fix do_sync_(read|write) to properly handle aio retries

diff -purN v2.6.12-rc6/fs/read_write.c uml-rc6/fs/read_write.c
@@ -203,6 +203,16 @@ Einval:
 	return -EINVAL;
 }
 
+static void wait_on_retry_sync_kiocb(struct kiocb *iocb)
+{
+	set_current_state(TASK_UNINTERRUPTIBLE);
+	if (!kiocbIsKicked(iocb))
+		schedule();
+	else
+		kiocbClearKicked(iocb);
+	__set_current_state(TASK_RUNNING);
+}
+
 ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
 {
 	struct kiocb kiocb;

@@ -210,7 +220,10 @@ ssize_t do_sync_read(struct file *filp, 
 
 	init_sync_kiocb(&kiocb, filp);
 	kiocb.ki_pos = *ppos;
-	ret = filp->f_op->aio_read(&kiocb, buf, len, kiocb.ki_pos);
+	while (-EIOCBRETRY == 
+		(ret = filp->f_op->aio_read(&kiocb, buf, len, kiocb.ki_pos)))
+		wait_on_retry_sync_kiocb(&kiocb);
+
 	if (-EIOCBQUEUED == ret)
 		ret = wait_on_sync_kiocb(&kiocb);
 	*ppos = kiocb.ki_pos;

@@ -258,7 +271,10 @@ ssize_t do_sync_write(struct file *filp,
 
 	init_sync_kiocb(&kiocb, filp);
 	kiocb.ki_pos = *ppos;
-	ret = filp->f_op->aio_write(&kiocb, buf, len, kiocb.ki_pos);
+	while (-EIOCBRETRY == 
+	       (ret = filp->f_op->aio_write(&kiocb, buf, len, kiocb.ki_pos)))
+		wait_on_retry_sync_kiocb(&kiocb);
+
 	if (-EIOCBQUEUED == ret)
 		ret = wait_on_sync_kiocb(&kiocb);
 	*ppos = kiocb.ki_pos;