Re: [PATCH 09/16] xfs: pass lv chain length into xlog_write()

[Chandan Babu R <chandan.babu@oracle.com>]

On 19 Nov 2021 at 04:43, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> The caller of xlog_write() usually has a close accounting of the
> aggregated vector length contained in the log vector chain passed to
> xlog_write(). There is no need to iterate the chain to calculate he
> length of the data in xlog_write_calculate_len() if the caller is
> already iterating that chain to build it.
>
> Passing in the vector length avoids doing an extra chain iteration,
> which can be a significant amount of work given that large CIL
> commits can have hundreds of thousands of vectors attached to the
> chain.
>

Looks good.

Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>

> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_log.c      | 35 +++++------------------------------
>  fs/xfs/xfs_log_cil.c  | 25 +++++++++++++++++--------
>  fs/xfs/xfs_log_priv.h |  2 +-
>  3 files changed, 23 insertions(+), 39 deletions(-)
>
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index bd2e50804cb4..76d5a743f6fb 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -972,7 +972,8 @@ xlog_write_unmount_record(
>  	/* account for space used by record data */
>  	ticket->t_curr_res -= sizeof(unmount_rec);
>  
> -	return xlog_write(log, NULL, &vec, ticket, XLOG_UNMOUNT_TRANS);
> +	return xlog_write(log, NULL, &vec, ticket, XLOG_UNMOUNT_TRANS,
> +			reg.i_len);
>  }
>  
>  /*
> @@ -2223,32 +2224,6 @@ xlog_print_trans(
>  	}
>  }
>  
> -/*
> - * Calculate the potential space needed by the log vector. All regions contain
> - * their own opheaders and they are accounted for in region space so we don't
> - * need to add them to the vector length here.
> - */
> -static int
> -xlog_write_calc_vec_length(
> -	struct xlog_ticket	*ticket,
> -	struct xfs_log_vec	*log_vector,
> -	uint			optype)
> -{
> -	struct xfs_log_vec	*lv;
> -	int			len = 0;
> -	int			i;
> -
> -	for (lv = log_vector; lv; lv = lv->lv_next) {
> -		/* we don't write ordered log vectors */
> -		if (lv->lv_buf_len == XFS_LOG_VEC_ORDERED)
> -			continue;
> -
> -		for (i = 0; i < lv->lv_niovecs; i++)
> -			len += lv->lv_iovecp[i].i_len;
> -	}
> -	return len;
> -}
> -
>  static xlog_op_header_t *
>  xlog_write_setup_ophdr(
>  	struct xlog_op_header	*ophdr,
> @@ -2402,13 +2377,14 @@ xlog_write(
>  	struct xfs_cil_ctx	*ctx,
>  	struct xfs_log_vec	*log_vector,
>  	struct xlog_ticket	*ticket,
> -	uint			optype)
> +	uint			optype,
> +	uint32_t		len)
> +
>  {
>  	struct xlog_in_core	*iclog = NULL;
>  	struct xfs_log_vec	*lv = log_vector;
>  	struct xfs_log_iovec	*vecp = lv->lv_iovecp;
>  	int			index = 0;
> -	int			len;
>  	int			partial_copy = 0;
>  	int			partial_copy_len = 0;
>  	int			contwr = 0;
> @@ -2423,7 +2399,6 @@ xlog_write(
>  		xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
>  	}
>  
> -	len = xlog_write_calc_vec_length(ticket, log_vector, optype);
>  	while (lv && (!lv->lv_niovecs || index < lv->lv_niovecs)) {
>  		void		*ptr;
>  		int		log_offset;
> diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
> index 90a0e9b9d3e0..99ef13f1b248 100644
> --- a/fs/xfs/xfs_log_cil.c
> +++ b/fs/xfs/xfs_log_cil.c
> @@ -791,7 +791,8 @@ xlog_cil_order_write(
>  static int
>  xlog_cil_write_chain(
>  	struct xfs_cil_ctx	*ctx,
> -	struct xfs_log_vec	*chain)
> +	struct xfs_log_vec	*chain,
> +	uint32_t		chain_len)
>  {
>  	struct xlog		*log = ctx->cil->xc_log;
>  	int			error;
> @@ -799,7 +800,8 @@ xlog_cil_write_chain(
>  	error = xlog_cil_order_write(ctx->cil, ctx->sequence, _START_RECORD);
>  	if (error)
>  		return error;
> -	return xlog_write(log, ctx, chain, ctx->ticket, XLOG_START_TRANS);
> +	return xlog_write(log, ctx, chain, ctx->ticket, XLOG_START_TRANS,
> +			chain_len);
>  }
>  
>  /*
> @@ -838,7 +840,8 @@ xlog_cil_write_commit_record(
>  
>  	/* account for space used by record data */
>  	ctx->ticket->t_curr_res -= reg.i_len;
> -	error = xlog_write(log, ctx, &vec, ctx->ticket, XLOG_COMMIT_TRANS);
> +	error = xlog_write(log, ctx, &vec, ctx->ticket, XLOG_COMMIT_TRANS,
> +			reg.i_len);
>  	if (error)
>  		xfs_force_shutdown(log->l_mp, SHUTDOWN_LOG_IO_ERROR);
>  	return error;
> @@ -901,11 +904,12 @@ xlog_cil_build_trans_hdr(
>  				sizeof(struct xfs_trans_header);
>  	hdr->lhdr[1].i_type = XLOG_REG_TYPE_TRANSHDR;
>  
> -	tic->t_curr_res -= hdr->lhdr[0].i_len + hdr->lhdr[1].i_len;
> -
>  	lvhdr->lv_niovecs = 2;
>  	lvhdr->lv_iovecp = &hdr->lhdr[0];
> +	lvhdr->lv_bytes = hdr->lhdr[0].i_len + hdr->lhdr[1].i_len;
>  	lvhdr->lv_next = ctx->lv_chain;
> +
> +	tic->t_curr_res -= lvhdr->lv_bytes;
>  }
>  
>  /*
> @@ -932,7 +936,8 @@ xlog_cil_push_work(
>  	struct xlog		*log = cil->xc_log;
>  	struct xfs_log_vec	*lv;
>  	struct xfs_cil_ctx	*new_ctx;
> -	int			num_iovecs;
> +	int			num_iovecs = 0;
> +	int			num_bytes = 0;
>  	int			error = 0;
>  	struct xlog_cil_trans_hdr thdr;
>  	struct xfs_log_vec	lvhdr = { NULL };
> @@ -1033,7 +1038,6 @@ xlog_cil_push_work(
>  	 * by the flush lock.
>  	 */
>  	lv = NULL;
> -	num_iovecs = 0;
>  	while (!list_empty(&cil->xc_cil)) {
>  		struct xfs_log_item	*item;
>  
> @@ -1047,6 +1051,10 @@ xlog_cil_push_work(
>  		lv = item->li_lv;
>  		item->li_lv = NULL;
>  		num_iovecs += lv->lv_niovecs;
> +
> +		/* we don't write ordered log vectors */
> +		if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED)
> +			num_bytes += lv->lv_bytes;
>  	}
>  
>  	/*
> @@ -1085,6 +1093,7 @@ xlog_cil_push_work(
>  	 * transaction header here as it is not accounted for in xlog_write().
>  	 */
>  	xlog_cil_build_trans_hdr(ctx, &thdr, &lvhdr, num_iovecs);
> +	num_bytes += lvhdr.lv_bytes;
>  
>  	/*
>  	 * Before we format and submit the first iclog, we have to ensure that
> @@ -1092,7 +1101,7 @@ xlog_cil_push_work(
>  	 */
>  	wait_for_completion(&bdev_flush);
>  
> -	error = xlog_cil_write_chain(ctx, &lvhdr);
> +	error = xlog_cil_write_chain(ctx, &lvhdr, num_bytes);
>  	if (error)
>  		goto out_abort_free_ticket;
>  
> diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
> index 47165c4d2a49..56df86d62430 100644
> --- a/fs/xfs/xfs_log_priv.h
> +++ b/fs/xfs/xfs_log_priv.h
> @@ -492,7 +492,7 @@ void	xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket);
>  void	xlog_print_trans(struct xfs_trans *);
>  int	xlog_write(struct xlog *log, struct xfs_cil_ctx *ctx,
>  		struct xfs_log_vec *log_vector, struct xlog_ticket *tic,
> -		uint optype);
> +		uint optype, uint32_t len);
>  void	xfs_log_ticket_ungrant(struct xlog *log, struct xlog_ticket *ticket);
>  void	xfs_log_ticket_regrant(struct xlog *log, struct xlog_ticket *ticket);


-- 
chandan