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Date: Sun, 22 Dec 2013 05:07:39 -0500
From: Oren Laadan <orenl@...lrox.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Linux Containers <containers@...ts.linux-foundation.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
lxc-devel <lxc-devel@...ts.sourceforge.net>,
Serge Hallyn <serge@...lyn.com>,
Eric Biederman <ebiederm@...ssion.com>,
Arve Hjønnevåg <arve@...roid.com>,
Amir Goldstein <amir@...lrox.com>,
Oren Laadan <orenl@...lrox.com>
Subject: [PATCH 1/2] ipc namespace: a generic per-ipc pointer and peripc_ops
Add a void * pointer to struct ipc_namespace. The access rules are:
1. (un)register ops with (un)register_peripc_operations()
2. call ipc_assign_generic() to put private data on the ipc_namespace
3. call ipc_access_generic() to access the private data
4. do not change the pointer during the lifetime of ipc_namespace
Modeled after generic net-ns pointers (commit dec827d), but simplified
to accommodate a single user for now (reduce code churn):
5. only one caller can register at a time
6. caller must register at boot time (not to be used by modules)
Signed-off-by: Oren Laadan <orenl@...lrox.com>
Signed-off-by: Amir Goldstein <amir@...lrox.com>
---
include/linux/ipc_namespace.h | 29 +++++++++++++++++++++
ipc/namespace.c | 9 +++++++
ipc/util.c | 60 +++++++++++++++++++++++++++++++++++++++++++
ipc/util.h | 3 +++
4 files changed, 101 insertions(+)
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index f6c82de..72da9bf 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -70,8 +70,37 @@ struct ipc_namespace {
struct user_namespace *user_ns;
unsigned int proc_inum;
+
+ /* allow others to piggyback on ipc_namesspaces */
+ void *gen; /* for others' private stuff */
};
+/*
+ * To access to the per-ipc generic data:
+ * 1. (un)register ops with (un)register_peripc_operations()
+ * 2. call ipc_assign_generic() to put private data on the ipc_namespace
+ * 3. call ipc_access_generic() to access the private data
+ * 4. do not change the pointer during the lifetime of ipc_namespace
+ *
+ * Modeled after generic net-ns pointers (commit dec827d), simplified for
+ * a single user case for now:
+ * 5. only one caller can register at a time
+ * 6. caller must register at boot time (not to be used by modules)
+ */
+struct peripc_operations {
+ int (*init)(struct ipc_namespace *);
+ void (*exit)(struct ipc_namespace *);
+};
+
+static inline void ipc_assign_generic(struct ipc_namespace *ns, void *data)
+{ ns->gen = data; }
+
+static inline void *ipc_access_generic(struct ipc_namespace *ns)
+{ return ns->gen; }
+
+extern int register_peripc_ops(struct peripc_operations *ops);
+extern void unregister_peripc_ops(struct peripc_operations *ops);
+
extern struct ipc_namespace init_ipc_ns;
extern atomic_t nr_ipc_ns;
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 59451c1..83968b6 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -33,9 +33,17 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
}
atomic_set(&ns->count, 1);
+
+ err = init_peripc_ns(ns);
+ if (err) {
+ kfree(ns);
+ return ERR_PTR(err);
+ }
+
err = mq_init_ns(ns);
if (err) {
proc_free_inum(ns->proc_inum);
+ exit_peripc_ns(ns);
kfree(ns);
return ERR_PTR(err);
}
@@ -111,6 +119,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
sem_exit_ns(ns);
msg_exit_ns(ns);
shm_exit_ns(ns);
+ exit_peripc_ns(ns);
atomic_dec(&nr_ipc_ns);
/*
diff --git a/ipc/util.c b/ipc/util.c
index 3ae17a4..8cb9949 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -71,6 +71,66 @@ struct ipc_proc_iface {
int (*show)(struct seq_file *, void *);
};
+/* allow others to piggyback on ipc_namespace */
+static DEFINE_MUTEX(peripc_mutex);
+static struct peripc_operations *peripc_ops;
+
+/*
+ * peripc_operations is a simplified pernet_operations:
+ * - allow only one entity to register
+ * - allow to register only at boot time (no modules)
+ * (these assumptions make the code much simpler)
+ */
+
+static int init_peripc_count;
+
+/* caller hold peripc_mutex */
+int init_peripc_ns(struct ipc_namespace *ns)
+{
+ int ret = 0;
+
+ if (peripc_ops && peripc_ops->init)
+ ret = peripc_ops->init(ns);
+ if (ret == 0)
+ init_peripc_count++;
+ return ret;
+}
+
+/* caller hold peripc_mutex */
+void exit_peripc_ns(struct ipc_namespace *ns)
+{
+ if (peripc_ops && peripc_ops->exit)
+ peripc_ops->exit(ns);
+ init_peripc_count--;
+}
+
+int register_peripc_ops(struct peripc_operations *ops)
+{
+ int ret = -EBUSY;
+
+ mutex_lock(&peripc_mutex);
+ /* must be first register, and only init ipc_namespace exists */
+ if (peripc_ops == NULL && init_peripc_count == 0) {
+ peripc_ops = ops;
+ ret = init_peripc_ns(&init_ipc_ns);
+ if (ret < 0)
+ peripc_ops = NULL;
+ }
+ mutex_unlock(&peripc_mutex);
+ return ret;
+}
+
+void unregister_peripc_ops(struct peripc_operations *ops)
+{
+ mutex_lock(&peripc_mutex);
+ /* sanity: be same as registered, and no other ipc ns (beyond init) */
+ BUG_ON(peripc_ops != ops);
+ BUG_ON(init_peripc_count != 1);
+ if (ops->exit)
+ exit_peripc_ns(&init_ipc_ns);
+ peripc_ops = NULL;
+ mutex_unlock(&peripc_mutex);
+}
static void ipc_memory_notifier(struct work_struct *work)
{
ipcns_notify(IPCNS_MEMCHANGED);
diff --git a/ipc/util.h b/ipc/util.h
index 59d78aa..daee0be 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -47,6 +47,9 @@ static inline void msg_exit_ns(struct ipc_namespace *ns) { }
static inline void shm_exit_ns(struct ipc_namespace *ns) { }
#endif
+int init_peripc_ns(struct ipc_namespace *ns);
+void exit_peripc_ns(struct ipc_namespace *ns);
+
struct ipc_rcu {
struct rcu_head rcu;
atomic_t refcount;
--
1.8.3.2
--
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