Re: [PATCH 6/8] xfs: simplify the xlog_write_partial calling conventions

[Brian Foster <bfoster@redhat.com>]

On Wed, Jun 16, 2021 at 06:32:10PM +0200, Christoph Hellwig wrote:
> Lift the iteration to the next log_vec into the callers, and drop
> the pointless log argument that can be trivially derived.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---

Heh, I actually had patches in my local tree very similar to these last
few to fix up the xlog_write() iteration logic. Nice cleanup overall:

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/xfs_log.c | 38 +++++++++++++++-----------------------
>  1 file changed, 15 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 5d55d4fff63035..4afa8ff1a82076 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -2232,14 +2232,11 @@ xlog_write_get_more_iclog_space(
>  /*
>   * Write log vectors into a single iclog which is smaller than the current chain
>   * length. We write until we cannot fit a full record into the remaining space
> - * and then stop. We return the log vector that is to be written that cannot
> - * wholly fit in the iclog.
> + * and then stop.
>   */
> -static struct xfs_log_vec *
> +static int
>  xlog_write_partial(
> -	struct xlog		*log,
> -	struct list_head	*lv_chain,
> -	struct xfs_log_vec	*log_vector,
> +	struct xfs_log_vec	*lv,
>  	struct xlog_ticket	*ticket,
>  	struct xlog_in_core	**iclogp,
>  	uint32_t		*log_offset,
> @@ -2248,8 +2245,7 @@ xlog_write_partial(
>  	uint32_t		*data_cnt)
>  {
>  	struct xlog_in_core	*iclog = *iclogp;
> -	struct xfs_log_vec	*lv = log_vector;
> -	struct xfs_log_iovec	*reg;
> +	struct xlog		*log = iclog->ic_log;
>  	struct xlog_op_header	*ophdr;
>  	int			index = 0;
>  	uint32_t		rlen;
> @@ -2257,9 +2253,8 @@ xlog_write_partial(
>  
>  	/* walk the logvec, copying until we run out of space in the iclog */
>  	for (index = 0; index < lv->lv_niovecs; index++) {
> -		uint32_t	reg_offset = 0;
> -
> -		reg = &lv->lv_iovecp[index];
> +		struct xfs_log_iovec	*reg = &lv->lv_iovecp[index];
> +		uint32_t		reg_offset = 0;
>  
>  		/*
>  		 * The first region of a continuation must have a non-zero
> @@ -2278,7 +2273,7 @@ xlog_write_partial(
>  					&iclog, log_offset, *len, record_cnt,
>  					data_cnt);
>  			if (error)
> -				return ERR_PTR(error);
> +				return error;
>  		}
>  
>  		ophdr = reg->i_addr;
> @@ -2329,7 +2324,7 @@ xlog_write_partial(
>  					*len + sizeof(struct xlog_op_header),
>  					record_cnt, data_cnt);
>  			if (error)
> -				return ERR_PTR(error);
> +				return error;
>  
>  			ophdr = iclog->ic_datap + *log_offset;
>  			ophdr->oh_tid = cpu_to_be32(ticket->t_tid);
> @@ -2365,10 +2360,7 @@ xlog_write_partial(
>  	 * the caller so it can go back to fast path copying.
>  	 */
>  	*iclogp = iclog;
> -	lv = list_next_entry(lv, lv_list);
> -	if (list_entry_is_head(lv, lv_chain, lv_list))
> -		return NULL;
> -	return lv;
> +	return 0;
>  }
>  
>  /*
> @@ -2450,13 +2442,13 @@ xlog_write(
>  		if (!lv)
>  			break;
>  
> -		lv = xlog_write_partial(log, lv_chain, lv, ticket, &iclog,
> -					&log_offset, &len, &record_cnt,
> -					&data_cnt);
> -		if (IS_ERR_OR_NULL(lv)) {
> -			error = PTR_ERR_OR_ZERO(lv);
> +		error = xlog_write_partial(lv, ticket, &iclog, &log_offset,
> +					   &len, &record_cnt, &data_cnt);
> +		if (error)
> +			break;
> +		lv = list_next_entry(lv, lv_list);
> +		if (list_entry_is_head(lv, lv_chain, lv_list))
>  			break;
> -		}
>  	}
>  	ASSERT((len == 0 && !lv) || error);
>  
> -- 
> 2.30.2
>