btrfs: Replace fs_info->readahead_workers workqueue with btrfs_workqueue.

Replace the fs_info->readahead_workers with the newly created
btrfs_workqueue.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Tested-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index 31c797c..9e01d36 100644
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -91,7 +91,8 @@
 };
 
 struct reada_machine_work {
-	struct btrfs_work	work;
+	struct btrfs_work_struct
+				work;
 	struct btrfs_fs_info	*fs_info;
 };
 
@@ -733,7 +734,7 @@
 
 }
 
-static void reada_start_machine_worker(struct btrfs_work *work)
+static void reada_start_machine_worker(struct btrfs_work_struct *work)
 {
 	struct reada_machine_work *rmw;
 	struct btrfs_fs_info *fs_info;
@@ -793,10 +794,10 @@
 		/* FIXME we cannot handle this properly right now */
 		BUG();
 	}
-	rmw->work.func = reada_start_machine_worker;
+	btrfs_init_work(&rmw->work, reada_start_machine_worker, NULL, NULL);
 	rmw->fs_info = fs_info;
 
-	btrfs_queue_worker(&fs_info->readahead_workers, &rmw->work);
+	btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
 }
 
 #ifdef DEBUG