[PATCH RESEND] cgroups: Allow dynamically changing net_classid

From: Nina Schiff
Date: Fri Nov 20 2015 - 15:32:01 EST

The classid of a process is changed either when a process is moved to
or from a cgroup or when the net_cls.classid file is updated.
Previously net_cls only supported propogating these changes to the
cgroup's related sockets when a process was added or removed from the
cgroup. This means it was neccessary to remove and re-add all processes
to a cgroup in order to update its classid. This change introduces
support for doing this dynamically - i.e. when the value is changed in
the net_cls_classid file, this will also trigger an update to the
classid associated with all sockets controlled by the cgroup.
This mimics the behaviour of other cgroup subsystems.
net_prio circumvents this issue by storing an index into a table with
each socket (and so any updates to the table, don't require updating
the value associated with the socket). net_cls, however, passes the
socket the classid directly, and so this additional step is needed.

Signed-off-by: Nina Schiff <ninasc@xxxxxx>
Concatented two email addresses by mistake, so resending

net/core/netclassid_cgroup.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/net/core/netclassid_cgroup.c b/net/core/netclassid_cgroup.c
index 6441f47..2e4df84 100644
--- a/net/core/netclassid_cgroup.c
+++ b/net/core/netclassid_cgroup.c
@@ -56,7 +56,7 @@ static void cgrp_css_free(struct cgroup_subsys_state *css)

-static int update_classid(const void *v, struct file *file, unsigned n)
+static int update_classid_sock(const void *v, struct file *file, unsigned n)
int err;
struct socket *sock = sock_from_file(file, &err);
@@ -67,18 +67,25 @@ static int update_classid(const void *v, struct file *file, unsigned n)
return 0;

-static void cgrp_attach(struct cgroup_subsys_state *css,
- struct cgroup_taskset *tset)
+static void update_classid(struct cgroup_subsys_state *css, void *v)
- struct cgroup_cls_state *cs = css_cls_state(css);
- void *v = (void *)(unsigned long)cs->classid;
+ struct css_task_iter it;
struct task_struct *p;

- cgroup_taskset_for_each(p, tset) {
+ css_task_iter_start(css, &it);
+ while ((p = css_task_iter_next(&it))) {
- iterate_fd(p->files, 0, update_classid, v);
+ iterate_fd(p->files, 0, update_classid_sock, v);
+ css_task_iter_end(&it);
+static void cgrp_attach(struct cgroup_subsys_state *css,
+ struct cgroup_taskset *tset)
+ update_classid(css,
+ (void *)(unsigned long)css_cls_state(css)->classid);

static u64 read_classid(struct cgroup_subsys_state *css, struct cftype *cft)
@@ -89,8 +96,11 @@ static u64 read_classid(struct cgroup_subsys_state *css, struct cftype *cft)
static int write_classid(struct cgroup_subsys_state *css, struct cftype *cft,
u64 value)
- css_cls_state(css)->classid = (u32) value;
+ struct cgroup_cls_state *cs = css_cls_state(css);
+ cs->classid = (u32)value;

+ update_classid(css, (void *)(unsigned long)cs->classid);
return 0;


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/