[PATCH 1/2] Add ipc_namespace to struct sem_undo_list

[Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

Checkpoint/Restart needs to have a pointer to the ipc_namespace that the
sem_undo_list applies to in order to properly bring up and tear down
the object hash.  This patch adds a pointer to the namespace to the list
structure, as well as breaks out the allocation of the undo list to a
separate function (which is needed in a later C/R patch anyway).

Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 include/linux/sem.h |    2 ++
 ipc/sem.c           |   30 +++++++++++++++++++++---------
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/include/linux/sem.h b/include/linux/sem.h
index 8a4adbe..8cf9636 100644
--- a/include/linux/sem.h
+++ b/include/linux/sem.h
@@ -127,12 +127,14 @@ struct sem_undo {
 	short *			semadj;		/* array of adjustments, one per semaphore */
 };
 
+struct ipc_namespace;
 /* sem_undo_list controls shared access to the list of sem_undo structures
  * that may be shared among all a CLONE_SYSVSEM task group.
  */ 
 struct sem_undo_list {
 	atomic_t		refcnt;
 	spinlock_t		lock;
+	struct ipc_namespace	*ipc_ns;
 	struct list_head	list_proc;
 };
 
diff --git a/ipc/sem.c b/ipc/sem.c
index 37da85e..e439b73 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -983,6 +983,21 @@ asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg)
 SYSCALL_ALIAS(sys_semctl, SyS_semctl);
 #endif
 
+static struct sem_undo_list *alloc_undo_list(struct ipc_namespace *ipc_ns)
+{
+	struct sem_undo_list *undo_list;
+
+	undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
+	if (undo_list == NULL)
+		return NULL;
+	spin_lock_init(&undo_list->lock);
+	atomic_set(&undo_list->refcnt, 1);
+	INIT_LIST_HEAD(&undo_list->list_proc);
+	undo_list->ipc_ns = ipc_ns;
+
+	return undo_list;
+}
+
 /* If the task doesn't already have a undo_list, then allocate one
  * here.  We guarantee there is only one thread using this undo list,
  * and current is THE ONE
@@ -994,19 +1009,16 @@ SYSCALL_ALIAS(sys_semctl, SyS_semctl);
  *
  * This can block, so callers must hold no locks.
  */
-static inline int get_undo_list(struct sem_undo_list **undo_listp)
+static inline int get_undo_list(struct sem_undo_list **undo_listp,
+				struct ipc_namespace *ipc_ns)
 {
 	struct sem_undo_list *undo_list;
 
 	undo_list = current->sysvsem.undo_list;
 	if (!undo_list) {
-		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
-		if (undo_list == NULL)
+		undo_list = alloc_undo_list(ipc_ns);
+		if (!undo_list)
 			return -ENOMEM;
-		spin_lock_init(&undo_list->lock);
-		atomic_set(&undo_list->refcnt, 1);
-		INIT_LIST_HEAD(&undo_list->list_proc);
-
 		current->sysvsem.undo_list = undo_list;
 	}
 	*undo_listp = undo_list;
@@ -1057,7 +1069,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
 	int nsems;
 	int error;
 
-	error = get_undo_list(&ulp);
+	error = get_undo_list(&ulp, ns);
 	if (error)
 		return ERR_PTR(error);
 
@@ -1328,7 +1340,7 @@ int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
 	int error;
 
 	if (clone_flags & CLONE_SYSVSEM) {
-		error = get_undo_list(&undo_list);
+		error = get_undo_list(&undo_list, tsk->nsproxy->ipc_ns);
 		if (error)
 			return error;
 		atomic_inc(&undo_list->refcnt);
-- 
1.7.1.1