Re: [PATCH v4 4/7] btrfs: qgroup: Refactor btrfs_qgroup_trace_subtree_swap()

[David Sterba <dsterba@suse.cz>]

On Tue, Jan 15, 2019 at 04:16:01PM +0800, Qu Wenruo wrote:
> Refactor btrfs_qgroup_trace_subtree_swap() into
> qgroup_trace_subtree_swap(), which only needs two extent buffer and some
> other bool to control the behavior.
> 
> This provides the basis for later delayed subtree scan work.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>  fs/btrfs/qgroup.c | 78 ++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 57 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index ba30adac88a7..8fe6ebe9aef8 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -1994,6 +1994,60 @@ static int qgroup_trace_new_subtree_blocks(struct btrfs_trans_handle* trans,
>  	return ret;
>  }
>  
> +static int qgroup_trace_subtree_swap(struct btrfs_trans_handle *trans,
> +				struct extent_buffer *src_eb,
> +				struct extent_buffer *dst_eb,
> +				u64 last_snapshot, bool trace_leaf)
> +{
> +	struct btrfs_fs_info *fs_info = trans->fs_info;
> +	struct btrfs_path *dst_path = NULL;
> +	int level;
> +	int ret;
> +
> +	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
> +		return 0;
> +
> +	/* Wrong parameter order */
> +	if (btrfs_header_generation(src_eb) > btrfs_header_generation(dst_eb)) {
> +		btrfs_err_rl(fs_info,
> +		"%s: bad parameter order, src_gen=%llu dst_gen=%llu", __func__,
> +			     btrfs_header_generation(src_eb),
> +			     btrfs_header_generation(dst_eb));
> +		return -EUCLEAN;
> +	}
> +
> +	if (!extent_buffer_uptodate(src_eb) ||
> +	    !extent_buffer_uptodate(dst_eb)) {
> +		ret = -EINVAL;

Why is this EINVAL and not EIO or EUCLEAN? There's a similar pattern in
btrfs_qgroup_trace_subtree_swap that also does not look correct.

> +		goto out;
> +	}
> +
> +	level = btrfs_header_level(dst_eb);
> +	dst_path = btrfs_alloc_path();
> +	if (!dst_path) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +	/* For dst_path */
> +	extent_buffer_get(dst_eb);
> +	dst_path->nodes[level] = dst_eb;
> +	dst_path->slots[level] = 0;
> +	dst_path->locks[level] = 0;
> +
> +	/* Do the generation aware breadth-first search */
> +	ret = qgroup_trace_new_subtree_blocks(trans, src_eb, dst_path, level,
> +					      level, last_snapshot, trace_leaf);
> +	if (ret < 0)
> +		goto out;
> +	ret = 0;
> +
> +out:
> +	btrfs_free_path(dst_path);
> +	if (ret < 0)
> +		fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
> +	return ret;
> +}