[AIO] fix io_wait

  When an application is mixing sync and async IO it ends up crashing
later on in the sync path when calling lock_page_slow as the io_wait
queue has been set to NULL in a previous AIO request.

  Therefore after the retry method has been called the task io_wait
queue should be reset to the default queue.

  This patch applies over Suparna's wait-bit patchset:

	- modify-wait-bit-action-args
	- lock_page_wait
	- init-wait-bit-key
	- tsk-default-io-wait
	- aio-wait-bit
	- aio-wait-page

and could be folded into aio-wait-bit.

Signed-off-by: Sébastien Dugué <sebastien.dugue@bull.net>
Signed-off-by: Benjamin LaHaise <bcrl@linux.intel.com>
diff -purN --exclude=description 78_fs_aio_write/fs/aio.c 79_fix-io_wait/fs/aio.c
--- 78_fs_aio_write/fs/aio.c	2005-08-08 17:16:03.000000000 -0400
+++ 79_fix-io_wait/fs/aio.c	2005-08-08 17:16:06.000000000 -0400
@@ -733,7 +733,7 @@ static ssize_t aio_run_iocb(struct kiocb
 	BUG_ON(!is_sync_wait(current->io_wait));
 	current->io_wait = &iocb->ki_wait.wait;
 	ret = retry(iocb);
-	current->io_wait = NULL;
+	current->io_wait = &current->__wait.wait;
 
 	if (-EIOCBRETRY != ret) {
  		if (-EIOCBQUEUED != ret) {