Re: [PATCH 1/5] xfs: log stripe roundoff is a property of the log

[Brian Foster <bfoster@redhat.com>]

On Thu, Jan 28, 2021 at 03:41:50PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> We don't need to look at the xfs_mount and superblock every time we
> need to do an iclog roundoff calculation. The property is fixed for
> the life of the log, so store the roundoff in the log at mount time
> and use that everywhere.
> 
> On a debug build:
> 
> $ size fs/xfs/xfs_log.o.*
>    text	   data	    bss	    dec	    hex	filename
>   27360	    560	      8	  27928	   6d18	fs/xfs/xfs_log.o.orig
>   27219	    560	      8	  27787	   6c8b	fs/xfs/xfs_log.o.patched
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_log_format.h |  3 --
>  fs/xfs/xfs_log.c               | 60 +++++++++++++++-------------------
>  fs/xfs/xfs_log_priv.h          |  2 ++
>  3 files changed, 28 insertions(+), 37 deletions(-)
> 
...
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 58699881c100..c5f507c24577 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -1400,6 +1400,12 @@ xlog_alloc_log(
>  	xlog_assign_atomic_lsn(&log->l_last_sync_lsn, 1, 0);
>  	log->l_curr_cycle  = 1;	    /* 0 is bad since this is initial value */
>  
> +	/* roundoff padding for transaction data and one for commit record */

I don't follow this comment. What do you mean by "... and one for commit
record?"

> +	if (xfs_sb_version_haslogv2(&mp->m_sb) && mp->m_sb.sb_logsunit > 1)
> +		log->l_iclog_roundoff = mp->m_sb.sb_logsunit;
> +	else
> +		log->l_iclog_roundoff = BBSIZE;
> +
>  	xlog_grant_head_init(&log->l_reserve_head);
>  	xlog_grant_head_init(&log->l_write_head);
>  
...
> @@ -3485,18 +3475,20 @@ xfs_log_calc_unit_res(
>  	/* for commit-rec LR header - note: padding will subsume the ophdr */
>  	unit_bytes += log->l_iclog_hsize;
>  
> -	/* for roundoff padding for transaction data and one for commit record */
> -	if (xfs_sb_version_haslogv2(&mp->m_sb) && mp->m_sb.sb_logsunit > 1) {
> -		/* log su roundoff */
> -		unit_bytes += 2 * mp->m_sb.sb_logsunit;
> -	} else {
> -		/* BB roundoff */
> -		unit_bytes += 2 * BBSIZE;
> -        }
> +	/* roundoff padding for transaction data and one for commit record */
> +	unit_bytes += log->l_iclog_roundoff;
>  
>  	return unit_bytes;
>  }
>  
> +int
> +xfs_log_calc_unit_res(
> +	struct xfs_mount	*mp,
> +	int			unit_bytes)
> +{
> +	return xlog_calc_unit_res(mp->m_log, unit_bytes);
> +}
> +

Could this be moved to the header as an inline? Otherwise looks
reasonable.

Brian

>  /*
>   * Allocate and initialise a new log ticket.
>   */
> @@ -3513,7 +3505,7 @@ xlog_ticket_alloc(
>  
>  	tic = kmem_cache_zalloc(xfs_log_ticket_zone, GFP_NOFS | __GFP_NOFAIL);
>  
> -	unit_res = xfs_log_calc_unit_res(log->l_mp, unit_bytes);
> +	unit_res = xlog_calc_unit_res(log, unit_bytes);
>  
>  	atomic_set(&tic->t_ref, 1);
>  	tic->t_task		= current;
> diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
> index 1c6fdbf3d506..037950cf1061 100644
> --- a/fs/xfs/xfs_log_priv.h
> +++ b/fs/xfs/xfs_log_priv.h
> @@ -436,6 +436,8 @@ struct xlog {
>  #endif
>  	/* log recovery lsn tracking (for buffer submission */
>  	xfs_lsn_t		l_recovery_lsn;
> +
> +	uint32_t		l_iclog_roundoff;/* padding roundoff */
>  };
>  
>  #define XLOG_BUF_CANCEL_BUCKET(log, blkno) \
> -- 
> 2.28.0
>