coredump: turn mm->core_startup_done into the pointer to struct core_state

mm->core_startup_done points to "struct completion startup_done" allocated
on the coredump_wait()'s stack.  Introduce the new structure, core_state,
which holds this "struct completion".  This way we can add more info
visible to the threads participating in coredump without enlarging
mm_struct.

No changes in affected .o files.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/exec.c

@@ -1597,13 +1597,13 @@ static int coredump_wait(int exit_code)
 {
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->mm;
-	struct completion startup_done;
+	struct core_state core_state;
 	struct completion *vfork_done;
 	int core_waiters;
 
 	init_completion(&mm->core_done);
-	init_completion(&startup_done);
-	mm->core_startup_done = &startup_done;
+	init_completion(&core_state.startup);
+	mm->core_state = &core_state;
 
 	core_waiters = zap_threads(tsk, mm, exit_code);
 	up_write(&mm->mmap_sem);
@@ -1622,7 +1622,7 @@ static int coredump_wait(int exit_code)
 	}
 
 	if (core_waiters)
-		wait_for_completion(&startup_done);
+		wait_for_completion(&core_state.startup);
 fail:
 	BUG_ON(mm->core_waiters);
 	return core_waiters;

include/linux/mm_types.h

@@ -159,6 +159,10 @@ struct vm_area_struct {
 #endif
 };
 
+struct core_state {
+	struct completion startup;
+};
+
 struct mm_struct {
 	struct vm_area_struct * mmap;		/* list of VMAs */
 	struct rb_root mm_rb;
@@ -220,7 +224,8 @@ struct mm_struct {
 	unsigned long flags; /* Must use atomic bitops to access the bits */
 
 	/* coredumping support */
-	struct completion *core_startup_done, core_done;
+	struct core_state *core_state;
+	struct completion core_done;
 
 	/* aio bits */
 	rwlock_t		ioctx_list_lock;	/* aio lock */

kernel/exit.c

@@ -680,7 +680,7 @@ static void exit_mm(struct task_struct * tsk)
 		up_read(&mm->mmap_sem);
 		down_write(&mm->mmap_sem);
 		if (!--mm->core_waiters)
-			complete(mm->core_startup_done);
+			complete(&mm->core_state->startup);
 		up_write(&mm->mmap_sem);
 
 		wait_for_completion(&mm->core_done);