->id test is moved above @cs allocation
  to simplify error path.

* In cgrp_css_free(), @cs assignment is made initialization.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>
---
 include/net/netprio_cgroup.h | 11 +++-----
 net/core/netprio_cgroup.c    | 65 ++++++++------------------------------------
 2 files changed, 15 insertions(+), 61 deletions(-)

diff --git a/include/net/netprio_cgroup.h b/include/net/netprio_cgroup.h
index 2760f4f..1d04b6f 100644
--- a/include/net/netprio_cgroup.h
+++ b/include/net/netprio_cgroup.h
@@ -27,7 +27,6 @@ struct netprio_map {
 
 struct cgroup_netprio_state {
 	struct cgroup_subsys_state css;
-	u32 prioidx;
 };
 
 extern void sock_update_netprioidx(struct sock *sk, struct task_struct *task);
@@ -36,13 +35,12 @@ extern void sock_update_netprioidx(struct sock *sk, struct task_struct *task);
 
 static inline u32 task_netprioidx(struct task_struct *p)
 {
-	struct cgroup_netprio_state *state;
+	struct cgroup_subsys_state *css;
 	u32 idx;
 
 	rcu_read_lock();
-	state = container_of(task_subsys_state(p, net_prio_subsys_id),
-			     struct cgroup_netprio_state, css);
-	idx = state->prioidx;
+	css = task_subsys_state(p, net_prio_subsys_id);
+	idx = css->cgroup->id;
 	rcu_read_unlock();
 	return idx;
 }
@@ -57,8 +55,7 @@ static inline u32 task_netprioidx(struct task_struct *p)
 	rcu_read_lock();
 	css = task_subsys_state(p, net_prio_subsys_id);
 	if (css)
-		idx = container_of(css,
-				   struct cgroup_netprio_state, css)->prioidx;
+		idx = css->cgroup->id;
 	rcu_read_unlock();
 	return idx;
 }
diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 569d83d..9409cdf 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -28,10 +28,6 @@
 #include <linux/fdtable.h>
 
 #define PRIOMAP_MIN_SZ		128
-#define PRIOIDX_SZ 128
-
-static unsigned long prioidx_map[PRIOIDX_SZ];
-static DEFINE_SPINLOCK(prioidx_map_lock);
 
 static inline struct cgroup_netprio_state *cgrp_netprio_state(struct cgroup *cgrp)
 {
@@ -39,32 +35,6 @@ static inline struct cgroup_netprio_state *cgrp_netprio_state(struct cgroup *cgr
 			    struct cgroup_netprio_state, css);
 }
 
-static int get_prioidx(u32 *prio)
-{
-	unsigned long flags;
-	u32 prioidx;
-
-	spin_lock_irqsave(&prioidx_map_lock, flags);
-	prioidx = find_first_zero_bit(prioidx_map, sizeof(unsigned long) * PRIOIDX_SZ);
-	if (prioidx == sizeof(unsigned long) * PRIOIDX_SZ) {
-		spin_unlock_irqrestore(&prioidx_map_lock, flags);
-		return -ENOSPC;
-	}
-	set_bit(prioidx, prioidx_map);
-	spin_unlock_irqrestore(&prioidx_map_lock, flags);
-	*prio = prioidx;
-	return 0;
-}
-
-static void put_prioidx(u32 idx)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&prioidx_map_lock, flags);
-	clear_bit(idx, prioidx_map);
-	spin_unlock_irqrestore(&prioidx_map_lock, flags);
-}
-
 /*
  * Extend @dev->priomap so that it's large enough to accomodate
  * @target_idx.  @dev->priomap.priomap_len > @target_idx after successful
@@ -120,62 +90,50 @@ static int extend_netdev_table(struct net_device *dev, u32 target_idx)
 static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
 {
 	struct cgroup_netprio_state *cs;
-	int ret = -EINVAL;
+
+	if (cgrp->parent && cgrp->parent->id)
+		return ERR_PTR(-EINVAL);
 
 	cs = kzalloc(sizeof(*cs), GFP_KERNEL);
 	if (!cs)
 		return ERR_PTR(-ENOMEM);
 
-	if (cgrp->parent && cgrp_netprio_state(cgrp->parent)->prioidx)
-		goto out;
-
-	ret = get_prioidx(&cs->prioidx);
-	if (ret < 0) {
-		pr_warn("No space in priority index array\n");
-		goto out;
-	}
-
 	return &cs->css;
-out:
-	kfree(cs);
-	return ERR_PTR(ret);
 }
 
 static void cgrp_css_free(struct cgroup *cgrp)
 {
-	struct cgroup_netprio_state *cs;
+	struct cgroup_netprio_state *cs = cgrp_netprio_state(cgrp);
 	struct net_device *dev;
 	struct netprio_map *map;
 
-	cs = cgrp_netprio_state(cgrp);
 	rtnl_lock();
 	for_each_netdev(&init_net, dev) {
 		map = rtnl_dereference(dev->priomap);
-		if (map && cs->prioidx < map->priomap_len)
-			map->priomap[cs->prioidx] = 0;
+		if (map && cgrp->id < map->priomap_len)
+			map->priomap[cgrp->id] = 0;
 	}
 	rtnl_unlock();
-	put_prioidx(cs->prioidx);
 	kfree(cs);
 }
 
 static u64 read_prioidx(struct cgroup *cgrp, struct cftype *cft)
 {
-	return (u64)cgrp_netprio_state(cgrp)->prioidx;
+	return cgrp->id;
 }
 
 static int read_priomap(struct cgroup *cont, struct cftype *cft,
 			struct cgroup_map_cb *cb)
 {
 	struct net_device *dev;
-	u32 prioidx = cgrp_netprio_state(cont)->prioidx;
+	u32 id = cont->id;
 	u32 priority;
 	struct netprio_map *map;
 
 	rcu_read_lock();
 	for_each_netdev_rcu(&init_net, dev) {
 		map = rcu_dereference(dev->priomap);
-		priority = (map && prioidx < map->priomap_len) ? map->priomap[prioidx] : 0;
+		priority = (map && id < map->priomap_len) ? map->priomap[id] : 0;
 		cb->fill(cb, dev->name, priority);
 	}
 	rcu_read_unlock();
@@ -185,7 +143,6 @@ static int read_priomap(struct cgroup *cont, struct cftype *cft,
 static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
 			 const char *buffer)
 {
-	u32 prioidx = cgrp_netprio_state(cgrp)->prioidx;
 	char devname[IFNAMSIZ + 1];
 	struct net_device *dev;
 	struct netprio_map *map;
@@ -201,13 +158,13 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
 
 	rtnl_lock();
 
-	ret = extend_netdev_table(dev, prioidx);
+	ret = extend_netdev_table(dev, cgrp->id);
 	if (ret)
 		goto out_unlock;
 
 	map = rtnl_dereference(dev->priomap);
 	if (map)
-		map->priomap[prioidx] = prio;
+		map->priomap[cgrp->id] = prio;
 out_unlock:
 	rtnl_unlock();
 	dev_put(dev);
-- 
1.7.11.7

Re: [PATCH 5/7] netprio_cgroup: use cgroup->id instead of cgroup_netprio_state->prioidx

[Daniel Wagner]

On 20.11.2012 09:30, Tejun Heo wrote:
> With priomap expansion no longer depending on knowing max id
> allocated, netprio_cgroup can use cgroup->id insted of cs->prioidx.
> Drop prioidx alloc/free logic and convert all uses to cgroup->id.
>
> * In cgrp_css_alloc(), parent->id test is moved above @cs allocation
>    to simplify error path.
>
> * In cgrp_css_free(), @cs assignment is made initialization.
>
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>

Tested and Acked-by: Daniel Wagner <daniel.wagner-98C5kh4wR6ohFhg+JK9F0w@public.gmane.org>

[PATCH 6/7] netprio_cgroup: implement netprio[_set]_prio() helpers

[Tejun Heo]

Introduce two helpers - netprio_prio() and netprio_set_prio() - which
hide the details of priomap access and expansion.  This will help
implementing hierarchy support.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>
---
 net/core/netprio_cgroup.c | 72 ++++++++++++++++++++++++++++++++---------------
 1 file changed, 50 insertions(+), 22 deletions(-)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 9409cdf..b2af0d0 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -87,6 +87,51 @@ static int extend_netdev_table(struct net_device *dev, u32 target_idx)
 	return 0;
 }
 
+/**
+ * netprio_prio - return the effective netprio of a cgroup-net_device pair
+ * @cgrp: cgroup part of the target pair
+ * @dev: net_device part of the target pair
+ *
+ * Should be called under RCU read or rtnl lock.
+ */
+static u32 netprio_prio(struct cgroup *cgrp, struct net_device *dev)
+{
+	struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);
+
+	if (map && cgrp->id < map->priomap_len)
+		return map->priomap[cgrp->id];
+	return 0;
+}
+
+/**
+ * netprio_set_prio - set netprio on a cgroup-net_device pair
+ * @cgrp: cgroup part of the target pair
+ * @dev: net_device part of the target pair
+ * @prio: prio to set
+ *
+ * Set netprio to @prio on @cgrp-@dev pair.  Should be called under rtnl
+ * lock and may fail under memory pressure for non-zero @prio.
+ */
+static int netprio_set_prio(struct cgroup *cgrp, struct net_device *dev,
+			    u32 prio)
+{
+	struct netprio_map *map;
+	int ret;
+
+	/* avoid extending priomap for zero writes */
+	map = rtnl_dereference(dev->priomap);
+	if (!prio && (!map || map->priomap_len <= cgrp->id))
+		return 0;
+
+	ret = extend_netdev_table(dev, cgrp->id);
+	if (ret)
+		return ret;
+
+	map = rtnl_dereference(dev->priomap);
+	map->priomap[cgrp->id] = prio;
+	return 0;
+}
+
 static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
 {
 	struct cgroup_netprio_state *cs;
@@ -105,14 +150,10 @@ static void cgrp_css_free(struct cgroup *cgrp)
 {
 	struct cgroup_netprio_state *cs = cgrp_netprio_state(cgrp);
 	struct net_device *dev;
-	struct netprio_map *map;
 
 	rtnl_lock();
-	for_each_netdev(&init_net, dev) {
-		map = rtnl_dereference(dev->priomap);
-		if (map && cgrp->id < map->priomap_len)
-			map->priomap[cgrp->id] = 0;
-	}
+	for_each_netdev(&init_net, dev)
+		WARN_ON_ONCE(netprio_set_prio(cgrp, dev, 0));
 	rtnl_unlock();
 	kfree(cs);
 }
@@ -126,16 +167,10 @@ static int read_priomap(struct cgroup *cont, struct cftype *cft,
 			struct cgroup_map_cb *cb)
 {
 	struct net_device *dev;
-	u32 id = cont->id;
-	u32 priority;
-	struct netprio_map *map;
 
 	rcu_read_lock();
-	for_each_netdev_rcu(&init_net, dev) {
-		map = rcu_dereference(dev->priomap);
-		priority = (map && id < map->priomap_len) ? map->priomap[id] : 0;
-		cb->fill(cb, dev->name, priority);
-	}
+	for_each_netdev_rcu(&init_net, dev)
+		cb->fill(cb, dev->name, netprio_prio(cont, dev));
 	rcu_read_unlock();
 	return 0;
 }
@@ -145,7 +180,6 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
 {
 	char devname[IFNAMSIZ + 1];
 	struct net_device *dev;
-	struct netprio_map *map;
 	u32 prio;
 	int ret;
 
@@ -158,14 +192,8 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
 
 	rtnl_lock();
 
-	ret = extend_netdev_table(dev, cgrp->id);
-	if (ret)
-		goto out_unlock;
+	ret = netprio_set_prio(cgrp, dev, prio);
 
-	map = rtnl_dereference(dev->priomap);
-	if (map)
-		map->priomap[cgrp->id] = prio;
-out_unlock:
 	rtnl_unlock();
 	dev_put(dev);
 	return ret;
-- 
1.7.11.7

Re: [PATCH 6/7] netprio_cgroup: implement netprio[_set]_prio() helpers

[Daniel Wagner]

On 20.11.2012 09:30, Tejun Heo wrote:
> Introduce two helpers - netprio_prio() and netprio_set_prio() - which
> hide the details of priomap access and expansion.  This will help
> implementing hierarchy support.
>
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>

Tested and Acked-by: Daniel Wagner <daniel.wagner-98C5kh4wR6ohFhg+JK9F0w@public.gmane.org>

[PATCH 7/7] netprio_cgroup: allow nesting and inherit config on cgroup creation

[Tejun Heo]

Inherit netprio configuration from ->css_online(), allow nesting and
remove .broken_hierarchy marking.  This makes netprio_cgroup's
behavior match netcls_cgroup's.

Note that this patch changes userland-visible behavior.  Nesting is
allowed and the first level cgroups below the root cgroup behave
differently - they inherit priorities from the root cgroup on creation
instead of starting with 0.  This is unfortunate but not doing so is
much crazier.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 Documentation/cgroups/net_prio.txt |  2 ++
 net/core/netprio_cgroup.c          | 42 ++++++++++++++++++++++----------------
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/Documentation/cgroups/net_prio.txt b/Documentation/cgroups/net_prio.txt
index 01b3226..a82cbd2 100644
--- a/Documentation/cgroups/net_prio.txt
+++ b/Documentation/cgroups/net_prio.txt
@@ -51,3 +51,5 @@ One usage for the net_prio cgroup is with mqprio qdisc allowing application
 traffic to be steered to hardware/driver based traffic classes. These mappings
 can then be managed by administrators or other networking protocols such as
 DCBX.
+
+A new net_prio cgroup inherits the parent's configuration.
diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index b2af0d0..bde53da 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -136,9 +136,6 @@ static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
 {
 	struct cgroup_netprio_state *cs;
 
-	if (cgrp->parent && cgrp->parent->id)
-		return ERR_PTR(-EINVAL);
-
 	cs = kzalloc(sizeof(*cs), GFP_KERNEL);
 	if (!cs)
 		return ERR_PTR(-ENOMEM);
@@ -146,16 +143,34 @@ static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
 	return &cs->css;
 }
 
-static void cgrp_css_free(struct cgroup *cgrp)
+static int cgrp_css_online(struct cgroup *cgrp)
 {
-	struct cgroup_netprio_state *cs = cgrp_netprio_state(cgrp);
+	struct cgroup *parent = cgrp->parent;
 	struct net_device *dev;
+	int ret = 0;
+
+	if (!parent)
+		return 0;
 
 	rtnl_lock();
-	for_each_netdev(&init_net, dev)
-		WARN_ON_ONCE(netprio_set_prio(cgrp, dev, 0));
+	/*
+	 * Inherit prios from the parent.  As all prios are set during
+	 * onlining, there is no need to clear them on offline.
+	 */
+	for_each_netdev(&init_net, dev) {
+		u32 prio = netprio_prio(parent, dev);
+
+		ret = netprio_set_prio(cgrp, dev, prio);
+		if (ret)
+			break;
+	}
 	rtnl_unlock();
-	kfree(cs);
+	return ret;
+}
+
+static void cgrp_css_free(struct cgroup *cgrp)
+{
+	kfree(cgrp_netprio_state(cgrp));
 }
 
 static u64 read_prioidx(struct cgroup *cgrp, struct cftype *cft)
@@ -237,21 +252,12 @@ static struct cftype ss_files[] = {
 struct cgroup_subsys net_prio_subsys = {
 	.name		= "net_prio",
 	.css_alloc	= cgrp_css_alloc,
+	.css_online	= cgrp_css_online,
 	.css_free	= cgrp_css_free,
 	.attach		= net_prio_attach,
 	.subsys_id	= net_prio_subsys_id,
 	.base_cftypes	= ss_files,
 	.module		= THIS_MODULE,
-
-	/*
-	 * net_prio has artificial limit on the number of cgroups and
-	 * disallows nesting making it impossible to co-mount it with other
-	 * hierarchical subsystems.  Remove the artificially low PRIOIDX_SZ
-	 * limit and properly nest configuration such that children follow
-	 * their parents' configurations by default and are allowed to
-	 * override and remove the following.
-	 */
-	.broken_hierarchy = true,
 };
 
 static int netprio_device_event(struct notifier_block *unused,
-- 
1.7.11.7

Re: [PATCH 7/7] netprio_cgroup: allow nesting and inherit config on cgroup creation

[Daniel Wagner]

Hi Tejun,

On 20.11.2012 09:30, Tejun Heo wrote:
> Inherit netprio configuration from ->css_online(), allow nesting and
> remove .broken_hierarchy marking.  This makes netprio_cgroup's
> behavior match netcls_cgroup's.
>
> Note that this patch changes userland-visible behavior.  Nesting is
> allowed and the first level cgroups below the root cgroup behave
> differently - they inherit priorities from the root cgroup on creation
> instead of starting with 0.  This is unfortunate but not doing so is
> much crazier.
>
> Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

Tested and Acked-by: Daniel Wagner <daniel.wagner-98C5kh4wR6ohFhg+JK9F0w@public.gmane.org>

> ---
>   Documentation/cgroups/net_prio.txt |  2 ++
>   net/core/netprio_cgroup.c          | 42 ++++++++++++++++++++++----------------
>   2 files changed, 26 insertions(+), 18 deletions(-)
>
> diff --git a/Documentation/cgroups/net_prio.txt b/Documentation/cgroups/net_prio.txt
> index 01b3226..a82cbd2 100644
> --- a/Documentation/cgroups/net_prio.txt
> +++ b/Documentation/cgroups/net_prio.txt
> @@ -51,3 +51,5 @@ One usage for the net_prio cgroup is with mqprio qdisc allowing application
>   traffic to be steered to hardware/driver based traffic classes. These mappings
>   can then be managed by administrators or other networking protocols such as
>   DCBX.
> +
> +A new net_prio cgroup inherits the parent's configuration.
> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> index b2af0d0..bde53da 100644
> --- a/net/core/netprio_cgroup.c
> +++ b/net/core/netprio_cgroup.c
> @@ -136,9 +136,6 @@ static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
>   {
>   	struct cgroup_netprio_state *cs;
>
> -	if (cgrp->parent && cgrp->parent->id)
> -		return ERR_PTR(-EINVAL);
> -
>   	cs = kzalloc(sizeof(*cs), GFP_KERNEL);
>   	if (!cs)
>   		return ERR_PTR(-ENOMEM);
> @@ -146,16 +143,34 @@ static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
>   	return &cs->css;
>   }
>
> -static void cgrp_css_free(struct cgroup *cgrp)
> +static int cgrp_css_online(struct cgroup *cgrp)
>   {
> -	struct cgroup_netprio_state *cs = cgrp_netprio_state(cgrp);
> +	struct cgroup *parent = cgrp->parent;
>   	struct net_device *dev;
> +	int ret = 0;
> +
> +	if (!parent)
> +		return 0;

BTW, parent is always != NULL, because the root cgroup will be attached 
to the dummytop cgroup.

This is the reason why there are this check in netprio_prio()

static u32 netprio_prio(struct cgroup *cgrp, struct net_device *dev)
{
	struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);

	if (map && cgrp->id < map->priomap_len)
		return map->priomap[cgrp->id];

is necessary.

cheer,
daniel

Re: [PATCH 7/7] netprio_cgroup: allow nesting and inherit config on cgroup creation

[Tejun Heo]

Hello, Daniel.

On Tue, Nov 20, 2012 at 09:57:14AM +0100, Daniel Wagner wrote:
> >-static void cgrp_css_free(struct cgroup *cgrp)
> >+static int cgrp_css_online(struct cgroup *cgrp)
> >  {
> >-	struct cgroup_netprio_state *cs = cgrp_netprio_state(cgrp);
> >+	struct cgroup *parent = cgrp->parent;
> >  	struct net_device *dev;
> >+	int ret = 0;
> >+
> >+	if (!parent)
> >+		return 0;
> 
> BTW, parent is always != NULL, because the root cgroup will be
> attached to the dummytop cgroup.

Hmmm?  I'm confused.  When ->css_online() is called for dummytop in
cgroup_init_subsys(), its parent is NULL.  What am I missing?

Thanks.

-- 
tejun

Re: [PATCH 7/7] netprio_cgroup: allow nesting and inherit config on cgroup creation

[Daniel Wagner]

Hi Tejun,

On 20.11.2012 15:40, Tejun Heo wrote:
> Hello, Daniel.
>
> On Tue, Nov 20, 2012 at 09:57:14AM +0100, Daniel Wagner wrote:
>>> -static void cgrp_css_free(struct cgroup *cgrp)
>>> +static int cgrp_css_online(struct cgroup *cgrp)
>>>   {
>>> -	struct cgroup_netprio_state *cs = cgrp_netprio_state(cgrp);
>>> +	struct cgroup *parent = cgrp->parent;
>>>   	struct net_device *dev;
>>> +	int ret = 0;
>>> +
>>> +	if (!parent)
>>> +		return 0;
>>
>> BTW, parent is always != NULL, because the root cgroup will be
>> attached to the dummytop cgroup.
>
> Hmmm?  I'm confused.  When ->css_online() is called for dummytop in
> cgroup_init_subsys(), its parent is NULL.  What am I missing?

Forget my comment, I was really confused when writing this. I was 
looking only at cgroups which were created after bootup.

cheers,
daniel

Re: [PATCHSET REPOST v2 cgroup/for-3.8] netcls/prio_cgroup: update hierarchy support

[David Miller]

From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Date: Tue, 20 Nov 2012 00:30:04 -0800

>  0001-netcls_cgroup-move-config-inheritance-to-css_online-.patch
>  0002-netprio_cgroup-simplify-write_priomap.patch
>  0003-netprio_cgroup-shorten-variable-names-in-extend_netd.patch
>  0004-netprio_cgroup-reimplement-priomap-expansion.patch
>  0005-netprio_cgroup-use-cgroup-id-instead-of-cgroup_netpr.patch
>  0006-netprio_cgroup-implement-netprio-_set-_prio-helpers.patch
>  0007-netprio_cgroup-allow-nesting-and-inherit-config-on-c.patch

For series:

Acked-by: David S. Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>

Re: [PATCHSET REPOST v2 cgroup/for-3.8] netcls/prio_cgroup: update hierarchy support

[Tejun Heo]

Applied to cgroup/for-3.8.  Thanks.

-- 
tejun

[PATCH 2/7] netprio_cgroup: simplify write_priomap()

[Tejun Heo]

sscanf() doesn't bite.

Signed-off-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Acked-by: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>
---
 net/core/netprio_cgroup.c | 56 ++++++++++-------------------------------------
 1 file changed, 11 insertions(+), 45 deletions(-)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index f0b6b0d..66d98da 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -176,66 +176,32 @@ static int read_priomap(struct cgroup *cont, struct cftype *cft,
 static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
 			 const char *buffer)
 {
-	char *devname = kstrdup(buffer, GFP_KERNEL);
-	int ret = -EINVAL;
 	u32 prioidx = cgrp_netprio_state(cgrp)->prioidx;
-	unsigned long priority;
-	char *priostr;
+	char devname[IFNAMSIZ + 1];
 	struct net_device *dev;
 	struct netprio_map *map;
+	u32 prio;
+	int ret;
 
-	if (!devname)
-		return -ENOMEM;
-
-	/*
-	 * Minimally sized valid priomap string
-	 */
-	if (strlen(devname) < 3)
-		goto out_free_devname;
-
-	priostr = strstr(devname, " ");
-	if (!priostr)
-		goto out_free_devname;
-
-	/*
-	 *Separate the devname from the associated priority
-	 *and advance the priostr pointer to the priority value
-	 */
-	*priostr = '\0';
-	priostr++;
-
-	/*
-	 * If the priostr points to NULL, we're at the end of the passed
-	 * in string, and its not a valid write
-	 */
-	if (*priostr == '\0')
-		goto out_free_devname;
-
-	ret = kstrtoul(priostr, 10, &priority);
-	if (ret < 0)
-		goto out_free_devname;
-
-	ret = -ENODEV;
+	if (sscanf(buffer, "%"__stringify(IFNAMSIZ)"s %u", devname, &prio) != 2)
+		return -EINVAL;
 
 	dev = dev_get_by_name(&init_net, devname);
 	if (!dev)
-		goto out_free_devname;
+		return -ENODEV;
 
 	rtnl_lock();
+
 	ret = write_update_netdev_table(dev);
-	if (ret < 0)
-		goto out_put_dev;
+	if (ret)
+		goto out_unlock;
 
 	map = rtnl_dereference(dev->priomap);
 	if (map)
-		map->priomap[prioidx] = priority;
-
-out_put_dev:
+		map->priomap[prioidx] = prio;
+out_unlock:
 	rtnl_unlock();
 	dev_put(dev);
-
-out_free_devname:
-	kfree(devname);
 	return ret;
 }
 
-- 
1.7.11.7