Re: [RFC v5 PATCH 2/9] xfs: introduce ->tr_relog transaction

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Feb 27, 2020 at 08:43:14AM -0500, Brian Foster wrote:
> Create a transaction reservation specifically for relog
> transactions. For now it only supports the quotaoff intent, so use
> the associated reservation.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_trans_resv.c | 15 +++++++++++++++
>  fs/xfs/libxfs/xfs_trans_resv.h |  1 +
>  2 files changed, 16 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c
> index 7a9c04920505..1f5c9e6e1afc 100644
> --- a/fs/xfs/libxfs/xfs_trans_resv.c
> +++ b/fs/xfs/libxfs/xfs_trans_resv.c
> @@ -832,6 +832,17 @@ xfs_calc_sb_reservation(
>  	return xfs_calc_buf_res(1, mp->m_sb.sb_sectsize);
>  }
>  
> +/*
> + * Internal relog transaction.
> + *   quotaoff intent
> + */
> +STATIC uint
> +xfs_calc_relog_reservation(
> +	struct xfs_mount	*mp)
> +{
> +	return xfs_calc_qm_quotaoff_reservation(mp);

So when we add the next reloggable intent item, this will turn this
into an n-way max(sizeof(type0), sizeof(type1), ...sizeof(typeN)); ?

> +}
> +
>  void
>  xfs_trans_resv_calc(
>  	struct xfs_mount	*mp,
> @@ -946,4 +957,8 @@ xfs_trans_resv_calc(
>  	resp->tr_clearagi.tr_logres = xfs_calc_clear_agi_bucket_reservation(mp);
>  	resp->tr_growrtzero.tr_logres = xfs_calc_growrtzero_reservation(mp);
>  	resp->tr_growrtfree.tr_logres = xfs_calc_growrtfree_reservation(mp);
> +
> +	resp->tr_relog.tr_logres = xfs_calc_relog_reservation(mp);
> +	resp->tr_relog.tr_logcount = XFS_DEFAULT_PERM_LOG_COUNT;

Relog operations can roll?  I would have figured that you'd simply log
the old item(s) in a new transaction and commit it, along with some
magic to let the log tail move forward.  I guess I'll see what happens
in the next 7 patches. :)

--D

> +	resp->tr_relog.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
>  }
> diff --git a/fs/xfs/libxfs/xfs_trans_resv.h b/fs/xfs/libxfs/xfs_trans_resv.h
> index 7241ab28cf84..b723979cad09 100644
> --- a/fs/xfs/libxfs/xfs_trans_resv.h
> +++ b/fs/xfs/libxfs/xfs_trans_resv.h
> @@ -50,6 +50,7 @@ struct xfs_trans_resv {
>  	struct xfs_trans_res	tr_qm_equotaoff;/* end of turn quota off */
>  	struct xfs_trans_res	tr_sb;		/* modify superblock */
>  	struct xfs_trans_res	tr_fsyncts;	/* update timestamps on fsync */
> +	struct xfs_trans_res	tr_relog;	/* internal relog transaction */
>  };
>  
>  /* shorthand way of accessing reservation structure */
> -- 
> 2.21.1
>