WorkStruct: Separate delayable and non-delayable events.

Separate delayable work items from non-delayable work items be splitting them
into a separate structure (delayed_work), which incorporates a work_struct and
the timer_list removed from work_struct.

The work_struct struct is huge, and this limits it's usefulness.  On a 64-bit
architecture it's nearly 100 bytes in size.  This reduces that by half for the
non-delayable type of event.

Signed-Off-By: David Howells <dhowells@redhat.com>
diff --git a/fs/aio.c b/fs/aio.c
index 9476659..11a1a71 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -227,7 +227,7 @@
 
 	INIT_LIST_HEAD(&ctx->active_reqs);
 	INIT_LIST_HEAD(&ctx->run_list);
-	INIT_WORK(&ctx->wq, aio_kick_handler, ctx);
+	INIT_DELAYED_WORK(&ctx->wq, aio_kick_handler, ctx);
 
 	if (aio_setup_ring(ctx) < 0)
 		goto out_freectx;
@@ -876,7 +876,7 @@
 	 * we're in a worker thread already, don't use queue_delayed_work,
 	 */
 	if (requeue)
-		queue_work(aio_wq, &ctx->wq);
+		queue_delayed_work(aio_wq, &ctx->wq, 0);
 }