aio: ifdef fields in mm_struct

->ioctx_lock and ->ioctx_list are used only under CONFIG_AIO.
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm_types.h

@@ -259,11 +259,10 @@ struct mm_struct {
 	unsigned long flags; /* Must use atomic bitops to access the bits */
 
 	struct core_state *core_state; /* coredumping support */
-
-	/* aio bits */
+#ifdef CONFIG_AIO
 	spinlock_t		ioctx_lock;
 	struct hlist_head	ioctx_list;
-
+#endif
 #ifdef CONFIG_MM_OWNER
 	/*
 	 * "owner" points to a task that is regarded as the canonical

kernel/fork.c

@@ -434,6 +434,14 @@ __setup("coredump_filter=", coredump_filter_setup);
 
 #include <linux/init_task.h>
 
+static void mm_init_aio(struct mm_struct *mm)
+{
+#ifdef CONFIG_AIO
+	spin_lock_init(&mm->ioctx_lock);
+	INIT_HLIST_HEAD(&mm->ioctx_list);
+#endif
+}
+
 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 {
 	atomic_set(&mm->mm_users, 1);
@@ -447,10 +455,9 @@ static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 	set_mm_counter(mm, file_rss, 0);
 	set_mm_counter(mm, anon_rss, 0);
 	spin_lock_init(&mm->page_table_lock);
-	spin_lock_init(&mm->ioctx_lock);
-	INIT_HLIST_HEAD(&mm->ioctx_list);
 	mm->free_area_cache = TASK_UNMAPPED_BASE;
 	mm->cached_hole_size = ~0UL;
+	mm_init_aio(mm);
 	mm_init_owner(mm, p);
 
 	if (likely(!mm_alloc_pgd(mm))) {