5 files changed, 10 insertions, 22 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 20bb919eb195..e7cd40b626b7 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 403d71dcb7c8..9e0ae8711276 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 68ab5f2ab9cd..dcfd2ecccb5d 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 41df81395719..2038bd27b041 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 2c70c9cdf5dc..e0d0b77343f8 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;