diff --git a/fs/aio.c b/fs/aio.c
index 20bb919eb1958e6e4dbbf96f6f04812a23983a24..e7cd40b626b7f3bd06446e7d01da5c7aaab623de 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -937,28 +937,19 @@ int fastcall aio_complete(struct kiocb *iocb, long res, long res2)
 	unsigned long	tail;
 	int		ret;
 
-	/* Special case handling for sync iocbs: events go directly
-	 * into the iocb for fast handling.  Note that this will not 
-	 * work if we allow sync kiocbs to be cancelled. in which
-	 * case the usage count checks will have to move under ctx_lock
-	 * for all cases.
+	/*
+	 * Special case handling for sync iocbs:
+	 *  - events go directly into the iocb for fast handling
+	 *  - the sync task with the iocb in its stack holds the single iocb
+	 *    ref, no other paths have a way to get another ref
+	 *  - the sync task helpfully left a reference to itself in the iocb
 	 */
 	if (is_sync_kiocb(iocb)) {
-		int ret;
-
+		BUG_ON(iocb->ki_users != 1);
 		iocb->ki_user_data = res;
-		if (iocb->ki_users == 1) {
-			iocb->ki_users = 0;
-			ret = 1;
-		} else {
-			spin_lock_irq(&ctx->ctx_lock);
-			iocb->ki_users--;
-			ret = (0 == iocb->ki_users);
-			spin_unlock_irq(&ctx->ctx_lock);
-		}
-		/* sync iocbs put the task here for us */
+		iocb->ki_users = 0;
 		wake_up_process(iocb->ki_obj.tsk);
-		return ret;
+		return 1;
 	}
 
 	info = &ctx->ring_info;
diff --git a/include/linux/aio.h b/include/linux/aio.h
index 403d71dcb7c818beb2b43101af33d6133f6d5622..9e0ae87112763035192a6301a6aa8a3ab2e179c9 100644
--- a/include/linux/aio.h
+++ b/include/linux/aio.h
@@ -124,7 +124,7 @@ struct kiocb {
 		(x)->ki_users = 1;			\
 		(x)->ki_key = KIOCB_SYNC_KEY;		\
 		(x)->ki_filp = (filp);			\
-		(x)->ki_ctx = &tsk->active_mm->default_kioctx;	\
+		(x)->ki_ctx = NULL;			\
 		(x)->ki_cancel = NULL;			\
 		(x)->ki_dtor = NULL;			\
 		(x)->ki_obj.tsk = tsk;			\
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 68ab5f2ab9cdb35bd8249f03b7e3b5b0bc54e443..dcfd2ecccb5d63dbcb2718a2f3e827aef9d68a23 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -51,7 +51,6 @@
 	.page_table_lock =  SPIN_LOCK_UNLOCKED, 		\
 	.mmlist		= LIST_HEAD_INIT(name.mmlist),		\
 	.cpu_vm_mask	= CPU_MASK_ALL,				\
-	.default_kioctx = INIT_KIOCTX(name.default_kioctx, name),	\
 }
 
 #define INIT_SIGNALS(sig) {	\
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 41df813957190adecba9015a4d17b7c13524f5f8..2038bd27b0413c74bcb66290adc3cfe33b5c0fd3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -357,7 +357,6 @@ struct mm_struct {
 	/* aio bits */
 	rwlock_t		ioctx_list_lock;
 	struct kioctx		*ioctx_list;
-	struct kioctx		default_kioctx;
 };
 
 struct sighand_struct {
diff --git a/kernel/fork.c b/kernel/fork.c
index 2c70c9cdf5dcf0c3f5955a467c5e47b68a77463b..e0d0b77343f880b60d8551338c26e05420c47291 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -323,7 +323,6 @@ static struct mm_struct * mm_init(struct mm_struct * mm)
 	spin_lock_init(&mm->page_table_lock);
 	rwlock_init(&mm->ioctx_list_lock);
 	mm->ioctx_list = NULL;
-	mm->default_kioctx = (struct kioctx)INIT_KIOCTX(mm->default_kioctx, *mm);
 	mm->free_area_cache = TASK_UNMAPPED_BASE;
 	mm->cached_hole_size = ~0UL;