Re: [PATCH 5/2] xfs: refactor xlog_recover_buffer_pass1

[Brian Foster <bfoster@redhat.com>]

On Tue, Apr 28, 2020 at 10:05:50AM +0200, Christoph Hellwig wrote:
> Split out a xlog_add_buffer_cancelled helper which does the low-level
> manipulation of the buffer cancelation table, and in that helper call
> xlog_find_buffer_cancelled instead of open coding it.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_log_recover.c | 114 +++++++++++++++++++--------------------
>  1 file changed, 55 insertions(+), 59 deletions(-)
> 
> diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
> index fe4dad5b77a95..3bc61838266f1 100644
> --- a/fs/xfs/xfs_log_recover.c
> +++ b/fs/xfs/xfs_log_recover.c
...
> @@ -2045,6 +2015,32 @@ xlog_buf_readahead(
>  		xfs_buf_readahead(log->l_mp->m_ddev_targp, blkno, len, ops);
>  }
>  
> +/*
> + * Build up the table of buf cancel records so that we don't replay cancelled
> + * data in the second pass.
> + */
> +static int
> +xlog_recover_buffer_pass1(
> +	struct xlog			*log,
> +	struct xlog_recover_item	*item)
> +{
> +	struct xfs_buf_log_format	*bf = item->ri_buf[0].i_addr;
> +
> +	if (!xfs_buf_log_check_iovec(&item->ri_buf[0])) {
> +		xfs_err(log->l_mp, "bad buffer log item size (%d)",
> +				item->ri_buf[0].i_len);
> +		return -EFSCORRUPTED;
> +	}
> +
> +	if (!(bf->blf_flags & XFS_BLF_CANCEL))
> +		trace_xfs_log_recover_buf_not_cancel(log, bf);
> +	else if (xlog_add_buffer_cancelled(log, bf->blf_blkno, bf->blf_len))
> +		trace_xfs_log_recover_buf_cancel_add(log, bf);
> +	else
> +		trace_xfs_log_recover_buf_cancel_ref_inc(log, bf);

Nit, but the function call looks buried here. Also, the boolean return
seems like overkill if it's only used to control tracepoints (and
true/false for inc/ref isn't terribly intuitive anyways).

This looks cleaner to me if it's just:

	if (!XFS_BLF_CANCEL) {
		trace_xfs_log_recover_buf_not_cancel(log, bf);
		return 0;
	}

	xlog_add_buffer_cancelled(log, bf->blf_blkno, bf->blf_len);
	return 0;

... and let the helper invoke the buf_cancel tracepoints and return
void. Otherwise looks like a good cleanup to me.

Brian

> +	return 0;
> +}
> +
>  /*
>   * Perform recovery for a buffer full of inodes.  In these buffers, the only
>   * data which should be recovered is that which corresponds to the
> -- 
> 2.26.1
>