aio: keep io_event in aio_kiocb

We want to separate forming the resulting io_event from putting it
into the ring buffer.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/aio.c

@@ -204,8 +204,7 @@ struct aio_kiocb {
 	struct kioctx		*ki_ctx;
 	kiocb_cancel_fn		*ki_cancel;
 
-	struct iocb __user	*ki_user_iocb;	/* user's aiocb */
-	__u64			ki_user_data;	/* user's data for completion */
+	struct io_event		ki_res;
 
 	struct list_head	ki_list;	/* the aio core uses this
 						 * for cancellation */
@@ -1084,15 +1083,6 @@ static inline void iocb_put(struct aio_kiocb *iocb)
 		iocb_destroy(iocb);
 }
 
-static void aio_fill_event(struct io_event *ev, struct aio_kiocb *iocb,
-			   long res, long res2)
-{
-	ev->obj = (u64)(unsigned long)iocb->ki_user_iocb;
-	ev->data = iocb->ki_user_data;
-	ev->res = res;
-	ev->res2 = res2;
-}
-
 /* aio_complete
  *	Called when the io request on the given iocb is complete.
  */
@@ -1104,6 +1094,8 @@ static void aio_complete(struct aio_kiocb *iocb, long res, long res2)
 	unsigned tail, pos, head;
 	unsigned long	flags;
 
+	iocb->ki_res.res = res;
+	iocb->ki_res.res2 = res2;
 	/*
 	 * Add a completion event to the ring buffer. Must be done holding
 	 * ctx->completion_lock to prevent other code from messing with the tail
@@ -1120,14 +1112,14 @@ static void aio_complete(struct aio_kiocb *iocb, long res, long res2)
 	ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
 	event = ev_page + pos % AIO_EVENTS_PER_PAGE;
 
-	aio_fill_event(event, iocb, res, res2);
+	*event = iocb->ki_res;
 
 	kunmap_atomic(ev_page);
 	flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
 
-	pr_debug("%p[%u]: %p: %p %Lx %lx %lx\n",
-		 ctx, tail, iocb, iocb->ki_user_iocb, iocb->ki_user_data,
-		 res, res2);
+	pr_debug("%p[%u]: %p: %p %Lx %Lx %Lx\n", ctx, tail, iocb,
+		 (void __user *)(unsigned long)iocb->ki_res.obj,
+		 iocb->ki_res.data, iocb->ki_res.res, iocb->ki_res.res2);
 
 	/* after flagging the request as done, we
 	 * must never even look at it again
@@ -1844,8 +1836,10 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 		goto out_put_req;
 	}
 
-	req->ki_user_iocb = user_iocb;
-	req->ki_user_data = iocb->aio_data;
+	req->ki_res.obj = (u64)(unsigned long)user_iocb;
+	req->ki_res.data = iocb->aio_data;
+	req->ki_res.res = 0;
+	req->ki_res.res2 = 0;
 
 	switch (iocb->aio_lio_opcode) {
 	case IOCB_CMD_PREAD:
@@ -2019,6 +2013,7 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
 	struct aio_kiocb *kiocb;
 	int ret = -EINVAL;
 	u32 key;
+	u64 obj = (u64)(unsigned long)iocb;
 
 	if (unlikely(get_user(key, &iocb->aio_key)))
 		return -EFAULT;
@@ -2032,7 +2027,7 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
 	spin_lock_irq(&ctx->ctx_lock);
 	/* TODO: use a hash or array, this sucks. */
 	list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) {
-		if (kiocb->ki_user_iocb == iocb) {
+		if (kiocb->ki_res.obj == obj) {
 			ret = kiocb->ki_cancel(&kiocb->rw);
 			list_del_init(&kiocb->ki_list);
 			break;