Btrfs: delayed-inode: replace root args iff only fs_info used

This is the second independent patch of a larger project to cleanup
btrfs's internal usage of btrfs_root. Many functions take btrfs_root
only to grab the fs_info struct.

By requiring a root these functions cause programmer overhead. That
these functions can accept any valid root is not obvious until
inspection.

This patch reduces the specificity of such functions to accept the
fs_info directly.

These patches can be applied independently and thus are not being
submitted as a patch series. There should be about 26 patches by the
project's completion. Each patch will cleanup between 1 and 34 functions
apiece.  Each patch covers a single file's functions.

This patch affects the following function(s):
  1) btrfs_wq_run_delayed_node
Signed-off-by: Daniel Dressler <danieru.dressler@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.cz>

fs/btrfs/delayed-inode.c

@@ -1383,7 +1383,7 @@ static void btrfs_async_run_delayed_root(struct btrfs_work *work)
 
 
 static int btrfs_wq_run_delayed_node(struct btrfs_delayed_root *delayed_root,
-				     struct btrfs_root *root, int nr)
+				     struct btrfs_fs_info *fs_info, int nr)
 {
 	struct btrfs_async_delayed_work *async_work;
 
@@ -1399,7 +1399,7 @@ static int btrfs_wq_run_delayed_node(struct btrfs_delayed_root *delayed_root,
 			btrfs_async_run_delayed_root, NULL, NULL);
 	async_work->nr = nr;
 
-	btrfs_queue_work(root->fs_info->delayed_workers, &async_work->work);
+	btrfs_queue_work(fs_info->delayed_workers, &async_work->work);
 	return 0;
 }
 
@@ -1426,6 +1426,7 @@ static int could_end_wait(struct btrfs_delayed_root *delayed_root, int seq)
 void btrfs_balance_delayed_items(struct btrfs_root *root)
 {
 	struct btrfs_delayed_root *delayed_root;
+	struct btrfs_fs_info *fs_info = root->fs_info;
 
 	delayed_root = btrfs_get_delayed_root(root);
 
@@ -1438,7 +1439,7 @@ void btrfs_balance_delayed_items(struct btrfs_root *root)
 
 		seq = atomic_read(&delayed_root->items_seq);
 
-		ret = btrfs_wq_run_delayed_node(delayed_root, root, 0);
+		ret = btrfs_wq_run_delayed_node(delayed_root, fs_info, 0);
 		if (ret)
 			return;
 
@@ -1447,7 +1448,7 @@ void btrfs_balance_delayed_items(struct btrfs_root *root)
 		return;
 	}
 
-	btrfs_wq_run_delayed_node(delayed_root, root, BTRFS_DELAYED_BATCH);
+	btrfs_wq_run_delayed_node(delayed_root, fs_info, BTRFS_DELAYED_BATCH);
 }
 
 /* Will return 0 or -ENOMEM */