Re: [PATCH v2] Btrfs: fix unexpected balance crash due to BUG_ON

[David Sterba <dsterba@suse.cz>]

On Mon, Jul 11, 2016 at 10:21:35AM -0700, Liu Bo wrote:
> +		}
>  
>  		trans = btrfs_start_transaction(dev_root, 0);
> -		BUG_ON(IS_ERR(trans));
> +		if (IS_ERR(trans)) {
> +			ret = PTR_ERR(trans);
> +			btrfs_info(fs_info,

This could be btrfs_info_in_rcu for clarity (using the rcu_string)

> +		 "%s:%d fails on btrfs_start_transaction() right after shrinking devivce %s (original size is %llu new size is %llu",
> +				   __func__, __LINE__,

I'm not sure the function and line is necessary, we don't use it
anywhere else. I'd suggest a slight modification:

		"resize: unable to start transaction after shrinking device %s (error %d), old size %llu, new size %llu"

> +				   rcu_str_deref(device->name), old_size,
> +				   old_size - size_to_free);
> +			goto error;
> +		}
>  
>  		ret = btrfs_grow_device(trans, device, old_size);
> -		BUG_ON(ret);
> +		if (ret) {
> +			btrfs_end_transaction(trans, dev_root);
> +			/* btrfs_grow_device never returns ret > 0 */
> +			WARN_ON(ret > 0);
> +			btrfs_info(fs_info,
> +		 "%s:%d fails on btrfs_grow_device() right after shrinking devivce %s (original size is %llu new size is %llu",

"resize: unable to grow device after shrinking device %s (error %d), old size %llu, new size %llu"