Btrfs: balance delayed inode updates

While trying to reproduce a delayed ref problem I noticed the box kept falling
over using all 80gb of my ram with btrfs_inode's and btrfs_delayed_node's.
Turns out this is because we only throttle delayed inode updates in
btrfs_dirty_inode, which doesn't actually get called that often, especially when
all you are doing is creating a bunch of files.  So balance delayed inode
updates everytime we create a new inode.  With this patch we no longer use up
all of our ram with delayed inode updates.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>

fs/btrfs/inode.c

@@ -5795,6 +5795,7 @@ static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
 	}
 out_unlock:
 	btrfs_end_transaction(trans, root);
+	btrfs_balance_delayed_items(root);
 	btrfs_btree_balance_dirty(root);
 	if (drop_inode) {
 		inode_dec_link_count(inode);
@@ -5868,6 +5869,7 @@ out_unlock:
 		inode_dec_link_count(inode);
 		iput(inode);
 	}
+	btrfs_balance_delayed_items(root);
 	btrfs_btree_balance_dirty(root);
 	return err;
 }
@@ -5926,6 +5928,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
 	}
 
 	btrfs_end_transaction(trans, root);
+	btrfs_balance_delayed_items(root);
 fail:
 	if (drop_inode) {
 		inode_dec_link_count(inode);
@@ -5992,6 +5995,7 @@ out_fail:
 	btrfs_end_transaction(trans, root);
 	if (drop_on_err)
 		iput(inode);
+	btrfs_balance_delayed_items(root);
 	btrfs_btree_balance_dirty(root);
 	return err;
 }