trimming task_work: kill ->data

get rid of the only user of ->data; this is _not_ the final variant - in the
end we'll have task_work and rcu_head identical and just use cred->rcu,
at which point the separate allocation will be gone completely.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/task_work.h

@@ -10,14 +10,12 @@ typedef void (*task_work_func_t)(struct task_work *);
 struct task_work {
 	struct hlist_node hlist;
 	task_work_func_t func;
-	void *data;
 };
 
 static inline void
-init_task_work(struct task_work *twork, task_work_func_t func, void *data)
+init_task_work(struct task_work *twork, task_work_func_t func)
 {
 	twork->func = func;
-	twork->data = data;
 }
 
 int task_work_add(struct task_struct *task, struct task_work *twork, bool);

kernel/irq/manage.c

@@ -830,7 +830,7 @@ static int irq_thread(void *data)
 
 	sched_setscheduler(current, SCHED_FIFO, &param);
 
-	init_task_work(&on_exit_work, irq_thread_dtor, NULL);
+	init_task_work(&on_exit_work, irq_thread_dtor);
 	task_work_add(current, &on_exit_work, false);
 
 	while (!irq_wait_for_interrupt(action)) {

security/keys/internal.h

@@ -148,6 +148,10 @@ extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
 #define KEY_LOOKUP_PARTIAL	0x02
 #define KEY_LOOKUP_FOR_UNLINK	0x04
 
+struct kludge {	/* this will die off very soon */
+	struct task_work twork;
+	struct cred *cred;
+};
 extern long join_session_keyring(const char *name);
 extern void key_change_session_keyring(struct task_work *twork);
 

security/keys/keyctl.c

@@ -1456,7 +1456,8 @@ long keyctl_session_to_parent(void)
 {
 	struct task_struct *me, *parent;
 	const struct cred *mycred, *pcred;
-	struct task_work *newwork, *oldwork;
+	struct kludge *newwork;
+	struct task_work *oldwork;
 	key_ref_t keyring_r;
 	struct cred *cred;
 	int ret;
@@ -1466,7 +1467,7 @@ long keyctl_session_to_parent(void)
 		return PTR_ERR(keyring_r);
 
 	ret = -ENOMEM;
-	newwork = kmalloc(sizeof(struct task_work), GFP_KERNEL);
+	newwork = kmalloc(sizeof(struct kludge), GFP_KERNEL);
 	if (!newwork)
 		goto error_keyring;
 
@@ -1478,7 +1479,8 @@ long keyctl_session_to_parent(void)
 		goto error_newwork;
 
 	cred->tgcred->session_keyring = key_ref_to_ptr(keyring_r);
-	init_task_work(newwork, key_change_session_keyring, cred);
+	init_task_work(&newwork->twork, key_change_session_keyring);
+	newwork->cred = cred;
 
 	me = current;
 	rcu_read_lock();
@@ -1527,18 +1529,18 @@ long keyctl_session_to_parent(void)
 
 	/* the replacement session keyring is applied just prior to userspace
 	 * restarting */
-	ret = task_work_add(parent, newwork, true);
+	ret = task_work_add(parent, &newwork->twork, true);
 	if (!ret)
 		newwork = NULL;
 unlock:
 	write_unlock_irq(&tasklist_lock);
 	rcu_read_unlock();
 	if (oldwork) {
-		put_cred(oldwork->data);
+		put_cred(container_of(oldwork, struct kludge, twork)->cred);
 		kfree(oldwork);
 	}
 	if (newwork) {
-		put_cred(newwork->data);
+		put_cred(newwork->cred);
 		kfree(newwork);
 	}
 	return ret;

security/keys/process_keys.c

@@ -837,9 +837,10 @@ long join_session_keyring(const char *name)
 void key_change_session_keyring(struct task_work *twork)
 {
 	const struct cred *old = current_cred();
-	struct cred *new = twork->data;
+	struct kludge *p = container_of(twork, struct kludge, twork);
+	struct cred *new = p->cred;
 
-	kfree(twork);
+	kfree(p);
 	if (unlikely(current->flags & PF_EXITING)) {
 		put_cred(new);
 		return;